src/crypto/x509/x509.go

   1 // Copyright 2009 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // Package x509 parses X.509-encoded keys and certificates.
   6 package x509
   7
   8 import (
   9         "bytes"
  10         "crypto"
  11         "crypto/dsa"
  12         "crypto/ecdsa"
  13         "crypto/ed25519"
  14         "crypto/elliptic"
  15         "crypto/rsa"
  16         "crypto/sha1"
  17         "crypto/x509/pkix"
  18         "encoding/asn1"
  19         "encoding/pem"
  20         "errors"
  21         "fmt"
  22         "io"
  23         "math/big"
  24         "net"
  25         "net/url"
  26         "strconv"
  27         "strings"
  28         "time"
  29         "unicode"
  30
  31         // Explicitly import these for their crypto.RegisterHash init side-effects.
  32         // Keep these as blank imports, even if they're imported above.
  33         _ "crypto/sha1"
  34         _ "crypto/sha256"
  35         _ "crypto/sha512"
  36
  37         "golang.org/x/crypto/cryptobyte"
  38         cryptobyte_asn1 "golang.org/x/crypto/cryptobyte/asn1"
  39 )
  40
  41 // pkixPublicKey reflects a PKIX public key structure. See SubjectPublicKeyInfo
  42 // in RFC 3280.
  43 type pkixPublicKey struct {
  44         Algo      pkix.AlgorithmIdentifier
  45         BitString asn1.BitString
  46 }
  47
  48 // ParsePKIXPublicKey parses a public key in PKIX, ASN.1 DER form.
  49 // The encoded public key is a SubjectPublicKeyInfo structure
  50 // (see RFC 5280, Section 4.1).
  51 //
  52 // It returns a *rsa.PublicKey, *dsa.PublicKey, *ecdsa.PublicKey, or
  53 // ed25519.PublicKey. More types might be supported in the future.
  54 //
  55 // This kind of key is commonly encoded in PEM blocks of type "PUBLIC KEY".
  56 func ParsePKIXPublicKey(derBytes []byte) (pub interface{}, err error) {
  57         var pki publicKeyInfo
  58         if rest, err := asn1.Unmarshal(derBytes, &pki); err != nil {
  59                 if _, err := asn1.Unmarshal(derBytes, &pkcs1PublicKey{}); err == nil {
  60                         return nil, errors.New("x509: failed to parse public key (use ParsePKCS1PublicKey instead for this key format)")
  61                 }
  62                 return nil, err
  63         } else if len(rest) != 0 {
  64                 return nil, errors.New("x509: trailing data after ASN.1 of public-key")
  65         }
  66         algo := getPublicKeyAlgorithmFromOID(pki.Algorithm.Algorithm)
  67         if algo == UnknownPublicKeyAlgorithm {
  68                 return nil, errors.New("x509: unknown public key algorithm")
  69         }
  70         return parsePublicKey(algo, &pki)
  71 }
  72
  73 func marshalPublicKey(pub interface{}) (publicKeyBytes []byte, publicKeyAlgorithm pkix.AlgorithmIdentifier, err error) {
  74         switch pub := pub.(type) {
  75         case *rsa.PublicKey:
  76                 publicKeyBytes, err = asn1.Marshal(pkcs1PublicKey{
  77                         N: pub.N,
  78                         E: pub.E,
  79                 })
  80                 if err != nil {
  81                         return nil, pkix.AlgorithmIdentifier{}, err
  82                 }
  83                 publicKeyAlgorithm.Algorithm = oidPublicKeyRSA
  84                 // This is a NULL parameters value which is required by
  85                 // RFC 3279, Section 2.3.1.
  86                 publicKeyAlgorithm.Parameters = asn1.NullRawValue
  87         case *ecdsa.PublicKey:
  88                 publicKeyBytes = elliptic.Marshal(pub.Curve, pub.X, pub.Y)
  89                 oid, ok := oidFromNamedCurve(pub.Curve)
  90                 if !ok {
  91                         return nil, pkix.AlgorithmIdentifier{}, errors.New("x509: unsupported elliptic curve")
  92                 }
  93                 publicKeyAlgorithm.Algorithm = oidPublicKeyECDSA
  94                 var paramBytes []byte
  95                 paramBytes, err = asn1.Marshal(oid)
  96                 if err != nil {
  97                         return
  98                 }
  99                 publicKeyAlgorithm.Parameters.FullBytes = paramBytes
 100         case ed25519.PublicKey:
 101                 publicKeyBytes = pub
 102                 publicKeyAlgorithm.Algorithm = oidPublicKeyEd25519
 103         default:
 104                 return nil, pkix.AlgorithmIdentifier{}, fmt.Errorf("x509: unsupported public key type: %T", pub)
 105         }
 106
 107         return publicKeyBytes, publicKeyAlgorithm, nil
 108 }
 109
 110 // MarshalPKIXPublicKey converts a public key to PKIX, ASN.1 DER form.
 111 // The encoded public key is a SubjectPublicKeyInfo structure
 112 // (see RFC 5280, Section 4.1).
 113 //
 114 // The following key types are currently supported: *rsa.PublicKey, *ecdsa.PublicKey
 115 // and ed25519.PublicKey. Unsupported key types result in an error.
 116 //
 117 // This kind of key is commonly encoded in PEM blocks of type "PUBLIC KEY".
 118 func MarshalPKIXPublicKey(pub interface{}) ([]byte, error) {
 119         var publicKeyBytes []byte
 120         var publicKeyAlgorithm pkix.AlgorithmIdentifier
 121         var err error
 122
 123         if publicKeyBytes, publicKeyAlgorithm, err = marshalPublicKey(pub); err != nil {
 124                 return nil, err
 125         }
 126
 127         pkix := pkixPublicKey{
 128                 Algo: publicKeyAlgorithm,
 129                 BitString: asn1.BitString{
 130                         Bytes:     publicKeyBytes,
 131                         BitLength: 8 * len(publicKeyBytes),
 132                 },
 133         }
 134
 135         ret, _ := asn1.Marshal(pkix)
 136         return ret, nil
 137 }
 138
 139 // These structures reflect the ASN.1 structure of X.509 certificates.:
 140
 141 type certificate struct {
 142         Raw                asn1.RawContent
 143         TBSCertificate     tbsCertificate
 144         SignatureAlgorithm pkix.AlgorithmIdentifier
 145         SignatureValue     asn1.BitString
 146 }
 147
 148 type tbsCertificate struct {
 149         Raw                asn1.RawContent
 150         Version            int `asn1:"optional,explicit,default:0,tag:0"`
 151         SerialNumber       *big.Int
 152         SignatureAlgorithm pkix.AlgorithmIdentifier
 153         Issuer             asn1.RawValue
 154         Validity           validity
 155         Subject            asn1.RawValue
 156         PublicKey          publicKeyInfo
 157         UniqueId           asn1.BitString   `asn1:"optional,tag:1"`
 158         SubjectUniqueId    asn1.BitString   `asn1:"optional,tag:2"`
 159         Extensions         []pkix.Extension `asn1:"optional,explicit,tag:3"`
 160 }
 161
 162 type dsaAlgorithmParameters struct {
 163         P, Q, G *big.Int
 164 }
 165
 166 type validity struct {
 167         NotBefore, NotAfter time.Time
 168 }
 169
 170 type publicKeyInfo struct {
 171         Raw       asn1.RawContent
 172         Algorithm pkix.AlgorithmIdentifier
 173         PublicKey asn1.BitString
 174 }
 175
 176 // RFC 5280,  4.2.1.1
 177 type authKeyId struct {
 178         Id []byte `asn1:"optional,tag:0"`
 179 }
 180
 181 type SignatureAlgorithm int
 182
 183 const (
 184         UnknownSignatureAlgorithm SignatureAlgorithm = iota
 185
 186         MD2WithRSA // Unsupported.
 187         MD5WithRSA // Only supported for signing, not verification.
 188         SHA1WithRSA
 189         SHA256WithRSA
 190         SHA384WithRSA
 191         SHA512WithRSA
 192         DSAWithSHA1   // Unsupported.
 193         DSAWithSHA256 // Unsupported.
 194         ECDSAWithSHA1
 195         ECDSAWithSHA256
 196         ECDSAWithSHA384
 197         ECDSAWithSHA512
 198         SHA256WithRSAPSS
 199         SHA384WithRSAPSS
 200         SHA512WithRSAPSS
 201         PureEd25519
 202 )
 203
 204 func (algo SignatureAlgorithm) isRSAPSS() bool {
 205         switch algo {
 206         case SHA256WithRSAPSS, SHA384WithRSAPSS, SHA512WithRSAPSS:
 207                 return true
 208         default:
 209                 return false
 210         }
 211 }
 212
 213 func (algo SignatureAlgorithm) String() string {
 214         for _, details := range signatureAlgorithmDetails {
 215                 if details.algo == algo {
 216                         return details.name
 217                 }
 218         }
 219         return strconv.Itoa(int(algo))
 220 }
 221
 222 type PublicKeyAlgorithm int
 223
 224 const (
 225         UnknownPublicKeyAlgorithm PublicKeyAlgorithm = iota
 226         RSA
 227         DSA // Unsupported.
 228         ECDSA
 229         Ed25519
 230 )
 231
 232 var publicKeyAlgoName = [...]string{
 233         RSA:     "RSA",
 234         DSA:     "DSA",
 235         ECDSA:   "ECDSA",
 236         Ed25519: "Ed25519",
 237 }
 238
 239 func (algo PublicKeyAlgorithm) String() string {
 240         if 0 < algo && int(algo) < len(publicKeyAlgoName) {
 241                 return publicKeyAlgoName[algo]
 242         }
 243         return strconv.Itoa(int(algo))
 244 }
 245
 246 // OIDs for signature algorithms
 247 //
 248 // pkcs-1 OBJECT IDENTIFIER ::= {
 249 //    iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 1 }
 250 //
 251 //
 252 // RFC 3279 2.2.1 RSA Signature Algorithms
 253 //
 254 // md2WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 2 }
 255 //
 256 // md5WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 4 }
 257 //
 258 // sha-1WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 5 }
 259 //
 260 // dsaWithSha1 OBJECT IDENTIFIER ::= {
 261 //    iso(1) member-body(2) us(840) x9-57(10040) x9cm(4) 3 }
 262 //
 263 // RFC 3279 2.2.3 ECDSA Signature Algorithm
 264 //
 265 // ecdsa-with-SHA1 OBJECT IDENTIFIER ::= {
 266 //        iso(1) member-body(2) us(840) ansi-x962(10045)
 267 //    signatures(4) ecdsa-with-SHA1(1)}
 268 //
 269 //
 270 // RFC 4055 5 PKCS #1 Version 1.5
 271 //
 272 // sha256WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 11 }
 273 //
 274 // sha384WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 12 }
 275 //
 276 // sha512WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 13 }
 277 //
 278 //
 279 // RFC 5758 3.1 DSA Signature Algorithms
 280 //
 281 // dsaWithSha256 OBJECT IDENTIFIER ::= {
 282 //    joint-iso-ccitt(2) country(16) us(840) organization(1) gov(101)
 283 //    csor(3) algorithms(4) id-dsa-with-sha2(3) 2}
 284 //
 285 // RFC 5758 3.2 ECDSA Signature Algorithm
 286 //
 287 // ecdsa-with-SHA256 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
 288 //    us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 2 }
 289 //
 290 // ecdsa-with-SHA384 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
 291 //    us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 3 }
 292 //
 293 // ecdsa-with-SHA512 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
 294 //    us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 4 }
 295 //
 296 //
 297 // RFC 8410 3 Curve25519 and Curve448 Algorithm Identifiers
 298 //
 299 // id-Ed25519   OBJECT IDENTIFIER ::= { 1 3 101 112 }
 300
 301 var (
 302         oidSignatureMD2WithRSA      = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 2}
 303         oidSignatureMD5WithRSA      = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 4}
 304         oidSignatureSHA1WithRSA     = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 5}
 305         oidSignatureSHA256WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 11}
 306         oidSignatureSHA384WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 12}
 307         oidSignatureSHA512WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 13}
 308         oidSignatureRSAPSS          = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 10}
 309         oidSignatureDSAWithSHA1     = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 3}
 310         oidSignatureDSAWithSHA256   = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 2}
 311         oidSignatureECDSAWithSHA1   = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 1}
 312         oidSignatureECDSAWithSHA256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 2}
 313         oidSignatureECDSAWithSHA384 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 3}
 314         oidSignatureECDSAWithSHA512 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 4}
 315         oidSignatureEd25519         = asn1.ObjectIdentifier{1, 3, 101, 112}
 316
 317         oidSHA256 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 1}
 318         oidSHA384 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 2}
 319         oidSHA512 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 3}
 320
 321         oidMGF1 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 8}
 322
 323         // oidISOSignatureSHA1WithRSA means the same as oidSignatureSHA1WithRSA
 324         // but it's specified by ISO. Microsoft's makecert.exe has been known
 325         // to produce certificates with this OID.
 326         oidISOSignatureSHA1WithRSA = asn1.ObjectIdentifier{1, 3, 14, 3, 2, 29}
 327 )
 328
 329 var signatureAlgorithmDetails = []struct {
 330         algo       SignatureAlgorithm
 331         name       string
 332         oid        asn1.ObjectIdentifier
 333         pubKeyAlgo PublicKeyAlgorithm
 334         hash       crypto.Hash
 335 }{
 336         {MD2WithRSA, "MD2-RSA", oidSignatureMD2WithRSA, RSA, crypto.Hash(0) /* no value for MD2 */},
 337         {MD5WithRSA, "MD5-RSA", oidSignatureMD5WithRSA, RSA, crypto.MD5},
 338         {SHA1WithRSA, "SHA1-RSA", oidSignatureSHA1WithRSA, RSA, crypto.SHA1},
 339         {SHA1WithRSA, "SHA1-RSA", oidISOSignatureSHA1WithRSA, RSA, crypto.SHA1},
 340         {SHA256WithRSA, "SHA256-RSA", oidSignatureSHA256WithRSA, RSA, crypto.SHA256},
 341         {SHA384WithRSA, "SHA384-RSA", oidSignatureSHA384WithRSA, RSA, crypto.SHA384},
 342         {SHA512WithRSA, "SHA512-RSA", oidSignatureSHA512WithRSA, RSA, crypto.SHA512},
 343         {SHA256WithRSAPSS, "SHA256-RSAPSS", oidSignatureRSAPSS, RSA, crypto.SHA256},
 344         {SHA384WithRSAPSS, "SHA384-RSAPSS", oidSignatureRSAPSS, RSA, crypto.SHA384},
 345         {SHA512WithRSAPSS, "SHA512-RSAPSS", oidSignatureRSAPSS, RSA, crypto.SHA512},
 346         {DSAWithSHA1, "DSA-SHA1", oidSignatureDSAWithSHA1, DSA, crypto.SHA1},
 347         {DSAWithSHA256, "DSA-SHA256", oidSignatureDSAWithSHA256, DSA, crypto.SHA256},
 348         {ECDSAWithSHA1, "ECDSA-SHA1", oidSignatureECDSAWithSHA1, ECDSA, crypto.SHA1},
 349         {ECDSAWithSHA256, "ECDSA-SHA256", oidSignatureECDSAWithSHA256, ECDSA, crypto.SHA256},
 350         {ECDSAWithSHA384, "ECDSA-SHA384", oidSignatureECDSAWithSHA384, ECDSA, crypto.SHA384},
 351         {ECDSAWithSHA512, "ECDSA-SHA512", oidSignatureECDSAWithSHA512, ECDSA, crypto.SHA512},
 352         {PureEd25519, "Ed25519", oidSignatureEd25519, Ed25519, crypto.Hash(0) /* no pre-hashing */},
 353 }
 354
 355 // hashToPSSParameters contains the DER encoded RSA PSS parameters for the
 356 // SHA256, SHA384, and SHA512 hashes as defined in RFC 3447, Appendix A.2.3.
 357 // The parameters contain the following values:
 358 //   * hashAlgorithm contains the associated hash identifier with NULL parameters
 359 //   * maskGenAlgorithm always contains the default mgf1SHA1 identifier
 360 //   * saltLength contains the length of the associated hash
 361 //   * trailerField always contains the default trailerFieldBC value
 362 var hashToPSSParameters = map[crypto.Hash]asn1.RawValue{
 363         crypto.SHA256: asn1.RawValue{FullBytes: []byte{48, 52, 160, 15, 48, 13, 6, 9, 96, 134, 72, 1, 101, 3, 4, 2, 1, 5, 0, 161, 28, 48, 26, 6, 9, 42, 134, 72, 134, 247, 13, 1, 1, 8, 48, 13, 6, 9, 96, 134, 72, 1, 101, 3, 4, 2, 1, 5, 0, 162, 3, 2, 1, 32}},
 364         crypto.SHA384: asn1.RawValue{FullBytes: []byte{48, 52, 160, 15, 48, 13, 6, 9, 96, 134, 72, 1, 101, 3, 4, 2, 2, 5, 0, 161, 28, 48, 26, 6, 9, 42, 134, 72, 134, 247, 13, 1, 1, 8, 48, 13, 6, 9, 96, 134, 72, 1, 101, 3, 4, 2, 2, 5, 0, 162, 3, 2, 1, 48}},
 365         crypto.SHA512: asn1.RawValue{FullBytes: []byte{48, 52, 160, 15, 48, 13, 6, 9, 96, 134, 72, 1, 101, 3, 4, 2, 3, 5, 0, 161, 28, 48, 26, 6, 9, 42, 134, 72, 134, 247, 13, 1, 1, 8, 48, 13, 6, 9, 96, 134, 72, 1, 101, 3, 4, 2, 3, 5, 0, 162, 3, 2, 1, 64}},
 366 }
 367
 368 // pssParameters reflects the parameters in an AlgorithmIdentifier that
 369 // specifies RSA PSS. See RFC 3447, Appendix A.2.3.
 370 type pssParameters struct {
 371         // The following three fields are not marked as
 372         // optional because the default values specify SHA-1,
 373         // which is no longer suitable for use in signatures.
 374         Hash         pkix.AlgorithmIdentifier `asn1:"explicit,tag:0"`
 375         MGF          pkix.AlgorithmIdentifier `asn1:"explicit,tag:1"`
 376         SaltLength   int                      `asn1:"explicit,tag:2"`
 377         TrailerField int                      `asn1:"optional,explicit,tag:3,default:1"`
 378 }
 379
 380 func getSignatureAlgorithmFromAI(ai pkix.AlgorithmIdentifier) SignatureAlgorithm {
 381         if ai.Algorithm.Equal(oidSignatureEd25519) {
 382                 // RFC 8410, Section 3
 383                 // > For all of the OIDs, the parameters MUST be absent.
 384                 if len(ai.Parameters.FullBytes) != 0 {
 385                         return UnknownSignatureAlgorithm
 386                 }
 387         }
 388
 389         if !ai.Algorithm.Equal(oidSignatureRSAPSS) {
 390                 for _, details := range signatureAlgorithmDetails {
 391                         if ai.Algorithm.Equal(details.oid) {
 392                                 return details.algo
 393                         }
 394                 }
 395                 return UnknownSignatureAlgorithm
 396         }
 397
 398         // RSA PSS is special because it encodes important parameters
 399         // in the Parameters.
 400
 401         var params pssParameters
 402         if _, err := asn1.Unmarshal(ai.Parameters.FullBytes, &params); err != nil {
 403                 return UnknownSignatureAlgorithm
 404         }
 405
 406         var mgf1HashFunc pkix.AlgorithmIdentifier
 407         if _, err := asn1.Unmarshal(params.MGF.Parameters.FullBytes, &mgf1HashFunc); err != nil {
 408                 return UnknownSignatureAlgorithm
 409         }
 410
 411         // PSS is greatly overburdened with options. This code forces them into
 412         // three buckets by requiring that the MGF1 hash function always match the
 413         // message hash function (as recommended in RFC 3447, Section 8.1), that the
 414         // salt length matches the hash length, and that the trailer field has the
 415         // default value.
 416         if (len(params.Hash.Parameters.FullBytes) != 0 && !bytes.Equal(params.Hash.Parameters.FullBytes, asn1.NullBytes)) ||
 417                 !params.MGF.Algorithm.Equal(oidMGF1) ||
 418                 !mgf1HashFunc.Algorithm.Equal(params.Hash.Algorithm) ||
 419                 (len(mgf1HashFunc.Parameters.FullBytes) != 0 && !bytes.Equal(mgf1HashFunc.Parameters.FullBytes, asn1.NullBytes)) ||
 420                 params.TrailerField != 1 {
 421                 return UnknownSignatureAlgorithm
 422         }
 423
 424         switch {
 425         case params.Hash.Algorithm.Equal(oidSHA256) && params.SaltLength == 32:
 426                 return SHA256WithRSAPSS
 427         case params.Hash.Algorithm.Equal(oidSHA384) && params.SaltLength == 48:
 428                 return SHA384WithRSAPSS
 429         case params.Hash.Algorithm.Equal(oidSHA512) && params.SaltLength == 64:
 430                 return SHA512WithRSAPSS
 431         }
 432
 433         return UnknownSignatureAlgorithm
 434 }
 435
 436 // RFC 3279, 2.3 Public Key Algorithms
 437 //
 438 // pkcs-1 OBJECT IDENTIFIER ::== { iso(1) member-body(2) us(840)
 439 //    rsadsi(113549) pkcs(1) 1 }
 440 //
 441 // rsaEncryption OBJECT IDENTIFIER ::== { pkcs1-1 1 }
 442 //
 443 // id-dsa OBJECT IDENTIFIER ::== { iso(1) member-body(2) us(840)
 444 //    x9-57(10040) x9cm(4) 1 }
 445 //
 446 // RFC 5480, 2.1.1 Unrestricted Algorithm Identifier and Parameters
 447 //
 448 // id-ecPublicKey OBJECT IDENTIFIER ::= {
 449 //       iso(1) member-body(2) us(840) ansi-X9-62(10045) keyType(2) 1 }
 450 var (
 451         oidPublicKeyRSA     = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}
 452         oidPublicKeyDSA     = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 1}
 453         oidPublicKeyECDSA   = asn1.ObjectIdentifier{1, 2, 840, 10045, 2, 1}
 454         oidPublicKeyEd25519 = oidSignatureEd25519
 455 )
 456
 457 func getPublicKeyAlgorithmFromOID(oid asn1.ObjectIdentifier) PublicKeyAlgorithm {
 458         switch {
 459         case oid.Equal(oidPublicKeyRSA):
 460                 return RSA
 461         case oid.Equal(oidPublicKeyDSA):
 462                 return DSA
 463         case oid.Equal(oidPublicKeyECDSA):
 464                 return ECDSA
 465         case oid.Equal(oidPublicKeyEd25519):
 466                 return Ed25519
 467         }
 468         return UnknownPublicKeyAlgorithm
 469 }
 470
 471 // RFC 5480, 2.1.1.1. Named Curve
 472 //
 473 // secp224r1 OBJECT IDENTIFIER ::= {
 474 //   iso(1) identified-organization(3) certicom(132) curve(0) 33 }
 475 //
 476 // secp256r1 OBJECT IDENTIFIER ::= {
 477 //   iso(1) member-body(2) us(840) ansi-X9-62(10045) curves(3)
 478 //   prime(1) 7 }
 479 //
 480 // secp384r1 OBJECT IDENTIFIER ::= {
 481 //   iso(1) identified-organization(3) certicom(132) curve(0) 34 }
 482 //
 483 // secp521r1 OBJECT IDENTIFIER ::= {
 484 //   iso(1) identified-organization(3) certicom(132) curve(0) 35 }
 485 //
 486 // NB: secp256r1 is equivalent to prime256v1
 487 var (
 488         oidNamedCurveP224 = asn1.ObjectIdentifier{1, 3, 132, 0, 33}
 489         oidNamedCurveP256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 3, 1, 7}
 490         oidNamedCurveP384 = asn1.ObjectIdentifier{1, 3, 132, 0, 34}
 491         oidNamedCurveP521 = asn1.ObjectIdentifier{1, 3, 132, 0, 35}
 492 )
 493
 494 func namedCurveFromOID(oid asn1.ObjectIdentifier) elliptic.Curve {
 495         switch {
 496         case oid.Equal(oidNamedCurveP224):
 497                 return elliptic.P224()
 498         case oid.Equal(oidNamedCurveP256):
 499                 return elliptic.P256()
 500         case oid.Equal(oidNamedCurveP384):
 501                 return elliptic.P384()
 502         case oid.Equal(oidNamedCurveP521):
 503                 return elliptic.P521()
 504         }
 505         return nil
 506 }
 507
 508 func oidFromNamedCurve(curve elliptic.Curve) (asn1.ObjectIdentifier, bool) {
 509         switch curve {
 510         case elliptic.P224():
 511                 return oidNamedCurveP224, true
 512         case elliptic.P256():
 513                 return oidNamedCurveP256, true
 514         case elliptic.P384():
 515                 return oidNamedCurveP384, true
 516         case elliptic.P521():
 517                 return oidNamedCurveP521, true
 518         }
 519
 520         return nil, false
 521 }
 522
 523 // KeyUsage represents the set of actions that are valid for a given key. It's
 524 // a bitmap of the KeyUsage* constants.
 525 type KeyUsage int
 526
 527 const (
 528         KeyUsageDigitalSignature KeyUsage = 1 << iota
 529         KeyUsageContentCommitment
 530         KeyUsageKeyEncipherment
 531         KeyUsageDataEncipherment
 532         KeyUsageKeyAgreement
 533         KeyUsageCertSign
 534         KeyUsageCRLSign
 535         KeyUsageEncipherOnly
 536         KeyUsageDecipherOnly
 537 )
 538
 539 // RFC 5280, 4.2.1.12  Extended Key Usage
 540 //
 541 // anyExtendedKeyUsage OBJECT IDENTIFIER ::= { id-ce-extKeyUsage 0 }
 542 //
 543 // id-kp OBJECT IDENTIFIER ::= { id-pkix 3 }
 544 //
 545 // id-kp-serverAuth             OBJECT IDENTIFIER ::= { id-kp 1 }
 546 // id-kp-clientAuth             OBJECT IDENTIFIER ::= { id-kp 2 }
 547 // id-kp-codeSigning            OBJECT IDENTIFIER ::= { id-kp 3 }
 548 // id-kp-emailProtection        OBJECT IDENTIFIER ::= { id-kp 4 }
 549 // id-kp-timeStamping           OBJECT IDENTIFIER ::= { id-kp 8 }
 550 // id-kp-OCSPSigning            OBJECT IDENTIFIER ::= { id-kp 9 }
 551 var (
 552         oidExtKeyUsageAny                            = asn1.ObjectIdentifier{2, 5, 29, 37, 0}
 553         oidExtKeyUsageServerAuth                     = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 1}
 554         oidExtKeyUsageClientAuth                     = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 2}
 555         oidExtKeyUsageCodeSigning                    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 3}
 556         oidExtKeyUsageEmailProtection                = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 4}
 557         oidExtKeyUsageIPSECEndSystem                 = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 5}
 558         oidExtKeyUsageIPSECTunnel                    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 6}
 559         oidExtKeyUsageIPSECUser                      = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 7}
 560         oidExtKeyUsageTimeStamping                   = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 8}
 561         oidExtKeyUsageOCSPSigning                    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 9}
 562         oidExtKeyUsageMicrosoftServerGatedCrypto     = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 10, 3, 3}
 563         oidExtKeyUsageNetscapeServerGatedCrypto      = asn1.ObjectIdentifier{2, 16, 840, 1, 113730, 4, 1}
 564         oidExtKeyUsageMicrosoftCommercialCodeSigning = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 2, 1, 22}
 565         oidExtKeyUsageMicrosoftKernelCodeSigning     = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 61, 1, 1}
 566 )
 567
 568 // ExtKeyUsage represents an extended set of actions that are valid for a given key.
 569 // Each of the ExtKeyUsage* constants define a unique action.
 570 type ExtKeyUsage int
 571
 572 const (
 573         ExtKeyUsageAny ExtKeyUsage = iota
 574         ExtKeyUsageServerAuth
 575         ExtKeyUsageClientAuth
 576         ExtKeyUsageCodeSigning
 577         ExtKeyUsageEmailProtection
 578         ExtKeyUsageIPSECEndSystem
 579         ExtKeyUsageIPSECTunnel
 580         ExtKeyUsageIPSECUser
 581         ExtKeyUsageTimeStamping
 582         ExtKeyUsageOCSPSigning
 583         ExtKeyUsageMicrosoftServerGatedCrypto
 584         ExtKeyUsageNetscapeServerGatedCrypto
 585         ExtKeyUsageMicrosoftCommercialCodeSigning
 586         ExtKeyUsageMicrosoftKernelCodeSigning
 587 )
 588
 589 // extKeyUsageOIDs contains the mapping between an ExtKeyUsage and its OID.
 590 var extKeyUsageOIDs = []struct {
 591         extKeyUsage ExtKeyUsage
 592         oid         asn1.ObjectIdentifier
 593 }{
 594         {ExtKeyUsageAny, oidExtKeyUsageAny},
 595         {ExtKeyUsageServerAuth, oidExtKeyUsageServerAuth},
 596         {ExtKeyUsageClientAuth, oidExtKeyUsageClientAuth},
 597         {ExtKeyUsageCodeSigning, oidExtKeyUsageCodeSigning},
 598         {ExtKeyUsageEmailProtection, oidExtKeyUsageEmailProtection},
 599         {ExtKeyUsageIPSECEndSystem, oidExtKeyUsageIPSECEndSystem},
 600         {ExtKeyUsageIPSECTunnel, oidExtKeyUsageIPSECTunnel},
 601         {ExtKeyUsageIPSECUser, oidExtKeyUsageIPSECUser},
 602         {ExtKeyUsageTimeStamping, oidExtKeyUsageTimeStamping},
 603         {ExtKeyUsageOCSPSigning, oidExtKeyUsageOCSPSigning},
 604         {ExtKeyUsageMicrosoftServerGatedCrypto, oidExtKeyUsageMicrosoftServerGatedCrypto},
 605         {ExtKeyUsageNetscapeServerGatedCrypto, oidExtKeyUsageNetscapeServerGatedCrypto},
 606         {ExtKeyUsageMicrosoftCommercialCodeSigning, oidExtKeyUsageMicrosoftCommercialCodeSigning},
 607         {ExtKeyUsageMicrosoftKernelCodeSigning, oidExtKeyUsageMicrosoftKernelCodeSigning},
 608 }
 609
 610 func extKeyUsageFromOID(oid asn1.ObjectIdentifier) (eku ExtKeyUsage, ok bool) {
 611         for _, pair := range extKeyUsageOIDs {
 612                 if oid.Equal(pair.oid) {
 613                         return pair.extKeyUsage, true
 614                 }
 615         }
 616         return
 617 }
 618
 619 func oidFromExtKeyUsage(eku ExtKeyUsage) (oid asn1.ObjectIdentifier, ok bool) {
 620         for _, pair := range extKeyUsageOIDs {
 621                 if eku == pair.extKeyUsage {
 622                         return pair.oid, true
 623                 }
 624         }
 625         return
 626 }
 627
 628 // A Certificate represents an X.509 certificate.
 629 type Certificate struct {
 630         Raw                     []byte // Complete ASN.1 DER content (certificate, signature algorithm and signature).
 631         RawTBSCertificate       []byte // Certificate part of raw ASN.1 DER content.
 632         RawSubjectPublicKeyInfo []byte // DER encoded SubjectPublicKeyInfo.
 633         RawSubject              []byte // DER encoded Subject
 634         RawIssuer               []byte // DER encoded Issuer
 635
 636         Signature          []byte
 637         SignatureAlgorithm SignatureAlgorithm
 638
 639         PublicKeyAlgorithm PublicKeyAlgorithm
 640         PublicKey          interface{}
 641
 642         Version             int
 643         SerialNumber        *big.Int
 644         Issuer              pkix.Name
 645         Subject             pkix.Name
 646         NotBefore, NotAfter time.Time // Validity bounds.
 647         KeyUsage            KeyUsage
 648
 649         // Extensions contains raw X.509 extensions. When parsing certificates,
 650         // this can be used to extract non-critical extensions that are not
 651         // parsed by this package. When marshaling certificates, the Extensions
 652         // field is ignored, see ExtraExtensions.
 653         Extensions []pkix.Extension
 654
 655         // ExtraExtensions contains extensions to be copied, raw, into any
 656         // marshaled certificates. Values override any extensions that would
 657         // otherwise be produced based on the other fields. The ExtraExtensions
 658         // field is not populated when parsing certificates, see Extensions.
 659         ExtraExtensions []pkix.Extension
 660
 661         // UnhandledCriticalExtensions contains a list of extension IDs that
 662         // were not (fully) processed when parsing. Verify will fail if this
 663         // slice is non-empty, unless verification is delegated to an OS
 664         // library which understands all the critical extensions.
 665         //
 666         // Users can access these extensions using Extensions and can remove
 667         // elements from this slice if they believe that they have been
 668         // handled.
 669         UnhandledCriticalExtensions []asn1.ObjectIdentifier
 670
 671         ExtKeyUsage        []ExtKeyUsage           // Sequence of extended key usages.
 672         UnknownExtKeyUsage []asn1.ObjectIdentifier // Encountered extended key usages unknown to this package.
 673
 674         // BasicConstraintsValid indicates whether IsCA, MaxPathLen,
 675         // and MaxPathLenZero are valid.
 676         BasicConstraintsValid bool
 677         IsCA                  bool
 678
 679         // MaxPathLen and MaxPathLenZero indicate the presence and
 680         // value of the BasicConstraints' "pathLenConstraint".
 681         //
 682         // When parsing a certificate, a positive non-zero MaxPathLen
 683         // means that the field was specified, -1 means it was unset,
 684         // and MaxPathLenZero being true mean that the field was
 685         // explicitly set to zero. The case of MaxPathLen==0 with MaxPathLenZero==false
 686         // should be treated equivalent to -1 (unset).
 687         //
 688         // When generating a certificate, an unset pathLenConstraint
 689         // can be requested with either MaxPathLen == -1 or using the
 690         // zero value for both MaxPathLen and MaxPathLenZero.
 691         MaxPathLen int
 692         // MaxPathLenZero indicates that BasicConstraintsValid==true
 693         // and MaxPathLen==0 should be interpreted as an actual
 694         // maximum path length of zero. Otherwise, that combination is
 695         // interpreted as MaxPathLen not being set.
 696         MaxPathLenZero bool
 697
 698         SubjectKeyId   []byte
 699         AuthorityKeyId []byte
 700
 701         // RFC 5280, 4.2.2.1 (Authority Information Access)
 702         OCSPServer            []string
 703         IssuingCertificateURL []string
 704
 705         // Subject Alternate Name values. (Note that these values may not be valid
 706         // if invalid values were contained within a parsed certificate. For
 707         // example, an element of DNSNames may not be a valid DNS domain name.)
 708         DNSNames       []string
 709         EmailAddresses []string
 710         IPAddresses    []net.IP
 711         URIs           []*url.URL
 712
 713         // Name constraints
 714         PermittedDNSDomainsCritical bool // if true then the name constraints are marked critical.
 715         PermittedDNSDomains         []string
 716         ExcludedDNSDomains          []string
 717         PermittedIPRanges           []*net.IPNet
 718         ExcludedIPRanges            []*net.IPNet
 719         PermittedEmailAddresses     []string
 720         ExcludedEmailAddresses      []string
 721         PermittedURIDomains         []string
 722         ExcludedURIDomains          []string
 723
 724         // CRL Distribution Points
 725         CRLDistributionPoints []string
 726
 727         PolicyIdentifiers []asn1.ObjectIdentifier
 728 }
 729
 730 // ErrUnsupportedAlgorithm results from attempting to perform an operation that
 731 // involves algorithms that are not currently implemented.
 732 var ErrUnsupportedAlgorithm = errors.New("x509: cannot verify signature: algorithm unimplemented")
 733
 734 // An InsecureAlgorithmError
 735 type InsecureAlgorithmError SignatureAlgorithm
 736
 737 func (e InsecureAlgorithmError) Error() string {
 738         return fmt.Sprintf("x509: cannot verify signature: insecure algorithm %v", SignatureAlgorithm(e))
 739 }
 740
 741 // ConstraintViolationError results when a requested usage is not permitted by
 742 // a certificate. For example: checking a signature when the public key isn't a
 743 // certificate signing key.
 744 type ConstraintViolationError struct{}
 745
 746 func (ConstraintViolationError) Error() string {
 747         return "x509: invalid signature: parent certificate cannot sign this kind of certificate"
 748 }
 749
 750 func (c *Certificate) Equal(other *Certificate) bool {
 751         if c == nil || other == nil {
 752                 return c == other
 753         }
 754         return bytes.Equal(c.Raw, other.Raw)
 755 }
 756
 757 func (c *Certificate) hasSANExtension() bool {
 758         return oidInExtensions(oidExtensionSubjectAltName, c.Extensions)
 759 }
 760
 761 // CheckSignatureFrom verifies that the signature on c is a valid signature
 762 // from parent.
 763 func (c *Certificate) CheckSignatureFrom(parent *Certificate) error {
 764         // RFC 5280, 4.2.1.9:
 765         // "If the basic constraints extension is not present in a version 3
 766         // certificate, or the extension is present but the cA boolean is not
 767         // asserted, then the certified public key MUST NOT be used to verify
 768         // certificate signatures."
 769         if parent.Version == 3 && !parent.BasicConstraintsValid ||
 770                 parent.BasicConstraintsValid && !parent.IsCA {
 771                 return ConstraintViolationError{}
 772         }
 773
 774         if parent.KeyUsage != 0 && parent.KeyUsage&KeyUsageCertSign == 0 {
 775                 return ConstraintViolationError{}
 776         }
 777
 778         if parent.PublicKeyAlgorithm == UnknownPublicKeyAlgorithm {
 779                 return ErrUnsupportedAlgorithm
 780         }
 781
 782         // TODO(agl): don't ignore the path length constraint.
 783
 784         return parent.CheckSignature(c.SignatureAlgorithm, c.RawTBSCertificate, c.Signature)
 785 }
 786
 787 // CheckSignature verifies that signature is a valid signature over signed from
 788 // c's public key.
 789 func (c *Certificate) CheckSignature(algo SignatureAlgorithm, signed, signature []byte) error {
 790         return checkSignature(algo, signed, signature, c.PublicKey)
 791 }
 792
 793 func (c *Certificate) hasNameConstraints() bool {
 794         return oidInExtensions(oidExtensionNameConstraints, c.Extensions)
 795 }
 796
 797 func (c *Certificate) getSANExtension() []byte {
 798         for _, e := range c.Extensions {
 799                 if e.Id.Equal(oidExtensionSubjectAltName) {
 800                         return e.Value
 801                 }
 802         }
 803         return nil
 804 }
 805
 806 func signaturePublicKeyAlgoMismatchError(expectedPubKeyAlgo PublicKeyAlgorithm, pubKey interface{}) error {
 807         return fmt.Errorf("x509: signature algorithm specifies an %s public key, but have public key of type %T", expectedPubKeyAlgo.String(), pubKey)
 808 }
 809
 810 // CheckSignature verifies that signature is a valid signature over signed from
 811 // a crypto.PublicKey.
 812 func checkSignature(algo SignatureAlgorithm, signed, signature []byte, publicKey crypto.PublicKey) (err error) {
 813         var hashType crypto.Hash
 814         var pubKeyAlgo PublicKeyAlgorithm
 815
 816         for _, details := range signatureAlgorithmDetails {
 817                 if details.algo == algo {
 818                         hashType = details.hash
 819                         pubKeyAlgo = details.pubKeyAlgo
 820                 }
 821         }
 822
 823         switch hashType {
 824         case crypto.Hash(0):
 825                 if pubKeyAlgo != Ed25519 {
 826                         return ErrUnsupportedAlgorithm
 827                 }
 828         case crypto.MD5:
 829                 return InsecureAlgorithmError(algo)
 830         default:
 831                 if !hashType.Available() {
 832                         return ErrUnsupportedAlgorithm
 833                 }
 834                 h := hashType.New()
 835                 h.Write(signed)
 836                 signed = h.Sum(nil)
 837         }
 838
 839         switch pub := publicKey.(type) {
 840         case *rsa.PublicKey:
 841                 if pubKeyAlgo != RSA {
 842                         return signaturePublicKeyAlgoMismatchError(pubKeyAlgo, pub)
 843                 }
 844                 if algo.isRSAPSS() {
 845                         return rsa.VerifyPSS(pub, hashType, signed, signature, &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash})
 846                 } else {
 847                         return rsa.VerifyPKCS1v15(pub, hashType, signed, signature)
 848                 }
 849         case *ecdsa.PublicKey:
 850                 if pubKeyAlgo != ECDSA {
 851                         return signaturePublicKeyAlgoMismatchError(pubKeyAlgo, pub)
 852                 }
 853                 if !ecdsa.VerifyASN1(pub, signed, signature) {
 854                         return errors.New("x509: ECDSA verification failure")
 855                 }
 856                 return
 857         case ed25519.PublicKey:
 858                 if pubKeyAlgo != Ed25519 {
 859                         return signaturePublicKeyAlgoMismatchError(pubKeyAlgo, pub)
 860                 }
 861                 if !ed25519.Verify(pub, signed, signature) {
 862                         return errors.New("x509: Ed25519 verification failure")
 863                 }
 864                 return
 865         }
 866         return ErrUnsupportedAlgorithm
 867 }
 868
 869 // CheckCRLSignature checks that the signature in crl is from c.
 870 func (c *Certificate) CheckCRLSignature(crl *pkix.CertificateList) error {
 871         algo := getSignatureAlgorithmFromAI(crl.SignatureAlgorithm)
 872         return c.CheckSignature(algo, crl.TBSCertList.Raw, crl.SignatureValue.RightAlign())
 873 }
 874
 875 type UnhandledCriticalExtension struct{}
 876
 877 func (h UnhandledCriticalExtension) Error() string {
 878         return "x509: unhandled critical extension"
 879 }
 880
 881 type basicConstraints struct {
 882         IsCA       bool `asn1:"optional"`
 883         MaxPathLen int  `asn1:"optional,default:-1"`
 884 }
 885
 886 // RFC 5280 4.2.1.4
 887 type policyInformation struct {
 888         Policy asn1.ObjectIdentifier
 889         // policyQualifiers omitted
 890 }
 891
 892 const (
 893         nameTypeEmail = 1
 894         nameTypeDNS   = 2
 895         nameTypeURI   = 6
 896         nameTypeIP    = 7
 897 )
 898
 899 // RFC 5280, 4.2.2.1
 900 type authorityInfoAccess struct {
 901         Method   asn1.ObjectIdentifier
 902         Location asn1.RawValue
 903 }
 904
 905 // RFC 5280, 4.2.1.14
 906 type distributionPoint struct {
 907         DistributionPoint distributionPointName `asn1:"optional,tag:0"`
 908         Reason            asn1.BitString        `asn1:"optional,tag:1"`
 909         CRLIssuer         asn1.RawValue         `asn1:"optional,tag:2"`
 910 }
 911
 912 type distributionPointName struct {
 913         FullName     []asn1.RawValue  `asn1:"optional,tag:0"`
 914         RelativeName pkix.RDNSequence `asn1:"optional,tag:1"`
 915 }
 916
 917 func parsePublicKey(algo PublicKeyAlgorithm, keyData *publicKeyInfo) (interface{}, error) {
 918         asn1Data := keyData.PublicKey.RightAlign()
 919         switch algo {
 920         case RSA:
 921                 // RSA public keys must have a NULL in the parameters.
 922                 // See RFC 3279, Section 2.3.1.
 923                 if !bytes.Equal(keyData.Algorithm.Parameters.FullBytes, asn1.NullBytes) {
 924                         return nil, errors.New("x509: RSA key missing NULL parameters")
 925                 }
 926
 927                 p := new(pkcs1PublicKey)
 928                 rest, err := asn1.Unmarshal(asn1Data, p)
 929                 if err != nil {
 930                         return nil, err
 931                 }
 932                 if len(rest) != 0 {
 933                         return nil, errors.New("x509: trailing data after RSA public key")
 934                 }
 935
 936                 if p.N.Sign() <= 0 {
 937                         return nil, errors.New("x509: RSA modulus is not a positive number")
 938                 }
 939                 if p.E <= 0 {
 940                         return nil, errors.New("x509: RSA public exponent is not a positive number")
 941                 }
 942
 943                 pub := &rsa.PublicKey{
 944                         E: p.E,
 945                         N: p.N,
 946                 }
 947                 return pub, nil
 948         case DSA:
 949                 var p *big.Int
 950                 rest, err := asn1.Unmarshal(asn1Data, &p)
 951                 if err != nil {
 952                         return nil, err
 953                 }
 954                 if len(rest) != 0 {
 955                         return nil, errors.New("x509: trailing data after DSA public key")
 956                 }
 957                 paramsData := keyData.Algorithm.Parameters.FullBytes
 958                 params := new(dsaAlgorithmParameters)
 959                 rest, err = asn1.Unmarshal(paramsData, params)
 960                 if err != nil {
 961                         return nil, err
 962                 }
 963                 if len(rest) != 0 {
 964                         return nil, errors.New("x509: trailing data after DSA parameters")
 965                 }
 966                 if p.Sign() <= 0 || params.P.Sign() <= 0 || params.Q.Sign() <= 0 || params.G.Sign() <= 0 {
 967                         return nil, errors.New("x509: zero or negative DSA parameter")
 968                 }
 969                 pub := &dsa.PublicKey{
 970                         Parameters: dsa.Parameters{
 971                                 P: params.P,
 972                                 Q: params.Q,
 973                                 G: params.G,
 974                         },
 975                         Y: p,
 976                 }
 977                 return pub, nil
 978         case ECDSA:
 979                 paramsData := keyData.Algorithm.Parameters.FullBytes
 980                 namedCurveOID := new(asn1.ObjectIdentifier)
 981                 rest, err := asn1.Unmarshal(paramsData, namedCurveOID)
 982                 if err != nil {
 983                         return nil, errors.New("x509: failed to parse ECDSA parameters as named curve")
 984                 }
 985                 if len(rest) != 0 {
 986                         return nil, errors.New("x509: trailing data after ECDSA parameters")
 987                 }
 988                 namedCurve := namedCurveFromOID(*namedCurveOID)
 989                 if namedCurve == nil {
 990                         return nil, errors.New("x509: unsupported elliptic curve")
 991                 }
 992                 x, y := elliptic.Unmarshal(namedCurve, asn1Data)
 993                 if x == nil {
 994                         return nil, errors.New("x509: failed to unmarshal elliptic curve point")
 995                 }
 996                 pub := &ecdsa.PublicKey{
 997                         Curve: namedCurve,
 998                         X:     x,
 999                         Y:     y,
1000                 }
1001                 return pub, nil
1002         case Ed25519:
1003                 // RFC 8410, Section 3
1004                 // > For all of the OIDs, the parameters MUST be absent.
1005                 if len(keyData.Algorithm.Parameters.FullBytes) != 0 {
1006                         return nil, errors.New("x509: Ed25519 key encoded with illegal parameters")
1007                 }
1008                 if len(asn1Data) != ed25519.PublicKeySize {
1009                         return nil, errors.New("x509: wrong Ed25519 public key size")
1010                 }
1011                 pub := make([]byte, ed25519.PublicKeySize)
1012                 copy(pub, asn1Data)
1013                 return ed25519.PublicKey(pub), nil
1014         default:
1015                 return nil, nil
1016         }
1017 }
1018
1019 func forEachSAN(extension []byte, callback func(tag int, data []byte) error) error {
1020         // RFC 5280, 4.2.1.6
1021
1022         // SubjectAltName ::= GeneralNames
1023         //
1024         // GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName
1025         //
1026         // GeneralName ::= CHOICE {
1027         //      otherName                       [0]     OtherName,
1028         //      rfc822Name                      [1]     IA5String,
1029         //      dNSName                         [2]     IA5String,
1030         //      x400Address                     [3]     ORAddress,
1031         //      directoryName                   [4]     Name,
1032         //      ediPartyName                    [5]     EDIPartyName,
1033         //      uniformResourceIdentifier       [6]     IA5String,
1034         //      iPAddress                       [7]     OCTET STRING,
1035         //      registeredID                    [8]     OBJECT IDENTIFIER }
1036         var seq asn1.RawValue
1037         rest, err := asn1.Unmarshal(extension, &seq)
1038         if err != nil {
1039                 return err
1040         } else if len(rest) != 0 {
1041                 return errors.New("x509: trailing data after X.509 extension")
1042         }
1043         if !seq.IsCompound || seq.Tag != 16 || seq.Class != 0 {
1044                 return asn1.StructuralError{Msg: "bad SAN sequence"}
1045         }
1046
1047         rest = seq.Bytes
1048         for len(rest) > 0 {
1049                 var v asn1.RawValue
1050                 rest, err = asn1.Unmarshal(rest, &v)
1051                 if err != nil {
1052                         return err
1053                 }
1054
1055                 if err := callback(v.Tag, v.Bytes); err != nil {
1056                         return err
1057                 }
1058         }
1059
1060         return nil
1061 }
1062
1063 func parseSANExtension(value []byte) (dnsNames, emailAddresses []string, ipAddresses []net.IP, uris []*url.URL, err error) {
1064         err = forEachSAN(value, func(tag int, data []byte) error {
1065                 switch tag {
1066                 case nameTypeEmail:
1067                         email := string(data)
1068                         if err := isIA5String(email); err != nil {
1069                                 return errors.New("x509: SAN rfc822Name is malformed")
1070                         }
1071                         emailAddresses = append(emailAddresses, email)
1072                 case nameTypeDNS:
1073                         name := string(data)
1074                         if err := isIA5String(name); err != nil {
1075                                 return errors.New("x509: SAN dNSName is malformed")
1076                         }
1077                         dnsNames = append(dnsNames, string(name))
1078                 case nameTypeURI:
1079                         uriStr := string(data)
1080                         if err := isIA5String(uriStr); err != nil {
1081                                 return errors.New("x509: SAN uniformResourceIdentifier is malformed")
1082                         }
1083                         uri, err := url.Parse(uriStr)
1084                         if err != nil {
1085                                 return fmt.Errorf("x509: cannot parse URI %q: %s", uriStr, err)
1086                         }
1087                         if len(uri.Host) > 0 {
1088                                 if _, ok := domainToReverseLabels(uri.Host); !ok {
1089                                         return fmt.Errorf("x509: cannot parse URI %q: invalid domain", uriStr)
1090                                 }
1091                         }
1092                         uris = append(uris, uri)
1093                 case nameTypeIP:
1094                         switch len(data) {
1095                         case net.IPv4len, net.IPv6len:
1096                                 ipAddresses = append(ipAddresses, data)
1097                         default:
1098                                 return errors.New("x509: cannot parse IP address of length " + strconv.Itoa(len(data)))
1099                         }
1100                 }
1101
1102                 return nil
1103         })
1104
1105         return
1106 }
1107
1108 // isValidIPMask reports whether mask consists of zero or more 1 bits, followed by zero bits.
1109 func isValidIPMask(mask []byte) bool {
1110         seenZero := false
1111
1112         for _, b := range mask {
1113                 if seenZero {
1114                         if b != 0 {
1115                                 return false
1116                         }
1117
1118                         continue
1119                 }
1120
1121                 switch b {
1122                 case 0x00, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe:
1123                         seenZero = true
1124                 case 0xff:
1125                 default:
1126                         return false
1127                 }
1128         }
1129
1130         return true
1131 }
1132
1133 func parseNameConstraintsExtension(out *Certificate, e pkix.Extension) (unhandled bool, err error) {
1134         // RFC 5280, 4.2.1.10
1135
1136         // NameConstraints ::= SEQUENCE {
1137         //      permittedSubtrees       [0]     GeneralSubtrees OPTIONAL,
1138         //      excludedSubtrees        [1]     GeneralSubtrees OPTIONAL }
1139         //
1140         // GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
1141         //
1142         // GeneralSubtree ::= SEQUENCE {
1143         //      base                    GeneralName,
1144         //      minimum         [0]     BaseDistance DEFAULT 0,
1145         //      maximum         [1]     BaseDistance OPTIONAL }
1146         //
1147         // BaseDistance ::= INTEGER (0..MAX)
1148
1149         outer := cryptobyte.String(e.Value)
1150         var toplevel, permitted, excluded cryptobyte.String
1151         var havePermitted, haveExcluded bool
1152         if !outer.ReadASN1(&toplevel, cryptobyte_asn1.SEQUENCE) ||
1153                 !outer.Empty() ||
1154                 !toplevel.ReadOptionalASN1(&permitted, &havePermitted, cryptobyte_asn1.Tag(0).ContextSpecific().Constructed()) ||
1155                 !toplevel.ReadOptionalASN1(&excluded, &haveExcluded, cryptobyte_asn1.Tag(1).ContextSpecific().Constructed()) ||
1156                 !toplevel.Empty() {
1157                 return false, errors.New("x509: invalid NameConstraints extension")
1158         }
1159
1160         if !havePermitted && !haveExcluded || len(permitted) == 0 && len(excluded) == 0 {
1161                 // From RFC 5280, Section 4.2.1.10:
1162                 //   “either the permittedSubtrees field
1163                 //   or the excludedSubtrees MUST be
1164                 //   present”
1165                 return false, errors.New("x509: empty name constraints extension")
1166         }
1167
1168         getValues := func(subtrees cryptobyte.String) (dnsNames []string, ips []*net.IPNet, emails, uriDomains []string, err error) {
1169                 for !subtrees.Empty() {
1170                         var seq, value cryptobyte.String
1171                         var tag cryptobyte_asn1.Tag
1172                         if !subtrees.ReadASN1(&seq, cryptobyte_asn1.SEQUENCE) ||
1173                                 !seq.ReadAnyASN1(&value, &tag) {
1174                                 return nil, nil, nil, nil, fmt.Errorf("x509: invalid NameConstraints extension")
1175                         }
1176
1177                         var (
1178                                 dnsTag   = cryptobyte_asn1.Tag(2).ContextSpecific()
1179                                 emailTag = cryptobyte_asn1.Tag(1).ContextSpecific()
1180                                 ipTag    = cryptobyte_asn1.Tag(7).ContextSpecific()
1181                                 uriTag   = cryptobyte_asn1.Tag(6).ContextSpecific()
1182                         )
1183
1184                         switch tag {
1185                         case dnsTag:
1186                                 domain := string(value)
1187                                 if err := isIA5String(domain); err != nil {
1188                                         return nil, nil, nil, nil, errors.New("x509: invalid constraint value: " + err.Error())
1189                                 }
1190
1191                                 trimmedDomain := domain
1192                                 if len(trimmedDomain) > 0 && trimmedDomain[0] == '.' {
1193                                         // constraints can have a leading
1194                                         // period to exclude the domain
1195                                         // itself, but that's not valid in a
1196                                         // normal domain name.
1197                                         trimmedDomain = trimmedDomain[1:]
1198                                 }
1199                                 if _, ok := domainToReverseLabels(trimmedDomain); !ok {
1200                                         return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse dnsName constraint %q", domain)
1201                                 }
1202                                 dnsNames = append(dnsNames, domain)
1203
1204                         case ipTag:
1205                                 l := len(value)
1206                                 var ip, mask []byte
1207
1208                                 switch l {
1209                                 case 8:
1210                                         ip = value[:4]
1211                                         mask = value[4:]
1212
1213                                 case 32:
1214                                         ip = value[:16]
1215                                         mask = value[16:]
1216
1217                                 default:
1218                                         return nil, nil, nil, nil, fmt.Errorf("x509: IP constraint contained value of length %d", l)
1219                                 }
1220
1221                                 if !isValidIPMask(mask) {
1222                                         return nil, nil, nil, nil, fmt.Errorf("x509: IP constraint contained invalid mask %x", mask)
1223                                 }
1224
1225                                 ips = append(ips, &net.IPNet{IP: net.IP(ip), Mask: net.IPMask(mask)})
1226
1227                         case emailTag:
1228                                 constraint := string(value)
1229                                 if err := isIA5String(constraint); err != nil {
1230                                         return nil, nil, nil, nil, errors.New("x509: invalid constraint value: " + err.Error())
1231                                 }
1232
1233                                 // If the constraint contains an @ then
1234                                 // it specifies an exact mailbox name.
1235                                 if strings.Contains(constraint, "@") {
1236                                         if _, ok := parseRFC2821Mailbox(constraint); !ok {
1237                                                 return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse rfc822Name constraint %q", constraint)
1238                                         }
1239                                 } else {
1240                                         // Otherwise it's a domain name.
1241                                         domain := constraint
1242                                         if len(domain) > 0 && domain[0] == '.' {
1243                                                 domain = domain[1:]
1244                                         }
1245                                         if _, ok := domainToReverseLabels(domain); !ok {
1246                                                 return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse rfc822Name constraint %q", constraint)
1247                                         }
1248                                 }
1249                                 emails = append(emails, constraint)
1250
1251                         case uriTag:
1252                                 domain := string(value)
1253                                 if err := isIA5String(domain); err != nil {
1254                                         return nil, nil, nil, nil, errors.New("x509: invalid constraint value: " + err.Error())
1255                                 }
1256
1257                                 if net.ParseIP(domain) != nil {
1258                                         return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse URI constraint %q: cannot be IP address", domain)
1259                                 }
1260
1261                                 trimmedDomain := domain
1262                                 if len(trimmedDomain) > 0 && trimmedDomain[0] == '.' {
1263                                         // constraints can have a leading
1264                                         // period to exclude the domain itself,
1265                                         // but that's not valid in a normal
1266                                         // domain name.
1267                                         trimmedDomain = trimmedDomain[1:]
1268                                 }
1269                                 if _, ok := domainToReverseLabels(trimmedDomain); !ok {
1270                                         return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse URI constraint %q", domain)
1271                                 }
1272                                 uriDomains = append(uriDomains, domain)
1273
1274                         default:
1275                                 unhandled = true
1276                         }
1277                 }
1278
1279                 return dnsNames, ips, emails, uriDomains, nil
1280         }
1281
1282         if out.PermittedDNSDomains, out.PermittedIPRanges, out.PermittedEmailAddresses, out.PermittedURIDomains, err = getValues(permitted); err != nil {
1283                 return false, err
1284         }
1285         if out.ExcludedDNSDomains, out.ExcludedIPRanges, out.ExcludedEmailAddresses, out.ExcludedURIDomains, err = getValues(excluded); err != nil {
1286                 return false, err
1287         }
1288         out.PermittedDNSDomainsCritical = e.Critical
1289
1290         return unhandled, nil
1291 }
1292
1293 func parseCertificate(in *certificate) (*Certificate, error) {
1294         out := new(Certificate)
1295         out.Raw = in.Raw
1296         out.RawTBSCertificate = in.TBSCertificate.Raw
1297         out.RawSubjectPublicKeyInfo = in.TBSCertificate.PublicKey.Raw
1298         out.RawSubject = in.TBSCertificate.Subject.FullBytes
1299         out.RawIssuer = in.TBSCertificate.Issuer.FullBytes
1300
1301         out.Signature = in.SignatureValue.RightAlign()
1302         out.SignatureAlgorithm =
1303                 getSignatureAlgorithmFromAI(in.TBSCertificate.SignatureAlgorithm)
1304
1305         out.PublicKeyAlgorithm =
1306                 getPublicKeyAlgorithmFromOID(in.TBSCertificate.PublicKey.Algorithm.Algorithm)
1307         var err error
1308         out.PublicKey, err = parsePublicKey(out.PublicKeyAlgorithm, &in.TBSCertificate.PublicKey)
1309         if err != nil {
1310                 return nil, err
1311         }
1312
1313         out.Version = in.TBSCertificate.Version + 1
1314         out.SerialNumber = in.TBSCertificate.SerialNumber
1315
1316         var issuer, subject pkix.RDNSequence
1317         if rest, err := asn1.Unmarshal(in.TBSCertificate.Subject.FullBytes, &subject); err != nil {
1318                 return nil, err
1319         } else if len(rest) != 0 {
1320                 return nil, errors.New("x509: trailing data after X.509 subject")
1321         }
1322         if rest, err := asn1.Unmarshal(in.TBSCertificate.Issuer.FullBytes, &issuer); err != nil {
1323                 return nil, err
1324         } else if len(rest) != 0 {
1325                 return nil, errors.New("x509: trailing data after X.509 issuer")
1326         }
1327
1328         out.Issuer.FillFromRDNSequence(&issuer)
1329         out.Subject.FillFromRDNSequence(&subject)
1330
1331         out.NotBefore = in.TBSCertificate.Validity.NotBefore
1332         out.NotAfter = in.TBSCertificate.Validity.NotAfter
1333
1334         for _, e := range in.TBSCertificate.Extensions {
1335                 out.Extensions = append(out.Extensions, e)
1336                 unhandled := false
1337
1338                 if len(e.Id) == 4 && e.Id[0] == 2 && e.Id[1] == 5 && e.Id[2] == 29 {
1339                         switch e.Id[3] {
1340                         case 15:
1341                                 out.KeyUsage, err = parseKeyUsageExtension(e.Value)
1342                                 if err != nil {
1343                                         return nil, err
1344                                 }
1345                         case 19:
1346                                 out.IsCA, out.MaxPathLen, err = parseBasicConstraintsExtension(e.Value)
1347                                 if err != nil {
1348                                         return nil, err
1349                                 }
1350                                 out.BasicConstraintsValid = true
1351                                 out.MaxPathLenZero = out.MaxPathLen == 0
1352                         case 17:
1353                                 out.DNSNames, out.EmailAddresses, out.IPAddresses, out.URIs, err = parseSANExtension(e.Value)
1354                                 if err != nil {
1355                                         return nil, err
1356                                 }
1357
1358                                 if len(out.DNSNames) == 0 && len(out.EmailAddresses) == 0 && len(out.IPAddresses) == 0 && len(out.URIs) == 0 {
1359                                         // If we didn't parse anything then we do the critical check, below.
1360                                         unhandled = true
1361                                 }
1362
1363                         case 30:
1364                                 unhandled, err = parseNameConstraintsExtension(out, e)
1365                                 if err != nil {
1366                                         return nil, err
1367                                 }
1368
1369                         case 31:
1370                                 // RFC 5280, 4.2.1.13
1371
1372                                 // CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint
1373                                 //
1374                                 // DistributionPoint ::= SEQUENCE {
1375                                 //     distributionPoint       [0]     DistributionPointName OPTIONAL,
1376                                 //     reasons                 [1]     ReasonFlags OPTIONAL,
1377                                 //     cRLIssuer               [2]     GeneralNames OPTIONAL }
1378                                 //
1379                                 // DistributionPointName ::= CHOICE {
1380                                 //     fullName                [0]     GeneralNames,
1381                                 //     nameRelativeToCRLIssuer [1]     RelativeDistinguishedName }
1382
1383                                 var cdp []distributionPoint
1384                                 if rest, err := asn1.Unmarshal(e.Value, &cdp); err != nil {
1385                                         return nil, err
1386                                 } else if len(rest) != 0 {
1387                                         return nil, errors.New("x509: trailing data after X.509 CRL distribution point")
1388                                 }
1389
1390                                 for _, dp := range cdp {
1391                                         // Per RFC 5280, 4.2.1.13, one of distributionPoint or cRLIssuer may be empty.
1392                                         if len(dp.DistributionPoint.FullName) == 0 {
1393                                                 continue
1394                                         }
1395
1396                                         for _, fullName := range dp.DistributionPoint.FullName {
1397                                                 if fullName.Tag == 6 {
1398                                                         out.CRLDistributionPoints = append(out.CRLDistributionPoints, string(fullName.Bytes))
1399                                                 }
1400                                         }
1401                                 }
1402
1403                         case 35:
1404                                 // RFC 5280, 4.2.1.1
1405                                 var a authKeyId
1406                                 if rest, err := asn1.Unmarshal(e.Value, &a); err != nil {
1407                                         return nil, err
1408                                 } else if len(rest) != 0 {
1409                                         return nil, errors.New("x509: trailing data after X.509 authority key-id")
1410                                 }
1411                                 out.AuthorityKeyId = a.Id
1412
1413                         case 37:
1414                                 out.ExtKeyUsage, out.UnknownExtKeyUsage, err = parseExtKeyUsageExtension(e.Value)
1415                                 if err != nil {
1416                                         return nil, err
1417                                 }
1418                         case 14:
1419                                 out.SubjectKeyId, err = parseSubjectKeyIdExtension(e.Value)
1420                                 if err != nil {
1421                                         return nil, err
1422                                 }
1423                         case 32:
1424                                 out.PolicyIdentifiers, err = parseCertificatePoliciesExtension(e.Value)
1425                                 if err != nil {
1426                                         return nil, err
1427                                 }
1428                         default:
1429                                 // Unknown extensions are recorded if critical.
1430                                 unhandled = true
1431                         }
1432                 } else if e.Id.Equal(oidExtensionAuthorityInfoAccess) {
1433                         // RFC 5280 4.2.2.1: Authority Information Access
1434                         var aia []authorityInfoAccess
1435                         if rest, err := asn1.Unmarshal(e.Value, &aia); err != nil {
1436                                 return nil, err
1437                         } else if len(rest) != 0 {
1438                                 return nil, errors.New("x509: trailing data after X.509 authority information")
1439                         }
1440
1441                         for _, v := range aia {
1442                                 // GeneralName: uniformResourceIdentifier [6] IA5String
1443                                 if v.Location.Tag != 6 {
1444                                         continue
1445                                 }
1446                                 if v.Method.Equal(oidAuthorityInfoAccessOcsp) {
1447                                         out.OCSPServer = append(out.OCSPServer, string(v.Location.Bytes))
1448                                 } else if v.Method.Equal(oidAuthorityInfoAccessIssuers) {
1449                                         out.IssuingCertificateURL = append(out.IssuingCertificateURL, string(v.Location.Bytes))
1450                                 }
1451                         }
1452                 } else {
1453                         // Unknown extensions are recorded if critical.
1454                         unhandled = true
1455                 }
1456
1457                 if e.Critical && unhandled {
1458                         out.UnhandledCriticalExtensions = append(out.UnhandledCriticalExtensions, e.Id)
1459                 }
1460         }
1461
1462         return out, nil
1463 }
1464
1465 // parseKeyUsageExtension parses id-ce-keyUsage (2.5.29.15) from RFC 5280
1466 // Section 4.2.1.3
1467 func parseKeyUsageExtension(ext []byte) (KeyUsage, error) {
1468         var usageBits asn1.BitString
1469         if rest, err := asn1.Unmarshal(ext, &usageBits); err != nil {
1470                 return 0, err
1471         } else if len(rest) != 0 {
1472                 return 0, errors.New("x509: trailing data after X.509 KeyUsage")
1473         }
1474
1475         var usage int
1476         for i := 0; i < 9; i++ {
1477                 if usageBits.At(i) != 0 {
1478                         usage |= 1 << uint(i)
1479                 }
1480         }
1481         return KeyUsage(usage), nil
1482 }
1483
1484 // parseBasicConstraintsExtension parses id-ce-basicConstraints (2.5.29.19)
1485 // from RFC 5280 Section 4.2.1.9
1486 func parseBasicConstraintsExtension(ext []byte) (isCA bool, maxPathLen int, err error) {
1487         var constraints basicConstraints
1488         if rest, err := asn1.Unmarshal(ext, &constraints); err != nil {
1489                 return false, 0, err
1490         } else if len(rest) != 0 {
1491                 return false, 0, errors.New("x509: trailing data after X.509 BasicConstraints")
1492         }
1493
1494         // TODO: map out.MaxPathLen to 0 if it has the -1 default value? (Issue 19285)
1495         return constraints.IsCA, constraints.MaxPathLen, nil
1496 }
1497
1498 // parseExtKeyUsageExtension parses id-ce-extKeyUsage (2.5.29.37) from
1499 // RFC 5280 Section 4.2.1.12
1500 func parseExtKeyUsageExtension(ext []byte) ([]ExtKeyUsage, []asn1.ObjectIdentifier, error) {
1501         var keyUsage []asn1.ObjectIdentifier
1502         if rest, err := asn1.Unmarshal(ext, &keyUsage); err != nil {
1503                 return nil, nil, err
1504         } else if len(rest) != 0 {
1505                 return nil, nil, errors.New("x509: trailing data after X.509 ExtendedKeyUsage")
1506         }
1507
1508         var extKeyUsages []ExtKeyUsage
1509         var unknownUsages []asn1.ObjectIdentifier
1510         for _, u := range keyUsage {
1511                 if extKeyUsage, ok := extKeyUsageFromOID(u); ok {
1512                         extKeyUsages = append(extKeyUsages, extKeyUsage)
1513                 } else {
1514                         unknownUsages = append(unknownUsages, u)
1515                 }
1516         }
1517         return extKeyUsages, unknownUsages, nil
1518 }
1519
1520 // parseSubjectKeyIdExtension parses id-ce-subjectKeyIdentifier (2.5.29.14)
1521 // from RFC 5280 Section 4.2.1.2
1522 func parseSubjectKeyIdExtension(ext []byte) ([]byte, error) {
1523         var keyid []byte
1524         if rest, err := asn1.Unmarshal(ext, &keyid); err != nil {
1525                 return nil, err
1526         } else if len(rest) != 0 {
1527                 return nil, errors.New("x509: trailing data after X.509 key-id")
1528         }
1529         return keyid, nil
1530 }
1531
1532 func parseCertificatePoliciesExtension(ext []byte) ([]asn1.ObjectIdentifier, error) {
1533         var policies []policyInformation
1534         if rest, err := asn1.Unmarshal(ext, &policies); err != nil {
1535                 return nil, err
1536         } else if len(rest) != 0 {
1537                 return nil, errors.New("x509: trailing data after X.509 certificate policies")
1538         }
1539         oids := make([]asn1.ObjectIdentifier, len(policies))
1540         for i, policy := range policies {
1541                 oids[i] = policy.Policy
1542         }
1543         return oids, nil
1544 }
1545
1546 // ParseCertificate parses a single certificate from the given ASN.1 DER data.
1547 func ParseCertificate(asn1Data []byte) (*Certificate, error) {
1548         var cert certificate
1549         rest, err := asn1.Unmarshal(asn1Data, &cert)
1550         if err != nil {
1551                 return nil, err
1552         }
1553         if len(rest) > 0 {
1554                 return nil, asn1.SyntaxError{Msg: "trailing data"}
1555         }
1556
1557         return parseCertificate(&cert)
1558 }
1559
1560 // ParseCertificates parses one or more certificates from the given ASN.1 DER
1561 // data. The certificates must be concatenated with no intermediate padding.
1562 func ParseCertificates(asn1Data []byte) ([]*Certificate, error) {
1563         var v []*certificate
1564
1565         for len(asn1Data) > 0 {
1566                 cert := new(certificate)
1567                 var err error
1568                 asn1Data, err = asn1.Unmarshal(asn1Data, cert)
1569                 if err != nil {
1570                         return nil, err
1571                 }
1572                 v = append(v, cert)
1573         }
1574
1575         ret := make([]*Certificate, len(v))
1576         for i, ci := range v {
1577                 cert, err := parseCertificate(ci)
1578                 if err != nil {
1579                         return nil, err
1580                 }
1581                 ret[i] = cert
1582         }
1583
1584         return ret, nil
1585 }
1586
1587 func reverseBitsInAByte(in byte) byte {
1588         b1 := in>>4 | in<<4
1589         b2 := b1>>2&0x33 | b1<<2&0xcc
1590         b3 := b2>>1&0x55 | b2<<1&0xaa
1591         return b3
1592 }
1593
1594 // asn1BitLength returns the bit-length of bitString by considering the
1595 // most-significant bit in a byte to be the "first" bit. This convention
1596 // matches ASN.1, but differs from almost everything else.
1597 func asn1BitLength(bitString []byte) int {
1598         bitLen := len(bitString) * 8
1599
1600         for i := range bitString {
1601                 b := bitString[len(bitString)-i-1]
1602
1603                 for bit := uint(0); bit < 8; bit++ {
1604                         if (b>>bit)&1 == 1 {
1605                                 return bitLen
1606                         }
1607                         bitLen--
1608                 }
1609         }
1610
1611         return 0
1612 }
1613
1614 var (
1615         oidExtensionSubjectKeyId          = []int{2, 5, 29, 14}
1616         oidExtensionKeyUsage              = []int{2, 5, 29, 15}
1617         oidExtensionExtendedKeyUsage      = []int{2, 5, 29, 37}
1618         oidExtensionAuthorityKeyId        = []int{2, 5, 29, 35}
1619         oidExtensionBasicConstraints      = []int{2, 5, 29, 19}
1620         oidExtensionSubjectAltName        = []int{2, 5, 29, 17}
1621         oidExtensionCertificatePolicies   = []int{2, 5, 29, 32}
1622         oidExtensionNameConstraints       = []int{2, 5, 29, 30}
1623         oidExtensionCRLDistributionPoints = []int{2, 5, 29, 31}
1624         oidExtensionAuthorityInfoAccess   = []int{1, 3, 6, 1, 5, 5, 7, 1, 1}
1625         oidExtensionCRLNumber             = []int{2, 5, 29, 20}
1626 )
1627
1628 var (
1629         oidAuthorityInfoAccessOcsp    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 1}
1630         oidAuthorityInfoAccessIssuers = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 2}
1631 )
1632
1633 // oidNotInExtensions reports whether an extension with the given oid exists in
1634 // extensions.
1635 func oidInExtensions(oid asn1.ObjectIdentifier, extensions []pkix.Extension) bool {
1636         for _, e := range extensions {
1637                 if e.Id.Equal(oid) {
1638                         return true
1639                 }
1640         }
1641         return false
1642 }
1643
1644 // marshalSANs marshals a list of addresses into a the contents of an X.509
1645 // SubjectAlternativeName extension.
1646 func marshalSANs(dnsNames, emailAddresses []string, ipAddresses []net.IP, uris []*url.URL) (derBytes []byte, err error) {
1647         var rawValues []asn1.RawValue
1648         for _, name := range dnsNames {
1649                 if err := isIA5String(name); err != nil {
1650                         return nil, err
1651                 }
1652                 rawValues = append(rawValues, asn1.RawValue{Tag: nameTypeDNS, Class: 2, Bytes: []byte(name)})
1653         }
1654         for _, email := range emailAddresses {
1655                 if err := isIA5String(email); err != nil {
1656                         return nil, err
1657                 }
1658                 rawValues = append(rawValues, asn1.RawValue{Tag: nameTypeEmail, Class: 2, Bytes: []byte(email)})
1659         }
1660         for _, rawIP := range ipAddresses {
1661                 // If possible, we always want to encode IPv4 addresses in 4 bytes.
1662                 ip := rawIP.To4()
1663                 if ip == nil {
1664                         ip = rawIP
1665                 }
1666                 rawValues = append(rawValues, asn1.RawValue{Tag: nameTypeIP, Class: 2, Bytes: ip})
1667         }
1668         for _, uri := range uris {
1669                 uriStr := uri.String()
1670                 if err := isIA5String(uriStr); err != nil {
1671                         return nil, err
1672                 }
1673                 rawValues = append(rawValues, asn1.RawValue{Tag: nameTypeURI, Class: 2, Bytes: []byte(uriStr)})
1674         }
1675         return asn1.Marshal(rawValues)
1676 }
1677
1678 func isIA5String(s string) error {
1679         for _, r := range s {
1680                 // Per RFC5280 "IA5String is limited to the set of ASCII characters"
1681                 if r > unicode.MaxASCII {
1682                         return fmt.Errorf("x509: %q cannot be encoded as an IA5String", s)
1683                 }
1684         }
1685
1686         return nil
1687 }
1688
1689 func buildCertExtensions(template *Certificate, subjectIsEmpty bool, authorityKeyId []byte, subjectKeyId []byte) (ret []pkix.Extension, err error) {
1690         ret = make([]pkix.Extension, 10 /* maximum number of elements. */)
1691         n := 0
1692
1693         if template.KeyUsage != 0 &&
1694                 !oidInExtensions(oidExtensionKeyUsage, template.ExtraExtensions) {
1695                 ret[n], err = marshalKeyUsage(template.KeyUsage)
1696                 if err != nil {
1697                         return nil, err
1698                 }
1699                 n++
1700         }
1701
1702         if (len(template.ExtKeyUsage) > 0 || len(template.UnknownExtKeyUsage) > 0) &&
1703                 !oidInExtensions(oidExtensionExtendedKeyUsage, template.ExtraExtensions) {
1704                 ret[n], err = marshalExtKeyUsage(template.ExtKeyUsage, template.UnknownExtKeyUsage)
1705                 if err != nil {
1706                         return nil, err
1707                 }
1708                 n++
1709         }
1710
1711         if template.BasicConstraintsValid && !oidInExtensions(oidExtensionBasicConstraints, template.ExtraExtensions) {
1712                 ret[n], err = marshalBasicConstraints(template.IsCA, template.MaxPathLen, template.MaxPathLenZero)
1713                 if err != nil {
1714                         return nil, err
1715                 }
1716                 n++
1717         }
1718
1719         if len(subjectKeyId) > 0 && !oidInExtensions(oidExtensionSubjectKeyId, template.ExtraExtensions) {
1720                 ret[n].Id = oidExtensionSubjectKeyId
1721                 ret[n].Value, err = asn1.Marshal(subjectKeyId)
1722                 if err != nil {
1723                         return
1724                 }
1725                 n++
1726         }
1727
1728         if len(authorityKeyId) > 0 && !oidInExtensions(oidExtensionAuthorityKeyId, template.ExtraExtensions) {
1729                 ret[n].Id = oidExtensionAuthorityKeyId
1730                 ret[n].Value, err = asn1.Marshal(authKeyId{authorityKeyId})
1731                 if err != nil {
1732                         return
1733                 }
1734                 n++
1735         }
1736
1737         if (len(template.OCSPServer) > 0 || len(template.IssuingCertificateURL) > 0) &&
1738                 !oidInExtensions(oidExtensionAuthorityInfoAccess, template.ExtraExtensions) {
1739                 ret[n].Id = oidExtensionAuthorityInfoAccess
1740                 var aiaValues []authorityInfoAccess
1741                 for _, name := range template.OCSPServer {
1742                         aiaValues = append(aiaValues, authorityInfoAccess{
1743                                 Method:   oidAuthorityInfoAccessOcsp,
1744                                 Location: asn1.RawValue{Tag: 6, Class: 2, Bytes: []byte(name)},
1745                         })
1746                 }
1747                 for _, name := range template.IssuingCertificateURL {
1748                         aiaValues = append(aiaValues, authorityInfoAccess{
1749                                 Method:   oidAuthorityInfoAccessIssuers,
1750                                 Location: asn1.RawValue{Tag: 6, Class: 2, Bytes: []byte(name)},
1751                         })
1752                 }
1753                 ret[n].Value, err = asn1.Marshal(aiaValues)
1754                 if err != nil {
1755                         return
1756                 }
1757                 n++
1758         }
1759
1760         if (len(template.DNSNames) > 0 || len(template.EmailAddresses) > 0 || len(template.IPAddresses) > 0 || len(template.URIs) > 0) &&
1761                 !oidInExtensions(oidExtensionSubjectAltName, template.ExtraExtensions) {
1762                 ret[n].Id = oidExtensionSubjectAltName
1763                 // From RFC 5280, Section 4.2.1.6:
1764                 // “If the subject field contains an empty sequence ... then
1765                 // subjectAltName extension ... is marked as critical”
1766                 ret[n].Critical = subjectIsEmpty
1767                 ret[n].Value, err = marshalSANs(template.DNSNames, template.EmailAddresses, template.IPAddresses, template.URIs)
1768                 if err != nil {
1769                         return
1770                 }
1771                 n++
1772         }
1773
1774         if len(template.PolicyIdentifiers) > 0 &&
1775                 !oidInExtensions(oidExtensionCertificatePolicies, template.ExtraExtensions) {
1776                 ret[n], err = marshalCertificatePolicies(template.PolicyIdentifiers)
1777                 if err != nil {
1778                         return nil, err
1779                 }
1780                 n++
1781         }
1782
1783         if (len(template.PermittedDNSDomains) > 0 || len(template.ExcludedDNSDomains) > 0 ||
1784                 len(template.PermittedIPRanges) > 0 || len(template.ExcludedIPRanges) > 0 ||
1785                 len(template.PermittedEmailAddresses) > 0 || len(template.ExcludedEmailAddresses) > 0 ||
1786                 len(template.PermittedURIDomains) > 0 || len(template.ExcludedURIDomains) > 0) &&
1787                 !oidInExtensions(oidExtensionNameConstraints, template.ExtraExtensions) {
1788                 ret[n].Id = oidExtensionNameConstraints
1789                 ret[n].Critical = template.PermittedDNSDomainsCritical
1790
1791                 ipAndMask := func(ipNet *net.IPNet) []byte {
1792                         maskedIP := ipNet.IP.Mask(ipNet.Mask)
1793                         ipAndMask := make([]byte, 0, len(maskedIP)+len(ipNet.Mask))
1794                         ipAndMask = append(ipAndMask, maskedIP...)
1795                         ipAndMask = append(ipAndMask, ipNet.Mask...)
1796                         return ipAndMask
1797                 }
1798
1799                 serialiseConstraints := func(dns []string, ips []*net.IPNet, emails []string, uriDomains []string) (der []byte, err error) {
1800                         var b cryptobyte.Builder
1801
1802                         for _, name := range dns {
1803                                 if err = isIA5String(name); err != nil {
1804                                         return nil, err
1805                                 }
1806
1807                                 b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
1808                                         b.AddASN1(cryptobyte_asn1.Tag(2).ContextSpecific(), func(b *cryptobyte.Builder) {
1809                                                 b.AddBytes([]byte(name))
1810                                         })
1811                                 })
1812                         }
1813
1814                         for _, ipNet := range ips {
1815                                 b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
1816                                         b.AddASN1(cryptobyte_asn1.Tag(7).ContextSpecific(), func(b *cryptobyte.Builder) {
1817                                                 b.AddBytes(ipAndMask(ipNet))
1818                                         })
1819                                 })
1820                         }
1821
1822                         for _, email := range emails {
1823                                 if err = isIA5String(email); err != nil {
1824                                         return nil, err
1825                                 }
1826
1827                                 b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
1828                                         b.AddASN1(cryptobyte_asn1.Tag(1).ContextSpecific(), func(b *cryptobyte.Builder) {
1829                                                 b.AddBytes([]byte(email))
1830                                         })
1831                                 })
1832                         }
1833
1834                         for _, uriDomain := range uriDomains {
1835                                 if err = isIA5String(uriDomain); err != nil {
1836                                         return nil, err
1837                                 }
1838
1839                                 b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
1840                                         b.AddASN1(cryptobyte_asn1.Tag(6).ContextSpecific(), func(b *cryptobyte.Builder) {
1841                                                 b.AddBytes([]byte(uriDomain))
1842                                         })
1843                                 })
1844                         }
1845
1846                         return b.Bytes()
1847                 }
1848
1849                 permitted, err := serialiseConstraints(template.PermittedDNSDomains, template.PermittedIPRanges, template.PermittedEmailAddresses, template.PermittedURIDomains)
1850                 if err != nil {
1851                         return nil, err
1852                 }
1853
1854                 excluded, err := serialiseConstraints(template.ExcludedDNSDomains, template.ExcludedIPRanges, template.ExcludedEmailAddresses, template.ExcludedURIDomains)
1855                 if err != nil {
1856                         return nil, err
1857                 }
1858
1859                 var b cryptobyte.Builder
1860                 b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
1861                         if len(permitted) > 0 {
1862                                 b.AddASN1(cryptobyte_asn1.Tag(0).ContextSpecific().Constructed(), func(b *cryptobyte.Builder) {
1863                                         b.AddBytes(permitted)
1864                                 })
1865                         }
1866
1867                         if len(excluded) > 0 {
1868                                 b.AddASN1(cryptobyte_asn1.Tag(1).ContextSpecific().Constructed(), func(b *cryptobyte.Builder) {
1869                                         b.AddBytes(excluded)
1870                                 })
1871                         }
1872                 })
1873
1874                 ret[n].Value, err = b.Bytes()
1875                 if err != nil {
1876                         return nil, err
1877                 }
1878                 n++
1879         }
1880
1881         if len(template.CRLDistributionPoints) > 0 &&
1882                 !oidInExtensions(oidExtensionCRLDistributionPoints, template.ExtraExtensions) {
1883                 ret[n].Id = oidExtensionCRLDistributionPoints
1884
1885                 var crlDp []distributionPoint
1886                 for _, name := range template.CRLDistributionPoints {
1887                         dp := distributionPoint{
1888                                 DistributionPoint: distributionPointName{
1889                                         FullName: []asn1.RawValue{
1890                                                 {Tag: 6, Class: 2, Bytes: []byte(name)},
1891                                         },
1892                                 },
1893                         }
1894                         crlDp = append(crlDp, dp)
1895                 }
1896
1897                 ret[n].Value, err = asn1.Marshal(crlDp)
1898                 if err != nil {
1899                         return
1900                 }
1901                 n++
1902         }
1903
1904         // Adding another extension here? Remember to update the maximum number
1905         // of elements in the make() at the top of the function and the list of
1906         // template fields used in CreateCertificate documentation.
1907
1908         return append(ret[:n], template.ExtraExtensions...), nil
1909 }
1910
1911 func marshalKeyUsage(ku KeyUsage) (pkix.Extension, error) {
1912         ext := pkix.Extension{Id: oidExtensionKeyUsage, Critical: true}
1913
1914         var a [2]byte
1915         a[0] = reverseBitsInAByte(byte(ku))
1916         a[1] = reverseBitsInAByte(byte(ku >> 8))
1917
1918         l := 1
1919         if a[1] != 0 {
1920                 l = 2
1921         }
1922
1923         bitString := a[:l]
1924         var err error
1925         ext.Value, err = asn1.Marshal(asn1.BitString{Bytes: bitString, BitLength: asn1BitLength(bitString)})
1926         if err != nil {
1927                 return ext, err
1928         }
1929         return ext, nil
1930 }
1931
1932 func marshalExtKeyUsage(extUsages []ExtKeyUsage, unknownUsages []asn1.ObjectIdentifier) (pkix.Extension, error) {
1933         ext := pkix.Extension{Id: oidExtensionExtendedKeyUsage}
1934
1935         oids := make([]asn1.ObjectIdentifier, len(extUsages)+len(unknownUsages))
1936         for i, u := range extUsages {
1937                 if oid, ok := oidFromExtKeyUsage(u); ok {
1938                         oids[i] = oid
1939                 } else {
1940                         return ext, errors.New("x509: unknown extended key usage")
1941                 }
1942         }
1943
1944         copy(oids[len(extUsages):], unknownUsages)
1945
1946         var err error
1947         ext.Value, err = asn1.Marshal(oids)
1948         if err != nil {
1949                 return ext, err
1950         }
1951         return ext, nil
1952 }
1953
1954 func marshalBasicConstraints(isCA bool, maxPathLen int, maxPathLenZero bool) (pkix.Extension, error) {
1955         ext := pkix.Extension{Id: oidExtensionBasicConstraints, Critical: true}
1956         // Leaving MaxPathLen as zero indicates that no maximum path
1957         // length is desired, unless MaxPathLenZero is set. A value of
1958         // -1 causes encoding/asn1 to omit the value as desired.
1959         if maxPathLen == 0 && !maxPathLenZero {
1960                 maxPathLen = -1
1961         }
1962         var err error
1963         ext.Value, err = asn1.Marshal(basicConstraints{isCA, maxPathLen})
1964         if err != nil {
1965                 return ext, nil
1966         }
1967         return ext, nil
1968 }
1969
1970 func marshalCertificatePolicies(policyIdentifiers []asn1.ObjectIdentifier) (pkix.Extension, error) {
1971         ext := pkix.Extension{Id: oidExtensionCertificatePolicies}
1972         policies := make([]policyInformation, len(policyIdentifiers))
1973         for i, policy := range policyIdentifiers {
1974                 policies[i].Policy = policy
1975         }
1976         var err error
1977         ext.Value, err = asn1.Marshal(policies)
1978         if err != nil {
1979                 return ext, err
1980         }
1981         return ext, nil
1982 }
1983
1984 func buildCSRExtensions(template *CertificateRequest) ([]pkix.Extension, error) {
1985         var ret []pkix.Extension
1986
1987         if (len(template.DNSNames) > 0 || len(template.EmailAddresses) > 0 || len(template.IPAddresses) > 0 || len(template.URIs) > 0) &&
1988                 !oidInExtensions(oidExtensionSubjectAltName, template.ExtraExtensions) {
1989                 sanBytes, err := marshalSANs(template.DNSNames, template.EmailAddresses, template.IPAddresses, template.URIs)
1990                 if err != nil {
1991                         return nil, err
1992                 }
1993
1994                 ret = append(ret, pkix.Extension{
1995                         Id:    oidExtensionSubjectAltName,
1996                         Value: sanBytes,
1997                 })
1998         }
1999
2000         if template.KeyUsage != 0 &&
2001                 !oidInExtensions(oidExtensionKeyUsage, template.ExtraExtensions) {
2002                 ext, err := marshalKeyUsage(template.KeyUsage)
2003                 if err != nil {
2004                         return nil, err
2005                 }
2006                 ret = append(ret, ext)
2007         }
2008
2009         return append(ret, template.ExtraExtensions...), nil
2010 }
2011
2012 func subjectBytes(cert *Certificate) ([]byte, error) {
2013         if len(cert.RawSubject) > 0 {
2014                 return cert.RawSubject, nil
2015         }
2016
2017         return asn1.Marshal(cert.Subject.ToRDNSequence())
2018 }
2019
2020 // signingParamsForPublicKey returns the parameters to use for signing with
2021 // priv. If requestedSigAlgo is not zero then it overrides the default
2022 // signature algorithm.
2023 func signingParamsForPublicKey(pub interface{}, requestedSigAlgo SignatureAlgorithm) (hashFunc crypto.Hash, sigAlgo pkix.AlgorithmIdentifier, err error) {
2024         var pubType PublicKeyAlgorithm
2025
2026         switch pub := pub.(type) {
2027         case *rsa.PublicKey:
2028                 pubType = RSA
2029                 hashFunc = crypto.SHA256
2030                 sigAlgo.Algorithm = oidSignatureSHA256WithRSA
2031                 sigAlgo.Parameters = asn1.NullRawValue
2032
2033         case *ecdsa.PublicKey:
2034                 pubType = ECDSA
2035
2036                 switch pub.Curve {
2037                 case elliptic.P224(), elliptic.P256():
2038                         hashFunc = crypto.SHA256
2039                         sigAlgo.Algorithm = oidSignatureECDSAWithSHA256
2040                 case elliptic.P384():
2041                         hashFunc = crypto.SHA384
2042                         sigAlgo.Algorithm = oidSignatureECDSAWithSHA384
2043                 case elliptic.P521():
2044                         hashFunc = crypto.SHA512
2045                         sigAlgo.Algorithm = oidSignatureECDSAWithSHA512
2046                 default:
2047                         err = errors.New("x509: unknown elliptic curve")
2048                 }
2049
2050         case ed25519.PublicKey:
2051                 pubType = Ed25519
2052                 sigAlgo.Algorithm = oidSignatureEd25519
2053
2054         default:
2055                 err = errors.New("x509: only RSA, ECDSA and Ed25519 keys supported")
2056         }
2057
2058         if err != nil {
2059                 return
2060         }
2061
2062         if requestedSigAlgo == 0 {
2063                 return
2064         }
2065
2066         found := false
2067         for _, details := range signatureAlgorithmDetails {
2068                 if details.algo == requestedSigAlgo {
2069                         if details.pubKeyAlgo != pubType {
2070                                 err = errors.New("x509: requested SignatureAlgorithm does not match private key type")
2071                                 return
2072                         }
2073                         sigAlgo.Algorithm, hashFunc = details.oid, details.hash
2074                         if hashFunc == 0 && pubType != Ed25519 {
2075                                 err = errors.New("x509: cannot sign with hash function requested")
2076                                 return
2077                         }
2078                         if requestedSigAlgo.isRSAPSS() {
2079                                 sigAlgo.Parameters = hashToPSSParameters[hashFunc]
2080                         }
2081                         found = true
2082                         break
2083                 }
2084         }
2085
2086         if !found {
2087                 err = errors.New("x509: unknown SignatureAlgorithm")
2088         }
2089
2090         return
2091 }
2092
2093 // emptyASN1Subject is the ASN.1 DER encoding of an empty Subject, which is
2094 // just an empty SEQUENCE.
2095 var emptyASN1Subject = []byte{0x30, 0}
2096
2097 // CreateCertificate creates a new X.509v3 certificate based on a template.
2098 // The following members of template are used:
2099 //
2100 //  - AuthorityKeyId
2101 //  - BasicConstraintsValid
2102 //  - CRLDistributionPoints
2103 //  - DNSNames
2104 //  - EmailAddresses
2105 //  - ExcludedDNSDomains
2106 //  - ExcludedEmailAddresses
2107 //  - ExcludedIPRanges
2108 //  - ExcludedURIDomains
2109 //  - ExtKeyUsage
2110 //  - ExtraExtensions
2111 //  - IPAddresses
2112 //  - IsCA
2113 //  - IssuingCertificateURL
2114 //  - KeyUsage
2115 //  - MaxPathLen
2116 //  - MaxPathLenZero
2117 //  - NotAfter
2118 //  - NotBefore
2119 //  - OCSPServer
2120 //  - PermittedDNSDomains
2121 //  - PermittedDNSDomainsCritical
2122 //  - PermittedEmailAddresses
2123 //  - PermittedIPRanges
2124 //  - PermittedURIDomains
2125 //  - PolicyIdentifiers
2126 //  - SerialNumber
2127 //  - SignatureAlgorithm
2128 //  - Subject
2129 //  - SubjectKeyId
2130 //  - URIs
2131 //  - UnknownExtKeyUsage
2132 //
2133 // The certificate is signed by parent. If parent is equal to template then the
2134 // certificate is self-signed. The parameter pub is the public key of the
2135 // signee and priv is the private key of the signer.
2136 //
2137 // The returned slice is the certificate in DER encoding.
2138 //
2139 // The currently supported key types are *rsa.PublicKey, *ecdsa.PublicKey and
2140 // ed25519.PublicKey. pub must be a supported key type, and priv must be a
2141 // crypto.Signer with a supported public key.
2142 //
2143 // The AuthorityKeyId will be taken from the SubjectKeyId of parent, if any,
2144 // unless the resulting certificate is self-signed. Otherwise the value from
2145 // template will be used.
2146 //
2147 // If SubjectKeyId from template is empty and the template is a CA, SubjectKeyId
2148 // will be generated from the hash of the public key.
2149 func CreateCertificate(rand io.Reader, template, parent *Certificate, pub, priv interface{}) (cert []byte, err error) {
2150         key, ok := priv.(crypto.Signer)
2151         if !ok {
2152                 return nil, errors.New("x509: certificate private key does not implement crypto.Signer")
2153         }
2154
2155         if template.SerialNumber == nil {
2156                 return nil, errors.New("x509: no SerialNumber given")
2157         }
2158
2159         if template.BasicConstraintsValid && !template.IsCA && template.MaxPathLen != -1 && (template.MaxPathLen != 0 || template.MaxPathLenZero) {
2160                 return nil, errors.New("x509: only CAs are allowed to specify MaxPathLen")
2161         }
2162
2163         hashFunc, signatureAlgorithm, err := signingParamsForPublicKey(key.Public(), template.SignatureAlgorithm)
2164         if err != nil {
2165                 return nil, err
2166         }
2167
2168         publicKeyBytes, publicKeyAlgorithm, err := marshalPublicKey(pub)
2169         if err != nil {
2170                 return nil, err
2171         }
2172
2173         asn1Issuer, err := subjectBytes(parent)
2174         if err != nil {
2175                 return
2176         }
2177
2178         asn1Subject, err := subjectBytes(template)
2179         if err != nil {
2180                 return
2181         }
2182
2183         authorityKeyId := template.AuthorityKeyId
2184         if !bytes.Equal(asn1Issuer, asn1Subject) && len(parent.SubjectKeyId) > 0 {
2185                 authorityKeyId = parent.SubjectKeyId
2186         }
2187
2188         subjectKeyId := template.SubjectKeyId
2189         if len(subjectKeyId) == 0 && template.IsCA {
2190                 // SubjectKeyId generated using method 1 in RFC 5280, Section 4.2.1.2:
2191                 //   (1) The keyIdentifier is composed of the 160-bit SHA-1 hash of the
2192                 //   value of the BIT STRING subjectPublicKey (excluding the tag,
2193                 //   length, and number of unused bits).
2194                 h := sha1.Sum(publicKeyBytes)
2195                 subjectKeyId = h[:]
2196         }
2197
2198         extensions, err := buildCertExtensions(template, bytes.Equal(asn1Subject, emptyASN1Subject), authorityKeyId, subjectKeyId)
2199         if err != nil {
2200                 return
2201         }
2202
2203         encodedPublicKey := asn1.BitString{BitLength: len(publicKeyBytes) * 8, Bytes: publicKeyBytes}
2204         c := tbsCertificate{
2205                 Version:            2,
2206                 SerialNumber:       template.SerialNumber,
2207                 SignatureAlgorithm: signatureAlgorithm,
2208                 Issuer:             asn1.RawValue{FullBytes: asn1Issuer},
2209                 Validity:           validity{template.NotBefore.UTC(), template.NotAfter.UTC()},
2210                 Subject:            asn1.RawValue{FullBytes: asn1Subject},
2211                 PublicKey:          publicKeyInfo{nil, publicKeyAlgorithm, encodedPublicKey},
2212                 Extensions:         extensions,
2213         }
2214
2215         tbsCertContents, err := asn1.Marshal(c)
2216         if err != nil {
2217                 return
2218         }
2219         c.Raw = tbsCertContents
2220
2221         signed := tbsCertContents
2222         if hashFunc != 0 {
2223                 h := hashFunc.New()
2224                 h.Write(signed)
2225                 signed = h.Sum(nil)
2226         }
2227
2228         var signerOpts crypto.SignerOpts = hashFunc
2229         if template.SignatureAlgorithm != 0 && template.SignatureAlgorithm.isRSAPSS() {
2230                 signerOpts = &rsa.PSSOptions{
2231                         SaltLength: rsa.PSSSaltLengthEqualsHash,
2232                         Hash:       hashFunc,
2233                 }
2234         }
2235
2236         var signature []byte
2237         signature, err = key.Sign(rand, signed, signerOpts)
2238         if err != nil {
2239                 return
2240         }
2241
2242         signedCert, err := asn1.Marshal(certificate{
2243                 nil,
2244                 c,
2245                 signatureAlgorithm,
2246                 asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
2247         })
2248         if err != nil {
2249                 return nil, err
2250         }
2251
2252         // Check the signature to ensure the crypto.Signer behaved correctly.
2253         // We skip this check if the signature algorithm is MD5WithRSA as we
2254         // only support this algorithm for signing, and not verification.
2255         if sigAlg := getSignatureAlgorithmFromAI(signatureAlgorithm); sigAlg != MD5WithRSA {
2256                 if err := checkSignature(sigAlg, c.Raw, signature, key.Public()); err != nil {
2257                         return nil, fmt.Errorf("x509: signature over certificate returned by signer is invalid: %w", err)
2258                 }
2259         }
2260
2261         return signedCert, nil
2262 }
2263
2264 // pemCRLPrefix is the magic string that indicates that we have a PEM encoded
2265 // CRL.
2266 var pemCRLPrefix = []byte("-----BEGIN X509 CRL")
2267
2268 // pemType is the type of a PEM encoded CRL.
2269 var pemType = "X509 CRL"
2270
2271 // ParseCRL parses a CRL from the given bytes. It's often the case that PEM
2272 // encoded CRLs will appear where they should be DER encoded, so this function
2273 // will transparently handle PEM encoding as long as there isn't any leading
2274 // garbage.
2275 func ParseCRL(crlBytes []byte) (*pkix.CertificateList, error) {
2276         if bytes.HasPrefix(crlBytes, pemCRLPrefix) {
2277                 block, _ := pem.Decode(crlBytes)
2278                 if block != nil && block.Type == pemType {
2279                         crlBytes = block.Bytes
2280                 }
2281         }
2282         return ParseDERCRL(crlBytes)
2283 }
2284
2285 // ParseDERCRL parses a DER encoded CRL from the given bytes.
2286 func ParseDERCRL(derBytes []byte) (*pkix.CertificateList, error) {
2287         certList := new(pkix.CertificateList)
2288         if rest, err := asn1.Unmarshal(derBytes, certList); err != nil {
2289                 return nil, err
2290         } else if len(rest) != 0 {
2291                 return nil, errors.New("x509: trailing data after CRL")
2292         }
2293         return certList, nil
2294 }
2295
2296 // CreateCRL returns a DER encoded CRL, signed by this Certificate, that
2297 // contains the given list of revoked certificates.
2298 //
2299 // Note: this method does not generate an RFC 5280 conformant X.509 v2 CRL.
2300 // To generate a standards compliant CRL, use CreateRevocationList instead.
2301 func (c *Certificate) CreateCRL(rand io.Reader, priv interface{}, revokedCerts []pkix.RevokedCertificate, now, expiry time.Time) (crlBytes []byte, err error) {
2302         key, ok := priv.(crypto.Signer)
2303         if !ok {
2304                 return nil, errors.New("x509: certificate private key does not implement crypto.Signer")
2305         }
2306
2307         hashFunc, signatureAlgorithm, err := signingParamsForPublicKey(key.Public(), 0)
2308         if err != nil {
2309                 return nil, err
2310         }
2311
2312         // Force revocation times to UTC per RFC 5280.
2313         revokedCertsUTC := make([]pkix.RevokedCertificate, len(revokedCerts))
2314         for i, rc := range revokedCerts {
2315                 rc.RevocationTime = rc.RevocationTime.UTC()
2316                 revokedCertsUTC[i] = rc
2317         }
2318
2319         tbsCertList := pkix.TBSCertificateList{
2320                 Version:             1,
2321                 Signature:           signatureAlgorithm,
2322                 Issuer:              c.Subject.ToRDNSequence(),
2323                 ThisUpdate:          now.UTC(),
2324                 NextUpdate:          expiry.UTC(),
2325                 RevokedCertificates: revokedCertsUTC,
2326         }
2327
2328         // Authority Key Id
2329         if len(c.SubjectKeyId) > 0 {
2330                 var aki pkix.Extension
2331                 aki.Id = oidExtensionAuthorityKeyId
2332                 aki.Value, err = asn1.Marshal(authKeyId{Id: c.SubjectKeyId})
2333                 if err != nil {
2334                         return
2335                 }
2336                 tbsCertList.Extensions = append(tbsCertList.Extensions, aki)
2337         }
2338
2339         tbsCertListContents, err := asn1.Marshal(tbsCertList)
2340         if err != nil {
2341                 return
2342         }
2343
2344         signed := tbsCertListContents
2345         if hashFunc != 0 {
2346                 h := hashFunc.New()
2347                 h.Write(signed)
2348                 signed = h.Sum(nil)
2349         }
2350
2351         var signature []byte
2352         signature, err = key.Sign(rand, signed, hashFunc)
2353         if err != nil {
2354                 return
2355         }
2356
2357         return asn1.Marshal(pkix.CertificateList{
2358                 TBSCertList:        tbsCertList,
2359                 SignatureAlgorithm: signatureAlgorithm,
2360                 SignatureValue:     asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
2361         })
2362 }
2363
2364 // CertificateRequest represents a PKCS #10, certificate signature request.
2365 type CertificateRequest struct {
2366         Raw                      []byte // Complete ASN.1 DER content (CSR, signature algorithm and signature).
2367         RawTBSCertificateRequest []byte // Certificate request info part of raw ASN.1 DER content.
2368         RawSubjectPublicKeyInfo  []byte // DER encoded SubjectPublicKeyInfo.
2369         RawSubject               []byte // DER encoded Subject.
2370
2371         Version            int
2372         Signature          []byte
2373         SignatureAlgorithm SignatureAlgorithm
2374         KeyUsage           KeyUsage
2375
2376         PublicKeyAlgorithm PublicKeyAlgorithm
2377         PublicKey          interface{}
2378
2379         Subject pkix.Name
2380
2381         // Attributes contains the CSR attributes that can parse as
2382         // pkix.AttributeTypeAndValueSET.
2383         //
2384         // Deprecated: Use Extensions and ExtraExtensions instead for parsing and
2385         // generating the requestedExtensions attribute.
2386         Attributes []pkix.AttributeTypeAndValueSET
2387
2388         // Extensions contains all requested extensions, in raw form. When parsing
2389         // CSRs, this can be used to extract extensions that are not parsed by this
2390         // package.
2391         Extensions []pkix.Extension
2392
2393         // ExtraExtensions contains extensions to be copied, raw, into any CSR
2394         // marshaled by CreateCertificateRequest. Values override any extensions
2395         // that would otherwise be produced based on the other fields but are
2396         // overridden by any extensions specified in Attributes.
2397         //
2398         // The ExtraExtensions field is not populated by ParseCertificateRequest,
2399         // see Extensions instead.
2400         ExtraExtensions []pkix.Extension
2401
2402         // Subject Alternate Name values.
2403         DNSNames       []string
2404         EmailAddresses []string
2405         IPAddresses    []net.IP
2406         URIs           []*url.URL
2407 }
2408
2409 // These structures reflect the ASN.1 structure of X.509 certificate
2410 // signature requests (see RFC 2986):
2411
2412 type tbsCertificateRequest struct {
2413         Raw           asn1.RawContent
2414         Version       int
2415         Subject       asn1.RawValue
2416         PublicKey     publicKeyInfo
2417         RawAttributes []asn1.RawValue `asn1:"tag:0"`
2418 }
2419
2420 type certificateRequest struct {
2421         Raw                asn1.RawContent
2422         TBSCSR             tbsCertificateRequest
2423         SignatureAlgorithm pkix.AlgorithmIdentifier
2424         SignatureValue     asn1.BitString
2425 }
2426
2427 // oidExtensionRequest is a PKCS #9 OBJECT IDENTIFIER that indicates requested
2428 // extensions in a CSR.
2429 var oidExtensionRequest = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 14}
2430
2431 // newRawAttributes converts AttributeTypeAndValueSETs from a template
2432 // CertificateRequest's Attributes into tbsCertificateRequest RawAttributes.
2433 func newRawAttributes(attributes []pkix.AttributeTypeAndValueSET) ([]asn1.RawValue, error) {
2434         var rawAttributes []asn1.RawValue
2435         b, err := asn1.Marshal(attributes)
2436         if err != nil {
2437                 return nil, err
2438         }
2439         rest, err := asn1.Unmarshal(b, &rawAttributes)
2440         if err != nil {
2441                 return nil, err
2442         }
2443         if len(rest) != 0 {
2444                 return nil, errors.New("x509: failed to unmarshal raw CSR Attributes")
2445         }
2446         return rawAttributes, nil
2447 }
2448
2449 // parseRawAttributes Unmarshals RawAttributes into AttributeTypeAndValueSETs.
2450 func parseRawAttributes(rawAttributes []asn1.RawValue) []pkix.AttributeTypeAndValueSET {
2451         var attributes []pkix.AttributeTypeAndValueSET
2452         for _, rawAttr := range rawAttributes {
2453                 var attr pkix.AttributeTypeAndValueSET
2454                 rest, err := asn1.Unmarshal(rawAttr.FullBytes, &attr)
2455                 // Ignore attributes that don't parse into pkix.AttributeTypeAndValueSET
2456                 // (i.e.: challengePassword or unstructuredName).
2457                 if err == nil && len(rest) == 0 {
2458                         attributes = append(attributes, attr)
2459                 }
2460         }
2461         return attributes
2462 }
2463
2464 // parseCSRExtensions parses the attributes from a CSR and extracts any
2465 // requested extensions.
2466 func parseCSRExtensions(rawAttributes []asn1.RawValue) ([]pkix.Extension, error) {
2467         // pkcs10Attribute reflects the Attribute structure from RFC 2986, Section 4.1.
2468         type pkcs10Attribute struct {
2469                 Id     asn1.ObjectIdentifier
2470                 Values []asn1.RawValue `asn1:"set"`
2471         }
2472
2473         var ret []pkix.Extension
2474         for _, rawAttr := range rawAttributes {
2475                 var attr pkcs10Attribute
2476                 if rest, err := asn1.Unmarshal(rawAttr.FullBytes, &attr); err != nil || len(rest) != 0 || len(attr.Values) == 0 {
2477                         // Ignore attributes that don't parse.
2478                         continue
2479                 }
2480
2481                 if !attr.Id.Equal(oidExtensionRequest) {
2482                         continue
2483                 }
2484
2485                 var extensions []pkix.Extension
2486                 if _, err := asn1.Unmarshal(attr.Values[0].FullBytes, &extensions); err != nil {
2487                         return nil, err
2488                 }
2489                 ret = append(ret, extensions...)
2490         }
2491
2492         return ret, nil
2493 }
2494
2495 // CreateCertificateRequest creates a new certificate request based on a
2496 // template. The following members of template are used:
2497 //
2498 //  - SignatureAlgorithm
2499 //  - Subject
2500 //  - DNSNames
2501 //  - EmailAddresses
2502 //  - IPAddresses
2503 //  - URIs
2504 //  - KeyUsage
2505 //  - ExtKeyUsage
2506 //  - UnknownExtKeyUsage
2507 //  - BasicConstraintsValid
2508 //  - IsCA
2509 //  - MaxPathLen
2510 //  - MaxPathLenZero
2511 //  - SubjectKeyId
2512 //  - PolicyIdentifiers
2513 //  - ExtraExtensions
2514 //  - Attributes (deprecated)
2515 //
2516 // priv is the private key to sign the CSR with, and the corresponding public
2517 // key will be included in the CSR. It must implement crypto.Signer and its
2518 // Public() method must return a *rsa.PublicKey or a *ecdsa.PublicKey or a
2519 // ed25519.PublicKey. (A *rsa.PrivateKey, *ecdsa.PrivateKey or
2520 // ed25519.PrivateKey satisfies this.)
2521 //
2522 // The returned slice is the certificate request in DER encoding.
2523 func CreateCertificateRequest(rand io.Reader, template *CertificateRequest, priv interface{}) (csr []byte, err error) {
2524         key, ok := priv.(crypto.Signer)
2525         if !ok {
2526                 return nil, errors.New("x509: certificate private key does not implement crypto.Signer")
2527         }
2528
2529         var hashFunc crypto.Hash
2530         var sigAlgo pkix.AlgorithmIdentifier
2531         hashFunc, sigAlgo, err = signingParamsForPublicKey(key.Public(), template.SignatureAlgorithm)
2532         if err != nil {
2533                 return nil, err
2534         }
2535
2536         var publicKeyBytes []byte
2537         var publicKeyAlgorithm pkix.AlgorithmIdentifier
2538         publicKeyBytes, publicKeyAlgorithm, err = marshalPublicKey(key.Public())
2539         if err != nil {
2540                 return nil, err
2541         }
2542
2543         extensions, err := buildCSRExtensions(template)
2544         if err != nil {
2545                 return nil, err
2546         }
2547
2548         // Make a copy of template.Attributes because we may alter it below.
2549         attributes := make([]pkix.AttributeTypeAndValueSET, 0, len(template.Attributes))
2550         for _, attr := range template.Attributes {
2551                 values := make([][]pkix.AttributeTypeAndValue, len(attr.Value))
2552                 copy(values, attr.Value)
2553                 attributes = append(attributes, pkix.AttributeTypeAndValueSET{
2554                         Type:  attr.Type,
2555                         Value: values,
2556                 })
2557         }
2558
2559         extensionsAppended := false
2560         if len(extensions) > 0 {
2561                 // Append the extensions to an existing attribute if possible.
2562                 for _, atvSet := range attributes {
2563                         if !atvSet.Type.Equal(oidExtensionRequest) || len(atvSet.Value) == 0 {
2564                                 continue
2565                         }
2566
2567                         // specifiedExtensions contains all the extensions that we
2568                         // found specified via template.Attributes.
2569                         specifiedExtensions := make(map[string]bool)
2570
2571                         for _, atvs := range atvSet.Value {
2572                                 for _, atv := range atvs {
2573                                         specifiedExtensions[atv.Type.String()] = true
2574                                 }
2575                         }
2576
2577                         newValue := make([]pkix.AttributeTypeAndValue, 0, len(atvSet.Value[0])+len(extensions))
2578                         newValue = append(newValue, atvSet.Value[0]...)
2579
2580                         for _, e := range extensions {
2581                                 if specifiedExtensions[e.Id.String()] {
2582                                         // Attributes already contained a value for
2583                                         // this extension and it takes priority.
2584                                         continue
2585                                 }
2586
2587                                 newValue = append(newValue, pkix.AttributeTypeAndValue{
2588                                         // There is no place for the critical
2589                                         // flag in an AttributeTypeAndValue.
2590                                         Type:  e.Id,
2591                                         Value: e.Value,
2592                                 })
2593                         }
2594
2595                         atvSet.Value[0] = newValue
2596                         extensionsAppended = true
2597                         break
2598                 }
2599         }
2600
2601         rawAttributes, err := newRawAttributes(attributes)
2602         if err != nil {
2603                 return
2604         }
2605
2606         // If not included in attributes, add a new attribute for the
2607         // extensions.
2608         if len(extensions) > 0 && !extensionsAppended {
2609                 attr := struct {
2610                         Type  asn1.ObjectIdentifier
2611                         Value [][]pkix.Extension `asn1:"set"`
2612                 }{
2613                         Type:  oidExtensionRequest,
2614                         Value: [][]pkix.Extension{extensions},
2615                 }
2616
2617                 b, err := asn1.Marshal(attr)
2618                 if err != nil {
2619                         return nil, errors.New("x509: failed to serialise extensions attribute: " + err.Error())
2620                 }
2621
2622                 var rawValue asn1.RawValue
2623                 if _, err := asn1.Unmarshal(b, &rawValue); err != nil {
2624                         return nil, err
2625                 }
2626
2627                 rawAttributes = append(rawAttributes, rawValue)
2628         }
2629
2630         asn1Subject := template.RawSubject
2631         if len(asn1Subject) == 0 {
2632                 asn1Subject, err = asn1.Marshal(template.Subject.ToRDNSequence())
2633                 if err != nil {
2634                         return nil, err
2635                 }
2636         }
2637
2638         tbsCSR := tbsCertificateRequest{
2639                 Version: 0, // PKCS #10, RFC 2986
2640                 Subject: asn1.RawValue{FullBytes: asn1Subject},
2641                 PublicKey: publicKeyInfo{
2642                         Algorithm: publicKeyAlgorithm,
2643                         PublicKey: asn1.BitString{
2644                                 Bytes:     publicKeyBytes,
2645                                 BitLength: len(publicKeyBytes) * 8,
2646                         },
2647                 },
2648                 RawAttributes: rawAttributes,
2649         }
2650
2651         tbsCSRContents, err := asn1.Marshal(tbsCSR)
2652         if err != nil {
2653                 return
2654         }
2655         tbsCSR.Raw = tbsCSRContents
2656
2657         signed := tbsCSRContents
2658         if hashFunc != 0 {
2659                 h := hashFunc.New()
2660                 h.Write(signed)
2661                 signed = h.Sum(nil)
2662         }
2663
2664         var signature []byte
2665         signature, err = key.Sign(rand, signed, hashFunc)
2666         if err != nil {
2667                 return
2668         }
2669
2670         return asn1.Marshal(certificateRequest{
2671                 TBSCSR:             tbsCSR,
2672                 SignatureAlgorithm: sigAlgo,
2673                 SignatureValue: asn1.BitString{
2674                         Bytes:     signature,
2675                         BitLength: len(signature) * 8,
2676                 },
2677         })
2678 }
2679
2680 // ParseCertificateRequest parses a single certificate request from the
2681 // given ASN.1 DER data.
2682 func ParseCertificateRequest(asn1Data []byte) (*CertificateRequest, error) {
2683         var csr certificateRequest
2684
2685         rest, err := asn1.Unmarshal(asn1Data, &csr)
2686         if err != nil {
2687                 return nil, err
2688         } else if len(rest) != 0 {
2689                 return nil, asn1.SyntaxError{Msg: "trailing data"}
2690         }
2691
2692         return parseCertificateRequest(&csr)
2693 }
2694
2695 func parseCertificateRequest(in *certificateRequest) (*CertificateRequest, error) {
2696         out := &CertificateRequest{
2697                 Raw:                      in.Raw,
2698                 RawTBSCertificateRequest: in.TBSCSR.Raw,
2699                 RawSubjectPublicKeyInfo:  in.TBSCSR.PublicKey.Raw,
2700                 RawSubject:               in.TBSCSR.Subject.FullBytes,
2701
2702                 Signature:          in.SignatureValue.RightAlign(),
2703                 SignatureAlgorithm: getSignatureAlgorithmFromAI(in.SignatureAlgorithm),
2704
2705                 PublicKeyAlgorithm: getPublicKeyAlgorithmFromOID(in.TBSCSR.PublicKey.Algorithm.Algorithm),
2706
2707                 Version:    in.TBSCSR.Version,
2708                 Attributes: parseRawAttributes(in.TBSCSR.RawAttributes),
2709         }
2710
2711         var err error
2712         out.PublicKey, err = parsePublicKey(out.PublicKeyAlgorithm, &in.TBSCSR.PublicKey)
2713         if err != nil {
2714                 return nil, err
2715         }
2716
2717         var subject pkix.RDNSequence
2718         if rest, err := asn1.Unmarshal(in.TBSCSR.Subject.FullBytes, &subject); err != nil {
2719                 return nil, err
2720         } else if len(rest) != 0 {
2721                 return nil, errors.New("x509: trailing data after X.509 Subject")
2722         }
2723
2724         out.Subject.FillFromRDNSequence(&subject)
2725
2726         if out.Extensions, err = parseCSRExtensions(in.TBSCSR.RawAttributes); err != nil {
2727                 return nil, err
2728         }
2729
2730         for _, extension := range out.Extensions {
2731                 switch {
2732                 case extension.Id.Equal(oidExtensionSubjectAltName):
2733                         out.DNSNames, out.EmailAddresses, out.IPAddresses, out.URIs, err = parseSANExtension(extension.Value)
2734                         if err != nil {
2735                                 return nil, err
2736                         }
2737                 case extension.Id.Equal(oidExtensionKeyUsage):
2738                         out.KeyUsage, err = parseKeyUsageExtension(extension.Value)
2739                         if err != nil {
2740                                 return nil, err
2741                         }
2742                 }
2743         }
2744
2745         return out, nil
2746 }
2747
2748 // CheckSignature reports whether the signature on c is valid.
2749 func (c *CertificateRequest) CheckSignature() error {
2750         return checkSignature(c.SignatureAlgorithm, c.RawTBSCertificateRequest, c.Signature, c.PublicKey)
2751 }
2752
2753 // RevocationList contains the fields used to create an X.509 v2 Certificate
2754 // Revocation list with CreateRevocationList.
2755 type RevocationList struct {
2756         // SignatureAlgorithm is used to determine the signature algorithm to be
2757         // used when signing the CRL. If 0 the default algorithm for the signing
2758         // key will be used.
2759         SignatureAlgorithm SignatureAlgorithm
2760
2761         // RevokedCertificates is used to populate the revokedCertificates
2762         // sequence in the CRL, it may be empty. RevokedCertificates may be nil,
2763         // in which case an empty CRL will be created.
2764         RevokedCertificates []pkix.RevokedCertificate
2765
2766         // Number is used to populate the X.509 v2 cRLNumber extension in the CRL,
2767         // which should be a monotonically increasing sequence number for a given
2768         // CRL scope and CRL issuer.
2769         Number *big.Int
2770         // ThisUpdate is used to populate the thisUpdate field in the CRL, which
2771         // indicates the issuance date of the CRL.
2772         ThisUpdate time.Time
2773         // NextUpdate is used to populate the nextUpdate field in the CRL, which
2774         // indicates the date by which the next CRL will be issued. NextUpdate
2775         // must be greater than ThisUpdate.
2776         NextUpdate time.Time
2777         // ExtraExtensions contains any additional extensions to add directly to
2778         // the CRL.
2779         ExtraExtensions []pkix.Extension
2780 }
2781
2782 // CreateRevocationList creates a new X.509 v2 Certificate Revocation List,
2783 // according to RFC 5280, based on template.
2784 //
2785 // The CRL is signed by priv which should be the private key associated with
2786 // the public key in the issuer certificate.
2787 //
2788 // The issuer may not be nil, and the crlSign bit must be set in KeyUsage in
2789 // order to use it as a CRL issuer.
2790 //
2791 // The issuer distinguished name CRL field and authority key identifier
2792 // extension are populated using the issuer certificate. issuer must have
2793 // SubjectKeyId set.
2794 func CreateRevocationList(rand io.Reader, template *RevocationList, issuer *Certificate, priv crypto.Signer) ([]byte, error) {
2795         if template == nil {
2796                 return nil, errors.New("x509: template can not be nil")
2797         }
2798         if issuer == nil {
2799                 return nil, errors.New("x509: issuer can not be nil")
2800         }
2801         if (issuer.KeyUsage & KeyUsageCRLSign) == 0 {
2802                 return nil, errors.New("x509: issuer must have the crlSign key usage bit set")
2803         }
2804         if len(issuer.SubjectKeyId) == 0 {
2805                 return nil, errors.New("x509: issuer certificate doesn't contain a subject key identifier")
2806         }
2807         if template.NextUpdate.Before(template.ThisUpdate) {
2808                 return nil, errors.New("x509: template.ThisUpdate is after template.NextUpdate")
2809         }
2810         if template.Number == nil {
2811                 return nil, errors.New("x509: template contains nil Number field")
2812         }
2813
2814         hashFunc, signatureAlgorithm, err := signingParamsForPublicKey(priv.Public(), template.SignatureAlgorithm)
2815         if err != nil {
2816                 return nil, err
2817         }
2818
2819         // Force revocation times to UTC per RFC 5280.
2820         revokedCertsUTC := make([]pkix.RevokedCertificate, len(template.RevokedCertificates))
2821         for i, rc := range template.RevokedCertificates {
2822                 rc.RevocationTime = rc.RevocationTime.UTC()
2823                 revokedCertsUTC[i] = rc
2824         }
2825
2826         aki, err := asn1.Marshal(authKeyId{Id: issuer.SubjectKeyId})
2827         if err != nil {
2828                 return nil, err
2829         }
2830         crlNum, err := asn1.Marshal(template.Number)
2831         if err != nil {
2832                 return nil, err
2833         }
2834
2835         tbsCertList := pkix.TBSCertificateList{
2836                 Version:    1, // v2
2837                 Signature:  signatureAlgorithm,
2838                 Issuer:     issuer.Subject.ToRDNSequence(),
2839                 ThisUpdate: template.ThisUpdate.UTC(),
2840                 NextUpdate: template.NextUpdate.UTC(),
2841                 Extensions: []pkix.Extension{
2842                         {
2843                                 Id:    oidExtensionAuthorityKeyId,
2844                                 Value: aki,
2845                         },
2846                         {
2847                                 Id:    oidExtensionCRLNumber,
2848                                 Value: crlNum,
2849                         },
2850                 },
2851         }
2852         if len(revokedCertsUTC) > 0 {
2853                 tbsCertList.RevokedCertificates = revokedCertsUTC
2854         }
2855
2856         if len(template.ExtraExtensions) > 0 {
2857                 tbsCertList.Extensions = append(tbsCertList.Extensions, template.ExtraExtensions...)
2858         }
2859
2860         tbsCertListContents, err := asn1.Marshal(tbsCertList)
2861         if err != nil {
2862                 return nil, err
2863         }
2864
2865         input := tbsCertListContents
2866         if hashFunc != 0 {
2867                 h := hashFunc.New()
2868                 h.Write(tbsCertListContents)
2869                 input = h.Sum(nil)
2870         }
2871         var signerOpts crypto.SignerOpts = hashFunc
2872         if template.SignatureAlgorithm.isRSAPSS() {
2873                 signerOpts = &rsa.PSSOptions{
2874                         SaltLength: rsa.PSSSaltLengthEqualsHash,
2875                         Hash:       hashFunc,
2876                 }
2877         }
2878
2879         signature, err := priv.Sign(rand, input, signerOpts)
2880         if err != nil {
2881                 return nil, err
2882         }
2883
2884         return asn1.Marshal(pkix.CertificateList{
2885                 TBSCertList:        tbsCertList,
2886                 SignatureAlgorithm: signatureAlgorithm,
2887                 SignatureValue:     asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
2888         })
2889 }