crypto/x509: reject duplicate extensions

[gostls13.git] / src / crypto / x509 / x509.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package x509 parses X.509-encoded keys and certificates.
package x509

import (
        "bytes"
        "crypto"
        "crypto/ecdsa"
        "crypto/ed25519"
        "crypto/elliptic"
        "crypto/rsa"
        "crypto/sha1"
        "crypto/x509/pkix"
        "encoding/asn1"
        "encoding/pem"
        "errors"
        "fmt"
        "internal/godebug"
        "io"
        "math/big"
        "net"
        "net/url"
        "strconv"
        "time"
        "unicode"

        // Explicitly import these for their crypto.RegisterHash init side-effects.
        // Keep these as blank imports, even if they're imported above.
        _ "crypto/sha1"
        _ "crypto/sha256"
        _ "crypto/sha512"

        "golang.org/x/crypto/cryptobyte"
        cryptobyte_asn1 "golang.org/x/crypto/cryptobyte/asn1"
)

// pkixPublicKey reflects a PKIX public key structure. See SubjectPublicKeyInfo
// in RFC 3280.
type pkixPublicKey struct {
        Algo      pkix.AlgorithmIdentifier
        BitString asn1.BitString
}

// ParsePKIXPublicKey parses a public key in PKIX, ASN.1 DER form.
// The encoded public key is a SubjectPublicKeyInfo structure
// (see RFC 5280, Section 4.1).
//
// It returns a *rsa.PublicKey, *dsa.PublicKey, *ecdsa.PublicKey, or
// ed25519.PublicKey. More types might be supported in the future.
//
// This kind of key is commonly encoded in PEM blocks of type "PUBLIC KEY".
func ParsePKIXPublicKey(derBytes []byte) (pub any, err error) {
        var pki publicKeyInfo
        if rest, err := asn1.Unmarshal(derBytes, &pki); err != nil {
                if _, err := asn1.Unmarshal(derBytes, &pkcs1PublicKey{}); err == nil {
                        return nil, errors.New("x509: failed to parse public key (use ParsePKCS1PublicKey instead for this key format)")
                }
                return nil, err
        } else if len(rest) != 0 {
                return nil, errors.New("x509: trailing data after ASN.1 of public-key")
        }
        algo := getPublicKeyAlgorithmFromOID(pki.Algorithm.Algorithm)
        if algo == UnknownPublicKeyAlgorithm {
                return nil, errors.New("x509: unknown public key algorithm")
        }
        return parsePublicKey(algo, &pki)
}

func marshalPublicKey(pub any) (publicKeyBytes []byte, publicKeyAlgorithm pkix.AlgorithmIdentifier, err error) {
        switch pub := pub.(type) {
        case *rsa.PublicKey:
                publicKeyBytes, err = asn1.Marshal(pkcs1PublicKey{
                        N: pub.N,
                        E: pub.E,
                })
                if err != nil {
                        return nil, pkix.AlgorithmIdentifier{}, err
                }
                publicKeyAlgorithm.Algorithm = oidPublicKeyRSA
                // This is a NULL parameters value which is required by
                // RFC 3279, Section 2.3.1.
                publicKeyAlgorithm.Parameters = asn1.NullRawValue
        case *ecdsa.PublicKey:
                publicKeyBytes = elliptic.Marshal(pub.Curve, pub.X, pub.Y)
                oid, ok := oidFromNamedCurve(pub.Curve)
                if !ok {
                        return nil, pkix.AlgorithmIdentifier{}, errors.New("x509: unsupported elliptic curve")
                }
                publicKeyAlgorithm.Algorithm = oidPublicKeyECDSA
                var paramBytes []byte
                paramBytes, err = asn1.Marshal(oid)
                if err != nil {
                        return
                }
                publicKeyAlgorithm.Parameters.FullBytes = paramBytes
        case ed25519.PublicKey:
                publicKeyBytes = pub
                publicKeyAlgorithm.Algorithm = oidPublicKeyEd25519
        default:
                return nil, pkix.AlgorithmIdentifier{}, fmt.Errorf("x509: unsupported public key type: %T", pub)
        }

        return publicKeyBytes, publicKeyAlgorithm, nil
}

// MarshalPKIXPublicKey converts a public key to PKIX, ASN.1 DER form.
// The encoded public key is a SubjectPublicKeyInfo structure
// (see RFC 5280, Section 4.1).
//
// The following key types are currently supported: *rsa.PublicKey, *ecdsa.PublicKey
// and ed25519.PublicKey. Unsupported key types result in an error.
//
// This kind of key is commonly encoded in PEM blocks of type "PUBLIC KEY".
func MarshalPKIXPublicKey(pub any) ([]byte, error) {
        var publicKeyBytes []byte
        var publicKeyAlgorithm pkix.AlgorithmIdentifier
        var err error

        if publicKeyBytes, publicKeyAlgorithm, err = marshalPublicKey(pub); err != nil {
                return nil, err
        }

        pkix := pkixPublicKey{
                Algo: publicKeyAlgorithm,
                BitString: asn1.BitString{
                        Bytes:     publicKeyBytes,
                        BitLength: 8 * len(publicKeyBytes),
                },
        }

        ret, _ := asn1.Marshal(pkix)
        return ret, nil
}

// These structures reflect the ASN.1 structure of X.509 certificates.:

type certificate struct {
        Raw                asn1.RawContent
        TBSCertificate     tbsCertificate
        SignatureAlgorithm pkix.AlgorithmIdentifier
        SignatureValue     asn1.BitString
}

type tbsCertificate struct {
        Raw                asn1.RawContent
        Version            int `asn1:"optional,explicit,default:0,tag:0"`
        SerialNumber       *big.Int
        SignatureAlgorithm pkix.AlgorithmIdentifier
        Issuer             asn1.RawValue
        Validity           validity
        Subject            asn1.RawValue
        PublicKey          publicKeyInfo
        UniqueId           asn1.BitString   `asn1:"optional,tag:1"`
        SubjectUniqueId    asn1.BitString   `asn1:"optional,tag:2"`
        Extensions         []pkix.Extension `asn1:"omitempty,optional,explicit,tag:3"`
}

type dsaAlgorithmParameters struct {
        P, Q, G *big.Int
}

type validity struct {
        NotBefore, NotAfter time.Time
}

type publicKeyInfo struct {
        Raw       asn1.RawContent
        Algorithm pkix.AlgorithmIdentifier
        PublicKey asn1.BitString
}

// RFC 5280,  4.2.1.1
type authKeyId struct {
        Id []byte `asn1:"optional,tag:0"`
}

type SignatureAlgorithm int

const (
        UnknownSignatureAlgorithm SignatureAlgorithm = iota

        MD2WithRSA  // Unsupported.
        MD5WithRSA  // Only supported for signing, not verification.
        SHA1WithRSA // Only supported for signing, and verification of CRLs, CSRs, and OCSP responses.
        SHA256WithRSA
        SHA384WithRSA
        SHA512WithRSA
        DSAWithSHA1   // Unsupported.
        DSAWithSHA256 // Unsupported.
        ECDSAWithSHA1 // Only supported for signing, and verification of CRLs, CSRs, and OCSP responses.
        ECDSAWithSHA256
        ECDSAWithSHA384
        ECDSAWithSHA512
        SHA256WithRSAPSS
        SHA384WithRSAPSS
        SHA512WithRSAPSS
        PureEd25519
)

func (algo SignatureAlgorithm) isRSAPSS() bool {
        switch algo {
        case SHA256WithRSAPSS, SHA384WithRSAPSS, SHA512WithRSAPSS:
                return true
        default:
                return false
        }
}

func (algo SignatureAlgorithm) String() string {
        for _, details := range signatureAlgorithmDetails {
                if details.algo == algo {
                        return details.name
                }
        }
        return strconv.Itoa(int(algo))
}

type PublicKeyAlgorithm int

const (
        UnknownPublicKeyAlgorithm PublicKeyAlgorithm = iota
        RSA
        DSA // Unsupported.
        ECDSA
        Ed25519
)

var publicKeyAlgoName = [...]string{
        RSA:     "RSA",
        DSA:     "DSA",
        ECDSA:   "ECDSA",
        Ed25519: "Ed25519",
}

func (algo PublicKeyAlgorithm) String() string {
        if 0 < algo && int(algo) < len(publicKeyAlgoName) {
                return publicKeyAlgoName[algo]
        }
        return strconv.Itoa(int(algo))
}

// OIDs for signature algorithms
//
//      pkcs-1 OBJECT IDENTIFIER ::= {
//              iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 1 }
//
// RFC 3279 2.2.1 RSA Signature Algorithms
//
//      md2WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 2 }
//
//      md5WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 4 }
//
//      sha-1WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 5 }
//
//      dsaWithSha1 OBJECT IDENTIFIER ::= {
//              iso(1) member-body(2) us(840) x9-57(10040) x9cm(4) 3 }
//
// RFC 3279 2.2.3 ECDSA Signature Algorithm
//
//      ecdsa-with-SHA1 OBJECT IDENTIFIER ::= {
//              iso(1) member-body(2) us(840) ansi-x962(10045)
//              signatures(4) ecdsa-with-SHA1(1)}
//
// RFC 4055 5 PKCS #1 Version 1.5
//
//      sha256WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 11 }
//
//      sha384WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 12 }
//
//      sha512WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 13 }
//
// RFC 5758 3.1 DSA Signature Algorithms
//
//      dsaWithSha256 OBJECT IDENTIFIER ::= {
//              joint-iso-ccitt(2) country(16) us(840) organization(1) gov(101)
//              csor(3) algorithms(4) id-dsa-with-sha2(3) 2}
//
// RFC 5758 3.2 ECDSA Signature Algorithm
//
//      ecdsa-with-SHA256 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
//              us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 2 }
//
//      ecdsa-with-SHA384 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
//              us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 3 }
//
//      ecdsa-with-SHA512 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
//              us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 4 }
//
// RFC 8410 3 Curve25519 and Curve448 Algorithm Identifiers
//
//      id-Ed25519   OBJECT IDENTIFIER ::= { 1 3 101 112 }
var (
        oidSignatureMD2WithRSA      = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 2}
        oidSignatureMD5WithRSA      = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 4}
        oidSignatureSHA1WithRSA     = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 5}
        oidSignatureSHA256WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 11}
        oidSignatureSHA384WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 12}
        oidSignatureSHA512WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 13}
        oidSignatureRSAPSS          = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 10}
        oidSignatureDSAWithSHA1     = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 3}
        oidSignatureDSAWithSHA256   = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 2}
        oidSignatureECDSAWithSHA1   = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 1}
        oidSignatureECDSAWithSHA256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 2}
        oidSignatureECDSAWithSHA384 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 3}
        oidSignatureECDSAWithSHA512 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 4}
        oidSignatureEd25519         = asn1.ObjectIdentifier{1, 3, 101, 112}

        oidSHA256 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 1}
        oidSHA384 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 2}
        oidSHA512 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 3}

        oidMGF1 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 8}

        // oidISOSignatureSHA1WithRSA means the same as oidSignatureSHA1WithRSA
        // but it's specified by ISO. Microsoft's makecert.exe has been known
        // to produce certificates with this OID.
        oidISOSignatureSHA1WithRSA = asn1.ObjectIdentifier{1, 3, 14, 3, 2, 29}
)

var signatureAlgorithmDetails = []struct {
        algo       SignatureAlgorithm
        name       string
        oid        asn1.ObjectIdentifier
        pubKeyAlgo PublicKeyAlgorithm
        hash       crypto.Hash
}{
        {MD2WithRSA, "MD2-RSA", oidSignatureMD2WithRSA, RSA, crypto.Hash(0) /* no value for MD2 */},
        {MD5WithRSA, "MD5-RSA", oidSignatureMD5WithRSA, RSA, crypto.MD5},
        {SHA1WithRSA, "SHA1-RSA", oidSignatureSHA1WithRSA, RSA, crypto.SHA1},
        {SHA1WithRSA, "SHA1-RSA", oidISOSignatureSHA1WithRSA, RSA, crypto.SHA1},
        {SHA256WithRSA, "SHA256-RSA", oidSignatureSHA256WithRSA, RSA, crypto.SHA256},
        {SHA384WithRSA, "SHA384-RSA", oidSignatureSHA384WithRSA, RSA, crypto.SHA384},
        {SHA512WithRSA, "SHA512-RSA", oidSignatureSHA512WithRSA, RSA, crypto.SHA512},
        {SHA256WithRSAPSS, "SHA256-RSAPSS", oidSignatureRSAPSS, RSA, crypto.SHA256},
        {SHA384WithRSAPSS, "SHA384-RSAPSS", oidSignatureRSAPSS, RSA, crypto.SHA384},
        {SHA512WithRSAPSS, "SHA512-RSAPSS", oidSignatureRSAPSS, RSA, crypto.SHA512},
        {DSAWithSHA1, "DSA-SHA1", oidSignatureDSAWithSHA1, DSA, crypto.SHA1},
        {DSAWithSHA256, "DSA-SHA256", oidSignatureDSAWithSHA256, DSA, crypto.SHA256},
        {ECDSAWithSHA1, "ECDSA-SHA1", oidSignatureECDSAWithSHA1, ECDSA, crypto.SHA1},
        {ECDSAWithSHA256, "ECDSA-SHA256", oidSignatureECDSAWithSHA256, ECDSA, crypto.SHA256},
        {ECDSAWithSHA384, "ECDSA-SHA384", oidSignatureECDSAWithSHA384, ECDSA, crypto.SHA384},
        {ECDSAWithSHA512, "ECDSA-SHA512", oidSignatureECDSAWithSHA512, ECDSA, crypto.SHA512},
        {PureEd25519, "Ed25519", oidSignatureEd25519, Ed25519, crypto.Hash(0) /* no pre-hashing */},
}

// hashToPSSParameters contains the DER encoded RSA PSS parameters for the
// SHA256, SHA384, and SHA512 hashes as defined in RFC 3447, Appendix A.2.3.
// The parameters contain the following values:
//   - hashAlgorithm contains the associated hash identifier with NULL parameters
//   - maskGenAlgorithm always contains the default mgf1SHA1 identifier
//   - saltLength contains the length of the associated hash
//   - trailerField always contains the default trailerFieldBC value
var hashToPSSParameters = map[crypto.Hash]asn1.RawValue{
        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}},
        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}},
        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}},
}

// pssParameters reflects the parameters in an AlgorithmIdentifier that
// specifies RSA PSS. See RFC 3447, Appendix A.2.3.
type pssParameters struct {
        // The following three fields are not marked as
        // optional because the default values specify SHA-1,
        // which is no longer suitable for use in signatures.
        Hash         pkix.AlgorithmIdentifier `asn1:"explicit,tag:0"`
        MGF          pkix.AlgorithmIdentifier `asn1:"explicit,tag:1"`
        SaltLength   int                      `asn1:"explicit,tag:2"`
        TrailerField int                      `asn1:"optional,explicit,tag:3,default:1"`
}

func getSignatureAlgorithmFromAI(ai pkix.AlgorithmIdentifier) SignatureAlgorithm {
        if ai.Algorithm.Equal(oidSignatureEd25519) {
                // RFC 8410, Section 3
                // > For all of the OIDs, the parameters MUST be absent.
                if len(ai.Parameters.FullBytes) != 0 {
                        return UnknownSignatureAlgorithm
                }
        }

        if !ai.Algorithm.Equal(oidSignatureRSAPSS) {
                for _, details := range signatureAlgorithmDetails {
                        if ai.Algorithm.Equal(details.oid) {
                                return details.algo
                        }
                }
                return UnknownSignatureAlgorithm
        }

        // RSA PSS is special because it encodes important parameters
        // in the Parameters.

        var params pssParameters
        if _, err := asn1.Unmarshal(ai.Parameters.FullBytes, &params); err != nil {
                return UnknownSignatureAlgorithm
        }

        var mgf1HashFunc pkix.AlgorithmIdentifier
        if _, err := asn1.Unmarshal(params.MGF.Parameters.FullBytes, &mgf1HashFunc); err != nil {
                return UnknownSignatureAlgorithm
        }

        // PSS is greatly overburdened with options. This code forces them into
        // three buckets by requiring that the MGF1 hash function always match the
        // message hash function (as recommended in RFC 3447, Section 8.1), that the
        // salt length matches the hash length, and that the trailer field has the
        // default value.
        if (len(params.Hash.Parameters.FullBytes) != 0 && !bytes.Equal(params.Hash.Parameters.FullBytes, asn1.NullBytes)) ||
                !params.MGF.Algorithm.Equal(oidMGF1) ||
                !mgf1HashFunc.Algorithm.Equal(params.Hash.Algorithm) ||
                (len(mgf1HashFunc.Parameters.FullBytes) != 0 && !bytes.Equal(mgf1HashFunc.Parameters.FullBytes, asn1.NullBytes)) ||
                params.TrailerField != 1 {
                return UnknownSignatureAlgorithm
        }

        switch {
        case params.Hash.Algorithm.Equal(oidSHA256) && params.SaltLength == 32:
                return SHA256WithRSAPSS
        case params.Hash.Algorithm.Equal(oidSHA384) && params.SaltLength == 48:
                return SHA384WithRSAPSS
        case params.Hash.Algorithm.Equal(oidSHA512) && params.SaltLength == 64:
                return SHA512WithRSAPSS
        }

        return UnknownSignatureAlgorithm
}

// RFC 3279, 2.3 Public Key Algorithms
//
//      pkcs-1 OBJECT IDENTIFIER ::== { iso(1) member-body(2) us(840)
//              rsadsi(113549) pkcs(1) 1 }
//
// rsaEncryption OBJECT IDENTIFIER ::== { pkcs1-1 1 }
//
//      id-dsa OBJECT IDENTIFIER ::== { iso(1) member-body(2) us(840)
//              x9-57(10040) x9cm(4) 1 }
//
// RFC 5480, 2.1.1 Unrestricted Algorithm Identifier and Parameters
//
//      id-ecPublicKey OBJECT IDENTIFIER ::= {
//              iso(1) member-body(2) us(840) ansi-X9-62(10045) keyType(2) 1 }
var (
        oidPublicKeyRSA     = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}
        oidPublicKeyDSA     = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 1}
        oidPublicKeyECDSA   = asn1.ObjectIdentifier{1, 2, 840, 10045, 2, 1}
        oidPublicKeyEd25519 = oidSignatureEd25519
)

func getPublicKeyAlgorithmFromOID(oid asn1.ObjectIdentifier) PublicKeyAlgorithm {
        switch {
        case oid.Equal(oidPublicKeyRSA):
                return RSA
        case oid.Equal(oidPublicKeyDSA):
                return DSA
        case oid.Equal(oidPublicKeyECDSA):
                return ECDSA
        case oid.Equal(oidPublicKeyEd25519):
                return Ed25519
        }
        return UnknownPublicKeyAlgorithm
}

// RFC 5480, 2.1.1.1. Named Curve
//
//      secp224r1 OBJECT IDENTIFIER ::= {
//        iso(1) identified-organization(3) certicom(132) curve(0) 33 }
//
//      secp256r1 OBJECT IDENTIFIER ::= {
//        iso(1) member-body(2) us(840) ansi-X9-62(10045) curves(3)
//        prime(1) 7 }
//
//      secp384r1 OBJECT IDENTIFIER ::= {
//        iso(1) identified-organization(3) certicom(132) curve(0) 34 }
//
//      secp521r1 OBJECT IDENTIFIER ::= {
//        iso(1) identified-organization(3) certicom(132) curve(0) 35 }
//
// NB: secp256r1 is equivalent to prime256v1
var (
        oidNamedCurveP224 = asn1.ObjectIdentifier{1, 3, 132, 0, 33}
        oidNamedCurveP256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 3, 1, 7}
        oidNamedCurveP384 = asn1.ObjectIdentifier{1, 3, 132, 0, 34}
        oidNamedCurveP521 = asn1.ObjectIdentifier{1, 3, 132, 0, 35}
)

func namedCurveFromOID(oid asn1.ObjectIdentifier) elliptic.Curve {
        switch {
        case oid.Equal(oidNamedCurveP224):
                return elliptic.P224()
        case oid.Equal(oidNamedCurveP256):
                return elliptic.P256()
        case oid.Equal(oidNamedCurveP384):
                return elliptic.P384()
        case oid.Equal(oidNamedCurveP521):
                return elliptic.P521()
        }
        return nil
}

func oidFromNamedCurve(curve elliptic.Curve) (asn1.ObjectIdentifier, bool) {
        switch curve {
        case elliptic.P224():
                return oidNamedCurveP224, true
        case elliptic.P256():
                return oidNamedCurveP256, true
        case elliptic.P384():
                return oidNamedCurveP384, true
        case elliptic.P521():
                return oidNamedCurveP521, true
        }

        return nil, false
}

// KeyUsage represents the set of actions that are valid for a given key. It's
// a bitmap of the KeyUsage* constants.
type KeyUsage int

const (
        KeyUsageDigitalSignature KeyUsage = 1 << iota
        KeyUsageContentCommitment
        KeyUsageKeyEncipherment
        KeyUsageDataEncipherment
        KeyUsageKeyAgreement
        KeyUsageCertSign
        KeyUsageCRLSign
        KeyUsageEncipherOnly
        KeyUsageDecipherOnly
)

// RFC 5280, 4.2.1.12  Extended Key Usage
//
//      anyExtendedKeyUsage OBJECT IDENTIFIER ::= { id-ce-extKeyUsage 0 }
//
//      id-kp OBJECT IDENTIFIER ::= { id-pkix 3 }
//
//      id-kp-serverAuth             OBJECT IDENTIFIER ::= { id-kp 1 }
//      id-kp-clientAuth             OBJECT IDENTIFIER ::= { id-kp 2 }
//      id-kp-codeSigning            OBJECT IDENTIFIER ::= { id-kp 3 }
//      id-kp-emailProtection        OBJECT IDENTIFIER ::= { id-kp 4 }
//      id-kp-timeStamping           OBJECT IDENTIFIER ::= { id-kp 8 }
//      id-kp-OCSPSigning            OBJECT IDENTIFIER ::= { id-kp 9 }
var (
        oidExtKeyUsageAny                            = asn1.ObjectIdentifier{2, 5, 29, 37, 0}
        oidExtKeyUsageServerAuth                     = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 1}
        oidExtKeyUsageClientAuth                     = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 2}
        oidExtKeyUsageCodeSigning                    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 3}
        oidExtKeyUsageEmailProtection                = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 4}
        oidExtKeyUsageIPSECEndSystem                 = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 5}
        oidExtKeyUsageIPSECTunnel                    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 6}
        oidExtKeyUsageIPSECUser                      = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 7}
        oidExtKeyUsageTimeStamping                   = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 8}
        oidExtKeyUsageOCSPSigning                    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 9}
        oidExtKeyUsageMicrosoftServerGatedCrypto     = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 10, 3, 3}
        oidExtKeyUsageNetscapeServerGatedCrypto      = asn1.ObjectIdentifier{2, 16, 840, 1, 113730, 4, 1}
        oidExtKeyUsageMicrosoftCommercialCodeSigning = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 2, 1, 22}
        oidExtKeyUsageMicrosoftKernelCodeSigning     = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 61, 1, 1}
)

// ExtKeyUsage represents an extended set of actions that are valid for a given key.
// Each of the ExtKeyUsage* constants define a unique action.
type ExtKeyUsage int

const (
        ExtKeyUsageAny ExtKeyUsage = iota
        ExtKeyUsageServerAuth
        ExtKeyUsageClientAuth
        ExtKeyUsageCodeSigning
        ExtKeyUsageEmailProtection
        ExtKeyUsageIPSECEndSystem
        ExtKeyUsageIPSECTunnel
        ExtKeyUsageIPSECUser
        ExtKeyUsageTimeStamping
        ExtKeyUsageOCSPSigning
        ExtKeyUsageMicrosoftServerGatedCrypto
        ExtKeyUsageNetscapeServerGatedCrypto
        ExtKeyUsageMicrosoftCommercialCodeSigning
        ExtKeyUsageMicrosoftKernelCodeSigning
)

// extKeyUsageOIDs contains the mapping between an ExtKeyUsage and its OID.
var extKeyUsageOIDs = []struct {
        extKeyUsage ExtKeyUsage
        oid         asn1.ObjectIdentifier
}{
        {ExtKeyUsageAny, oidExtKeyUsageAny},
        {ExtKeyUsageServerAuth, oidExtKeyUsageServerAuth},
        {ExtKeyUsageClientAuth, oidExtKeyUsageClientAuth},
        {ExtKeyUsageCodeSigning, oidExtKeyUsageCodeSigning},
        {ExtKeyUsageEmailProtection, oidExtKeyUsageEmailProtection},
        {ExtKeyUsageIPSECEndSystem, oidExtKeyUsageIPSECEndSystem},
        {ExtKeyUsageIPSECTunnel, oidExtKeyUsageIPSECTunnel},
        {ExtKeyUsageIPSECUser, oidExtKeyUsageIPSECUser},
        {ExtKeyUsageTimeStamping, oidExtKeyUsageTimeStamping},
        {ExtKeyUsageOCSPSigning, oidExtKeyUsageOCSPSigning},
        {ExtKeyUsageMicrosoftServerGatedCrypto, oidExtKeyUsageMicrosoftServerGatedCrypto},
        {ExtKeyUsageNetscapeServerGatedCrypto, oidExtKeyUsageNetscapeServerGatedCrypto},
        {ExtKeyUsageMicrosoftCommercialCodeSigning, oidExtKeyUsageMicrosoftCommercialCodeSigning},
        {ExtKeyUsageMicrosoftKernelCodeSigning, oidExtKeyUsageMicrosoftKernelCodeSigning},
}

func extKeyUsageFromOID(oid asn1.ObjectIdentifier) (eku ExtKeyUsage, ok bool) {
        for _, pair := range extKeyUsageOIDs {
                if oid.Equal(pair.oid) {
                        return pair.extKeyUsage, true
                }
        }
        return
}

func oidFromExtKeyUsage(eku ExtKeyUsage) (oid asn1.ObjectIdentifier, ok bool) {
        for _, pair := range extKeyUsageOIDs {
                if eku == pair.extKeyUsage {
                        return pair.oid, true
                }
        }
        return
}

// A Certificate represents an X.509 certificate.
type Certificate struct {
        Raw                     []byte // Complete ASN.1 DER content (certificate, signature algorithm and signature).
        RawTBSCertificate       []byte // Certificate part of raw ASN.1 DER content.
        RawSubjectPublicKeyInfo []byte // DER encoded SubjectPublicKeyInfo.
        RawSubject              []byte // DER encoded Subject
        RawIssuer               []byte // DER encoded Issuer

        Signature          []byte
        SignatureAlgorithm SignatureAlgorithm

        PublicKeyAlgorithm PublicKeyAlgorithm
        PublicKey          any

        Version             int
        SerialNumber        *big.Int
        Issuer              pkix.Name
        Subject             pkix.Name
        NotBefore, NotAfter time.Time // Validity bounds.
        KeyUsage            KeyUsage

        // Extensions contains raw X.509 extensions. When parsing certificates,
        // this can be used to extract non-critical extensions that are not
        // parsed by this package. When marshaling certificates, the Extensions
        // field is ignored, see ExtraExtensions.
        Extensions []pkix.Extension

        // ExtraExtensions contains extensions to be copied, raw, into any
        // marshaled certificates. Values override any extensions that would
        // otherwise be produced based on the other fields. The ExtraExtensions
        // field is not populated when parsing certificates, see Extensions.
        ExtraExtensions []pkix.Extension

        // UnhandledCriticalExtensions contains a list of extension IDs that
        // were not (fully) processed when parsing. Verify will fail if this
        // slice is non-empty, unless verification is delegated to an OS
        // library which understands all the critical extensions.
        //
        // Users can access these extensions using Extensions and can remove
        // elements from this slice if they believe that they have been
        // handled.
        UnhandledCriticalExtensions []asn1.ObjectIdentifier

        ExtKeyUsage        []ExtKeyUsage           // Sequence of extended key usages.
        UnknownExtKeyUsage []asn1.ObjectIdentifier // Encountered extended key usages unknown to this package.

        // BasicConstraintsValid indicates whether IsCA, MaxPathLen,
        // and MaxPathLenZero are valid.
        BasicConstraintsValid bool
        IsCA                  bool

        // MaxPathLen and MaxPathLenZero indicate the presence and
        // value of the BasicConstraints' "pathLenConstraint".
        //
        // When parsing a certificate, a positive non-zero MaxPathLen
        // means that the field was specified, -1 means it was unset,
        // and MaxPathLenZero being true mean that the field was
        // explicitly set to zero. The case of MaxPathLen==0 with MaxPathLenZero==false
        // should be treated equivalent to -1 (unset).
        //
        // When generating a certificate, an unset pathLenConstraint
        // can be requested with either MaxPathLen == -1 or using the
        // zero value for both MaxPathLen and MaxPathLenZero.
        MaxPathLen int
        // MaxPathLenZero indicates that BasicConstraintsValid==true
        // and MaxPathLen==0 should be interpreted as an actual
        // maximum path length of zero. Otherwise, that combination is
        // interpreted as MaxPathLen not being set.
        MaxPathLenZero bool

        SubjectKeyId   []byte
        AuthorityKeyId []byte

        // RFC 5280, 4.2.2.1 (Authority Information Access)
        OCSPServer            []string
        IssuingCertificateURL []string

        // Subject Alternate Name values. (Note that these values may not be valid
        // if invalid values were contained within a parsed certificate. For
        // example, an element of DNSNames may not be a valid DNS domain name.)
        DNSNames       []string
        EmailAddresses []string
        IPAddresses    []net.IP
        URIs           []*url.URL

        // Name constraints
        PermittedDNSDomainsCritical bool // if true then the name constraints are marked critical.
        PermittedDNSDomains         []string
        ExcludedDNSDomains          []string
        PermittedIPRanges           []*net.IPNet
        ExcludedIPRanges            []*net.IPNet
        PermittedEmailAddresses     []string
        ExcludedEmailAddresses      []string
        PermittedURIDomains         []string
        ExcludedURIDomains          []string

        // CRL Distribution Points
        CRLDistributionPoints []string

        PolicyIdentifiers []asn1.ObjectIdentifier
}

// ErrUnsupportedAlgorithm results from attempting to perform an operation that
// involves algorithms that are not currently implemented.
var ErrUnsupportedAlgorithm = errors.New("x509: cannot verify signature: algorithm unimplemented")

// debugAllowSHA1 allows SHA-1 signatures. See issue 41682.
var debugAllowSHA1 = godebug.Get("x509sha1") == "1"

// An InsecureAlgorithmError indicates that the SignatureAlgorithm used to
// generate the signature is not secure, and the signature has been rejected.
//
// To temporarily restore support for SHA-1 signatures, include the value
// "x509sha1=1" in the GODEBUG environment variable. Note that this option will
// be removed in Go 1.19.
type InsecureAlgorithmError SignatureAlgorithm

func (e InsecureAlgorithmError) Error() string {
        var override string
        if SignatureAlgorithm(e) == SHA1WithRSA || SignatureAlgorithm(e) == ECDSAWithSHA1 {
                override = " (temporarily override with GODEBUG=x509sha1=1)"
        }
        return fmt.Sprintf("x509: cannot verify signature: insecure algorithm %v", SignatureAlgorithm(e)) + override
}

// ConstraintViolationError results when a requested usage is not permitted by
// a certificate. For example: checking a signature when the public key isn't a
// certificate signing key.
type ConstraintViolationError struct{}

func (ConstraintViolationError) Error() string {
        return "x509: invalid signature: parent certificate cannot sign this kind of certificate"
}

func (c *Certificate) Equal(other *Certificate) bool {
        if c == nil || other == nil {
                return c == other
        }
        return bytes.Equal(c.Raw, other.Raw)
}

func (c *Certificate) hasSANExtension() bool {
        return oidInExtensions(oidExtensionSubjectAltName, c.Extensions)
}

// CheckSignatureFrom verifies that the signature on c is a valid signature
// from parent. SHA1WithRSA and ECDSAWithSHA1 signatures are not supported.
func (c *Certificate) CheckSignatureFrom(parent *Certificate) error {
        // RFC 5280, 4.2.1.9:
        // "If the basic constraints extension is not present in a version 3
        // certificate, or the extension is present but the cA boolean is not
        // asserted, then the certified public key MUST NOT be used to verify
        // certificate signatures."
        if parent.Version == 3 && !parent.BasicConstraintsValid ||
                parent.BasicConstraintsValid && !parent.IsCA {
                return ConstraintViolationError{}
        }

        if parent.KeyUsage != 0 && parent.KeyUsage&KeyUsageCertSign == 0 {
                return ConstraintViolationError{}
        }

        if parent.PublicKeyAlgorithm == UnknownPublicKeyAlgorithm {
                return ErrUnsupportedAlgorithm
        }

        // TODO(agl): don't ignore the path length constraint.

        return checkSignature(c.SignatureAlgorithm, c.RawTBSCertificate, c.Signature, parent.PublicKey, debugAllowSHA1)
}

// CheckSignature verifies that signature is a valid signature over signed from
// c's public key.
func (c *Certificate) CheckSignature(algo SignatureAlgorithm, signed, signature []byte) error {
        return checkSignature(algo, signed, signature, c.PublicKey, true)
}

func (c *Certificate) hasNameConstraints() bool {
        return oidInExtensions(oidExtensionNameConstraints, c.Extensions)
}

func (c *Certificate) getSANExtension() []byte {
        for _, e := range c.Extensions {
                if e.Id.Equal(oidExtensionSubjectAltName) {
                        return e.Value
                }
        }
        return nil
}

func signaturePublicKeyAlgoMismatchError(expectedPubKeyAlgo PublicKeyAlgorithm, pubKey any) error {
        return fmt.Errorf("x509: signature algorithm specifies an %s public key, but have public key of type %T", expectedPubKeyAlgo.String(), pubKey)
}

// checkSignature verifies that signature is a valid signature over signed from
// a crypto.PublicKey.
func checkSignature(algo SignatureAlgorithm, signed, signature []byte, publicKey crypto.PublicKey, allowSHA1 bool) (err error) {
        var hashType crypto.Hash
        var pubKeyAlgo PublicKeyAlgorithm

        for _, details := range signatureAlgorithmDetails {
                if details.algo == algo {
                        hashType = details.hash
                        pubKeyAlgo = details.pubKeyAlgo
                }
        }

        switch hashType {
        case crypto.Hash(0):
                if pubKeyAlgo != Ed25519 {
                        return ErrUnsupportedAlgorithm
                }
        case crypto.MD5:
                return InsecureAlgorithmError(algo)
        case crypto.SHA1:
                if !allowSHA1 {
                        return InsecureAlgorithmError(algo)
                }
                fallthrough
        default:
                if !hashType.Available() {
                        return ErrUnsupportedAlgorithm
                }
                h := hashType.New()
                h.Write(signed)
                signed = h.Sum(nil)
        }

        switch pub := publicKey.(type) {
        case *rsa.PublicKey:
                if pubKeyAlgo != RSA {
                        return signaturePublicKeyAlgoMismatchError(pubKeyAlgo, pub)
                }
                if algo.isRSAPSS() {
                        return rsa.VerifyPSS(pub, hashType, signed, signature, &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash})
                } else {
                        return rsa.VerifyPKCS1v15(pub, hashType, signed, signature)
                }
        case *ecdsa.PublicKey:
                if pubKeyAlgo != ECDSA {
                        return signaturePublicKeyAlgoMismatchError(pubKeyAlgo, pub)
                }
                if !ecdsa.VerifyASN1(pub, signed, signature) {
                        return errors.New("x509: ECDSA verification failure")
                }
                return
        case ed25519.PublicKey:
                if pubKeyAlgo != Ed25519 {
                        return signaturePublicKeyAlgoMismatchError(pubKeyAlgo, pub)
                }
                if !ed25519.Verify(pub, signed, signature) {
                        return errors.New("x509: Ed25519 verification failure")
                }
                return
        }
        return ErrUnsupportedAlgorithm
}

// CheckCRLSignature checks that the signature in crl is from c.
//
// Deprecated: Use RevocationList.CheckSignatureFrom instead.
func (c *Certificate) CheckCRLSignature(crl *pkix.CertificateList) error {
        algo := getSignatureAlgorithmFromAI(crl.SignatureAlgorithm)
        return c.CheckSignature(algo, crl.TBSCertList.Raw, crl.SignatureValue.RightAlign())
}

type UnhandledCriticalExtension struct{}

func (h UnhandledCriticalExtension) Error() string {
        return "x509: unhandled critical extension"
}

type basicConstraints struct {
        IsCA       bool `asn1:"optional"`
        MaxPathLen int  `asn1:"optional,default:-1"`
}

// RFC 5280 4.2.1.4
type policyInformation struct {
        Policy asn1.ObjectIdentifier
        // policyQualifiers omitted
}

const (
        nameTypeEmail = 1
        nameTypeDNS   = 2
        nameTypeURI   = 6
        nameTypeIP    = 7
)

// RFC 5280, 4.2.2.1
type authorityInfoAccess struct {
        Method   asn1.ObjectIdentifier
        Location asn1.RawValue
}

// RFC 5280, 4.2.1.14
type distributionPoint struct {
        DistributionPoint distributionPointName `asn1:"optional,tag:0"`
        Reason            asn1.BitString        `asn1:"optional,tag:1"`
        CRLIssuer         asn1.RawValue         `asn1:"optional,tag:2"`
}

type distributionPointName struct {
        FullName     []asn1.RawValue  `asn1:"optional,tag:0"`
        RelativeName pkix.RDNSequence `asn1:"optional,tag:1"`
}

func reverseBitsInAByte(in byte) byte {
        b1 := in>>4 | in<<4
        b2 := b1>>2&0x33 | b1<<2&0xcc
        b3 := b2>>1&0x55 | b2<<1&0xaa
        return b3
}

// asn1BitLength returns the bit-length of bitString by considering the
// most-significant bit in a byte to be the "first" bit. This convention
// matches ASN.1, but differs from almost everything else.
func asn1BitLength(bitString []byte) int {
        bitLen := len(bitString) * 8

        for i := range bitString {
                b := bitString[len(bitString)-i-1]

                for bit := uint(0); bit < 8; bit++ {
                        if (b>>bit)&1 == 1 {
                                return bitLen
                        }
                        bitLen--
                }
        }

        return 0
}

var (
        oidExtensionSubjectKeyId          = []int{2, 5, 29, 14}
        oidExtensionKeyUsage              = []int{2, 5, 29, 15}
        oidExtensionExtendedKeyUsage      = []int{2, 5, 29, 37}
        oidExtensionAuthorityKeyId        = []int{2, 5, 29, 35}
        oidExtensionBasicConstraints      = []int{2, 5, 29, 19}
        oidExtensionSubjectAltName        = []int{2, 5, 29, 17}
        oidExtensionCertificatePolicies   = []int{2, 5, 29, 32}
        oidExtensionNameConstraints       = []int{2, 5, 29, 30}
        oidExtensionCRLDistributionPoints = []int{2, 5, 29, 31}
        oidExtensionAuthorityInfoAccess   = []int{1, 3, 6, 1, 5, 5, 7, 1, 1}
        oidExtensionCRLNumber             = []int{2, 5, 29, 20}
)

var (
        oidAuthorityInfoAccessOcsp    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 1}
        oidAuthorityInfoAccessIssuers = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 2}
)

// oidNotInExtensions reports whether an extension with the given oid exists in
// extensions.
func oidInExtensions(oid asn1.ObjectIdentifier, extensions []pkix.Extension) bool {
        for _, e := range extensions {
                if e.Id.Equal(oid) {
                        return true
                }
        }
        return false
}

// marshalSANs marshals a list of addresses into a the contents of an X.509
// SubjectAlternativeName extension.
func marshalSANs(dnsNames, emailAddresses []string, ipAddresses []net.IP, uris []*url.URL) (derBytes []byte, err error) {
        var rawValues []asn1.RawValue
        for _, name := range dnsNames {
                if err := isIA5String(name); err != nil {
                        return nil, err
                }
                rawValues = append(rawValues, asn1.RawValue{Tag: nameTypeDNS, Class: 2, Bytes: []byte(name)})
        }
        for _, email := range emailAddresses {
                if err := isIA5String(email); err != nil {
                        return nil, err
                }
                rawValues = append(rawValues, asn1.RawValue{Tag: nameTypeEmail, Class: 2, Bytes: []byte(email)})
        }
        for _, rawIP := range ipAddresses {
                // If possible, we always want to encode IPv4 addresses in 4 bytes.
                ip := rawIP.To4()
                if ip == nil {
                        ip = rawIP
                }
                rawValues = append(rawValues, asn1.RawValue{Tag: nameTypeIP, Class: 2, Bytes: ip})
        }
        for _, uri := range uris {
                uriStr := uri.String()
                if err := isIA5String(uriStr); err != nil {
                        return nil, err
                }
                rawValues = append(rawValues, asn1.RawValue{Tag: nameTypeURI, Class: 2, Bytes: []byte(uriStr)})
        }
        return asn1.Marshal(rawValues)
}

func isIA5String(s string) error {
        for _, r := range s {
                // Per RFC5280 "IA5String is limited to the set of ASCII characters"
                if r > unicode.MaxASCII {
                        return fmt.Errorf("x509: %q cannot be encoded as an IA5String", s)
                }
        }

        return nil
}

func buildCertExtensions(template *Certificate, subjectIsEmpty bool, authorityKeyId []byte, subjectKeyId []byte) (ret []pkix.Extension, err error) {
        ret = make([]pkix.Extension, 10 /* maximum number of elements. */)
        n := 0

        if template.KeyUsage != 0 &&
                !oidInExtensions(oidExtensionKeyUsage, template.ExtraExtensions) {
                ret[n], err = marshalKeyUsage(template.KeyUsage)
                if err != nil {
                        return nil, err
                }
                n++
        }

        if (len(template.ExtKeyUsage) > 0 || len(template.UnknownExtKeyUsage) > 0) &&
                !oidInExtensions(oidExtensionExtendedKeyUsage, template.ExtraExtensions) {
                ret[n], err = marshalExtKeyUsage(template.ExtKeyUsage, template.UnknownExtKeyUsage)
                if err != nil {
                        return nil, err
                }
                n++
        }

        if template.BasicConstraintsValid && !oidInExtensions(oidExtensionBasicConstraints, template.ExtraExtensions) {
                ret[n], err = marshalBasicConstraints(template.IsCA, template.MaxPathLen, template.MaxPathLenZero)
                if err != nil {
                        return nil, err
                }
                n++
        }

        if len(subjectKeyId) > 0 && !oidInExtensions(oidExtensionSubjectKeyId, template.ExtraExtensions) {
                ret[n].Id = oidExtensionSubjectKeyId
                ret[n].Value, err = asn1.Marshal(subjectKeyId)
                if err != nil {
                        return
                }
                n++
        }

        if len(authorityKeyId) > 0 && !oidInExtensions(oidExtensionAuthorityKeyId, template.ExtraExtensions) {
                ret[n].Id = oidExtensionAuthorityKeyId
                ret[n].Value, err = asn1.Marshal(authKeyId{authorityKeyId})
                if err != nil {
                        return
                }
                n++
        }

        if (len(template.OCSPServer) > 0 || len(template.IssuingCertificateURL) > 0) &&
                !oidInExtensions(oidExtensionAuthorityInfoAccess, template.ExtraExtensions) {
                ret[n].Id = oidExtensionAuthorityInfoAccess
                var aiaValues []authorityInfoAccess
                for _, name := range template.OCSPServer {
                        aiaValues = append(aiaValues, authorityInfoAccess{
                                Method:   oidAuthorityInfoAccessOcsp,
                                Location: asn1.RawValue{Tag: 6, Class: 2, Bytes: []byte(name)},
                        })
                }
                for _, name := range template.IssuingCertificateURL {
                        aiaValues = append(aiaValues, authorityInfoAccess{
                                Method:   oidAuthorityInfoAccessIssuers,
                                Location: asn1.RawValue{Tag: 6, Class: 2, Bytes: []byte(name)},
                        })
                }
                ret[n].Value, err = asn1.Marshal(aiaValues)
                if err != nil {
                        return
                }
                n++
        }

        if (len(template.DNSNames) > 0 || len(template.EmailAddresses) > 0 || len(template.IPAddresses) > 0 || len(template.URIs) > 0) &&
                !oidInExtensions(oidExtensionSubjectAltName, template.ExtraExtensions) {
                ret[n].Id = oidExtensionSubjectAltName
                // From RFC 5280, Section 4.2.1.6:
                // “If the subject field contains an empty sequence ... then
                // subjectAltName extension ... is marked as critical”
                ret[n].Critical = subjectIsEmpty
                ret[n].Value, err = marshalSANs(template.DNSNames, template.EmailAddresses, template.IPAddresses, template.URIs)
                if err != nil {
                        return
                }
                n++
        }

        if len(template.PolicyIdentifiers) > 0 &&
                !oidInExtensions(oidExtensionCertificatePolicies, template.ExtraExtensions) {
                ret[n], err = marshalCertificatePolicies(template.PolicyIdentifiers)
                if err != nil {
                        return nil, err
                }
                n++
        }

        if (len(template.PermittedDNSDomains) > 0 || len(template.ExcludedDNSDomains) > 0 ||
                len(template.PermittedIPRanges) > 0 || len(template.ExcludedIPRanges) > 0 ||
                len(template.PermittedEmailAddresses) > 0 || len(template.ExcludedEmailAddresses) > 0 ||
                len(template.PermittedURIDomains) > 0 || len(template.ExcludedURIDomains) > 0) &&
                !oidInExtensions(oidExtensionNameConstraints, template.ExtraExtensions) {
                ret[n].Id = oidExtensionNameConstraints
                ret[n].Critical = template.PermittedDNSDomainsCritical

                ipAndMask := func(ipNet *net.IPNet) []byte {
                        maskedIP := ipNet.IP.Mask(ipNet.Mask)
                        ipAndMask := make([]byte, 0, len(maskedIP)+len(ipNet.Mask))
                        ipAndMask = append(ipAndMask, maskedIP...)
                        ipAndMask = append(ipAndMask, ipNet.Mask...)
                        return ipAndMask
                }

                serialiseConstraints := func(dns []string, ips []*net.IPNet, emails []string, uriDomains []string) (der []byte, err error) {
                        var b cryptobyte.Builder

                        for _, name := range dns {
                                if err = isIA5String(name); err != nil {
                                        return nil, err
                                }

                                b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
                                        b.AddASN1(cryptobyte_asn1.Tag(2).ContextSpecific(), func(b *cryptobyte.Builder) {
                                                b.AddBytes([]byte(name))
                                        })
                                })
                        }

                        for _, ipNet := range ips {
                                b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
                                        b.AddASN1(cryptobyte_asn1.Tag(7).ContextSpecific(), func(b *cryptobyte.Builder) {
                                                b.AddBytes(ipAndMask(ipNet))
                                        })
                                })
                        }

                        for _, email := range emails {
                                if err = isIA5String(email); err != nil {
                                        return nil, err
                                }

                                b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
                                        b.AddASN1(cryptobyte_asn1.Tag(1).ContextSpecific(), func(b *cryptobyte.Builder) {
                                                b.AddBytes([]byte(email))
                                        })
                                })
                        }

                        for _, uriDomain := range uriDomains {
                                if err = isIA5String(uriDomain); err != nil {
                                        return nil, err
                                }

                                b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
                                        b.AddASN1(cryptobyte_asn1.Tag(6).ContextSpecific(), func(b *cryptobyte.Builder) {
                                                b.AddBytes([]byte(uriDomain))
                                        })
                                })
                        }

                        return b.Bytes()
                }

                permitted, err := serialiseConstraints(template.PermittedDNSDomains, template.PermittedIPRanges, template.PermittedEmailAddresses, template.PermittedURIDomains)
                if err != nil {
                        return nil, err
                }

                excluded, err := serialiseConstraints(template.ExcludedDNSDomains, template.ExcludedIPRanges, template.ExcludedEmailAddresses, template.ExcludedURIDomains)
                if err != nil {
                        return nil, err
                }

                var b cryptobyte.Builder
                b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
                        if len(permitted) > 0 {
                                b.AddASN1(cryptobyte_asn1.Tag(0).ContextSpecific().Constructed(), func(b *cryptobyte.Builder) {
                                        b.AddBytes(permitted)
                                })
                        }

                        if len(excluded) > 0 {
                                b.AddASN1(cryptobyte_asn1.Tag(1).ContextSpecific().Constructed(), func(b *cryptobyte.Builder) {
                                        b.AddBytes(excluded)
                                })
                        }
                })

                ret[n].Value, err = b.Bytes()
                if err != nil {
                        return nil, err
                }
                n++
        }

        if len(template.CRLDistributionPoints) > 0 &&
                !oidInExtensions(oidExtensionCRLDistributionPoints, template.ExtraExtensions) {
                ret[n].Id = oidExtensionCRLDistributionPoints

                var crlDp []distributionPoint
                for _, name := range template.CRLDistributionPoints {
                        dp := distributionPoint{
                                DistributionPoint: distributionPointName{
                                        FullName: []asn1.RawValue{
                                                {Tag: 6, Class: 2, Bytes: []byte(name)},
                                        },
                                },
                        }
                        crlDp = append(crlDp, dp)
                }

                ret[n].Value, err = asn1.Marshal(crlDp)
                if err != nil {
                        return
                }
                n++
        }

        // Adding another extension here? Remember to update the maximum number
        // of elements in the make() at the top of the function and the list of
        // template fields used in CreateCertificate documentation.

        return append(ret[:n], template.ExtraExtensions...), nil
}

func marshalKeyUsage(ku KeyUsage) (pkix.Extension, error) {
        ext := pkix.Extension{Id: oidExtensionKeyUsage, Critical: true}

        var a [2]byte
        a[0] = reverseBitsInAByte(byte(ku))
        a[1] = reverseBitsInAByte(byte(ku >> 8))

        l := 1
        if a[1] != 0 {
                l = 2
        }

        bitString := a[:l]
        var err error
        ext.Value, err = asn1.Marshal(asn1.BitString{Bytes: bitString, BitLength: asn1BitLength(bitString)})
        return ext, err
}

func marshalExtKeyUsage(extUsages []ExtKeyUsage, unknownUsages []asn1.ObjectIdentifier) (pkix.Extension, error) {
        ext := pkix.Extension{Id: oidExtensionExtendedKeyUsage}

        oids := make([]asn1.ObjectIdentifier, len(extUsages)+len(unknownUsages))
        for i, u := range extUsages {
                if oid, ok := oidFromExtKeyUsage(u); ok {
                        oids[i] = oid
                } else {
                        return ext, errors.New("x509: unknown extended key usage")
                }
        }

        copy(oids[len(extUsages):], unknownUsages)

        var err error
        ext.Value, err = asn1.Marshal(oids)
        return ext, err
}

func marshalBasicConstraints(isCA bool, maxPathLen int, maxPathLenZero bool) (pkix.Extension, error) {
        ext := pkix.Extension{Id: oidExtensionBasicConstraints, Critical: true}
        // Leaving MaxPathLen as zero indicates that no maximum path
        // length is desired, unless MaxPathLenZero is set. A value of
        // -1 causes encoding/asn1 to omit the value as desired.
        if maxPathLen == 0 && !maxPathLenZero {
                maxPathLen = -1
        }
        var err error
        ext.Value, err = asn1.Marshal(basicConstraints{isCA, maxPathLen})
        return ext, err
}

func marshalCertificatePolicies(policyIdentifiers []asn1.ObjectIdentifier) (pkix.Extension, error) {
        ext := pkix.Extension{Id: oidExtensionCertificatePolicies}
        policies := make([]policyInformation, len(policyIdentifiers))
        for i, policy := range policyIdentifiers {
                policies[i].Policy = policy
        }
        var err error
        ext.Value, err = asn1.Marshal(policies)
        return ext, err
}

func buildCSRExtensions(template *CertificateRequest) ([]pkix.Extension, error) {
        var ret []pkix.Extension

        if (len(template.DNSNames) > 0 || len(template.EmailAddresses) > 0 || len(template.IPAddresses) > 0 || len(template.URIs) > 0) &&
                !oidInExtensions(oidExtensionSubjectAltName, template.ExtraExtensions) {
                sanBytes, err := marshalSANs(template.DNSNames, template.EmailAddresses, template.IPAddresses, template.URIs)
                if err != nil {
                        return nil, err
                }

                ret = append(ret, pkix.Extension{
                        Id:    oidExtensionSubjectAltName,
                        Value: sanBytes,
                })
        }

        return append(ret, template.ExtraExtensions...), nil
}

func subjectBytes(cert *Certificate) ([]byte, error) {
        if len(cert.RawSubject) > 0 {
                return cert.RawSubject, nil
        }

        return asn1.Marshal(cert.Subject.ToRDNSequence())
}

// signingParamsForPublicKey returns the parameters to use for signing with
// priv. If requestedSigAlgo is not zero then it overrides the default
// signature algorithm.
func signingParamsForPublicKey(pub any, requestedSigAlgo SignatureAlgorithm) (hashFunc crypto.Hash, sigAlgo pkix.AlgorithmIdentifier, err error) {
        var pubType PublicKeyAlgorithm

        switch pub := pub.(type) {
        case *rsa.PublicKey:
                pubType = RSA
                hashFunc = crypto.SHA256
                sigAlgo.Algorithm = oidSignatureSHA256WithRSA
                sigAlgo.Parameters = asn1.NullRawValue

        case *ecdsa.PublicKey:
                pubType = ECDSA

                switch pub.Curve {
                case elliptic.P224(), elliptic.P256():
                        hashFunc = crypto.SHA256
                        sigAlgo.Algorithm = oidSignatureECDSAWithSHA256
                case elliptic.P384():
                        hashFunc = crypto.SHA384
                        sigAlgo.Algorithm = oidSignatureECDSAWithSHA384
                case elliptic.P521():
                        hashFunc = crypto.SHA512
                        sigAlgo.Algorithm = oidSignatureECDSAWithSHA512
                default:
                        err = errors.New("x509: unknown elliptic curve")
                }

        case ed25519.PublicKey:
                pubType = Ed25519
                sigAlgo.Algorithm = oidSignatureEd25519

        default:
                err = errors.New("x509: only RSA, ECDSA and Ed25519 keys supported")
        }

        if err != nil {
                return
        }

        if requestedSigAlgo == 0 {
                return
        }

        found := false
        for _, details := range signatureAlgorithmDetails {
                if details.algo == requestedSigAlgo {
                        if details.pubKeyAlgo != pubType {
                                err = errors.New("x509: requested SignatureAlgorithm does not match private key type")
                                return
                        }
                        sigAlgo.Algorithm, hashFunc = details.oid, details.hash
                        if hashFunc == 0 && pubType != Ed25519 {
                                err = errors.New("x509: cannot sign with hash function requested")
                                return
                        }
                        if requestedSigAlgo.isRSAPSS() {
                                sigAlgo.Parameters = hashToPSSParameters[hashFunc]
                        }
                        found = true
                        break
                }
        }

        if !found {
                err = errors.New("x509: unknown SignatureAlgorithm")
        }

        return
}

// emptyASN1Subject is the ASN.1 DER encoding of an empty Subject, which is
// just an empty SEQUENCE.
var emptyASN1Subject = []byte{0x30, 0}

// CreateCertificate creates a new X.509 v3 certificate based on a template.
// The following members of template are currently used:
//
//   - AuthorityKeyId
//   - BasicConstraintsValid
//   - CRLDistributionPoints
//   - DNSNames
//   - EmailAddresses
//   - ExcludedDNSDomains
//   - ExcludedEmailAddresses
//   - ExcludedIPRanges
//   - ExcludedURIDomains
//   - ExtKeyUsage
//   - ExtraExtensions
//   - IPAddresses
//   - IsCA
//   - IssuingCertificateURL
//   - KeyUsage
//   - MaxPathLen
//   - MaxPathLenZero
//   - NotAfter
//   - NotBefore
//   - OCSPServer
//   - PermittedDNSDomains
//   - PermittedDNSDomainsCritical
//   - PermittedEmailAddresses
//   - PermittedIPRanges
//   - PermittedURIDomains
//   - PolicyIdentifiers
//   - SerialNumber
//   - SignatureAlgorithm
//   - Subject
//   - SubjectKeyId
//   - URIs
//   - UnknownExtKeyUsage
//
// The certificate is signed by parent. If parent is equal to template then the
// certificate is self-signed. The parameter pub is the public key of the
// certificate to be generated and priv is the private key of the signer.
//
// The returned slice is the certificate in DER encoding.
//
// The currently supported key types are *rsa.PublicKey, *ecdsa.PublicKey and
// ed25519.PublicKey. pub must be a supported key type, and priv must be a
// crypto.Signer with a supported public key.
//
// The AuthorityKeyId will be taken from the SubjectKeyId of parent, if any,
// unless the resulting certificate is self-signed. Otherwise the value from
// template will be used.
//
// If SubjectKeyId from template is empty and the template is a CA, SubjectKeyId
// will be generated from the hash of the public key.
func CreateCertificate(rand io.Reader, template, parent *Certificate, pub, priv any) ([]byte, error) {
        key, ok := priv.(crypto.Signer)
        if !ok {
                return nil, errors.New("x509: certificate private key does not implement crypto.Signer")
        }

        if template.SerialNumber == nil {
                return nil, errors.New("x509: no SerialNumber given")
        }

        // RFC 5280 Section 4.1.2.2: serial number must positive and should not be longer
        // than 20 octets.
        //
        // We cannot simply check for len(serialBytes) > 20, because encoding/asn1 may
        // pad the slice in order to prevent the integer being mistaken for a negative
        // number (DER uses the high bit of the left-most byte to indicate the sign.),
        // so we need to double check the composition of the serial if it is exactly
        // 20 bytes.
        if template.SerialNumber.Sign() == -1 {
                return nil, errors.New("x509: serial number must be positive")
        }
        serialBytes := template.SerialNumber.Bytes()
        if len(serialBytes) > 20 || (len(serialBytes) == 20 && serialBytes[0]&0x80 != 0) {
                return nil, errors.New("x509: serial number exceeds 20 octets")
        }

        if template.BasicConstraintsValid && !template.IsCA && template.MaxPathLen != -1 && (template.MaxPathLen != 0 || template.MaxPathLenZero) {
                return nil, errors.New("x509: only CAs are allowed to specify MaxPathLen")
        }

        hashFunc, signatureAlgorithm, err := signingParamsForPublicKey(key.Public(), template.SignatureAlgorithm)
        if err != nil {
                return nil, err
        }

        publicKeyBytes, publicKeyAlgorithm, err := marshalPublicKey(pub)
        if err != nil {
                return nil, err
        }

        asn1Issuer, err := subjectBytes(parent)
        if err != nil {
                return nil, err
        }

        asn1Subject, err := subjectBytes(template)
        if err != nil {
                return nil, err
        }

        authorityKeyId := template.AuthorityKeyId
        if !bytes.Equal(asn1Issuer, asn1Subject) && len(parent.SubjectKeyId) > 0 {
                authorityKeyId = parent.SubjectKeyId
        }

        subjectKeyId := template.SubjectKeyId
        if len(subjectKeyId) == 0 && template.IsCA {
                // SubjectKeyId generated using method 1 in RFC 5280, Section 4.2.1.2:
                //   (1) The keyIdentifier is composed of the 160-bit SHA-1 hash of the
                //   value of the BIT STRING subjectPublicKey (excluding the tag,
                //   length, and number of unused bits).
                h := sha1.Sum(publicKeyBytes)
                subjectKeyId = h[:]
        }

        // Check that the signer's public key matches the private key, if available.
        type privateKey interface {
                Equal(crypto.PublicKey) bool
        }
        if privPub, ok := key.Public().(privateKey); !ok {
                return nil, errors.New("x509: internal error: supported public key does not implement Equal")
        } else if parent.PublicKey != nil && !privPub.Equal(parent.PublicKey) {
                return nil, errors.New("x509: provided PrivateKey doesn't match parent's PublicKey")
        }

        extensions, err := buildCertExtensions(template, bytes.Equal(asn1Subject, emptyASN1Subject), authorityKeyId, subjectKeyId)
        if err != nil {
                return nil, err
        }

        encodedPublicKey := asn1.BitString{BitLength: len(publicKeyBytes) * 8, Bytes: publicKeyBytes}
        c := tbsCertificate{
                Version:            2,
                SerialNumber:       template.SerialNumber,
                SignatureAlgorithm: signatureAlgorithm,
                Issuer:             asn1.RawValue{FullBytes: asn1Issuer},
                Validity:           validity{template.NotBefore.UTC(), template.NotAfter.UTC()},
                Subject:            asn1.RawValue{FullBytes: asn1Subject},
                PublicKey:          publicKeyInfo{nil, publicKeyAlgorithm, encodedPublicKey},
                Extensions:         extensions,
        }

        tbsCertContents, err := asn1.Marshal(c)
        if err != nil {
                return nil, err
        }
        c.Raw = tbsCertContents

        signed := tbsCertContents
        if hashFunc != 0 {
                h := hashFunc.New()
                h.Write(signed)
                signed = h.Sum(nil)
        }

        var signerOpts crypto.SignerOpts = hashFunc
        if template.SignatureAlgorithm != 0 && template.SignatureAlgorithm.isRSAPSS() {
                signerOpts = &rsa.PSSOptions{
                        SaltLength: rsa.PSSSaltLengthEqualsHash,
                        Hash:       hashFunc,
                }
        }

        var signature []byte
        signature, err = key.Sign(rand, signed, signerOpts)
        if err != nil {
                return nil, err
        }

        signedCert, err := asn1.Marshal(certificate{
                nil,
                c,
                signatureAlgorithm,
                asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
        })
        if err != nil {
                return nil, err
        }

        // Check the signature to ensure the crypto.Signer behaved correctly.
        sigAlg := getSignatureAlgorithmFromAI(signatureAlgorithm)
        switch sigAlg {
        case MD5WithRSA:
                // We skip the check if the signature algorithm is only supported for
                // signing, not verification.
        default:
                if err := checkSignature(sigAlg, c.Raw, signature, key.Public(), true); err != nil {
                        return nil, fmt.Errorf("x509: signature over certificate returned by signer is invalid: %w", err)
                }
        }

        return signedCert, nil
}

// pemCRLPrefix is the magic string that indicates that we have a PEM encoded
// CRL.
var pemCRLPrefix = []byte("-----BEGIN X509 CRL")

// pemType is the type of a PEM encoded CRL.
var pemType = "X509 CRL"

// ParseCRL parses a CRL from the given bytes. It's often the case that PEM
// encoded CRLs will appear where they should be DER encoded, so this function
// will transparently handle PEM encoding as long as there isn't any leading
// garbage.
//
// Deprecated: Use ParseRevocationList instead.
func ParseCRL(crlBytes []byte) (*pkix.CertificateList, error) {
        if bytes.HasPrefix(crlBytes, pemCRLPrefix) {
                block, _ := pem.Decode(crlBytes)
                if block != nil && block.Type == pemType {
                        crlBytes = block.Bytes
                }
        }
        return ParseDERCRL(crlBytes)
}

// ParseDERCRL parses a DER encoded CRL from the given bytes.
//
// Deprecated: Use ParseRevocationList instead.
func ParseDERCRL(derBytes []byte) (*pkix.CertificateList, error) {
        certList := new(pkix.CertificateList)
        if rest, err := asn1.Unmarshal(derBytes, certList); err != nil {
                return nil, err
        } else if len(rest) != 0 {
                return nil, errors.New("x509: trailing data after CRL")
        }
        return certList, nil
}

// CreateCRL returns a DER encoded CRL, signed by this Certificate, that
// contains the given list of revoked certificates.
//
// Deprecated: this method does not generate an RFC 5280 conformant X.509 v2 CRL.
// To generate a standards compliant CRL, use CreateRevocationList instead.
func (c *Certificate) CreateCRL(rand io.Reader, priv any, revokedCerts []pkix.RevokedCertificate, now, expiry time.Time) (crlBytes []byte, err error) {
        key, ok := priv.(crypto.Signer)
        if !ok {
                return nil, errors.New("x509: certificate private key does not implement crypto.Signer")
        }

        hashFunc, signatureAlgorithm, err := signingParamsForPublicKey(key.Public(), 0)
        if err != nil {
                return nil, err
        }

        // Force revocation times to UTC per RFC 5280.
        revokedCertsUTC := make([]pkix.RevokedCertificate, len(revokedCerts))
        for i, rc := range revokedCerts {
                rc.RevocationTime = rc.RevocationTime.UTC()
                revokedCertsUTC[i] = rc
        }

        tbsCertList := pkix.TBSCertificateList{
                Version:             1,
                Signature:           signatureAlgorithm,
                Issuer:              c.Subject.ToRDNSequence(),
                ThisUpdate:          now.UTC(),
                NextUpdate:          expiry.UTC(),
                RevokedCertificates: revokedCertsUTC,
        }

        // Authority Key Id
        if len(c.SubjectKeyId) > 0 {
                var aki pkix.Extension
                aki.Id = oidExtensionAuthorityKeyId
                aki.Value, err = asn1.Marshal(authKeyId{Id: c.SubjectKeyId})
                if err != nil {
                        return
                }
                tbsCertList.Extensions = append(tbsCertList.Extensions, aki)
        }

        tbsCertListContents, err := asn1.Marshal(tbsCertList)
        if err != nil {
                return
        }

        signed := tbsCertListContents
        if hashFunc != 0 {
                h := hashFunc.New()
                h.Write(signed)
                signed = h.Sum(nil)
        }

        var signature []byte
        signature, err = key.Sign(rand, signed, hashFunc)
        if err != nil {
                return
        }

        return asn1.Marshal(pkix.CertificateList{
                TBSCertList:        tbsCertList,
                SignatureAlgorithm: signatureAlgorithm,
                SignatureValue:     asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
        })
}

// CertificateRequest represents a PKCS #10, certificate signature request.
type CertificateRequest struct {
        Raw                      []byte // Complete ASN.1 DER content (CSR, signature algorithm and signature).
        RawTBSCertificateRequest []byte // Certificate request info part of raw ASN.1 DER content.
        RawSubjectPublicKeyInfo  []byte // DER encoded SubjectPublicKeyInfo.
        RawSubject               []byte // DER encoded Subject.

        Version            int
        Signature          []byte
        SignatureAlgorithm SignatureAlgorithm

        PublicKeyAlgorithm PublicKeyAlgorithm
        PublicKey          any

        Subject pkix.Name

        // Attributes contains the CSR attributes that can parse as
        // pkix.AttributeTypeAndValueSET.
        //
        // Deprecated: Use Extensions and ExtraExtensions instead for parsing and
        // generating the requestedExtensions attribute.
        Attributes []pkix.AttributeTypeAndValueSET

        // Extensions contains all requested extensions, in raw form. When parsing
        // CSRs, this can be used to extract extensions that are not parsed by this
        // package.
        Extensions []pkix.Extension

        // ExtraExtensions contains extensions to be copied, raw, into any CSR
        // marshaled by CreateCertificateRequest. Values override any extensions
        // that would otherwise be produced based on the other fields but are
        // overridden by any extensions specified in Attributes.
        //
        // The ExtraExtensions field is not populated by ParseCertificateRequest,
        // see Extensions instead.
        ExtraExtensions []pkix.Extension

        // Subject Alternate Name values.
        DNSNames       []string
        EmailAddresses []string
        IPAddresses    []net.IP
        URIs           []*url.URL
}

// These structures reflect the ASN.1 structure of X.509 certificate
// signature requests (see RFC 2986):

type tbsCertificateRequest struct {
        Raw           asn1.RawContent
        Version       int
        Subject       asn1.RawValue
        PublicKey     publicKeyInfo
        RawAttributes []asn1.RawValue `asn1:"tag:0"`
}

type certificateRequest struct {
        Raw                asn1.RawContent
        TBSCSR             tbsCertificateRequest
        SignatureAlgorithm pkix.AlgorithmIdentifier
        SignatureValue     asn1.BitString
}

// oidExtensionRequest is a PKCS #9 OBJECT IDENTIFIER that indicates requested
// extensions in a CSR.
var oidExtensionRequest = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 14}

// newRawAttributes converts AttributeTypeAndValueSETs from a template
// CertificateRequest's Attributes into tbsCertificateRequest RawAttributes.
func newRawAttributes(attributes []pkix.AttributeTypeAndValueSET) ([]asn1.RawValue, error) {
        var rawAttributes []asn1.RawValue
        b, err := asn1.Marshal(attributes)
        if err != nil {
                return nil, err
        }
        rest, err := asn1.Unmarshal(b, &rawAttributes)
        if err != nil {
                return nil, err
        }
        if len(rest) != 0 {
                return nil, errors.New("x509: failed to unmarshal raw CSR Attributes")
        }
        return rawAttributes, nil
}

// parseRawAttributes Unmarshals RawAttributes into AttributeTypeAndValueSETs.
func parseRawAttributes(rawAttributes []asn1.RawValue) []pkix.AttributeTypeAndValueSET {
        var attributes []pkix.AttributeTypeAndValueSET
        for _, rawAttr := range rawAttributes {
                var attr pkix.AttributeTypeAndValueSET
                rest, err := asn1.Unmarshal(rawAttr.FullBytes, &attr)
                // Ignore attributes that don't parse into pkix.AttributeTypeAndValueSET
                // (i.e.: challengePassword or unstructuredName).
                if err == nil && len(rest) == 0 {
                        attributes = append(attributes, attr)
                }
        }
        return attributes
}

// parseCSRExtensions parses the attributes from a CSR and extracts any
// requested extensions.
func parseCSRExtensions(rawAttributes []asn1.RawValue) ([]pkix.Extension, error) {
        // pkcs10Attribute reflects the Attribute structure from RFC 2986, Section 4.1.
        type pkcs10Attribute struct {
                Id     asn1.ObjectIdentifier
                Values []asn1.RawValue `asn1:"set"`
        }

        var ret []pkix.Extension
        seenExts := make(map[string]bool)
        for _, rawAttr := range rawAttributes {
                var attr pkcs10Attribute
                if rest, err := asn1.Unmarshal(rawAttr.FullBytes, &attr); err != nil || len(rest) != 0 || len(attr.Values) == 0 {
                        // Ignore attributes that don't parse.
                        continue
                }
                oidStr := attr.Id.String()
                if seenExts[oidStr] {
                        return nil, errors.New("x509: certificate request contains duplicate extensions")
                }
                seenExts[oidStr] = true

                if !attr.Id.Equal(oidExtensionRequest) {
                        continue
                }

                var extensions []pkix.Extension
                if _, err := asn1.Unmarshal(attr.Values[0].FullBytes, &extensions); err != nil {
                        return nil, err
                }
                requestedExts := make(map[string]bool)
                for _, ext := range extensions {
                        oidStr := ext.Id.String()
                        if requestedExts[oidStr] {
                                return nil, errors.New("x509: certificate request contains duplicate requested extensions")
                        }
                        requestedExts[oidStr] = true
                }
                ret = append(ret, extensions...)
        }

        return ret, nil
}

// CreateCertificateRequest creates a new certificate request based on a
// template. The following members of template are used:
//
//   - SignatureAlgorithm
//   - Subject
//   - DNSNames
//   - EmailAddresses
//   - IPAddresses
//   - URIs
//   - ExtraExtensions
//   - Attributes (deprecated)
//
// priv is the private key to sign the CSR with, and the corresponding public
// key will be included in the CSR. It must implement crypto.Signer and its
// Public() method must return a *rsa.PublicKey or a *ecdsa.PublicKey or a
// ed25519.PublicKey. (A *rsa.PrivateKey, *ecdsa.PrivateKey or
// ed25519.PrivateKey satisfies this.)
//
// The returned slice is the certificate request in DER encoding.
func CreateCertificateRequest(rand io.Reader, template *CertificateRequest, priv any) (csr []byte, err error) {
        key, ok := priv.(crypto.Signer)
        if !ok {
                return nil, errors.New("x509: certificate private key does not implement crypto.Signer")
        }

        var hashFunc crypto.Hash
        var sigAlgo pkix.AlgorithmIdentifier
        hashFunc, sigAlgo, err = signingParamsForPublicKey(key.Public(), template.SignatureAlgorithm)
        if err != nil {
                return nil, err
        }

        var publicKeyBytes []byte
        var publicKeyAlgorithm pkix.AlgorithmIdentifier
        publicKeyBytes, publicKeyAlgorithm, err = marshalPublicKey(key.Public())
        if err != nil {
                return nil, err
        }

        extensions, err := buildCSRExtensions(template)
        if err != nil {
                return nil, err
        }

        // Make a copy of template.Attributes because we may alter it below.
        attributes := make([]pkix.AttributeTypeAndValueSET, 0, len(template.Attributes))
        for _, attr := range template.Attributes {
                values := make([][]pkix.AttributeTypeAndValue, len(attr.Value))
                copy(values, attr.Value)
                attributes = append(attributes, pkix.AttributeTypeAndValueSET{
                        Type:  attr.Type,
                        Value: values,
                })
        }

        extensionsAppended := false
        if len(extensions) > 0 {
                // Append the extensions to an existing attribute if possible.
                for _, atvSet := range attributes {
                        if !atvSet.Type.Equal(oidExtensionRequest) || len(atvSet.Value) == 0 {
                                continue
                        }

                        // specifiedExtensions contains all the extensions that we
                        // found specified via template.Attributes.
                        specifiedExtensions := make(map[string]bool)

                        for _, atvs := range atvSet.Value {
                                for _, atv := range atvs {
                                        specifiedExtensions[atv.Type.String()] = true
                                }
                        }

                        newValue := make([]pkix.AttributeTypeAndValue, 0, len(atvSet.Value[0])+len(extensions))
                        newValue = append(newValue, atvSet.Value[0]...)

                        for _, e := range extensions {
                                if specifiedExtensions[e.Id.String()] {
                                        // Attributes already contained a value for
                                        // this extension and it takes priority.
                                        continue
                                }

                                newValue = append(newValue, pkix.AttributeTypeAndValue{
                                        // There is no place for the critical
                                        // flag in an AttributeTypeAndValue.
                                        Type:  e.Id,
                                        Value: e.Value,
                                })
                        }

                        atvSet.Value[0] = newValue
                        extensionsAppended = true
                        break
                }
        }

        rawAttributes, err := newRawAttributes(attributes)
        if err != nil {
                return
        }

        // If not included in attributes, add a new attribute for the
        // extensions.
        if len(extensions) > 0 && !extensionsAppended {
                attr := struct {
                        Type  asn1.ObjectIdentifier
                        Value [][]pkix.Extension `asn1:"set"`
                }{
                        Type:  oidExtensionRequest,
                        Value: [][]pkix.Extension{extensions},
                }

                b, err := asn1.Marshal(attr)
                if err != nil {
                        return nil, errors.New("x509: failed to serialise extensions attribute: " + err.Error())
                }

                var rawValue asn1.RawValue
                if _, err := asn1.Unmarshal(b, &rawValue); err != nil {
                        return nil, err
                }

                rawAttributes = append(rawAttributes, rawValue)
        }

        asn1Subject := template.RawSubject
        if len(asn1Subject) == 0 {
                asn1Subject, err = asn1.Marshal(template.Subject.ToRDNSequence())
                if err != nil {
                        return nil, err
                }
        }

        tbsCSR := tbsCertificateRequest{
                Version: 0, // PKCS #10, RFC 2986
                Subject: asn1.RawValue{FullBytes: asn1Subject},
                PublicKey: publicKeyInfo{
                        Algorithm: publicKeyAlgorithm,
                        PublicKey: asn1.BitString{
                                Bytes:     publicKeyBytes,
                                BitLength: len(publicKeyBytes) * 8,
                        },
                },
                RawAttributes: rawAttributes,
        }

        tbsCSRContents, err := asn1.Marshal(tbsCSR)
        if err != nil {
                return
        }
        tbsCSR.Raw = tbsCSRContents

        signed := tbsCSRContents
        if hashFunc != 0 {
                h := hashFunc.New()
                h.Write(signed)
                signed = h.Sum(nil)
        }

        var signature []byte
        signature, err = key.Sign(rand, signed, hashFunc)
        if err != nil {
                return
        }

        return asn1.Marshal(certificateRequest{
                TBSCSR:             tbsCSR,
                SignatureAlgorithm: sigAlgo,
                SignatureValue: asn1.BitString{
                        Bytes:     signature,
                        BitLength: len(signature) * 8,
                },
        })
}

// ParseCertificateRequest parses a single certificate request from the
// given ASN.1 DER data.
func ParseCertificateRequest(asn1Data []byte) (*CertificateRequest, error) {
        var csr certificateRequest

        rest, err := asn1.Unmarshal(asn1Data, &csr)
        if err != nil {
                return nil, err
        } else if len(rest) != 0 {
                return nil, asn1.SyntaxError{Msg: "trailing data"}
        }

        return parseCertificateRequest(&csr)
}

func parseCertificateRequest(in *certificateRequest) (*CertificateRequest, error) {
        out := &CertificateRequest{
                Raw:                      in.Raw,
                RawTBSCertificateRequest: in.TBSCSR.Raw,
                RawSubjectPublicKeyInfo:  in.TBSCSR.PublicKey.Raw,
                RawSubject:               in.TBSCSR.Subject.FullBytes,

                Signature:          in.SignatureValue.RightAlign(),
                SignatureAlgorithm: getSignatureAlgorithmFromAI(in.SignatureAlgorithm),

                PublicKeyAlgorithm: getPublicKeyAlgorithmFromOID(in.TBSCSR.PublicKey.Algorithm.Algorithm),

                Version:    in.TBSCSR.Version,
                Attributes: parseRawAttributes(in.TBSCSR.RawAttributes),
        }

        var err error
        out.PublicKey, err = parsePublicKey(out.PublicKeyAlgorithm, &in.TBSCSR.PublicKey)
        if err != nil {
                return nil, err
        }

        var subject pkix.RDNSequence
        if rest, err := asn1.Unmarshal(in.TBSCSR.Subject.FullBytes, &subject); err != nil {
                return nil, err
        } else if len(rest) != 0 {
                return nil, errors.New("x509: trailing data after X.509 Subject")
        }

        out.Subject.FillFromRDNSequence(&subject)

        if out.Extensions, err = parseCSRExtensions(in.TBSCSR.RawAttributes); err != nil {
                return nil, err
        }

        for _, extension := range out.Extensions {
                switch {
                case extension.Id.Equal(oidExtensionSubjectAltName):
                        out.DNSNames, out.EmailAddresses, out.IPAddresses, out.URIs, err = parseSANExtension(extension.Value)
                        if err != nil {
                                return nil, err
                        }
                }
        }

        return out, nil
}

// CheckSignature reports whether the signature on c is valid.
func (c *CertificateRequest) CheckSignature() error {
        return checkSignature(c.SignatureAlgorithm, c.RawTBSCertificateRequest, c.Signature, c.PublicKey, true)
}

// RevocationList contains the fields used to create an X.509 v2 Certificate
// Revocation list with CreateRevocationList.
type RevocationList struct {
        Raw                  []byte
        RawTBSRevocationList []byte
        RawIssuer            []byte

        Issuer         pkix.Name
        AuthorityKeyId []byte

        Signature []byte
        // SignatureAlgorithm is used to determine the signature algorithm to be
        // used when signing the CRL. If 0 the default algorithm for the signing
        // key will be used.
        SignatureAlgorithm SignatureAlgorithm

        // RevokedCertificates is used to populate the revokedCertificates
        // sequence in the CRL, it may be empty. RevokedCertificates may be nil,
        // in which case an empty CRL will be created.
        RevokedCertificates []pkix.RevokedCertificate

        // Number is used to populate the X.509 v2 cRLNumber extension in the CRL,
        // which should be a monotonically increasing sequence number for a given
        // CRL scope and CRL issuer.
        Number *big.Int

        // ThisUpdate is used to populate the thisUpdate field in the CRL, which
        // indicates the issuance date of the CRL.
        ThisUpdate time.Time
        // NextUpdate is used to populate the nextUpdate field in the CRL, which
        // indicates the date by which the next CRL will be issued. NextUpdate
        // must be greater than ThisUpdate.
        NextUpdate time.Time

        // Extensions contains raw X.509 extensions. When creating a CRL,
        // the Extensions field is ignored, see ExtraExtensions.
        Extensions []pkix.Extension

        // ExtraExtensions contains any additional extensions to add directly to
        // the CRL.
        ExtraExtensions []pkix.Extension
}

// CreateRevocationList creates a new X.509 v2 Certificate Revocation List,
// according to RFC 5280, based on template.
//
// The CRL is signed by priv which should be the private key associated with
// the public key in the issuer certificate.
//
// The issuer may not be nil, and the crlSign bit must be set in KeyUsage in
// order to use it as a CRL issuer.
//
// The issuer distinguished name CRL field and authority key identifier
// extension are populated using the issuer certificate. issuer must have
// SubjectKeyId set.
func CreateRevocationList(rand io.Reader, template *RevocationList, issuer *Certificate, priv crypto.Signer) ([]byte, error) {
        if template == nil {
                return nil, errors.New("x509: template can not be nil")
        }
        if issuer == nil {
                return nil, errors.New("x509: issuer can not be nil")
        }
        if (issuer.KeyUsage & KeyUsageCRLSign) == 0 {
                return nil, errors.New("x509: issuer must have the crlSign key usage bit set")
        }
        if len(issuer.SubjectKeyId) == 0 {
                return nil, errors.New("x509: issuer certificate doesn't contain a subject key identifier")
        }
        if template.NextUpdate.Before(template.ThisUpdate) {
                return nil, errors.New("x509: template.ThisUpdate is after template.NextUpdate")
        }
        if template.Number == nil {
                return nil, errors.New("x509: template contains nil Number field")
        }

        hashFunc, signatureAlgorithm, err := signingParamsForPublicKey(priv.Public(), template.SignatureAlgorithm)
        if err != nil {
                return nil, err
        }

        // Force revocation times to UTC per RFC 5280.
        revokedCertsUTC := make([]pkix.RevokedCertificate, len(template.RevokedCertificates))
        for i, rc := range template.RevokedCertificates {
                rc.RevocationTime = rc.RevocationTime.UTC()
                revokedCertsUTC[i] = rc
        }

        aki, err := asn1.Marshal(authKeyId{Id: issuer.SubjectKeyId})
        if err != nil {
                return nil, err
        }
        crlNum, err := asn1.Marshal(template.Number)
        if err != nil {
                return nil, err
        }

        tbsCertList := pkix.TBSCertificateList{
                Version:    1, // v2
                Signature:  signatureAlgorithm,
                Issuer:     issuer.Subject.ToRDNSequence(),
                ThisUpdate: template.ThisUpdate.UTC(),
                NextUpdate: template.NextUpdate.UTC(),
                Extensions: []pkix.Extension{
                        {
                                Id:    oidExtensionAuthorityKeyId,
                                Value: aki,
                        },
                        {
                                Id:    oidExtensionCRLNumber,
                                Value: crlNum,
                        },
                },
        }
        if len(revokedCertsUTC) > 0 {
                tbsCertList.RevokedCertificates = revokedCertsUTC
        }

        if len(template.ExtraExtensions) > 0 {
                tbsCertList.Extensions = append(tbsCertList.Extensions, template.ExtraExtensions...)
        }

        tbsCertListContents, err := asn1.Marshal(tbsCertList)
        if err != nil {
                return nil, err
        }

        input := tbsCertListContents
        if hashFunc != 0 {
                h := hashFunc.New()
                h.Write(tbsCertListContents)
                input = h.Sum(nil)
        }
        var signerOpts crypto.SignerOpts = hashFunc
        if template.SignatureAlgorithm.isRSAPSS() {
                signerOpts = &rsa.PSSOptions{
                        SaltLength: rsa.PSSSaltLengthEqualsHash,
                        Hash:       hashFunc,
                }
        }

        signature, err := priv.Sign(rand, input, signerOpts)
        if err != nil {
                return nil, err
        }

        return asn1.Marshal(pkix.CertificateList{
                TBSCertList:        tbsCertList,
                SignatureAlgorithm: signatureAlgorithm,
                SignatureValue:     asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
        })
}

// CheckSignatureFrom verifies that the signature on rl is a valid signature
// from issuer.
func (rl *RevocationList) CheckSignatureFrom(parent *Certificate) error {
        if parent.Version == 3 && !parent.BasicConstraintsValid ||
                parent.BasicConstraintsValid && !parent.IsCA {
                return ConstraintViolationError{}
        }

        if parent.KeyUsage != 0 && parent.KeyUsage&KeyUsageCRLSign == 0 {
                return ConstraintViolationError{}
        }

        if parent.PublicKeyAlgorithm == UnknownPublicKeyAlgorithm {
                return ErrUnsupportedAlgorithm
        }

        return parent.CheckSignature(rl.SignatureAlgorithm, rl.RawTBSRevocationList, rl.Signature)
}