// Copyright 2010 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 tls import ( "crypto" "crypto/aes" "crypto/cipher" "crypto/des" "crypto/hmac" "crypto/rc4" "crypto/sha1" "crypto/sha256" "crypto/x509" "hash" "internal/x/crypto/chacha20poly1305" ) // a keyAgreement implements the client and server side of a TLS key agreement // protocol by generating and processing key exchange messages. type keyAgreement interface { // On the server side, the first two methods are called in order. // In the case that the key agreement protocol doesn't use a // ServerKeyExchange message, generateServerKeyExchange can return nil, // nil. generateServerKeyExchange(*Config, *Certificate, *clientHelloMsg, *serverHelloMsg) (*serverKeyExchangeMsg, error) processClientKeyExchange(*Config, *Certificate, *clientKeyExchangeMsg, uint16) ([]byte, error) // On the client side, the next two methods are called in order. // This method may not be called if the server doesn't send a // ServerKeyExchange message. processServerKeyExchange(*Config, *clientHelloMsg, *serverHelloMsg, *x509.Certificate, *serverKeyExchangeMsg) error generateClientKeyExchange(*Config, *clientHelloMsg, *x509.Certificate) ([]byte, *clientKeyExchangeMsg, error) } const ( // suiteECDH indicates that the cipher suite involves elliptic curve // Diffie-Hellman. This means that it should only be selected when the // client indicates that it supports ECC with a curve and point format // that we're happy with. suiteECDHE = 1 << iota // suiteECDSA indicates that the cipher suite involves an ECDSA // signature and therefore may only be selected when the server's // certificate is ECDSA. If this is not set then the cipher suite is // RSA based. suiteECDSA // suiteTLS12 indicates that the cipher suite should only be advertised // and accepted when using TLS 1.2. suiteTLS12 // suiteSHA384 indicates that the cipher suite uses SHA384 as the // handshake hash. suiteSHA384 // suiteDefaultOff indicates that this cipher suite is not included by // default. suiteDefaultOff ) // A cipherSuite is a specific combination of key agreement, cipher and MAC function. type cipherSuite struct { id uint16 // the lengths, in bytes, of the key material needed for each component. keyLen int macLen int ivLen int ka func(version uint16) keyAgreement // flags is a bitmask of the suite* values, above. flags int cipher func(key, iv []byte, isRead bool) interface{} mac func(version uint16, macKey []byte) macFunction aead func(key, fixedNonce []byte) aead } var cipherSuites = []*cipherSuite{ // Ciphersuite order is chosen so that ECDHE comes before plain RSA and // AEADs are the top preference. {TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305, 32, 0, 12, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadChaCha20Poly1305}, {TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305, 32, 0, 12, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12, nil, nil, aeadChaCha20Poly1305}, {TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadAESGCM}, {TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12, nil, nil, aeadAESGCM}, {TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM}, {TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM}, {TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil}, {TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil}, {TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil}, {TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil}, {TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil}, {TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil}, {TLS_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, rsaKA, suiteTLS12, nil, nil, aeadAESGCM}, {TLS_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, rsaKA, suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM}, {TLS_RSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, rsaKA, suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil}, {TLS_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil}, {TLS_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil}, {TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, ecdheRSAKA, suiteECDHE, cipher3DES, macSHA1, nil}, {TLS_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, rsaKA, 0, cipher3DES, macSHA1, nil}, // RC4-based cipher suites are disabled by default. {TLS_RSA_WITH_RC4_128_SHA, 16, 20, 0, rsaKA, suiteDefaultOff, cipherRC4, macSHA1, nil}, {TLS_ECDHE_RSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheRSAKA, suiteECDHE | suiteDefaultOff, cipherRC4, macSHA1, nil}, {TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteDefaultOff, cipherRC4, macSHA1, nil}, } // A cipherSuiteTLS13 defines only the pair of the AEAD algorithm and hash // algorithm to be used with HKDF. See RFC 8446, Appendix B.4. type cipherSuiteTLS13 struct { id uint16 keyLen int aead func(key, fixedNonce []byte) aead hash crypto.Hash } var cipherSuitesTLS13 = []*cipherSuiteTLS13{ {TLS_AES_128_GCM_SHA256, 16, aeadAESGCMTLS13, crypto.SHA256}, {TLS_CHACHA20_POLY1305_SHA256, 32, aeadChaCha20Poly1305, crypto.SHA256}, {TLS_AES_256_GCM_SHA384, 32, aeadAESGCMTLS13, crypto.SHA384}, } func cipherRC4(key, iv []byte, isRead bool) interface{} { cipher, _ := rc4.NewCipher(key) return cipher } func cipher3DES(key, iv []byte, isRead bool) interface{} { block, _ := des.NewTripleDESCipher(key) if isRead { return cipher.NewCBCDecrypter(block, iv) } return cipher.NewCBCEncrypter(block, iv) } func cipherAES(key, iv []byte, isRead bool) interface{} { block, _ := aes.NewCipher(key) if isRead { return cipher.NewCBCDecrypter(block, iv) } return cipher.NewCBCEncrypter(block, iv) } // macSHA1 returns a macFunction for the given protocol version. func macSHA1(version uint16, key []byte) macFunction { if version == VersionSSL30 { mac := ssl30MAC{ h: sha1.New(), key: make([]byte, len(key)), } copy(mac.key, key) return mac } return tls10MAC{h: hmac.New(newConstantTimeHash(sha1.New), key)} } // macSHA256 returns a SHA-256 based MAC. These are only supported in TLS 1.2 // so the given version is ignored. func macSHA256(version uint16, key []byte) macFunction { return tls10MAC{h: hmac.New(sha256.New, key)} } type macFunction interface { // Size returns the length of the MAC. Size() int // MAC appends the MAC of (seq, header, data) to out. The extra data is fed // into the MAC after obtaining the result to normalize timing. The result // is only valid until the next invocation of MAC as the buffer is reused. MAC(seq, header, data, extra []byte) []byte } type aead interface { cipher.AEAD // explicitNonceLen returns the number of bytes of explicit nonce // included in each record. This is eight for older AEADs and // zero for modern ones. explicitNonceLen() int } const ( aeadNonceLength = 12 noncePrefixLength = 4 ) // prefixNonceAEAD wraps an AEAD and prefixes a fixed portion of the nonce to // each call. type prefixNonceAEAD struct { // nonce contains the fixed part of the nonce in the first four bytes. nonce [aeadNonceLength]byte aead cipher.AEAD } func (f *prefixNonceAEAD) NonceSize() int { return aeadNonceLength - noncePrefixLength } func (f *prefixNonceAEAD) Overhead() int { return f.aead.Overhead() } func (f *prefixNonceAEAD) explicitNonceLen() int { return f.NonceSize() } func (f *prefixNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte { copy(f.nonce[4:], nonce) return f.aead.Seal(out, f.nonce[:], plaintext, additionalData) } func (f *prefixNonceAEAD) Open(out, nonce, ciphertext, additionalData []byte) ([]byte, error) { copy(f.nonce[4:], nonce) return f.aead.Open(out, f.nonce[:], ciphertext, additionalData) } // xoredNonceAEAD wraps an AEAD by XORing in a fixed pattern to the nonce // before each call. type xorNonceAEAD struct { nonceMask [aeadNonceLength]byte aead cipher.AEAD } func (f *xorNonceAEAD) NonceSize() int { return 8 } // 64-bit sequence number func (f *xorNonceAEAD) Overhead() int { return f.aead.Overhead() } func (f *xorNonceAEAD) explicitNonceLen() int { return 0 } func (f *xorNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte { for i, b := range nonce { f.nonceMask[4+i] ^= b } result := f.aead.Seal(out, f.nonceMask[:], plaintext, additionalData) for i, b := range nonce { f.nonceMask[4+i] ^= b } return result } func (f *xorNonceAEAD) Open(out, nonce, ciphertext, additionalData []byte) ([]byte, error) { for i, b := range nonce { f.nonceMask[4+i] ^= b } result, err := f.aead.Open(out, f.nonceMask[:], ciphertext, additionalData) for i, b := range nonce { f.nonceMask[4+i] ^= b } return result, err } func aeadAESGCM(key, noncePrefix []byte) aead { if len(noncePrefix) != noncePrefixLength { panic("tls: internal error: wrong nonce length") } aes, err := aes.NewCipher(key) if err != nil { panic(err) } aead, err := cipher.NewGCM(aes) if err != nil { panic(err) } ret := &prefixNonceAEAD{aead: aead} copy(ret.nonce[:], noncePrefix) return ret } func aeadAESGCMTLS13(key, nonceMask []byte) aead { if len(nonceMask) != aeadNonceLength { panic("tls: internal error: wrong nonce length") } aes, err := aes.NewCipher(key) if err != nil { panic(err) } aead, err := cipher.NewGCM(aes) if err != nil { panic(err) } ret := &xorNonceAEAD{aead: aead} copy(ret.nonceMask[:], nonceMask) return ret } func aeadChaCha20Poly1305(key, nonceMask []byte) aead { if len(nonceMask) != aeadNonceLength { panic("tls: internal error: wrong nonce length") } aead, err := chacha20poly1305.New(key) if err != nil { panic(err) } ret := &xorNonceAEAD{aead: aead} copy(ret.nonceMask[:], nonceMask) return ret } // ssl30MAC implements the SSLv3 MAC function, as defined in // www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 5.2.3.1 type ssl30MAC struct { h hash.Hash key []byte buf []byte } func (s ssl30MAC) Size() int { return s.h.Size() } var ssl30Pad1 = [48]byte{0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36} var ssl30Pad2 = [48]byte{0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c} // MAC does not offer constant timing guarantees for SSL v3.0, since it's deemed // useless considering the similar, protocol-level POODLE vulnerability. func (s ssl30MAC) MAC(seq, header, data, extra []byte) []byte { padLength := 48 if s.h.Size() == 20 { padLength = 40 } s.h.Reset() s.h.Write(s.key) s.h.Write(ssl30Pad1[:padLength]) s.h.Write(seq) s.h.Write(header[:1]) s.h.Write(header[3:5]) s.h.Write(data) s.buf = s.h.Sum(s.buf[:0]) s.h.Reset() s.h.Write(s.key) s.h.Write(ssl30Pad2[:padLength]) s.h.Write(s.buf) return s.h.Sum(s.buf[:0]) } type constantTimeHash interface { hash.Hash ConstantTimeSum(b []byte) []byte } // cthWrapper wraps any hash.Hash that implements ConstantTimeSum, and replaces // with that all calls to Sum. It's used to obtain a ConstantTimeSum-based HMAC. type cthWrapper struct { h constantTimeHash } func (c *cthWrapper) Size() int { return c.h.Size() } func (c *cthWrapper) BlockSize() int { return c.h.BlockSize() } func (c *cthWrapper) Reset() { c.h.Reset() } func (c *cthWrapper) Write(p []byte) (int, error) { return c.h.Write(p) } func (c *cthWrapper) Sum(b []byte) []byte { return c.h.ConstantTimeSum(b) } func newConstantTimeHash(h func() hash.Hash) func() hash.Hash { return func() hash.Hash { return &cthWrapper{h().(constantTimeHash)} } } // tls10MAC implements the TLS 1.0 MAC function. RFC 2246, Section 6.2.3. type tls10MAC struct { h hash.Hash buf []byte } func (s tls10MAC) Size() int { return s.h.Size() } // MAC is guaranteed to take constant time, as long as // len(seq)+len(header)+len(data)+len(extra) is constant. extra is not fed into // the MAC, but is only provided to make the timing profile constant. func (s tls10MAC) MAC(seq, header, data, extra []byte) []byte { s.h.Reset() s.h.Write(seq) s.h.Write(header) s.h.Write(data) res := s.h.Sum(s.buf[:0]) if extra != nil { s.h.Write(extra) } return res } func rsaKA(version uint16) keyAgreement { return rsaKeyAgreement{} } func ecdheECDSAKA(version uint16) keyAgreement { return &ecdheKeyAgreement{ isRSA: false, version: version, } } func ecdheRSAKA(version uint16) keyAgreement { return &ecdheKeyAgreement{ isRSA: true, version: version, } } // mutualCipherSuite returns a cipherSuite given a list of supported // ciphersuites and the id requested by the peer. func mutualCipherSuite(have []uint16, want uint16) *cipherSuite { for _, id := range have { if id == want { return cipherSuiteByID(id) } } return nil } func cipherSuiteByID(id uint16) *cipherSuite { for _, cipherSuite := range cipherSuites { if cipherSuite.id == id { return cipherSuite } } return nil } func mutualCipherSuiteTLS13(have []uint16, want uint16) *cipherSuiteTLS13 { for _, id := range have { if id == want { return cipherSuiteTLS13ByID(id) } } return nil } func cipherSuiteTLS13ByID(id uint16) *cipherSuiteTLS13 { for _, cipherSuite := range cipherSuitesTLS13 { if cipherSuite.id == id { return cipherSuite } } return nil } // A list of cipher suite IDs that are, or have been, implemented by this // package. // // Taken from https://www.iana.org/assignments/tls-parameters/tls-parameters.xml const ( // TLS 1.0 - 1.2 cipher suites. TLS_RSA_WITH_RC4_128_SHA uint16 = 0x0005 TLS_RSA_WITH_3DES_EDE_CBC_SHA uint16 = 0x000a TLS_RSA_WITH_AES_128_CBC_SHA uint16 = 0x002f TLS_RSA_WITH_AES_256_CBC_SHA uint16 = 0x0035 TLS_RSA_WITH_AES_128_CBC_SHA256 uint16 = 0x003c TLS_RSA_WITH_AES_128_GCM_SHA256 uint16 = 0x009c TLS_RSA_WITH_AES_256_GCM_SHA384 uint16 = 0x009d TLS_ECDHE_ECDSA_WITH_RC4_128_SHA uint16 = 0xc007 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA uint16 = 0xc009 TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA uint16 = 0xc00a TLS_ECDHE_RSA_WITH_RC4_128_SHA uint16 = 0xc011 TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA uint16 = 0xc012 TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA uint16 = 0xc013 TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA uint16 = 0xc014 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 uint16 = 0xc023 TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 uint16 = 0xc027 TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 uint16 = 0xc02f TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 uint16 = 0xc02b TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 uint16 = 0xc030 TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 uint16 = 0xc02c TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305 uint16 = 0xcca8 TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305 uint16 = 0xcca9 // TLS 1.3 cipher suites. TLS_AES_128_GCM_SHA256 uint16 = 0x1301 TLS_AES_256_GCM_SHA384 uint16 = 0x1302 TLS_CHACHA20_POLY1305_SHA256 uint16 = 0x1303 // TLS_FALLBACK_SCSV isn't a standard cipher suite but an indicator // that the client is doing version fallback. See RFC 7507. TLS_FALLBACK_SCSV uint16 = 0x5600 )