// 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/x509" "hash" ) // 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 ) // A cipherSuite is a specific combination of key agreement, cipher and MAC // function. All cipher suites currently assume RSA key agreement. 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) cipher.AEAD tls12Hash crypto.Hash } var cipherSuites = []*cipherSuite{ // Ciphersuite order is chosen so that ECDHE comes before plain RSA // and RC4 comes before AES (because of the Lucky13 attack). {TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadAESGCM, crypto.SHA256}, {TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12, nil, nil, aeadAESGCM, crypto.SHA256}, {TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadAESGCM, crypto.SHA384}, {TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12, nil, nil, aeadAESGCM, crypto.SHA384}, {TLS_ECDHE_RSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheRSAKA, suiteECDHE, cipherRC4, macSHA1, nil, crypto.SHA256}, {TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherRC4, macSHA1, nil, crypto.SHA256}, {TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil, crypto.SHA256}, {TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil, crypto.SHA256}, {TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil, crypto.SHA256}, {TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil, crypto.SHA256}, {TLS_RSA_WITH_RC4_128_SHA, 16, 20, 0, rsaKA, 0, cipherRC4, macSHA1, nil, crypto.SHA256}, {TLS_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil, crypto.SHA256}, {TLS_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil, crypto.SHA256}, {TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, ecdheRSAKA, suiteECDHE, cipher3DES, macSHA1, nil, crypto.SHA256}, {TLS_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, rsaKA, 0, cipher3DES, macSHA1, nil, crypto.SHA256}, } 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{hmac.New(sha1.New, key)} } type macFunction interface { Size() int MAC(digestBuf, seq, header, data []byte) []byte } // fixedNonceAEAD wraps an AEAD and prefixes a fixed portion of the nonce to // each call. type fixedNonceAEAD struct { // sealNonce and openNonce are buffers where the larger nonce will be // constructed. Since a seal and open operation may be running // concurrently, there is a separate buffer for each. sealNonce, openNonce []byte aead cipher.AEAD } func (f *fixedNonceAEAD) NonceSize() int { return 8 } func (f *fixedNonceAEAD) Overhead() int { return f.aead.Overhead() } func (f *fixedNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte { copy(f.sealNonce[len(f.sealNonce)-8:], nonce) return f.aead.Seal(out, f.sealNonce, plaintext, additionalData) } func (f *fixedNonceAEAD) Open(out, nonce, plaintext, additionalData []byte) ([]byte, error) { copy(f.openNonce[len(f.openNonce)-8:], nonce) return f.aead.Open(out, f.openNonce, plaintext, additionalData) } func aeadAESGCM(key, fixedNonce []byte) cipher.AEAD { aes, err := aes.NewCipher(key) if err != nil { panic(err) } aead, err := cipher.NewGCM(aes) if err != nil { panic(err) } nonce1, nonce2 := make([]byte, 12), make([]byte, 12) copy(nonce1, fixedNonce) copy(nonce2, fixedNonce) return &fixedNonceAEAD{nonce1, nonce2, aead} } // 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 } 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} func (s ssl30MAC) MAC(digestBuf, seq, header, data []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) digestBuf = s.h.Sum(digestBuf[:0]) s.h.Reset() s.h.Write(s.key) s.h.Write(ssl30Pad2[:padLength]) s.h.Write(digestBuf) return s.h.Sum(digestBuf[:0]) } // tls10MAC implements the TLS 1.0 MAC function. RFC 2246, section 6.2.3. type tls10MAC struct { h hash.Hash } func (s tls10MAC) Size() int { return s.h.Size() } func (s tls10MAC) MAC(digestBuf, seq, header, data []byte) []byte { s.h.Reset() s.h.Write(seq) s.h.Write(header) s.h.Write(data) return s.h.Sum(digestBuf[:0]) } func rsaKA(version uint16) keyAgreement { return rsaKeyAgreement{} } func ecdheECDSAKA(version uint16) keyAgreement { return &ecdheKeyAgreement{ sigType: signatureECDSA, version: version, } } func ecdheRSAKA(version uint16) keyAgreement { return &ecdheKeyAgreement{ sigType: signatureRSA, 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 { for _, suite := range cipherSuites { if suite.id == want { return suite } } return nil } } return nil } // A list of the possible cipher suite ids. Taken from // http://www.iana.org/assignments/tls-parameters/tls-parameters.xml const ( 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_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_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_FALLBACK_SCSV isn't a standard cipher suite but an indicator // that the client is doing version fallback. See // https://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-00. TLS_FALLBACK_SCSV uint16 = 0x5600 )