1 // Copyright 2010 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package tls 6 7 import ( 8 "crypto/aes" 9 "crypto/cipher" 10 "crypto/des" 11 "crypto/hmac" 12 "crypto/rc4" 13 "crypto/sha1" 14 "crypto/x509" 15 "hash" 16 ) 17 18 // a keyAgreement implements the client and server side of a TLS key agreement 19 // protocol by generating and processing key exchange messages. 20 type keyAgreement interface { 21 // On the server side, the first two methods are called in order. 22 23 // In the case that the key agreement protocol doesn't use a 24 // ServerKeyExchange message, generateServerKeyExchange can return nil, 25 // nil. 26 generateServerKeyExchange(*Config, *Certificate, *clientHelloMsg, *serverHelloMsg) (*serverKeyExchangeMsg, error) 27 processClientKeyExchange(*Config, *Certificate, *clientKeyExchangeMsg, uint16) ([]byte, error) 28 29 // On the client side, the next two methods are called in order. 30 31 // This method may not be called if the server doesn't send a 32 // ServerKeyExchange message. 33 processServerKeyExchange(*Config, *clientHelloMsg, *serverHelloMsg, *x509.Certificate, *serverKeyExchangeMsg) error 34 generateClientKeyExchange(*Config, *clientHelloMsg, *x509.Certificate) ([]byte, *clientKeyExchangeMsg, error) 35 } 36 37 const ( 38 // suiteECDH indicates that the cipher suite involves elliptic curve 39 // Diffie-Hellman. This means that it should only be selected when the 40 // client indicates that it supports ECC with a curve and point format 41 // that we're happy with. 42 suiteECDHE = 1 << iota 43 // suiteECDSA indicates that the cipher suite involves an ECDSA 44 // signature and therefore may only be selected when the server's 45 // certificate is ECDSA. If this is not set then the cipher suite is 46 // RSA based. 47 suiteECDSA 48 // suiteTLS12 indicates that the cipher suite should only be advertised 49 // and accepted when using TLS 1.2. 50 suiteTLS12 51 // suiteSHA384 indicates that the cipher suite uses SHA384 as the 52 // handshake hash. 53 suiteSHA384 54 // suiteDefaultOff indicates that this cipher suite is not included by 55 // default. 56 suiteDefaultOff 57 ) 58 59 // A cipherSuite is a specific combination of key agreement, cipher and MAC 60 // function. All cipher suites currently assume RSA key agreement. 61 type cipherSuite struct { 62 id uint16 63 // the lengths, in bytes, of the key material needed for each component. 64 keyLen int 65 macLen int 66 ivLen int 67 ka func(version uint16) keyAgreement 68 // flags is a bitmask of the suite* values, above. 69 flags int 70 cipher func(key, iv []byte, isRead bool) interface{} 71 mac func(version uint16, macKey []byte) macFunction 72 aead func(key, fixedNonce []byte) cipher.AEAD 73 } 74 75 var cipherSuites = []*cipherSuite{ 76 // Ciphersuite order is chosen so that ECDHE comes before plain RSA 77 // and RC4 comes before AES (because of the Lucky13 attack). 78 {TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadAESGCM}, 79 {TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12, nil, nil, aeadAESGCM}, 80 {TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM}, 81 {TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM}, 82 {TLS_ECDHE_RSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheRSAKA, suiteECDHE | suiteDefaultOff, cipherRC4, macSHA1, nil}, 83 {TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteDefaultOff, cipherRC4, macSHA1, nil}, 84 {TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil}, 85 {TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil}, 86 {TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil}, 87 {TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil}, 88 {TLS_RSA_WITH_RC4_128_SHA, 16, 20, 0, rsaKA, suiteDefaultOff, cipherRC4, macSHA1, nil}, 89 {TLS_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil}, 90 {TLS_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil}, 91 {TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, ecdheRSAKA, suiteECDHE, cipher3DES, macSHA1, nil}, 92 {TLS_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, rsaKA, 0, cipher3DES, macSHA1, nil}, 93 } 94 95 func cipherRC4(key, iv []byte, isRead bool) interface{} { 96 cipher, _ := rc4.NewCipher(key) 97 return cipher 98 } 99 100 func cipher3DES(key, iv []byte, isRead bool) interface{} { 101 block, _ := des.NewTripleDESCipher(key) 102 if isRead { 103 return cipher.NewCBCDecrypter(block, iv) 104 } 105 return cipher.NewCBCEncrypter(block, iv) 106 } 107 108 func cipherAES(key, iv []byte, isRead bool) interface{} { 109 block, _ := aes.NewCipher(key) 110 if isRead { 111 return cipher.NewCBCDecrypter(block, iv) 112 } 113 return cipher.NewCBCEncrypter(block, iv) 114 } 115 116 // macSHA1 returns a macFunction for the given protocol version. 117 func macSHA1(version uint16, key []byte) macFunction { 118 if version == VersionSSL30 { 119 mac := ssl30MAC{ 120 h: sha1.New(), 121 key: make([]byte, len(key)), 122 } 123 copy(mac.key, key) 124 return mac 125 } 126 return tls10MAC{hmac.New(sha1.New, key)} 127 } 128 129 type macFunction interface { 130 Size() int 131 MAC(digestBuf, seq, header, data []byte) []byte 132 } 133 134 // fixedNonceAEAD wraps an AEAD and prefixes a fixed portion of the nonce to 135 // each call. 136 type fixedNonceAEAD struct { 137 // sealNonce and openNonce are buffers where the larger nonce will be 138 // constructed. Since a seal and open operation may be running 139 // concurrently, there is a separate buffer for each. 140 sealNonce, openNonce []byte 141 aead cipher.AEAD 142 } 143 144 func (f *fixedNonceAEAD) NonceSize() int { return 8 } 145 func (f *fixedNonceAEAD) Overhead() int { return f.aead.Overhead() } 146 147 func (f *fixedNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte { 148 copy(f.sealNonce[len(f.sealNonce)-8:], nonce) 149 return f.aead.Seal(out, f.sealNonce, plaintext, additionalData) 150 } 151 152 func (f *fixedNonceAEAD) Open(out, nonce, plaintext, additionalData []byte) ([]byte, error) { 153 copy(f.openNonce[len(f.openNonce)-8:], nonce) 154 return f.aead.Open(out, f.openNonce, plaintext, additionalData) 155 } 156 157 func aeadAESGCM(key, fixedNonce []byte) cipher.AEAD { 158 aes, err := aes.NewCipher(key) 159 if err != nil { 160 panic(err) 161 } 162 aead, err := cipher.NewGCM(aes) 163 if err != nil { 164 panic(err) 165 } 166 167 nonce1, nonce2 := make([]byte, 12), make([]byte, 12) 168 copy(nonce1, fixedNonce) 169 copy(nonce2, fixedNonce) 170 171 return &fixedNonceAEAD{nonce1, nonce2, aead} 172 } 173 174 // ssl30MAC implements the SSLv3 MAC function, as defined in 175 // www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 5.2.3.1 176 type ssl30MAC struct { 177 h hash.Hash 178 key []byte 179 } 180 181 func (s ssl30MAC) Size() int { 182 return s.h.Size() 183 } 184 185 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} 186 187 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} 188 189 func (s ssl30MAC) MAC(digestBuf, seq, header, data []byte) []byte { 190 padLength := 48 191 if s.h.Size() == 20 { 192 padLength = 40 193 } 194 195 s.h.Reset() 196 s.h.Write(s.key) 197 s.h.Write(ssl30Pad1[:padLength]) 198 s.h.Write(seq) 199 s.h.Write(header[:1]) 200 s.h.Write(header[3:5]) 201 s.h.Write(data) 202 digestBuf = s.h.Sum(digestBuf[:0]) 203 204 s.h.Reset() 205 s.h.Write(s.key) 206 s.h.Write(ssl30Pad2[:padLength]) 207 s.h.Write(digestBuf) 208 return s.h.Sum(digestBuf[:0]) 209 } 210 211 // tls10MAC implements the TLS 1.0 MAC function. RFC 2246, section 6.2.3. 212 type tls10MAC struct { 213 h hash.Hash 214 } 215 216 func (s tls10MAC) Size() int { 217 return s.h.Size() 218 } 219 220 func (s tls10MAC) MAC(digestBuf, seq, header, data []byte) []byte { 221 s.h.Reset() 222 s.h.Write(seq) 223 s.h.Write(header) 224 s.h.Write(data) 225 return s.h.Sum(digestBuf[:0]) 226 } 227 228 func rsaKA(version uint16) keyAgreement { 229 return rsaKeyAgreement{} 230 } 231 232 func ecdheECDSAKA(version uint16) keyAgreement { 233 return &ecdheKeyAgreement{ 234 sigType: signatureECDSA, 235 version: version, 236 } 237 } 238 239 func ecdheRSAKA(version uint16) keyAgreement { 240 return &ecdheKeyAgreement{ 241 sigType: signatureRSA, 242 version: version, 243 } 244 } 245 246 // mutualCipherSuite returns a cipherSuite given a list of supported 247 // ciphersuites and the id requested by the peer. 248 func mutualCipherSuite(have []uint16, want uint16) *cipherSuite { 249 for _, id := range have { 250 if id == want { 251 for _, suite := range cipherSuites { 252 if suite.id == want { 253 return suite 254 } 255 } 256 return nil 257 } 258 } 259 return nil 260 } 261 262 // A list of the possible cipher suite ids. Taken from 263 // http://www.iana.org/assignments/tls-parameters/tls-parameters.xml 264 const ( 265 TLS_RSA_WITH_RC4_128_SHA uint16 = 0x0005 266 TLS_RSA_WITH_3DES_EDE_CBC_SHA uint16 = 0x000a 267 TLS_RSA_WITH_AES_128_CBC_SHA uint16 = 0x002f 268 TLS_RSA_WITH_AES_256_CBC_SHA uint16 = 0x0035 269 TLS_ECDHE_ECDSA_WITH_RC4_128_SHA uint16 = 0xc007 270 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA uint16 = 0xc009 271 TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA uint16 = 0xc00a 272 TLS_ECDHE_RSA_WITH_RC4_128_SHA uint16 = 0xc011 273 TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA uint16 = 0xc012 274 TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA uint16 = 0xc013 275 TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA uint16 = 0xc014 276 TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 uint16 = 0xc02f 277 TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 uint16 = 0xc02b 278 TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 uint16 = 0xc030 279 TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 uint16 = 0xc02c 280 281 // TLS_FALLBACK_SCSV isn't a standard cipher suite but an indicator 282 // that the client is doing version fallback. See 283 // https://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-00. 284 TLS_FALLBACK_SCSV uint16 = 0x5600 285 ) 286
