1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353
|
/*-
* Copyright 2014 Square Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package jose
import (
"crypto/aes"
"crypto/cipher"
"crypto/hmac"
"crypto/rand"
"crypto/sha256"
"crypto/sha512"
"crypto/subtle"
"errors"
"hash"
"io"
"gopkg.in/square/go-jose.v1/cipher"
)
// Random reader (stubbed out in tests)
var randReader = rand.Reader
// Dummy key cipher for shared symmetric key mode
type symmetricKeyCipher struct {
key []byte // Pre-shared content-encryption key
}
// Signer/verifier for MAC modes
type symmetricMac struct {
key []byte
}
// Input/output from an AEAD operation
type aeadParts struct {
iv, ciphertext, tag []byte
}
// A content cipher based on an AEAD construction
type aeadContentCipher struct {
keyBytes int
authtagBytes int
getAead func(key []byte) (cipher.AEAD, error)
}
// Random key generator
type randomKeyGenerator struct {
size int
}
// Static key generator
type staticKeyGenerator struct {
key []byte
}
// Create a new content cipher based on AES-GCM
func newAESGCM(keySize int) contentCipher {
return &aeadContentCipher{
keyBytes: keySize,
authtagBytes: 16,
getAead: func(key []byte) (cipher.AEAD, error) {
aes, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
return cipher.NewGCM(aes)
},
}
}
// Create a new content cipher based on AES-CBC+HMAC
func newAESCBC(keySize int) contentCipher {
return &aeadContentCipher{
keyBytes: keySize * 2,
authtagBytes: 16,
getAead: func(key []byte) (cipher.AEAD, error) {
return josecipher.NewCBCHMAC(key, aes.NewCipher)
},
}
}
// Get an AEAD cipher object for the given content encryption algorithm
func getContentCipher(alg ContentEncryption) contentCipher {
switch alg {
case A128GCM:
return newAESGCM(16)
case A192GCM:
return newAESGCM(24)
case A256GCM:
return newAESGCM(32)
case A128CBC_HS256:
return newAESCBC(16)
case A192CBC_HS384:
return newAESCBC(24)
case A256CBC_HS512:
return newAESCBC(32)
default:
return nil
}
}
// newSymmetricRecipient creates a JWE encrypter based on AES-GCM key wrap.
func newSymmetricRecipient(keyAlg KeyAlgorithm, key []byte) (recipientKeyInfo, error) {
switch keyAlg {
case DIRECT, A128GCMKW, A192GCMKW, A256GCMKW, A128KW, A192KW, A256KW:
default:
return recipientKeyInfo{}, ErrUnsupportedAlgorithm
}
return recipientKeyInfo{
keyAlg: keyAlg,
keyEncrypter: &symmetricKeyCipher{
key: key,
},
}, nil
}
// newSymmetricSigner creates a recipientSigInfo based on the given key.
func newSymmetricSigner(sigAlg SignatureAlgorithm, key []byte) (recipientSigInfo, error) {
// Verify that key management algorithm is supported by this encrypter
switch sigAlg {
case HS256, HS384, HS512:
default:
return recipientSigInfo{}, ErrUnsupportedAlgorithm
}
return recipientSigInfo{
sigAlg: sigAlg,
signer: &symmetricMac{
key: key,
},
}, nil
}
// Generate a random key for the given content cipher
func (ctx randomKeyGenerator) genKey() ([]byte, rawHeader, error) {
key := make([]byte, ctx.size)
_, err := io.ReadFull(randReader, key)
if err != nil {
return nil, rawHeader{}, err
}
return key, rawHeader{}, nil
}
// Key size for random generator
func (ctx randomKeyGenerator) keySize() int {
return ctx.size
}
// Generate a static key (for direct mode)
func (ctx staticKeyGenerator) genKey() ([]byte, rawHeader, error) {
cek := make([]byte, len(ctx.key))
copy(cek, ctx.key)
return cek, rawHeader{}, nil
}
// Key size for static generator
func (ctx staticKeyGenerator) keySize() int {
return len(ctx.key)
}
// Get key size for this cipher
func (ctx aeadContentCipher) keySize() int {
return ctx.keyBytes
}
// Encrypt some data
func (ctx aeadContentCipher) encrypt(key, aad, pt []byte) (*aeadParts, error) {
// Get a new AEAD instance
aead, err := ctx.getAead(key)
if err != nil {
return nil, err
}
// Initialize a new nonce
iv := make([]byte, aead.NonceSize())
_, err = io.ReadFull(randReader, iv)
if err != nil {
return nil, err
}
ciphertextAndTag := aead.Seal(nil, iv, pt, aad)
offset := len(ciphertextAndTag) - ctx.authtagBytes
return &aeadParts{
iv: iv,
ciphertext: ciphertextAndTag[:offset],
tag: ciphertextAndTag[offset:],
}, nil
}
// Decrypt some data
func (ctx aeadContentCipher) decrypt(key, aad []byte, parts *aeadParts) ([]byte, error) {
aead, err := ctx.getAead(key)
if err != nil {
return nil, err
}
if len(parts.iv) < aead.NonceSize() || len(parts.tag) < ctx.authtagBytes {
return nil, ErrCryptoFailure
}
return aead.Open(nil, parts.iv, append(parts.ciphertext, parts.tag...), aad)
}
// Encrypt the content encryption key.
func (ctx *symmetricKeyCipher) encryptKey(cek []byte, alg KeyAlgorithm) (recipientInfo, error) {
switch alg {
case DIRECT:
return recipientInfo{
header: &rawHeader{},
}, nil
case A128GCMKW, A192GCMKW, A256GCMKW:
aead := newAESGCM(len(ctx.key))
parts, err := aead.encrypt(ctx.key, []byte{}, cek)
if err != nil {
return recipientInfo{}, err
}
return recipientInfo{
header: &rawHeader{
Iv: newBuffer(parts.iv),
Tag: newBuffer(parts.tag),
},
encryptedKey: parts.ciphertext,
}, nil
case A128KW, A192KW, A256KW:
block, err := aes.NewCipher(ctx.key)
if err != nil {
return recipientInfo{}, err
}
jek, err := josecipher.KeyWrap(block, cek)
if err != nil {
return recipientInfo{}, err
}
return recipientInfo{
encryptedKey: jek,
header: &rawHeader{},
}, nil
}
return recipientInfo{}, ErrUnsupportedAlgorithm
}
// Decrypt the content encryption key.
func (ctx *symmetricKeyCipher) decryptKey(headers rawHeader, recipient *recipientInfo, generator keyGenerator) ([]byte, error) {
switch KeyAlgorithm(headers.Alg) {
case DIRECT:
cek := make([]byte, len(ctx.key))
copy(cek, ctx.key)
return cek, nil
case A128GCMKW, A192GCMKW, A256GCMKW:
aead := newAESGCM(len(ctx.key))
parts := &aeadParts{
iv: headers.Iv.bytes(),
ciphertext: recipient.encryptedKey,
tag: headers.Tag.bytes(),
}
cek, err := aead.decrypt(ctx.key, []byte{}, parts)
if err != nil {
return nil, err
}
return cek, nil
case A128KW, A192KW, A256KW:
block, err := aes.NewCipher(ctx.key)
if err != nil {
return nil, err
}
cek, err := josecipher.KeyUnwrap(block, recipient.encryptedKey)
if err != nil {
return nil, err
}
return cek, nil
}
return nil, ErrUnsupportedAlgorithm
}
// Sign the given payload
func (ctx symmetricMac) signPayload(payload []byte, alg SignatureAlgorithm) (Signature, error) {
mac, err := ctx.hmac(payload, alg)
if err != nil {
return Signature{}, errors.New("square/go-jose: failed to compute hmac")
}
return Signature{
Signature: mac,
protected: &rawHeader{},
}, nil
}
// Verify the given payload
func (ctx symmetricMac) verifyPayload(payload []byte, mac []byte, alg SignatureAlgorithm) error {
expected, err := ctx.hmac(payload, alg)
if err != nil {
return errors.New("square/go-jose: failed to compute hmac")
}
if len(mac) != len(expected) {
return errors.New("square/go-jose: invalid hmac")
}
match := subtle.ConstantTimeCompare(mac, expected)
if match != 1 {
return errors.New("square/go-jose: invalid hmac")
}
return nil
}
// Compute the HMAC based on the given alg value
func (ctx symmetricMac) hmac(payload []byte, alg SignatureAlgorithm) ([]byte, error) {
var hash func() hash.Hash
switch alg {
case HS256:
hash = sha256.New
case HS384:
hash = sha512.New384
case HS512:
hash = sha512.New
default:
return nil, ErrUnsupportedAlgorithm
}
hmac := hmac.New(hash, ctx.key)
// According to documentation, Write() on hash never fails
_, _ = hmac.Write(payload)
return hmac.Sum(nil), nil
}
|