1// Copyright 2011 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 5package packet 6 7import ( 8 "bytes" 9 "crypto" 10 "crypto/dsa" 11 "crypto/ecdsa" 12 "crypto/elliptic" 13 "crypto/rsa" 14 "crypto/sha1" 15 _ "crypto/sha256" 16 _ "crypto/sha512" 17 "encoding/binary" 18 "fmt" 19 "hash" 20 "io" 21 "math/big" 22 "strconv" 23 "time" 24 25 "golang.org/x/crypto/openpgp/elgamal" 26 "golang.org/x/crypto/openpgp/errors" 27) 28 29var ( 30 // NIST curve P-256 31 oidCurveP256 []byte = []byte{0x2A, 0x86, 0x48, 0xCE, 0x3D, 0x03, 0x01, 0x07} 32 // NIST curve P-384 33 oidCurveP384 []byte = []byte{0x2B, 0x81, 0x04, 0x00, 0x22} 34 // NIST curve P-521 35 oidCurveP521 []byte = []byte{0x2B, 0x81, 0x04, 0x00, 0x23} 36) 37 38const maxOIDLength = 8 39 40// ecdsaKey stores the algorithm-specific fields for ECDSA keys. 41// as defined in RFC 6637, Section 9. 42type ecdsaKey struct { 43 // oid contains the OID byte sequence identifying the elliptic curve used 44 oid []byte 45 // p contains the elliptic curve point that represents the public key 46 p parsedMPI 47} 48 49// parseOID reads the OID for the curve as defined in RFC 6637, Section 9. 50func parseOID(r io.Reader) (oid []byte, err error) { 51 buf := make([]byte, maxOIDLength) 52 if _, err = readFull(r, buf[:1]); err != nil { 53 return 54 } 55 oidLen := buf[0] 56 if int(oidLen) > len(buf) { 57 err = errors.UnsupportedError("invalid oid length: " + strconv.Itoa(int(oidLen))) 58 return 59 } 60 oid = buf[:oidLen] 61 _, err = readFull(r, oid) 62 return 63} 64 65func (f *ecdsaKey) parse(r io.Reader) (err error) { 66 if f.oid, err = parseOID(r); err != nil { 67 return err 68 } 69 f.p.bytes, f.p.bitLength, err = readMPI(r) 70 return 71} 72 73func (f *ecdsaKey) serialize(w io.Writer) (err error) { 74 buf := make([]byte, maxOIDLength+1) 75 buf[0] = byte(len(f.oid)) 76 copy(buf[1:], f.oid) 77 if _, err = w.Write(buf[:len(f.oid)+1]); err != nil { 78 return 79 } 80 return writeMPIs(w, f.p) 81} 82 83func (f *ecdsaKey) newECDSA() (*ecdsa.PublicKey, error) { 84 var c elliptic.Curve 85 if bytes.Equal(f.oid, oidCurveP256) { 86 c = elliptic.P256() 87 } else if bytes.Equal(f.oid, oidCurveP384) { 88 c = elliptic.P384() 89 } else if bytes.Equal(f.oid, oidCurveP521) { 90 c = elliptic.P521() 91 } else { 92 return nil, errors.UnsupportedError(fmt.Sprintf("unsupported oid: %x", f.oid)) 93 } 94 x, y := elliptic.Unmarshal(c, f.p.bytes) 95 if x == nil { 96 return nil, errors.UnsupportedError("failed to parse EC point") 97 } 98 return &ecdsa.PublicKey{Curve: c, X: x, Y: y}, nil 99} 100 101func (f *ecdsaKey) byteLen() int { 102 return 1 + len(f.oid) + 2 + len(f.p.bytes) 103} 104 105type kdfHashFunction byte 106type kdfAlgorithm byte 107 108// ecdhKdf stores key derivation function parameters 109// used for ECDH encryption. See RFC 6637, Section 9. 110type ecdhKdf struct { 111 KdfHash kdfHashFunction 112 KdfAlgo kdfAlgorithm 113} 114 115func (f *ecdhKdf) parse(r io.Reader) (err error) { 116 buf := make([]byte, 1) 117 if _, err = readFull(r, buf); err != nil { 118 return 119 } 120 kdfLen := int(buf[0]) 121 if kdfLen < 3 { 122 return errors.UnsupportedError("Unsupported ECDH KDF length: " + strconv.Itoa(kdfLen)) 123 } 124 buf = make([]byte, kdfLen) 125 if _, err = readFull(r, buf); err != nil { 126 return 127 } 128 reserved := int(buf[0]) 129 f.KdfHash = kdfHashFunction(buf[1]) 130 f.KdfAlgo = kdfAlgorithm(buf[2]) 131 if reserved != 0x01 { 132 return errors.UnsupportedError("Unsupported KDF reserved field: " + strconv.Itoa(reserved)) 133 } 134 return 135} 136 137func (f *ecdhKdf) serialize(w io.Writer) (err error) { 138 buf := make([]byte, 4) 139 // See RFC 6637, Section 9, Algorithm-Specific Fields for ECDH keys. 140 buf[0] = byte(0x03) // Length of the following fields 141 buf[1] = byte(0x01) // Reserved for future extensions, must be 1 for now 142 buf[2] = byte(f.KdfHash) 143 buf[3] = byte(f.KdfAlgo) 144 _, err = w.Write(buf[:]) 145 return 146} 147 148func (f *ecdhKdf) byteLen() int { 149 return 4 150} 151 152// PublicKey represents an OpenPGP public key. See RFC 4880, section 5.5.2. 153type PublicKey struct { 154 CreationTime time.Time 155 PubKeyAlgo PublicKeyAlgorithm 156 PublicKey interface{} // *rsa.PublicKey, *dsa.PublicKey or *ecdsa.PublicKey 157 Fingerprint [20]byte 158 KeyId uint64 159 IsSubkey bool 160 161 n, e, p, q, g, y parsedMPI 162 163 // RFC 6637 fields 164 ec *ecdsaKey 165 ecdh *ecdhKdf 166} 167 168// signingKey provides a convenient abstraction over signature verification 169// for v3 and v4 public keys. 170type signingKey interface { 171 SerializeSignaturePrefix(io.Writer) 172 serializeWithoutHeaders(io.Writer) error 173} 174 175func fromBig(n *big.Int) parsedMPI { 176 return parsedMPI{ 177 bytes: n.Bytes(), 178 bitLength: uint16(n.BitLen()), 179 } 180} 181 182// NewRSAPublicKey returns a PublicKey that wraps the given rsa.PublicKey. 183func NewRSAPublicKey(creationTime time.Time, pub *rsa.PublicKey) *PublicKey { 184 pk := &PublicKey{ 185 CreationTime: creationTime, 186 PubKeyAlgo: PubKeyAlgoRSA, 187 PublicKey: pub, 188 n: fromBig(pub.N), 189 e: fromBig(big.NewInt(int64(pub.E))), 190 } 191 192 pk.setFingerPrintAndKeyId() 193 return pk 194} 195 196// NewDSAPublicKey returns a PublicKey that wraps the given dsa.PublicKey. 197func NewDSAPublicKey(creationTime time.Time, pub *dsa.PublicKey) *PublicKey { 198 pk := &PublicKey{ 199 CreationTime: creationTime, 200 PubKeyAlgo: PubKeyAlgoDSA, 201 PublicKey: pub, 202 p: fromBig(pub.P), 203 q: fromBig(pub.Q), 204 g: fromBig(pub.G), 205 y: fromBig(pub.Y), 206 } 207 208 pk.setFingerPrintAndKeyId() 209 return pk 210} 211 212// NewElGamalPublicKey returns a PublicKey that wraps the given elgamal.PublicKey. 213func NewElGamalPublicKey(creationTime time.Time, pub *elgamal.PublicKey) *PublicKey { 214 pk := &PublicKey{ 215 CreationTime: creationTime, 216 PubKeyAlgo: PubKeyAlgoElGamal, 217 PublicKey: pub, 218 p: fromBig(pub.P), 219 g: fromBig(pub.G), 220 y: fromBig(pub.Y), 221 } 222 223 pk.setFingerPrintAndKeyId() 224 return pk 225} 226 227func NewECDSAPublicKey(creationTime time.Time, pub *ecdsa.PublicKey) *PublicKey { 228 pk := &PublicKey{ 229 CreationTime: creationTime, 230 PubKeyAlgo: PubKeyAlgoECDSA, 231 PublicKey: pub, 232 ec: new(ecdsaKey), 233 } 234 235 switch pub.Curve { 236 case elliptic.P256(): 237 pk.ec.oid = oidCurveP256 238 case elliptic.P384(): 239 pk.ec.oid = oidCurveP384 240 case elliptic.P521(): 241 pk.ec.oid = oidCurveP521 242 default: 243 panic("unknown elliptic curve") 244 } 245 246 pk.ec.p.bytes = elliptic.Marshal(pub.Curve, pub.X, pub.Y) 247 pk.ec.p.bitLength = uint16(8 * len(pk.ec.p.bytes)) 248 249 pk.setFingerPrintAndKeyId() 250 return pk 251} 252 253func (pk *PublicKey) parse(r io.Reader) (err error) { 254 // RFC 4880, section 5.5.2 255 var buf [6]byte 256 _, err = readFull(r, buf[:]) 257 if err != nil { 258 return 259 } 260 if buf[0] != 4 { 261 return errors.UnsupportedError("public key version") 262 } 263 pk.CreationTime = time.Unix(int64(uint32(buf[1])<<24|uint32(buf[2])<<16|uint32(buf[3])<<8|uint32(buf[4])), 0) 264 pk.PubKeyAlgo = PublicKeyAlgorithm(buf[5]) 265 switch pk.PubKeyAlgo { 266 case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly: 267 err = pk.parseRSA(r) 268 case PubKeyAlgoDSA: 269 err = pk.parseDSA(r) 270 case PubKeyAlgoElGamal: 271 err = pk.parseElGamal(r) 272 case PubKeyAlgoECDSA: 273 pk.ec = new(ecdsaKey) 274 if err = pk.ec.parse(r); err != nil { 275 return err 276 } 277 pk.PublicKey, err = pk.ec.newECDSA() 278 case PubKeyAlgoECDH: 279 pk.ec = new(ecdsaKey) 280 if err = pk.ec.parse(r); err != nil { 281 return 282 } 283 pk.ecdh = new(ecdhKdf) 284 if err = pk.ecdh.parse(r); err != nil { 285 return 286 } 287 // The ECDH key is stored in an ecdsa.PublicKey for convenience. 288 pk.PublicKey, err = pk.ec.newECDSA() 289 default: 290 err = errors.UnsupportedError("public key type: " + strconv.Itoa(int(pk.PubKeyAlgo))) 291 } 292 if err != nil { 293 return 294 } 295 296 pk.setFingerPrintAndKeyId() 297 return 298} 299 300func (pk *PublicKey) setFingerPrintAndKeyId() { 301 // RFC 4880, section 12.2 302 fingerPrint := sha1.New() 303 pk.SerializeSignaturePrefix(fingerPrint) 304 pk.serializeWithoutHeaders(fingerPrint) 305 copy(pk.Fingerprint[:], fingerPrint.Sum(nil)) 306 pk.KeyId = binary.BigEndian.Uint64(pk.Fingerprint[12:20]) 307} 308 309// parseRSA parses RSA public key material from the given Reader. See RFC 4880, 310// section 5.5.2. 311func (pk *PublicKey) parseRSA(r io.Reader) (err error) { 312 pk.n.bytes, pk.n.bitLength, err = readMPI(r) 313 if err != nil { 314 return 315 } 316 pk.e.bytes, pk.e.bitLength, err = readMPI(r) 317 if err != nil { 318 return 319 } 320 321 if len(pk.e.bytes) > 3 { 322 err = errors.UnsupportedError("large public exponent") 323 return 324 } 325 rsa := &rsa.PublicKey{ 326 N: new(big.Int).SetBytes(pk.n.bytes), 327 E: 0, 328 } 329 for i := 0; i < len(pk.e.bytes); i++ { 330 rsa.E <<= 8 331 rsa.E |= int(pk.e.bytes[i]) 332 } 333 pk.PublicKey = rsa 334 return 335} 336 337// parseDSA parses DSA public key material from the given Reader. See RFC 4880, 338// section 5.5.2. 339func (pk *PublicKey) parseDSA(r io.Reader) (err error) { 340 pk.p.bytes, pk.p.bitLength, err = readMPI(r) 341 if err != nil { 342 return 343 } 344 pk.q.bytes, pk.q.bitLength, err = readMPI(r) 345 if err != nil { 346 return 347 } 348 pk.g.bytes, pk.g.bitLength, err = readMPI(r) 349 if err != nil { 350 return 351 } 352 pk.y.bytes, pk.y.bitLength, err = readMPI(r) 353 if err != nil { 354 return 355 } 356 357 dsa := new(dsa.PublicKey) 358 dsa.P = new(big.Int).SetBytes(pk.p.bytes) 359 dsa.Q = new(big.Int).SetBytes(pk.q.bytes) 360 dsa.G = new(big.Int).SetBytes(pk.g.bytes) 361 dsa.Y = new(big.Int).SetBytes(pk.y.bytes) 362 pk.PublicKey = dsa 363 return 364} 365 366// parseElGamal parses ElGamal public key material from the given Reader. See 367// RFC 4880, section 5.5.2. 368func (pk *PublicKey) parseElGamal(r io.Reader) (err error) { 369 pk.p.bytes, pk.p.bitLength, err = readMPI(r) 370 if err != nil { 371 return 372 } 373 pk.g.bytes, pk.g.bitLength, err = readMPI(r) 374 if err != nil { 375 return 376 } 377 pk.y.bytes, pk.y.bitLength, err = readMPI(r) 378 if err != nil { 379 return 380 } 381 382 elgamal := new(elgamal.PublicKey) 383 elgamal.P = new(big.Int).SetBytes(pk.p.bytes) 384 elgamal.G = new(big.Int).SetBytes(pk.g.bytes) 385 elgamal.Y = new(big.Int).SetBytes(pk.y.bytes) 386 pk.PublicKey = elgamal 387 return 388} 389 390// SerializeSignaturePrefix writes the prefix for this public key to the given Writer. 391// The prefix is used when calculating a signature over this public key. See 392// RFC 4880, section 5.2.4. 393func (pk *PublicKey) SerializeSignaturePrefix(h io.Writer) { 394 var pLength uint16 395 switch pk.PubKeyAlgo { 396 case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly: 397 pLength += 2 + uint16(len(pk.n.bytes)) 398 pLength += 2 + uint16(len(pk.e.bytes)) 399 case PubKeyAlgoDSA: 400 pLength += 2 + uint16(len(pk.p.bytes)) 401 pLength += 2 + uint16(len(pk.q.bytes)) 402 pLength += 2 + uint16(len(pk.g.bytes)) 403 pLength += 2 + uint16(len(pk.y.bytes)) 404 case PubKeyAlgoElGamal: 405 pLength += 2 + uint16(len(pk.p.bytes)) 406 pLength += 2 + uint16(len(pk.g.bytes)) 407 pLength += 2 + uint16(len(pk.y.bytes)) 408 case PubKeyAlgoECDSA: 409 pLength += uint16(pk.ec.byteLen()) 410 case PubKeyAlgoECDH: 411 pLength += uint16(pk.ec.byteLen()) 412 pLength += uint16(pk.ecdh.byteLen()) 413 default: 414 panic("unknown public key algorithm") 415 } 416 pLength += 6 417 h.Write([]byte{0x99, byte(pLength >> 8), byte(pLength)}) 418 return 419} 420 421func (pk *PublicKey) Serialize(w io.Writer) (err error) { 422 length := 6 // 6 byte header 423 424 switch pk.PubKeyAlgo { 425 case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly: 426 length += 2 + len(pk.n.bytes) 427 length += 2 + len(pk.e.bytes) 428 case PubKeyAlgoDSA: 429 length += 2 + len(pk.p.bytes) 430 length += 2 + len(pk.q.bytes) 431 length += 2 + len(pk.g.bytes) 432 length += 2 + len(pk.y.bytes) 433 case PubKeyAlgoElGamal: 434 length += 2 + len(pk.p.bytes) 435 length += 2 + len(pk.g.bytes) 436 length += 2 + len(pk.y.bytes) 437 case PubKeyAlgoECDSA: 438 length += pk.ec.byteLen() 439 case PubKeyAlgoECDH: 440 length += pk.ec.byteLen() 441 length += pk.ecdh.byteLen() 442 default: 443 panic("unknown public key algorithm") 444 } 445 446 packetType := packetTypePublicKey 447 if pk.IsSubkey { 448 packetType = packetTypePublicSubkey 449 } 450 err = serializeHeader(w, packetType, length) 451 if err != nil { 452 return 453 } 454 return pk.serializeWithoutHeaders(w) 455} 456 457// serializeWithoutHeaders marshals the PublicKey to w in the form of an 458// OpenPGP public key packet, not including the packet header. 459func (pk *PublicKey) serializeWithoutHeaders(w io.Writer) (err error) { 460 var buf [6]byte 461 buf[0] = 4 462 t := uint32(pk.CreationTime.Unix()) 463 buf[1] = byte(t >> 24) 464 buf[2] = byte(t >> 16) 465 buf[3] = byte(t >> 8) 466 buf[4] = byte(t) 467 buf[5] = byte(pk.PubKeyAlgo) 468 469 _, err = w.Write(buf[:]) 470 if err != nil { 471 return 472 } 473 474 switch pk.PubKeyAlgo { 475 case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly: 476 return writeMPIs(w, pk.n, pk.e) 477 case PubKeyAlgoDSA: 478 return writeMPIs(w, pk.p, pk.q, pk.g, pk.y) 479 case PubKeyAlgoElGamal: 480 return writeMPIs(w, pk.p, pk.g, pk.y) 481 case PubKeyAlgoECDSA: 482 return pk.ec.serialize(w) 483 case PubKeyAlgoECDH: 484 if err = pk.ec.serialize(w); err != nil { 485 return 486 } 487 return pk.ecdh.serialize(w) 488 } 489 return errors.InvalidArgumentError("bad public-key algorithm") 490} 491 492// CanSign returns true iff this public key can generate signatures 493func (pk *PublicKey) CanSign() bool { 494 return pk.PubKeyAlgo != PubKeyAlgoRSAEncryptOnly && pk.PubKeyAlgo != PubKeyAlgoElGamal 495} 496 497// VerifySignature returns nil iff sig is a valid signature, made by this 498// public key, of the data hashed into signed. signed is mutated by this call. 499func (pk *PublicKey) VerifySignature(signed hash.Hash, sig *Signature) (err error) { 500 if !pk.CanSign() { 501 return errors.InvalidArgumentError("public key cannot generate signatures") 502 } 503 504 signed.Write(sig.HashSuffix) 505 hashBytes := signed.Sum(nil) 506 507 if hashBytes[0] != sig.HashTag[0] || hashBytes[1] != sig.HashTag[1] { 508 return errors.SignatureError("hash tag doesn't match") 509 } 510 511 if pk.PubKeyAlgo != sig.PubKeyAlgo { 512 return errors.InvalidArgumentError("public key and signature use different algorithms") 513 } 514 515 switch pk.PubKeyAlgo { 516 case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly: 517 rsaPublicKey, _ := pk.PublicKey.(*rsa.PublicKey) 518 err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, sig.RSASignature.bytes) 519 if err != nil { 520 return errors.SignatureError("RSA verification failure") 521 } 522 return nil 523 case PubKeyAlgoDSA: 524 dsaPublicKey, _ := pk.PublicKey.(*dsa.PublicKey) 525 // Need to truncate hashBytes to match FIPS 186-3 section 4.6. 526 subgroupSize := (dsaPublicKey.Q.BitLen() + 7) / 8 527 if len(hashBytes) > subgroupSize { 528 hashBytes = hashBytes[:subgroupSize] 529 } 530 if !dsa.Verify(dsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.DSASigR.bytes), new(big.Int).SetBytes(sig.DSASigS.bytes)) { 531 return errors.SignatureError("DSA verification failure") 532 } 533 return nil 534 case PubKeyAlgoECDSA: 535 ecdsaPublicKey := pk.PublicKey.(*ecdsa.PublicKey) 536 if !ecdsa.Verify(ecdsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.ECDSASigR.bytes), new(big.Int).SetBytes(sig.ECDSASigS.bytes)) { 537 return errors.SignatureError("ECDSA verification failure") 538 } 539 return nil 540 default: 541 return errors.SignatureError("Unsupported public key algorithm used in signature") 542 } 543} 544 545// VerifySignatureV3 returns nil iff sig is a valid signature, made by this 546// public key, of the data hashed into signed. signed is mutated by this call. 547func (pk *PublicKey) VerifySignatureV3(signed hash.Hash, sig *SignatureV3) (err error) { 548 if !pk.CanSign() { 549 return errors.InvalidArgumentError("public key cannot generate signatures") 550 } 551 552 suffix := make([]byte, 5) 553 suffix[0] = byte(sig.SigType) 554 binary.BigEndian.PutUint32(suffix[1:], uint32(sig.CreationTime.Unix())) 555 signed.Write(suffix) 556 hashBytes := signed.Sum(nil) 557 558 if hashBytes[0] != sig.HashTag[0] || hashBytes[1] != sig.HashTag[1] { 559 return errors.SignatureError("hash tag doesn't match") 560 } 561 562 if pk.PubKeyAlgo != sig.PubKeyAlgo { 563 return errors.InvalidArgumentError("public key and signature use different algorithms") 564 } 565 566 switch pk.PubKeyAlgo { 567 case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly: 568 rsaPublicKey := pk.PublicKey.(*rsa.PublicKey) 569 if err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, sig.RSASignature.bytes); err != nil { 570 return errors.SignatureError("RSA verification failure") 571 } 572 return 573 case PubKeyAlgoDSA: 574 dsaPublicKey := pk.PublicKey.(*dsa.PublicKey) 575 // Need to truncate hashBytes to match FIPS 186-3 section 4.6. 576 subgroupSize := (dsaPublicKey.Q.BitLen() + 7) / 8 577 if len(hashBytes) > subgroupSize { 578 hashBytes = hashBytes[:subgroupSize] 579 } 580 if !dsa.Verify(dsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.DSASigR.bytes), new(big.Int).SetBytes(sig.DSASigS.bytes)) { 581 return errors.SignatureError("DSA verification failure") 582 } 583 return nil 584 default: 585 panic("shouldn't happen") 586 } 587} 588 589// keySignatureHash returns a Hash of the message that needs to be signed for 590// pk to assert a subkey relationship to signed. 591func keySignatureHash(pk, signed signingKey, hashFunc crypto.Hash) (h hash.Hash, err error) { 592 if !hashFunc.Available() { 593 return nil, errors.UnsupportedError("hash function") 594 } 595 h = hashFunc.New() 596 597 // RFC 4880, section 5.2.4 598 pk.SerializeSignaturePrefix(h) 599 pk.serializeWithoutHeaders(h) 600 signed.SerializeSignaturePrefix(h) 601 signed.serializeWithoutHeaders(h) 602 return 603} 604 605// VerifyKeySignature returns nil iff sig is a valid signature, made by this 606// public key, of signed. 607func (pk *PublicKey) VerifyKeySignature(signed *PublicKey, sig *Signature) error { 608 h, err := keySignatureHash(pk, signed, sig.Hash) 609 if err != nil { 610 return err 611 } 612 if err = pk.VerifySignature(h, sig); err != nil { 613 return err 614 } 615 616 if sig.FlagSign { 617 // Signing subkeys must be cross-signed. See 618 // https://www.gnupg.org/faq/subkey-cross-certify.html. 619 if sig.EmbeddedSignature == nil { 620 return errors.StructuralError("signing subkey is missing cross-signature") 621 } 622 // Verify the cross-signature. This is calculated over the same 623 // data as the main signature, so we cannot just recursively 624 // call signed.VerifyKeySignature(...) 625 if h, err = keySignatureHash(pk, signed, sig.EmbeddedSignature.Hash); err != nil { 626 return errors.StructuralError("error while hashing for cross-signature: " + err.Error()) 627 } 628 if err := signed.VerifySignature(h, sig.EmbeddedSignature); err != nil { 629 return errors.StructuralError("error while verifying cross-signature: " + err.Error()) 630 } 631 } 632 633 return nil 634} 635 636func keyRevocationHash(pk signingKey, hashFunc crypto.Hash) (h hash.Hash, err error) { 637 if !hashFunc.Available() { 638 return nil, errors.UnsupportedError("hash function") 639 } 640 h = hashFunc.New() 641 642 // RFC 4880, section 5.2.4 643 pk.SerializeSignaturePrefix(h) 644 pk.serializeWithoutHeaders(h) 645 646 return 647} 648 649// VerifyRevocationSignature returns nil iff sig is a valid signature, made by this 650// public key. 651func (pk *PublicKey) VerifyRevocationSignature(sig *Signature) (err error) { 652 h, err := keyRevocationHash(pk, sig.Hash) 653 if err != nil { 654 return err 655 } 656 return pk.VerifySignature(h, sig) 657} 658 659// userIdSignatureHash returns a Hash of the message that needs to be signed 660// to assert that pk is a valid key for id. 661func userIdSignatureHash(id string, pk *PublicKey, hashFunc crypto.Hash) (h hash.Hash, err error) { 662 if !hashFunc.Available() { 663 return nil, errors.UnsupportedError("hash function") 664 } 665 h = hashFunc.New() 666 667 // RFC 4880, section 5.2.4 668 pk.SerializeSignaturePrefix(h) 669 pk.serializeWithoutHeaders(h) 670 671 var buf [5]byte 672 buf[0] = 0xb4 673 buf[1] = byte(len(id) >> 24) 674 buf[2] = byte(len(id) >> 16) 675 buf[3] = byte(len(id) >> 8) 676 buf[4] = byte(len(id)) 677 h.Write(buf[:]) 678 h.Write([]byte(id)) 679 680 return 681} 682 683// VerifyUserIdSignature returns nil iff sig is a valid signature, made by this 684// public key, that id is the identity of pub. 685func (pk *PublicKey) VerifyUserIdSignature(id string, pub *PublicKey, sig *Signature) (err error) { 686 h, err := userIdSignatureHash(id, pub, sig.Hash) 687 if err != nil { 688 return err 689 } 690 return pk.VerifySignature(h, sig) 691} 692 693// VerifyUserIdSignatureV3 returns nil iff sig is a valid signature, made by this 694// public key, that id is the identity of pub. 695func (pk *PublicKey) VerifyUserIdSignatureV3(id string, pub *PublicKey, sig *SignatureV3) (err error) { 696 h, err := userIdSignatureV3Hash(id, pub, sig.Hash) 697 if err != nil { 698 return err 699 } 700 return pk.VerifySignatureV3(h, sig) 701} 702 703// KeyIdString returns the public key's fingerprint in capital hex 704// (e.g. "6C7EE1B8621CC013"). 705func (pk *PublicKey) KeyIdString() string { 706 return fmt.Sprintf("%X", pk.Fingerprint[12:20]) 707} 708 709// KeyIdShortString returns the short form of public key's fingerprint 710// in capital hex, as shown by gpg --list-keys (e.g. "621CC013"). 711func (pk *PublicKey) KeyIdShortString() string { 712 return fmt.Sprintf("%X", pk.Fingerprint[16:20]) 713} 714 715// A parsedMPI is used to store the contents of a big integer, along with the 716// bit length that was specified in the original input. This allows the MPI to 717// be reserialized exactly. 718type parsedMPI struct { 719 bytes []byte 720 bitLength uint16 721} 722 723// writeMPIs is a utility function for serializing several big integers to the 724// given Writer. 725func writeMPIs(w io.Writer, mpis ...parsedMPI) (err error) { 726 for _, mpi := range mpis { 727 err = writeMPI(w, mpi.bitLength, mpi.bytes) 728 if err != nil { 729 return 730 } 731 } 732 return 733} 734 735// BitLength returns the bit length for the given public key. 736func (pk *PublicKey) BitLength() (bitLength uint16, err error) { 737 switch pk.PubKeyAlgo { 738 case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly: 739 bitLength = pk.n.bitLength 740 case PubKeyAlgoDSA: 741 bitLength = pk.p.bitLength 742 case PubKeyAlgoElGamal: 743 bitLength = pk.p.bitLength 744 default: 745 err = errors.InvalidArgumentError("bad public-key algorithm") 746 } 747 return 748} 749