githaven/vendor/github.com/ProtonMail/go-crypto/openpgp/packet/public_key.go
6543 86e2789960
Vendor Update (#16121)
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Co-authored-by: techknowlogick <techknowlogick@gitea.io>
2021-06-10 16:44:25 +02:00

826 lines
23 KiB
Go
Vendored

// Copyright 2011 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 packet
import (
"crypto"
"crypto/dsa"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rsa"
"crypto/sha1"
"crypto/sha256"
_ "crypto/sha512"
"encoding/binary"
"fmt"
"hash"
"io"
"math/big"
"strconv"
"time"
"github.com/ProtonMail/go-crypto/openpgp/ecdh"
"github.com/ProtonMail/go-crypto/openpgp/elgamal"
"github.com/ProtonMail/go-crypto/openpgp/errors"
"github.com/ProtonMail/go-crypto/openpgp/internal/algorithm"
"github.com/ProtonMail/go-crypto/openpgp/internal/ecc"
"github.com/ProtonMail/go-crypto/openpgp/internal/encoding"
"golang.org/x/crypto/ed25519"
)
type kdfHashFunction byte
type kdfAlgorithm byte
// PublicKey represents an OpenPGP public key. See RFC 4880, section 5.5.2.
type PublicKey struct {
Version int
CreationTime time.Time
PubKeyAlgo PublicKeyAlgorithm
PublicKey interface{} // *rsa.PublicKey, *dsa.PublicKey, *ecdsa.PublicKey or *eddsa.PublicKey
Fingerprint []byte
KeyId uint64
IsSubkey bool
// RFC 4880 fields
n, e, p, q, g, y encoding.Field
// RFC 6637 fields
// oid contains the OID byte sequence identifying the elliptic curve used
oid encoding.Field
// kdf stores key derivation function parameters
// used for ECDH encryption. See RFC 6637, Section 9.
kdf encoding.Field
}
// UpgradeToV5 updates the version of the key to v5, and updates all necessary
// fields.
func (pk *PublicKey) UpgradeToV5() {
pk.Version = 5
pk.setFingerprintAndKeyId()
}
// signingKey provides a convenient abstraction over signature verification
// for v3 and v4 public keys.
type signingKey interface {
SerializeForHash(io.Writer) error
SerializeSignaturePrefix(io.Writer)
serializeWithoutHeaders(io.Writer) error
}
// NewRSAPublicKey returns a PublicKey that wraps the given rsa.PublicKey.
func NewRSAPublicKey(creationTime time.Time, pub *rsa.PublicKey) *PublicKey {
pk := &PublicKey{
Version: 4,
CreationTime: creationTime,
PubKeyAlgo: PubKeyAlgoRSA,
PublicKey: pub,
n: new(encoding.MPI).SetBig(pub.N),
e: new(encoding.MPI).SetBig(big.NewInt(int64(pub.E))),
}
pk.setFingerprintAndKeyId()
return pk
}
// NewDSAPublicKey returns a PublicKey that wraps the given dsa.PublicKey.
func NewDSAPublicKey(creationTime time.Time, pub *dsa.PublicKey) *PublicKey {
pk := &PublicKey{
Version: 4,
CreationTime: creationTime,
PubKeyAlgo: PubKeyAlgoDSA,
PublicKey: pub,
p: new(encoding.MPI).SetBig(pub.P),
q: new(encoding.MPI).SetBig(pub.Q),
g: new(encoding.MPI).SetBig(pub.G),
y: new(encoding.MPI).SetBig(pub.Y),
}
pk.setFingerprintAndKeyId()
return pk
}
// NewElGamalPublicKey returns a PublicKey that wraps the given elgamal.PublicKey.
func NewElGamalPublicKey(creationTime time.Time, pub *elgamal.PublicKey) *PublicKey {
pk := &PublicKey{
Version: 4,
CreationTime: creationTime,
PubKeyAlgo: PubKeyAlgoElGamal,
PublicKey: pub,
p: new(encoding.MPI).SetBig(pub.P),
g: new(encoding.MPI).SetBig(pub.G),
y: new(encoding.MPI).SetBig(pub.Y),
}
pk.setFingerprintAndKeyId()
return pk
}
func NewECDSAPublicKey(creationTime time.Time, pub *ecdsa.PublicKey) *PublicKey {
pk := &PublicKey{
Version: 4,
CreationTime: creationTime,
PubKeyAlgo: PubKeyAlgoECDSA,
PublicKey: pub,
p: encoding.NewMPI(elliptic.Marshal(pub.Curve, pub.X, pub.Y)),
}
curveInfo := ecc.FindByCurve(pub.Curve)
if curveInfo == nil {
panic("unknown elliptic curve")
}
pk.oid = curveInfo.Oid
pk.setFingerprintAndKeyId()
return pk
}
func NewECDHPublicKey(creationTime time.Time, pub *ecdh.PublicKey) *PublicKey {
var pk *PublicKey
var curveInfo *ecc.CurveInfo
var kdf = encoding.NewOID([]byte{0x1, pub.Hash.Id(), pub.Cipher.Id()})
if pub.CurveType == ecc.Curve25519 {
pk = &PublicKey{
Version: 4,
CreationTime: creationTime,
PubKeyAlgo: PubKeyAlgoECDH,
PublicKey: pub,
p: encoding.NewMPI(pub.X.Bytes()),
kdf: kdf,
}
curveInfo = ecc.FindByName("Curve25519")
} else {
pk = &PublicKey{
Version: 4,
CreationTime: creationTime,
PubKeyAlgo: PubKeyAlgoECDH,
PublicKey: pub,
p: encoding.NewMPI(elliptic.Marshal(pub.Curve, pub.X, pub.Y)),
kdf: kdf,
}
curveInfo = ecc.FindByCurve(pub.Curve)
}
if curveInfo == nil {
panic("unknown elliptic curve")
}
pk.oid = curveInfo.Oid
pk.setFingerprintAndKeyId()
return pk
}
func NewEdDSAPublicKey(creationTime time.Time, pub *ed25519.PublicKey) *PublicKey {
curveInfo := ecc.FindByName("Ed25519")
pk := &PublicKey{
Version: 4,
CreationTime: creationTime,
PubKeyAlgo: PubKeyAlgoEdDSA,
PublicKey: pub,
oid: curveInfo.Oid,
// Native point format, see draft-koch-eddsa-for-openpgp-04, Appendix B
p: encoding.NewMPI(append([]byte{0x40}, *pub...)),
}
pk.setFingerprintAndKeyId()
return pk
}
func (pk *PublicKey) parse(r io.Reader) (err error) {
// RFC 4880, section 5.5.2
var buf [6]byte
_, err = readFull(r, buf[:])
if err != nil {
return
}
if buf[0] != 4 && buf[0] != 5 {
return errors.UnsupportedError("public key version " + strconv.Itoa(int(buf[0])))
}
pk.Version = int(buf[0])
if pk.Version == 5 {
var n [4]byte
_, err = readFull(r, n[:])
if err != nil {
return
}
}
pk.CreationTime = time.Unix(int64(uint32(buf[1])<<24|uint32(buf[2])<<16|uint32(buf[3])<<8|uint32(buf[4])), 0)
pk.PubKeyAlgo = PublicKeyAlgorithm(buf[5])
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
err = pk.parseRSA(r)
case PubKeyAlgoDSA:
err = pk.parseDSA(r)
case PubKeyAlgoElGamal:
err = pk.parseElGamal(r)
case PubKeyAlgoECDSA:
err = pk.parseECDSA(r)
case PubKeyAlgoECDH:
err = pk.parseECDH(r)
case PubKeyAlgoEdDSA:
err = pk.parseEdDSA(r)
default:
err = errors.UnsupportedError("public key type: " + strconv.Itoa(int(pk.PubKeyAlgo)))
}
if err != nil {
return
}
pk.setFingerprintAndKeyId()
return
}
func (pk *PublicKey) setFingerprintAndKeyId() {
// RFC 4880, section 12.2
if pk.Version == 5 {
fingerprint := sha256.New()
pk.SerializeForHash(fingerprint)
pk.Fingerprint = make([]byte, 32)
copy(pk.Fingerprint, fingerprint.Sum(nil))
pk.KeyId = binary.BigEndian.Uint64(pk.Fingerprint[:8])
} else {
fingerprint := sha1.New()
pk.SerializeForHash(fingerprint)
pk.Fingerprint = make([]byte, 20)
copy(pk.Fingerprint, fingerprint.Sum(nil))
pk.KeyId = binary.BigEndian.Uint64(pk.Fingerprint[12:20])
}
}
// parseRSA parses RSA public key material from the given Reader. See RFC 4880,
// section 5.5.2.
func (pk *PublicKey) parseRSA(r io.Reader) (err error) {
pk.n = new(encoding.MPI)
if _, err = pk.n.ReadFrom(r); err != nil {
return
}
pk.e = new(encoding.MPI)
if _, err = pk.e.ReadFrom(r); err != nil {
return
}
if len(pk.e.Bytes()) > 3 {
err = errors.UnsupportedError("large public exponent")
return
}
rsa := &rsa.PublicKey{
N: new(big.Int).SetBytes(pk.n.Bytes()),
E: 0,
}
for i := 0; i < len(pk.e.Bytes()); i++ {
rsa.E <<= 8
rsa.E |= int(pk.e.Bytes()[i])
}
pk.PublicKey = rsa
return
}
// parseDSA parses DSA public key material from the given Reader. See RFC 4880,
// section 5.5.2.
func (pk *PublicKey) parseDSA(r io.Reader) (err error) {
pk.p = new(encoding.MPI)
if _, err = pk.p.ReadFrom(r); err != nil {
return
}
pk.q = new(encoding.MPI)
if _, err = pk.q.ReadFrom(r); err != nil {
return
}
pk.g = new(encoding.MPI)
if _, err = pk.g.ReadFrom(r); err != nil {
return
}
pk.y = new(encoding.MPI)
if _, err = pk.y.ReadFrom(r); err != nil {
return
}
dsa := new(dsa.PublicKey)
dsa.P = new(big.Int).SetBytes(pk.p.Bytes())
dsa.Q = new(big.Int).SetBytes(pk.q.Bytes())
dsa.G = new(big.Int).SetBytes(pk.g.Bytes())
dsa.Y = new(big.Int).SetBytes(pk.y.Bytes())
pk.PublicKey = dsa
return
}
// parseElGamal parses ElGamal public key material from the given Reader. See
// RFC 4880, section 5.5.2.
func (pk *PublicKey) parseElGamal(r io.Reader) (err error) {
pk.p = new(encoding.MPI)
if _, err = pk.p.ReadFrom(r); err != nil {
return
}
pk.g = new(encoding.MPI)
if _, err = pk.g.ReadFrom(r); err != nil {
return
}
pk.y = new(encoding.MPI)
if _, err = pk.y.ReadFrom(r); err != nil {
return
}
elgamal := new(elgamal.PublicKey)
elgamal.P = new(big.Int).SetBytes(pk.p.Bytes())
elgamal.G = new(big.Int).SetBytes(pk.g.Bytes())
elgamal.Y = new(big.Int).SetBytes(pk.y.Bytes())
pk.PublicKey = elgamal
return
}
// parseECDSA parses ECDSA public key material from the given Reader. See
// RFC 6637, Section 9.
func (pk *PublicKey) parseECDSA(r io.Reader) (err error) {
pk.oid = new(encoding.OID)
if _, err = pk.oid.ReadFrom(r); err != nil {
return
}
pk.p = new(encoding.MPI)
if _, err = pk.p.ReadFrom(r); err != nil {
return
}
var c elliptic.Curve
curveInfo := ecc.FindByOid(pk.oid)
if curveInfo == nil || curveInfo.SigAlgorithm != ecc.ECDSA {
return errors.UnsupportedError(fmt.Sprintf("unsupported oid: %x", pk.oid))
}
c = curveInfo.Curve
x, y := elliptic.Unmarshal(c, pk.p.Bytes())
if x == nil {
return errors.UnsupportedError("failed to parse EC point")
}
pk.PublicKey = &ecdsa.PublicKey{Curve: c, X: x, Y: y}
return
}
// parseECDH parses ECDH public key material from the given Reader. See
// RFC 6637, Section 9.
func (pk *PublicKey) parseECDH(r io.Reader) (err error) {
pk.oid = new(encoding.OID)
if _, err = pk.oid.ReadFrom(r); err != nil {
return
}
pk.p = new(encoding.MPI)
if _, err = pk.p.ReadFrom(r); err != nil {
return
}
pk.kdf = new(encoding.OID)
if _, err = pk.kdf.ReadFrom(r); err != nil {
return
}
curveInfo := ecc.FindByOid(pk.oid)
if curveInfo == nil {
return errors.UnsupportedError(fmt.Sprintf("unsupported oid: %x", pk.oid))
}
c := curveInfo.Curve
cType := curveInfo.CurveType
var x, y *big.Int
if cType == ecc.Curve25519 {
x = new(big.Int)
x.SetBytes(pk.p.Bytes())
} else {
x, y = elliptic.Unmarshal(c, pk.p.Bytes())
}
if x == nil {
return errors.UnsupportedError("failed to parse EC point")
}
if kdfLen := len(pk.kdf.Bytes()); kdfLen < 3 {
return errors.UnsupportedError("unsupported ECDH KDF length: " + strconv.Itoa(kdfLen))
}
if reserved := pk.kdf.Bytes()[0]; reserved != 0x01 {
return errors.UnsupportedError("unsupported KDF reserved field: " + strconv.Itoa(int(reserved)))
}
kdfHash, ok := algorithm.HashById[pk.kdf.Bytes()[1]]
if !ok {
return errors.UnsupportedError("unsupported ECDH KDF hash: " + strconv.Itoa(int(pk.kdf.Bytes()[1])))
}
kdfCipher, ok := algorithm.CipherById[pk.kdf.Bytes()[2]]
if !ok {
return errors.UnsupportedError("unsupported ECDH KDF cipher: " + strconv.Itoa(int(pk.kdf.Bytes()[2])))
}
pk.PublicKey = &ecdh.PublicKey{
CurveType: cType,
Curve: c,
X: x,
Y: y,
KDF: ecdh.KDF{
Hash: kdfHash,
Cipher: kdfCipher,
},
}
return
}
func (pk *PublicKey) parseEdDSA(r io.Reader) (err error) {
pk.oid = new(encoding.OID)
if _, err = pk.oid.ReadFrom(r); err != nil {
return
}
curveInfo := ecc.FindByOid(pk.oid)
if curveInfo == nil || curveInfo.SigAlgorithm != ecc.EdDSA {
return errors.UnsupportedError(fmt.Sprintf("unsupported oid: %x", pk.oid))
}
pk.p = new(encoding.MPI)
if _, err = pk.p.ReadFrom(r); err != nil {
return
}
eddsa := make(ed25519.PublicKey, ed25519.PublicKeySize)
switch flag := pk.p.Bytes()[0]; flag {
case 0x04:
// TODO: see _grcy_ecc_eddsa_ensure_compact in grcypt
return errors.UnsupportedError("unsupported EdDSA compression: " + strconv.Itoa(int(flag)))
case 0x40:
copy(eddsa[:], pk.p.Bytes()[1:])
default:
return errors.UnsupportedError("unsupported EdDSA compression: " + strconv.Itoa(int(flag)))
}
pk.PublicKey = &eddsa
return
}
// SerializeForHash serializes the PublicKey to w with the special packet
// header format needed for hashing.
func (pk *PublicKey) SerializeForHash(w io.Writer) error {
pk.SerializeSignaturePrefix(w)
return pk.serializeWithoutHeaders(w)
}
// SerializeSignaturePrefix writes the prefix for this public key to the given Writer.
// The prefix is used when calculating a signature over this public key. See
// RFC 4880, section 5.2.4.
func (pk *PublicKey) SerializeSignaturePrefix(w io.Writer) {
var pLength = pk.algorithmSpecificByteCount()
if pk.Version == 5 {
pLength += 10 // version, timestamp (4), algorithm, key octet count (4).
w.Write([]byte{
0x9A,
byte(pLength >> 24),
byte(pLength >> 16),
byte(pLength >> 8),
byte(pLength),
})
return
}
pLength += 6
w.Write([]byte{0x99, byte(pLength >> 8), byte(pLength)})
}
func (pk *PublicKey) Serialize(w io.Writer) (err error) {
length := 6 // 6 byte header
length += pk.algorithmSpecificByteCount()
if pk.Version == 5 {
length += 4 // octet key count
}
packetType := packetTypePublicKey
if pk.IsSubkey {
packetType = packetTypePublicSubkey
}
err = serializeHeader(w, packetType, length)
if err != nil {
return
}
return pk.serializeWithoutHeaders(w)
}
func (pk *PublicKey) algorithmSpecificByteCount() int {
length := 0
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
length += int(pk.n.EncodedLength())
length += int(pk.e.EncodedLength())
case PubKeyAlgoDSA:
length += int(pk.p.EncodedLength())
length += int(pk.q.EncodedLength())
length += int(pk.g.EncodedLength())
length += int(pk.y.EncodedLength())
case PubKeyAlgoElGamal:
length += int(pk.p.EncodedLength())
length += int(pk.g.EncodedLength())
length += int(pk.y.EncodedLength())
case PubKeyAlgoECDSA:
length += int(pk.oid.EncodedLength())
length += int(pk.p.EncodedLength())
case PubKeyAlgoECDH:
length += int(pk.oid.EncodedLength())
length += int(pk.p.EncodedLength())
length += int(pk.kdf.EncodedLength())
case PubKeyAlgoEdDSA:
length += int(pk.oid.EncodedLength())
length += int(pk.p.EncodedLength())
default:
panic("unknown public key algorithm")
}
return length
}
// serializeWithoutHeaders marshals the PublicKey to w in the form of an
// OpenPGP public key packet, not including the packet header.
func (pk *PublicKey) serializeWithoutHeaders(w io.Writer) (err error) {
t := uint32(pk.CreationTime.Unix())
if _, err = w.Write([]byte{
byte(pk.Version),
byte(t >> 24), byte(t >> 16), byte(t >> 8), byte(t),
byte(pk.PubKeyAlgo),
}); err != nil {
return
}
if pk.Version == 5 {
n := pk.algorithmSpecificByteCount()
if _, err = w.Write([]byte{
byte(n >> 24), byte(n >> 16), byte(n >> 8), byte(n),
}); err != nil {
return
}
}
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
if _, err = w.Write(pk.n.EncodedBytes()); err != nil {
return
}
_, err = w.Write(pk.e.EncodedBytes())
return
case PubKeyAlgoDSA:
if _, err = w.Write(pk.p.EncodedBytes()); err != nil {
return
}
if _, err = w.Write(pk.q.EncodedBytes()); err != nil {
return
}
if _, err = w.Write(pk.g.EncodedBytes()); err != nil {
return
}
_, err = w.Write(pk.y.EncodedBytes())
return
case PubKeyAlgoElGamal:
if _, err = w.Write(pk.p.EncodedBytes()); err != nil {
return
}
if _, err = w.Write(pk.g.EncodedBytes()); err != nil {
return
}
_, err = w.Write(pk.y.EncodedBytes())
return
case PubKeyAlgoECDSA:
if _, err = w.Write(pk.oid.EncodedBytes()); err != nil {
return
}
_, err = w.Write(pk.p.EncodedBytes())
return
case PubKeyAlgoECDH:
if _, err = w.Write(pk.oid.EncodedBytes()); err != nil {
return
}
if _, err = w.Write(pk.p.EncodedBytes()); err != nil {
return
}
_, err = w.Write(pk.kdf.EncodedBytes())
return
case PubKeyAlgoEdDSA:
if _, err = w.Write(pk.oid.EncodedBytes()); err != nil {
return
}
_, err = w.Write(pk.p.EncodedBytes())
return
}
return errors.InvalidArgumentError("bad public-key algorithm")
}
// CanSign returns true iff this public key can generate signatures
func (pk *PublicKey) CanSign() bool {
return pk.PubKeyAlgo != PubKeyAlgoRSAEncryptOnly && pk.PubKeyAlgo != PubKeyAlgoElGamal && pk.PubKeyAlgo != PubKeyAlgoECDH
}
// VerifySignature returns nil iff sig is a valid signature, made by this
// public key, of the data hashed into signed. signed is mutated by this call.
func (pk *PublicKey) VerifySignature(signed hash.Hash, sig *Signature) (err error) {
if !pk.CanSign() {
return errors.InvalidArgumentError("public key cannot generate signatures")
}
if sig.Version == 5 && (sig.SigType == 0x00 || sig.SigType == 0x01) {
sig.AddMetadataToHashSuffix()
}
signed.Write(sig.HashSuffix)
hashBytes := signed.Sum(nil)
if hashBytes[0] != sig.HashTag[0] || hashBytes[1] != sig.HashTag[1] {
return errors.SignatureError("hash tag doesn't match")
}
if pk.PubKeyAlgo != sig.PubKeyAlgo {
return errors.InvalidArgumentError("public key and signature use different algorithms")
}
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
rsaPublicKey, _ := pk.PublicKey.(*rsa.PublicKey)
err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, padToKeySize(rsaPublicKey, sig.RSASignature.Bytes()))
if err != nil {
return errors.SignatureError("RSA verification failure")
}
return nil
case PubKeyAlgoDSA:
dsaPublicKey, _ := pk.PublicKey.(*dsa.PublicKey)
// Need to truncate hashBytes to match FIPS 186-3 section 4.6.
subgroupSize := (dsaPublicKey.Q.BitLen() + 7) / 8
if len(hashBytes) > subgroupSize {
hashBytes = hashBytes[:subgroupSize]
}
if !dsa.Verify(dsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.DSASigR.Bytes()), new(big.Int).SetBytes(sig.DSASigS.Bytes())) {
return errors.SignatureError("DSA verification failure")
}
return nil
case PubKeyAlgoECDSA:
ecdsaPublicKey := pk.PublicKey.(*ecdsa.PublicKey)
if !ecdsa.Verify(ecdsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.ECDSASigR.Bytes()), new(big.Int).SetBytes(sig.ECDSASigS.Bytes())) {
return errors.SignatureError("ECDSA verification failure")
}
return nil
case PubKeyAlgoEdDSA:
eddsaPublicKey := pk.PublicKey.(*ed25519.PublicKey)
sigR := sig.EdDSASigR.Bytes()
sigS := sig.EdDSASigS.Bytes()
eddsaSig := make([]byte, ed25519.SignatureSize)
copy(eddsaSig[32-len(sigR):32], sigR)
copy(eddsaSig[64-len(sigS):], sigS)
if !ed25519.Verify(*eddsaPublicKey, hashBytes, eddsaSig) {
return errors.SignatureError("EdDSA verification failure")
}
return nil
default:
return errors.SignatureError("Unsupported public key algorithm used in signature")
}
}
// keySignatureHash returns a Hash of the message that needs to be signed for
// pk to assert a subkey relationship to signed.
func keySignatureHash(pk, signed signingKey, hashFunc crypto.Hash) (h hash.Hash, err error) {
if !hashFunc.Available() {
return nil, errors.UnsupportedError("hash function")
}
h = hashFunc.New()
// RFC 4880, section 5.2.4
err = pk.SerializeForHash(h)
if err != nil {
return nil, err
}
err = signed.SerializeForHash(h)
return
}
// VerifyKeySignature returns nil iff sig is a valid signature, made by this
// public key, of signed.
func (pk *PublicKey) VerifyKeySignature(signed *PublicKey, sig *Signature) error {
h, err := keySignatureHash(pk, signed, sig.Hash)
if err != nil {
return err
}
if err = pk.VerifySignature(h, sig); err != nil {
return err
}
if sig.FlagSign {
// Signing subkeys must be cross-signed. See
// https://www.gnupg.org/faq/subkey-cross-certify.html.
if sig.EmbeddedSignature == nil {
return errors.StructuralError("signing subkey is missing cross-signature")
}
// Verify the cross-signature. This is calculated over the same
// data as the main signature, so we cannot just recursively
// call signed.VerifyKeySignature(...)
if h, err = keySignatureHash(pk, signed, sig.EmbeddedSignature.Hash); err != nil {
return errors.StructuralError("error while hashing for cross-signature: " + err.Error())
}
if err := signed.VerifySignature(h, sig.EmbeddedSignature); err != nil {
return errors.StructuralError("error while verifying cross-signature: " + err.Error())
}
}
return nil
}
func keyRevocationHash(pk signingKey, hashFunc crypto.Hash) (h hash.Hash, err error) {
if !hashFunc.Available() {
return nil, errors.UnsupportedError("hash function")
}
h = hashFunc.New()
// RFC 4880, section 5.2.4
err = pk.SerializeForHash(h)
return
}
// VerifyRevocationSignature returns nil iff sig is a valid signature, made by this
// public key.
func (pk *PublicKey) VerifyRevocationSignature(sig *Signature) (err error) {
h, err := keyRevocationHash(pk, sig.Hash)
if err != nil {
return err
}
return pk.VerifySignature(h, sig)
}
// VerifySubkeyRevocationSignature returns nil iff sig is a valid subkey revocation signature,
// made by the passed in signingKey.
func (pk *PublicKey) VerifySubkeyRevocationSignature(sig *Signature, signingKey *PublicKey) (err error) {
h, err := keyRevocationHash(pk, sig.Hash)
if err != nil {
return err
}
return signingKey.VerifySignature(h, sig)
}
// userIdSignatureHash returns a Hash of the message that needs to be signed
// to assert that pk is a valid key for id.
func userIdSignatureHash(id string, pk *PublicKey, hashFunc crypto.Hash) (h hash.Hash, err error) {
if !hashFunc.Available() {
return nil, errors.UnsupportedError("hash function")
}
h = hashFunc.New()
// RFC 4880, section 5.2.4
pk.SerializeSignaturePrefix(h)
pk.serializeWithoutHeaders(h)
var buf [5]byte
buf[0] = 0xb4
buf[1] = byte(len(id) >> 24)
buf[2] = byte(len(id) >> 16)
buf[3] = byte(len(id) >> 8)
buf[4] = byte(len(id))
h.Write(buf[:])
h.Write([]byte(id))
return
}
// VerifyUserIdSignature returns nil iff sig is a valid signature, made by this
// public key, that id is the identity of pub.
func (pk *PublicKey) VerifyUserIdSignature(id string, pub *PublicKey, sig *Signature) (err error) {
h, err := userIdSignatureHash(id, pub, sig.Hash)
if err != nil {
return err
}
return pk.VerifySignature(h, sig)
}
// KeyIdString returns the public key's fingerprint in capital hex
// (e.g. "6C7EE1B8621CC013").
func (pk *PublicKey) KeyIdString() string {
return fmt.Sprintf("%X", pk.Fingerprint[12:20])
}
// KeyIdShortString returns the short form of public key's fingerprint
// in capital hex, as shown by gpg --list-keys (e.g. "621CC013").
func (pk *PublicKey) KeyIdShortString() string {
return fmt.Sprintf("%X", pk.Fingerprint[16:20])
}
// BitLength returns the bit length for the given public key.
func (pk *PublicKey) BitLength() (bitLength uint16, err error) {
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
bitLength = pk.n.BitLength()
case PubKeyAlgoDSA:
bitLength = pk.p.BitLength()
case PubKeyAlgoElGamal:
bitLength = pk.p.BitLength()
case PubKeyAlgoECDSA:
bitLength = pk.p.BitLength()
case PubKeyAlgoECDH:
bitLength = pk.p.BitLength()
case PubKeyAlgoEdDSA:
bitLength = pk.p.BitLength()
default:
err = errors.InvalidArgumentError("bad public-key algorithm")
}
return
}
// KeyExpired returns whether sig is a self-signature of a key that has
// expired or is created in the future.
func (pk *PublicKey) KeyExpired(sig *Signature, currentTime time.Time) bool {
if pk.CreationTime.After(currentTime) {
return true
}
if sig.KeyLifetimeSecs == nil || *sig.KeyLifetimeSecs == 0 {
return false
}
expiry := pk.CreationTime.Add(time.Duration(*sig.KeyLifetimeSecs) * time.Second)
return currentTime.After(expiry)
}