mirror of https://github.com/go-gitea/gitea.git
280 lines
8.0 KiB
Go
280 lines
8.0 KiB
Go
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// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package packet
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import (
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"crypto"
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"crypto/md5"
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"crypto/rsa"
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"encoding/binary"
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"fmt"
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"hash"
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"io"
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"math/big"
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"strconv"
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"time"
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"golang.org/x/crypto/openpgp/errors"
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)
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// PublicKeyV3 represents older, version 3 public keys. These keys are less secure and
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// should not be used for signing or encrypting. They are supported here only for
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// parsing version 3 key material and validating signatures.
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// See RFC 4880, section 5.5.2.
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type PublicKeyV3 struct {
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CreationTime time.Time
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DaysToExpire uint16
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PubKeyAlgo PublicKeyAlgorithm
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PublicKey *rsa.PublicKey
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Fingerprint [16]byte
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KeyId uint64
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IsSubkey bool
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n, e parsedMPI
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}
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// newRSAPublicKeyV3 returns a PublicKey that wraps the given rsa.PublicKey.
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// Included here for testing purposes only. RFC 4880, section 5.5.2:
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// "an implementation MUST NOT generate a V3 key, but MAY accept it."
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func newRSAPublicKeyV3(creationTime time.Time, pub *rsa.PublicKey) *PublicKeyV3 {
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pk := &PublicKeyV3{
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CreationTime: creationTime,
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PublicKey: pub,
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n: fromBig(pub.N),
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e: fromBig(big.NewInt(int64(pub.E))),
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}
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pk.setFingerPrintAndKeyId()
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return pk
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}
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func (pk *PublicKeyV3) parse(r io.Reader) (err error) {
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// RFC 4880, section 5.5.2
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var buf [8]byte
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if _, err = readFull(r, buf[:]); err != nil {
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return
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}
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if buf[0] < 2 || buf[0] > 3 {
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return errors.UnsupportedError("public key version")
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}
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pk.CreationTime = time.Unix(int64(uint32(buf[1])<<24|uint32(buf[2])<<16|uint32(buf[3])<<8|uint32(buf[4])), 0)
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pk.DaysToExpire = binary.BigEndian.Uint16(buf[5:7])
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pk.PubKeyAlgo = PublicKeyAlgorithm(buf[7])
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switch pk.PubKeyAlgo {
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case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
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err = pk.parseRSA(r)
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default:
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err = errors.UnsupportedError("public key type: " + strconv.Itoa(int(pk.PubKeyAlgo)))
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}
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if err != nil {
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return
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}
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pk.setFingerPrintAndKeyId()
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return
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}
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func (pk *PublicKeyV3) setFingerPrintAndKeyId() {
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// RFC 4880, section 12.2
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fingerPrint := md5.New()
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fingerPrint.Write(pk.n.bytes)
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fingerPrint.Write(pk.e.bytes)
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fingerPrint.Sum(pk.Fingerprint[:0])
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pk.KeyId = binary.BigEndian.Uint64(pk.n.bytes[len(pk.n.bytes)-8:])
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}
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// parseRSA parses RSA public key material from the given Reader. See RFC 4880,
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// section 5.5.2.
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func (pk *PublicKeyV3) parseRSA(r io.Reader) (err error) {
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if pk.n.bytes, pk.n.bitLength, err = readMPI(r); err != nil {
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return
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}
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if pk.e.bytes, pk.e.bitLength, err = readMPI(r); err != nil {
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return
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}
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// RFC 4880 Section 12.2 requires the low 8 bytes of the
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// modulus to form the key id.
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if len(pk.n.bytes) < 8 {
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return errors.StructuralError("v3 public key modulus is too short")
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}
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if len(pk.e.bytes) > 3 {
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err = errors.UnsupportedError("large public exponent")
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return
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}
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rsa := &rsa.PublicKey{N: new(big.Int).SetBytes(pk.n.bytes)}
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for i := 0; i < len(pk.e.bytes); i++ {
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rsa.E <<= 8
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rsa.E |= int(pk.e.bytes[i])
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}
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pk.PublicKey = rsa
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return
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}
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// SerializeSignaturePrefix writes the prefix for this public key to the given Writer.
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// The prefix is used when calculating a signature over this public key. See
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// RFC 4880, section 5.2.4.
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func (pk *PublicKeyV3) SerializeSignaturePrefix(w io.Writer) {
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var pLength uint16
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switch pk.PubKeyAlgo {
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case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
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pLength += 2 + uint16(len(pk.n.bytes))
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pLength += 2 + uint16(len(pk.e.bytes))
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default:
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panic("unknown public key algorithm")
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}
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pLength += 6
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w.Write([]byte{0x99, byte(pLength >> 8), byte(pLength)})
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return
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}
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func (pk *PublicKeyV3) Serialize(w io.Writer) (err error) {
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length := 8 // 8 byte header
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switch pk.PubKeyAlgo {
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case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
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length += 2 + len(pk.n.bytes)
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length += 2 + len(pk.e.bytes)
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default:
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panic("unknown public key algorithm")
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}
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packetType := packetTypePublicKey
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if pk.IsSubkey {
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packetType = packetTypePublicSubkey
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}
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if err = serializeHeader(w, packetType, length); err != nil {
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return
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}
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return pk.serializeWithoutHeaders(w)
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}
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// serializeWithoutHeaders marshals the PublicKey to w in the form of an
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// OpenPGP public key packet, not including the packet header.
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func (pk *PublicKeyV3) serializeWithoutHeaders(w io.Writer) (err error) {
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var buf [8]byte
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// Version 3
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buf[0] = 3
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// Creation time
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t := uint32(pk.CreationTime.Unix())
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buf[1] = byte(t >> 24)
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buf[2] = byte(t >> 16)
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buf[3] = byte(t >> 8)
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buf[4] = byte(t)
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// Days to expire
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buf[5] = byte(pk.DaysToExpire >> 8)
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buf[6] = byte(pk.DaysToExpire)
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// Public key algorithm
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buf[7] = byte(pk.PubKeyAlgo)
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if _, err = w.Write(buf[:]); err != nil {
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return
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}
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switch pk.PubKeyAlgo {
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case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
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return writeMPIs(w, pk.n, pk.e)
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}
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return errors.InvalidArgumentError("bad public-key algorithm")
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}
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// CanSign returns true iff this public key can generate signatures
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func (pk *PublicKeyV3) CanSign() bool {
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return pk.PubKeyAlgo != PubKeyAlgoRSAEncryptOnly
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}
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// VerifySignatureV3 returns nil iff sig is a valid signature, made by this
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// public key, of the data hashed into signed. signed is mutated by this call.
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func (pk *PublicKeyV3) VerifySignatureV3(signed hash.Hash, sig *SignatureV3) (err error) {
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if !pk.CanSign() {
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return errors.InvalidArgumentError("public key cannot generate signatures")
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}
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suffix := make([]byte, 5)
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suffix[0] = byte(sig.SigType)
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binary.BigEndian.PutUint32(suffix[1:], uint32(sig.CreationTime.Unix()))
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signed.Write(suffix)
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hashBytes := signed.Sum(nil)
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if hashBytes[0] != sig.HashTag[0] || hashBytes[1] != sig.HashTag[1] {
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return errors.SignatureError("hash tag doesn't match")
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}
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if pk.PubKeyAlgo != sig.PubKeyAlgo {
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return errors.InvalidArgumentError("public key and signature use different algorithms")
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}
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switch pk.PubKeyAlgo {
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case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
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if err = rsa.VerifyPKCS1v15(pk.PublicKey, sig.Hash, hashBytes, sig.RSASignature.bytes); err != nil {
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return errors.SignatureError("RSA verification failure")
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}
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return
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default:
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// V3 public keys only support RSA.
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panic("shouldn't happen")
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}
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}
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// VerifyUserIdSignatureV3 returns nil iff sig is a valid signature, made by this
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// public key, that id is the identity of pub.
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func (pk *PublicKeyV3) VerifyUserIdSignatureV3(id string, pub *PublicKeyV3, sig *SignatureV3) (err error) {
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h, err := userIdSignatureV3Hash(id, pk, sig.Hash)
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if err != nil {
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return err
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}
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return pk.VerifySignatureV3(h, sig)
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}
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// VerifyKeySignatureV3 returns nil iff sig is a valid signature, made by this
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// public key, of signed.
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func (pk *PublicKeyV3) VerifyKeySignatureV3(signed *PublicKeyV3, sig *SignatureV3) (err error) {
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h, err := keySignatureHash(pk, signed, sig.Hash)
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if err != nil {
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return err
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}
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return pk.VerifySignatureV3(h, sig)
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}
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// userIdSignatureV3Hash returns a Hash of the message that needs to be signed
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// to assert that pk is a valid key for id.
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func userIdSignatureV3Hash(id string, pk signingKey, hfn crypto.Hash) (h hash.Hash, err error) {
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if !hfn.Available() {
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return nil, errors.UnsupportedError("hash function")
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}
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h = hfn.New()
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// RFC 4880, section 5.2.4
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pk.SerializeSignaturePrefix(h)
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pk.serializeWithoutHeaders(h)
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h.Write([]byte(id))
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return
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}
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// KeyIdString returns the public key's fingerprint in capital hex
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// (e.g. "6C7EE1B8621CC013").
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func (pk *PublicKeyV3) KeyIdString() string {
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return fmt.Sprintf("%X", pk.KeyId)
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}
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// KeyIdShortString returns the short form of public key's fingerprint
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// in capital hex, as shown by gpg --list-keys (e.g. "621CC013").
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func (pk *PublicKeyV3) KeyIdShortString() string {
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return fmt.Sprintf("%X", pk.KeyId&0xFFFFFFFF)
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}
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// BitLength returns the bit length for the given public key.
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func (pk *PublicKeyV3) BitLength() (bitLength uint16, err error) {
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switch pk.PubKeyAlgo {
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case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
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bitLength = pk.n.bitLength
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default:
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err = errors.InvalidArgumentError("bad public-key algorithm")
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}
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return
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}
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