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crypto/openpgp/packet: add public key support
Note that DSA public key support is nascent and the verification functions clearly don't support it yet. I'm intending to get RSA keys working first. R=bradfitzgo CC=golang-dev https://golang.org/cl/3973054
This commit is contained in:
Adam Langley
parent
459da21603
commit
4a14bc524b
260
src/pkg/crypto/openpgp/packet/public_key.go
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260
src/pkg/crypto/openpgp/packet/public_key.go
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// Copyright 2011 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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"big"
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"crypto/dsa"
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"crypto/openpgp/error"
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"crypto/rsa"
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"crypto/sha1"
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"encoding/binary"
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"hash"
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"io"
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"os"
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)
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// PublicKey represents an OpenPGP public key. See RFC 4880, section 5.5.2.
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type PublicKey struct {
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CreationTime uint32 // seconds since the epoch
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PubKeyAlgo PublicKeyAlgorithm
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PublicKey interface{} // Either a *rsa.PublicKey or *dsa.PublicKey
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Fingerprint [20]byte
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KeyId uint64
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IsSubKey bool
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n, e, p, q, g, y parsedMPI
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}
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func (pk *PublicKey) parse(r io.Reader) (err os.Error) {
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// RFC 4880, section 5.5.2
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var buf [6]byte
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_, err = readFull(r, buf[:])
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if err != nil {
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return
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}
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if buf[0] != 4 {
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return error.UnsupportedError("public key version")
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}
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pk.CreationTime = uint32(buf[1])<<24 | uint32(buf[2])<<16 | uint32(buf[3])<<8 | uint32(buf[4])
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pk.PubKeyAlgo = PublicKeyAlgorithm(buf[5])
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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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case PubKeyAlgoDSA:
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err = pk.parseDSA(r)
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default:
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err = error.UnsupportedError("public key type")
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}
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if err != nil {
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return
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}
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// RFC 4880, section 12.2
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fingerPrint := sha1.New()
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pk.SerializeSignaturePrefix(fingerPrint)
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pk.Serialize(fingerPrint)
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copy(pk.Fingerprint[:], fingerPrint.Sum())
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pk.KeyId = binary.BigEndian.Uint64(pk.Fingerprint[12:20])
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return
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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 *PublicKey) parseRSA(r io.Reader) (err os.Error) {
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pk.n.bytes, pk.n.bitLength, err = readMPI(r)
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if err != nil {
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return
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}
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pk.e.bytes, pk.e.bitLength, err = readMPI(r)
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if err != nil {
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return
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}
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if len(pk.e.bytes) > 3 {
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err = error.UnsupportedError("large public exponent")
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return
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}
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rsa := &rsa.PublicKey{
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N: new(big.Int).SetBytes(pk.n.bytes),
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E: 0,
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}
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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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// parseRSA parses DSA public key material from the given Reader. See RFC 4880,
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// section 5.5.2.
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func (pk *PublicKey) parseDSA(r io.Reader) (err os.Error) {
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pk.p.bytes, pk.p.bitLength, err = readMPI(r)
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if err != nil {
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return
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}
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pk.q.bytes, pk.q.bitLength, err = readMPI(r)
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if err != nil {
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return
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}
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pk.g.bytes, pk.g.bitLength, err = readMPI(r)
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if err != nil {
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return
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}
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pk.y.bytes, pk.y.bitLength, err = readMPI(r)
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if err != nil {
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return
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}
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dsa := new(dsa.PublicKey)
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dsa.P = new(big.Int).SetBytes(pk.p.bytes)
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dsa.Q = new(big.Int).SetBytes(pk.q.bytes)
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dsa.G = new(big.Int).SetBytes(pk.g.bytes)
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dsa.Y = new(big.Int).SetBytes(pk.y.bytes)
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pk.PublicKey = dsa
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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 *PublicKey) SerializeSignaturePrefix(h hash.Hash) {
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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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case PubKeyAlgoDSA:
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pLength += 2 + uint16(len(pk.p.bytes))
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pLength += 2 + uint16(len(pk.q.bytes))
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pLength += 2 + uint16(len(pk.g.bytes))
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pLength += 2 + uint16(len(pk.y.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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h.Write([]byte{0x99, byte(pLength >> 8), byte(pLength)})
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return
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}
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// Serialize marshals the PublicKey to w in the form of an OpenPGP public key
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// packet, not including the packet header.
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func (pk *PublicKey) Serialize(w io.Writer) (err os.Error) {
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var buf [6]byte
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buf[0] = 4
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buf[1] = byte(pk.CreationTime >> 24)
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buf[2] = byte(pk.CreationTime >> 16)
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buf[3] = byte(pk.CreationTime >> 8)
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buf[4] = byte(pk.CreationTime)
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buf[5] = byte(pk.PubKeyAlgo)
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_, err = w.Write(buf[:])
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if 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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case PubKeyAlgoDSA:
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return writeMPIs(w, pk.p, pk.q, pk.g, pk.y)
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}
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return error.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 *PublicKey) CanSign() bool {
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return pk.PubKeyAlgo != PubKeyAlgoRSAEncryptOnly && pk.PubKeyAlgo != PubKeyAlgoElgamal
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}
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// VerifySignature 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 *PublicKey) VerifySignature(signed hash.Hash, sig *Signature) (err os.Error) {
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if !pk.CanSign() {
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return error.InvalidArgumentError("public key cannot generate signatures")
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}
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rsaPublicKey, ok := pk.PublicKey.(*rsa.PublicKey)
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if !ok {
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// TODO(agl): support DSA and ECDSA keys.
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return error.UnsupportedError("non-RSA public key")
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}
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signed.Write(sig.HashSuffix)
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hashBytes := signed.Sum()
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if hashBytes[0] != sig.HashTag[0] || hashBytes[1] != sig.HashTag[1] {
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return error.SignatureError("hash tag doesn't match")
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}
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err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, sig.Signature)
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if err != nil {
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return error.SignatureError("RSA verification failure")
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}
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return nil
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}
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// VerifyKeySignature returns nil iff sig is a valid signature, make by this
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// public key, of the public key in signed.
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func (pk *PublicKey) VerifyKeySignature(signed *PublicKey, sig *Signature) (err os.Error) {
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h := sig.Hash.New()
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if h == nil {
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return error.UnsupportedError("hash function")
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}
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// RFC 4880, section 5.2.4
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pk.SerializeSignaturePrefix(h)
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pk.Serialize(h)
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signed.SerializeSignaturePrefix(h)
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signed.Serialize(h)
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return pk.VerifySignature(h, sig)
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}
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// VerifyUserIdSignature returns nil iff sig is a valid signature, make by this
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// public key, of the given user id.
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func (pk *PublicKey) VerifyUserIdSignature(id string, sig *Signature) (err os.Error) {
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h := sig.Hash.New()
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if h == nil {
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return error.UnsupportedError("hash function")
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}
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// RFC 4880, section 5.2.4
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pk.SerializeSignaturePrefix(h)
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pk.Serialize(h)
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var buf [5]byte
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buf[0] = 0xb4
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buf[1] = byte(len(id) >> 24)
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buf[2] = byte(len(id) >> 16)
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buf[3] = byte(len(id) >> 8)
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buf[4] = byte(len(id))
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h.Write(buf[:])
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h.Write([]byte(id))
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return pk.VerifySignature(h, sig)
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}
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// A parsedMPI is used to store the contents of a big integer, along with the
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// bit length that was specified in the original input. This allows the MPI to
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// be reserialised exactly.
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type parsedMPI struct {
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bytes []byte
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bitLength uint16
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}
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// writeMPIs is a utility function for serialising several big integers to the
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// given Writer.
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func writeMPIs(w io.Writer, mpis ...parsedMPI) (err os.Error) {
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for _, mpi := range mpis {
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err = writeMPI(w, mpi.bitLength, mpi.bytes)
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if err != nil {
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return
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}
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}
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return
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}
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58
src/pkg/crypto/openpgp/packet/public_key_test.go
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58
src/pkg/crypto/openpgp/packet/public_key_test.go
Normal file
@ -0,0 +1,58 @@
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// Copyright 2011 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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"bytes"
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"encoding/hex"
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"testing"
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)
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var pubKeyTests = []struct {
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hexData string
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hexFingerprint string
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creationTime uint32
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pubKeyAlgo PublicKeyAlgorithm
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keyId uint64
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}{
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{rsaPkDataHex, rsaFingerprintHex, 0x4d3c5c10, PubKeyAlgoRSA, 0xa34d7e18c20c31bb},
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{dsaPkDataHex, dsaFingerprintHex, 0x4d432f89, PubKeyAlgoDSA, 0x8e8fbe54062f19ed},
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}
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func TestPublicKeyRead(t *testing.T) {
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for i, test := range pubKeyTests {
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packet, err := Read(readerFromHex(test.hexData))
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if err != nil {
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t.Errorf("#%d: Read error: %s", i, err)
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return
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}
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pk, ok := packet.(*PublicKey)
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if !ok {
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t.Errorf("#%d: failed to parse, got: %#v", i, packet)
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return
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}
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if pk.PubKeyAlgo != test.pubKeyAlgo {
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t.Errorf("#%d: bad public key algorithm got:%x want:%x", i, pk.PubKeyAlgo, test.pubKeyAlgo)
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}
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if pk.CreationTime != test.creationTime {
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t.Errorf("#%d: bad creation time got:%x want:%x", i, pk.CreationTime, test.creationTime)
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}
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expectedFingerprint, _ := hex.DecodeString(test.hexFingerprint)
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if !bytes.Equal(expectedFingerprint, pk.Fingerprint[:]) {
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t.Errorf("#%d: bad fingerprint got:%x want:%x", i, pk.Fingerprint[:], expectedFingerprint)
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}
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if pk.KeyId != test.keyId {
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t.Errorf("#%d: bad keyid got:%x want:%x", i, pk.KeyId, test.keyId)
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}
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}
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}
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const rsaFingerprintHex = "5fb74b1d03b1e3cb31bc2f8aa34d7e18c20c31bb"
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const rsaPkDataHex = "988d044d3c5c10010400b1d13382944bd5aba23a4312968b5095d14f947f600eb478e14a6fcb16b0e0cac764884909c020bc495cfcc39a935387c661507bdb236a0612fb582cac3af9b29cc2c8c70090616c41b662f4da4c1201e195472eb7f4ae1ccbcbf9940fe21d985e379a5563dde5b9a23d35f1cfaa5790da3b79db26f23695107bfaca8e7b5bcd0011010001"
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const dsaFingerprintHex = "eece4c094db002103714c63c8e8fbe54062f19ed"
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const dsaPkDataHex = "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"
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