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// 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 (
"big"
"bytes"
"crypto/cipher"
"crypto/dsa"
"crypto/openpgp/error"
"crypto/openpgp/s2k"
"crypto/rsa"
"crypto/sha1"
"io"
"io/ioutil"
"os"
"strconv"
)
// PrivateKey represents a possibly encrypted private key. See RFC 4880,
// section 5.5.3.
type PrivateKey struct {
PublicKey
Encrypted bool // if true then the private key is unavailable until Decrypt has been called.
encryptedData []byte
cipher CipherFunction
s2k func(out, in []byte)
PrivateKey interface{} // An *rsa.PrivateKey.
sha1Checksum bool
iv []byte
}
func (pk *PrivateKey) parse(r io.Reader) (err os.Error) {
err = (&pk.PublicKey).parse(r)
if err != nil {
return
}
var buf [1]byte
_, err = readFull(r, buf[:])
if err != nil {
return
}
s2kType := buf[0]
switch s2kType {
case 0:
pk.s2k = nil
pk.Encrypted = false
case 254, 255:
_, err = readFull(r, buf[:])
if err != nil {
return
}
pk.cipher = CipherFunction(buf[0])
pk.Encrypted = true
pk.s2k, err = s2k.Parse(r)
if err != nil {
return
}
if s2kType == 254 {
pk.sha1Checksum = true
}
default:
return error.UnsupportedError("deprecated s2k function in private key")
}
if pk.Encrypted {
blockSize := pk.cipher.blockSize()
if blockSize == 0 {
return error.UnsupportedError("unsupported cipher in private key: " + strconv.Itoa(int(pk.cipher)))
}
pk.iv = make([]byte, blockSize)
_, err = readFull(r, pk.iv)
if err != nil {
return
}
}
pk.encryptedData, err = ioutil.ReadAll(r)
if err != nil {
return
}
if !pk.Encrypted {
return pk.parsePrivateKey(pk.encryptedData)
}
return
}
// Decrypt decrypts an encrypted private key using a passphrase.
func (pk *PrivateKey) Decrypt(passphrase []byte) os.Error {
if !pk.Encrypted {
return nil
}
key := make([]byte, pk.cipher.keySize())
pk.s2k(key, passphrase)
block := pk.cipher.new(key)
cfb := cipher.NewCFBDecrypter(block, pk.iv)
data := pk.encryptedData
cfb.XORKeyStream(data, data)
if pk.sha1Checksum {
if len(data) < sha1.Size {
return error.StructuralError("truncated private key data")
}
h := sha1.New()
h.Write(data[:len(data)-sha1.Size])
sum := h.Sum()
if !bytes.Equal(sum, data[len(data)-sha1.Size:]) {
return error.StructuralError("private key checksum failure")
}
data = data[:len(data)-sha1.Size]
} else {
if len(data) < 2 {
return error.StructuralError("truncated private key data")
}
var sum uint16
for i := 0; i < len(data)-2; i++ {
sum += uint16(data[i])
}
if data[len(data)-2] != uint8(sum>>8) ||
data[len(data)-1] != uint8(sum) {
return error.StructuralError("private key checksum failure")
}
data = data[:len(data)-2]
}
return pk.parsePrivateKey(data)
}
func (pk *PrivateKey) parsePrivateKey(data []byte) (err os.Error) {
switch pk.PublicKey.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly, PubKeyAlgoRSAEncryptOnly:
return pk.parseRSAPrivateKey(data)
case PubKeyAlgoDSA:
return pk.parseDSAPrivateKey(data)
}
panic("impossible")
}
func (pk *PrivateKey) parseRSAPrivateKey(data []byte) (err os.Error) {
rsaPub := pk.PublicKey.PublicKey.(*rsa.PublicKey)
rsaPriv := new(rsa.PrivateKey)
rsaPriv.PublicKey = *rsaPub
buf := bytes.NewBuffer(data)
d, _, err := readMPI(buf)
if err != nil {
return
}
p, _, err := readMPI(buf)
if err != nil {
return
}
q, _, err := readMPI(buf)
if err != nil {
return
}
rsaPriv.D = new(big.Int).SetBytes(d)
rsaPriv.Primes = make([]*big.Int, 2)
rsaPriv.Primes[0] = new(big.Int).SetBytes(p)
rsaPriv.Primes[1] = new(big.Int).SetBytes(q)
rsaPriv.Precompute()
pk.PrivateKey = rsaPriv
pk.Encrypted = false
pk.encryptedData = nil
return nil
}
func (pk *PrivateKey) parseDSAPrivateKey(data []byte) (err os.Error) {
dsaPub := pk.PublicKey.PublicKey.(*dsa.PublicKey)
dsaPriv := new(dsa.PrivateKey)
dsaPriv.PublicKey = *dsaPub
buf := bytes.NewBuffer(data)
x, _, err := readMPI(buf)
if err != nil {
return
}
dsaPriv.X = new(big.Int).SetBytes(x)
pk.PrivateKey = dsaPriv
pk.Encrypted = false
pk.encryptedData = nil
return nil
}
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