forked from dgryski/dkeyczar
/
dsa_key.go
225 lines (208 loc) · 5.34 KB
/
dsa_key.go
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package dkeyczar
import (
"crypto/dsa"
"crypto/rand"
"crypto/sha1"
"encoding/asn1"
"encoding/binary"
"encoding/json"
"math/big"
)
type dsaPublicKeyJSON struct {
Q string `json:"q"`
P string `json:"p"`
Y string `json:"y"`
G string `json:"g"`
Size uint `json:"size"`
}
type dsaPublicKey struct {
key dsa.PublicKey
id []byte
}
type dsaKeyJSON struct {
PublicKey dsaPublicKeyJSON `json:"publicKey"`
Size uint `json:"size"`
X string `json:"x"`
}
type dsaKey struct {
key dsa.PrivateKey
publicKey dsaPublicKey
}
func generateDSAKey(size uint) (*dsaKey, error) {
dsakey := new(dsaKey)
if size == 0 {
size = T_DSA_PRIV.defaultSize()
}
if !T_DSA_PRIV.isAcceptableSize(size) {
return nil, ErrInvalidKeySize
}
var psz dsa.ParameterSizes
switch size {
case 1024:
psz = dsa.L1024N160
default:
panic("unknown dsa key size")
}
err := dsa.GenerateParameters(&dsakey.key.PublicKey.Parameters, rand.Reader, psz)
if err != nil {
return nil, err
}
err = dsa.GenerateKey(&dsakey.key, rand.Reader)
if err != nil {
return nil, err
}
dsakey.publicKey.key = dsakey.key.PublicKey
return dsakey, nil
}
func newDSAPublicKeyFromJSON(s []byte) (*dsaPublicKey, error) {
dsakey := new(dsaPublicKey)
dsajson := new(dsaPublicKeyJSON)
var err error
err = json.Unmarshal([]byte(s), &dsajson)
if err != nil {
return nil, err
}
if !T_DSA_PUB.isAcceptableSize(dsajson.Size) {
return nil, ErrInvalidKeySize
}
b, err := decodeWeb64String(dsajson.Y)
if err != nil {
return nil, ErrBase64Decoding
}
dsakey.key.Y = big.NewInt(0).SetBytes(b)
b, err = decodeWeb64String(dsajson.G)
if err != nil {
return nil, ErrBase64Decoding
}
dsakey.key.G = big.NewInt(0).SetBytes(b)
b, err = decodeWeb64String(dsajson.P)
if err != nil {
return nil, ErrBase64Decoding
}
dsakey.key.P = big.NewInt(0).SetBytes(b)
b, err = decodeWeb64String(dsajson.Q)
if err != nil {
return nil, ErrBase64Decoding
}
dsakey.key.Q = big.NewInt(0).SetBytes(b)
return dsakey, nil
}
func newDSAJSONFromKey(key *dsa.PrivateKey) *dsaKeyJSON {
dsajson := new(dsaKeyJSON)
dsajson.PublicKey.P = encodeWeb64String(bigIntBytes(key.P))
dsajson.PublicKey.Q = encodeWeb64String(bigIntBytes(key.Q))
dsajson.PublicKey.Y = encodeWeb64String(bigIntBytes(key.Y))
dsajson.PublicKey.G = encodeWeb64String(bigIntBytes(key.G))
dsajson.X = encodeWeb64String(bigIntBytes(key.X))
dsajson.Size = uint(len(key.P.Bytes())) * 8
dsajson.PublicKey.Size = uint(len(key.P.Bytes())) * 8
return dsajson
}
func (dk *dsaKey) ToKeyJSON() []byte {
j := newDSAJSONFromKey(&dk.key)
s, _ := json.Marshal(j)
return s
}
func newDSAPublicJSONFromKey(key *dsa.PublicKey) *dsaPublicKeyJSON {
dsajson := new(dsaPublicKeyJSON)
dsajson.P = encodeWeb64String(bigIntBytes(key.P))
dsajson.Q = encodeWeb64String(bigIntBytes(key.Q))
dsajson.Y = encodeWeb64String(bigIntBytes(key.Y))
dsajson.G = encodeWeb64String(bigIntBytes(key.G))
dsajson.Size = uint(len(key.P.Bytes())) * 8
return dsajson
}
func (dk *dsaPublicKey) ToKeyJSON() []byte {
j := newDSAPublicJSONFromKey(&dk.key)
s, _ := json.Marshal(j)
return s
}
func newDSAKeyFromJSON(s []byte) (*dsaKey, error) {
dsakey := new(dsaKey)
dsajson := new(dsaKeyJSON)
var err error
err = json.Unmarshal([]byte(s), &dsajson)
if err != nil {
return nil, err
}
if !T_DSA_PRIV.isAcceptableSize(dsajson.Size) || !T_DSA_PUB.isAcceptableSize(dsajson.PublicKey.Size) {
return nil, ErrInvalidKeySize
}
b, err := decodeWeb64String(dsajson.X)
if err != nil {
return nil, ErrBase64Decoding
}
dsakey.key.X = big.NewInt(0).SetBytes(b)
b, err = decodeWeb64String(dsajson.PublicKey.Y)
if err != nil {
return nil, ErrBase64Decoding
}
dsakey.key.Y = big.NewInt(0).SetBytes(b)
dsakey.publicKey.key.Y = dsakey.key.Y
b, err = decodeWeb64String(dsajson.PublicKey.G)
if err != nil {
return nil, ErrBase64Decoding
}
dsakey.key.G = big.NewInt(0).SetBytes(b)
dsakey.publicKey.key.G = dsakey.key.G
b, err = decodeWeb64String(dsajson.PublicKey.P)
if err != nil {
return nil, ErrBase64Decoding
}
dsakey.key.P = big.NewInt(0).SetBytes(b)
dsakey.publicKey.key.P = dsakey.key.P
b, err = decodeWeb64String(dsajson.PublicKey.Q)
if err != nil {
return nil, ErrBase64Decoding
}
dsakey.key.Q = big.NewInt(0).SetBytes(b)
dsakey.publicKey.key.Q = dsakey.key.Q
return dsakey, nil
}
func (dk *dsaPublicKey) KeyID() []byte {
if len(dk.id) != 0 {
return dk.id
}
h := sha1.New()
for _, n := range []*big.Int{dk.key.P, dk.key.Q, dk.key.G, dk.key.Y} {
b := n.Bytes()
binary.Write(h, binary.BigEndian, uint32(len(b)))
h.Write(b)
}
dk.id = h.Sum(nil)[:4]
return dk.id
}
func (dk *dsaKey) KeyID() []byte {
return dk.publicKey.KeyID()
}
type dsaSignature struct {
R *big.Int
S *big.Int
}
func (dk *dsaKey) Sign(msg []byte) ([]byte, error) {
h := sha1.New()
h.Write(msg)
r, s, err := dsa.Sign(rand.Reader, &dk.key, h.Sum(nil))
if err != nil {
return nil, err
}
sig := dsaSignature{r, s}
b, err := asn1.Marshal(sig)
if err != nil {
return nil, err
}
return b, nil
}
func (dk *dsaKey) Verify(msg []byte, signature []byte) (bool, error) {
return dk.publicKey.Verify(msg, signature)
}
func (dk *dsaPublicKey) Verify(msg []byte, signature []byte) (bool, error) {
h := sha1.New()
h.Write(msg)
var rs dsaSignature
_, err := asn1.Unmarshal(signature, &rs)
if err != nil {
return false, err
}
return dsa.Verify(&dk.key, h.Sum(nil), rs.R, rs.S), nil
}