Merge pull request #2 from Gustav-Simonsson/correct_ecies_shared_key_generation

Correct ECIES shared key length check
This commit is contained in:
Jeffrey Wilcke 2015-02-12 00:10:00 +01:00
commit 04c1a81509

View File

@ -17,7 +17,8 @@ var (
ErrInvalidCurve = fmt.Errorf("ecies: invalid elliptic curve")
ErrInvalidParams = fmt.Errorf("ecies: invalid ECIES parameters")
ErrInvalidPublicKey = fmt.Errorf("ecies: invalid public key")
ErrSharedKeyTooBig = fmt.Errorf("ecies: shared key is too big")
ErrSharedKeyIsPointAtInfinity = fmt.Errorf("ecies: shared key is point at infinity")
ErrSharedKeyTooBig = fmt.Errorf("ecies: shared key params are too big")
)
// PublicKey is a representation of an elliptic curve public key.
@ -90,16 +91,20 @@ func MaxSharedKeyLength(pub *PublicKey) int {
// ECDH key agreement method used to establish secret keys for encryption.
func (prv *PrivateKey) GenerateShared(pub *PublicKey, skLen, macLen int) (sk []byte, err error) {
if prv.PublicKey.Curve != pub.Curve {
err = ErrInvalidCurve
return
return nil, ErrInvalidCurve
}
if skLen+macLen > MaxSharedKeyLength(pub) {
return nil, ErrSharedKeyTooBig
}
x, _ := pub.Curve.ScalarMult(pub.X, pub.Y, prv.D.Bytes())
if x == nil || (x.BitLen()+7)/8 < (skLen+macLen) {
err = ErrSharedKeyTooBig
return
if x == nil {
return nil, ErrSharedKeyIsPointAtInfinity
}
sk = x.Bytes()[:skLen+macLen]
return
sk = make([]byte, skLen+macLen)
skBytes := x.Bytes()
copy(sk[len(sk)-len(skBytes):], skBytes)
return sk, nil
}
var (