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crypto/ecies: make authenticated shared data work

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The s2 parameter was not actually written to the MAC.
This commit is contained in:
Felix Lange
2016-02-09 20:05:49 +01:00
parent b05e472c07
commit fdb936ee95
2 changed files with 36 additions and 6 deletions
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12
crypto/ecies/ecies.go
View File

@@ -192,11 +192,9 @@ func concatKDF(hash hash.Hash, z, s1 []byte, kdLen int) (k []byte, err error) {
// messageTag computes the MAC of a message (called the tag) as per
// SEC 1, 3.5.
func messageTag(hash func() hash.Hash, km, msg, shared []byte) []byte {
if shared == nil {
shared = make([]byte, 0)
}
mac := hmac.New(hash, km)
mac.Write(msg)
mac.Write(shared)
tag := mac.Sum(nil)
return tag
}
@@ -243,9 +241,11 @@ func symDecrypt(rand io.Reader, params *ECIESParams, key, ct []byte) (m []byte,
return
}
// Encrypt encrypts a message using ECIES as specified in SEC 1, 5.1. If
// the shared information parameters aren't being used, they should be
// nil.
// Encrypt encrypts a message using ECIES as specified in SEC 1, 5.1.
//
// s1 and s2 contain shared information that is not part of the resulting
// ciphertext. s1 is fed into key derivation, s2 is fed into the MAC. If the
// shared information parameters aren't being used, they should be nil.
func Encrypt(rand io.Reader, pub *PublicKey, m, s1, s2 []byte) (ct []byte, err error) {
params := pub.Params
if params == nil {

30
crypto/ecies/ecies_test.go
View File

@@ -408,6 +408,36 @@ func TestEncryptDecrypt(t *testing.T) {
}
}
func TestDecryptShared2(t *testing.T) {
prv, err := GenerateKey(rand.Reader, DefaultCurve, nil)
if err != nil {
t.Fatal(err)
}
message := []byte("Hello, world.")
shared2 := []byte("shared data 2")
ct, err := Encrypt(rand.Reader, &prv.PublicKey, message, nil, shared2)
if err != nil {
t.Fatal(err)
}
// Check that decrypting with correct shared data works.
pt, err := prv.Decrypt(rand.Reader, ct, nil, shared2)
if err != nil {
t.Fatal(err)
}
if !bytes.Equal(pt, message) {
t.Fatal("ecies: plaintext doesn't match message")
}
// Decrypting without shared data or incorrect shared data fails.
if _, err = prv.Decrypt(rand.Reader, ct, nil, nil); err == nil {
t.Fatal("ecies: decrypting without shared data didn't fail")
}
if _, err = prv.Decrypt(rand.Reader, ct, nil, []byte("garbage")); err == nil {
t.Fatal("ecies: decrypting with incorrect shared data didn't fail")
}
}
// TestMarshalEncryption validates the encode/decode produces a valid
// ECIES encryption key.
func TestMarshalEncryption(t *testing.T) {