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crypto: ensure that VerifySignature rejects malleable signatures (#15708) 

* crypto: ensure that VerifySignature rejects malleable signatures

It already rejected them when using libsecp256k1, make sure the nocgo
version does the same thing.

* crypto: simplify check

* crypto: fix build
This commit is contained in:
Felix Lange 2017-12-20 13:30:00 +01:00 committed by Péter Szilágyi
parent 5e1581c2c3
commit ce823c9f84
2 changed files with 14 additions and 0 deletions
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4
crypto/signature_nocgo.go
View File

@ -87,6 +87,10 @@ func VerifySignature(pubkey, hash, signature []byte) bool {
if err != nil {
return false
}
// Reject malleable signatures. libsecp256k1 does this check but btcec doesn't.
if sig.S.Cmp(secp256k1_halfN) > 0 {
return false
}
return sig.Verify(hash, key)
}

10
crypto/signature_test.go
View File

@ -75,6 +75,16 @@ func TestVerifySignature(t *testing.T) {
}
}
// This test checks that VerifySignature rejects malleable signatures with s > N/2.
func TestVerifySignatureMalleable(t *testing.T) {
sig := hexutil.MustDecode("0x638a54215d80a6713c8d523a6adc4e6e73652d859103a36b700851cb0e61b66b8ebfc1a610c57d732ec6e0a8f06a9a7a28df5051ece514702ff9cdff0b11f454")
key := hexutil.MustDecode("0x03ca634cae0d49acb401d8a4c6b6fe8c55b70d115bf400769cc1400f3258cd3138")
msg := hexutil.MustDecode("0xd301ce462d3e639518f482c7f03821fec1e602018630ce621e1e7851c12343a6")
if VerifySignature(key, msg, sig) {
t.Error("VerifySignature returned true for malleable signature")
}
}
func TestDecompressPubkey(t *testing.T) {
key, err := DecompressPubkey(testpubkeyc)
if err != nil {