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crypto: ensure that VerifySignature rejects malleable signatures #15708

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Merged
karalabe merged 3 commits into from
Dec 20, 2017
Merged

crypto: ensure that VerifySignature rejects malleable signatures #15708

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df04f9e
crypto: ensure that VerifySignature rejects malleable signatures
fjl Dec 18, 2017
b6be57f
crypto: simplify check
fjl Dec 20, 2017
41c854a
crypto: fix build
fjl Dec 20, 2017
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4 changes: 4 additions & 0 deletions crypto/signature_nocgo.go
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
}

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10 changes: 10 additions & 0 deletions crypto/signature_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -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 {
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