Merge pull request #3637

6fd7ef2 Also switch the (unused) verification code to low-s instead of even-s. (Pieter Wuille)
This commit is contained in:
Wladimir J. van der Laan 2014-05-09 16:24:46 +02:00
commit 72f754cf51
No known key found for this signature in database
GPG key ID: 74810B012346C9A6
5 changed files with 78 additions and 25 deletions

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@ -332,30 +332,60 @@ public:
}
};
int CompareBigEndian(const unsigned char *c1, size_t c1len, const unsigned char *c2, size_t c2len) {
while (c1len > c2len) {
if (*c1)
return 1;
c1++;
c1len--;
}
while (c2len > c1len) {
if (*c2)
return -1;
c2++;
c2len--;
}
while (c1len > 0) {
if (*c1 > *c2)
return 1;
if (*c2 > *c1)
return -1;
c1++;
c2++;
c1len--;
}
return 0;
}
// Order of secp256k1's generator minus 1.
const unsigned char vchMaxModOrder[32] = {
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFE,
0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,
0xBF,0xD2,0x5E,0x8C,0xD0,0x36,0x41,0x40
};
// Half of the order of secp256k1's generator minus 1.
const unsigned char vchMaxModHalfOrder[32] = {
0x7F,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0x5D,0x57,0x6E,0x73,0x57,0xA4,0x50,0x1D,
0xDF,0xE9,0x2F,0x46,0x68,0x1B,0x20,0xA0
};
const unsigned char vchZero[0] = {};
}; // end of anonymous namespace
bool CKey::Check(const unsigned char *vch) {
// Do not convert to OpenSSL's data structures for range-checking keys,
// it's easy enough to do directly.
static const unsigned char vchMax[32] = {
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFE,
0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,
0xBF,0xD2,0x5E,0x8C,0xD0,0x36,0x41,0x40
};
bool fIsZero = true;
for (int i=0; i<32 && fIsZero; i++)
if (vch[i] != 0)
fIsZero = false;
if (fIsZero)
return false;
for (int i=0; i<32; i++) {
if (vch[i] < vchMax[i])
return true;
if (vch[i] > vchMax[i])
return false;
}
return true;
return CompareBigEndian(vch, 32, vchZero, 0) > 0 &&
CompareBigEndian(vch, 32, vchMaxModOrder, 32) <= 0;
}
bool CKey::CheckSignatureElement(const unsigned char *vch, int len, bool half) {
return CompareBigEndian(vch, len, vchZero, 0) > 0 &&
CompareBigEndian(vch, len, half ? vchMaxModHalfOrder : vchMaxModOrder, 32) <= 0;
}
void CKey::MakeNewKey(bool fCompressedIn) {

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@ -269,6 +269,9 @@ public:
// Load private key and check that public key matches.
bool Load(CPrivKey &privkey, CPubKey &vchPubKey, bool fSkipCheck);
// Check whether an element of a signature (r or s) is valid.
static bool CheckSignatureElement(const unsigned char *vch, int len, bool half);
};
struct CExtPubKey {

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@ -286,9 +286,12 @@ bool IsCanonicalSignature(const valtype &vchSig, unsigned int flags) {
if (nLenS > 1 && (S[0] == 0x00) && !(S[1] & 0x80))
return error("Non-canonical signature: S value excessively padded");
if (flags & SCRIPT_VERIFY_EVEN_S) {
if (S[nLenS-1] & 1)
return error("Non-canonical signature: S value odd");
if (flags & SCRIPT_VERIFY_LOW_S) {
// If the S value is above the order of the curve divided by two, its
// complement modulo the order could have been used instead, which is
// one byte shorter when encoded correctly.
if (!CKey::CheckSignatureElement(S, nLenS, true))
return error("Non-canonical signature: S value is unnecessarily high");
}
return true;

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@ -188,7 +188,7 @@ enum
SCRIPT_VERIFY_NONE = 0,
SCRIPT_VERIFY_P2SH = (1U << 0), // evaluate P2SH (BIP16) subscripts
SCRIPT_VERIFY_STRICTENC = (1U << 1), // enforce strict conformance to DER and SEC2 for signatures and pubkeys
SCRIPT_VERIFY_EVEN_S = (1U << 2), // enforce even S values in signatures (depends on STRICTENC)
SCRIPT_VERIFY_LOW_S = (1U << 2), // enforce low S values (<n/2) in signatures (depends on STRICTENC)
SCRIPT_VERIFY_NOCACHE = (1U << 3), // do not store results in signature cache (but do query it)
SCRIPT_VERIFY_NULLDUMMY = (1U << 4), // verify dummy stack item consumed by CHECKMULTISIG is of zero-length
};

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@ -93,4 +93,21 @@ BOOST_AUTO_TEST_CASE(script_noncanon)
}
}
BOOST_AUTO_TEST_CASE(script_signstrict)
{
for (int i=0; i<100; i++) {
CKey key;
key.MakeNewKey(i & 1);
std::vector<unsigned char> sig;
uint256 hash = GetRandHash();
BOOST_CHECK(key.Sign(hash, sig)); // Generate a random signature.
BOOST_CHECK(key.GetPubKey().Verify(hash, sig)); // Check it.
sig.push_back(0x01); // Append a sighash type.
BOOST_CHECK(IsCanonicalSignature(sig, SCRIPT_VERIFY_STRICTENC | SCRIPT_VERIFY_LOW_S));
BOOST_CHECK(IsCanonicalSignature_OpenSSL(sig));
}
}
BOOST_AUTO_TEST_SUITE_END()