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bulletproofs: a few fixes from the Kudelski review

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- fix integer overflow in n_bulletproof_amounts
- check input scalars are in range
- remove use of environment variable to tweak straus performance
- do not use implementation defined signed shift for signum
This commit is contained in:
moneromooo-monero 2018-07-16 14:40:51 +01:00
parent c429176248
commit 869b3bf824
No known key found for this signature in database
GPG Key ID: 686F07454D6CEFC3
4 changed files with 23 additions and 15 deletions
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3
src/crypto/crypto-ops.c
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@ -3707,9 +3707,8 @@ void sc_muladd(unsigned char *s, const unsigned char *a, const unsigned char *b,
s[31] = s11 >> 17;
}
/* Assumes that a != INT64_MIN */
static int64_t signum(int64_t a) {
return (a >> 63) - ((-a) >> 63);
return a > 0 ? 1 : a < 0 ? -1 : 0;
}
int sc_check(const unsigned char *s) {

23
src/ringct/bulletproofs.cc
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@ -74,14 +74,20 @@ static boost::mutex init_mutex;
static inline rct::key multiexp(const std::vector<MultiexpData> &data, bool HiGi)
{
static const size_t STEP = getenv("STRAUS_STEP") ? atoi(getenv("STRAUS_STEP")) : 0;
if (HiGi)
{
static_assert(128 <= STRAUS_SIZE_LIMIT, "Straus in precalc mode can only be calculated till STRAUS_SIZE_LIMIT");
return data.size() <= 128 ? straus(data, straus_HiGi_cache, STEP) : pippenger(data, pippenger_HiGi_cache, get_pippenger_c(data.size()));
return data.size() <= 128 ? straus(data, straus_HiGi_cache, 0) : pippenger(data, pippenger_HiGi_cache, get_pippenger_c(data.size()));
}
else
return data.size() <= 64 ? straus(data, NULL, STEP) : pippenger(data, NULL, get_pippenger_c(data.size()));
return data.size() <= 64 ? straus(data, NULL, 0) : pippenger(data, NULL, get_pippenger_c(data.size()));
}
static bool is_reduced(const rct::key &scalar)
{
rct::key reduced = scalar;
sc_reduce32(reduced.bytes);
return scalar == reduced;
}
//addKeys3acc_p3
@ -659,6 +665,10 @@ Bulletproof bulletproof_PROVE(const rct::keyV &sv, const rct::keyV &gamma)
{
CHECK_AND_ASSERT_THROW_MES(sv.size() == gamma.size(), "Incompatible sizes of sv and gamma");
CHECK_AND_ASSERT_THROW_MES(!sv.empty(), "sv is empty");
for (const rct::key &sve: sv)
CHECK_AND_ASSERT_THROW_MES(is_reduced(sve), "Invalid sv input");
for (const rct::key &g: gamma)
CHECK_AND_ASSERT_THROW_MES(is_reduced(g), "Invalid gamma input");
init_exponents();
@ -935,6 +945,13 @@ bool bulletproof_VERIFY(const std::vector<const Bulletproof*> &proofs)
CHECK_AND_ASSERT_MES(rct::isInMainSubgroup(proof.T1), false, "Input point not in subgroup");
CHECK_AND_ASSERT_MES(rct::isInMainSubgroup(proof.T2), false, "Input point not in subgroup");
// check scalar range
CHECK_AND_ASSERT_MES(is_reduced(proof.taux), false, "Input scalar not in range");
CHECK_AND_ASSERT_MES(is_reduced(proof.mu), false, "Input scalar not in range");
CHECK_AND_ASSERT_MES(is_reduced(proof.a), false, "Input scalar not in range");
CHECK_AND_ASSERT_MES(is_reduced(proof.b), false, "Input scalar not in range");
CHECK_AND_ASSERT_MES(is_reduced(proof.t), false, "Input scalar not in range");
CHECK_AND_ASSERT_MES(proof.V.size() >= 1, false, "V does not have at least one element");
CHECK_AND_ASSERT_MES(proof.L.size() == proof.R.size(), false, "Mismatched L and R sizes");
CHECK_AND_ASSERT_MES(proof.L.size() > 0, false, "Empty proof");

2
src/ringct/rctTypes.cpp
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@ -236,6 +236,7 @@ namespace rct {
size_t n_bulletproof_amounts(const Bulletproof &proof)
{
CHECK_AND_ASSERT_MES(proof.L.size() >= 6, 0, "Invalid bulletproof L size");
CHECK_AND_ASSERT_MES(proof.L.size() <= 31, 0, "Insane bulletproof L size");
return 1 << (proof.L.size() - 6);
}
@ -245,6 +246,7 @@ namespace rct {
for (const Bulletproof &proof: proofs)
{
size_t n2 = n_bulletproof_amounts(proof);
CHECK_AND_ASSERT_MES(n2 < std::numeric_limits<uint32_t>::max() - n, 0, "Invalid number of bulletproofs");
if (n2 == 0)
return 0;
n += n2;

10
tests/unit_tests/bulletproofs.cpp
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@ -185,16 +185,6 @@ TEST(bulletproofs, invalid_gamma_0)
ASSERT_FALSE(rct::bulletproof_VERIFY(proof));
}
TEST(bulletproofs, invalid_gamma_ff)
{
rct::key invalid_amount = rct::zero();
invalid_amount[8] = 1;
rct::key gamma = rct::zero();
memset(&gamma, 0xff, sizeof(gamma));
rct::Bulletproof proof = bulletproof_PROVE(invalid_amount, gamma);
ASSERT_FALSE(rct::bulletproof_VERIFY(proof));
}
static const char * const torsion_elements[] =
{
"c7176a703d4dd84fba3c0b760d10670f2a2053fa2c39ccc64ec7fd7792ac03fa",