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bulletproofs: reject x, y, z, or w[i] being zero 

Also try again when we're generate a proof with those characteristics

Reported by QuarksLab.
This commit is contained in:
moneromooo-monero 2018-07-24 19:56:48 +01:00
parent 5ffb2ff9b7
commit fe0fa3b9c5
No known key found for this signature in database
GPG Key ID: 686F07454D6CEFC3
1 changed files with 63 additions and 2 deletions
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65
src/ringct/bulletproofs.cc
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@ -473,6 +473,7 @@ Bulletproof bulletproof_PROVE(const rct::key &sv, const rct::key &gamma)
CHECK_AND_ASSERT_THROW_MES(test_aR == v_test, "test_aR failed");
#endif
try_again:
PERF_TIMER_START_BP(PROVE_step1);
// PAPER LINES 38-39
rct::key alpha = rct::skGen();
@ -489,7 +490,19 @@ Bulletproof bulletproof_PROVE(const rct::key &sv, const rct::key &gamma)
// PAPER LINES 43-45
rct::key y = hash_cache_mash(hash_cache, A, S);
if (y == rct::zero())
{
PERF_TIMER_STOP(PROVE_step1);
MINFO("y is 0, trying again");
goto try_again;
}
rct::key z = hash_cache = rct::hash_to_scalar(y);
if (z == rct::zero())
{
PERF_TIMER_STOP(PROVE_step1);
MINFO("z is 0, trying again");
goto try_again;
}
// Polynomial construction before PAPER LINE 46
rct::key t0 = rct::zero();
@ -552,6 +565,12 @@ Bulletproof bulletproof_PROVE(const rct::key &sv, const rct::key &gamma)
// PAPER LINES 49-51
rct::key x = hash_cache_mash(hash_cache, z, T1, T2);
if (x == rct::zero())
{
PERF_TIMER_STOP(PROVE_step2);
MINFO("x is 0, trying again");
goto try_again;
}
// PAPER LINES 52-53
rct::key taux = rct::zero();
@ -625,6 +644,12 @@ Bulletproof bulletproof_PROVE(const rct::key &sv, const rct::key &gamma)
// PAPER LINES 21-22
w[round] = hash_cache_mash(hash_cache, L[round], R[round]);
if (w[round] == rct::zero())
{
PERF_TIMER_STOP(PROVE_step4);
MINFO("w[round] is 0, trying again");
goto try_again;
}
// PAPER LINES 24-25
const rct::key winv = invert(w[round]);
@ -713,8 +738,6 @@ Bulletproof bulletproof_PROVE(const rct::keyV &sv, const rct::keyV &gamma)
}
PERF_TIMER_STOP(PROVE_aLaR);
rct::key hash_cache = rct::hash_to_scalar(V);
// DEBUG: Test to ensure this recovers the value
#ifdef DEBUG_BP
for (size_t j = 0; j < M; ++j)
@ -735,6 +758,9 @@ Bulletproof bulletproof_PROVE(const rct::keyV &sv, const rct::keyV &gamma)
}
#endif
try_again:
rct::key hash_cache = rct::hash_to_scalar(V);
PERF_TIMER_START_BP(PROVE_step1);
// PAPER LINES 38-39
rct::key alpha = rct::skGen();
@ -751,7 +777,19 @@ Bulletproof bulletproof_PROVE(const rct::keyV &sv, const rct::keyV &gamma)
// PAPER LINES 43-45
rct::key y = hash_cache_mash(hash_cache, A, S);
if (y == rct::zero())
{
PERF_TIMER_STOP(PROVE_step1);
MINFO("y is 0, trying again");
goto try_again;
}
rct::key z = hash_cache = rct::hash_to_scalar(y);
if (z == rct::zero())
{
PERF_TIMER_STOP(PROVE_step1);
MINFO("z is 0, trying again");
goto try_again;
}
// Polynomial construction by coefficients
const auto zMN = vector_dup(z, MN);
@ -799,6 +837,12 @@ Bulletproof bulletproof_PROVE(const rct::keyV &sv, const rct::keyV &gamma)
// PAPER LINES 49-51
rct::key x = hash_cache_mash(hash_cache, z, T1, T2);
if (x == rct::zero())
{
PERF_TIMER_STOP(PROVE_step2);
MINFO("x is 0, trying again");
goto try_again;
}
// PAPER LINES 52-53
rct::key taux;
@ -835,6 +879,12 @@ Bulletproof bulletproof_PROVE(const rct::keyV &sv, const rct::keyV &gamma)
// PAPER LINES 32-33
rct::key x_ip = hash_cache_mash(hash_cache, x, taux, mu, t);
if (x_ip == rct::zero())
{
PERF_TIMER_STOP(PROVE_step3);
MINFO("x_ip is 0, trying again");
goto try_again;
}
// These are used in the inner product rounds
size_t nprime = MN;
@ -879,6 +929,12 @@ Bulletproof bulletproof_PROVE(const rct::keyV &sv, const rct::keyV &gamma)
// PAPER LINES 21-22
w[round] = hash_cache_mash(hash_cache, L[round], R[round]);
if (w[round] == rct::zero())
{
PERF_TIMER_STOP(PROVE_step4);
MINFO("w[round] is 0, trying again");
goto try_again;
}
// PAPER LINES 24-25
const rct::key winv = invert(w[round]);
@ -985,9 +1041,13 @@ bool bulletproof_VERIFY(const std::vector<const Bulletproof*> &proofs)
PERF_TIMER_START_BP(VERIFY_start);
rct::key hash_cache = rct::hash_to_scalar(proof.V);
rct::key y = hash_cache_mash(hash_cache, proof.A, proof.S);
CHECK_AND_ASSERT_MES(!(y == rct::zero()), false, "y == 0");
rct::key z = hash_cache = rct::hash_to_scalar(y);
CHECK_AND_ASSERT_MES(!(z == rct::zero()), false, "z == 0");
rct::key x = hash_cache_mash(hash_cache, z, proof.T1, proof.T2);
CHECK_AND_ASSERT_MES(!(x == rct::zero()), false, "x == 0");
rct::key x_ip = hash_cache_mash(hash_cache, x, proof.taux, proof.mu, proof.t);
CHECK_AND_ASSERT_MES(!(x_ip == rct::zero()), false, "x_ip == 0");
PERF_TIMER_STOP(VERIFY_start);
PERF_TIMER_START_BP(VERIFY_line_61);
@ -1082,6 +1142,7 @@ bool bulletproof_VERIFY(const std::vector<const Bulletproof*> &proofs)
for (size_t i = 0; i < rounds; ++i)
{
w[i] = hash_cache_mash(hash_cache, proof.L[i], proof.R[i]);
CHECK_AND_ASSERT_MES(!(w[i] == rct::zero()), false, "w[i] == 0");
}
PERF_TIMER_STOP(VERIFY_line_21_22);