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-rw-r--r--security/nss/fuzz/mpi_expmod_target.cc9
1 files changed, 9 insertions, 0 deletions
diff --git a/security/nss/fuzz/mpi_expmod_target.cc b/security/nss/fuzz/mpi_expmod_target.cc
index ed31da354..b9be5854f 100644
--- a/security/nss/fuzz/mpi_expmod_target.cc
+++ b/security/nss/fuzz/mpi_expmod_target.cc
@@ -19,6 +19,15 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
auto modulus = get_modulus(data, size, ctx);
// Compare with OpenSSL exp mod
m1 = &std::get<1>(modulus);
+ // The exponent b (B) can get really big. Make it smaller if necessary.
+ if (MP_USED(&b) > 100) {
+ size_t shift = (MP_USED(&b) - 100) * MP_DIGIT_BIT;
+ mp_div_2d(&b, shift, &b, nullptr);
+ BN_rshift(B, B, shift);
+ }
+ check_equal(A, &a, max_size);
+ check_equal(B, &b, max_size);
+ check_equal(std::get<0>(modulus), m1, 3 * max_size);
assert(mp_exptmod(&a, &b, m1, &c) == MP_OKAY);
(void)BN_mod_exp(C, A, B, std::get<0>(modulus), ctx);
check_equal(C, &c, 2 * max_size);