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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/* Helper functions for MPI fuzzing targets. */
#include "mpi_helper.h"
#include <cstdlib>
#include <random>
char *to_char(const uint8_t *x) {
return reinterpret_cast<char *>(const_cast<unsigned char *>(x));
}
void print_bn(std::string label, BIGNUM *x) {
char *xc = BN_bn2hex(x);
std::cout << label << ": " << std::hex << xc << std::endl;
OPENSSL_free(xc);
}
// Check that the two numbers are equal.
void check_equal(BIGNUM *b, mp_int *m, size_t max_size) {
char *bnBc = BN_bn2hex(b);
char mpiMc[max_size];
mp_tohex(m, mpiMc);
std::string bnA(bnBc);
std::string mpiA(mpiMc);
OPENSSL_free(bnBc);
// We have to strip leading zeros from bignums, ignoring the sign.
if (bnA.at(0) != '-') {
bnA.erase(0, std::min(bnA.find_first_not_of('0'), bnA.size() - 1));
} else if (bnA.at(1) == '0') {
bnA.erase(1, std::min(bnA.find_first_not_of('0', 1) - 1, bnA.size() - 1));
}
if (mpiA != bnA) {
std::cout << "openssl: " << std::hex << bnA << std::endl;
std::cout << "nss: " << std::hex << mpiA << std::endl;
}
assert(mpiA == bnA);
}
// Parse data into two numbers for MPI and OpenSSL Bignum.
void parse_input(const uint8_t *data, size_t size, BIGNUM *A, BIGNUM *B,
mp_int *a, mp_int *b) {
// Note that b might overlap a.
size_t len = (size_t)size / 2;
assert(mp_read_raw(a, to_char(data), len) == MP_OKAY);
assert(mp_read_raw(b, to_char(data) + len, len) == MP_OKAY);
// Force a positive sign.
// TODO: add tests for negatives.
MP_SIGN(a) = MP_ZPOS;
MP_SIGN(b) = MP_ZPOS;
// Skip the first byte as it's interpreted as sign by NSS.
assert(BN_bin2bn(data + 1, len - 1, A) != nullptr);
assert(BN_bin2bn(data + len + 1, len - 1, B) != nullptr);
check_equal(A, a, 2 * size + 1);
check_equal(B, b, 2 * size + 1);
}
// Parse data into a number for MPI and OpenSSL Bignum.
void parse_input(const uint8_t *data, size_t size, BIGNUM *A, mp_int *a) {
assert(mp_read_raw(a, to_char(data), size) == MP_OKAY);
// Force a positive sign.
// TODO: add tests for negatives.
MP_SIGN(a) = MP_ZPOS;
// Skip the first byte as it's interpreted as sign by NSS.
assert(BN_bin2bn(data + 1, size - 1, A) != nullptr);
check_equal(A, a, 4 * size + 1);
}
// Take a chunk in the middle of data and use it as modulus.
std::tuple<BIGNUM *, mp_int> get_modulus(const uint8_t *data, size_t size,
BN_CTX *ctx) {
BIGNUM *r1 = BN_CTX_get(ctx);
mp_int r2;
assert(mp_init(&r2) == MP_OKAY);
size_t len = static_cast<size_t>(size / 4);
if (len != 0) {
assert(mp_read_raw(&r2, to_char(data + len), len) == MP_OKAY);
MP_SIGN(&r2) = MP_ZPOS;
assert(BN_bin2bn(data + len + 1, len - 1, r1) != nullptr);
check_equal(r1, &r2, 2 * len + 1);
}
// If we happen to get 0 for the modulus, take a random number.
if (mp_cmp_z(&r2) == 0 || len == 0) {
mp_zero(&r2);
BN_zero(r1);
std::mt19937 rng(data[0]);
std::uniform_int_distribution<mp_digit> dist(1, MP_DIGIT_MAX);
mp_digit x = dist(rng);
mp_add_d(&r2, x, &r2);
BN_add_word(r1, x);
}
return std::make_tuple(r1, r2);
}
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