diff options
| author | Hugo Landau <hlandau@openssl.org> | 2022-03-01 14:08:12 +0000 |
|---|---|---|
| committer | Tomas Mraz <tomas@openssl.org> | 2022-03-03 10:32:57 +0100 |
| commit | 8845aeb3ed528491b9eccba365182f90540e5b95 (patch) | |
| tree | fdaaa77b6a6619130e2e0cb7524df539b7a6dec9 | |
| parent | 2d7afbd93dda02feb3435e585c62c04a07a198d3 (diff) | |
Fix NULL pointer dereference for BN_mod_exp2_mont
This fixes a bug whereby BN_mod_exp2_mont can dereference a NULL pointer
if BIGNUM argument m represents zero.
Regression test added. Fixes #17648. Backport from master to 1.1.
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Todd Short <todd.short@me.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17787)
| -rw-r--r-- | crypto/bn/bn_exp2.c | 2 | ||||
| -rw-r--r-- | test/bntest.c | 45 |
2 files changed, 46 insertions, 1 deletions
diff --git a/crypto/bn/bn_exp2.c b/crypto/bn/bn_exp2.c index e542abe46f..de3e249d78 100644 --- a/crypto/bn/bn_exp2.c +++ b/crypto/bn/bn_exp2.c @@ -32,7 +32,7 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1, bn_check_top(p2); bn_check_top(m); - if (!(m->d[0] & 1)) { + if (!BN_is_odd(m)) { BNerr(BN_F_BN_MOD_EXP2_MONT, BN_R_CALLED_WITH_EVEN_MODULUS); return 0; } diff --git a/test/bntest.c b/test/bntest.c index bab34ba54b..390dd80073 100644 --- a/test/bntest.c +++ b/test/bntest.c @@ -2798,6 +2798,50 @@ static int test_mod_exp_consttime(int i) return res; } +/* + * Regression test to ensure BN_mod_exp2_mont fails safely if argument m is + * zero. + */ +static int test_mod_exp2_mont(void) +{ + int res = 0; + BIGNUM *exp_result = NULL; + BIGNUM *exp_a1 = NULL, *exp_p1 = NULL, *exp_a2 = NULL, *exp_p2 = NULL, + *exp_m = NULL; + + if (!TEST_ptr(exp_result = BN_new()) + || !TEST_ptr(exp_a1 = BN_new()) + || !TEST_ptr(exp_p1 = BN_new()) + || !TEST_ptr(exp_a2 = BN_new()) + || !TEST_ptr(exp_p2 = BN_new()) + || !TEST_ptr(exp_m = BN_new())) + goto err; + + if (!TEST_true(BN_one(exp_a1)) + || !TEST_true(BN_one(exp_p1)) + || !TEST_true(BN_one(exp_a2)) + || !TEST_true(BN_one(exp_p2))) + goto err; + + BN_zero(exp_m); + + /* input of 0 is even, so must fail */ + if (!TEST_int_eq(BN_mod_exp2_mont(exp_result, exp_a1, exp_p1, exp_a2, + exp_p2, exp_m, ctx, NULL), 0)) + goto err; + + res = 1; + +err: + BN_free(exp_result); + BN_free(exp_a1); + BN_free(exp_p1); + BN_free(exp_a2); + BN_free(exp_p2); + BN_free(exp_m); + return res; +} + static int file_test_run(STANZA *s) { static const FILETEST filetests[] = { @@ -2906,6 +2950,7 @@ int setup_tests(void) ADD_TEST(test_gcd_prime); ADD_ALL_TESTS(test_mod_exp, (int)OSSL_NELEM(ModExpTests)); ADD_ALL_TESTS(test_mod_exp_consttime, (int)OSSL_NELEM(ModExpTests)); + ADD_TEST(test_mod_exp2_mont); } else { ADD_ALL_TESTS(run_file_tests, n); } |