Commit ac35f285 authored by Matt Caswell's avatar Matt Caswell
Browse files

The result of a ^ 0 mod -1 is 0 not 1 



Thanks to Guido Vranken and OSSFuzz for finding this issue.

Reviewed-by: default avatarRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6355)

(cherry picked from commit 4aa5b725)
parent 10fe37dd

crypto/bn/bn_exp.c

+11 −11
Original line number Diff line number Diff line
@@ -188,8 +188,8 @@ int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, 


    bits = BN_num_bits(p);

    if (bits == 0) {

        /* x**0 mod 1 is still zero. */

        if (BN_is_one(m)) {

        /* x**0 mod 1, or x**0 mod -1 is still zero. */

        if (BN_abs_is_word(m, 1)) {

            ret = 1;

            BN_zero(r);

        } else {
@@ -330,8 +330,8 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, 
    }

    bits = BN_num_bits(p);

    if (bits == 0) {

        /* x**0 mod 1 is still zero. */

        if (BN_is_one(m)) {

        /* x**0 mod 1, or x**0 mod -1 is still zero. */

        if (BN_abs_is_word(m, 1)) {

            ret = 1;

            BN_zero(rr);

        } else {
@@ -639,8 +639,8 @@ int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, 
     */

    bits = p->top * BN_BITS2;

    if (bits == 0) {

        /* x**0 mod 1 is still zero. */

        if (BN_is_one(m)) {

        /* x**0 mod 1, or x**0 mod -1 is still zero. */

        if (BN_abs_is_word(m, 1)) {

            ret = 1;

            BN_zero(rr);

        } else {
@@ -1151,8 +1151,8 @@ int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p, 


    bits = BN_num_bits(p);

    if (bits == 0) {

        /* x**0 mod 1 is still zero. */

        if (BN_is_one(m)) {

        /* x**0 mod 1, or x**0 mod -1 is still zero. */

        if (BN_abs_is_word(m, 1)) {

            ret = 1;

            BN_zero(rr);

        } else {
@@ -1274,8 +1274,8 @@ int BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, 


    bits = BN_num_bits(p);

    if (bits == 0) {

        /* x**0 mod 1 is still zero. */

        if (BN_is_one(m)) {

        /* x**0 mod 1, or x**0 mod -1 is still zero. */

        if (BN_abs_is_word(m, 1)) {

            ret = 1;

            BN_zero(r);

        } else {