diff options
| -rw-r--r-- | crypto/bn/bn_gcd.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/crypto/bn/bn_gcd.c b/crypto/bn/bn_gcd.c index fbefe4ab6a..bed9fca4d9 100644 --- a/crypto/bn/bn_gcd.c +++ b/crypto/bn/bn_gcd.c @@ -593,7 +593,9 @@ int BN_gcd(BIGNUM *r, const BIGNUM *in_a, const BIGNUM *in_b, BN_CTX *ctx) for (i = 0; i < m; i++) { /* conditionally flip signs if delta is positive and g is odd */ - cond = (-delta >> (8 * sizeof(delta) - 1)) & g->d[0] & 1; + cond = (-delta >> (8 * sizeof(delta) - 1)) & g->d[0] & 1 + /* make sure g->top > 0 (i.e. if top == 0 then g == 0 always) */ + & (~((g->top - 1) >> (sizeof(g->top) * 8 - 1))); delta = (-cond & -delta) | ((cond - 1) & delta); r->neg ^= cond; /* swap */ @@ -603,7 +605,10 @@ int BN_gcd(BIGNUM *r, const BIGNUM *in_a, const BIGNUM *in_b, BN_CTX *ctx) delta++; if (!BN_add(temp, g, r)) goto err; - BN_consttime_swap(g->d[0] & 1, g, temp, top); + BN_consttime_swap(g->d[0] & 1 /* g is odd */ + /* make sure g->top > 0 (i.e. if top == 0 then g == 0 always) */ + & (~((g->top - 1) >> (sizeof(g->top) * 8 - 1))), + g, temp, top); if (!BN_rshift1(g, g)) goto err; } |