diff options
| -rw-r--r-- | crypto/bn/bn_lib.c | 23 |
1 files changed, 11 insertions, 12 deletions
diff --git a/crypto/bn/bn_lib.c b/crypto/bn/bn_lib.c index a582ce5cf3..df6ea69535 100644 --- a/crypto/bn/bn_lib.c +++ b/crypto/bn/bn_lib.c @@ -417,28 +417,27 @@ BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret) /* ignore negative */ static int bn2binpad(const BIGNUM *a, unsigned char *to, int tolen) { - int i, j, top; + int n; + size_t i, inc, lasti, j; BN_ULONG l; - i = BN_num_bytes(a); + n = BN_num_bytes(a); if (tolen == -1) - tolen = i; - else if (tolen < i) + tolen = n; + else if (tolen < n) return -1; - if (i == 0) { + if (n == 0) { OPENSSL_cleanse(to, tolen); return tolen; } - top = a->top * BN_BYTES; - for (i = 0, j = tolen; j > 0; i++) { - unsigned int mask; - - mask = constant_time_lt(i, top); - i -= 1 & ~mask; /* stay on top limb */ + lasti = n - 1; + for (i = 0, inc = 1, j = tolen; j > 0;) { l = a->d[i / BN_BYTES]; - to[--j] = (unsigned char)(l >> (8 * (i % BN_BYTES)) & mask); + to[--j] = (unsigned char)(l >> (8 * (i % BN_BYTES)) & (0 - inc)); + inc = (i - lasti) >> (8 * sizeof(i) - 1); + i += inc; /* stay on top limb */ } return tolen; |