From df6b67becc1f41c2eeee7e20ff10b5ec42ced58b Mon Sep 17 00:00:00 2001 From: Andy Polyakov Date: Mon, 16 Jul 2018 18:17:44 +0200 Subject: [PATCH] bn/bn_lib.c address Coverity nit in bn2binpad. It was false positive, but one can as well view it as readability issue. Switch even to unsigned indices because % BN_BYTES takes 4-6 instructions with signed dividend vs. 1 (one) with unsigned. Reviewed-by: Rich Salz (Merged from https://github.com/openssl/openssl/pull/6889) (cherry picked from commit 83e034379fa3f6f0d308ec75fbcb137e26154aec) --- crypto/bn/bn_lib.c | 23 +++++++++++------------ 1 file changed, 11 insertions(+), 12 deletions(-) diff --git a/crypto/bn/bn_lib.c b/crypto/bn/bn_lib.c index 4ed037d176..03bd8cd183 100644 --- a/crypto/bn/bn_lib.c +++ b/crypto/bn/bn_lib.c @@ -616,28 +616,27 @@ 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; -- 2.25.1