From 8b24f94209676bbe9933affd2879a686b1ed044d Mon Sep 17 00:00:00 2001 From: David Benjamin Date: Fri, 21 Apr 2017 12:07:03 -0400 Subject: [PATCH] Numbers greater than 1 are usually non-negative. BN_is_prime_fasttest_ex begins by rejecting if a <= 1. Then it goes to set A := abs(a), but a cannot be negative at this point. Reviewed-by: Richard Levitte Reviewed-by: Rich Salz (Merged from https://github.com/openssl/openssl/pull/3275) --- crypto/bn/bn_prime.c | 24 ++++++------------------ 1 file changed, 6 insertions(+), 18 deletions(-) diff --git a/crypto/bn/bn_prime.c b/crypto/bn/bn_prime.c index 9295aeb625..9b12dd23b7 100644 --- a/crypto/bn/bn_prime.c +++ b/crypto/bn/bn_prime.c @@ -158,7 +158,6 @@ int BN_is_prime_fasttest_ex(const BIGNUM *a, int checks, BN_CTX *ctx_passed, BN_CTX *ctx = NULL; BIGNUM *A1, *A1_odd, *check; /* taken from ctx */ BN_MONT_CTX *mont = NULL; - const BIGNUM *A = NULL; if (BN_cmp(a, BN_value_one()) <= 0) return 0; @@ -188,25 +187,14 @@ int BN_is_prime_fasttest_ex(const BIGNUM *a, int checks, BN_CTX *ctx_passed, goto err; BN_CTX_start(ctx); - /* A := abs(a) */ - if (a->neg) { - BIGNUM *t; - if ((t = BN_CTX_get(ctx)) == NULL) - goto err; - if (BN_copy(t, a) == NULL) - goto err; - t->neg = 0; - A = t; - } else - A = a; A1 = BN_CTX_get(ctx); A1_odd = BN_CTX_get(ctx); check = BN_CTX_get(ctx); if (check == NULL) goto err; - /* compute A1 := A - 1 */ - if (!BN_copy(A1, A)) + /* compute A1 := a - 1 */ + if (!BN_copy(A1, a)) goto err; if (!BN_sub_word(A1, 1)) goto err; @@ -222,11 +210,11 @@ int BN_is_prime_fasttest_ex(const BIGNUM *a, int checks, BN_CTX *ctx_passed, if (!BN_rshift(A1_odd, A1, k)) goto err; - /* Montgomery setup for computations mod A */ + /* Montgomery setup for computations mod a */ mont = BN_MONT_CTX_new(); if (mont == NULL) goto err; - if (!BN_MONT_CTX_set(mont, A, ctx)) + if (!BN_MONT_CTX_set(mont, a, ctx)) goto err; for (i = 0; i < checks; i++) { @@ -234,9 +222,9 @@ int BN_is_prime_fasttest_ex(const BIGNUM *a, int checks, BN_CTX *ctx_passed, goto err; if (!BN_add_word(check, 1)) goto err; - /* now 1 <= check < A */ + /* now 1 <= check < a */ - j = witness(check, A, A1, A1_odd, k, ctx, mont); + j = witness(check, a, A1, A1_odd, k, ctx, mont); if (j == -1) goto err; if (j) { -- 2.25.1