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Avoid an infinite loop in BN_GF2m_mod_inv 

If p is set to 1 when calling BN_GF2m_mod_inv then an infinite loop will
result. Calling this function set 1 when applications call this directly
is a non-sensical value - so this would be considered a bug in the caller.

It does not seem possible to cause OpenSSL internal callers of
BN_GF2m_mod_inv to call it with a value of 1.

So, for the above reasons, this is not considered a security issue.
Reported by Bing Shi.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Todd Short <todd.short@me.com>
(Merged from https://github.com/openssl/openssl/pull/22960)
This commit is contained in:
Matt Caswell 2023-12-06 11:09:53 +00:00
parent ff27959769
commit 9c1b8f17ce
1 changed files with 7 additions and 1 deletions
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8
crypto/bn/bn_gf2m.c
View File

@ -730,14 +730,20 @@ int BN_GF2m_mod_inv(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
{
BIGNUM *b = NULL;
int ret = 0;
int numbits;
BN_CTX_start(ctx);
if ((b = BN_CTX_get(ctx)) == NULL)
goto err;
/* Fail on a non-sensical input p value */
numbits = BN_num_bits(p);
if (numbits <= 1)
goto err;
/* generate blinding value */
do {
if (!BN_priv_rand_ex(b, BN_num_bits(p) - 1,
if (!BN_priv_rand_ex(b, numbits - 1,
BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY, 0, ctx))
goto err;
} while (BN_is_zero(b));