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DH_check(): Do not try checking q properties if it is obviously invalid

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If  |q| >= |p| then the q value is obviously wrong as q
is supposed to be a prime divisor of p-1.

We check if p is overly large so this added test implies that
q is not large either when performing subsequent tests using that
q value.

Otherwise if it is too large these additional checks of the q value
such as the primality test can then trigger DoS by doing overly long
computations.

Fixes CVE-2023-3817

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
Reviewed-by: Todd Short <todd.short@me.com>
(Merged from https://github.com/openssl/openssl/pull/21550)
This commit is contained in:
Tomas Mraz 2023-07-25 15:22:48 +02:00 committed by Todd Short
parent 81d10e61a4
commit 1c16253f3c
1 changed files with 8 additions and 1 deletions
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9
crypto/dh/dh_check.c
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@ -143,7 +143,7 @@ int DH_check(const DH *dh, int *ret)
#ifdef FIPS_MODULE
return DH_check_params(dh, ret);
#else
int ok = 0, r;
int ok = 0, r, q_good = 0;
BN_CTX *ctx = NULL;
BIGNUM *t1 = NULL, *t2 = NULL;
int nid = DH_get_nid((DH *)dh);
@ -172,6 +172,13 @@ int DH_check(const DH *dh, int *ret)
goto err;
if (dh->params.q != NULL) {
if (BN_ucmp(dh->params.p, dh->params.q) > 0)
q_good = 1;
else
*ret |= DH_CHECK_INVALID_Q_VALUE;
}
if (q_good) {
if (BN_cmp(dh->params.g, BN_value_one()) <= 0)
*ret |= DH_NOT_SUITABLE_GENERATOR;
else if (BN_cmp(dh->params.g, dh->params.p) >= 0)