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From 9002fd07327a91f35ba6c1307e71fa6fd4409b7f Mon Sep 17 00:00:00 2001
From: Tomas Mraz <tomas@openssl.org>
Date: Tue, 25 Jul 2023 15:22:48 +0200
Subject: [PATCH] DH_check(): Do not try checking q properties if it is
obviously invalid
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)
(cherry picked from commit 1c16253f3c3a8d1e25918c3f404aae6a5b0893de)
(cherry picked from commit 6a1eb62c29db6cb5eec707f9338aee00f44e26f5)
---
crypto/dh/dh_check.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/crypto/dh/dh_check.c b/crypto/dh/dh_check.c
index aef6f9b1b7..fbe2797569 100644
--- a/crypto/dh/dh_check.c
+++ b/crypto/dh/dh_check.c
@@ -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)
--
2.27.0
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