From 91ddeba0f2269b017dc06c46c993a788974b1aa5 Mon Sep 17 00:00:00 2001 From: Tomas Mraz Date: Fri, 21 Jul 2023 11:39:41 +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: Paul Dale Reviewed-by: Matt Caswell (Merged from https://github.com/openssl/openssl/pull/21551) Upstream-Status: Backport [91ddeba0f2269b017dc06c46c993a788974b1aa5] --- crypto/dh/dh_check.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/crypto/dh/dh_check.c b/crypto/dh/dh_check.c index 2001d2e7cb..9ae96991eb 100644 --- a/crypto/dh/dh_check.c +++ b/crypto/dh/dh_check.c @@ -105,7 +105,7 @@ int DH_check_ex(const DH *dh) /* Note: according to documentation - this only checks the params */ int DH_check(const DH *dh, int *ret) { - int ok = 0, r; + int ok = 0, r, q_good = 0; BN_CTX *ctx = NULL; BIGNUM *t1 = NULL, *t2 = NULL; @@ -130,7 +130,14 @@ int DH_check(const DH *dh, int *ret) if (t2 == NULL) goto err; - if (dh->q) { + if (dh->q != NULL) { + if (BN_ucmp(dh->p, dh->q) > 0) + q_good = 1; + else + *ret |= DH_CHECK_INVALID_Q_VALUE; + } + + if (q_good) { if (BN_cmp(dh->g, BN_value_one()) <= 0) *ret |= DH_NOT_SUITABLE_GENERATOR; else if (BN_cmp(dh->g, dh->p) >= 0) -- 2.41.0