From 1c16253f3c3a8d1e25918c3f404aae6a5b0893de Mon Sep 17 00:00:00 2001 From: Tomas Mraz Date: Tue, 25 Jul 2023 15:22:48 +0200 Subject: 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 Reviewed-by: Paul Dale Reviewed-by: Tom Cosgrove Reviewed-by: Todd Short (Merged from https://github.com/openssl/openssl/pull/21550) --- crypto/dh/dh_check.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'crypto') diff --git a/crypto/dh/dh_check.c b/crypto/dh/dh_check.c index 6e1ea5349a..58c1d1798b 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) -- cgit v1.2.3