commit 15c95d6eb2e8bc549719578c9a16541015363360
Author: Hans Petter Jansson <hpj@hpjansson.org>
Date:   Mon Oct 26 22:26:46 2020 +0100

    Ensure DHGs are approved in FIPS mode using OpenSSL's DH_check_params()

diff --git a/dh.c b/dh.c
index 7cb135d..3fe7f75 100644
--- a/dh.c
+++ b/dh.c
@@ -143,6 +143,28 @@ parse_prime(int linenum, char *line, struct dhgroup *dhg)
 	return 0;
 }
 
+static int
+dhg_is_approved(const struct dhgroup *dhg)
+{
+	BIGNUM *g, *p;
+	DH *dh;
+	int dh_status;
+	int is_ok = 0;
+
+	/* DH_set0_pqg() transfers ownership of the bignums, so we
+	 * make temporary copies here for simplicity. */
+	g = BN_dup(dhg->g);
+	p = BN_dup(dhg->p);
+	dh = dh_new_group(g, p);
+
+	if (dh) {
+		is_ok = DH_check_params(dh, &dh_status);
+	}
+
+	DH_free(dh);
+	return is_ok;
+}
+
 DH *
 choose_dh(int min, int wantbits, int max)
 {
@@ -161,12 +183,20 @@ choose_dh(int min, int wantbits, int max)
 	linenum = 0;
 	best = bestcount = 0;
 	while (getline(&line, &linesize, f) != -1) {
+		int dhg_is_ok;
+
 		linenum++;
 		if (!parse_prime(linenum, line, &dhg))
 			continue;
+
+		dhg_is_ok = dhg_is_approved(&dhg);
+
 		BN_clear_free(dhg.g);
 		BN_clear_free(dhg.p);
 
+		if (!dhg_is_ok)
+			continue;
+
 		if (dhg.size > max || dhg.size < min)
 			continue;
 
@@ -193,10 +223,16 @@ choose_dh(int min, int wantbits, int max)
 	linenum = 0;
 	bestcount = 0;
 	while (getline(&line, &linesize, f) != -1) {
+		int dhg_is_ok;
+
 		linenum++;
 		if (!parse_prime(linenum, line, &dhg))
 			continue;
-		if ((dhg.size > max || dhg.size < min) ||
+
+		dhg_is_ok = dhg_is_approved(&dhg);
+
+		if (!dhg_is_ok ||
+		    (dhg.size > max || dhg.size < min) ||
 		    dhg.size != best ||
 		    bestcount++ != which) {
 			BN_clear_free(dhg.g);