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From:
Theo Buehler <tb@theobuehler.org>
Subject:
Re: isakmpd: don't reach into ASN1_STRING [step 2/2]
To:
tech@openbsd.org
Cc:
beck@openbsd.org
Date:
Fri, 5 Dec 2025 07:54:20 +0100

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On Tue, Nov 25, 2025 at 07:07:31AM +0100, Theo Buehler wrote:
> On Mon, Nov 24, 2025 at 03:31:58PM +0100, Theo Buehler wrote:
> > beck and davidben have plans to make ASN1_STRING opaque in OpenSSL 4 [1].
> > This breaks somewhere in the vicinity of 200 ports, so I don't think we'll
> > flip the switch anytime soon in libressl, but I want base to be ready for
> > that since that makes my life easier.
> 
> Here's the second step. This allows things that aren't really kosher in
> modern X.509 like omitting seconds or allowing local times.
> 
> Since this transforms notBefore and notAfter into a string to be used in
> a keynote assertion, existing libcrypto interfaces aren't suitable, so I
> kept this mechanical by assigning the data and length fields to local
> variables accessors and replacing tm->data by data and tm->length by
> len, only occasionally fixing up whitespace and omitting parentheses.
> 
> The whole dance should be deduplicated, but I'll leave that for someone
> else.

Anyone? It's a very simple diff... It's not my fault that it is so big :)

Index: x509.c
===================================================================
RCS file: /cvs/src/sbin/isakmpd/x509.c,v
diff -u -p -r1.127 x509.c
--- x509.c	25 Nov 2025 05:12:44 -0000	1.127
+++ x509.c	25 Nov 2025 05:43:37 -0000
@@ -116,7 +116,8 @@ x509_generate_kn(int id, X509 *cert)
 	time_t	tt;
 	char	before[15], after[15], *timecomp, *timecomp2;
 	ASN1_TIME *tm;
-	int	i;
+	const unsigned char *data;
+	int	i, len;
 
 	LOG_DBG((LOG_POLICY, 90,
 	    "x509_generate_kn: generating KeyNote policy for certificate %p",
@@ -220,8 +221,8 @@ x509_generate_kn(int id, X509 *cert)
 	key = NULL;
 
 	if (((tm = X509_get_notBefore(cert)) == NULL) ||
-	    (tm->type != V_ASN1_UTCTIME &&
-		tm->type != V_ASN1_GENERALIZEDTIME)) {
+	    (ASN1_STRING_type(tm) != V_ASN1_UTCTIME &&
+	     ASN1_STRING_type(tm) != V_ASN1_GENERALIZEDTIME)) {
 		struct tm *ltm;
 
 		tt = time(NULL);
@@ -233,16 +234,18 @@ x509_generate_kn(int id, X509 *cert)
 		strftime(before, 14, "%Y%m%d%H%M%S", ltm);
 		timecomp = "LocalTimeOfDay";
 	} else {
-		if (tm->data[tm->length - 1] == 'Z') {
+		data = ASN1_STRING_get0_data(tm);
+		len = ASN1_STRING_length(tm);
+		if (data[len - 1] == 'Z') {
 			timecomp = "GMTTimeOfDay";
-			i = tm->length - 2;
+			i = len - 2;
 		} else {
 			timecomp = "LocalTimeOfDay";
-			i = tm->length - 1;
+			i = len - 1;
 		}
 
 		for (; i >= 0; i--) {
-			if (tm->data[i] < '0' || tm->data[i] > '9') {
+			if (data[i] < '0' || data[i] > '9') {
 				LOG_DBG((LOG_POLICY, 30,
 				    "x509_generate_kn: invalid data in "
 				    "NotValidBefore time field"));
@@ -250,64 +253,64 @@ x509_generate_kn(int id, X509 *cert)
 			}
 		}
 
-		if (tm->type == V_ASN1_UTCTIME) {
-			if ((tm->length < 10) || (tm->length > 13)) {
+		if (ASN1_STRING_type(tm) == V_ASN1_UTCTIME) {
+			if (len < 10 || len > 13) {
 				LOG_DBG((LOG_POLICY, 30,
 				    "x509_generate_kn: invalid length "
 				    "of NotValidBefore time field (%d)",
-				    tm->length));
+				    len));
 				goto fail;
 			}
 			/* Validity checks.  */
-			if ((tm->data[2] != '0' && tm->data[2] != '1') ||
-			    (tm->data[2] == '0' && tm->data[3] == '0') ||
-			    (tm->data[2] == '1' && tm->data[3] > '2') ||
-			    (tm->data[4] > '3') ||
-			    (tm->data[4] == '0' && tm->data[5] == '0') ||
-			    (tm->data[4] == '3' && tm->data[5] > '1') ||
-			    (tm->data[6] > '2') ||
-			    (tm->data[6] == '2' && tm->data[7] > '3') ||
-			    (tm->data[8] > '5')) {
+			if ((data[2] != '0' && data[2] != '1') ||
+			    (data[2] == '0' && data[3] == '0') ||
+			    (data[2] == '1' && data[3] > '2') ||
+			    (data[4] > '3') ||
+			    (data[4] == '0' && data[5] == '0') ||
+			    (data[4] == '3' && data[5] > '1') ||
+			    (data[6] > '2') ||
+			    (data[6] == '2' && data[7] > '3') ||
+			    (data[8] > '5')) {
 				LOG_DBG((LOG_POLICY, 30,
 				    "x509_generate_kn: invalid value in "
 				    "NotValidBefore time field"));
 				goto fail;
 			}
 			/* Stupid UTC tricks.  */
-			if (tm->data[0] < '5')
+			if (data[0] < '5')
 				snprintf(before, sizeof before, "20%s",
-				    tm->data);
+				    data);
 			else
 				snprintf(before, sizeof before, "19%s",
-				    tm->data);
-		} else {	/* V_ASN1_GENERICTIME */
-			if ((tm->length < 12) || (tm->length > 15)) {
+				    data);
+		} else {	/* V_ASN1_GENERALIZEDTIME */
+			if (len < 12 || len > 15) {
 				LOG_DBG((LOG_POLICY, 30,
 				    "x509_generate_kn: invalid length of "
 				    "NotValidBefore time field (%d)",
-				    tm->length));
+				    len));
 				goto fail;
 			}
 			/* Validity checks.  */
-			if ((tm->data[4] != '0' && tm->data[4] != '1') ||
-			    (tm->data[4] == '0' && tm->data[5] == '0') ||
-			    (tm->data[4] == '1' && tm->data[5] > '2') ||
-			    (tm->data[6] > '3') ||
-			    (tm->data[6] == '0' && tm->data[7] == '0') ||
-			    (tm->data[6] == '3' && tm->data[7] > '1') ||
-			    (tm->data[8] > '2') ||
-			    (tm->data[8] == '2' && tm->data[9] > '3') ||
-			    (tm->data[10] > '5')) {
+			if ((data[4] != '0' && data[4] != '1') ||
+			    (data[4] == '0' && data[5] == '0') ||
+			    (data[4] == '1' && data[5] > '2') ||
+			    (data[6] > '3') ||
+			    (data[6] == '0' && data[7] == '0') ||
+			    (data[6] == '3' && data[7] > '1') ||
+			    (data[8] > '2') ||
+			    (data[8] == '2' && data[9] > '3') ||
+			    (data[10] > '5')) {
 				LOG_DBG((LOG_POLICY, 30,
 				    "x509_generate_kn: invalid value in "
 				    "NotValidBefore time field"));
 				goto fail;
 			}
-			snprintf(before, sizeof before, "%s", tm->data);
+			snprintf(before, sizeof before, "%s", data);
 		}
 
 		/* Fix missing seconds.  */
-		if (tm->length < 12) {
+		if (len < 12) {
 			before[12] = '0';
 			before[13] = '0';
 		}
@@ -317,8 +320,8 @@ x509_generate_kn(int id, X509 *cert)
 
 	tm = X509_get_notAfter(cert);
 	if (tm == NULL ||
-	    (tm->type != V_ASN1_UTCTIME &&
-		tm->type != V_ASN1_GENERALIZEDTIME)) {
+	    (ASN1_STRING_type(tm) != V_ASN1_UTCTIME &&
+	     ASN1_STRING_type(tm) != V_ASN1_GENERALIZEDTIME)) {
 		struct tm *ltm;
 
 		tt = time(0);
@@ -330,16 +333,18 @@ x509_generate_kn(int id, X509 *cert)
 		strftime(after, 14, "%Y%m%d%H%M%S", ltm);
 		timecomp2 = "LocalTimeOfDay";
 	} else {
-		if (tm->data[tm->length - 1] == 'Z') {
+		data = ASN1_STRING_get0_data(tm);
+		len = ASN1_STRING_length(tm);
+		if (data[len - 1] == 'Z') {
 			timecomp2 = "GMTTimeOfDay";
-			i = tm->length - 2;
+			i = len - 2;
 		} else {
 			timecomp2 = "LocalTimeOfDay";
-			i = tm->length - 1;
+			i = len - 1;
 		}
 
 		for (; i >= 0; i--) {
-			if (tm->data[i] < '0' || tm->data[i] > '9') {
+			if (data[i] < '0' || data[i] > '9') {
 				LOG_DBG((LOG_POLICY, 30,
 				    "x509_generate_kn: invalid data in "
 				    "NotValidAfter time field"));
@@ -347,64 +352,64 @@ x509_generate_kn(int id, X509 *cert)
 			}
 		}
 
-		if (tm->type == V_ASN1_UTCTIME) {
-			if ((tm->length < 10) || (tm->length > 13)) {
+		if (ASN1_STRING_type(tm) == V_ASN1_UTCTIME) {
+			if (len < 10 || len > 13) {
 				LOG_DBG((LOG_POLICY, 30,
 				    "x509_generate_kn: invalid length of "
 				    "NotValidAfter time field (%d)",
-				    tm->length));
+				    len));
 				goto fail;
 			}
 			/* Validity checks. */
-			if ((tm->data[2] != '0' && tm->data[2] != '1') ||
-			    (tm->data[2] == '0' && tm->data[3] == '0') ||
-			    (tm->data[2] == '1' && tm->data[3] > '2') ||
-			    (tm->data[4] > '3') ||
-			    (tm->data[4] == '0' && tm->data[5] == '0') ||
-			    (tm->data[4] == '3' && tm->data[5] > '1') ||
-			    (tm->data[6] > '2') ||
-			    (tm->data[6] == '2' && tm->data[7] > '3') ||
-			    (tm->data[8] > '5')) {
+			if ((data[2] != '0' && data[2] != '1') ||
+			    (data[2] == '0' && data[3] == '0') ||
+			    (data[2] == '1' && data[3] > '2') ||
+			    (data[4] > '3') ||
+			    (data[4] == '0' && data[5] == '0') ||
+			    (data[4] == '3' && data[5] > '1') ||
+			    (data[6] > '2') ||
+			    (data[6] == '2' && data[7] > '3') ||
+			    (data[8] > '5')) {
 				LOG_DBG((LOG_POLICY, 30,
 				    "x509_generate_kn: invalid value in "
 				    "NotValidAfter time field"));
 				goto fail;
 			}
 			/* Stupid UTC tricks.  */
-			if (tm->data[0] < '5')
+			if (data[0] < '5')
 				snprintf(after, sizeof after, "20%s",
-				    tm->data);
+				    data);
 			else
 				snprintf(after, sizeof after, "19%s",
-				    tm->data);
-		} else {	/* V_ASN1_GENERICTIME */
-			if ((tm->length < 12) || (tm->length > 15)) {
+				    data);
+		} else {	/* V_ASN1_GENERALIZEDTIME */
+			if (len < 12 || len > 15) {
 				LOG_DBG((LOG_POLICY, 30,
 				    "x509_generate_kn: invalid length of "
 				    "NotValidAfter time field (%d)",
-				    tm->length));
+				    len));
 				goto fail;
 			}
 			/* Validity checks.  */
-			if ((tm->data[4] != '0' && tm->data[4] != '1') ||
-			    (tm->data[4] == '0' && tm->data[5] == '0') ||
-			    (tm->data[4] == '1' && tm->data[5] > '2') ||
-			    (tm->data[6] > '3') ||
-			    (tm->data[6] == '0' && tm->data[7] == '0') ||
-			    (tm->data[6] == '3' && tm->data[7] > '1') ||
-			    (tm->data[8] > '2') ||
-			    (tm->data[8] == '2' && tm->data[9] > '3') ||
-			    (tm->data[10] > '5')) {
+			if ((data[4] != '0' && data[4] != '1') ||
+			    (data[4] == '0' && data[5] == '0') ||
+			    (data[4] == '1' && data[5] > '2') ||
+			    (data[6] > '3') ||
+			    (data[6] == '0' && data[7] == '0') ||
+			    (data[6] == '3' && data[7] > '1') ||
+			    (data[8] > '2') ||
+			    (data[8] == '2' && data[9] > '3') ||
+			    (data[10] > '5')) {
 				LOG_DBG((LOG_POLICY, 30,
 				    "x509_generate_kn: invalid value in "
 				    "NotValidAfter time field"));
 				goto fail;
 			}
-			snprintf(after, sizeof after, "%s", tm->data);
+			snprintf(after, sizeof after, "%s", data);
 		}
 
 		/* Fix missing seconds.  */
-		if (tm->length < 12) {
+		if (len < 12) {
 			after[12] = '0';
 			after[13] = '0';
 		}