Add X.509 subject alternative name support to TLS certificate

verification.

This way one X.509 certificate can be used for hosts that
can be reached under multiple DNS names or for multiple hosts.

Signed-off-by: Maciej Szmigiero <mail@maciej.szmigiero.name>

ASTERISK-25063 #close

Change-Id: I13302c80490a0b44c43f1b45376c9bd7b15a538f

1 files changed, 53 insertions, 14 deletions

diff --git a/main/tcptls.c b/main/tcptls.c
index 0b06d22ac..652282b59 100644
--- a/main/tcptls.c
+++ b/main/tcptls.c
@@ -555,6 +555,34 @@ static void session_instance_destructor(void *obj)
 	ao2_cleanup(i->private_data);
 }
 
+#ifdef DO_SSL
+static int check_tcptls_cert_name(ASN1_STRING *cert_str, const char *hostname, const char *desc)
+{
+	unsigned char *str;
+	int ret;
+
+	ret = ASN1_STRING_to_UTF8(&str, cert_str);
+	if (ret < 0 || !str) {
+		return -1;
+	}
+
+	if (strlen((char *) str) != ret) {
+		ast_log(LOG_WARNING, "Invalid certificate %s length (contains NULL bytes?)\n", desc);
+
+		ret = -1;
+	} else if (!strcasecmp(hostname, (char *) str)) {
+		ret = 0;
+	} else {
+		ret = -1;
+	}
+
+	ast_debug(3, "SSL %s compare s1='%s' s2='%s'\n", desc, hostname, str);
+	OPENSSL_free(str);
+
+	return ret;
+}
+#endif
+
 /*! \brief
 * creates a FILE * from the fd passed by the accept thread.
 * This operation is potentially expensive (certificate verification),
@@ -631,8 +659,8 @@ static void *handle_tcptls_connection(void *data)
 				}
 				if (!ast_test_flag(&tcptls_session->parent->tls_cfg->flags, AST_SSL_IGNORE_COMMON_NAME)) {
 					ASN1_STRING *str;
-					unsigned char *str2;
 					X509_NAME *name = X509_get_subject_name(peer);
+					STACK_OF(GENERAL_NAME) *alt_names;
 					int pos = -1;
 					int found = 0;
 
@@ -643,25 +671,36 @@ static void *handle_tcptls_connection(void *data)
 						if (pos < 0) {
 							break;
 						}
+
 						str = X509_NAME_ENTRY_get_data(X509_NAME_get_entry(name, pos));
-						ret = ASN1_STRING_to_UTF8(&str2, str);
-						if (ret < 0) {
-							continue;
+						if (!check_tcptls_cert_name(str, tcptls_session->parent->hostname, "common name")) {
+							found = 1;
+							break;
 						}
+					}
+
+					if (!found) {
+						alt_names = X509_get_ext_d2i(peer, NID_subject_alt_name, NULL, NULL);
+						if (alt_names != NULL) {
+							int alt_names_count = sk_GENERAL_NAME_num(alt_names);
 
-						if (str2) {
-							if (strlen((char *) str2) != ret) {
-								ast_log(LOG_WARNING, "Invalid certificate common name length (contains NULL bytes?)\n");
-							} else if (!strcasecmp(tcptls_session->parent->hostname, (char *) str2)) {
-								found = 1;
+							for (pos = 0; pos < alt_names_count; pos++) {
+								const GENERAL_NAME *alt_name = sk_GENERAL_NAME_value(alt_names, pos);
+
+								if (alt_name->type != GEN_DNS) {
+									continue;
+								}
+
+								if (!check_tcptls_cert_name(alt_name->d.dNSName, tcptls_session->parent->hostname, "alt name")) {
+									found = 1;
+									break;
+								}
 							}
-							ast_debug(3, "SSL Common Name compare s1='%s' s2='%s'\n", tcptls_session->parent->hostname, str2);
-							OPENSSL_free(str2);
-						}
-						if (found) {
-							break;
+
+							sk_GENERAL_NAME_pop_free(alt_names, GENERAL_NAME_free);
 						}
 					}
+
 					if (!found) {
 						ast_log(LOG_ERROR, "Certificate common name did not match (%s)\n", tcptls_session->parent->hostname);
 						X509_free(peer);