Access ssl->hostname through abstractions in certificate verification
New abstractions to access ssl->hostname:
mbedtls_ssl_has_set_hostname_been_called(), mbedtls_ssl_free_hostname().
Use these abstractions to access the hostname with the opportunity for
extra checks in mbedtls_ssl_verify_certificate().
No behavior change except for a new log message.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 4744db3..dd1beb9 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -2516,6 +2516,36 @@
}
#if defined(MBEDTLS_X509_CRT_PARSE_C)
+
+#if defined(MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED)
+/** Whether mbedtls_ssl_set_hostname() has been called.
+ *
+ * \param[in] ssl SSL context
+ *
+ * \return \c 1 if mbedtls_ssl_set_hostname() has been called on \p ssl
+ * (including `mbedtls_ssl_set_hostname(ssl, NULL)`),
+ * otherwise \c 0.
+ */
+static int mbedtls_ssl_has_set_hostname_been_called(
+ const mbedtls_ssl_context *ssl)
+{
+ /* We can't tell the difference between the case where
+ * mbedtls_ssl_set_hostname() has not been called at all, and
+ * the case where it was last called with NULL. For the time
+ * being, we assume the latter, i.e. we behave as if there had
+ * been an implicit call to mbedtls_ssl_set_hostname(ssl, NULL). */
+ return ssl->hostname != NULL;
+}
+#endif
+
+static void mbedtls_ssl_free_hostname(mbedtls_ssl_context *ssl)
+{
+ if (ssl->hostname != NULL) {
+ mbedtls_zeroize_and_free(ssl->hostname, strlen(ssl->hostname));
+ }
+ ssl->hostname = NULL;
+}
+
int mbedtls_ssl_set_hostname(mbedtls_ssl_context *ssl, const char *hostname)
{
/* Initialize to suppress unnecessary compiler warning */
@@ -2533,10 +2563,7 @@
/* Now it's clear that we will overwrite the old hostname,
* so we can free it safely */
-
- if (ssl->hostname != NULL) {
- mbedtls_zeroize_and_free(ssl->hostname, strlen(ssl->hostname));
- }
+ mbedtls_ssl_free_hostname(ssl);
/* Passing NULL as hostname shall clear the old one */
@@ -5295,9 +5322,7 @@
}
#if defined(MBEDTLS_X509_CRT_PARSE_C)
- if (ssl->hostname != NULL) {
- mbedtls_zeroize_and_free(ssl->hostname, strlen(ssl->hostname));
- }
+ mbedtls_ssl_free_hostname(ssl);
#endif
#if defined(MBEDTLS_SSL_DTLS_HELLO_VERIFY) && defined(MBEDTLS_SSL_SRV_C)
@@ -8845,6 +8870,21 @@
return ret;
}
+static int get_hostname_for_verification(mbedtls_ssl_context *ssl,
+ const char **hostname)
+{
+ if (!mbedtls_ssl_has_set_hostname_been_called(ssl)) {
+ MBEDTLS_SSL_DEBUG_MSG(1, ("Certificate verification without having set hostname"));
+ }
+
+ *hostname = ssl->hostname;
+ if (*hostname == NULL) {
+ MBEDTLS_SSL_DEBUG_MSG(2, ("Certificate verification without CN verification"));
+ }
+
+ return 0;
+}
+
int mbedtls_ssl_verify_certificate(mbedtls_ssl_context *ssl,
int authmode,
mbedtls_x509_crt *chain,
@@ -8870,7 +8910,13 @@
p_vrfy = ssl->conf->p_vrfy;
}
- int ret = 0;
+ const char *hostname = "";
+ int ret = get_hostname_for_verification(ssl, &hostname);
+ if (ret != 0) {
+ MBEDTLS_SSL_DEBUG_RET(1, "get_hostname_for_verification", ret);
+ return ret;
+ }
+
int have_ca_chain_or_callback = 0;
#if defined(MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK)
if (ssl->conf->f_ca_cb != NULL) {
@@ -8883,7 +8929,7 @@
ssl->conf->f_ca_cb,
ssl->conf->p_ca_cb,
ssl->conf->cert_profile,
- ssl->hostname,
+ hostname,
&ssl->session_negotiate->verify_result,
f_vrfy, p_vrfy);
} else
@@ -8910,7 +8956,7 @@
chain,
ca_chain, ca_crl,
ssl->conf->cert_profile,
- ssl->hostname,
+ hostname,
&ssl->session_negotiate->verify_result,
f_vrfy, p_vrfy, rs_ctx);
}