commit e61852e4d2fabe9f37d38242050f26e8508ad8ec
author Gilles Peskine <Gilles.Peskine@arm.com> Wed Feb 12 23:28:48 2025 +0100
committer Gilles Peskine <Gilles.Peskine@arm.com> Thu Feb 13 21:24:01 2025 +0100
tree 98200752c65d81cb5329bfd9d98352272d682a63
parent b3de9da6b023404a8fb773f7f9276692dd791619

Access ssl->hostname through abstractions

New abstractions to access ssl->hostname:
mbedtls_ssl_has_set_hostname_been_called() (only implemented approximatively
for now), mbedtls_ssl_get_hostname_pointer(), mbedtls_ssl_free_hostname().

Only access ssl->hostname directly in these functions and in
mbedtls_ssl_set_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>

library/ssl_client.c

diff --git a/library/ssl_client.c b/library/ssl_client.c
index 345e608..0bd00cd 100644
--- a/library/ssl_client.c
+++ b/library/ssl_client.c
@@ -29,19 +29,20 @@
                                   size_t *olen)
 {
     unsigned char *p = buf;
+    const char *hostname = mbedtls_ssl_get_hostname_pointer(ssl);
     size_t hostname_len;
 
     *olen = 0;
 
-    if (ssl->hostname == NULL) {
+    if (hostname == NULL) {
         return 0;
     }
 
     MBEDTLS_SSL_DEBUG_MSG(3,
                           ("client hello, adding server name extension: %s",
-                           ssl->hostname));
+                           hostname));
 
-    hostname_len = strlen(ssl->hostname);
+    hostname_len = strlen(hostname);
 
     MBEDTLS_SSL_CHK_BUF_PTR(p, end, hostname_len + 9);
 
@@ -85,7 +86,7 @@
     MBEDTLS_PUT_UINT16_BE(hostname_len, p, 0);
     p += 2;
 
-    memcpy(p, ssl->hostname, hostname_len);
+    memcpy(p, hostname, hostname_len);
 
     *olen = hostname_len + 9;
 
@@ -881,13 +882,14 @@
 #if defined(MBEDTLS_SSL_PROTO_TLS1_3) && \
     defined(MBEDTLS_SSL_SESSION_TICKETS) && \
     defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
+    const char *context_hostname = mbedtls_ssl_get_hostname_pointer(ssl);
     if (ssl->tls_version == MBEDTLS_SSL_VERSION_TLS1_3  &&
         ssl->handshake->resume) {
-        int hostname_mismatch = ssl->hostname != NULL ||
+        int hostname_mismatch = context_hostname != NULL ||
                                 session_negotiate->hostname != NULL;
-        if (ssl->hostname != NULL && session_negotiate->hostname != NULL) {
+        if (context_hostname != NULL && session_negotiate->hostname != NULL) {
             hostname_mismatch = strcmp(
-                ssl->hostname, session_negotiate->hostname) != 0;
+                context_hostname, session_negotiate->hostname) != 0;
         }
 
         if (hostname_mismatch) {
@@ -898,7 +900,7 @@
         }
     } else {
         return mbedtls_ssl_session_set_hostname(session_negotiate,
-                                                ssl->hostname);
+                                                context_hostname);
     }
 #endif /* MBEDTLS_SSL_PROTO_TLS1_3 &&
           MBEDTLS_SSL_SESSION_TICKETS &&