commit c4949d1426077bfaa870ea29401646549002d7ea
author Gilles Peskine <Gilles.Peskine@arm.com> Tue May 27 19:45:29 2025 +0200
committer Gilles Peskine <Gilles.Peskine@arm.com> Wed May 28 20:23:22 2025 +0200
tree f14e3638f5cac604be37c0615d534f4ae8c36372
parent 2744a439778cb748b05a0dd981f992f25d938cf4

mbedtls_ssl_conf_alpn_protocols: declare list elements as const

This reflects the fact that the library will not modify the list, and allows
the list to be read from a const buffer.

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 cb57a97..307da0f 100644
--- a/library/ssl_client.c
+++ b/library/ssl_client.c
@@ -141,7 +141,7 @@
      *     ProtocolName protocol_name_list<2..2^16-1>
      * } ProtocolNameList;
      */
-    for (const char **cur = ssl->conf->alpn_list; *cur != NULL; cur++) {
+    for (const char *const *cur = ssl->conf->alpn_list; *cur != NULL; cur++) {
         /*
          * mbedtls_ssl_conf_set_alpn_protocols() checked that the length of
          * protocol names is less than 255.

library/ssl_tls.c

diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index f95f3c7..1c0aab0 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -2534,10 +2534,11 @@
 #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */
 
 #if defined(MBEDTLS_SSL_ALPN)
-int mbedtls_ssl_conf_alpn_protocols(mbedtls_ssl_config *conf, const char **protos)
+int mbedtls_ssl_conf_alpn_protocols(mbedtls_ssl_config *conf,
+                                    const char *const *protos)
 {
     size_t cur_len, tot_len;
-    const char **p;
+    const char *const *p;
 
     /*
      * RFC 7301 3.1: "Empty strings MUST NOT be included and byte strings
@@ -5111,7 +5112,7 @@
 #if defined(MBEDTLS_SSL_ALPN)
     {
         uint8_t alpn_len;
-        const char **cur;
+        const char *const *cur;
 
         if ((size_t) (end - p) < 1) {
             return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
@@ -8547,7 +8548,7 @@
     }
 
     /* Use our order of preference */
-    for (const char **alpn = ssl->conf->alpn_list; *alpn != NULL; alpn++) {
+    for (const char *const *alpn = ssl->conf->alpn_list; *alpn != NULL; alpn++) {
         size_t const alpn_len = strlen(*alpn);
         p = protocol_name_list;
         while (p < protocol_name_list_end) {

library/ssl_tls12_client.c

diff --git a/library/ssl_tls12_client.c b/library/ssl_tls12_client.c
index df7dfbf..ec778f9 100644
--- a/library/ssl_tls12_client.c
+++ b/library/ssl_tls12_client.c
@@ -869,7 +869,7 @@
                               const unsigned char *buf, size_t len)
 {
     size_t list_len, name_len;
-    const char **p;
+    const char *const *p;
 
     /* If we didn't send it, the server shouldn't send it */
     if (ssl->conf->alpn_list == NULL) {

library/ssl_tls13_client.c

diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index 9386801..b7b075c 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -158,7 +158,7 @@
 
     /* Check that the server chosen protocol was in our list and save it */
     MBEDTLS_SSL_CHK_BUF_READ_PTR(p, protocol_name_list_end, protocol_name_len);
-    for (const char **alpn = ssl->conf->alpn_list; *alpn != NULL; alpn++) {
+    for (const char *const *alpn = ssl->conf->alpn_list; *alpn != NULL; alpn++) {
         if (protocol_name_len == strlen(*alpn) &&
             memcmp(p, *alpn, protocol_name_len) == 0) {
             ssl->alpn_chosen = *alpn;