net/sock/dtls: allow to register multiple credentials into a sock

pkg/tinydtls/contrib/sock_dtls.c

@@ -293,8 +293,12 @@ int sock_dtls_create(sock_dtls_t *sock, sock_udp_t *udp_sock,
     sock->buf_ctx = NULL;
     memset(&sock->async_cb_session, 0, sizeof(sock->async_cb_session));
 #endif /* SOCK_HAS_ASYNC */
+
+    memset(sock->tags, CREDMAN_TAG_EMPTY, CONFIG_DTLS_CREDENTIALS_MAX * sizeof(credman_tag_t));
+    sock->tags_len = 1;
+    sock->tags[0] = tag;
+
     sock->role = role;
-    sock->tag = tag;
     sock->dtls_ctx = dtls_new_context(sock);
     if (!sock->dtls_ctx) {
         DEBUG("sock_dtls: error getting DTLS context\n");
@@ -316,6 +320,53 @@ int sock_dtls_set_server_psk_id_hint(sock_dtls_t *sock, const char *hint)
     return 0;
 }
 
+int sock_dtls_add_credential(sock_dtls_t *sock, credman_tag_t tag)
+{
+    assert(sock);
+    if (sock->tags_len < CONFIG_DTLS_CREDENTIALS_MAX) {
+        DEBUG("sock_dtls: credential added in position %d\n", sock->tags_len);
+        sock->tags[sock->tags_len] = tag;
+        sock->tags_len++;
+        return 0;
+    }
+    DEBUG("sock_dtls: could not add new credential\n");
+    return -1;
+}
+
+int sock_dtls_remove_credential(sock_dtls_t *sock, credman_tag_t tag)
+{
+    assert(sock);
+    int pos = -1;
+    for (unsigned i = 0; i < sock->tags_len; i++) {
+        if (sock->tags[i] == tag) {
+            pos = i;
+            DEBUG("sock_dtls: found credential to remove in position %i\n", pos);
+            break;
+        }
+    }
+
+    if (pos >= 0) {
+        sock->tags_len--;
+        for (; (unsigned)pos < sock->tags_len; pos++) {
+            sock->tags[pos] = sock->tags[pos + 1];
+        }
+        return 0;
+    }
+    else {
+        DEBUG("sock_dtls: could not find credential to remove\n");
+        return -1;
+    }
+}
+
+size_t sock_dtls_get_credentials(sock_dtls_t *sock, const credman_tag_t **out)
+{
+    assert(sock);
+    assert(out);
+
+    *out = sock->tags;
+    return sock->tags_len;
+}
+
 sock_udp_t *sock_dtls_get_udp_sock(sock_dtls_t *sock)
 {
     assert(sock);

pkg/tinydtls/include/sock_dtls_types.h

@@ -75,9 +75,9 @@ struct sock_dtls {
         size_t datalen;                     /**< data length */
         session_t *session;                 /**< Session information */
     } buffer;
-    credman_tag_t tag;                      /**< Credential tag of a registered
-                                                (D)TLS credential */
     char psk_hint[CONFIG_DTLS_PSK_ID_HINT_MAX_SIZE]; /**< PSK Identity hint */
+    credman_tag_t tags[CONFIG_DTLS_CREDENTIALS_MAX]; /**< Tags of the available credentials */
+    unsigned tags_len;                      /**< Number of tags in the list 'tags' */
     dtls_peer_type role;                    /**< DTLS role of the socket */
 };
 

sys/include/net/sock/dtls/creds.h

@@ -37,6 +37,13 @@ extern "C" {
 #ifndef CONFIG_DTLS_PSK_ID_HINT_MAX_SIZE
 #define CONFIG_DTLS_PSK_ID_HINT_MAX_SIZE    32
 #endif
+
+/**
+ * @brief   Default buffer size for TLS credential tags
+ */
+#ifndef CONFIG_DTLS_CREDENTIALS_MAX
+#define CONFIG_DTLS_CREDENTIALS_MAX     4
+#endif
 /** @} */
 
 /**
@@ -52,6 +59,42 @@ extern "C" {
  */
 int sock_dtls_set_server_psk_id_hint(sock_dtls_t *sock, const char *hint);
 
+/**
+ * @brief Adds a credential tag to list of available credentials for @p sock.
+ *
+ * @pre sock != NULL
+ *
+ * @param[in] sock      DTLS sock object
+ * @param[in] tag       Tag of the credential to add
+ *
+ * @retval 0 on success
+ * @retval -1 otherwise
+ */
+int sock_dtls_add_credential(sock_dtls_t *sock, credman_tag_t tag);
+
+/**
+ * @brief Removes a credential tag of the list of available credentials for @p sock.
+ *
+ * @pre sock != NULL
+ *
+ * @param[in] sock      DTLS sock object
+ * @param[in] tag       Tag of the credential to remove
+ *
+ * @retval 0 on success
+ * @retval -1 otherwise
+ */
+int sock_dtls_remove_credential(sock_dtls_t *sock, credman_tag_t tag);
+
+/**
+ * @brief Returns an array of tags of the registered credentials in @p sock.
+ *
+ * @param[in]  sock      DTLS sock object
+ * @param[out] out       Pointer to place the reference to a read-only array of @ref credman_tag_t
+ *
+ * @return Number of registered credentials
+ */
+size_t sock_dtls_get_credentials(sock_dtls_t *sock, const credman_tag_t **out);
+
 #ifdef __cplusplus
 }
 #endif

sys/net/sock/Kconfig

@@ -44,6 +44,10 @@ config DTLS_HANDSHAKE_BUFSIZE_EXP
         represents the exponent of 2^n, which will be used as the size of the
         buffer. The buffer is used to hold credentials during DTLS handshakes.
 
+config DTLS_CREDENTIALS_MAX
+    int "Buffer size for TLS credential tags"
+    default 4
+
 config DTLS_PSK_ID_HINT_MAX_SIZE
     int "Maximum size for a PSK Identity hint string"
     default 32