https_server: Add provision for callback at session close

Closes https://github.com/espressif/esp-idf/issues/8288

components/esp_https_server/include/esp_https_server.h

@@ -21,10 +21,21 @@ typedef enum {
     HTTPD_SSL_TRANSPORT_INSECURE     // SSL disabled
 } httpd_ssl_transport_mode_t;
 
+/**
+ * @brief Indicates the state at which the user callback is executed,
+ *        i.e at session creation or session close
+ */
+typedef enum {
+    HTTPD_SSL_USER_CB_SESS_CREATE,
+    HTTPD_SSL_USER_CB_SESS_CLOSE
+} httpd_ssl_user_cb_state_t;
+
 /**
  * @brief Callback data struct, contains the ESP-TLS connection handle
+ * and the connection state at which the callback is executed
  */
 typedef struct esp_https_server_user_cb_arg {
+    httpd_ssl_user_cb_state_t user_cb_state;
     const esp_tls_t *tls;
 } esp_https_server_user_cb_arg_t;
 

components/esp_https_server/src/https_server.c

@@ -18,6 +18,11 @@ typedef struct httpd_ssl_ctx {
     esp_https_server_user_cb *user_cb;
 } httpd_ssl_ctx_t;
 
+typedef struct httpd_ssl_transport_ctx {
+    esp_tls_t *tls;
+    httpd_ssl_ctx_t *global_ctx;
+} httpd_ssl_transport_ctx_t;
+
 /**
  * SSL socket close handler
  *
@@ -26,7 +31,20 @@ typedef struct httpd_ssl_ctx {
 static void httpd_ssl_close(void *ctx)
 {
     assert(ctx != NULL);
-    esp_tls_server_session_delete(ctx);
+
+    httpd_ssl_transport_ctx_t *transport_ctx = (httpd_ssl_transport_ctx_t *)ctx;
+    httpd_ssl_ctx_t *global_ctx = transport_ctx->global_ctx;
+    esp_tls_t *tls = transport_ctx->tls;
+
+    if (global_ctx->user_cb) {
+        esp_https_server_user_cb_arg_t user_cb_data = {0};
+        user_cb_data.user_cb_state = HTTPD_SSL_USER_CB_SESS_CLOSE;
+        user_cb_data.tls = tls;
+        (global_ctx->user_cb)((void *)&user_cb_data);
+    }
+
+    esp_tls_server_session_delete(tls);
+    free(ctx);
     ESP_LOGD(TAG, "Secure socket closed");
 }
 
@@ -39,7 +57,9 @@ static void httpd_ssl_close(void *ctx)
  */
 static int httpd_ssl_pending(httpd_handle_t server, int sockfd)
 {
-    esp_tls_t *tls = httpd_sess_get_transport_ctx(server, sockfd);
+    httpd_ssl_transport_ctx_t *transport_ctx = httpd_sess_get_transport_ctx(server, sockfd);
+    assert(transport_ctx != NULL);
+    esp_tls_t *tls = transport_ctx->tls;
     assert(tls != NULL);
     return esp_tls_get_bytes_avail(tls);
 }
@@ -56,7 +76,9 @@ static int httpd_ssl_pending(httpd_handle_t server, int sockfd)
  */
 static int httpd_ssl_recv(httpd_handle_t server, int sockfd, char *buf, size_t buf_len, int flags)
 {
-    esp_tls_t *tls = httpd_sess_get_transport_ctx(server, sockfd);
+    httpd_ssl_transport_ctx_t *transport_ctx = httpd_sess_get_transport_ctx(server, sockfd);
+    assert(transport_ctx != NULL);
+    esp_tls_t *tls = transport_ctx->tls;
     assert(tls != NULL);
     return esp_tls_conn_read(tls, buf, buf_len);
 }
@@ -73,7 +95,9 @@ static int httpd_ssl_recv(httpd_handle_t server, int sockfd, char *buf, size_t b
  */
 static int httpd_ssl_send(httpd_handle_t server, int sockfd, const char *buf, size_t buf_len, int flags)
 {
-    esp_tls_t *tls = httpd_sess_get_transport_ctx(server, sockfd);
+    httpd_ssl_transport_ctx_t *transport_ctx = httpd_sess_get_transport_ctx(server, sockfd);
+    assert(transport_ctx != NULL);
+    esp_tls_t *tls = transport_ctx->tls;
     assert(tls != NULL);
     return esp_tls_conn_write(tls, buf, buf_len);
 }
@@ -105,8 +129,18 @@ static esp_err_t httpd_ssl_open(httpd_handle_t server, int sockfd)
         goto fail;
     }
 
+    // Pass a new structure containing the global context and the tls pointer to httpd_ssl_close
+    // Store it in the context field of the HTTPD session object
+    // NOTE: allocated memory will be freed by httpd_ssl_close
+    httpd_ssl_transport_ctx_t *transport_ctx = (httpd_ssl_transport_ctx_t *)calloc(1, sizeof(httpd_ssl_transport_ctx_t));
+    if (!transport_ctx) {
+        return ESP_ERR_NO_MEM;
+    }
+    transport_ctx->tls = tls;
+    transport_ctx->global_ctx = global_ctx;
+
     // Store the SSL session into the context field of the HTTPD session object
-    httpd_sess_set_transport_ctx(server, sockfd, tls, httpd_ssl_close);
+    httpd_sess_set_transport_ctx(server, sockfd, transport_ctx, httpd_ssl_close);
 
     // Set rx/tx/pending override functions
     httpd_sess_set_send_override(server, sockfd, httpd_ssl_send);
@@ -114,7 +148,6 @@ static esp_err_t httpd_ssl_open(httpd_handle_t server, int sockfd)
     httpd_sess_set_pending_override(server, sockfd, httpd_ssl_pending);
 
     // all access should now go through SSL
-
     ESP_LOGD(TAG, "Secure socket open");
 
     if (global_ctx->open_fn) {
@@ -123,6 +156,7 @@ static esp_err_t httpd_ssl_open(httpd_handle_t server, int sockfd)
 
     if (global_ctx->user_cb) {
         esp_https_server_user_cb_arg_t user_cb_data = {0};
+        user_cb_data.user_cb_state = HTTPD_SSL_USER_CB_SESS_CREATE;
         user_cb_data.tls = tls;
         (global_ctx->user_cb)((void *)&user_cb_data);
     }

examples/protocols/https_server/simple/main/main.c

@@ -36,9 +36,32 @@ static esp_err_t root_get_handler(httpd_req_t *req)
 }
 
 #if CONFIG_EXAMPLE_ENABLE_HTTPS_USER_CALLBACK
+
+void print_peer_cert_info(const mbedtls_ssl_context *ssl)
+{
+    const mbedtls_x509_crt *cert;
+    const size_t buf_size = 1024;
+    char *buf = calloc(buf_size, sizeof(char));
+    if (buf == NULL) {
+        ESP_LOGE(TAG, "Out of memory - Callback execution failed!");
+        return;
+    }
+
+    // Logging the peer certificate info
+    cert = mbedtls_ssl_get_peer_cert(ssl);
+    if (cert != NULL) {
+        mbedtls_x509_crt_info((char *) buf, buf_size - 1, "    ", cert);
+        ESP_LOGI(TAG, "Peer certificate info:\n%s", buf);
+    } else {
+        ESP_LOGW(TAG, "Could not obtain the peer certificate!");
+    }
+
+    free(buf);
+}
+
 /**
  * Example callback function to get the certificate of connected clients,
- * whenever a new SSL connection is created
+ * whenever a new SSL connection is created and closed
  *
  * Can also be used to other information like Socket FD, Connection state, etc.
  *
@@ -51,30 +74,28 @@ static esp_err_t root_get_handler(httpd_req_t *req)
  */
 void https_server_user_callback(esp_https_server_user_cb_arg_t *user_cb)
 {
-    ESP_LOGI(TAG, "Session Created!");
+    ESP_LOGI(TAG, "User callback invoked!");
+
+    switch(user_cb->user_cb_state) {
+        case HTTPD_SSL_USER_CB_SESS_CREATE:
+            ESP_LOGD(TAG, "At session creation");
+
+            // Logging the socket FD
             ESP_LOGI(TAG, "Socket FD: %d", user_cb->tls->sockfd);
 
-    const mbedtls_x509_crt *cert;
+            // Logging the current ciphersuite
-    const size_t buf_size = 1024;
+            ESP_LOGI(TAG, "Current Ciphersuite: %s", mbedtls_ssl_get_ciphersuite(&user_cb->tls->ssl));
-    char *buf = calloc(buf_size, sizeof(char));
+            break;
-    if (buf == NULL) {
+        case HTTPD_SSL_USER_CB_SESS_CLOSE:
-        ESP_LOGE(TAG, "Out of memory - Callback execution failed!");
+            ESP_LOGD(TAG, "At session close");
+
+            // Logging the peer certificate
+            print_peer_cert_info(&user_cb->tls->ssl);
+            break;
+        default:
+            ESP_LOGE(TAG, "Illegal state!");
             return;
     }
-
-    mbedtls_x509_crt_info((char *) buf, buf_size - 1, "    ", &user_cb->tls->servercert);
-    ESP_LOGI(TAG, "Server certificate info:\n%s", buf);
-    memset(buf, 0x00, buf_size);
-
-    cert = mbedtls_ssl_get_peer_cert(&user_cb->tls->ssl);
-    if (cert != NULL) {
-        mbedtls_x509_crt_info((char *) buf, buf_size - 1, "    ", cert);
-        ESP_LOGI(TAG, "Peer certificate info:\n%s", buf);
-    } else {
-        ESP_LOGW(TAG, "Could not obtain the peer certificate!");
-    }
-
-    free(buf);
 }
 #endif