Implement server session ticket support with mbedtls

Closes https://github.com/espressif/esp-idf/pull/7048

Signed-off-by: Aditya Patwardhan <aditya.patwardhan@espressif.com>

components/esp-tls/Kconfig

@@ -41,6 +41,20 @@ menu "ESP-TLS"
             Enable support for creating server side SSL/TLS session, available for mbedTLS
             as well as wolfSSL TLS library.
 
+    config ESP_TLS_SERVER_SESSION_TICKETS
+        bool "Enable session tickets"
+        depends on ESP_TLS_SERVER && ESP_TLS_USING_MBEDTLS && MBEDTLS_SERVER_SSL_SESSION_TICKETS
+        default n
+        help
+            Enable session ticket support as specified in RFC5077
+
+    config ESP_TLS_SERVER_SESSION_TICKET_TIMEOUT
+        int "Server session ticket timeout in seconds"
+        depends on ESP_TLS_SERVER_SESSION_TICKETS
+        default 86400
+        help
+            Sets the session ticket timeout used in the tls server.
+
     config ESP_TLS_PSK_VERIFICATION
         bool "Enable PSK verification"
         select MBEDTLS_PSK_MODES if ESP_TLS_USING_MBEDTLS

components/esp-tls/esp_tls.c

@@ -41,6 +41,8 @@ static const char *TAG = "esp-tls";
 #ifdef CONFIG_ESP_TLS_SERVER
 #define _esp_tls_server_session_create      esp_mbedtls_server_session_create
 #define _esp_tls_server_session_delete      esp_mbedtls_server_session_delete
+#define _esp_tls_session_ticket_ctx_init    esp_mbedtls_session_ticket_ctx_init
+#define _esp_tls_session_ticket_ctx_free    esp_mbedtls_session_ticket_ctx_free
 #endif  /* CONFIG_ESP_TLS_SERVER */
 #define _esp_tls_get_bytes_avail            esp_mbedtls_get_bytes_avail
 #define _esp_tls_init_global_ca_store       esp_mbedtls_init_global_ca_store
@@ -569,6 +571,32 @@ mbedtls_x509_crt *esp_tls_get_global_ca_store(void)
 
 #endif /* CONFIG_ESP_TLS_USING_MBEDTLS */
 #ifdef CONFIG_ESP_TLS_SERVER
+
+esp_err_t esp_tls_cfg_server_session_tickets_init(esp_tls_cfg_server_t *cfg)
+{
+#if defined(CONFIG_ESP_TLS_USING_MBEDTLS) && defined(CONFIG_ESP_TLS_SERVER_SESSION_TICKETS)
+    if (!cfg || cfg->ticket_ctx) {
+        return ESP_ERR_INVALID_ARG;
+    }
+    cfg->ticket_ctx = calloc(1, sizeof(esp_tls_session_ticket_ctx_t));
+    if (!cfg->ticket_ctx) {
+        return ESP_ERR_NO_MEM;
+    }
+    return _esp_tls_session_ticket_ctx_init(cfg->ticket_ctx);
+#else
+    return ESP_ERR_NOT_SUPPORTED;
+#endif
+}
+
+void esp_tls_cfg_server_session_tickets_free(esp_tls_cfg_server_t *cfg)
+{
+#if defined(CONFIG_ESP_TLS_USING_MBEDTLS) && defined(CONFIG_ESP_TLS_SERVER_SESSION_TICKETS)
+    if (cfg && cfg->ticket_ctx) {
+        _esp_tls_session_ticket_ctx_free(cfg->ticket_ctx);
+    }
+#endif
+}
+
 /**
  * @brief      Create a server side TLS/SSL connection
  */

components/esp-tls/esp_tls.h

@@ -20,6 +20,9 @@
 #include "mbedtls/ctr_drbg.h"
 #include "mbedtls/error.h"
 #include "mbedtls/certs.h"
+#ifdef CONFIG_ESP_TLS_SERVER_SESSION_TICKETS
+#include "mbedtls/ssl_ticket.h"
+#endif
 #elif CONFIG_ESP_TLS_USING_WOLFSSL
 #include "wolfssl/wolfcrypt/settings.h"
 #include "wolfssl/ssl.h"
@@ -171,6 +174,20 @@ typedef struct esp_tls_cfg {
 } esp_tls_cfg_t;
 
 #ifdef CONFIG_ESP_TLS_SERVER
+#if defined(CONFIG_ESP_TLS_USING_MBEDTLS) && defined(CONFIG_ESP_TLS_SERVER_SESSION_TICKETS)
+/**
+ * @brief Data structures necessary to support TLS session tickets according to RFC5077
+ */
+typedef struct esp_tls_session_ticket_ctx {
+    mbedtls_entropy_context entropy;                                            /*!< mbedTLS entropy context structure */
+
+    mbedtls_ctr_drbg_context ctr_drbg;                                          /*!< mbedTLS ctr drbg context structure.
+                                                                                     CTR_DRBG is deterministic random
+                                                                                     bit generation based on AES-256 */
+    mbedtls_ssl_ticket_context ticket_ctx;                                     /*!< Session ticket generation context */
+} esp_tls_session_ticket_ctx_t;
+#endif
+
 typedef struct esp_tls_cfg_server {
     const char **alpn_protos;                   /*!< Application protocols required for HTTP2.
                                                      If HTTP2/ALPN support is required, a list
@@ -222,7 +239,37 @@ typedef struct esp_tls_cfg_server {
     unsigned int serverkey_password_len;        /*!< String length of the password pointed to by
                                                      serverkey_password */
 
+#if defined(CONFIG_ESP_TLS_USING_MBEDTLS) && defined(CONFIG_ESP_TLS_SERVER_SESSION_TICKETS)
+    esp_tls_session_ticket_ctx_t * ticket_ctx; /*!< Session ticket generation context.
+                                                    You have to call esp_tls_cfg_server_session_tickets_init
+                                                    to use it.
+                                                    Call esp_tls_cfg_server_session_tickets_free
+                                                    to free the data associated with this context. */
+#endif
 } esp_tls_cfg_server_t;
+
+/**
+ * @brief Initialize the server side TLS session ticket context
+ *
+ * This function initializes the server side tls session ticket context
+ * which holds all necessary data structures to enable tls session tickets
+ * according to RFC5077.
+ * Use esp_tls_cfg_server_session_tickets_free to free the data.
+ *
+ * @param[in]  cfg server configuration as esp_tls_cfg_server_t
+ * @return
+ *             ESP_OK if setup succeeded
+ *             ESP_ERR_INVALID_ARG if context is already initialized
+ *             ESP_ERR_NO_MEM if memory allocation failed
+ *             ESP_ERR_NOT_SUPPORTED if session tickets are not available due to build configuration
+ *             ESP_FAIL if setup failed
+ */
+esp_err_t esp_tls_cfg_server_session_tickets_init(esp_tls_cfg_server_t *cfg);
+
+/**
+ * @brief Free the server side TLS session ticket context
+ */
+void esp_tls_cfg_server_session_tickets_free(esp_tls_cfg_server_t *cfg);
 #endif /* ! CONFIG_ESP_TLS_SERVER */
 
 /**

components/esp-tls/esp_tls_errors.h

@@ -31,18 +31,19 @@ extern "C" {
 #define ESP_ERR_MBEDTLS_PK_PARSE_KEY_FAILED               (ESP_ERR_ESP_TLS_BASE + 0x0F)  /*!< mbedtls api returned failed  */
 #define ESP_ERR_MBEDTLS_SSL_HANDSHAKE_FAILED              (ESP_ERR_ESP_TLS_BASE + 0x10)  /*!< mbedtls api returned failed  */
 #define ESP_ERR_MBEDTLS_SSL_CONF_PSK_FAILED               (ESP_ERR_ESP_TLS_BASE + 0x11)  /*!< mbedtls api returned failed  */
-#define ESP_ERR_ESP_TLS_CONNECTION_TIMEOUT                (ESP_ERR_ESP_TLS_BASE + 0x12)  /*!< new connection in esp_tls_low_level_conn connection timeouted */
+#define ESP_ERR_MBEDTLS_SSL_SESSION_TICKET_SETUP_FAILED   (ESP_ERR_ESP_TLS_BASE + 0x12)  /*!< mbedtls api returned failed  */
-#define ESP_ERR_WOLFSSL_SSL_SET_HOSTNAME_FAILED           (ESP_ERR_ESP_TLS_BASE + 0x13)  /*!< wolfSSL api returned error */
+#define ESP_ERR_ESP_TLS_CONNECTION_TIMEOUT                (ESP_ERR_ESP_TLS_BASE + 0x13)  /*!< new connection in esp_tls_low_level_conn connection timeouted */
-#define ESP_ERR_WOLFSSL_SSL_CONF_ALPN_PROTOCOLS_FAILED    (ESP_ERR_ESP_TLS_BASE + 0x14)  /*!< wolfSSL api returned error */
+#define ESP_ERR_WOLFSSL_SSL_SET_HOSTNAME_FAILED           (ESP_ERR_ESP_TLS_BASE + 0x14)  /*!< wolfSSL api returned error */
-#define ESP_ERR_WOLFSSL_CERT_VERIFY_SETUP_FAILED          (ESP_ERR_ESP_TLS_BASE + 0x15)  /*!< wolfSSL api returned error */
+#define ESP_ERR_WOLFSSL_SSL_CONF_ALPN_PROTOCOLS_FAILED    (ESP_ERR_ESP_TLS_BASE + 0x15)  /*!< wolfSSL api returned error */
-#define ESP_ERR_WOLFSSL_KEY_VERIFY_SETUP_FAILED           (ESP_ERR_ESP_TLS_BASE + 0x16)  /*!< wolfSSL api returned error */
+#define ESP_ERR_WOLFSSL_CERT_VERIFY_SETUP_FAILED          (ESP_ERR_ESP_TLS_BASE + 0x16)  /*!< wolfSSL api returned error */
-#define ESP_ERR_WOLFSSL_SSL_HANDSHAKE_FAILED              (ESP_ERR_ESP_TLS_BASE + 0x17)  /*!< wolfSSL api returned failed  */
+#define ESP_ERR_WOLFSSL_KEY_VERIFY_SETUP_FAILED           (ESP_ERR_ESP_TLS_BASE + 0x17)  /*!< wolfSSL api returned error */
-#define ESP_ERR_WOLFSSL_CTX_SETUP_FAILED                  (ESP_ERR_ESP_TLS_BASE + 0x18)  /*!< wolfSSL api returned failed */
+#define ESP_ERR_WOLFSSL_SSL_HANDSHAKE_FAILED              (ESP_ERR_ESP_TLS_BASE + 0x18)  /*!< wolfSSL api returned failed  */
-#define ESP_ERR_WOLFSSL_SSL_SETUP_FAILED                  (ESP_ERR_ESP_TLS_BASE + 0x19)  /*!< wolfSSL api returned failed */
+#define ESP_ERR_WOLFSSL_CTX_SETUP_FAILED                  (ESP_ERR_ESP_TLS_BASE + 0x19)  /*!< wolfSSL api returned failed */
-#define ESP_ERR_WOLFSSL_SSL_WRITE_FAILED                  (ESP_ERR_ESP_TLS_BASE + 0x1A)  /*!< wolfSSL api returned failed */
+#define ESP_ERR_WOLFSSL_SSL_SETUP_FAILED                  (ESP_ERR_ESP_TLS_BASE + 0x1A)  /*!< wolfSSL api returned failed */
+#define ESP_ERR_WOLFSSL_SSL_WRITE_FAILED                  (ESP_ERR_ESP_TLS_BASE + 0x1B)  /*!< wolfSSL api returned failed */
 
-#define ESP_ERR_ESP_TLS_SE_FAILED                         (ESP_ERR_ESP_TLS_BASE + 0x1B)  /*< esp-tls use Secure Element returned failed */
+#define ESP_ERR_ESP_TLS_SE_FAILED                         (ESP_ERR_ESP_TLS_BASE + 0x1C)  /*< esp-tls use Secure Element returned failed */
-#define ESP_ERR_ESP_TLS_TCP_CLOSED_FIN                    (ESP_ERR_ESP_TLS_BASE + 0x1C)  /*< esp-tls's TPC transport connection has benn closed (in a clean way) */
+#define ESP_ERR_ESP_TLS_TCP_CLOSED_FIN                    (ESP_ERR_ESP_TLS_BASE + 0x1D)  /*< esp-tls's TPC transport connection has benn closed (in a clean way) */
 
 /**
 * Definition of errors reported from IO API (potentially non-blocking) in case of error:

components/esp-tls/esp_tls_mbedtls.c

@@ -368,8 +368,70 @@ static esp_err_t set_global_ca_store(esp_tls_t *tls)
     return ESP_OK;
 }
 
-
 #ifdef CONFIG_ESP_TLS_SERVER
+#ifdef CONFIG_ESP_TLS_SERVER_SESSION_TICKETS
+int esp_mbedtls_session_ticket_write(void *p_ticket, const mbedtls_ssl_session *session, unsigned char *start, const unsigned char *end, size_t *tlen, uint32_t *lifetime)
+{
+    int ret = mbedtls_ssl_ticket_write(p_ticket, session, start, end, tlen, lifetime);
+#ifndef NDEBUG
+    if (ret != 0) {
+        ESP_LOGE(TAG, "Writing session ticket resulted in error code -0x%04X", -ret);
+        mbedtls_print_error_msg(ret);
+    }
+#endif
+    return ret;
+}
+
+int esp_mbedtls_session_ticket_parse(void *p_ticket, mbedtls_ssl_session *session, unsigned char *buf, size_t len)
+{
+    int ret = mbedtls_ssl_ticket_parse(p_ticket, session, buf, len);
+#ifndef NDEBUG
+    if (ret != 0) {
+        ESP_LOGD(TAG, "Parsing session ticket resulted in error code -0x%04X", -ret);
+        mbedtls_print_error_msg(ret);
+    }
+#endif
+    return ret;
+}
+
+esp_err_t esp_mbedtls_session_ticket_ctx_init(esp_tls_session_ticket_ctx_t *ctx)
+{
+    if (!ctx) {
+        return ESP_ERR_INVALID_ARG;
+    }
+    mbedtls_ctr_drbg_init(&ctx->ctr_drbg);
+    mbedtls_entropy_init(&ctx->entropy);
+    mbedtls_ssl_ticket_init(&ctx->ticket_ctx);
+    int ret;
+    if ((ret = mbedtls_ctr_drbg_seed(&ctx->ctr_drbg,
+                                     mbedtls_entropy_func, &ctx->entropy, NULL, 0)) != 0) {
+        ESP_LOGE(TAG, "mbedtls_ctr_drbg_seed returned -0x%04X", -ret);
+        mbedtls_print_error_msg(ret);
+        return ESP_ERR_MBEDTLS_CTR_DRBG_SEED_FAILED;
+    }
+
+    if( ( ret = mbedtls_ssl_ticket_setup( &ctx->ticket_ctx,
+                    mbedtls_ctr_drbg_random, &ctx->ctr_drbg,
+                    MBEDTLS_CIPHER_AES_256_GCM,
+                    CONFIG_ESP_TLS_SERVER_SESSION_TICKET_TIMEOUT ) ) != 0 )
+        {
+            ESP_LOGE(TAG, "mbedtls_ssl_ticket_setup returned -0x%04X", -ret);
+            mbedtls_print_error_msg(ret);
+            return ESP_ERR_MBEDTLS_SSL_SESSION_TICKET_SETUP_FAILED;
+        }
+    return ESP_OK;
+}
+
+void esp_mbedtls_session_ticket_ctx_free(esp_tls_session_ticket_ctx_t *ctx)
+{
+    if (ctx) {
+        mbedtls_ssl_ticket_free(&ctx->ticket_ctx);
+        mbedtls_ctr_drbg_init(&ctx->ctr_drbg);
+        mbedtls_entropy_free(&ctx->entropy);
+    }
+}
+#endif
+
 esp_err_t set_server_config(esp_tls_cfg_server_t *cfg, esp_tls_t *tls)
 {
     assert(cfg != NULL);
@@ -421,6 +483,18 @@ esp_err_t set_server_config(esp_tls_cfg_server_t *cfg, esp_tls_t *tls)
         ESP_LOGE(TAG, "Missing server certificate and/or key");
         return ESP_ERR_INVALID_STATE;
     }
+
+#ifdef CONFIG_ESP_TLS_SERVER_SESSION_TICKETS
+    if (cfg->ticket_ctx) {
+        ESP_LOGD(TAG, "Enabling server-side tls session ticket support");
+
+        mbedtls_ssl_conf_session_tickets_cb( &tls->conf,
+                esp_mbedtls_session_ticket_write,
+                esp_mbedtls_session_ticket_parse,
+                &cfg->ticket_ctx->ticket_ctx );
+    }
+#endif
+
     return ESP_OK;
 }
 #endif /* ! CONFIG_ESP_TLS_SERVER */

components/esp-tls/private_include/esp_tls_mbedtls.h

@@ -76,6 +76,22 @@ int esp_mbedtls_server_session_create(esp_tls_cfg_server_t *cfg, int sockfd, esp
  * /note :- The function can only be used with mbedtls ssl library
  */
 void esp_mbedtls_server_session_delete(esp_tls_t *tls);
+
+#ifdef CONFIG_ESP_TLS_SERVER_SESSION_TICKETS
+/**
+ * Internal function to setup server side session ticket context
+ *
+ * /note :- The function can only be used with mbedtls ssl library
+ */
+esp_err_t esp_mbedtls_session_ticket_ctx_init(esp_tls_session_ticket_ctx_t *cfg);
+
+/**
+ * Internal function to free server side session ticket context
+ *
+ * /note :- The function can only be used with mbedtls ssl library
+ */
+void esp_mbedtls_session_ticket_ctx_free(esp_tls_session_ticket_ctx_t *cfg);
+#endif
 #endif
 
 /**

components/esp_https_server/include/esp_https_server.h

@@ -63,6 +63,9 @@ struct httpd_ssl_config {
 
     /** Port used when transport mode is insecure (default 80) */
     uint16_t port_insecure;
+
+    /** Enable tls session tickets */
+    bool session_tickets;
 };
 
 typedef struct httpd_ssl_config httpd_ssl_config_t;
@@ -109,6 +112,7 @@ typedef struct httpd_ssl_config httpd_ssl_config_t;
     .transport_mode = HTTPD_SSL_TRANSPORT_SECURE, \
     .port_secure = 443,                           \
     .port_insecure = 80,                          \
+    .session_tickets = false,                     \
 }
 
 /**

components/esp_https_server/src/https_server.c

@@ -145,6 +145,7 @@ static void free_secure_context(void *ctx)
     if (cfg->serverkey_buf) {
         free((void *)cfg->serverkey_buf);
     }
+    esp_tls_cfg_server_session_tickets_free(cfg);
     free(cfg);
     free(ssl_ctx);
 }
@@ -160,6 +161,16 @@ static httpd_ssl_ctx_t *create_secure_context(const struct httpd_ssl_config *con
         free(ssl_ctx);
         return NULL;
     }
+
+    if (config->session_tickets) {
+        if ( esp_tls_cfg_server_session_tickets_init(cfg) != ESP_OK ) {
+            ESP_LOGE(TAG, "Failed to init session ticket support");
+            free(ssl_ctx);
+            free(cfg);
+            return NULL;
+        }
+    }
+
     ssl_ctx->tls_cfg = cfg;
 /* cacert = CA which signs client cert, or client cert itself , which is mapped to client_verify_cert_pem */
     if(config->client_verify_cert_pem != NULL) {