Merge pull request #87 from andresag01/iotssl-1247-tls-client-refactoring

Refactor tls-client example to improve readability

Author: Patater

tests/tls-client.log

@@ -1,6 +1,13 @@
-Starting the TLS handshake...
-Server certificate:
-Certificate verification passed
-HTTPS: Received 'Hello world!' status ... [OK]
-HTTPS: Received message:
-Hello world!
+Starting mbed-os-example-tls/tls-client
+Using Mbed OS
+Successfully connected to os.mbed.com at port 443
+Starting the TLS handshake...
+Successfully completed the TLS handshake
+Server certificate:
+Certificate verification passed
+Established TLS connection to os.mbed.com
+HTTP: Received [0-9]+ chars from server
+HTTP: Received '200 OK' status ... OK
+HTTP: Received message:
+Hello world!
+DONE

tls-client/HelloHttpsClient.cpp

@@ -0,0 +1,374 @@
+/*
+ *  Hello world example of a TLS client: fetch an HTTPS page
+ *
+ *  Copyright (C) 2006-2018, Arm Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  This file is part of Mbed TLS (https://tls.mbed.org)
+ */
+
+#include "HelloHttpsClient.h"
+
+#include "easy-connect.h"
+
+#include "mbedtls/platform.h"
+#include "mbedtls/config.h"
+#include "mbedtls/ssl.h"
+#include "mbedtls/entropy.h"
+#include "mbedtls/ctr_drbg.h"
+#include "mbedtls/error.h"
+#include "mbedtls/debug.h"
+
+#include <stdint.h>
+#include <string.h>
+
+const char *HelloHttpsClient::DRBG_PERSONALIZED_STR =
+                                                "Mbed TLS helloword client";
+
+const size_t HelloHttpsClient::ERROR_LOG_BUFFER_LENGTH = 128;
+
+const char *HelloHttpsClient::TLS_PEM_CA =
+    "-----BEGIN CERTIFICATE-----\n"
+    "MIIDdTCCAl2gAwIBAgILBAAAAAABFUtaw5QwDQYJKoZIhvcNAQEFBQAwVzELMAkG\n"
+    "A1UEBhMCQkUxGTAXBgNVBAoTEEdsb2JhbFNpZ24gbnYtc2ExEDAOBgNVBAsTB1Jv\n"
+    "b3QgQ0ExGzAZBgNVBAMTEkdsb2JhbFNpZ24gUm9vdCBDQTAeFw05ODA5MDExMjAw\n"
+    "MDBaFw0yODAxMjgxMjAwMDBaMFcxCzAJBgNVBAYTAkJFMRkwFwYDVQQKExBHbG9i\n"
+    "YWxTaWduIG52LXNhMRAwDgYDVQQLEwdSb290IENBMRswGQYDVQQDExJHbG9iYWxT\n"
+    "aWduIFJvb3QgQ0EwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDaDuaZ\n"
+    "jc6j40+Kfvvxi4Mla+pIH/EqsLmVEQS98GPR4mdmzxzdzxtIK+6NiY6arymAZavp\n"
+    "xy0Sy6scTHAHoT0KMM0VjU/43dSMUBUc71DuxC73/OlS8pF94G3VNTCOXkNz8kHp\n"
+    "1Wrjsok6Vjk4bwY8iGlbKk3Fp1S4bInMm/k8yuX9ifUSPJJ4ltbcdG6TRGHRjcdG\n"
+    "snUOhugZitVtbNV4FpWi6cgKOOvyJBNPc1STE4U6G7weNLWLBYy5d4ux2x8gkasJ\n"
+    "U26Qzns3dLlwR5EiUWMWea6xrkEmCMgZK9FGqkjWZCrXgzT/LCrBbBlDSgeF59N8\n"
+    "9iFo7+ryUp9/k5DPAgMBAAGjQjBAMA4GA1UdDwEB/wQEAwIBBjAPBgNVHRMBAf8E\n"
+    "BTADAQH/MB0GA1UdDgQWBBRge2YaRQ2XyolQL30EzTSo//z9SzANBgkqhkiG9w0B\n"
+    "AQUFAAOCAQEA1nPnfE920I2/7LqivjTFKDK1fPxsnCwrvQmeU79rXqoRSLblCKOz\n"
+    "yj1hTdNGCbM+w6DjY1Ub8rrvrTnhQ7k4o+YviiY776BQVvnGCv04zcQLcFGUl5gE\n"
+    "38NflNUVyRRBnMRddWQVDf9VMOyGj/8N7yy5Y0b2qvzfvGn9LhJIZJrglfCm7ymP\n"
+    "AbEVtQwdpf5pLGkkeB6zpxxxYu7KyJesF12KwvhHhm4qxFYxldBniYUr+WymXUad\n"
+    "DKqC5JlR3XC321Y9YeRq4VzW9v493kHMB65jUr9TU/Qr6cf9tveCX4XSQRjbgbME\n"
+    "HMUfpIBvFSDJ3gyICh3WZlXi/EjJKSZp4A==\n"
+    "-----END CERTIFICATE-----\n";
+
+const char *HelloHttpsClient::HTTP_REQUEST_FILE_PATH =
+                                    "/media/uploads/mbed_official/hello.txt";
+
+const char *HelloHttpsClient::HTTP_HELLO_STR = "Hello world!";
+
+const char *HelloHttpsClient::HTTP_OK_STR = "200 OK";
+
+HelloHttpsClient::HelloHttpsClient(const char *in_server_name,
+                                   const uint16_t in_server_port) :
+    socket(),
+    server_name(in_server_name),
+    server_port(in_server_port)
+{
+    mbedtls_entropy_init(&entropy);
+    mbedtls_ctr_drbg_init(&ctr_drbg);
+    mbedtls_x509_crt_init(&cacert);
+    mbedtls_ssl_init(&ssl);
+    mbedtls_ssl_config_init(&ssl_conf);
+}
+
+HelloHttpsClient::~HelloHttpsClient()
+{
+    mbedtls_entropy_free(&entropy);
+    mbedtls_ctr_drbg_free(&ctr_drbg);
+    mbedtls_x509_crt_free(&cacert);
+    mbedtls_ssl_free(&ssl);
+    mbedtls_ssl_config_free(&ssl_conf);
+
+    socket.close();
+}
+
+int HelloHttpsClient::run()
+{
+    int ret;
+    size_t req_len, req_offset, resp_offset;
+    uint32_t flags;
+    bool resp_200, resp_hello;
+
+    /* Configure the TCPSocket */
+    if ((ret = configureTCPSocket()) != 0)
+        return ret;
+
+    /* Configure already initialized Mbed TLS structures */
+    if ((ret = configureTlsContexts()) != 0)
+        return ret;
+
+    /* Start a connection to the server */
+    if ((ret = socket.connect(server_name, server_port)) != NSAPI_ERROR_OK) {
+        mbedtls_printf("socket.connect() returned %d\n", ret);
+        return ret;
+    }
+    mbedtls_printf("Successfully connected to %s at port %u\n",
+                   server_name, server_port);
+
+    /* Start the TLS handshake */
+    mbedtls_printf("Starting the TLS handshake...\n");
+    do {
+        ret = mbedtls_ssl_handshake(&ssl);
+    } while(ret != 0 &&
+            (ret == MBEDTLS_ERR_SSL_WANT_READ ||
+            ret == MBEDTLS_ERR_SSL_WANT_WRITE));
+    if (ret < 0) {
+        mbedtls_printf("mbedtls_ssl_handshake() returned -0x%04X\n", -ret);
+        return ret;
+    }
+    mbedtls_printf("Successfully completed the TLS handshake\n");
+
+    /* Fill the request buffer */
+    ret = snprintf(gp_buf, sizeof(gp_buf),
+                   "GET %s HTTP/1.1\nHost: %s\n\n", HTTP_REQUEST_FILE_PATH,
+                   server_name);
+    req_len = static_cast<size_t>(ret);
+    if (ret < 0 || req_len >= sizeof(gp_buf)) {
+        mbedtls_printf("Failed to compose HTTP request using snprintf: %d\n",
+                       ret);
+        return ret;
+    }
+
+    /* Send the HTTP request to the server over TLS */
+    req_offset = 0;
+    do {
+        ret = mbedtls_ssl_write(&ssl,
+                reinterpret_cast<const unsigned char *>(gp_buf + req_offset),
+                req_len - req_offset);
+        if (ret > 0)
+            req_offset += static_cast<size_t>(ret);
+    }
+    while(req_offset < req_len &&
+          (ret > 0 ||
+          ret == MBEDTLS_ERR_SSL_WANT_WRITE ||
+          ret == MBEDTLS_ERR_SSL_WANT_READ));
+    if (ret < 0) {
+        mbedtls_printf("mbedtls_ssl_write() returned -0x%04X\n", -ret);
+        return ret;
+    }
+
+    /* Print information about the TLS connection */
+    ret = mbedtls_x509_crt_info(gp_buf, sizeof(gp_buf),
+                                "\r  ", mbedtls_ssl_get_peer_cert(&ssl));
+    if (ret < 0) {
+        mbedtls_printf("mbedtls_x509_crt_info() returned -0x%04X\n", -ret);
+        return ret;
+    }
+    mbedtls_printf("Server certificate:\n%s\n", gp_buf);
+
+    /* Ensure certificate verification was successful */
+    flags = mbedtls_ssl_get_verify_result(&ssl);
+    if (flags != 0) {
+        ret = mbedtls_x509_crt_verify_info(gp_buf, sizeof(gp_buf),
+                                           "\r  ! ", flags);
+        if (ret < 0) {
+            mbedtls_printf("mbedtls_x509_crt_verify_info() returned "
+                           "-0x%04X\n", -ret);
+            return ret;
+        } else {
+            mbedtls_printf("Certificate verification failed (flags %lu):"
+                           "\n%s\n", flags, gp_buf);
+            return -1;
+        }
+    } else {
+        mbedtls_printf("Certificate verification passed\n");
+    }
+
+    mbedtls_printf("Established TLS connection to %s\n", server_name);
+
+    /* Read response from the server */
+    resp_offset = 0;
+    resp_200 = false;
+    resp_hello = false;
+    do {
+        ret = mbedtls_ssl_read(&ssl,
+                    reinterpret_cast<unsigned char *>(gp_buf  + resp_offset),
+                    sizeof(gp_buf) - resp_offset - 1);
+        if (ret > 0)
+            resp_offset += static_cast<size_t>(ret);
+
+        /* Ensure that the response string is null-terminated */
+        gp_buf[resp_offset] = '\0';
+
+        /* Check  if we received expected string */
+        resp_200 = resp_200 || strstr(gp_buf, HTTP_OK_STR) != NULL;
+        resp_hello = resp_hello || strstr(gp_buf, HTTP_HELLO_STR) != NULL;
+    } while((!resp_200 || !resp_hello) &&
+            (ret > 0 ||
+            ret == MBEDTLS_ERR_SSL_WANT_READ || MBEDTLS_ERR_SSL_WANT_WRITE));
+    if (ret < 0) {
+        mbedtls_printf("mbedtls_ssl_read() returned -0x%04X\n", -ret);
+        return ret;
+    }
+
+    /* Display response information */
+    mbedtls_printf("HTTP: Received %u chars from server\n", resp_offset);
+    mbedtls_printf("HTTP: Received '%s' status ... %s\n", HTTP_OK_STR,
+                   resp_200 ? "OK" : "FAIL");
+    mbedtls_printf("HTTP: Received message:\n%s\n", gp_buf);
+
+    return 0;
+}
+
+int HelloHttpsClient::configureTCPSocket()
+{
+    int ret;
+
+    /*
+     * Use easy-connect lib to support multiple network bearers. See
+     * https://github.com/ARMmbed/easy-connect README.md for more information.
+     */
+#if HELLO_HTTPS_CLIENT_DEBUG_LEVEL > 0
+    NetworkInterface *network = easy_connect(true);
+#else
+    NetworkInterface *network = easy_connect(false);
+#endif /* HELLO_HTTPS_CLIENT_DEBUG_LEVEL > 0 */
+    if(network == NULL) {
+        mbedtls_printf("easy_connect() returned NULL\n"
+                       "Failed to connect to the network\n");
+        return -1;
+    }
+
+    if ((ret = socket.open(network)) != NSAPI_ERROR_OK) {
+        mbedtls_printf("socket.open() returned %d\n", ret);
+        return ret;
+    }
+
+    socket.set_blocking(false);
+
+    return 0;
+}
+
+int HelloHttpsClient::configureTlsContexts()
+{
+    int ret;
+
+    ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
+            reinterpret_cast<const unsigned char *>(DRBG_PERSONALIZED_STR),
+            strlen(DRBG_PERSONALIZED_STR) + 1);
+    if (ret != 0) {
+        mbedtls_printf("mbedtls_ctr_drbg_seed() returned -0x%04X\n", -ret);
+        return ret;
+    }
+
+    ret = mbedtls_x509_crt_parse(&cacert,
+                        reinterpret_cast<const unsigned char *>(TLS_PEM_CA),
+                        strlen(TLS_PEM_CA) + 1);
+    if (ret != 0) {
+        mbedtls_printf("mbedtls_x509_crt_parse() returned -0x%04X\n", -ret);
+        return ret;
+    }
+
+    ret = mbedtls_ssl_config_defaults(&ssl_conf, MBEDTLS_SSL_IS_CLIENT,
+                                      MBEDTLS_SSL_TRANSPORT_STREAM,
+                                      MBEDTLS_SSL_PRESET_DEFAULT);
+    if (ret != 0) {
+        mbedtls_printf("mbedtls_ssl_config_defaults() returned -0x%04X\n",
+                       -ret);
+        return ret;
+    }
+
+    mbedtls_ssl_conf_ca_chain(&ssl_conf, &cacert, NULL);
+    mbedtls_ssl_conf_rng(&ssl_conf, mbedtls_ctr_drbg_random, &ctr_drbg);
+
+    /*
+     * It is possible to disable authentication by passing
+     * MBEDTLS_SSL_VERIFY_NONE in the call to mbedtls_ssl_conf_authmode()
+     */
+    mbedtls_ssl_conf_authmode(&ssl_conf, MBEDTLS_SSL_VERIFY_REQUIRED);
+
+#if HELLO_HTTPS_CLIENT_DEBUG_LEVEL > 0
+    mbedtls_ssl_conf_verify(&ssl_conf, sslVerify, this);
+    mbedtls_ssl_conf_dbg(&ssl_conf, sslDebug, NULL);
+    mbedtls_debug_set_threshold(HELLO_HTTPS_CLIENT_DEBUG_LEVEL);
+#endif /* HELLO_HTTPS_CLIENT_DEBUG_LEVEL > 0 */
+
+    if ((ret = mbedtls_ssl_setup( &ssl, &ssl_conf)) != 0) {
+        mbedtls_printf("mbedtls_ssl_setup() returned -0x%04X\n", -ret);
+        return ret;
+    }
+
+    if ((ret = mbedtls_ssl_set_hostname( &ssl, server_name )) != 0) {
+        mbedtls_printf("mbedtls_ssl_set_hostname() returned -0x%04X\n",
+                       -ret);
+        return ret;
+    }
+
+    mbedtls_ssl_set_bio(&ssl, static_cast<void *>(&socket), sslSend, sslRecv,
+                        NULL);
+
+    return 0;
+}
+
+int HelloHttpsClient::sslRecv(void *ctx, unsigned char *buf, size_t len)
+{
+    TCPSocket *socket = static_cast<TCPSocket *>(ctx);
+    int ret = socket->recv(buf, len);
+
+    if (ret == NSAPI_ERROR_WOULD_BLOCK)
+        ret = MBEDTLS_ERR_SSL_WANT_READ;
+    else if (ret < 0)
+        mbedtls_printf("socket.recv() returned %d\n", ret);
+
+    return ret;
+}
+
+int HelloHttpsClient::sslSend(void *ctx, const unsigned char *buf, size_t len)
+{
+    TCPSocket *socket = static_cast<TCPSocket *>(ctx);
+    int ret = socket->send(buf, len);
+
+    if (ret == NSAPI_ERROR_WOULD_BLOCK)
+        ret = MBEDTLS_ERR_SSL_WANT_WRITE;
+    else if (ret < 0)
+        mbedtls_printf("socket.send() returned %d\n", ret);
+
+    return ret;
+}
+
+void HelloHttpsClient::sslDebug(void *ctx, int level, const char *file,
+                                int line, const char *str)
+{
+    (void)ctx;
+
+    const char *p, *basename;
+
+    /* Extract basename from file */
+    for (p = basename = file; *p != '\0'; p++) {
+        if (*p == '/' || *p == '\\')
+            basename = p + 1;
+    }
+
+    mbedtls_printf("%s:%d: |%d| %s\r", basename, line, level, str);
+}
+
+int HelloHttpsClient::sslVerify(void *ctx, mbedtls_x509_crt *crt, int depth,
+                                uint32_t *flags)
+{
+    HelloHttpsClient *client = static_cast<HelloHttpsClient *>(ctx);
+
+    int ret = -1;
+
+    ret = mbedtls_x509_crt_info(client->gp_buf, sizeof(gp_buf), "\r  ", crt);
+    if (ret < 0) {
+        mbedtls_printf("mbedtls_x509_crt_info() returned -0x%04X\n", -ret);
+    } else {
+        ret = 0;
+        mbedtls_printf("Verifying certificate at depth %d:\n%s\n",
+                       depth, client->gp_buf);
+    }
+
+    return ret;
+}
+