mbed-os-example-http(s) using WNC 14A2A Data Module

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#ifndef _MBED_HTTPS_REQUEST_H_
#define _MBED_HTTPS_REQUEST_H_

/* Change to a number between 1 and 4 to debug the TLS connection */
#define DEBUG_LEVEL 0

#include <string>
#include <vector>
#include <map>
#include "http_parser.h"
#include "http_response.h"
#include "http_request_builder.h"
#include "http_response_parser.h"
#include "http_parsed_url.h"

#include "mbedtls/platform.h"
#include "mbedtls/ssl.h"
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include "mbedtls/error.h"

#if DEBUG_LEVEL > 0
#include "mbedtls/debug.h"
#endif

/**
 * \brief HttpsRequest implements the logic for interacting with HTTPS servers.
 */
class HttpsRequest {
public:
    /**
     * HttpsRequest Constructor
     * Initializes the TCP socket, sets up event handlers and flags.
     *
     * @param[in] net_iface The network interface
     * @param[in] ssl_ca_pem String containing the trusted CAs
     * @param[in] method HTTP method to use
     * @param[in] url URL to the resource
     * @param[in] body_callback Callback on which to retrieve chunks of the response body.
                                If not set, the complete body will be allocated on the HttpResponse object,
                                which might use lots of memory.
     */
    HttpsRequest(NetworkInterface* net_iface,
                 const char* ssl_ca_pem,
                 http_method method,
                 const char* url,
                 Callback<void(const char *at, size_t length)> body_callback = 0)
    {
        _parsed_url = new ParsedUrl(url);
        _body_callback = body_callback;
        _tcpsocket = new TCPSocket(net_iface);
        _request_builder = new HttpRequestBuilder(method, _parsed_url);
        _response = NULL;
        _debug = false;
        _ssl_ca_pem = ssl_ca_pem;

        DRBG_PERS = "mbed TLS helloword client";

        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);
    }

    /**
     * HttpsRequest Destructor
     */
    ~HttpsRequest() {
        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);

        if (_request_builder) {
            delete _request_builder;
        }

        if (_tcpsocket) {
            delete _tcpsocket;
        }

        if (_parsed_url) {
            delete _parsed_url;
        }

        if (_response) {
            delete _response;
        }

        // @todo: free DRBG_PERS ?
    }

    /**
     * Execute the HTTPS request.
     *
     * @param[in] body Pointer to the request body
     * @param[in] body_size Size of the request body
     * @return An HttpResponse pointer on success, or NULL on failure.
     *         See get_error() for the error code.
     */
    HttpResponse* send(const void* body = NULL, nsapi_size_t body_size = 0) {
        /* Initialize the flags */
        /*
         * Initialize TLS-related stuf.
         */
        int ret;
        if ((ret = mbedtls_ctr_drbg_seed(&_ctr_drbg, mbedtls_entropy_func, &_entropy,
                          (const unsigned char *) DRBG_PERS,
                          sizeof (DRBG_PERS))) != 0) {
            print_mbedtls_error("mbedtls_crt_drbg_init", ret);
            _error = ret;
            return NULL;
        }

        if ((ret = mbedtls_x509_crt_parse(&_cacert, (const unsigned char *)_ssl_ca_pem,
                           strlen(_ssl_ca_pem) + 1)) != 0) {
            print_mbedtls_error("mbedtls_x509_crt_parse", ret);
            _error = ret;
            return NULL;
        }

        if ((ret = mbedtls_ssl_config_defaults(&_ssl_conf,
                        MBEDTLS_SSL_IS_CLIENT,
                        MBEDTLS_SSL_TRANSPORT_STREAM,
                        MBEDTLS_SSL_PRESET_DEFAULT)) != 0) {
            print_mbedtls_error("mbedtls_ssl_config_defaults", ret);
            _error = ret;
            return NULL;
        }

        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 DEBUG_LEVEL > 0
        mbedtls_ssl_conf_verify(&_ssl_conf, my_verify, NULL);
        mbedtls_ssl_conf_dbg(&_ssl_conf, my_debug, NULL);
        mbedtls_debug_set_threshold(DEBUG_LEVEL);
#endif

        if ((ret = mbedtls_ssl_setup(&_ssl, &_ssl_conf)) != 0) {
            print_mbedtls_error("mbedtls_ssl_setup", ret);
            _error = ret;
            return NULL;
        }

        mbedtls_ssl_set_hostname(&_ssl, _parsed_url->host());

        mbedtls_ssl_set_bio(&_ssl, static_cast<void *>(_tcpsocket),
                                   ssl_send, ssl_recv, NULL );

        /* Connect to the server */
        if (_debug) mbedtls_printf("Connecting to %s:%d\r\n", _parsed_url->host(), _parsed_url->port());
        ret = _tcpsocket->connect(_parsed_url->host(), _parsed_url->port());
        if (ret != NSAPI_ERROR_OK) {
            if (_debug) mbedtls_printf("Failed to connect\r\n");
            onError(_tcpsocket, -1);
            return NULL;
        }

       /* Start the handshake, the rest will be done in onReceive() */
        if (_debug) mbedtls_printf("Starting the TLS handshake...\r\n");
        ret = mbedtls_ssl_handshake(&_ssl);
        if (ret < 0) {
            if (ret != MBEDTLS_ERR_SSL_WANT_READ &&
                ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
                print_mbedtls_error("mbedtls_ssl_handshake", ret);
                onError(_tcpsocket, -1);
            }
            else {
                _error = ret;
            }
            return NULL;
        }

        char* request = _request_builder->build(body, body_size);
        size_t request_size = strlen(request);

        ret = mbedtls_ssl_write(&_ssl, (const unsigned char *) request, request_size);

        free(request);

        if (ret < 0) {
            if (ret != MBEDTLS_ERR_SSL_WANT_READ &&
                ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
                print_mbedtls_error("mbedtls_ssl_write", ret);
                onError(_tcpsocket, -1 );
            }
            else {
                _error = ret;
            }
            return NULL;
        }

        /* It also means the handshake is done, time to print info */
        if (_debug) mbedtls_printf("TLS connection to %s:%d established\r\n", _parsed_url->host(), _parsed_url->port());

        const uint32_t buf_size = 1024;
        char *buf = new char[buf_size];
        mbedtls_x509_crt_info(buf, buf_size, "\r    ",
                        mbedtls_ssl_get_peer_cert(&_ssl));
        if (_debug) mbedtls_printf("Server certificate:\r\n%s\r", buf);

        uint32_t flags = mbedtls_ssl_get_verify_result(&_ssl);
        if( flags != 0 )
        {
            mbedtls_x509_crt_verify_info(buf, buf_size, "\r  ! ", flags);
            if (_debug) mbedtls_printf("Certificate verification failed:\r\n%s\r\r\n", buf);
        }
        else {
            if (_debug) mbedtls_printf("Certificate verification passed\r\n\r\n");
        }

        // Create a response object
        _response = new HttpResponse();
        // And a response parser
        HttpResponseParser parser(_response, _body_callback);

        // Set up a receive buffer (on the heap)
        uint8_t* recv_buffer = (uint8_t*)malloc(HTTP_RECEIVE_BUFFER_SIZE);

        /* Read data out of the socket */
        while ((ret = mbedtls_ssl_read(&_ssl, (unsigned char *) recv_buffer, HTTP_RECEIVE_BUFFER_SIZE)) > 0) {
            // Don't know if this is actually needed, but OK
            size_t _bpos = static_cast<size_t>(ret);
            recv_buffer[_bpos] = 0;

            size_t nparsed = parser.execute((const char*)recv_buffer, _bpos);
            if (nparsed != _bpos) {
                print_mbedtls_error("parser_error", nparsed);
                // parser error...
                _error = -2101;
                free(recv_buffer);
                return NULL;
            }
            // No more chunks? break out of this loop
            if (_bpos < HTTP_RECEIVE_BUFFER_SIZE) {
                break;
            }
        }
        if (ret < 0) {
            if (ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
                print_mbedtls_error("mbedtls_ssl_read", ret);
                onError(_tcpsocket, -1 );
            }
            else {
                _error = ret;
            }
            free(recv_buffer);
            return NULL;
        }

        parser.finish();

        _tcpsocket->close();
        free(recv_buffer);

        return _response;
    }

    /**
     * Closes the TCP socket
     */
    void close() {
        _tcpsocket->close();
    }

    /**
     * Set a header for the request.
     *
     * The 'Host' and 'Content-Length' headers are set automatically.
     * Setting the same header twice will overwrite the previous entry.
     *
     * @param[in] key Header key
     * @param[in] value Header value
     */
    void set_header(string key, string value) {
        _request_builder->set_header(key, value);
    }

    /**
     * Get the error code.
     *
     * When send() fails, this error is set.
     */
    nsapi_error_t get_error() {
        return _error;
    }

    /**
     * Set the debug flag.
     *
     * If this flag is set, debug information from mbed TLS will be logged to stdout.
     */
    void set_debug(bool debug) {
        _debug = debug;
    }

protected:
    /**
     * Helper for pretty-printing mbed TLS error codes
     */
    static void print_mbedtls_error(const char *name, int err) {
        char buf[128];
        mbedtls_strerror(err, buf, sizeof (buf));
        mbedtls_printf("%s() failed: -0x%04x (%d): %s\r\n", name, -err, err, buf);
    }

#if DEBUG_LEVEL > 0
    /**
     * Debug callback for mbed TLS
     * Just prints on the USB serial port
     */
    static void my_debug(void *ctx, int level, const char *file, int line,
                         const char *str)
    {
        const char *p, *basename;
        (void) ctx;

        /* Extract basename from file */
        for(p = basename = file; *p != '\0'; p++) {
            if(*p == '/' || *p == '\\') {
                basename = p + 1;
            }
        }

        if (_debug) {
            mbedtls_printf("%s:%04d: |%d| %s", basename, line, level, str);
        }
    }

    /**
     * Certificate verification callback for mbed TLS
     * Here we only use it to display information on each cert in the chain
     */
    static int my_verify(void *data, mbedtls_x509_crt *crt, int depth, uint32_t *flags)
    {
        const uint32_t buf_size = 1024;
        char *buf = new char[buf_size];
        (void) data;

        if (_debug) mbedtls_printf("\nVerifying certificate at depth %d:\n", depth);
        mbedtls_x509_crt_info(buf, buf_size - 1, "  ", crt);
        if (_debug) mbedtls_printf("%s", buf);

        if (*flags == 0)
            if (_debug) mbedtls_printf("No verification issue for this certificate\n");
        else
        {
            mbedtls_x509_crt_verify_info(buf, buf_size, "  ! ", *flags);
            if (_debug) mbedtls_printf("%s\n", buf);
        }

        delete[] buf;
        return 0;
    }
#endif

    /**
     * Receive callback for mbed TLS
     */
    static int ssl_recv(void *ctx, unsigned char *buf, size_t len) {
        int recv = -1;
        TCPSocket *socket = static_cast<TCPSocket *>(ctx);
        recv = socket->recv(buf, len);

        if (NSAPI_ERROR_WOULD_BLOCK == recv) {
            return MBEDTLS_ERR_SSL_WANT_READ;
        }
        else if (recv < 0) {
            return -1;
        }
        else {
            return recv;
        }
   }

    /**
     * Send callback for mbed TLS
     */
    static int ssl_send(void *ctx, const unsigned char *buf, size_t len) {
       int size = -1;
        TCPSocket *socket = static_cast<TCPSocket *>(ctx);
        size = socket->send(buf, len);

        if(NSAPI_ERROR_WOULD_BLOCK == size) {
            return len;
        }
        else if (size < 0){
            return -1;
        }
        else {
            return size;
        }
    }

    void onError(TCPSocket *s, int error) {
        s->close();
        _error = error;
    }

protected:
    TCPSocket* _tcpsocket;

    Callback<void(const char *at, size_t length)> _body_callback;
    ParsedUrl* _parsed_url;
    HttpRequestBuilder* _request_builder;
    HttpResponse* _response;
    const char *DRBG_PERS;
    const char *_ssl_ca_pem;

    nsapi_error_t _error;
    bool _debug;

    mbedtls_entropy_context _entropy;
    mbedtls_ctr_drbg_context _ctr_drbg;
    mbedtls_x509_crt _cacert;
    mbedtls_ssl_context _ssl;
    mbedtls_ssl_config _ssl_conf;
};

#endif // _MBED_HTTPS_REQUEST_H_