#include "stdafx.h"

// Hack due to MFC project strangeness
#define _WIN32_WINNT 0x0500
#include <wincrypt.h>

#include "interface.h"

/*
 * This method computes the MD5 hash of the secret, text and destination
 * address. It should be clear how this can be extended to other hash
 * algorithms and arbitrary data.
 */
char* computeMD5Hash(const char* secret,
                     const char* shortmessage,
                     const char* destaddr)
{
    // Variables used during the hashing process
    HCRYPTPROV cryptoProvider;
    HCRYPTHASH rawHash;

    // Get the cryptographic provider for MD5 hashing
    // NOTE: This call could (potentially) fail and this should be checked for
    CryptAcquireContext(&cryptoProvider,
                        NULL,
                        NULL,
                        PROV_RSA_FULL,
                        CRYPT_VERIFYCONTEXT);

    // Create an object that will perform the hash
    // NOTE: This call could (potentially) fail and this should be checked for
    CryptCreateHash(cryptoProvider,
                    CALG_MD5,
                    0,
                    0,
                    &rawHash);

    // Feed data into the hash
    // NOTE: These calls could (potentially) fail and this should be checked for
    CryptHashData(rawHash, (unsigned char*)secret, strlen(secret), 0);
    CryptHashData(rawHash,
                  (unsigned char*)shortmessage,
                  strlen(shortmessage),
                  0);
    CryptHashData(rawHash, (unsigned char*)destaddr, strlen(destaddr), 0);

    // Extract the hash data
    // NOTE: This call could (potentially) fail and this should be checked for
    DWORD hashLength = 16; //(MD5 length)
    unsigned char* hashData = new unsigned char[hashLength];
    CryptGetHashParam(rawHash, HP_HASHVAL, hashData, &hashLength, 0);

    // Create a hex-encoded string of the hash bytes
    char lut[] = { '0', '1', '2', '3', '4', '5', '6', '7',
                   '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
    char* hash = new char[33];
    for(int i = 0; i < 16; i++) {
        hash[2 * i] = lut[(hashData[i] & 0xF0) >> 4];
        hash[2 * i + 1] = lut[hashData[i] & 0x0F];
    }
    hash[32] = '\0';

    // After processing, cryptoProvider and hasher must be released.
    if(rawHash) {
        CryptDestroyHash(rawHash);
    }
    if(cryptoProvider) {
        CryptReleaseContext(cryptoProvider, 0);
    }

    delete[] hashData;

    return hash;
}

/*
 * This method performs the actual HTTP request that sends the SMS. It also
 * contains the information that is used to form the request.
 */
char* send_ems(char* destaddr) {
    const char* host = "194.247.82.149";
    const int port = 80;
    const char* action = "submitsm";
    const char* client_id = "<your client_id>";
    const char* shortmessage = "7C0C7A00424547494E3A494D454C4F44590D0A5645525" \
        "3494F4E3A312E320D0A464F524D41543A434C415353312E300D0A4D454C4F44593A6" \
        "43323633364332363336433723264332363336433653323663365332366336733613" \
        "3236733613323673361337232613323673361330D0A454E443A494D454C4F44590D0A";
    const char* secret = "<your secret>";
    char* hash = computeMD5Hash(secret, shortmessage, destaddr);

    // Format the URL/request
    const char* pattern = "GET /%s/?client_id=%s&destaddr=%s&esm=64" \
        "&shortmessage=%s&key=%s HTTP/1.0\r\n\r\n"
    int buffer_size = strlen(action) + strlen(client_id) + strlen(destaddr)
                     + strlen(shortmessage) + strlen(hash) + 80;
    char* buffer = new char[buffer_size];
    sprintf(buffer,
            pattern,
            action,
            client_id,
            destaddr,
            shortmessage,
            hash);

    // Clean up
    delete[] hash;

    // Create the socket
    CSocket socket;
    socket.Create();

    // Try to connect to the server
    if(!socket.Connect( host, port )) {
        MessageBox( NULL, "unable to connect, check settings", "Error", MB_OK );
    }

    // These variables are used during the request and response code
    int bytesToIO = strlen(buffer);
    int totalBytesIOd = 0;
    int bytesIOd = 0;

    // Send the request
    while(totalBytesIOd < bytesToIO
           && (bytesIOd = socket.Send(buffer + totalBytesIOd,
                                      bytesToIO - totalBytesIOd,
                                      0)) > 0)
    {
        totalBytesIOd += bytesIOd;
    }

    // If any errors occurred in the read process, bytesIOd will be SOCKET_ERROR
    // and appropriate action should be taken

    // Re-allocate the buffer for storing the response
    delete[] buffer;
    buffer = new char[4096];

    // Receive the response
    bytesIOd = 0;
    totalBytesIOd = 0;
    while(totalBytesIOd < 4096
           && (bytesIOd = socket.Receive(buffer + totalBytesIOd,
                                         4096 - totalBytesIOd, 0)) > 0)
    {
        totalBytesIOd += bytesIOd;
    }

    // If any errors occurred in the read process, bytesIOd will be SOCKET_ERROR
    // and appropriate action should be taken

    // NULL-terminate the response we've read
    buffer[totalBytesIOd] = '\0';

    // Close the socket
    socket.Close();

    // Return the result of the request
    return buffer;
}