Proxy HTTP request

Today I was working with HTTP protocol, I had to connect to web server over proxy using C and Sockets.
For this task you have to connect with the proxy and it'll redirect your request to your requested web server, if you are authenticated.
My Proxy uses Basic Authorization then I had to send the login information (userid and password) in base64 format. For this task I used OpenSSL one more time.
Once you are authenticated, and you have send a GET request correctly formated, proxy will send response to you.

Bellow I write a necesary code to do this connection. I hope it'll be usefull for you.


// Proxy.c : HTTP/HTTPS Request example
//

#include <stdio.h>
#include <memory.h>
#include <errno.h>
#include <sys/types.h>

#ifdef WIN32
#include <winsock.h>
#else
#include <sys/socket.h>
#include <netinet/in.h>
#endif

#include <openssl/sha.h>
#include <openssl/hmac.h>
#include <openssl/evp.h>
#include <openssl/bio.h>
#include <openssl/buffer.h>

#include "applink.c"

// OpenSSL functions
void OpenSSL_add_all_algorithms();
void ERR_load_crypto_strings();
void ENGINE_load_builtin_engines();

// my functions
char *base64(const unsigned char *input, int length);
BOOL sendGet(const char* host, const char* dir, const char* proxy,
unsigned short proxyPort, const char* uid, const char* pwd);
char* GetIpAddress(char* host);
long getLen(char* cadena, long *bytes);

#define MAXLEN 10000

int main (int argc, char* argv[])
{
    char ret[2500]="";
    boolean r=FALSE;

    // OpenSSL Init
    _fmode=_O_BINARY;
    CRYPTO_malloc_init();
    ERR_load_crypto_strings();
    OpenSSL_add_all_algorithms();
    ENGINE_load_builtin_engines();

vERR_load_crypto_strings();

    // HTTPS connection example
    r= sendGet("www.ingdirect.es:443", "CONNECT www.ingdirect.es:443 ", "myproxy.es", 8080, "uid", "pwd");
    // Ejemplo HTTP
    r= sendGet("www.elmundo.es", "GET /", "myproxy.es", 8080, "uid", "pwd");

    return 0;
}


/*
*
* Sends a HTTP request
*
*/
BOOL sendGet(const char* host, const char* dir, const char* proxy,
unsigned short proxyPort, const char* uid, const char* pwd)
{
    int iProtocolPort = 0;
    char szBuffer[MAXLEN] = "";
    SOCKET sd;
    struct sockaddr_in sa;
    char proxySrv[16]="";
    char login[200]="";
    boolean loop=TRUE;
    int ret=0;
    FILE *file=NULL;
    int len=0;
    long bytes=0;

    #ifdef WIN32
        int err=0;
        WORD wVersionRequested;
        WSADATA wsaData;

        wVersionRequested = MAKEWORD( 1, 1 );
        err = WSAStartup(wVersionRequested, &wsaData );
        if ( err != 0 )
        {
            return FALSE;
        }
    #endif

    // Translate hostname to ip address
    strcpy(proxySrv, GetIpAddress((char*)proxy));

    // creating Socket
    sd = socket(PF_INET, SOCK_STREAM, 0);
    if (sd == INVALID_SOCKET)
    {
        // Can't open the socket
        return FALSE;
    }


    memset (&sa, '\0', sizeof(sa));
    sa.sin_family = AF_INET;
    sa.sin_addr.s_addr = inet_addr (proxySrv); /* Proxy Ip */
    sa.sin_port = htons(proxyPort); /* Proxy Port */


    // Connecting to Proxy
    if(connect(sd, (struct sockaddr*) &sa, sizeof(sa)))
    {
        // Error connecting proxy!
        return FALSE;
    }

    // Init Request
    sprintf(szBuffer,"%s HTTP/1.1\r\nHost:%s\r\n", dir,host);

    // setting login information
    strcat(szBuffer,"Proxy-authorization:Basic ");
    strcpy(login,uid);
    strcat(login, ":");
    strcat(login,pwd);
    strcpy(login, base64(login, strlen(login)));
    strcat(szBuffer,login);
    strcat(szBuffer, "\r\n\r\n");

    // Sending request
    send(sd,szBuffer,strlen(szBuffer),0);

    // Proxy response
    bytes=recv(sd, szBuffer, sizeof(szBuffer), 0);
    file=fopen("c:\\index.html","w");
    len=getLen(szBuffer, &bytes);


    fprintf(file, "%s", szBuffer);
    fflush(file);

    if(bytes>0 && strncmp(szBuffer+strlen(szBuffer)-4,"\r\n\r\n",4)!=0 && (len>0 && len>bytes)){
        // Writing proxy response
        do{
            ret=recv(sd, szBuffer, sizeof(szBuffer), 0);
            bytes+=ret;
            if(ret<0 || strncmp(szBuffer+strlen(szBuffer)-4,"\r\n\r\n",4)==0 || (len>0 && len<bytes)){
                loop=FALSE;
            }
            fprintf(file, "%s",szBuffer);
            fflush(file);
        }while(loop);
    }
    fclose(file);

    // closing connection
    #ifdef WIN32
        closesocket (sd);
        // free resources
        WSACleanup();

    #else
        close(sd);
    #endif

    return TRUE;
}

/*
*
* Returns a Base64 string
*
*/
char *base64(const unsigned char *input, int length)
{
    BIO *bmem, *b64;
    BUF_MEM *bptr;
    char *buff="";

    b64 = BIO_new(BIO_f_base64());
    bmem = BIO_new(BIO_s_mem());
    b64 = BIO_push(b64, bmem);
    BIO_write(b64, input, length);
    BIO_flush(b64);
    BIO_get_mem_ptr(b64, &bptr);

    buff = (char *)malloc(bptr->length);
    memcpy(buff, bptr->data, bptr->length-1);
    buff[bptr->length-1] = 0;

    BIO_free_all(b64);

    return buff;
}

/*
*
* Translate hostname to ip address
*
*/
char* GetIpAddress(char *hostname)
{

    struct sockaddr_in SocketAddress;
    struct hostent *pHost = 0;
    char aszIPAddresses[16];
    int iCnt=0;

    pHost = gethostbyname(hostname);
    if(!pHost)
        return "";

    // Recupero la primera ip del Servidor
    memcpy(&SocketAddress.sin_addr, pHost->h_addr_list[0], pHost->h_length);
    strcpy(aszIPAddresses, inet_ntoa(SocketAddress.sin_addr));

    // Retorno la ip
    return aszIPAddresses;

}


/*
*
* Returns length data from Content-Length header
*
*/

long getLen(char* cadena, long *bytes){
    int t=0;
    char len[10];

    while(t<MAXLEN){
        if(strncmp(cadena+t,"Content-Length:",15)==0){
            int f=t+16;
            while(cadena[f]!='\r')
                f++;
            memcpy(len, cadena+t+16,f-(t+16));
            while(strncmp(cadena+f,"\r\n\r\n",4)!=0)
                f++;
            *bytes=*bytes-f;
            return atol(len);
        }
        t++;
    }

    return -1;

}

Socket eMail Example

Hi Friends, today We need to send a simple alert mail from our application and I have wanted to send this email from C using sockets.

It isn't difficult, you need to open a socket connection to the server using the port of email service and exchange some messages to send the alert message.

All messages you have to send, should be terminated by "\r\n" and after each message you have to call to recv function to get the response from the server.

The first message to send to the Server is the HELO %s\r\n message, replacing %s with the server ip address.

After this message you have to send the EHLO\r\n message, this message will be responsed by the Server with all operations permited by the server.

If you need to send some login information to your email server, you'll need to send the auth\r\n message and after this, you'll have to send the user uid\r\n and pwd\r\n in base64 format.
To do this, I've used Openssl again.

At this point you have to send the information about the from address, to address, subject and body.

For ending the comunication with the server you need to send a blank line and after this blank line send a quit\r\n message.

Bellow I paste the code I've used to do this, I hope it'll be useful for you


// Mail.c : email function example
//

#include <stdio.h>
#include <memory.h>
#include <errno.h>
#includee <sys/types.h>
#ifdef WIN32
  #include <winsock.h>
#else
  #include <sys/socket.h>
  #include <netinet/in.h>
#endif

#include <openssl/bio.h>
#include <openssl/evp.h>
#include "applink.c"

BIO_METHOD * BIO_f_base64(void);

#include <openssl/sha.h>
#include <openssl/hmac.h>
#include <openssl/evp.h>
#include <openssl/bio.h>
#include <openssl/buffer.h>

char *base64(const unsigned char *input, int length);


int main (int argc, char* argv[])
{
  char ret[2500]="";

  // Init OpenSSL
  _fmode=_O_BINARY;
  CRYPTO_malloc_init();
  ERR_load_crypto_strings();
  OpenSSL_add_all_algorithms();
  ENGINE_load_builtin_engines();

  ERR_load_crypto_strings();

  return SendMail("uid@server.es","uidTo@server.es", "MailServerIp", "Subject", "UID","PWD", "Message");

}


/*
*
* Send Text Mail from user requested to the target user, using the server and the specified credentials.
*
*/
BOOL SendMail(const char* _From, const char* _To, const char* host,
const char* _Subject, const char* uid, const char* pwd, const char* _MessageFormat, ...)
{
  int iProtocolPort = 0;
  char szBuffer[4096] = "";
  SOCKET sd;
  struct sockaddr_in sa;
  LPSERVENT lpServEntry;
  va_list message_parts;
  char message[65536];
  int err=0;
  char _SMTP[16]="";
  #ifdef WIN32
    WORD wVersionRequested;
    WSADATA wsaData;
  #endif

  #ifdef WIN32
    wVersionRequested = MAKEWORD( 1, 1 );
    err = WSAStartup(wVersionRequested, &wsaData );
    if ( err != 0 )
    {
      exit(1);
    }
  #endif

  // traslating namehost to ip address
  strcpy(_SMTP, GetIpAddress((char*)host));

  // creating the Socket
  sd = socket(PF_INET, SOCK_STREAM, 0);
  if (sd == INVALID_SOCKET)
  {
    // Cannot open mail server socket!
    return FALSE;
    }

  // Getting the mail port
  lpServEntry = getservbyname("mail", 0);

  // if we havent't a port, we use the default port to SMTP
  if (!lpServEntry)
    iProtocolPort = htons(IPPORT_SMTP);
  else
    iProtocolPort = lpServEntry->s_port;

  memset (&sa, '\0', sizeof(sa));
  sa.sin_family = AF_INET;
  sa.sin_addr.s_addr = inet_addr (_SMTP); /* Server IP*/
  sa.sin_port = (iProtocolPort); /* Server Port*/


  // Connecting to the Server
  if(connect(sd, (struct sockaddr*) &sa, sizeof(sa)))
  {
    // Error connecting to the Server!
    return FALSE;
  }

  // Initial response from the Server
  recv(sd, szBuffer, sizeof(szBuffer), 0);

  // Init dialog
  sprintf(szBuffer, "HELO %s\r\n", _SMTP);
  send(sd, szBuffer, strlen(szBuffer), 0);
  recv(sd, szBuffer, sizeof(szBuffer), 0);


  sprintf(szBuffer,"ehlo\r\n");
  send(sd,szBuffer,strlen(szBuffer),0);
  recv(sd,szBuffer,sizeof(szBuffer),0);

  // Sending login
  strcpy(szBuffer, "auth login\r\n");
  send(sd, szBuffer, strlen(szBuffer), 0);
  recv(sd, szBuffer, sizeof(szBuffer), 0);

  // Send userid
  sprintf(szBuffer,"%s\r\n", base64(uid, strlen(uid)));
  send(sd, szBuffer, strlen(szBuffer), 0);
  recv(sd, szBuffer, sizeof(szBuffer), 0);


  // Send Pwd
  sprintf(szBuffer,"%s\r\n", base64(pwd, strlen(pwd)));
  send(sd, szBuffer, strlen(szBuffer), 0);
  recv(sd, szBuffer, sizeof(szBuffer), 0);

  // send From
  sprintf(szBuffer, "MAIL FROM:<%s>\r\n", _From);
  send(sd, szBuffer, strlen(szBuffer), 0);
  recv(sd, szBuffer, sizeof(szBuffer), 0);

  // Send To
  // repeat for each target address
  sprintf(szBuffer, "RCPT TO:<%s>\r\n", _To);
  send(sd, szBuffer, strlen(szBuffer), 0);
  recv(sd, szBuffer, sizeof(szBuffer), 0);

  // Send Data
  sprintf(szBuffer, "DATA\r\n");
  send(sd, szBuffer, strlen(szBuffer), 0);
  recv(sd, szBuffer, sizeof(szBuffer), 0);

  // Preparing the string to send
  va_start(message_parts, _MessageFormat);
  vsprintf(message, _MessageFormat, message_parts);
  va_end(message_parts);

  // Setting Subject and Body
  sprintf(szBuffer,"Subject: %s\r\n\r\n%s\r\n.\r\n",_Subject, message);


  // Send a blank line to end the transmision
  send(sd, szBuffer, strlen(szBuffer), 0);
  recv(sd, szBuffer, sizeof(szBuffer), 0);

  // Sending end command
  sprintf(szBuffer, "quit\r\n");
  send(sd, szBuffer, strlen(szBuffer), 0);
  recv(sd, szBuffer, sizeof(szBuffer), 0);

  // closing the connection
  #ifdef WIN32
    closesocket (sd);
  #else
    close(sd);
  #endif

  return TRUE;
}


char *base64(const unsigned char *input, int length)
{
  BIO *bmem, *b64;
  BUF_MEM *bptr;
  char *buff="";

  b64 = BIO_new(BIO_f_base64());
  bmem = BIO_new(BIO_s_mem());
  b64 = BIO_push(b64, bmem);
  BIO_write(b64, input, length);
  BIO_flush(b64);
  BIO_get_mem_ptr(b64, &bptr);

  buff = (char *)malloc(bptr->length);
  memcpy(buff, bptr->data, bptr->length-1);
  buff[bptr->length-1] = 0;

  BIO_free_all(b64);

  return buff;
}

/*
*
* Return Ip from hostname
*
*/
char* GetIpAddress(char *hostname)
{

  struct sockaddr_in SocketAddress;
  struct hostent *pHost = 0;
  char aszIPAddresses[16];
  int iCnt=0;

  pHost = gethostbyname(hostname);
  if(!pHost)
    return "";

  // get first server ip
  memcpy(&SocketAddress.sin_addr, pHost->h_addr_list[0], pHost->h_length);
  strcpy(aszIPAddresses, inet_ntoa(SocketAddress.sin_addr));

  // returning ip
  return aszIPAddresses;

}

SSL OpenSSL with Visual C++

Today I have another solution to work with SSL from Visual C++ using OpenSSL.

Well, the OpenSSL compilation was described before, so I can’t described here again. Click here if you want to know more about OpenSSL compilation

To work with SSL is easy with OpenSSL, really is a layer to add to our Windows Socket Projects.

The steps you’ll have to do are:

1. Add the OpenSSL libs (libeay32.lib, ssleay32.lib) to your project in Link options. Well, and touch some different options in this sheet, download the projects to see more about this point.
2. Add the OpenSSL header files to your main cpp.
3. And the OpenSSL SSL commands.

Here is the sample server code:

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <errno.h>
#include <sys/types.h>
#include <winsock.h>

#include <openssl/rsa.h>
#include <openssl/crypto.h>
#include <openssl/x509.h>
#include <openssl/pem.h>
#include <openssl/ssl.h>
#include <openssl/err.h>


/* certificates root path */
#define HOME "./"
/* certificate and private key */
#define CERTF HOME "micert.pem"
#define KEYF HOME "mikey.key"

/* checking fuctions */
#define CHK_NULL(x) if ((x)==NULL) exit (1)
#define CHK_ERR(err,s) if ((err)==-1) { perror(s); exit(1); }
#define CHK_SSL(err) if ((err)==-1) { ERR_print_errors_fp(stderr); exit(2); }

int err;


void main ()
{
int err;
int listen_sd;
int sd;
struct sockaddr_in sa_serv;
struct sockaddr_in sa_cli;
int client_len;
SSL_CTX* ctx;
SSL* ssl;
X509* client_cert;
char* str;
char buf [4096];
SSL_METHOD *meth;
WORD wVersionRequested;
WSADATA wsaData;

/* SSL init. Keep the Key and the certificate in the context. */

SSL_load_error_strings();
SSLeay_add_ssl_algorithms();
meth = SSLv23_server_method();
ctx = SSL_CTX_new (meth);
if (!ctx) {
    ERR_print_errors_fp(stderr);
    exit(2);
}

if (SSL_CTX_use_certificate_file(ctx, CERTF, SSL_FILETYPE_PEM) <= 0) {
    ERR_print_errors_fp(stderr);
    exit(3);
}
if (SSL_CTX_use_PrivateKey_file(ctx, KEYF, SSL_FILETYPE_PEM) <= 0) {
    ERR_print_errors_fp(stderr);
    exit(4);
}

if (!SSL_CTX_check_private_key(ctx)) {
    fprintf(stderr,"The private Key don’t match with the certificate\n");
    exit(5);
}

/*****************************************************/
/*                                                   */
/* Socket Initialitation */
/*                                                   */
/*****************************************************/


wVersionRequested = MAKEWORD( 1, 1 );
err = WSAStartup(wVersionRequested, &wsaData );
if ( err != 0 )
{
    printf("///Error in WSAStartup//%d\n",err);
    exit(err);

}

listen_sd = socket (AF_INET, SOCK_STREAM, 0);
printf("socket() return 0x%X (%d)\n", listen_sd, listen_sd);
CHK_ERR(listen_sd, "socket");

memset (&sa_serv, '\0', sizeof(sa_serv));
sa_serv.sin_family = AF_INET;
sa_serv.sin_addr.s_addr = INADDR_ANY;
sa_serv.sin_port = htons (9000); /* Server listen Port */

err = bind(listen_sd, (struct sockaddr*) &sa_serv,
sizeof (sa_serv));
CHK_ERR(err, "bind");

/*****************************************************/
/*                                                   */
/* setting listening */
/*                                                   */
/*****************************************************/

printf("listening\n");
err = listen (listen_sd, 5); CHK_ERR(err, "listen");

client_len = sizeof(sa_cli);
sd = accept (listen_sd, (struct sockaddr*) &sa_cli, &client_len);
CHK_ERR(sd, "accept");
closesocket (listen_sd);

printf ("Connection from %lx, port %x\n",
sa_cli.sin_addr.s_addr, sa_cli.sin_port);

/*****************************************************/
/*                                                   */
/* preparing SSL with the recived socket */
/*                                                   */
/*****************************************************/

ssl = SSL_new (ctx); CHK_NULL(ssl);
SSL_set_fd (ssl, sd);
err = SSL_accept (ssl); CHK_SSL(err);

/* Showing cipher - optional */

printf ("SSL connection using %s\n", SSL_get_cipher (ssl));

/* Get Client cert, if exist - optional */

client_cert = SSL_get_peer_certificate (ssl);
if (client_cert != NULL) {
    printf ("Client Certificate:\n");

    str = X509_NAME_oneline (X509_get_subject_name (client_cert), 0, 0);
    CHK_NULL(str);
    printf ("\t subject: %s\n", str);
    OPENSSL_free (str);

    str = X509_NAME_oneline (X509_get_issuer_name (client_cert), 0, 0);
    CHK_NULL(str);
    printf ("\t issuer: %s\n", str);
    OPENSSL_free (str);

    /* Here we could check all we want about client certificate. */

    X509_free (client_cert);
} else
    printf ("The Client hasn’t certificate.\n");

/* Exchanging messages */

err = SSL_read (ssl, buf, sizeof(buf) - 1); CHK_SSL(err);
buf[err] = '\0';
printf ("Read %d characters:'%s'\n", err, buf);

err = SSL_write (ssl, "I’m listening.", strlen("I’m listening.")); CHK_SSL(err);

/* Freeing resources */

closesocket (sd);
SSL_free (ssl);
SSL_CTX_free (ctx);
}

Bellow is the SSL Client Code.

#include <stdio.h>
#include <memory.h>
#include <errno.h>
#include <sys/types.h>
#include <winsock.h>

#include <openssl/crypto.h>
#include <openssl/x509.h>
#include <openssl/pem.h>
#include <openssl/ssl.h>
#include <openssl/err.h>


#define CHK_NULL(x) if ((x)==NULL) exit (1)
#define CHK_ERR(err,s) if ((err)==-1) { perror(s); exit(1); }
#define CHK_SSL(err) if ((err)==-1) { ERR_print_errors_fp(stderr); exit(2); }

void main ()
{
int err=0;
int sd;
struct sockaddr_in sa;
SSL_CTX* ctx;
SSL* ssl;
X509* scert;
char* txt;
char buff [4096];
SSL_METHOD *meth;
WORD wVersionRequested;
WSADATA wsaData;
SSLeay_add_ssl_algorithms();
meth = SSLv2_client_method();
SSL_load_error_strings();
ctx = SSL_CTX_new (meth); CHK_NULL(ctx);

CHK_SSL(err);

/*****************************************************/
/*                                                   */
/* Socket Init and connecting. */
/*                                                   */
/*****************************************************/

wVersionRequested = MAKEWORD( 1, 1 );
err = WSAStartup(wVersionRequested, &wsaData );
if ( err != 0 )
{
    printf("///Error in WSAStartup //%d\n",err);
    exit(1);

}


sd = socket (AF_INET, SOCK_STREAM, 0);
CHK_ERR(sd, "socket");

memset (&sa, '\0', sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_addr.s_addr = inet_addr ("127.0.0.1"); /* Server Ip */
sa.sin_port = htons (9000); /* Server port */

err = connect(sd, (struct sockaddr*) &sa,
sizeof(sa)); CHK_ERR(err, "connection");

/*****************************************************/
/*                                                   */
/* Starting SSL connection */
/*                                                   */
/*****************************************************/

ssl = SSL_new (ctx); CHK_NULL(ssl);
SSL_set_fd (ssl, sd);
err = SSL_connect (ssl); CHK_SSL(err);

/* Get the cipher - optional */

printf ("SSL connection using %s\n", SSL_get_cipher (ssl));

/* Get Server certificate - optional */

scert = SSL_get_peer_certificate (ssl); CHK_NULL(scert);
printf ("Server Certificate:\n");

txt = X509_NAME_oneline (X509_get_subject_name (scert),0,0);
CHK_NULL(txt);
printf ("\t Subject: %s\n", txt);
OPENSSL_free (txt);

txt = X509_NAME_oneline (X509_get_issuer_name (scert),0,0);
CHK_NULL(txt);
printf ("\t Issuer: %s\n", txt);
OPENSSL_free (txt);

/* Here we can check what we wanted about the Server certificate */

X509_free (scert);

/*****************************************************/
/*                                                   */
/* Exchanging messages */
/*                                                   */
/*****************************************************/

err = SSL_write (ssl, "Is someone there?", strlen("Is someone there?")); CHK_SSL(err);

err = SSL_read (ssl, buff, sizeof(buff) - 1); CHK_SSL(err);
buff[err] = '\0';
printf ("Read %d characters:'%s'\n", err, buff);
SSL_shutdown (ssl); /* sending the SSL/TLS end*/

/* Freeing resources */

closesocket (sd);
SSL_free (ssl);
SSL_CTX_free (ctx);
}


If you want to download the client and Server projects, click here. Source Files

CSoap and Visual Studio

First of all, I’m sorry for my English, but I want to improve it and this is a good way.

Well, this is my first solution.

Many times I have had to connect a c program to a Web Service, in Windows with MFC is too easy. I have a dll, which connects the c program with whatever Web Service only updating some xml files.

But, when you need to connect a c program running in other OS, you'll need to try other solutions.

The best, for me, it's CSoap.

However when I had to develop that connection I only had Windows Systems and well, I tried to connect CSoap in a Visual Studio Project.

It wasn't easy for me to find examples about CSOAP for Visual C++, and that is why I put that solution here.

Here is the original link to my source files https://sourceforge.net/tracker/download.php?group_id=74977&atid=542567&file_id=250457&aid=1816455