Havenard

/*
 * Simple HTTP Proxy Daemon by Havenard <havenard@hotmail.com>
 *
 *  Compile: gcc proxy.c -o proxy
 *      Use: ./proxy
 *       Or: ./proxy port
 *  Exemple: ./proxy 1337
 *
 */

#include <stdio.h>
#include <time.h>
#include <signal.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

#define INVALID_SOCKET -1
typedef int SOCKET;

typedef struct complete_socket { /* < 0x0001.txt */
  SOCKET handle;
  struct sockaddr_in addr;
  char *buffer;
} complete_socket; /* > 0x0001.txt */

const char http_foot[] = "\x0d\x0a\x0d\x0a";
const char http_vers[] = " HTTP/1.";
const char http_200[] = "HTTP/1.0 200 OK\x0d\x0a\x0d\x0a";

long int strpos(const char *m, const char *s);
int resolve(char *host);

int main(int argc, char **argv) {
  complete_socket s_receiver, s_client, s_remote; /* < 0x0002.txt */
  struct timeval tv;
  fd_set fdsets;
  int i, size;
  int port, s_port; /* > 0x0002.txt */

  if (!((argc > 1) && ((port = atoi(argv[1])) > 0)))
    port = 6589; /* Se nao foi especificada porta ou a porta e' invalida, usa-se a porta padrao 6589 */
  bzero((char *)&s_receiver, sizeof(complete_socket));
  bzero((char *)&s_client, sizeof(complete_socket));
  bzero((char *)&s_remote, sizeof(complete_socket));
  s_client.buffer = (char *)malloc(8193); /* < 0x0003.txt */
  s_remote.buffer = (char *)malloc(8193);
  if ((s_client.buffer < 0) || (s_remote.buffer < 0)) {
    printf("[-] Unable to alloc memory.\n");
    exit(-1);
  } /* > 0x0003.txt */
  if ((s_receiver.handle = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) { /* < 0x0004.txt */
    printf("[-] Unable to create a socket.\n");
    exit(-1);
  } /* > 0x0004.txt */

  bzero(s_client.buffer, 8193); /* Zerar a memoria dos buffers e' importante porque o programa precisara' */
  bzero(s_remote.buffer, 8193); /* saber quanta informacao ja' foi armazenada neles. */

  s_receiver.addr.sin_family = AF_INET; /* < 0x0005.txt */
  s_receiver.addr.sin_addr.s_addr = htonl(INADDR_ANY);
  s_receiver.addr.sin_port = htons(port);

  if (bind(s_receiver.handle, (struct sockaddr *)&s_receiver.addr, sizeof(struct sockaddr_in)) < 0) {
    printf("[-] Unable to bind socket to port %d, it may being used by another program.\n", port);
    exit(-1);
  }
  if (listen(s_receiver.handle, 10) < 0) {
    printf("[-] Unable to listen to port %d.\n", port);
    exit(-1);
  } /* > 0x0005.txt */
  printf("[+] Service activated successfully on port %d.\n", port);
  setsid(); /* < 0x0006.txt */
  signal(SIGCHLD, SIG_IGN);
  if (fork()) exit(0); /* > 0x0006.txt */
  while (1) { /* < 0x0007.txt */
    size = sizeof(struct sockaddr_in);
    if ((s_client.handle = accept(s_receiver.handle, (struct sockaddr *)&s_client.addr, &size)) != INVALID_SOCKET)
      if (!fork()) {
      close(s_receiver.handle); /* > 0x0007.txt */
      while (1) { /* < 0x0008.txt */
        tv.tv_sec  = 1;
        tv.tv_usec = 0;
        FD_ZERO(&fdsets);
        FD_SET(s_client.handle, &fdsets);
        if (s_remote.handle > 0)
          FD_SET(s_remote.handle, &fdsets);
        if (select((s_client.handle > s_remote.handle ? s_client.handle : s_remote.handle) +1, &fdsets, NULL, NULL, &tv) < 0) {
          close(s_client.handle);
          if (s_remote.handle > 0)
            close(s_remote.handle);
          exit(0);
        } /* > 0x0008.txt */
        if (FD_ISSET(s_client.handle, &fdsets)) {
          if (s_remote.handle == 0) {
            size = strlen(s_client.buffer);
            size = recv(s_client.handle, &s_client.buffer[size], 8192-size, 0);
            if (size < 1) {
              close(s_client.handle);
              exit(0);
            }
            if (strpos(http_foot, s_client.buffer) >= 0) {
              if (!strncasecmp("CONNECT ", s_client.buffer, 8)) {
                memcpy(s_remote.buffer, &s_client.buffer[8], 8192-8);
                if ((i = strpos(http_vers, s_remote.buffer)) < 0) {
                  close(s_client.handle);
                  exit(0);
                }
                s_remote.buffer[i] = '\x00';
                for (i = 0; i < 512; i++)
                  if ((s_remote.buffer[i] == '\x0d') || (s_remote.buffer[i] == '\x0a')) {
                    s_remote.buffer[i] = '\x00';
                    break;
                  }
                for (i = strlen(s_remote.buffer); i >= 0; i--)
                  if (s_remote.buffer[i] == '\\')
                    s_remote.buffer[i] = '/';
                if (strpos("/", s_remote.buffer) >= 0) {
                  close(s_client.handle);
                  exit(0);
                }
                s_port = 80;
                if ((i = strpos(":", s_remote.buffer)) >= 0) {
                  s_remote.buffer[i] = '\x00';
                  i++;
                  if ((s_port = atoi(&s_remote.buffer[i])) <= 0) {
                    close(s_client.handle);
                    exit(0);
                  }
                }
                s_remote.addr.sin_family = AF_INET;
                s_remote.addr.sin_port = htons(s_port);
                s_remote.addr.sin_addr.s_addr = resolve(s_remote.buffer);
                if (s_remote.addr.sin_addr.s_addr <= 0) {
                  close(s_client.handle);
                  exit(0);
                }
                if ((s_remote.handle = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) {
                  close(s_client.handle);
                  exit(0);
                }
                if (connect(s_remote.handle, (struct sockaddr *)&s_remote.addr, sizeof(struct sockaddr_in)) < 0) {
                  close(s_client.handle);
                  close(s_remote.handle);
                  exit(0);
                }
                send(s_client.handle, http_200, strlen(http_200), 0);
                bzero(s_client.buffer, 8192);
                bzero(s_remote.buffer, 8192);
              }
              else if (!strncasecmp("GET ", s_client.buffer, 4) || !strncasecmp("POST ", s_client.buffer, 5)) {
                if (!strncasecmp("GET ", s_client.buffer, 4))
                  memcpy(s_remote.buffer, &s_client.buffer[4], 8192-4);
                else
                  memcpy(s_remote.buffer, &s_client.buffer[5], 8192-5);
                if ((i = strpos(http_vers, s_remote.buffer)) < 0) {
                  close(s_client.handle);
                  exit(0);
                }
                s_remote.buffer[i] = '\x00';
                for (i = 0; i < 512; i++)
                  if ((s_remote.buffer[i] == '\x0d') || (s_remote.buffer[i] == '\x0a')) {
                    s_remote.buffer[i] = '\x00';
                    break;
                  }
                for (i = strlen(s_remote.buffer); i >= 0; i--)
                  if (s_remote.buffer[i] == '\\')
                    s_remote.buffer[i] = '/';
                if (s_remote.buffer[0] == '/') {
                  close(s_client.handle);
                  exit(0);
                }
                if (strncasecmp("http://", s_remote.buffer, 7)) {
                  close(s_client.handle);
                  exit(0);
                }
                for (i = strlen(s_remote.buffer); i >= 0; i--)
                  if (s_remote.buffer[i] == '/')
                    s_remote.buffer[i] = '\x00';
                s_port = 80;
                if ((i = strpos(":", &s_remote.buffer[7])) >= 0) {
                  i += 7;
                  s_remote.buffer[i] = '\x00';
                  i++;
                  if ((s_port = atoi(&s_remote.buffer[i])) <= 0) {
                    close(s_client.handle);
                    exit(0);
                  }
                }
                s_remote.addr.sin_family = AF_INET;
                s_remote.addr.sin_port = htons(s_port);
                s_remote.addr.sin_addr.s_addr = resolve(&s_remote.buffer[7]);
                if (s_remote.addr.sin_addr.s_addr <= 0) {
                  close(s_client.handle);
                  exit(0);
                }
                size = (toupper(s_client.buffer[0]) == 'G' ? 11 : 12);
                i = strpos("/", &s_client.buffer[size]);
                if (i < 0) {
                  close(s_client.handle);
                  exit(0);
                }
                if ((s_remote.handle = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) {
                  close(s_client.handle);
                  exit(0);
                }
                if (connect(s_remote.handle, (struct sockaddr *)&s_remote.addr, sizeof(struct sockaddr_in)) < 0) {
                  close(s_client.handle);
                  close(s_remote.handle);
                  exit(0);
                }
                memcpy(s_remote.buffer, s_client.buffer, (size == 11 ? 4 : 5));
                memcpy(&s_remote.buffer[(size == 11 ? 4 : 5)], &s_client.buffer[i+size], 8192-(i+size));
                send(s_remote.handle, s_remote.buffer, strlen(s_remote.buffer), 0);
              }
              else {
                close(s_client.handle);
                exit(0);
              }
            }
            else if (s_client.buffer[8191] != '\x00') {
              close(s_client.handle);
              exit(0);
            }
          }
          else {
            size = recv(s_client.handle, s_client.buffer, 8192, 0);
            if (size > 0)
              send(s_remote.handle, s_client.buffer, size, 0);
            else {
              close(s_client.handle);
              close(s_remote.handle);
              exit(0);
            }
          }
        }
        if ((s_remote.handle > 0) && FD_ISSET(s_remote.handle, &fdsets)) {
          size = recv(s_remote.handle, s_remote.buffer, 8192, 0);
          if (size > 0)
            send(s_client.handle, s_remote.buffer, size, 0);
          else {
            close(s_client.handle);
            close(s_remote.handle);
            exit(0);
          }
        }
      }
      exit(0);
    }
    close(s_client.handle);
  }
}

int resolve(char *host) {
  int result;
  struct hostent *dnslook;
  if ((result = inet_addr(host)) == INADDR_NONE) {
    if ((dnslook = gethostbyname(host)) == NULL)
      return 0;
    return ((struct in_addr *)(dnslook->h_addr))->s_addr;
  }
  return result;
}

long int strpos(const char *m, const char *s) {
  long int i, len, end;
  len = strlen(m);
  end = strlen(s) - len +1;
  if (end >= len)
    for (i = 0; i < end; i++)
      if (!strncmp(m, &s[i], len))
        return i;
  return -1;
}