// unix2inet-bridge (C) 2008 hcsw.org and Doug Hoyte
//
// Compilation: gcc -Wall -O3 unix2inet-bridge.c -o unix2inet-bridge
//
// Usage: unix2inet-bridge <port> <path to unix socket>
//
// This will then bridge all connections to port with the specified
// unix domain socket, suitable for scanning with Nmap, bridging unix
// sockets across the network, etc.
//
// Uncomment the #define DEBUG line to see connection logs on stdout.
//
// TODO:
//   * Currently only supports STREAM sockets
//   * Would be interesting to report if the unix end ever sends
//     messages (see man cmsg)

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/select.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <netinet/in.h>
#include <arpa/inet.h>

//#define DEBUG


int conn_unix(char *path) {
  struct sockaddr_un address;
  size_t address_len;
  int sd;

  sd = socket(PF_UNIX, SOCK_STREAM, 0);
  if (sd < 0) {
    fprintf(stderr, "Error creating socket: %s\n", strerror(errno));
    return -1;
  }

  address.sun_family = AF_UNIX;
  strcpy(address.sun_path, path);
  address_len = sizeof(address.sun_family) + strlen(path) + 1;

  if(connect(sd, (struct sockaddr *) &address, address_len) != 0) {
    fprintf(stderr, "Error connecting to '%s': %s\n", path, strerror(errno));
    close(sd);
    return -1;
  }

  return sd;
}


int listen_inet(int port) {
  struct sockaddr_in my_addr;
  int sd, tp=0;

  if ((sd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
    fprintf(stderr, "Error creating socket: %s\n", strerror(errno));
    return -1;
  }

  setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, &tp, sizeof(tp));

  my_addr.sin_family = AF_INET;
  my_addr.sin_port = htons(port);
  my_addr.sin_addr.s_addr = INADDR_ANY;
  memset(&(my_addr.sin_zero), 0, 8);

  if (bind(sd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1) {
    fprintf(stderr, "Error binding to port %d: %s\n", port, strerror(errno));
    close(sd);
    return -1;
  }

  if (listen(sd, 5) == -1) {
    fprintf(stderr, "Error listening: %s\n", strerror(errno));
    close(sd);
    return -1;
  }

  return sd;
}


void proc_bridge(int insd, int unsd) {
  fd_set rfds;
  int rv;
  char buf[4096];
  int offset, len;

  while(1) {
    FD_ZERO(&rfds);
    FD_SET(insd, &rfds);
    FD_SET(unsd, &rfds);

    rv = select(insd>unsd ? insd+1 : unsd+1, &rfds, NULL, NULL, NULL);

    if (rv == -1) return;

    if (FD_ISSET(insd, &rfds)) {
      offset = 0;
      len = read(insd, buf, sizeof(buf));
      if (len<=0) return;

      while (len) {
        rv = write(unsd, buf+offset, len);
        if (rv<=0) return;
        offset+=rv;
        len-=rv;
      }
    } else if (FD_ISSET(unsd, &rfds)) {
      offset = 0;
      len = read(unsd, buf, sizeof(buf));
      if (len<=0) return;

      while (len) {
        rv = write(insd, buf+offset, len);
        if (rv<=0) return;
        offset+=rv;
        len-=rv;
      }
    }
  }
}


int main(int argc, char **argv) {
  int mainsd, insd, unsd;
  struct sockaddr_in their_addr;
  socklen_t tp;
  char ipbuf[100];

  if (argc != 3 || atoi(argv[1])<=0 || atoi(argv[1])>=65536) {
    fprintf(stderr, "unix2inet-bridge (C) 2008 hcsw.org and Doug Hoyte\n");
    fprintf(stderr, "  Usage: unix2inet-bridge <port> <path to unix socket>\n");
    return -1;
  }

  mainsd = listen_inet(atoi(argv[1]));
  if (mainsd == -1) exit(-1);

  while(1) {
    tp = sizeof(struct sockaddr_in);

    insd = accept(mainsd, (struct sockaddr *)&their_addr, &tp);
    if (insd == -1) {
      fprintf(stderr, "Error accepting: %s\n", strerror(errno));
      exit(-1);
    }

    inet_ntop(AF_INET, &(((struct sockaddr_in *)&their_addr)->sin_addr), ipbuf, sizeof(ipbuf));

    #ifdef DEBUG
    printf("Bridging connection from %s to %s\n", ipbuf, argv[2]);
    #endif

    unsd = conn_unix(argv[2]);
    if (unsd == -1) exit(-1);

    if (fork() == 0) {
      proc_bridge(insd, unsd);
      #ifdef DEBUG
      printf("Killing connection from %s\n", ipbuf);
      #endif
      exit(0);
    }

    close(insd);
    close(unsd);
  }

}