inspectsocks.c

/*
 * INSPECTSOCKS - Part of the tsocks package
 * This utility can be used to determine the protocol
 * level of a SOCKS server.
 *
 * Copyright (C) 2000 Shaun Clowes
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/* Global configuration variables */
char *progname = "inspectsocks";	   /* Name for error msgs      */
int defaultport	= 1080;			   /* Default SOCKS port       */

/* Header Files */
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <string.h>
#include <strings.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#include <common.h>

int send_request(struct sockaddr_in *server, void *req,
	int reqlen, void *rep, int replen);

int main(int argc, char *argv[]) {
    char *usage = "Usage: <socks server name/ip> [portno]";
    char req[9];
    char resp[100];
    unsigned short int portno = defaultport;
    int ver = 0;
    int read_bytes;
    struct sockaddr_in server;

    if ((argc < 2) || (argc > 3)) {
	show_msg(MSGERR, "Invalid number of arguments\n");
	show_msg(MSGERR, "%s\n", usage);
	exit(1);
    }

    switch (argc) {
	case 3:
	    portno = (unsigned short int)
		strtol(argv[2], (char **) 0, 10);
	    if ((portno == 0) || (errno == EINVAL)) {
		show_msg(MSGERR, "%s\n", usage);
		exit(1);
	    }
	case 2:
	    if ((server.sin_addr.s_addr = resolve_ip(argv[1], 1,HOSTNAMES))
		    ==  -1) {
		show_msg(MSGERR, "Invalid IP/host specified (%s)\n", argv[1]);
		show_msg(MSGERR, "%s\n", usage);
		exit(1);
	    }
    }

    server.sin_family = AF_INET; /* host byte order */
    server.sin_port = htons(portno);     /* short, network byte order */
    bzero(&(server.sin_zero), 8);/* zero the rest of the struct */

    /* Now, we send a SOCKS V5 request which happens to be */
    /* the same size as the smallest possible SOCKS V4     */
    /* request. In this packet we specify we have 7 auth   */
    /* methods but specify them all as NO AUTH.            */
    bzero(req, sizeof(req));
    req[0] = '\x05';
    req[1] = '\x07';
    read_bytes = send_request(&server, req,
	    sizeof(req), resp, sizeof(resp));
    if (read_bytes > 0) {
	if ((int) resp[0] == 0) {
	    ver = 4;
	} else if ((int) resp[0] == 5) {
	    ver = 5;
	}
	if (ver != 0) {
	    printf("Reply indicates server is a version "
		    "%d socks server\n", ver);
	} else {
	    show_msg(MSGERR, "Invalid SOCKS version reply (%d), "
		    "probably not a socks server\n",
		    ver);
	}
	exit(0);
    }

    /* Hmmm.... disconnected so try a V4 request */
    printf("Server disconnected V5 request, trying V4\n");
    req[0] = '\x04';
    req[1] = '\x01';
    read_bytes = send_request(&server, req,
	    sizeof(req), resp, sizeof(resp));
    if (read_bytes > 0) {
	if ((int) resp[0] == 0) {
	    ver = 4;
	}
	if (ver == 4) {
	    printf("Reply indicates server is a version "
		    "4 socks server\n");
	} else {
	    show_msg(MSGERR, "Invalid SOCKS version reply (%d), "
		    "probably not a socks server\n",
		    (int) resp[0]);
	}
	exit(0);
    } else {
	show_msg(MSGERR, "Server disconnected, probably not a "
		"socks server\n");
    }

    return 0;
}

int send_request(struct sockaddr_in *server, void *req,
	int reqlen, void *rep, int replen) {
    int sock;
    int rc;

    if ((sock = socket(server->sin_family, SOCK_STREAM, 0)) < 0)
    {
	show_msg(MSGERR, "Could not create socket (%s)\n",
		strerror(errno));
	exit(1);
    }

    if (connect(sock, (struct sockaddr *) server,
		sizeof(struct sockaddr_in)) != -1) {
    } else {
	show_msg(MSGERR, "Connect failed! (%s)\n",
		strerror(errno));
	exit(1);
    }

    if (send(sock, (void *) req, reqlen,0) < 0) {
	show_msg(MSGERR, "Could not send to server (%s)\n",
		strerror(errno));
	exit(1);
    }

    /* Now wait for reply */
    if ((rc = recv(sock, (void *) rep, replen, 0)) < 0) {
	show_msg(MSGERR, "Could not read from server\n",
		strerror(errno));
	exit(1);
    }

    close(sock);

    return rc;

}

/*
 * vim:sts=4:sw=4:tw=80
 */