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socks.c

/*    $OpenBSD: socks.c,v 1.17 2006/09/25 04:51:20 ray Exp $      */

/*
 * Copyright (c) 1999 Niklas Hallqvist.  All rights reserved.
 * Copyright (c) 2004, 2005 Damien Miller.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <err.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <resolv.h>
#include <readpassphrase.h>
#include "atomicio.h"

#define SOCKS_PORT      "1080"
#define HTTP_PROXY_PORT "3128"
#define HTTP_MAXHDRS    64
#define SOCKS_V5  5
#define SOCKS_V4  4
#define SOCKS_NOAUTH    0
#define SOCKS_NOMETHOD  0xff
#define SOCKS_CONNECT   1
#define SOCKS_IPV4      1
#define SOCKS_DOMAIN    3
#define SOCKS_IPV6      4

extern int b64_ntop(unsigned char const *, size_t, char *, size_t);

int   remote_connect(const char *, const char *, struct addrinfo);
int   socks_connect(const char *, const char *, struct addrinfo,
          const char *, const char *, struct addrinfo, int,
          const char *);

static int
decode_addrport(const char *h, const char *p, struct sockaddr *addr,
    socklen_t addrlen, int v4only, int numeric)
{
      int r;
      struct addrinfo hints, *res;

      bzero(&hints, sizeof(hints));
      hints.ai_family = v4only ? PF_INET : PF_UNSPEC;
      hints.ai_flags = numeric ? AI_NUMERICHOST : 0;
      hints.ai_socktype = SOCK_STREAM;
      r = getaddrinfo(h, p, &hints, &res);
      /* Don't fatal when attempting to convert a numeric address */
      if (r != 0) {
            if (!numeric) {
                  errx(1, "getaddrinfo(\"%.64s\", \"%.64s\"): %s", h, p,
                      gai_strerror(r));
            }
            return (-1);
      }
      if (addrlen < res->ai_addrlen) {
            freeaddrinfo(res);
            errx(1, "internal error: addrlen < res->ai_addrlen");
      }
      memcpy(addr, res->ai_addr, res->ai_addrlen);
      freeaddrinfo(res);
      return (0);
}

static int
proxy_read_line(int fd, char *buf, size_t bufsz)
{
      size_t off;

      for(off = 0;;) {
            if (off >= bufsz)
                  errx(1, "proxy read too long");
            if (atomicio(read, fd, buf + off, 1) != 1)
                  err(1, "proxy read");
            /* Skip CR */
            if (buf[off] == '\r')
                  continue;
            if (buf[off] == '\n') {
                  buf[off] = '\0';
                  break;
            }
            off++;
      }
      return (off);
}

static const char *
getproxypass(const char *proxyuser, const char *proxyhost)
{
      char prompt[512];
      static char pw[256];

      snprintf(prompt, sizeof(prompt), "Proxy password for %s@%s: ",
         proxyuser, proxyhost);
      if (readpassphrase(prompt, pw, sizeof(pw), RPP_REQUIRE_TTY) == NULL)
            errx(1, "Unable to read proxy passphrase");
      return (pw);
}

int
socks_connect(const char *host, const char *port,
    struct addrinfo hints __attribute__ ((__unused__)),
    const char *proxyhost, const char *proxyport, struct addrinfo proxyhints,
    int socksv, const char *proxyuser)
{
      int proxyfd, r, authretry = 0;
      size_t hlen, wlen;
      unsigned char buf[1024];
      size_t cnt;
      struct sockaddr_storage addr;
      struct sockaddr_in *in4 = (struct sockaddr_in *)&addr;
      struct sockaddr_in6 *in6 = (struct sockaddr_in6 *)&addr;
      in_port_t serverport;
      const char *proxypass = NULL;

      if (proxyport == NULL)
            proxyport = (socksv == -1) ? HTTP_PROXY_PORT : SOCKS_PORT;

      /* Abuse API to lookup port */
      if (decode_addrport("0.0.0.0", port, (struct sockaddr *)&addr,
          sizeof(addr), 1, 1) == -1)
            errx(1, "unknown port \"%.64s\"", port);
      serverport = in4->sin_port;

 again:
      if (authretry++ > 3)
            errx(1, "Too many authentication failures");

      proxyfd = remote_connect(proxyhost, proxyport, proxyhints);

      if (proxyfd < 0)
            return (-1);

      if (socksv == 5) {
            if (decode_addrport(host, port, (struct sockaddr *)&addr,
                sizeof(addr), 0, 1) == -1)
                  addr.ss_family = 0; /* used in switch below */

            /* Version 5, one method: no authentication */
            buf[0] = SOCKS_V5;
            buf[1] = 1;
            buf[2] = SOCKS_NOAUTH;
            cnt = atomicio(vwrite, proxyfd, buf, 3);
            if (cnt != 3)
                  err(1, "write failed (%d/3)", cnt);

            cnt = atomicio(read, proxyfd, buf, 2);
            if (cnt != 2)
                  err(1, "read failed (%d/3)", cnt);

            if (buf[1] == SOCKS_NOMETHOD)
                  errx(1, "authentication method negotiation failed");

            switch (addr.ss_family) {
            case 0:
                  /* Version 5, connect: domain name */

                  /* Max domain name length is 255 bytes */
                  hlen = strlen(host);
                  if (hlen > 255)
                        errx(1, "host name too long for SOCKS5");
                  buf[0] = SOCKS_V5;
                  buf[1] = SOCKS_CONNECT;
                  buf[2] = 0;
                  buf[3] = SOCKS_DOMAIN;
                  buf[4] = hlen;
                  memcpy(buf + 5, host, hlen);              
                  memcpy(buf + 5 + hlen, &serverport, sizeof serverport);
                  wlen = 7 + hlen;
                  break;
            case AF_INET:
                  /* Version 5, connect: IPv4 address */
                  buf[0] = SOCKS_V5;
                  buf[1] = SOCKS_CONNECT;
                  buf[2] = 0;
                  buf[3] = SOCKS_IPV4;
                  memcpy(buf + 4, &in4->sin_addr, sizeof in4->sin_addr);
                  memcpy(buf + 8, &in4->sin_port, sizeof in4->sin_port);
                  wlen = 10;
                  break;
            case AF_INET6:
                  /* Version 5, connect: IPv6 address */
                  buf[0] = SOCKS_V5;
                  buf[1] = SOCKS_CONNECT;
                  buf[2] = 0;
                  buf[3] = SOCKS_IPV6;
                  memcpy(buf + 4, &in6->sin6_addr, sizeof in6->sin6_addr);
                  memcpy(buf + 20, &in6->sin6_port,
                      sizeof in6->sin6_port);
                  wlen = 22;
                  break;
            default:
                  errx(1, "internal error: silly AF");
            }

            cnt = atomicio(vwrite, proxyfd, buf, wlen);
            if (cnt != wlen)
                  err(1, "write failed (%d/%d)", cnt, wlen);

            cnt = atomicio(read, proxyfd, buf, 10);
            if (cnt != 10)
                  err(1, "read failed (%d/10)", cnt);
            if (buf[1] != 0)
                  errx(1, "connection failed, SOCKS error %d", buf[1]);
      } else if (socksv == 4) {
            /* This will exit on lookup failure */
            decode_addrport(host, port, (struct sockaddr *)&addr,
                sizeof(addr), 1, 0);

            /* Version 4 */
            buf[0] = SOCKS_V4;
            buf[1] = SOCKS_CONNECT; /* connect */
            memcpy(buf + 2, &in4->sin_port, sizeof in4->sin_port);
            memcpy(buf + 4, &in4->sin_addr, sizeof in4->sin_addr);
            buf[8] = 0; /* empty username */
            wlen = 9;

            cnt = atomicio(vwrite, proxyfd, buf, wlen);
            if (cnt != wlen)
                  err(1, "write failed (%d/%d)", cnt, wlen);

            cnt = atomicio(read, proxyfd, buf, 8);
            if (cnt != 8)
                  err(1, "read failed (%d/8)", cnt);
            if (buf[1] != 90)
                  errx(1, "connection failed, SOCKS error %d", buf[1]);
      } else if (socksv == -1) {
            /* HTTP proxy CONNECT */

            /* Disallow bad chars in hostname */
            if (strcspn(host, "\r\n\t []:") != strlen(host))
                  errx(1, "Invalid hostname");

            /* Try to be sane about numeric IPv6 addresses */
            if (strchr(host, ':') != NULL) {
                  r = snprintf(buf, sizeof(buf),
                      "CONNECT [%s]:%d HTTP/1.0\r\n",
                      host, ntohs(serverport));
            } else {
                  r = snprintf(buf, sizeof(buf),
                      "CONNECT %s:%d HTTP/1.0\r\n",
                      host, ntohs(serverport));
            }
            if (r == -1 || (size_t)r >= sizeof(buf))
                  errx(1, "hostname too long");
            r = strlen(buf);

            cnt = atomicio(vwrite, proxyfd, buf, r);
            if (cnt != r)
                  err(1, "write failed (%d/%d)", cnt, r);

            if (authretry > 1) {
                  char resp[1024];

                  proxypass = getproxypass(proxyuser, proxyhost);
                  r = snprintf(buf, sizeof(buf), "%s:%s",
                      proxyuser, proxypass);
                  if (r == -1 || (size_t)r >= sizeof(buf) ||
                      b64_ntop(buf, strlen(buf), resp,
                      sizeof(resp)) == -1)
                        errx(1, "Proxy username/password too long");
                  r = snprintf(buf, sizeof(buf), "Proxy-Authorization: "
                      "Basic %s\r\n", resp);
                  if (r == -1 || (size_t)r >= sizeof(buf))
                        errx(1, "Proxy auth response too long");
                  r = strlen(buf);
                  if ((cnt = atomicio(vwrite, proxyfd, buf, r)) != r)
                        err(1, "write failed (%d/%d)", cnt, r);
            }

            /* Terminate headers */
            if ((r = atomicio(vwrite, proxyfd, "\r\n", 2)) != 2)
                  err(1, "write failed (2/%d)", r);

            /* Read status reply */
            proxy_read_line(proxyfd, buf, sizeof(buf));
            if (proxyuser != NULL &&
                strncmp(buf, "HTTP/1.0 407 ", 12) == 0) {
                  if (authretry > 1) {
                        fprintf(stderr, "Proxy authentication "
                            "failed\n");
                  }
                  close(proxyfd);
                  goto again;
            } else if (strncmp(buf, "HTTP/1.0 200 ", 12) != 0 &&
                strncmp(buf, "HTTP/1.1 200 ", 12) != 0)
                  errx(1, "Proxy error: \"%s\"", buf);

            /* Headers continue until we hit an empty line */
            for (r = 0; r < HTTP_MAXHDRS; r++) {
                  proxy_read_line(proxyfd, buf, sizeof(buf));
                  if (*buf == '\0')
                        break;
            }
            if (*buf != '\0')
                  errx(1, "Too many proxy headers received");
      } else
            errx(1, "Unknown proxy protocol %d", socksv);

      return (proxyfd);
}

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