tor-resolve.c

/* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson
 * Copyright (c) 2007-2021, The Tor Project, Inc.
 */
/* See LICENSE for licensing information */
 
#include "orconfig.h"
 
#include "lib/arch/bytes.h"
#include "lib/log/log.h"
#include "lib/malloc/malloc.h"
#include "lib/net/address.h"
#include "lib/net/resolve.h"
#include "lib/net/socket.h"
#include "lib/sandbox/sandbox.h"
#include "lib/string/util_string.h"
 
#include "lib/net/socks5_status.h"
#include "trunnel/socks5.h"
 
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
 
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h> /* Must be included before sys/stat.h for Ultrix */
#endif
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
 
#ifdef _WIN32
#include <winsock2.h>
#include <ws2tcpip.h>
#endif
 
#define RESPONSE_LEN_4 8
#define log_sock_error(act, _s)                                         \
  STMT_BEGIN                                                            \
    log_fn(LOG_ERR, LD_NET, "Error while %s: %s", act,                  \
    tor_socket_strerror(tor_socket_errno(_s)));                         \
  STMT_END
 
static void usage(void) ATTR_NORETURN;
 
/**
 * Set <b>out</b> to a pointer to newly allocated buffer containing
 * SOCKS4a RESOLVE request with <b>username</b> and <b>hostname</b>.
 * Return number of bytes in the buffer if succeeded or -1 if failed.
 */
static ssize_t
build_socks4a_resolve_request(uint8_t **out,
                              const char *username,
                              const char *hostname)
{
  tor_assert(out);
  tor_assert(username);
  tor_assert(hostname);
 
  const char *errmsg = NULL;
  uint8_t *output = NULL;
  socks4_client_request_t *rq = socks4_client_request_new();
 
  socks4_client_request_set_version(rq, 4);
  socks4_client_request_set_command(rq, CMD_RESOLVE);
  socks4_client_request_set_port(rq, 0);
  socks4_client_request_set_addr(rq, 0x00000001u);
  socks4_client_request_set_username(rq, username);
  socks4_client_request_set_socks4a_addr_hostname(rq, hostname);
 
  errmsg = socks4_client_request_check(rq);
  if (errmsg) {
    goto cleanup;
  }
 
  ssize_t encoded_len = socks4_client_request_encoded_len(rq);
  if (encoded_len <= 0) {
    errmsg = "socks4_client_request_encoded_len failed";
    goto cleanup;
  }
 
  output = tor_malloc(encoded_len);
  memset(output, 0, encoded_len);
 
  encoded_len = socks4_client_request_encode(output, encoded_len, rq);
  if (encoded_len <= 0) {
    errmsg = "socks4_client_request_encode failed";
    goto cleanup;
  }
 
  *out = output;
 
 cleanup:
  socks4_client_request_free(rq);
  if (errmsg) {
    log_err(LD_NET, "build_socks4a_resolve_request failed: %s", errmsg);
    *out = NULL;
    tor_free(output);
  }
  return errmsg ? -1 : encoded_len;
}
 
#define SOCKS5_ATYPE_HOSTNAME 0x03
#define SOCKS5_ATYPE_IPV4     0x01
#define SOCKS5_ATYPE_IPV6     0x04
 
/**
 * Set <b>out</b> to pointer to newly allocated buffer containing
 * SOCKS5 RESOLVE/RESOLVE_PTR request with given <b>hostname<b>.
 * Generate a reverse request if <b>reverse</b> is true.
 * Return the number of bytes in the buffer if succeeded or -1 if failed.
 */
static ssize_t
build_socks5_resolve_request(uint8_t **out,
                             const char *hostname,
                             int reverse)
{
  const char *errmsg = NULL;
  uint8_t *outbuf = NULL;
  int is_ip_address;
  tor_addr_t addr;
  size_t addrlen;
  int ipv6;
  is_ip_address = tor_addr_parse(&addr, hostname) != -1;
  if (!is_ip_address && reverse) {
    log_err(LD_GENERAL, "Tried to do a reverse lookup on a non-IP!");
    return -1;
  }
  ipv6 = reverse && tor_addr_family(&addr) == AF_INET6;
  addrlen = reverse ? (ipv6 ? 16 : 4) : 1 + strlen(hostname);
  if (addrlen > UINT8_MAX) {
    log_err(LD_GENERAL, "Hostname is too long!");
    return -1;
  }
 
  socks5_client_request_t *rq = socks5_client_request_new();
 
  socks5_client_request_set_version(rq, 5);
  /* RESOLVE_PTR or RESOLVE */
  socks5_client_request_set_command(rq, reverse ? CMD_RESOLVE_PTR :
                                                  CMD_RESOLVE);
  socks5_client_request_set_reserved(rq, 0);
 
  uint8_t atype = SOCKS5_ATYPE_HOSTNAME;
  if (reverse)
    atype = ipv6 ? SOCKS5_ATYPE_IPV6 : SOCKS5_ATYPE_IPV4;
 
  socks5_client_request_set_atype(rq, atype);
 
  switch (atype) {
    case SOCKS5_ATYPE_IPV4: {
      socks5_client_request_set_dest_addr_ipv4(rq,
                                        tor_addr_to_ipv4h(&addr));
    } break;
    case SOCKS5_ATYPE_IPV6: {
      uint8_t *ipv6_array =
        socks5_client_request_getarray_dest_addr_ipv6(rq);
 
      tor_assert(ipv6_array);
 
      memcpy(ipv6_array, tor_addr_to_in6_addr8(&addr), 16);
    } break;
 
    case SOCKS5_ATYPE_HOSTNAME: {
      domainname_t *dn = domainname_new();
      domainname_set_len(dn, addrlen - 1);
      domainname_setlen_name(dn, addrlen - 1);
      char *dn_buf = domainname_getarray_name(dn);
      memcpy(dn_buf, hostname, addrlen - 1);
 
      errmsg = domainname_check(dn);
 
      if (errmsg) {
        domainname_free(dn);
        goto cleanup;
      } else {
        socks5_client_request_set_dest_addr_domainname(rq, dn);
      }
    } break;
    default:
      tor_assert_unreached();
      break;
  }
 
  socks5_client_request_set_dest_port(rq, 0);
 
  errmsg = socks5_client_request_check(rq);
  if (errmsg) {
    goto cleanup;
  }
 
  ssize_t encoded_len = socks5_client_request_encoded_len(rq);
  if (encoded_len < 0) {
    errmsg = "Cannot predict encoded length";
    goto cleanup;
  }
 
  outbuf = tor_malloc(encoded_len);
  memset(outbuf, 0, encoded_len);
 
  encoded_len = socks5_client_request_encode(outbuf, encoded_len, rq);
  if (encoded_len < 0) {
    errmsg = "encoding failed";
    goto cleanup;
  }
 
  *out = outbuf;
 
 cleanup:
  socks5_client_request_free(rq);
  if (errmsg) {
    tor_free(outbuf);
    log_err(LD_NET, "build_socks5_resolve_request failed with error: %s",
            errmsg);
  }
 
  return errmsg ? -1 : encoded_len;
}
 
/** Set *<b>out</b> to a newly allocated SOCKS4a resolve request with
 * <b>username</b> and <b>hostname</b> as provided.  Return the number
 * of bytes in the request. */
static ssize_t
build_socks_resolve_request(uint8_t **out,
                            const char *username,
                            const char *hostname,
                            int reverse,
                            int version)
{
  tor_assert(out);
  tor_assert(username);
  tor_assert(hostname);
 
  tor_assert(version == 4 || version == 5);
 
  if (version == 4) {
    return build_socks4a_resolve_request(out, username, hostname);
  } else if (version == 5) {
    return build_socks5_resolve_request(out, hostname, reverse);
  }
 
  tor_assert_unreached();
  return -1;
}
 
static void
onion_hs_warning(const char *hostname)
{
  log_warn(LD_NET,
        "%s is a hidden service; those don't have IP addresses. "
        "You can use the AutomapHostsOnResolve option to have Tor return a "
        "fake address for hidden services.  Or you can have your "
        "application send the address to Tor directly; we recommend an "
        "application that uses SOCKS 5 with hostnames.",
           hostname);
}
 
static void
onion_exit_warning(const char *hostname)
{
  log_warn(LD_NET,
        "%s is a link pointing to an exit node; however, .exit domains"
        "have been long defunct and are not valid anymore.",
           hostname);
}
 
/** Given a <b>len</b>-byte SOCKS4a response in <b>response</b>, set
 * *<b>addr_out</b> to the address it contains (in host order).
 * Return 0 on success, -1 on error.
 */
static int
parse_socks4a_resolve_response(const char *hostname,
                               const char *response, size_t len,
                               tor_addr_t *addr_out)
{
  int result = 0;
  uint8_t status;
  tor_assert(response);
  tor_assert(addr_out);
 
  socks4_server_reply_t *reply;
 
  ssize_t parsed = socks4_server_reply_parse(&reply,
                                             (const uint8_t *)response,
                                             len);
 
  if (parsed == -1) {
    log_warn(LD_PROTOCOL, "Failed parsing SOCKS4a response");
    result = -1; goto cleanup;
  }
 
  if (parsed == -2) {
    log_warn(LD_PROTOCOL,"Truncated socks response.");
    result = -1; goto cleanup;
  }
 
  if (socks4_server_reply_get_version(reply) != 0) { /* version: 0 */
    log_warn(LD_PROTOCOL,"Nonzero version in socks response: bad format.");
    result = -1; goto cleanup;
  }
  if (socks4_server_reply_get_port(reply) != 0) { /* port: 0 */
    log_warn(LD_PROTOCOL,"Nonzero port in socks response: bad format.");
    result = -1; goto cleanup;
  }
  status = socks4_server_reply_get_status(reply);
  if (status != 90) {
    log_warn(LD_NET,"Got status response '%d': socks request failed.", status);
    if (!strcasecmpend(hostname, ".onion")) {
      onion_hs_warning(hostname);
      result = -1; goto cleanup;
    }
 
    if (!strcasecmpend(hostname, ".exit")) {
      onion_exit_warning(hostname);
      result = -1; goto cleanup;
    }
 
    result = -1; goto cleanup;
  }
 
  tor_addr_from_ipv4h(addr_out, socks4_server_reply_get_addr(reply));
 
 cleanup:
  socks4_server_reply_free(reply);
  return result;
}
 
/* It would be nice to let someone know what SOCKS5 issue a user may have */
static const char *
socks5_reason_to_string(char reason)
{
  switch (reason) {
    case SOCKS5_SUCCEEDED:
      return "succeeded";
    case SOCKS5_GENERAL_ERROR:
      return "general error";
    case SOCKS5_NOT_ALLOWED:
      return "not allowed";
    case SOCKS5_NET_UNREACHABLE:
      return "network is unreachable";
    case SOCKS5_HOST_UNREACHABLE:
      return "host is unreachable";
    case SOCKS5_CONNECTION_REFUSED:
      return "connection refused";
    case SOCKS5_TTL_EXPIRED:
      return "ttl expired";
    case SOCKS5_COMMAND_NOT_SUPPORTED:
      return "command not supported";
    case SOCKS5_ADDRESS_TYPE_NOT_SUPPORTED:
      return "address type not supported";
    default:
      return "unknown SOCKS5 code";
  }
}
 
/** Send a resolve request for <b>hostname</b> to the Tor listening on
 * <b>sockshost</b>:<b>socksport</b>.  Store the resulting IPv4
 * address (in host order) into *<b>result_addr</b>.
 */
static int
do_resolve(const char *hostname,
           const tor_addr_t *sockshost, uint16_t socksport,
           int reverse, int version,
           tor_addr_t *result_addr, char **result_hostname)
{
  int s = -1;
  struct sockaddr_storage ss;
  socklen_t socklen;
  uint8_t *req = NULL;
  ssize_t len = 0;
 
  tor_assert(hostname);
  tor_assert(result_addr);
  tor_assert(version == 4 || version == 5);
 
  tor_addr_make_unspec(result_addr);
  *result_hostname = NULL;
 
  s = tor_open_socket(PF_INET,SOCK_STREAM,IPPROTO_TCP);
  if (s<0) {
    log_sock_error("creating_socket", -1);
    return -1;
  }
 
  socklen = tor_addr_to_sockaddr(sockshost, socksport,
                                 (struct sockaddr *)&ss, sizeof(ss));
 
  if (connect(s, (struct sockaddr*)&ss, socklen)) {
    log_sock_error("connecting to SOCKS host", s);
    goto err;
  }
 
  if (version == 5) {
    socks5_client_version_t *v = socks5_client_version_new();
 
    socks5_client_version_set_version(v, 5);
    socks5_client_version_set_n_methods(v, 1);
    socks5_client_version_setlen_methods(v, 1);
    socks5_client_version_set_methods(v, 0, 0x00);
 
    tor_assert(!socks5_client_version_check(v));
    ssize_t encoded_len = socks5_client_version_encoded_len(v);
    tor_assert(encoded_len > 0);
 
    uint8_t *buf = tor_malloc(encoded_len);
    encoded_len = socks5_client_version_encode(buf, encoded_len, v);
    tor_assert(encoded_len > 0);
 
    socks5_client_version_free(v);
 
    if (write_all_to_socket(s, (const char *)buf,
                            encoded_len) != encoded_len) {
      log_err(LD_NET, "Error sending SOCKS5 method list.");
      tor_free(buf);
 
      goto err;
    }
 
    tor_free(buf);
 
    uint8_t method_buf[2];
 
    if (read_all_from_socket(s, (char *)method_buf, 2) != 2) {
      log_err(LD_NET, "Error reading SOCKS5 methods.");
      goto err;
    }
 
    socks5_server_method_t *m;
    ssize_t parsed = socks5_server_method_parse(&m, method_buf,
                                                sizeof(method_buf));
 
    if (parsed < 2) {
      log_err(LD_NET, "Failed to parse SOCKS5 method selection "
                      "message");
      socks5_server_method_free(m);
      goto err;
    }
 
    uint8_t method = socks5_server_method_get_method(m);
 
    socks5_server_method_free(m);
 
    if (method != 0x00) {
      log_err(LD_NET, "Unrecognized socks authentication method: %u",
              (unsigned)method);
      goto err;
    }
  }
 
  if ((len = build_socks_resolve_request(&req, "", hostname, reverse,
                                         version))<0) {
    log_err(LD_BUG,"Error generating SOCKS request");
    tor_assert(!req);
    goto err;
  }
  if (write_all_to_socket(s, (const char *)req, len) != len) {
    log_sock_error("sending SOCKS request", s);
    tor_free(req);
    goto err;
  }
  tor_free(req);
 
  if (version == 4) {
    char reply_buf[RESPONSE_LEN_4];
    if (read_all_from_socket(s, reply_buf, RESPONSE_LEN_4) != RESPONSE_LEN_4) {
      log_err(LD_NET, "Error reading SOCKS4 response.");
      goto err;
    }
    if (parse_socks4a_resolve_response(hostname,
                                       reply_buf, RESPONSE_LEN_4,
                                       result_addr)<0) {
      goto err;
    }
  } else {
    uint8_t reply_buf[512];
 
    len = read_all_from_socket(s, (char *)reply_buf,
                               sizeof(reply_buf));
 
    socks5_server_reply_t *reply;
 
    ssize_t parsed = socks5_server_reply_parse(&reply,
                                               reply_buf,
                                               len);
    if (parsed == -1) {
      log_err(LD_NET, "Failed parsing SOCKS5 response");
      goto err;
    }
 
    if (parsed == -2) {
      log_err(LD_NET, "Truncated SOCKS5 response");
      goto err;
    }
 
    /* Give a user some useful feedback about SOCKS5 errors */
    uint8_t reply_field = socks5_server_reply_get_reply(reply);
    if (reply_field != 0) {
      log_warn(LD_NET,"Got SOCKS5 status response '%u': %s",
               (unsigned)reply_field,
               socks5_reason_to_string(reply_field));
      if (reply_field == 4 && !strcasecmpend(hostname, ".onion")) {
        onion_hs_warning(hostname);
      }
 
      if (reply_field == 4 && !strcasecmpend(hostname, ".exit")) {
        onion_exit_warning(hostname);
      }
 
      socks5_server_reply_free(reply);
      goto err;
    }
 
    uint8_t atype = socks5_server_reply_get_atype(reply);
 
    if (atype == SOCKS5_ATYPE_IPV4) {
      /* IPv4 address */
      tor_addr_from_ipv4h(result_addr,
        socks5_server_reply_get_bind_addr_ipv4(reply));
    } else if (atype == SOCKS5_ATYPE_IPV6) {
      /* IPv6 address */
      tor_addr_from_ipv6_bytes(result_addr,
        socks5_server_reply_getarray_bind_addr_ipv6(reply));
    } else if (atype == SOCKS5_ATYPE_HOSTNAME) {
      /* Domain name */
      domainname_t *dn =
        socks5_server_reply_get_bind_addr_domainname(reply);
 
      *result_hostname = tor_strdup(domainname_getstr_name(dn));
    }
 
    socks5_server_reply_free(reply);
  }
 
  tor_close_socket(s);
  return 0;
 err:
  tor_close_socket(s);
  return -1;
}
 
/** Print a usage message and exit. */
static void
usage(void)
{
  puts("Syntax: tor-resolve [-4] [-5] [-v] [-x] [-p port] "
       "hostname [sockshost[:socksport]]");
  exit(1);
}
 
/** Entry point to tor-resolve */
int
main(int argc, char **argv)
{
  tor_addr_t sockshost;
  uint16_t socksport = 0, port_option = 0;
  int isSocks4 = 0, isVerbose = 0, isReverse = 0;
  char **arg;
  int n_args;
  tor_addr_t result;
  char *result_hostname = NULL;
 
  init_logging(1);
  sandbox_disable_getaddrinfo_cache();
 
  arg = &argv[1];
  n_args = argc-1;
 
  if (!n_args)
    usage();
 
  if (!strcmp(arg[0],"--version")) {
    printf("Tor version %s.\n",VERSION);
    return 0;
  }
  while (n_args && *arg[0] == '-') {
    if (!strcmp("-v", arg[0]))
      isVerbose = 1;
    else if (!strcmp("-4", arg[0]))
      isSocks4 = 1;
    else if (!strcmp("-5", arg[0]))
      isSocks4 = 0;
    else if (!strcmp("-x", arg[0]))
      isReverse = 1;
    else if (!strcmp("-p", arg[0])) {
      int p;
      if (n_args < 2) {
        fprintf(stderr, "No arguments given to -p\n");
        usage();
      }
      p = atoi(arg[1]);
      if (p<1 || p > 65535) {
        fprintf(stderr, "-p requires a number between 1 and 65535\n");
        usage();
      }
      port_option = (uint16_t) p;
      ++arg; /* skip the port */
      --n_args;
    } else {
      fprintf(stderr, "Unrecognized flag '%s'\n", arg[0]);
      usage();
    }
    ++arg;
    --n_args;
  }
 
  if (isSocks4 && isReverse) {
    fprintf(stderr, "Reverse lookups not supported with SOCKS4a\n");
    usage();
  }
 
  log_severity_list_t *severities =
    tor_malloc_zero(sizeof(log_severity_list_t));
  if (isVerbose)
    set_log_severity_config(LOG_DEBUG, LOG_ERR, severities);
  else
    set_log_severity_config(LOG_WARN, LOG_ERR, severities);
  add_stream_log(severities, "<stderr>", fileno(stderr));
  tor_free(severities);
 
  if (n_args == 1) {
    log_debug(LD_CONFIG, "defaulting to localhost");
    tor_addr_from_ipv4h(&sockshost, 0x7f000001u); /* localhost */
    if (port_option) {
      log_debug(LD_CONFIG, "Using port %d", (int)port_option);
      socksport = port_option;
    } else {
      log_debug(LD_CONFIG, "defaulting to port 9050");
      socksport = 9050; /* 9050 */
    }
  } else if (n_args == 2) {
    if (tor_addr_port_lookup(arg[1], &sockshost, &socksport)<0) {
      fprintf(stderr, "Couldn't parse/resolve address %s", arg[1]);
      return 1;
    }
    if (socksport && port_option && socksport != port_option) {
      log_warn(LD_CONFIG, "Conflicting ports; using %d, not %d",
               (int)socksport, (int)port_option);
    } else if (port_option) {
      socksport = port_option;
    } else if (!socksport) {
      log_debug(LD_CONFIG, "defaulting to port 9050");
      socksport = 9050;
    }
  } else {
    usage();
  }
 
  if (network_init()<0) {
    log_err(LD_BUG,"Error initializing network; exiting.");
    return 1;
  }
 
  if (do_resolve(arg[0], &sockshost, socksport, isReverse,
                 isSocks4 ? 4 : 5, &result,
                 &result_hostname))
    return 1;
 
  if (result_hostname) {
    printf("%s\n", result_hostname);
  } else {
    printf("%s\n", fmt_addr(&result));
  }
  return 0;
}