path: root/contrib/libs/curl/lib/socks.c

/*************************************************************************** 
 *                                  _   _ ____  _ 
 *  Project                     ___| | | |  _ \| | 
 *                             / __| | | | |_) | | 
 *                            | (__| |_| |  _ <| |___ 
 *                             \___|\___/|_| \_\_____| 
 * 
 * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
 * 
 * This software is licensed as described in the file COPYING, which 
 * you should have received as part of this distribution. The terms 
 * are also available at https://curl.se/docs/copyright.html.
 * 
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell 
 * copies of the Software, and permit persons to whom the Software is 
 * furnished to do so, under the terms of the COPYING file. 
 * 
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY 
 * KIND, either express or implied. 
 * 
 ***************************************************************************/ 
 
#include "curl_setup.h" 
 
#if !defined(CURL_DISABLE_PROXY) 
 
#ifdef HAVE_NETINET_IN_H 
#include <netinet/in.h> 
#endif 
#ifdef HAVE_ARPA_INET_H 
#include <arpa/inet.h> 
#endif 
 
#include "urldata.h" 
#include "sendf.h" 
#include "select.h" 
#include "connect.h" 
#include "timeval.h" 
#include "socks.h" 
#include "multiif.h" /* for getsock macros */
 
/* The last 3 #include files should be in this order */
#include "curl_printf.h"
#include "curl_memory.h"
#include "memdebug.h" 
 
#if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
/* 
 * Helper read-from-socket functions. Does the same as Curl_read() but it 
 * blocks until all bytes amount of buffersize will be read. No more, no less. 
 * 
 * This is STUPID BLOCKING behavior. Only used by the SOCKS GSSAPI functions.
 */ 
int Curl_blockread_all(struct connectdata *conn, /* connection data */ 
                       curl_socket_t sockfd,     /* read from this socket */ 
                       char *buf,                /* store read data here */ 
                       ssize_t buffersize,       /* max amount to read */ 
                       ssize_t *n)               /* amount bytes read */ 
{ 
  ssize_t nread = 0;
  ssize_t allread = 0; 
  int result; 
  *n = 0; 
  for(;;) { 
    timediff_t timeout_ms = Curl_timeleft(conn->data, NULL, TRUE);
    if(timeout_ms < 0) {
      /* we already got the timeout */ 
      result = CURLE_OPERATION_TIMEDOUT; 
      break; 
    } 
    if(!timeout_ms)
      timeout_ms = TIMEDIFF_T_MAX;
    if(SOCKET_READABLE(sockfd, timeout_ms) <= 0) {
      result = ~CURLE_OK; 
      break; 
    } 
    result = Curl_read_plain(sockfd, buf, buffersize, &nread); 
    if(CURLE_AGAIN == result) 
      continue; 
    if(result)
      break; 
 
    if(buffersize == nread) { 
      allread += nread; 
      *n = allread; 
      result = CURLE_OK; 
      break; 
    } 
    if(!nread) { 
      result = ~CURLE_OK; 
      break; 
    } 
 
    buffersize -= nread; 
    buf += nread; 
    allread += nread; 
  } 
  return result; 
} 
#endif
 
#ifndef DEBUGBUILD
#define sxstate(x,y) socksstate(x,y)
#else
#define sxstate(x,y) socksstate(x,y, __LINE__)
#endif


/* always use this function to change state, to make debugging easier */
static void socksstate(struct connectdata *conn,
                       enum connect_t state
#ifdef DEBUGBUILD
                       , int lineno
#endif
)
{
  enum connect_t oldstate = conn->cnnct.state;
#if defined(DEBUGBUILD) && !defined(CURL_DISABLE_VERBOSE_STRINGS)
  /* synced with the state list in urldata.h */
  static const char * const statename[] = {
    "INIT",
    "SOCKS_INIT",
    "SOCKS_SEND",
    "SOCKS_READ_INIT",
    "SOCKS_READ",
    "GSSAPI_INIT",
    "AUTH_INIT",
    "AUTH_SEND",
    "AUTH_READ",
    "REQ_INIT",
    "RESOLVING",
    "RESOLVED",
    "RESOLVE_REMOTE",
    "REQ_SEND",
    "REQ_SENDING",
    "REQ_READ",
    "REQ_READ_MORE",
    "DONE"
  };
#endif

  if(oldstate == state)
    /* don't bother when the new state is the same as the old state */
    return;

  conn->cnnct.state = state;

#if defined(DEBUGBUILD) && !defined(CURL_DISABLE_VERBOSE_STRINGS)
  infof(conn->data,
        "SXSTATE: %s => %s conn %p; line %d\n",
        statename[oldstate], statename[conn->cnnct.state], conn,
        lineno);
#endif
}

int Curl_SOCKS_getsock(struct connectdata *conn, curl_socket_t *sock,
                       int sockindex)
{
  int rc = 0;
  sock[0] = conn->sock[sockindex];
  switch(conn->cnnct.state) {
  case CONNECT_RESOLVING:
  case CONNECT_SOCKS_READ:
  case CONNECT_AUTH_READ:
  case CONNECT_REQ_READ:
  case CONNECT_REQ_READ_MORE:
    rc = GETSOCK_READSOCK(0);
    break;
  default:
    rc = GETSOCK_WRITESOCK(0);
    break;
  }
  return rc;
}

/* 
* This function logs in to a SOCKS4 proxy and sends the specifics to the final 
* destination server. 
* 
* Reference : 
*   https://www.openssh.com/txt/socks4.protocol
* 
* Note : 
*   Set protocol4a=true for  "SOCKS 4A (Simple Extension to SOCKS 4 Protocol)" 
*   Nonsupport "Identification Protocol (RFC1413)" 
*/ 
CURLproxycode Curl_SOCKS4(const char *proxy_user,
                          const char *hostname,
                          int remote_port,
                          int sockindex,
                          struct connectdata *conn,
                          bool *done)
{ 
  const bool protocol4a =
    (conn->socks_proxy.proxytype == CURLPROXY_SOCKS4A) ? TRUE : FALSE;
  unsigned char *socksreq = &conn->cnnct.socksreq[0];
  CURLcode result;
  curl_socket_t sockfd = conn->sock[sockindex];
  struct Curl_easy *data = conn->data;
  struct connstate *sx = &conn->cnnct;
  struct Curl_dns_entry *dns = NULL;
  ssize_t actualread;
  ssize_t written;
 
  if(!SOCKS_STATE(sx->state) && !*done)
    sxstate(conn, CONNECT_SOCKS_INIT);
 
  switch(sx->state) {
  case CONNECT_SOCKS_INIT:
    /* SOCKS4 can only do IPv4, insist! */
    conn->ip_version = CURL_IPRESOLVE_V4;
    if(conn->bits.httpproxy)
      infof(conn->data, "SOCKS4%s: connecting to HTTP proxy %s port %d\n",
            protocol4a ? "a" : "", hostname, remote_port);
 
    infof(data, "SOCKS4 communication to %s:%d\n", hostname, remote_port);

    /*
     * Compose socks4 request
     *
     * Request format
     *
     *     +----+----+----+----+----+----+----+----+----+----+....+----+
     *     | VN | CD | DSTPORT |      DSTIP        | USERID       |NULL|
     *     +----+----+----+----+----+----+----+----+----+----+....+----+
     * # of bytes:  1    1      2              4           variable       1
     */

    socksreq[0] = 4; /* version (SOCKS4) */
    socksreq[1] = 1; /* connect */
    socksreq[2] = (unsigned char)((remote_port >> 8) & 0xff); /* PORT MSB */
    socksreq[3] = (unsigned char)(remote_port & 0xff);        /* PORT LSB */
 
    /* DNS resolve only for SOCKS4, not SOCKS4a */
    if(!protocol4a) {
      enum resolve_t rc =
        Curl_resolv(conn, hostname, remote_port, FALSE, &dns);
 
      if(rc == CURLRESOLV_ERROR)
        return CURLPX_RESOLVE_HOST;
      else if(rc == CURLRESOLV_PENDING) {
        sxstate(conn, CONNECT_RESOLVING);
        infof(data, "SOCKS4 non-blocking resolve of %s\n", hostname);
        return CURLPX_OK;
      }
      sxstate(conn, CONNECT_RESOLVED);
      goto CONNECT_RESOLVED;
    }
 
    /* socks4a doesn't resolve anything locally */
    sxstate(conn, CONNECT_REQ_INIT);
    goto CONNECT_REQ_INIT;
 
  case CONNECT_RESOLVING:
    /* check if we have the name resolved by now */
    dns = Curl_fetch_addr(conn, hostname, (int)conn->port);
 
    if(dns) {
#ifdef CURLRES_ASYNCH
      conn->async.dns = dns;
      conn->async.done = TRUE;
#endif
      infof(data, "Hostname '%s' was found\n", hostname);
      sxstate(conn, CONNECT_RESOLVED);
    }
    else {
      result = Curl_resolv_check(data->conn, &dns);
      if(!dns) {
        if(result)
          return CURLPX_RESOLVE_HOST;
        return CURLPX_OK;
      }
    }
    /* FALLTHROUGH */
  CONNECT_RESOLVED:
  case CONNECT_RESOLVED: {
    struct Curl_addrinfo *hp = NULL;
    char buf[64];
    /* 
     * We cannot use 'hostent' as a struct that Curl_resolv() returns.  It 
     * returns a Curl_addrinfo pointer that may not always look the same. 
     */ 
    if(dns) 
      hp = dns->addr;
    if(hp) { 
      Curl_printable_address(hp, buf, sizeof(buf)); 
 
      if(hp->ai_family == AF_INET) {
        struct sockaddr_in *saddr_in;

        saddr_in = (struct sockaddr_in *)(void *)hp->ai_addr;
        socksreq[4] = ((unsigned char *)&saddr_in->sin_addr.s_addr)[0];
        socksreq[5] = ((unsigned char *)&saddr_in->sin_addr.s_addr)[1];
        socksreq[6] = ((unsigned char *)&saddr_in->sin_addr.s_addr)[2];
        socksreq[7] = ((unsigned char *)&saddr_in->sin_addr.s_addr)[3];

        infof(data, "SOCKS4 connect to IPv4 %s (locally resolved)\n", buf);
      } 
      else {
        hp = NULL; /* fail! */ 
        failf(data, "SOCKS4 connection to %s not supported\n", buf);
      }

      Curl_resolv_unlock(data, dns); /* not used anymore from now on */ 
    } 
    if(!hp) { 
      failf(data, "Failed to resolve \"%s\" for SOCKS4 connect.", 
            hostname); 
      return CURLPX_RESOLVE_HOST;
    } 
  } 
    /* FALLTHROUGH */
  CONNECT_REQ_INIT:
  case CONNECT_REQ_INIT:
    /*
     * This is currently not supporting "Identification Protocol (RFC1413)".
     */
    socksreq[8] = 0; /* ensure empty userid is NUL-terminated */
    if(proxy_user) {
      size_t plen = strlen(proxy_user);
      if(plen >= sizeof(sx->socksreq) - 8) {
        failf(data, "Too long SOCKS proxy user name, can't use!\n");
        return CURLPX_LONG_USER;
      }
      /* copy the proxy name WITH trailing zero */
      memcpy(socksreq + 8, proxy_user, plen + 1);
    } 
 
    /*
     * Make connection
     */
    {
      size_t packetsize = 9 +
        strlen((char *)socksreq + 8); /* size including NUL */
 
      /* If SOCKS4a, set special invalid IP address 0.0.0.x */
      if(protocol4a) {
        size_t hostnamelen = 0;
        socksreq[4] = 0;
        socksreq[5] = 0;
        socksreq[6] = 0;
        socksreq[7] = 1;
        /* append hostname */
        hostnamelen = strlen(hostname) + 1; /* length including NUL */
        if(hostnamelen <= 255)
          strcpy((char *)socksreq + packetsize, hostname);
        else {
          failf(data, "SOCKS4: too long host name");
          return CURLPX_LONG_HOSTNAME;
        }
        packetsize += hostnamelen;
      }
      sx->outp = socksreq;
      sx->outstanding = packetsize;
      sxstate(conn, CONNECT_REQ_SENDING);
    } 
    /* FALLTHROUGH */
  case CONNECT_REQ_SENDING:
    /* Send request */ 
    result = Curl_write_plain(conn, sockfd, (char *)sx->outp,
                              sx->outstanding, &written);
    if(result && (CURLE_AGAIN != result)) {
      failf(data, "Failed to send SOCKS4 connect request."); 
      return CURLPX_SEND_CONNECT;
    } 
    if(written != sx->outstanding) {
      /* not done, remain in state */
      sx->outstanding -= written;
      sx->outp += written;
      return CURLPX_OK;
    } 
 
    /* done sending! */
    sx->outstanding = 8; /* receive data size */
    sx->outp = socksreq;
    sxstate(conn, CONNECT_SOCKS_READ);
 
    /* FALLTHROUGH */
  case CONNECT_SOCKS_READ:
    /* Receive response */ 
    result = Curl_read_plain(sockfd, (char *)sx->outp,
                             sx->outstanding, &actualread);
    if(result && (CURLE_AGAIN != result)) {
      failf(data, "SOCKS4: Failed receiving connect request ack: %s",
            curl_easy_strerror(result));
      return CURLPX_RECV_CONNECT;
    } 
    else if(!result && !actualread) {
      /* connection closed */
      failf(data, "connection to proxy closed");
      return CURLPX_CLOSED;
    }
    else if(actualread != sx->outstanding) {
      /* remain in reading state */
      sx->outstanding -= actualread;
      sx->outp += actualread;
      return CURLPX_OK;
    }
    sxstate(conn, CONNECT_DONE);
    break;
  default: /* lots of unused states in SOCKS4 */
    break;
  }
 
  /*
   * Response format
   *
   *     +----+----+----+----+----+----+----+----+
   *     | VN | CD | DSTPORT |      DSTIP        |
   *     +----+----+----+----+----+----+----+----+
   * # of bytes:  1    1      2              4
   *
   * VN is the version of the reply code and should be 0. CD is the result
   * code with one of the following values:
   *
   * 90: request granted
   * 91: request rejected or failed
   * 92: request rejected because SOCKS server cannot connect to
   *     identd on the client
   * 93: request rejected because the client program and identd
   *     report different user-ids
   */
 
  /* wrong version ? */
  if(socksreq[0] != 0) {
    failf(data,
          "SOCKS4 reply has wrong version, version should be 0.");
    return CURLPX_BAD_VERSION;
  }
 
  /* Result */
  switch(socksreq[1]) {
  case 90:
    infof(data, "SOCKS4%s request granted.\n", protocol4a?"a":"");
    break;
  case 91:
    failf(data,
          "Can't complete SOCKS4 connection to %d.%d.%d.%d:%d. (%d)"
          ", request rejected or failed.",
          (unsigned char)socksreq[4], (unsigned char)socksreq[5],
          (unsigned char)socksreq[6], (unsigned char)socksreq[7],
          (((unsigned char)socksreq[2] << 8) | (unsigned char)socksreq[3]),
          (unsigned char)socksreq[1]);
    return CURLPX_REQUEST_FAILED;
  case 92:
    failf(data,
          "Can't complete SOCKS4 connection to %d.%d.%d.%d:%d. (%d)"
          ", request rejected because SOCKS server cannot connect to "
          "identd on the client.",
          (unsigned char)socksreq[4], (unsigned char)socksreq[5],
          (unsigned char)socksreq[6], (unsigned char)socksreq[7],
          (((unsigned char)socksreq[2] << 8) | (unsigned char)socksreq[3]),
          (unsigned char)socksreq[1]);
    return CURLPX_IDENTD;
  case 93:
    failf(data,
          "Can't complete SOCKS4 connection to %d.%d.%d.%d:%d. (%d)"
          ", request rejected because the client program and identd "
          "report different user-ids.",
          (unsigned char)socksreq[4], (unsigned char)socksreq[5],
          (unsigned char)socksreq[6], (unsigned char)socksreq[7],
          (((unsigned char)socksreq[2] << 8) | (unsigned char)socksreq[3]),
          (unsigned char)socksreq[1]);
    return CURLPX_IDENTD_DIFFER;
  default:
    failf(data,
          "Can't complete SOCKS4 connection to %d.%d.%d.%d:%d. (%d)"
          ", Unknown.",
          (unsigned char)socksreq[4], (unsigned char)socksreq[5],
          (unsigned char)socksreq[6], (unsigned char)socksreq[7],
          (((unsigned char)socksreq[2] << 8) | (unsigned char)socksreq[3]),
          (unsigned char)socksreq[1]);
    return CURLPX_UNKNOWN_FAIL;
  } 
 
  *done = TRUE;
  return CURLPX_OK; /* Proxy was successful! */
} 
 
/* 
 * This function logs in to a SOCKS5 proxy and sends the specifics to the final 
 * destination server. 
 */ 
CURLproxycode Curl_SOCKS5(const char *proxy_user,
                          const char *proxy_password,
                          const char *hostname,
                          int remote_port,
                          int sockindex,
                          struct connectdata *conn,
                          bool *done)
{ 
  /* 
    According to the RFC1928, section "6.  Replies". This is what a SOCK5 
    replies: 
 
        +----+-----+-------+------+----------+----------+ 
        |VER | REP |  RSV  | ATYP | BND.ADDR | BND.PORT | 
        +----+-----+-------+------+----------+----------+ 
        | 1  |  1  | X'00' |  1   | Variable |    2     | 
        +----+-----+-------+------+----------+----------+ 
 
    Where: 
 
    o  VER    protocol version: X'05' 
    o  REP    Reply field: 
    o  X'00' succeeded 
  */ 
  unsigned char *socksreq = &conn->cnnct.socksreq[0];
  char dest[256] = "unknown";  /* printable hostname:port */
  int idx;
  ssize_t actualread; 
  ssize_t written; 
  CURLcode result;
  curl_socket_t sockfd = conn->sock[sockindex];
  struct Curl_easy *data = conn->data;
  bool socks5_resolve_local =
    (conn->socks_proxy.proxytype == CURLPROXY_SOCKS5) ? TRUE : FALSE;
  const size_t hostname_len = strlen(hostname); 
  ssize_t len = 0; 
  const unsigned long auth = data->set.socks5auth;
  bool allow_gssapi = FALSE;
  struct connstate *sx = &conn->cnnct;
  struct Curl_dns_entry *dns = NULL;
 
  if(!SOCKS_STATE(sx->state) && !*done)
    sxstate(conn, CONNECT_SOCKS_INIT);

  switch(sx->state) {
  case CONNECT_SOCKS_INIT:
    if(conn->bits.httpproxy)
      infof(conn->data, "SOCKS5: connecting to HTTP proxy %s port %d\n",
            hostname, remote_port);
 
    /* RFC1928 chapter 5 specifies max 255 chars for domain name in packet */
    if(!socks5_resolve_local && hostname_len > 255) {
      infof(conn->data, "SOCKS5: server resolving disabled for hostnames of "
            "length > 255 [actual len=%zu]\n", hostname_len);
      socks5_resolve_local = TRUE;
    }
 
    if(auth & ~(CURLAUTH_BASIC | CURLAUTH_GSSAPI))
      infof(conn->data,
            "warning: unsupported value passed to CURLOPT_SOCKS5_AUTH: %lu\n",
            auth);
    if(!(auth & CURLAUTH_BASIC))
      /* disable username/password auth */
      proxy_user = NULL;
#if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI) 
    if(auth & CURLAUTH_GSSAPI)
      allow_gssapi = TRUE;
#endif 
 
    idx = 0;
    socksreq[idx++] = 5;   /* version */
    idx++;                 /* number of authentication methods */
    socksreq[idx++] = 0;   /* no authentication */
    if(allow_gssapi)
      socksreq[idx++] = 1; /* GSS-API */
    if(proxy_user)
      socksreq[idx++] = 2; /* username/password */
    /* write the number of authentication methods */
    socksreq[1] = (unsigned char) (idx - 2);
 
    result = Curl_write_plain(conn, sockfd, (char *)socksreq, idx, &written);
    if(result && (CURLE_AGAIN != result)) {
      failf(data, "Unable to send initial SOCKS5 request.");
      return CURLPX_SEND_CONNECT;
    }
    if(written != idx) {
      sxstate(conn, CONNECT_SOCKS_SEND);
      sx->outstanding = idx - written;
      sx->outp = &socksreq[written];
      return CURLPX_OK;
    }
    sxstate(conn, CONNECT_SOCKS_READ);
    goto CONNECT_SOCKS_READ_INIT;
  case CONNECT_SOCKS_SEND:
    result = Curl_write_plain(conn, sockfd, (char *)sx->outp,
                              sx->outstanding, &written);
    if(result && (CURLE_AGAIN != result)) {
      failf(data, "Unable to send initial SOCKS5 request.");
      return CURLPX_SEND_CONNECT;
    }
    if(written != sx->outstanding) {
      /* not done, remain in state */
      sx->outstanding -= written;
      sx->outp += written;
      return CURLPX_OK;
    }
    /* FALLTHROUGH */
  CONNECT_SOCKS_READ_INIT:
  case CONNECT_SOCKS_READ_INIT:
    sx->outstanding = 2; /* expect two bytes */
    sx->outp = socksreq; /* store it here */
    /* FALLTHROUGH */
  case CONNECT_SOCKS_READ:
    result = Curl_read_plain(sockfd, (char *)sx->outp,
                             sx->outstanding, &actualread);
    if(result && (CURLE_AGAIN != result)) {
      failf(data, "Unable to receive initial SOCKS5 response.");
      return CURLPX_RECV_CONNECT;
    }
    else if(!result && !actualread) {
      /* connection closed */
      failf(data, "Connection to proxy closed");
      return CURLPX_CLOSED;
    }
    else if(actualread != sx->outstanding) {
      /* remain in reading state */
      sx->outstanding -= actualread;
      sx->outp += actualread;
      return CURLPX_OK;
    }
    else if(socksreq[0] != 5) {
      failf(data, "Received invalid version in initial SOCKS5 response.");
      return CURLPX_BAD_VERSION;
    }
    else if(socksreq[1] == 0) {
      /* DONE! No authentication needed. Send request. */
      sxstate(conn, CONNECT_REQ_INIT);
      goto CONNECT_REQ_INIT;
    }
    else if(socksreq[1] == 2) {
      /* regular name + password authentication */
      sxstate(conn, CONNECT_AUTH_INIT);
      goto CONNECT_AUTH_INIT;
    }
#if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI) 
    else if(allow_gssapi && (socksreq[1] == 1)) {
      sxstate(conn, CONNECT_GSSAPI_INIT);
      result = Curl_SOCKS5_gssapi_negotiate(sockindex, conn);
      if(result) {
        failf(data, "Unable to negotiate SOCKS5 GSS-API context.");
        return CURLPX_GSSAPI;
      }
    } 
#endif 
    else {
      /* error */
      if(!allow_gssapi && (socksreq[1] == 1)) {
        failf(data,
              "SOCKS5 GSSAPI per-message authentication is not supported.");
        return CURLPX_GSSAPI_PERMSG;
      }
      else if(socksreq[1] == 255) {
        failf(data, "No authentication method was acceptable.");
        return CURLPX_NO_AUTH;
      }
    }
    failf(data,
          "Undocumented SOCKS5 mode attempted to be used by server.");
    return CURLPX_UNKNOWN_MODE;
#if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
  case CONNECT_GSSAPI_INIT:
    /* GSSAPI stuff done non-blocking */
    break;
#endif

  default: /* do nothing! */
    break;

  CONNECT_AUTH_INIT:
  case CONNECT_AUTH_INIT: {
    /* Needs user name and password */ 
    size_t proxy_user_len, proxy_password_len;
    if(proxy_user && proxy_password) {
      proxy_user_len = strlen(proxy_user);
      proxy_password_len = strlen(proxy_password); 
    } 
    else { 
      proxy_user_len = 0;
      proxy_password_len = 0; 
    } 
 
    /*   username/password request looks like 
     * +----+------+----------+------+----------+ 
     * |VER | ULEN |  UNAME   | PLEN |  PASSWD  | 
     * +----+------+----------+------+----------+ 
     * | 1  |  1   | 1 to 255 |  1   | 1 to 255 | 
     * +----+------+----------+------+----------+ 
     */ 
    len = 0; 
    socksreq[len++] = 1;    /* username/pw subnegotiation version */ 
    socksreq[len++] = (unsigned char) proxy_user_len;
    if(proxy_user && proxy_user_len) {
      /* the length must fit in a single byte */
      if(proxy_user_len >= 255) {
        failf(data, "Excessive user name length for proxy auth");
        return CURLPX_LONG_USER;
      }
      memcpy(socksreq + len, proxy_user, proxy_user_len);
    }
    len += proxy_user_len;
    socksreq[len++] = (unsigned char) proxy_password_len; 
    if(proxy_password && proxy_password_len) {
      /* the length must fit in a single byte */
      if(proxy_password_len > 255) {
        failf(data, "Excessive password length for proxy auth");
        return CURLPX_LONG_PASSWD;
      }
      memcpy(socksreq + len, proxy_password, proxy_password_len); 
    }
    len += proxy_password_len; 
    sxstate(conn, CONNECT_AUTH_SEND);
    sx->outstanding = len;
    sx->outp = socksreq;
  }
    /* FALLTHROUGH */
  case CONNECT_AUTH_SEND:
    result = Curl_write_plain(conn, sockfd, (char *)sx->outp,
                              sx->outstanding, &written);
    if(result && (CURLE_AGAIN != result)) {
      failf(data, "Failed to send SOCKS5 sub-negotiation request."); 
      return CURLPX_SEND_AUTH;
    } 
    if(sx->outstanding != written) {
      /* remain in state */
      sx->outstanding -= written;
      sx->outp += written;
      return CURLPX_OK;
    }
    sx->outp = socksreq;
    sx->outstanding = 2;
    sxstate(conn, CONNECT_AUTH_READ);
    /* FALLTHROUGH */
  case CONNECT_AUTH_READ:
    result = Curl_read_plain(sockfd, (char *)sx->outp,
                             sx->outstanding, &actualread);
    if(result && (CURLE_AGAIN != result)) {
      failf(data, "Unable to receive SOCKS5 sub-negotiation response."); 
      return CURLPX_RECV_AUTH;
    } 
    else if(!result && !actualread) {
      /* connection closed */
      failf(data, "connection to proxy closed");
      return CURLPX_CLOSED;
    }
    else if(actualread != sx->outstanding) {
      /* remain in state */
      sx->outstanding -= actualread;
      sx->outp += actualread;
      return CURLPX_OK;
    }
    /* ignore the first (VER) byte */ 
    else if(socksreq[1] != 0) { /* status */
      failf(data, "User was rejected by the SOCKS5 server (%d %d).", 
            socksreq[0], socksreq[1]); 
      return CURLPX_USER_REJECTED;
    } 
 
    /* Everything is good so far, user was authenticated! */ 
    sxstate(conn, CONNECT_REQ_INIT);
    /* FALLTHROUGH */
  CONNECT_REQ_INIT:
  case CONNECT_REQ_INIT:
    if(socks5_resolve_local) {
      enum resolve_t rc = Curl_resolv(conn, hostname, remote_port,
                                      FALSE, &dns);

      if(rc == CURLRESOLV_ERROR)
        return CURLPX_RESOLVE_HOST;

      if(rc == CURLRESOLV_PENDING) {
        sxstate(conn, CONNECT_RESOLVING);
        return CURLPX_OK;
      } 
      sxstate(conn, CONNECT_RESOLVED);
      goto CONNECT_RESOLVED;
    } 
    goto CONNECT_RESOLVE_REMOTE;
 
  case CONNECT_RESOLVING:
    /* check if we have the name resolved by now */
    dns = Curl_fetch_addr(conn, hostname, remote_port);
 
    if(dns) {
#ifdef CURLRES_ASYNCH
      conn->async.dns = dns;
      conn->async.done = TRUE;
#endif
      infof(data, "SOCKS5: hostname '%s' found\n", hostname);
    }
 
    if(!dns) {
      result = Curl_resolv_check(data->conn, &dns);
      if(!dns) {
        if(result)
          return CURLPX_RESOLVE_HOST;
        return CURLPX_OK;
      }
    } 
    /* FALLTHROUGH */
  CONNECT_RESOLVED:
  case CONNECT_RESOLVED: {
    struct Curl_addrinfo *hp = NULL;
    size_t destlen;
    if(dns) 
      hp = dns->addr;
    if(!hp) {
      failf(data, "Failed to resolve \"%s\" for SOCKS5 connect.",
            hostname);
      return CURLPX_RESOLVE_HOST;
    }
 
    Curl_printable_address(hp, dest, sizeof(dest));
    destlen = strlen(dest);
    msnprintf(dest + destlen, sizeof(dest) - destlen, ":%d", remote_port);
 
    len = 0;
    socksreq[len++] = 5; /* version (SOCKS5) */
    socksreq[len++] = 1; /* connect */
    socksreq[len++] = 0; /* must be zero */
    if(hp->ai_family == AF_INET) {
      int i;
      struct sockaddr_in *saddr_in;
      socksreq[len++] = 1; /* ATYP: IPv4 = 1 */

      saddr_in = (struct sockaddr_in *)(void *)hp->ai_addr;
      for(i = 0; i < 4; i++) {
        socksreq[len++] = ((unsigned char *)&saddr_in->sin_addr.s_addr)[i];
      } 

      infof(data, "SOCKS5 connect to IPv4 %s (locally resolved)\n", dest);
    }
#ifdef ENABLE_IPV6 
    else if(hp->ai_family == AF_INET6) {
      int i;
      struct sockaddr_in6 *saddr_in6;
      socksreq[len++] = 4; /* ATYP: IPv6 = 4 */
 
      saddr_in6 = (struct sockaddr_in6 *)(void *)hp->ai_addr;
      for(i = 0; i < 16; i++) {
        socksreq[len++] =
          ((unsigned char *)&saddr_in6->sin6_addr.s6_addr)[i];
      } 
 
      infof(data, "SOCKS5 connect to IPv6 %s (locally resolved)\n", dest);
    } 
#endif
    else {
      hp = NULL; /* fail! */
      failf(data, "SOCKS5 connection to %s not supported\n", dest);
    } 
 
    Curl_resolv_unlock(data, dns); /* not used anymore from now on */
    goto CONNECT_REQ_SEND;
  } 
  CONNECT_RESOLVE_REMOTE:
  case CONNECT_RESOLVE_REMOTE:
    /* Authentication is complete, now specify destination to the proxy */
    len = 0;
    socksreq[len++] = 5; /* version (SOCKS5) */
    socksreq[len++] = 1; /* connect */
    socksreq[len++] = 0; /* must be zero */
 
    if(!socks5_resolve_local) {
      socksreq[len++] = 3; /* ATYP: domain name = 3 */
      socksreq[len++] = (char) hostname_len; /* one byte address length */
      memcpy(&socksreq[len], hostname, hostname_len); /* address w/o NULL */
      len += hostname_len;
      infof(data, "SOCKS5 connect to %s:%d (remotely resolved)\n",
            hostname, remote_port);
    }
    /* FALLTHROUGH */
 
  CONNECT_REQ_SEND:
  case CONNECT_REQ_SEND:
    /* PORT MSB */
    socksreq[len++] = (unsigned char)((remote_port >> 8) & 0xff);
    /* PORT LSB */
    socksreq[len++] = (unsigned char)(remote_port & 0xff);
 
#if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI) 
    if(conn->socks5_gssapi_enctype) {
      failf(data, "SOCKS5 GSS-API protection not yet implemented.");
      return CURLPX_GSSAPI_PROTECTION;
    }
#endif 
    sx->outp = socksreq;
    sx->outstanding = len;
    sxstate(conn, CONNECT_REQ_SENDING);
    /* FALLTHROUGH */
  case CONNECT_REQ_SENDING:
    result = Curl_write_plain(conn, sockfd, (char *)sx->outp,
                              sx->outstanding, &written);
    if(result && (CURLE_AGAIN != result)) {
      failf(data, "Failed to send SOCKS5 connect request.");
      return CURLPX_SEND_REQUEST;
    }
    if(sx->outstanding != written) {
      /* remain in state */
      sx->outstanding -= written;
      sx->outp += written;
      return CURLPX_OK;
    }
#if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
    if(conn->socks5_gssapi_enctype) {
      failf(data, "SOCKS5 GSS-API protection not yet implemented.");
      return CURLPX_GSSAPI_PROTECTION;
    }
#endif
    sx->outstanding = 10; /* minimum packet size is 10 */
    sx->outp = socksreq;
    sxstate(conn, CONNECT_REQ_READ);
    /* FALLTHROUGH */
  case CONNECT_REQ_READ:
    result = Curl_read_plain(sockfd, (char *)sx->outp,
                             sx->outstanding, &actualread);
    if(result && (CURLE_AGAIN != result)) {
      failf(data, "Failed to receive SOCKS5 connect request ack.");
      return CURLPX_RECV_REQACK;
    }
    else if(!result && !actualread) {
      /* connection closed */
      failf(data, "connection to proxy closed");
      return CURLPX_CLOSED;
    }
    else if(actualread != sx->outstanding) {
      /* remain in state */
      sx->outstanding -= actualread;
      sx->outp += actualread;
      return CURLPX_OK;
    }
 
    if(socksreq[0] != 5) { /* version */
      failf(data,
            "SOCKS5 reply has wrong version, version should be 5.");
      return CURLPX_BAD_VERSION;
    }
    else if(socksreq[1] != 0) { /* Anything besides 0 is an error */
      CURLproxycode rc = CURLPX_REPLY_UNASSIGNED;
      int code = socksreq[1];
      failf(data, "Can't complete SOCKS5 connection to %s. (%d)",
            hostname, (unsigned char)socksreq[1]);
      if(code < 9) {
        /* RFC 1928 section 6 lists: */
        static const CURLproxycode lookup[] = {
          CURLPX_OK,
          CURLPX_REPLY_GENERAL_SERVER_FAILURE,
          CURLPX_REPLY_NOT_ALLOWED,
          CURLPX_REPLY_NETWORK_UNREACHABLE,
          CURLPX_REPLY_HOST_UNREACHABLE,
          CURLPX_REPLY_CONNECTION_REFUSED,
          CURLPX_REPLY_TTL_EXPIRED,
          CURLPX_REPLY_COMMAND_NOT_SUPPORTED,
          CURLPX_REPLY_ADDRESS_TYPE_NOT_SUPPORTED,
        };
        rc = lookup[code];
      }
      return rc;
    }
 
    /* Fix: in general, returned BND.ADDR is variable length parameter by RFC
       1928, so the reply packet should be read until the end to avoid errors
       at subsequent protocol level.
 
       +----+-----+-------+------+----------+----------+
       |VER | REP |  RSV  | ATYP | BND.ADDR | BND.PORT |
       +----+-----+-------+------+----------+----------+
       | 1  |  1  | X'00' |  1   | Variable |    2     |
       +----+-----+-------+------+----------+----------+
 
       ATYP:
       o  IP v4 address: X'01', BND.ADDR = 4 byte
       o  domain name:  X'03', BND.ADDR = [ 1 byte length, string ]
       o  IP v6 address: X'04', BND.ADDR = 16 byte
    */
 
    /* Calculate real packet size */
    if(socksreq[3] == 3) {
      /* domain name */
      int addrlen = (int) socksreq[4];
      len = 5 + addrlen + 2;
    }
    else if(socksreq[3] == 4) {
      /* IPv6 */
      len = 4 + 16 + 2;
    }
    else if(socksreq[3] == 1) {
      len = 4 + 4 + 2;
    }
    else {
      failf(data, "SOCKS5 reply has wrong address type.");
      return CURLPX_BAD_ADDRESS_TYPE;
    }
 
    /* At this point we already read first 10 bytes */
#if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI) 
    if(!conn->socks5_gssapi_enctype) {
      /* decrypt_gssapi_blockread already read the whole packet */
#endif 
      if(len > 10) {
        sx->outstanding = len - 10; /* get the rest */
        sx->outp = &socksreq[10];
        sxstate(conn, CONNECT_REQ_READ_MORE);
      } 
      else {
        sxstate(conn, CONNECT_DONE);
        break;
      }
#if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
    } 
#endif 
    /* FALLTHROUGH */
  case CONNECT_REQ_READ_MORE:
    result = Curl_read_plain(sockfd, (char *)sx->outp,
                             sx->outstanding, &actualread);
    if(result && (CURLE_AGAIN != result)) {
      failf(data, "Failed to receive SOCKS5 connect request ack.");
      return CURLPX_RECV_ADDRESS;
    }
    else if(!result && !actualread) {
      /* connection closed */
      failf(data, "connection to proxy closed");
      return CURLPX_CLOSED;
    }
    else if(actualread != sx->outstanding) {
      /* remain in state */
      sx->outstanding -= actualread;
      sx->outp += actualread;
      return CURLPX_OK;
    }
    sxstate(conn, CONNECT_DONE);
  }
  infof(data, "SOCKS5 request granted.\n");

  *done = TRUE;
  return CURLPX_OK; /* Proxy was successful! */
} 
 
#endif /* CURL_DISABLE_PROXY */