text: /***************************************************************************
   *                                  _   _ ____  _
   *  Project                     ___| | | |  _ \| |
   *                             / __| | | | |_) | |
   *                            | (__| |_| |  _ <| |___
   *                             \___|\___/|_| \_\_____|
   *
   * Copyright (C) 1998 - 2021, 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 Curl_easy *data,   /* transfer */
                         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(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 Curl_easy *data,
                         enum connect_t state
  #ifdef DEBUGBUILD
                         , int lineno
  #endif
  )
  {
    struct connectdata *conn = data->conn;
    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(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 Curl_easy *data,
                            bool *done)
  {
    struct connectdata *conn = data->conn;
    const bool protocol4a =
      (conn->socks_proxy.proxytype == CURLPROXY_SOCKS4A) ? TRUE : FALSE;
    unsigned char *socksreq = (unsigned char *)data->state.buffer;
    CURLcode result;
    curl_socket_t sockfd = conn->sock[sockindex];
    struct connstate *sx = &conn->cnnct;
    struct Curl_dns_entry *dns = NULL;
    ssize_t actualread;
    ssize_t written;
  
    /* make sure that the buffer is at least 600 bytes */
    DEBUGASSERT(READBUFFER_MIN >= 600);
  
    if(!SOCKS_STATE(sx->state) && !*done)
      sxstate(data, 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(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(data, hostname, remote_port, FALSE, &dns);
  
        if(rc == CURLRESOLV_ERROR)
          return CURLPX_RESOLVE_HOST;
        else if(rc == CURLRESOLV_PENDING) {
          sxstate(data, CONNECT_RESOLVING);
          infof(data, "SOCKS4 non-blocking resolve of %s\n", hostname);
          return CURLPX_OK;
        }
        sxstate(data, CONNECT_RESOLVED);
        goto CONNECT_RESOLVED;
      }
  
      /* socks4a doesn't resolve anything locally */
      sxstate(data, CONNECT_REQ_INIT);
      goto CONNECT_REQ_INIT;
  
    case CONNECT_RESOLVING:
      /* check if we have the name resolved by now */
      dns = Curl_fetch_addr(data, hostname, (int)conn->port);
  
      if(dns) {
  #ifdef CURLRES_ASYNCH
        data->state.async.dns = dns;
        data->state.async.done = TRUE;
  #endif
        infof(data, "Hostname '%s' was found\n", hostname);
        sxstate(data, CONNECT_RESOLVED);
      }
      else {
        result = Curl_resolv_check(data, &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", 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 >= (size_t)data->set.buffer_size - 8) {
          failf(data, "Too long SOCKS proxy user name, can't use!");
          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(data, CONNECT_REQ_SENDING);
      }
      /* FALLTHROUGH */
    case CONNECT_REQ_SENDING:
      /* Send request */
      result = Curl_write_plain(data, 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(data, 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(data, 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.",
            socksreq[4], socksreq[5], socksreq[6], 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.",
            socksreq[4], socksreq[5], socksreq[6], 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.",
            socksreq[4], socksreq[5], socksreq[6], 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.",
            socksreq[4], socksreq[5], socksreq[6], 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 Curl_easy *data,
                            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
    */
    struct connectdata *conn = data->conn;
    unsigned char *socksreq = (unsigned char *)data->state.buffer;
    char dest[256] = "unknown";  /* printable hostname:port */
    int idx;
    ssize_t actualread;
    ssize_t written;
    CURLcode result;
    curl_socket_t sockfd = conn->sock[sockindex];
    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(data, CONNECT_SOCKS_INIT);
  
    switch(sx->state) {
    case CONNECT_SOCKS_INIT:
      if(conn->bits.httpproxy)
        infof(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(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(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(data, 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(data, CONNECT_SOCKS_SEND);
        sx->outstanding = idx - written;
        sx->outp = &socksreq[written];
        return CURLPX_OK;
      }
      sxstate(data, CONNECT_SOCKS_READ);
      goto CONNECT_SOCKS_READ_INIT;
    case CONNECT_SOCKS_SEND:
      result = Curl_write_plain(data, 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(data, CONNECT_REQ_INIT);
        goto CONNECT_REQ_INIT;
      }
      else if(socksreq[1] == 2) {
        /* regular name + password authentication */
        sxstate(data, CONNECT_AUTH_INIT);
        goto CONNECT_AUTH_INIT;
      }
  #if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
      else if(allow_gssapi && (socksreq[1] == 1)) {
        sxstate(data, CONNECT_GSSAPI_INIT);
        result = Curl_SOCKS5_gssapi_negotiate(sockindex, data);
        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(data, CONNECT_AUTH_SEND);
      sx->outstanding = len;
      sx->outp = socksreq;
    }
      /* FALLTHROUGH */
    case CONNECT_AUTH_SEND:
      result = Curl_write_plain(data, 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(data, 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(data, CONNECT_REQ_INIT);
      /* FALLTHROUGH */
    CONNECT_REQ_INIT:
    case CONNECT_REQ_INIT:
      if(socks5_resolve_local) {
        enum resolve_t rc = Curl_resolv(data, hostname, remote_port,
                                        FALSE, &dns);
  
        if(rc == CURLRESOLV_ERROR)
          return CURLPX_RESOLVE_HOST;
  
        if(rc == CURLRESOLV_PENDING) {
          sxstate(data, CONNECT_RESOLVING);
          return CURLPX_OK;
        }
        sxstate(data, 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(data, hostname, remote_port);
  
      if(dns) {
  #ifdef CURLRES_ASYNCH
        data->state.async.dns = dns;
        data->state.async.done = TRUE;
  #endif
        infof(data, "SOCKS5: hostname '%s' found\n", hostname);
      }
  
      if(!dns) {
        result = Curl_resolv_check(data, &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", 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(data, CONNECT_REQ_SENDING);
      /* FALLTHROUGH */
    case CONNECT_REQ_SENDING:
      result = Curl_write_plain(data, 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(data, 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(data, CONNECT_REQ_READ_MORE);
        }
        else {
          sxstate(data, 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(data, CONNECT_DONE);
    }
    infof(data, "SOCKS5 request granted.\n");
  
    *done = TRUE;
    return CURLPX_OK; /* Proxy was successful! */
  }
  
  #endif /* CURL_DISABLE_PROXY */
  