• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 /***************************************************************************
2  *                                  _   _ ____  _
3  *  Project                     ___| | | |  _ \| |
4  *                             / __| | | | |_) | |
5  *                            | (__| |_| |  _ <| |___
6  *                             \___|\___/|_| \_\_____|
7  *
8  * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
9  *
10  * This software is licensed as described in the file COPYING, which
11  * you should have received as part of this distribution. The terms
12  * are also available at http://curl.haxx.se/docs/copyright.html.
13  *
14  * You may opt to use, copy, modify, merge, publish, distribute and/or sell
15  * copies of the Software, and permit persons to whom the Software is
16  * furnished to do so, under the terms of the COPYING file.
17  *
18  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
19  * KIND, either express or implied.
20  *
21  ***************************************************************************/
22 
23 #include "curl_setup.h"
24 
25 #if !defined(CURL_DISABLE_PROXY)
26 
27 #ifdef HAVE_NETINET_IN_H
28 #include <netinet/in.h>
29 #endif
30 #ifdef HAVE_ARPA_INET_H
31 #include <arpa/inet.h>
32 #endif
33 
34 #include "urldata.h"
35 #include "sendf.h"
36 #include "strequal.h"
37 #include "select.h"
38 #include "connect.h"
39 #include "timeval.h"
40 #include "socks.h"
41 
42 /* The last #include file should be: */
43 #include "memdebug.h"
44 
45 /*
46  * Helper read-from-socket functions. Does the same as Curl_read() but it
47  * blocks until all bytes amount of buffersize will be read. No more, no less.
48  *
49  * This is STUPID BLOCKING behaviour which we frown upon, but right now this
50  * is what we have...
51  */
Curl_blockread_all(struct connectdata * conn,curl_socket_t sockfd,char * buf,ssize_t buffersize,ssize_t * n)52 int Curl_blockread_all(struct connectdata *conn, /* connection data */
53                        curl_socket_t sockfd,     /* read from this socket */
54                        char *buf,                /* store read data here */
55                        ssize_t buffersize,       /* max amount to read */
56                        ssize_t *n)               /* amount bytes read */
57 {
58   ssize_t nread;
59   ssize_t allread = 0;
60   int result;
61   long timeleft;
62   *n = 0;
63   for(;;) {
64     timeleft = Curl_timeleft(conn->data, NULL, TRUE);
65     if(timeleft < 0) {
66       /* we already got the timeout */
67       result = CURLE_OPERATION_TIMEDOUT;
68       break;
69     }
70     if(Curl_socket_ready(sockfd, CURL_SOCKET_BAD, timeleft) <= 0) {
71       result = ~CURLE_OK;
72       break;
73     }
74     result = Curl_read_plain(sockfd, buf, buffersize, &nread);
75     if(CURLE_AGAIN == result)
76       continue;
77     else if(result)
78       break;
79 
80     if(buffersize == nread) {
81       allread += nread;
82       *n = allread;
83       result = CURLE_OK;
84       break;
85     }
86     if(!nread) {
87       result = ~CURLE_OK;
88       break;
89     }
90 
91     buffersize -= nread;
92     buf += nread;
93     allread += nread;
94   }
95   return result;
96 }
97 
98 /*
99 * This function logs in to a SOCKS4 proxy and sends the specifics to the final
100 * destination server.
101 *
102 * Reference :
103 *   http://socks.permeo.com/protocol/socks4.protocol
104 *
105 * Note :
106 *   Set protocol4a=true for  "SOCKS 4A (Simple Extension to SOCKS 4 Protocol)"
107 *   Nonsupport "Identification Protocol (RFC1413)"
108 */
Curl_SOCKS4(const char * proxy_name,const char * hostname,int remote_port,int sockindex,struct connectdata * conn,bool protocol4a)109 CURLcode Curl_SOCKS4(const char *proxy_name,
110                      const char *hostname,
111                      int remote_port,
112                      int sockindex,
113                      struct connectdata *conn,
114                      bool protocol4a)
115 {
116 #define SOCKS4REQLEN 262
117   unsigned char socksreq[SOCKS4REQLEN]; /* room for SOCKS4 request incl. user
118                                            id */
119   int result;
120   CURLcode code;
121   curl_socket_t sock = conn->sock[sockindex];
122   struct SessionHandle *data = conn->data;
123 
124   if(Curl_timeleft(data, NULL, TRUE) < 0) {
125     /* time-out, bail out, go home */
126     failf(data, "Connection time-out");
127     return CURLE_OPERATION_TIMEDOUT;
128   }
129 
130   (void)curlx_nonblock(sock, FALSE);
131 
132   infof(data, "SOCKS4 communication to %s:%d\n", hostname, remote_port);
133 
134   /*
135    * Compose socks4 request
136    *
137    * Request format
138    *
139    *     +----+----+----+----+----+----+----+----+----+----+....+----+
140    *     | VN | CD | DSTPORT |      DSTIP        | USERID       |NULL|
141    *     +----+----+----+----+----+----+----+----+----+----+....+----+
142    * # of bytes:  1    1      2              4           variable       1
143    */
144 
145   socksreq[0] = 4; /* version (SOCKS4) */
146   socksreq[1] = 1; /* connect */
147   socksreq[2] = (unsigned char)((remote_port >> 8) & 0xff); /* PORT MSB */
148   socksreq[3] = (unsigned char)(remote_port & 0xff);        /* PORT LSB */
149 
150   /* DNS resolve only for SOCKS4, not SOCKS4a */
151   if(!protocol4a) {
152     struct Curl_dns_entry *dns;
153     Curl_addrinfo *hp=NULL;
154     int rc;
155 
156     rc = Curl_resolv(conn, hostname, remote_port, &dns);
157 
158     if(rc == CURLRESOLV_ERROR)
159       return CURLE_COULDNT_RESOLVE_PROXY;
160 
161     if(rc == CURLRESOLV_PENDING)
162       /* ignores the return code, but 'dns' remains NULL on failure */
163       (void)Curl_resolver_wait_resolv(conn, &dns);
164 
165     /*
166      * We cannot use 'hostent' as a struct that Curl_resolv() returns.  It
167      * returns a Curl_addrinfo pointer that may not always look the same.
168      */
169     if(dns)
170       hp=dns->addr;
171     if(hp) {
172       char buf[64];
173       unsigned short ip[4];
174       Curl_printable_address(hp, buf, sizeof(buf));
175 
176       if(4 == sscanf( buf, "%hu.%hu.%hu.%hu",
177                       &ip[0], &ip[1], &ip[2], &ip[3])) {
178         /* Set DSTIP */
179         socksreq[4] = (unsigned char)ip[0];
180         socksreq[5] = (unsigned char)ip[1];
181         socksreq[6] = (unsigned char)ip[2];
182         socksreq[7] = (unsigned char)ip[3];
183       }
184       else
185         hp = NULL; /* fail! */
186 
187       infof(data, "SOCKS4 connect to %s (locally resolved)\n", buf);
188 
189       Curl_resolv_unlock(data, dns); /* not used anymore from now on */
190 
191     }
192     if(!hp) {
193       failf(data, "Failed to resolve \"%s\" for SOCKS4 connect.",
194             hostname);
195       return CURLE_COULDNT_RESOLVE_HOST;
196     }
197   }
198 
199   /*
200    * This is currently not supporting "Identification Protocol (RFC1413)".
201    */
202   socksreq[8] = 0; /* ensure empty userid is NUL-terminated */
203   if(proxy_name) {
204     size_t plen = strlen(proxy_name);
205     if(plen >= sizeof(socksreq) - 8) {
206       failf(data, "Too long SOCKS proxy name, can't use!\n");
207       return CURLE_COULDNT_CONNECT;
208     }
209     /* copy the proxy name WITH trailing zero */
210     memcpy(socksreq + 8, proxy_name, plen+1);
211   }
212 
213   /*
214    * Make connection
215    */
216   {
217     ssize_t actualread;
218     ssize_t written;
219     ssize_t hostnamelen = 0;
220     int packetsize = 9 +
221       (int)strlen((char*)socksreq + 8); /* size including NUL */
222 
223     /* If SOCKS4a, set special invalid IP address 0.0.0.x */
224     if(protocol4a) {
225       socksreq[4] = 0;
226       socksreq[5] = 0;
227       socksreq[6] = 0;
228       socksreq[7] = 1;
229       /* If still enough room in buffer, also append hostname */
230       hostnamelen = (ssize_t)strlen(hostname) + 1; /* length including NUL */
231       if(packetsize + hostnamelen <= SOCKS4REQLEN)
232         strcpy((char*)socksreq + packetsize, hostname);
233       else
234         hostnamelen = 0; /* Flag: hostname did not fit in buffer */
235     }
236 
237     /* Send request */
238     code = Curl_write_plain(conn, sock, (char *)socksreq,
239                             packetsize + hostnamelen,
240                             &written);
241     if(code || (written != packetsize + hostnamelen)) {
242       failf(data, "Failed to send SOCKS4 connect request.");
243       return CURLE_COULDNT_CONNECT;
244     }
245     if(protocol4a && hostnamelen == 0) {
246       /* SOCKS4a with very long hostname - send that name separately */
247       hostnamelen = (ssize_t)strlen(hostname) + 1;
248       code = Curl_write_plain(conn, sock, (char *)hostname, hostnamelen,
249                               &written);
250       if(code || (written != hostnamelen)) {
251         failf(data, "Failed to send SOCKS4 connect request.");
252         return CURLE_COULDNT_CONNECT;
253       }
254     }
255 
256     packetsize = 8; /* receive data size */
257 
258     /* Receive response */
259     result = Curl_blockread_all(conn, sock, (char *)socksreq, packetsize,
260                                 &actualread);
261     if(result || (actualread != packetsize)) {
262       failf(data, "Failed to receive SOCKS4 connect request ack.");
263       return CURLE_COULDNT_CONNECT;
264     }
265 
266     /*
267      * Response format
268      *
269      *     +----+----+----+----+----+----+----+----+
270      *     | VN | CD | DSTPORT |      DSTIP        |
271      *     +----+----+----+----+----+----+----+----+
272      * # of bytes:  1    1      2              4
273      *
274      * VN is the version of the reply code and should be 0. CD is the result
275      * code with one of the following values:
276      *
277      * 90: request granted
278      * 91: request rejected or failed
279      * 92: request rejected because SOCKS server cannot connect to
280      *     identd on the client
281      * 93: request rejected because the client program and identd
282      *     report different user-ids
283      */
284 
285     /* wrong version ? */
286     if(socksreq[0] != 0) {
287       failf(data,
288             "SOCKS4 reply has wrong version, version should be 4.");
289       return CURLE_COULDNT_CONNECT;
290     }
291 
292     /* Result */
293     switch(socksreq[1]) {
294     case 90:
295       infof(data, "SOCKS4%s request granted.\n", protocol4a?"a":"");
296       break;
297     case 91:
298       failf(data,
299             "Can't complete SOCKS4 connection to %d.%d.%d.%d:%d. (%d)"
300             ", request rejected or failed.",
301             (unsigned char)socksreq[4], (unsigned char)socksreq[5],
302             (unsigned char)socksreq[6], (unsigned char)socksreq[7],
303             ((socksreq[8] << 8) | socksreq[9]),
304             socksreq[1]);
305       return CURLE_COULDNT_CONNECT;
306     case 92:
307       failf(data,
308             "Can't complete SOCKS4 connection to %d.%d.%d.%d:%d. (%d)"
309             ", request rejected because SOCKS server cannot connect to "
310             "identd on the client.",
311             (unsigned char)socksreq[4], (unsigned char)socksreq[5],
312             (unsigned char)socksreq[6], (unsigned char)socksreq[7],
313             ((socksreq[8] << 8) | socksreq[9]),
314             socksreq[1]);
315       return CURLE_COULDNT_CONNECT;
316     case 93:
317       failf(data,
318             "Can't complete SOCKS4 connection to %d.%d.%d.%d:%d. (%d)"
319             ", request rejected because the client program and identd "
320             "report different user-ids.",
321             (unsigned char)socksreq[4], (unsigned char)socksreq[5],
322             (unsigned char)socksreq[6], (unsigned char)socksreq[7],
323             ((socksreq[8] << 8) | socksreq[9]),
324             socksreq[1]);
325       return CURLE_COULDNT_CONNECT;
326     default:
327       failf(data,
328             "Can't complete SOCKS4 connection to %d.%d.%d.%d:%d. (%d)"
329             ", Unknown.",
330             (unsigned char)socksreq[4], (unsigned char)socksreq[5],
331             (unsigned char)socksreq[6], (unsigned char)socksreq[7],
332             ((socksreq[8] << 8) | socksreq[9]),
333             socksreq[1]);
334       return CURLE_COULDNT_CONNECT;
335     }
336   }
337 
338   (void)curlx_nonblock(sock, TRUE);
339 
340   return CURLE_OK; /* Proxy was successful! */
341 }
342 
343 /*
344  * This function logs in to a SOCKS5 proxy and sends the specifics to the final
345  * destination server.
346  */
Curl_SOCKS5(const char * proxy_name,const char * proxy_password,const char * hostname,int remote_port,int sockindex,struct connectdata * conn)347 CURLcode Curl_SOCKS5(const char *proxy_name,
348                      const char *proxy_password,
349                      const char *hostname,
350                      int remote_port,
351                      int sockindex,
352                      struct connectdata *conn)
353 {
354   /*
355     According to the RFC1928, section "6.  Replies". This is what a SOCK5
356     replies:
357 
358         +----+-----+-------+------+----------+----------+
359         |VER | REP |  RSV  | ATYP | BND.ADDR | BND.PORT |
360         +----+-----+-------+------+----------+----------+
361         | 1  |  1  | X'00' |  1   | Variable |    2     |
362         +----+-----+-------+------+----------+----------+
363 
364     Where:
365 
366     o  VER    protocol version: X'05'
367     o  REP    Reply field:
368     o  X'00' succeeded
369   */
370 
371   unsigned char socksreq[600]; /* room for large user/pw (255 max each) */
372   ssize_t actualread;
373   ssize_t written;
374   int result;
375   CURLcode code;
376   curl_socket_t sock = conn->sock[sockindex];
377   struct SessionHandle *data = conn->data;
378   long timeout;
379   bool socks5_resolve_local = (conn->proxytype == CURLPROXY_SOCKS5)?TRUE:FALSE;
380   const size_t hostname_len = strlen(hostname);
381   ssize_t len = 0;
382 
383   /* RFC1928 chapter 5 specifies max 255 chars for domain name in packet */
384   if(!socks5_resolve_local && hostname_len > 255) {
385     infof(conn->data, "SOCKS5: server resolving disabled for hostnames of "
386           "length > 255 [actual len=%zu]\n", hostname_len);
387     socks5_resolve_local = TRUE;
388   }
389 
390   /* get timeout */
391   timeout = Curl_timeleft(data, NULL, TRUE);
392 
393   if(timeout < 0) {
394     /* time-out, bail out, go home */
395     failf(data, "Connection time-out");
396     return CURLE_OPERATION_TIMEDOUT;
397   }
398 
399   (void)curlx_nonblock(sock, TRUE);
400 
401   /* wait until socket gets connected */
402   result = Curl_socket_ready(CURL_SOCKET_BAD, sock, timeout);
403 
404   if(-1 == result) {
405     failf(conn->data, "SOCKS5: no connection here");
406     return CURLE_COULDNT_CONNECT;
407   }
408   else if(0 == result) {
409     failf(conn->data, "SOCKS5: connection timeout");
410     return CURLE_OPERATION_TIMEDOUT;
411   }
412 
413   if(result & CURL_CSELECT_ERR) {
414     failf(conn->data, "SOCKS5: error occurred during connection");
415     return CURLE_COULDNT_CONNECT;
416   }
417 
418   socksreq[0] = 5; /* version */
419 #if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
420   socksreq[1] = (char)(proxy_name ? 3 : 2); /* number of methods (below) */
421   socksreq[2] = 0; /* no authentication */
422   socksreq[3] = 1; /* GSS-API */
423   socksreq[4] = 2; /* username/password */
424 #else
425   socksreq[1] = (char)(proxy_name ? 2 : 1); /* number of methods (below) */
426   socksreq[2] = 0; /* no authentication */
427   socksreq[3] = 2; /* username/password */
428 #endif
429 
430   (void)curlx_nonblock(sock, FALSE);
431 
432   code = Curl_write_plain(conn, sock, (char *)socksreq, (2 + (int)socksreq[1]),
433                           &written);
434   if(code || (written != (2 + (int)socksreq[1]))) {
435     failf(data, "Unable to send initial SOCKS5 request.");
436     return CURLE_COULDNT_CONNECT;
437   }
438 
439   (void)curlx_nonblock(sock, TRUE);
440 
441   result = Curl_socket_ready(sock, CURL_SOCKET_BAD, timeout);
442 
443   if(-1 == result) {
444     failf(conn->data, "SOCKS5 nothing to read");
445     return CURLE_COULDNT_CONNECT;
446   }
447   else if(0 == result) {
448     failf(conn->data, "SOCKS5 read timeout");
449     return CURLE_OPERATION_TIMEDOUT;
450   }
451 
452   if(result & CURL_CSELECT_ERR) {
453     failf(conn->data, "SOCKS5 read error occurred");
454     return CURLE_RECV_ERROR;
455   }
456 
457   (void)curlx_nonblock(sock, FALSE);
458 
459   result=Curl_blockread_all(conn, sock, (char *)socksreq, 2, &actualread);
460   if(result || (actualread != 2)) {
461     failf(data, "Unable to receive initial SOCKS5 response.");
462     return CURLE_COULDNT_CONNECT;
463   }
464 
465   if(socksreq[0] != 5) {
466     failf(data, "Received invalid version in initial SOCKS5 response.");
467     return CURLE_COULDNT_CONNECT;
468   }
469   if(socksreq[1] == 0) {
470     /* Nothing to do, no authentication needed */
471     ;
472   }
473 #if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
474   else if(socksreq[1] == 1) {
475     code = Curl_SOCKS5_gssapi_negotiate(sockindex, conn);
476     if(code) {
477       failf(data, "Unable to negotiate SOCKS5 GSS-API context.");
478       return CURLE_COULDNT_CONNECT;
479     }
480   }
481 #endif
482   else if(socksreq[1] == 2) {
483     /* Needs user name and password */
484     size_t proxy_name_len, proxy_password_len;
485     if(proxy_name && proxy_password) {
486       proxy_name_len = strlen(proxy_name);
487       proxy_password_len = strlen(proxy_password);
488     }
489     else {
490       proxy_name_len = 0;
491       proxy_password_len = 0;
492     }
493 
494     /*   username/password request looks like
495      * +----+------+----------+------+----------+
496      * |VER | ULEN |  UNAME   | PLEN |  PASSWD  |
497      * +----+------+----------+------+----------+
498      * | 1  |  1   | 1 to 255 |  1   | 1 to 255 |
499      * +----+------+----------+------+----------+
500      */
501     len = 0;
502     socksreq[len++] = 1;    /* username/pw subnegotiation version */
503     socksreq[len++] = (unsigned char) proxy_name_len;
504     if(proxy_name && proxy_name_len)
505       memcpy(socksreq + len, proxy_name, proxy_name_len);
506     len += proxy_name_len;
507     socksreq[len++] = (unsigned char) proxy_password_len;
508     if(proxy_password && proxy_password_len)
509       memcpy(socksreq + len, proxy_password, proxy_password_len);
510     len += proxy_password_len;
511 
512     code = Curl_write_plain(conn, sock, (char *)socksreq, len, &written);
513     if(code || (len != written)) {
514       failf(data, "Failed to send SOCKS5 sub-negotiation request.");
515       return CURLE_COULDNT_CONNECT;
516     }
517 
518     result=Curl_blockread_all(conn, sock, (char *)socksreq, 2, &actualread);
519     if(result || (actualread != 2)) {
520       failf(data, "Unable to receive SOCKS5 sub-negotiation response.");
521       return CURLE_COULDNT_CONNECT;
522     }
523 
524     /* ignore the first (VER) byte */
525     if(socksreq[1] != 0) { /* status */
526       failf(data, "User was rejected by the SOCKS5 server (%d %d).",
527             socksreq[0], socksreq[1]);
528       return CURLE_COULDNT_CONNECT;
529     }
530 
531     /* Everything is good so far, user was authenticated! */
532   }
533   else {
534     /* error */
535 #if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
536     if(socksreq[1] == 255) {
537 #else
538     if(socksreq[1] == 1) {
539       failf(data,
540             "SOCKS5 GSSAPI per-message authentication is not supported.");
541       return CURLE_COULDNT_CONNECT;
542     }
543     else if(socksreq[1] == 255) {
544 #endif
545       if(!proxy_name || !*proxy_name) {
546         failf(data,
547               "No authentication method was acceptable. (It is quite likely"
548               " that the SOCKS5 server wanted a username/password, since none"
549               " was supplied to the server on this connection.)");
550       }
551       else {
552         failf(data, "No authentication method was acceptable.");
553       }
554       return CURLE_COULDNT_CONNECT;
555     }
556     else {
557       failf(data,
558             "Undocumented SOCKS5 mode attempted to be used by server.");
559       return CURLE_COULDNT_CONNECT;
560     }
561   }
562 
563   /* Authentication is complete, now specify destination to the proxy */
564   len = 0;
565   socksreq[len++] = 5; /* version (SOCKS5) */
566   socksreq[len++] = 1; /* connect */
567   socksreq[len++] = 0; /* must be zero */
568 
569   if(!socks5_resolve_local) {
570     socksreq[len++] = 3; /* ATYP: domain name = 3 */
571     socksreq[len++] = (char) hostname_len; /* address length */
572     memcpy(&socksreq[len], hostname, hostname_len); /* address str w/o NULL */
573     len += hostname_len;
574   }
575   else {
576     struct Curl_dns_entry *dns;
577     Curl_addrinfo *hp = NULL;
578     int rc = Curl_resolv(conn, hostname, remote_port, &dns);
579 
580     if(rc == CURLRESOLV_ERROR)
581       return CURLE_COULDNT_RESOLVE_HOST;
582 
583     if(rc == CURLRESOLV_PENDING) {
584       /* this requires that we're in "wait for resolve" state */
585       code = Curl_resolver_wait_resolv(conn, &dns);
586       if(code)
587         return code;
588     }
589 
590     /*
591      * We cannot use 'hostent' as a struct that Curl_resolv() returns.  It
592      * returns a Curl_addrinfo pointer that may not always look the same.
593      */
594     if(dns)
595       hp=dns->addr;
596     if(hp) {
597       struct sockaddr_in *saddr_in;
598 #ifdef ENABLE_IPV6
599       struct sockaddr_in6 *saddr_in6;
600 #endif
601       int i;
602 
603       if(hp->ai_family == AF_INET) {
604         socksreq[len++] = 1; /* ATYP: IPv4 = 1 */
605 
606         saddr_in = (struct sockaddr_in*)hp->ai_addr;
607         for(i = 0; i < 4; i++) {
608           socksreq[len++] = ((unsigned char*)&saddr_in->sin_addr.s_addr)[i];
609           infof(data, "%d\n", socksreq[len-1]);
610         }
611       }
612 #ifdef ENABLE_IPV6
613       else if(hp->ai_family == AF_INET6) {
614         socksreq[len++] = 4; /* ATYP: IPv6 = 4 */
615 
616         saddr_in6 = (struct sockaddr_in6*)hp->ai_addr;
617         for(i = 0; i < 16; i++) {
618           socksreq[len++] = ((unsigned char*)&saddr_in6->sin6_addr.s6_addr)[i];
619         }
620       }
621 #endif
622       else
623         hp = NULL; /* fail! */
624 
625       Curl_resolv_unlock(data, dns); /* not used anymore from now on */
626     }
627     if(!hp) {
628       failf(data, "Failed to resolve \"%s\" for SOCKS5 connect.",
629             hostname);
630       return CURLE_COULDNT_RESOLVE_HOST;
631     }
632   }
633 
634   socksreq[len++] = (unsigned char)((remote_port >> 8) & 0xff); /* PORT MSB */
635   socksreq[len++] = (unsigned char)(remote_port & 0xff);        /* PORT LSB */
636 
637 #if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
638   if(conn->socks5_gssapi_enctype) {
639     failf(data, "SOCKS5 GSS-API protection not yet implemented.");
640   }
641   else
642 #endif
643     code = Curl_write_plain(conn, sock, (char *)socksreq, len, &written);
644 
645   if(code || (len != written)) {
646     failf(data, "Failed to send SOCKS5 connect request.");
647     return CURLE_COULDNT_CONNECT;
648   }
649 
650   len = 10; /* minimum packet size is 10 */
651 
652 #if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
653   if(conn->socks5_gssapi_enctype) {
654     failf(data, "SOCKS5 GSS-API protection not yet implemented.");
655   }
656   else
657 #endif
658     result = Curl_blockread_all(conn, sock, (char *)socksreq,
659                                 len, &actualread);
660 
661   if(result || (len != actualread)) {
662     failf(data, "Failed to receive SOCKS5 connect request ack.");
663     return CURLE_COULDNT_CONNECT;
664   }
665 
666   if(socksreq[0] != 5) { /* version */
667     failf(data,
668           "SOCKS5 reply has wrong version, version should be 5.");
669     return CURLE_COULDNT_CONNECT;
670   }
671   if(socksreq[1] != 0) { /* Anything besides 0 is an error */
672     if(socksreq[3] == 1) {
673       failf(data,
674             "Can't complete SOCKS5 connection to %d.%d.%d.%d:%d. (%d)",
675             (unsigned char)socksreq[4], (unsigned char)socksreq[5],
676             (unsigned char)socksreq[6], (unsigned char)socksreq[7],
677             ((socksreq[8] << 8) | socksreq[9]),
678             socksreq[1]);
679     }
680     else if(socksreq[3] == 3) {
681       failf(data,
682             "Can't complete SOCKS5 connection to %s:%d. (%d)",
683             hostname,
684             ((socksreq[8] << 8) | socksreq[9]),
685             socksreq[1]);
686     }
687     else if(socksreq[3] == 4) {
688       failf(data,
689             "Can't complete SOCKS5 connection to %02x%02x:%02x%02x:"
690             "%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%d. (%d)",
691             (unsigned char)socksreq[4], (unsigned char)socksreq[5],
692             (unsigned char)socksreq[6], (unsigned char)socksreq[7],
693             (unsigned char)socksreq[8], (unsigned char)socksreq[9],
694             (unsigned char)socksreq[10], (unsigned char)socksreq[11],
695             (unsigned char)socksreq[12], (unsigned char)socksreq[13],
696             (unsigned char)socksreq[14], (unsigned char)socksreq[15],
697             (unsigned char)socksreq[16], (unsigned char)socksreq[17],
698             (unsigned char)socksreq[18], (unsigned char)socksreq[19],
699             ((socksreq[8] << 8) | socksreq[9]),
700             socksreq[1]);
701     }
702     return CURLE_COULDNT_CONNECT;
703   }
704 
705   /* Fix: in general, returned BND.ADDR is variable length parameter by RFC
706      1928, so the reply packet should be read until the end to avoid errors at
707      subsequent protocol level.
708 
709     +----+-----+-------+------+----------+----------+
710     |VER | REP |  RSV  | ATYP | BND.ADDR | BND.PORT |
711     +----+-----+-------+------+----------+----------+
712     | 1  |  1  | X'00' |  1   | Variable |    2     |
713     +----+-----+-------+------+----------+----------+
714 
715      ATYP:
716      o  IP v4 address: X'01', BND.ADDR = 4 byte
717      o  domain name:  X'03', BND.ADDR = [ 1 byte length, string ]
718      o  IP v6 address: X'04', BND.ADDR = 16 byte
719      */
720 
721   /* Calculate real packet size */
722   if(socksreq[3] == 3) {
723     /* domain name */
724     int addrlen = (int) socksreq[4];
725     len = 5 + addrlen + 2;
726   }
727   else if(socksreq[3] == 4) {
728     /* IPv6 */
729     len = 4 + 16 + 2;
730   }
731 
732   /* At this point we already read first 10 bytes */
733 #if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
734   if(!conn->socks5_gssapi_enctype) {
735     /* decrypt_gssapi_blockread already read the whole packet */
736 #endif
737     if(len > 10) {
738       len -= 10;
739       result = Curl_blockread_all(conn, sock, (char *)&socksreq[10],
740                                   len, &actualread);
741       if(result || (len != actualread)) {
742         failf(data, "Failed to receive SOCKS5 connect request ack.");
743         return CURLE_COULDNT_CONNECT;
744       }
745     }
746 #if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
747   }
748 #endif
749 
750   (void)curlx_nonblock(sock, TRUE);
751   return CURLE_OK; /* Proxy was successful! */
752 }
753 
754 #endif /* CURL_DISABLE_PROXY */
755 
756