2 * Platform-independent bits of X11 forwarding.
14 #define GET_16BIT(endian, cp) \
15 (endian=='B' ? GET_16BIT_MSB_FIRST(cp) : GET_16BIT_LSB_FIRST(cp))
17 #define PUT_16BIT(endian, cp, val) \
18 (endian=='B' ? PUT_16BIT_MSB_FIRST(cp, val) : PUT_16BIT_LSB_FIRST(cp, val))
20 const char *const x11_authnames[] = {
21 "", "MIT-MAGIC-COOKIE-1", "XDM-AUTHORIZATION-1"
26 unsigned char clientid[6];
30 const struct plug_function_table *fn;
31 /* the above variable absolutely *must* be the first in this structure */
32 unsigned char firstpkt[12]; /* first X data packet */
33 struct X11Display *disp;
35 unsigned char *auth_data;
36 int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize;
38 int throttled, throttle_override;
39 unsigned long peer_ip;
41 void *c; /* data used by ssh.c */
45 static int xdmseen_cmp(void *a, void *b)
47 struct XDMSeen *sa = a, *sb = b;
48 return sa->time > sb->time ? 1 :
49 sa->time < sb->time ? -1 :
50 memcmp(sa->clientid, sb->clientid, sizeof(sa->clientid));
53 struct X11Display *x11_setup_display(char *display, int authtype,
56 struct X11Display *disp = snew(struct X11Display);
60 if (!display || !*display) {
61 localcopy = platform_get_x_display();
62 if (!localcopy || !*localcopy) {
64 localcopy = dupstr(":0"); /* plausible default for any platform */
67 localcopy = dupstr(display);
70 * Parse the display name.
72 * We expect this to have one of the following forms:
74 * - the standard X format which looks like
75 * [ [ protocol '/' ] host ] ':' displaynumber [ '.' screennumber ]
76 * (X11 also permits a double colon to indicate DECnet, but
77 * that's not our problem, thankfully!)
79 * - only seen in the wild on MacOS (so far): a pathname to a
80 * Unix-domain socket, which will typically and confusingly
81 * end in ":0", and which I'm currently distinguishing from
82 * the standard scheme by noting that it starts with '/'.
84 if (localcopy[0] == '/') {
85 disp->unixsocketpath = localcopy;
86 disp->unixdomain = TRUE;
87 disp->hostname = NULL;
88 disp->displaynum = -1;
91 char *colon, *dot, *slash;
92 char *protocol, *hostname;
94 colon = strrchr(localcopy, ':');
98 return NULL; /* FIXME: report a specific error? */
102 dot = strchr(colon, '.');
106 disp->displaynum = atoi(colon);
108 disp->screennum = atoi(dot);
113 hostname = localcopy;
114 if (colon > localcopy) {
115 slash = strchr(localcopy, '/');
118 protocol = localcopy;
123 disp->hostname = *hostname ? dupstr(hostname) : NULL;
126 disp->unixdomain = (!strcmp(protocol, "local") ||
127 !strcmp(protocol, "unix"));
128 else if (!*hostname || !strcmp(hostname, "unix"))
129 disp->unixdomain = platform_uses_x11_unix_by_default;
131 disp->unixdomain = FALSE;
133 if (!disp->hostname && !disp->unixdomain)
134 disp->hostname = dupstr("localhost");
136 disp->unixsocketpath = NULL;
142 * Look up the display hostname, if we need to.
144 if (disp->unixdomain) {
145 disp->addr = platform_get_x11_unix_address(disp->unixsocketpath,
147 if (disp->unixsocketpath)
148 disp->realhost = dupstr(disp->unixsocketpath);
150 disp->realhost = dupprintf("unix:%d", disp->displaynum);
155 disp->port = 6000 + disp->displaynum;
156 disp->addr = name_lookup(disp->hostname, disp->port,
157 &disp->realhost, cfg, ADDRTYPE_UNSPEC);
159 if ((err = sk_addr_error(disp->addr)) != NULL) {
160 sk_addr_free(disp->addr);
161 sfree(disp->hostname);
162 sfree(disp->unixsocketpath);
163 return NULL; /* FIXME: report an error */
168 * Invent the remote authorisation details.
170 if (authtype == X11_MIT) {
171 disp->remoteauthproto = X11_MIT;
173 /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
174 disp->remoteauthdata = snewn(16, unsigned char);
175 for (i = 0; i < 16; i++)
176 disp->remoteauthdata[i] = random_byte();
177 disp->remoteauthdatalen = 16;
179 disp->xdmseen = NULL;
181 assert(authtype == X11_XDM);
182 disp->remoteauthproto = X11_XDM;
184 /* XDM-AUTHORIZATION-1. Cookie size is 16 bytes; byte 8 is zero. */
185 disp->remoteauthdata = snewn(16, unsigned char);
186 for (i = 0; i < 16; i++)
187 disp->remoteauthdata[i] = (i == 8 ? 0 : random_byte());
188 disp->remoteauthdatalen = 16;
190 disp->xdmseen = newtree234(xdmseen_cmp);
192 disp->remoteauthprotoname = dupstr(x11_authnames[disp->remoteauthproto]);
193 disp->remoteauthdatastring = snewn(disp->remoteauthdatalen * 2 + 1, char);
194 for (i = 0; i < disp->remoteauthdatalen; i++)
195 sprintf(disp->remoteauthdatastring + i*2, "%02x",
196 disp->remoteauthdata[i]);
199 * Fetch the local authorisation details.
201 disp->localauthproto = X11_NO_AUTH;
202 disp->localauthdata = NULL;
203 disp->localauthdatalen = 0;
204 platform_get_x11_auth(disp, cfg);
209 void x11_free_display(struct X11Display *disp)
211 if (disp->xdmseen != NULL) {
212 struct XDMSeen *seen;
213 while ((seen = delpos234(disp->xdmseen, 0)) != NULL)
215 freetree234(disp->xdmseen);
217 sfree(disp->hostname);
218 sfree(disp->unixsocketpath);
219 if (disp->localauthdata)
220 memset(disp->localauthdata, 0, disp->localauthdatalen);
221 sfree(disp->localauthdata);
222 if (disp->remoteauthdata)
223 memset(disp->remoteauthdata, 0, disp->remoteauthdatalen);
224 sfree(disp->remoteauthdata);
225 sfree(disp->remoteauthprotoname);
226 sfree(disp->remoteauthdatastring);
227 sk_addr_free(disp->addr);
231 #define XDM_MAXSKEW 20*60 /* 20 minute clock skew should be OK */
233 static char *x11_verify(unsigned long peer_ip, int peer_port,
234 struct X11Display *disp, char *proto,
235 unsigned char *data, int dlen)
237 if (strcmp(proto, x11_authnames[disp->remoteauthproto]) != 0)
238 return "wrong authorisation protocol attempted";
239 if (disp->remoteauthproto == X11_MIT) {
240 if (dlen != disp->remoteauthdatalen)
241 return "MIT-MAGIC-COOKIE-1 data was wrong length";
242 if (memcmp(disp->remoteauthdata, data, dlen) != 0)
243 return "MIT-MAGIC-COOKIE-1 data did not match";
245 if (disp->remoteauthproto == X11_XDM) {
249 struct XDMSeen *seen, *ret;
252 return "XDM-AUTHORIZATION-1 data was wrong length";
254 return "cannot do XDM-AUTHORIZATION-1 without remote address data";
255 des_decrypt_xdmauth(disp->remoteauthdata+9, data, 24);
256 if (memcmp(disp->remoteauthdata, data, 8) != 0)
257 return "XDM-AUTHORIZATION-1 data failed check"; /* cookie wrong */
258 if (GET_32BIT_MSB_FIRST(data+8) != peer_ip)
259 return "XDM-AUTHORIZATION-1 data failed check"; /* IP wrong */
260 if ((int)GET_16BIT_MSB_FIRST(data+12) != peer_port)
261 return "XDM-AUTHORIZATION-1 data failed check"; /* port wrong */
262 t = GET_32BIT_MSB_FIRST(data+14);
263 for (i = 18; i < 24; i++)
264 if (data[i] != 0) /* zero padding wrong */
265 return "XDM-AUTHORIZATION-1 data failed check";
267 if (abs(t - tim) > XDM_MAXSKEW)
268 return "XDM-AUTHORIZATION-1 time stamp was too far out";
269 seen = snew(struct XDMSeen);
271 memcpy(seen->clientid, data+8, 6);
272 assert(disp->xdmseen != NULL);
273 ret = add234(disp->xdmseen, seen);
276 return "XDM-AUTHORIZATION-1 data replayed";
278 /* While we're here, purge entries too old to be replayed. */
280 seen = index234(disp->xdmseen, 0);
281 assert(seen != NULL);
282 if (t - seen->time <= XDM_MAXSKEW)
284 sfree(delpos234(disp->xdmseen, 0));
287 /* implement other protocols here if ever required */
291 void x11_get_auth_from_authfile(struct X11Display *disp,
292 const char *authfilename)
295 char *buf, *ptr, *str[4];
297 int family, protocol;
299 authfp = fopen(authfilename, "rb");
303 /* Records in .Xauthority contain four strings of up to 64K each */
304 buf = snewn(65537 * 4, char);
309 #define GET do { c = fgetc(authfp); if (c == EOF) goto done; c = (unsigned char)c; } while (0)
310 /* Expect a big-endian 2-byte number giving address family */
312 GET; family = (family << 8) | c;
313 /* Then expect four strings, each composed of a big-endian 2-byte
314 * length field followed by that many bytes of data */
316 for (i = 0; i < 4; i++) {
318 GET; len[i] = (len[i] << 8) | c;
320 for (j = 0; j < len[i]; j++) {
328 * Now we have a full X authority record in memory. See
329 * whether it matches the display we're trying to
332 * The details we've just read should be interpreted as
335 * - 'family' is the network address family used to
336 * connect to the display. 0 means IPv4; 6 means IPv6;
337 * 256 means Unix-domain sockets.
339 * - str[0] is the network address itself. For IPv4 and
340 * IPv6, this is a string of binary data of the
341 * appropriate length (respectively 4 and 16 bytes)
342 * representing the address in big-endian format, e.g.
343 * 7F 00 00 01 means IPv4 localhost. For Unix-domain
344 * sockets, this is the host name of the machine on
345 * which the Unix-domain display resides (so that an
346 * .Xauthority file on a shared file system can contain
347 * authority entries for Unix-domain displays on
348 * several machines without them clashing).
350 * - str[1] is the display number. I've no idea why
351 * .Xauthority stores this as a string when it has a
352 * perfectly good integer format, but there we go.
354 * - str[2] is the authorisation method, encoded as its
355 * canonical string name (i.e. "MIT-MAGIC-COOKIE-1",
356 * "XDM-AUTHORIZATION-1" or something we don't
359 * - str[3] is the actual authorisation data, stored in
363 if (disp->displaynum < 0 || disp->displaynum != atoi(str[1]))
364 continue; /* not the one */
366 for (protocol = 1; protocol < lenof(x11_authnames); protocol++)
367 if (!strcmp(str[2], x11_authnames[protocol]))
369 if (protocol == lenof(x11_authnames))
370 continue; /* don't recognise this protocol, look for another */
374 if (!disp->unixdomain &&
375 sk_addrtype(disp->addr) == ADDRTYPE_IPV4) {
377 sk_addrcopy(disp->addr, buf);
378 if (len[0] == 4 && !memcmp(str[0], buf, 4))
383 if (!disp->unixdomain &&
384 sk_addrtype(disp->addr) == ADDRTYPE_IPV6) {
386 sk_addrcopy(disp->addr, buf);
387 if (len[0] == 16 && !memcmp(str[0], buf, 16))
392 if (disp->unixdomain && !strcmp(disp->hostname, str[0]))
399 disp->localauthproto = protocol;
400 disp->localauthdata = snewn(len[3], unsigned char);
401 memcpy(disp->localauthdata, str[3], len[3]);
402 disp->localauthdatalen = len[3];
406 memset(buf, 0, 65537 * 4);
410 static void x11_log(Plug p, int type, SockAddr addr, int port,
411 const char *error_msg, int error_code)
413 /* We have no interface to the logging module here, so we drop these. */
416 static int x11_closing(Plug plug, const char *error_msg, int error_code,
419 struct X11Private *pr = (struct X11Private *) plug;
422 * We have no way to communicate down the forwarded connection,
423 * so if an error occurred on the socket, we just ignore it
424 * and treat it like a proper close.
431 static int x11_receive(Plug plug, int urgent, char *data, int len)
433 struct X11Private *pr = (struct X11Private *) plug;
435 if (sshfwd_write(pr->c, data, len) > 0) {
437 sk_set_frozen(pr->s, 1);
443 static void x11_sent(Plug plug, int bufsize)
445 struct X11Private *pr = (struct X11Private *) plug;
447 sshfwd_unthrottle(pr->c, bufsize);
451 * When setting up X forwarding, we should send the screen number
452 * from the specified local display. This function extracts it from
453 * the display string.
455 int x11_get_screen_number(char *display)
459 n = strcspn(display, ":");
462 n = strcspn(display, ".");
465 return atoi(display + n + 1);
469 * Called to set up the raw connection.
471 * Returns an error message, or NULL on success.
472 * also, fills the SocketsStructure
474 extern const char *x11_init(Socket *s, struct X11Display *disp, void *c,
475 const char *peeraddr, int peerport,
478 static const struct plug_function_table fn_table = {
487 struct X11Private *pr;
492 pr = snew(struct X11Private);
494 pr->auth_protocol = NULL;
498 pr->throttled = pr->throttle_override = 0;
501 pr->s = *s = new_connection(sk_addr_dup(disp->addr),
502 disp->realhost, disp->port,
503 0, 1, 0, 0, (Plug) pr, cfg);
504 if ((err = sk_socket_error(*s)) != NULL) {
510 * See if we can make sense of the peer address we were given.
515 4 == sscanf(peeraddr, "%d.%d.%d.%d", i+0, i+1, i+2, i+3)) {
516 pr->peer_ip = (i[0] << 24) | (i[1] << 16) | (i[2] << 8) | i[3];
517 pr->peer_port = peerport;
524 sk_set_private_ptr(*s, pr);
528 void x11_close(Socket s)
530 struct X11Private *pr;
533 pr = (struct X11Private *) sk_get_private_ptr(s);
534 if (pr->auth_protocol) {
535 sfree(pr->auth_protocol);
536 sfree(pr->auth_data);
544 void x11_unthrottle(Socket s)
546 struct X11Private *pr;
549 pr = (struct X11Private *) sk_get_private_ptr(s);
552 sk_set_frozen(s, pr->throttled || pr->throttle_override);
555 void x11_override_throttle(Socket s, int enable)
557 struct X11Private *pr;
560 pr = (struct X11Private *) sk_get_private_ptr(s);
562 pr->throttle_override = enable;
563 sk_set_frozen(s, pr->throttled || pr->throttle_override);
567 * Called to send data down the raw connection.
569 int x11_send(Socket s, char *data, int len)
571 struct X11Private *pr;
574 pr = (struct X11Private *) sk_get_private_ptr(s);
577 * Read the first packet.
579 while (len > 0 && pr->data_read < 12)
580 pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++);
581 if (pr->data_read < 12)
585 * If we have not allocated the auth_protocol and auth_data
586 * strings, do so now.
588 if (!pr->auth_protocol) {
589 pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6);
590 pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8);
591 pr->auth_psize = (pr->auth_plen + 3) & ~3;
592 pr->auth_dsize = (pr->auth_dlen + 3) & ~3;
593 /* Leave room for a terminating zero, to make our lives easier. */
594 pr->auth_protocol = snewn(pr->auth_psize + 1, char);
595 pr->auth_data = snewn(pr->auth_dsize, unsigned char);
599 * Read the auth_protocol and auth_data strings.
601 while (len > 0 && pr->data_read < 12 + pr->auth_psize)
602 pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
603 while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
604 pr->auth_data[pr->data_read++ - 12 -
605 pr->auth_psize] = (unsigned char) (len--, *data++);
606 if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
610 * If we haven't verified the authorisation, do so now.
615 pr->auth_protocol[pr->auth_plen] = '\0'; /* ASCIZ */
616 err = x11_verify(pr->peer_ip, pr->peer_port,
617 pr->disp, pr->auth_protocol,
618 pr->auth_data, pr->auth_dlen);
621 * If authorisation failed, construct and send an error
622 * packet, then terminate the connection.
627 unsigned char *reply;
629 message = dupprintf("PuTTY X11 proxy: %s", err);
630 msglen = strlen(message);
631 reply = snewn(8 + msglen+1 + 4, unsigned char); /* include zero */
632 msgsize = (msglen + 3) & ~3;
633 reply[0] = 0; /* failure */
634 reply[1] = msglen; /* length of reason string */
635 memcpy(reply + 2, pr->firstpkt + 2, 4); /* major/minor proto vsn */
636 PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */
637 memset(reply + 8, 0, msgsize);
638 memcpy(reply + 8, message, msglen);
639 sshfwd_write(pr->c, (char *)reply, 8 + msgsize);
648 * Now we know we're going to accept the connection. Strip
649 * the fake auth data, and optionally put real auth data in
653 char realauthdata[64];
655 int authstrlen = strlen(x11_authnames[pr->disp->localauthproto]);
656 int buflen = 0; /* initialise to placate optimiser */
657 static const char zeroes[4] = { 0,0,0,0 };
660 if (pr->disp->localauthproto == X11_MIT) {
661 assert(pr->disp->localauthdatalen <= lenof(realauthdata));
662 realauthlen = pr->disp->localauthdatalen;
663 memcpy(realauthdata, pr->disp->localauthdata, realauthlen);
664 } else if (pr->disp->localauthproto == X11_XDM &&
665 pr->disp->localauthdatalen == 16 &&
666 ((buf = sk_getxdmdata(s, &buflen))!=0)) {
668 realauthlen = (buflen+12+7) & ~7;
669 assert(realauthlen <= lenof(realauthdata));
670 memset(realauthdata, 0, realauthlen);
671 memcpy(realauthdata, pr->disp->localauthdata, 8);
672 memcpy(realauthdata+8, buf, buflen);
674 PUT_32BIT_MSB_FIRST(realauthdata+8+buflen, t);
675 des_encrypt_xdmauth(pr->disp->localauthdata+9,
676 (unsigned char *)realauthdata,
680 /* implement other auth methods here if required */
682 PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, authstrlen);
683 PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, realauthlen);
685 sk_write(s, (char *)pr->firstpkt, 12);
688 sk_write(s, x11_authnames[pr->disp->localauthproto],
690 sk_write(s, zeroes, 3 & (-authstrlen));
693 sk_write(s, realauthdata, realauthlen);
694 sk_write(s, zeroes, 3 & (-realauthlen));
701 * After initialisation, just copy data simply.
704 return sk_write(s, data, len);