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"));
129 disp->unixdomain = platform_uses_x11_unix_by_default;
131 if (!disp->hostname && !disp->unixdomain)
132 disp->hostname = dupstr("localhost");
134 disp->unixsocketpath = NULL;
140 * Look up the display hostname, if we need to.
142 if (disp->unixdomain) {
143 disp->addr = platform_get_x11_unix_address(disp->unixsocketpath,
145 if (disp->unixsocketpath)
146 disp->realhost = dupstr(disp->unixsocketpath);
148 disp->realhost = dupprintf("unix:%d", disp->displaynum);
153 disp->port = 6000 + disp->displaynum;
154 disp->addr = name_lookup(disp->hostname, disp->port,
155 &disp->realhost, cfg, ADDRTYPE_UNSPEC);
157 if ((err = sk_addr_error(disp->addr)) != NULL) {
158 sk_addr_free(disp->addr);
159 sfree(disp->hostname);
160 sfree(disp->unixsocketpath);
161 return NULL; /* FIXME: report an error */
166 * Invent the remote authorisation details.
168 if (authtype == X11_MIT) {
169 disp->remoteauthproto = X11_MIT;
171 /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
172 disp->remoteauthdata = snewn(16, unsigned char);
173 for (i = 0; i < 16; i++)
174 disp->remoteauthdata[i] = random_byte();
175 disp->remoteauthdatalen = 16;
177 disp->xdmseen = NULL;
179 assert(authtype == X11_XDM);
180 disp->remoteauthproto = X11_XDM;
182 /* XDM-AUTHORIZATION-1. Cookie size is 16 bytes; byte 8 is zero. */
183 disp->remoteauthdata = snewn(16, unsigned char);
184 for (i = 0; i < 16; i++)
185 disp->remoteauthdata[i] = (i == 8 ? 0 : random_byte());
186 disp->remoteauthdatalen = 16;
188 disp->xdmseen = newtree234(xdmseen_cmp);
190 disp->remoteauthprotoname = dupstr(x11_authnames[disp->remoteauthproto]);
191 disp->remoteauthdatastring = snewn(disp->remoteauthdatalen * 2 + 1, char);
192 for (i = 0; i < disp->remoteauthdatalen; i++)
193 sprintf(disp->remoteauthdatastring + i*2, "%02x",
194 disp->remoteauthdata[i]);
197 * Fetch the local authorisation details.
199 disp->localauthproto = X11_NO_AUTH;
200 disp->localauthdata = NULL;
201 disp->localauthdatalen = 0;
202 platform_get_x11_auth(disp, cfg);
207 void x11_free_display(struct X11Display *disp)
209 if (disp->xdmseen != NULL) {
210 struct XDMSeen *seen;
211 while ((seen = delpos234(disp->xdmseen, 0)) != NULL)
213 freetree234(disp->xdmseen);
215 sfree(disp->hostname);
216 sfree(disp->unixsocketpath);
217 if (disp->localauthdata)
218 memset(disp->localauthdata, 0, disp->localauthdatalen);
219 sfree(disp->localauthdata);
220 if (disp->remoteauthdata)
221 memset(disp->remoteauthdata, 0, disp->remoteauthdatalen);
222 sfree(disp->remoteauthdata);
223 sfree(disp->remoteauthprotoname);
224 sfree(disp->remoteauthdatastring);
225 sk_addr_free(disp->addr);
229 #define XDM_MAXSKEW 20*60 /* 20 minute clock skew should be OK */
231 static char *x11_verify(unsigned long peer_ip, int peer_port,
232 struct X11Display *disp, char *proto,
233 unsigned char *data, int dlen)
235 if (strcmp(proto, x11_authnames[disp->remoteauthproto]) != 0)
236 return "wrong authorisation protocol attempted";
237 if (disp->remoteauthproto == X11_MIT) {
238 if (dlen != disp->remoteauthdatalen)
239 return "MIT-MAGIC-COOKIE-1 data was wrong length";
240 if (memcmp(disp->remoteauthdata, data, dlen) != 0)
241 return "MIT-MAGIC-COOKIE-1 data did not match";
243 if (disp->remoteauthproto == X11_XDM) {
247 struct XDMSeen *seen, *ret;
250 return "XDM-AUTHORIZATION-1 data was wrong length";
252 return "cannot do XDM-AUTHORIZATION-1 without remote address data";
253 des_decrypt_xdmauth(disp->remoteauthdata+9, data, 24);
254 if (memcmp(disp->remoteauthdata, data, 8) != 0)
255 return "XDM-AUTHORIZATION-1 data failed check"; /* cookie wrong */
256 if (GET_32BIT_MSB_FIRST(data+8) != peer_ip)
257 return "XDM-AUTHORIZATION-1 data failed check"; /* IP wrong */
258 if ((int)GET_16BIT_MSB_FIRST(data+12) != peer_port)
259 return "XDM-AUTHORIZATION-1 data failed check"; /* port wrong */
260 t = GET_32BIT_MSB_FIRST(data+14);
261 for (i = 18; i < 24; i++)
262 if (data[i] != 0) /* zero padding wrong */
263 return "XDM-AUTHORIZATION-1 data failed check";
265 if (abs(t - tim) > XDM_MAXSKEW)
266 return "XDM-AUTHORIZATION-1 time stamp was too far out";
267 seen = snew(struct XDMSeen);
269 memcpy(seen->clientid, data+8, 6);
270 assert(disp->xdmseen != NULL);
271 ret = add234(disp->xdmseen, seen);
274 return "XDM-AUTHORIZATION-1 data replayed";
276 /* While we're here, purge entries too old to be replayed. */
278 seen = index234(disp->xdmseen, 0);
279 assert(seen != NULL);
280 if (t - seen->time <= XDM_MAXSKEW)
282 sfree(delpos234(disp->xdmseen, 0));
285 /* implement other protocols here if ever required */
289 void x11_get_auth_from_authfile(struct X11Display *disp,
290 const char *authfilename)
293 char *buf, *ptr, *str[4];
295 int family, protocol;
297 authfp = fopen(authfilename, "rb");
301 /* Records in .Xauthority contain four strings of up to 64K each */
302 buf = snewn(65537 * 4, char);
307 #define GET do { c = fgetc(authfp); if (c == EOF) goto done; c = (unsigned char)c; } while (0)
308 /* Expect a big-endian 2-byte number giving address family */
310 GET; family = (family << 8) | c;
311 /* Then expect four strings, each composed of a big-endian 2-byte
312 * length field followed by that many bytes of data */
314 for (i = 0; i < 4; i++) {
316 GET; len[i] = (len[i] << 8) | c;
318 for (j = 0; j < len[i]; j++) {
326 * Now we have a full X authority record in memory. See
327 * whether it matches the display we're trying to
330 * The details we've just read should be interpreted as
333 * - 'family' is the network address family used to
334 * connect to the display. 0 means IPv4; 6 means IPv6;
335 * 256 means Unix-domain sockets.
337 * - str[0] is the network address itself. For IPv4 and
338 * IPv6, this is a string of binary data of the
339 * appropriate length (respectively 4 and 16 bytes)
340 * representing the address in big-endian format, e.g.
341 * 7F 00 00 01 means IPv4 localhost. For Unix-domain
342 * sockets, this is the host name of the machine on
343 * which the Unix-domain display resides (so that an
344 * .Xauthority file on a shared file system can contain
345 * authority entries for Unix-domain displays on
346 * several machines without them clashing).
348 * - str[1] is the display number. I've no idea why
349 * .Xauthority stores this as a string when it has a
350 * perfectly good integer format, but there we go.
352 * - str[2] is the authorisation method, encoded as its
353 * canonical string name (i.e. "MIT-MAGIC-COOKIE-1",
354 * "XDM-AUTHORIZATION-1" or something we don't
357 * - str[3] is the actual authorisation data, stored in
361 if (disp->displaynum < 0 || disp->displaynum != atoi(str[1]))
362 continue; /* not the one */
364 for (protocol = 1; protocol < lenof(x11_authnames); protocol++)
365 if (!strcmp(str[2], x11_authnames[protocol]))
367 if (protocol == lenof(x11_authnames))
368 continue; /* don't recognise this protocol, look for another */
372 if (!disp->unixdomain &&
373 sk_addrtype(disp->addr) == ADDRTYPE_IPV4) {
375 sk_addrcopy(disp->addr, buf);
376 if (len[0] == 4 && !memcmp(str[0], buf, 4))
381 if (!disp->unixdomain &&
382 sk_addrtype(disp->addr) == ADDRTYPE_IPV6) {
384 sk_addrcopy(disp->addr, buf);
385 if (len[0] == 16 && !memcmp(str[0], buf, 16))
390 if (disp->unixdomain && !strcmp(disp->hostname, str[0]))
397 disp->localauthproto = protocol;
398 disp->localauthdata = snewn(len[3], unsigned char);
399 memcpy(disp->localauthdata, str[3], len[3]);
400 disp->localauthdatalen = len[3];
404 memset(buf, 0, 65537 * 4);
408 static void x11_log(Plug p, int type, SockAddr addr, int port,
409 const char *error_msg, int error_code)
411 /* We have no interface to the logging module here, so we drop these. */
414 static int x11_closing(Plug plug, const char *error_msg, int error_code,
417 struct X11Private *pr = (struct X11Private *) plug;
420 * We have no way to communicate down the forwarded connection,
421 * so if an error occurred on the socket, we just ignore it
422 * and treat it like a proper close.
429 static int x11_receive(Plug plug, int urgent, char *data, int len)
431 struct X11Private *pr = (struct X11Private *) plug;
433 if (sshfwd_write(pr->c, data, len) > 0) {
435 sk_set_frozen(pr->s, 1);
441 static void x11_sent(Plug plug, int bufsize)
443 struct X11Private *pr = (struct X11Private *) plug;
445 sshfwd_unthrottle(pr->c, bufsize);
449 * When setting up X forwarding, we should send the screen number
450 * from the specified local display. This function extracts it from
451 * the display string.
453 int x11_get_screen_number(char *display)
457 n = strcspn(display, ":");
460 n = strcspn(display, ".");
463 return atoi(display + n + 1);
467 * Called to set up the raw connection.
469 * Returns an error message, or NULL on success.
470 * also, fills the SocketsStructure
472 extern const char *x11_init(Socket *s, struct X11Display *disp, void *c,
473 const char *peeraddr, int peerport,
476 static const struct plug_function_table fn_table = {
485 struct X11Private *pr;
490 pr = snew(struct X11Private);
492 pr->auth_protocol = NULL;
496 pr->throttled = pr->throttle_override = 0;
499 pr->s = *s = new_connection(sk_addr_dup(disp->addr),
500 disp->realhost, disp->port,
501 0, 1, 0, 0, (Plug) pr, cfg);
502 if ((err = sk_socket_error(*s)) != NULL) {
508 * See if we can make sense of the peer address we were given.
513 4 == sscanf(peeraddr, "%d.%d.%d.%d", i+0, i+1, i+2, i+3)) {
514 pr->peer_ip = (i[0] << 24) | (i[1] << 16) | (i[2] << 8) | i[3];
515 pr->peer_port = peerport;
522 sk_set_private_ptr(*s, pr);
526 void x11_close(Socket s)
528 struct X11Private *pr;
531 pr = (struct X11Private *) sk_get_private_ptr(s);
532 if (pr->auth_protocol) {
533 sfree(pr->auth_protocol);
534 sfree(pr->auth_data);
542 void x11_unthrottle(Socket s)
544 struct X11Private *pr;
547 pr = (struct X11Private *) sk_get_private_ptr(s);
550 sk_set_frozen(s, pr->throttled || pr->throttle_override);
553 void x11_override_throttle(Socket s, int enable)
555 struct X11Private *pr;
558 pr = (struct X11Private *) sk_get_private_ptr(s);
560 pr->throttle_override = enable;
561 sk_set_frozen(s, pr->throttled || pr->throttle_override);
565 * Called to send data down the raw connection.
567 int x11_send(Socket s, char *data, int len)
569 struct X11Private *pr;
572 pr = (struct X11Private *) sk_get_private_ptr(s);
575 * Read the first packet.
577 while (len > 0 && pr->data_read < 12)
578 pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++);
579 if (pr->data_read < 12)
583 * If we have not allocated the auth_protocol and auth_data
584 * strings, do so now.
586 if (!pr->auth_protocol) {
587 pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6);
588 pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8);
589 pr->auth_psize = (pr->auth_plen + 3) & ~3;
590 pr->auth_dsize = (pr->auth_dlen + 3) & ~3;
591 /* Leave room for a terminating zero, to make our lives easier. */
592 pr->auth_protocol = snewn(pr->auth_psize + 1, char);
593 pr->auth_data = snewn(pr->auth_dsize, unsigned char);
597 * Read the auth_protocol and auth_data strings.
599 while (len > 0 && pr->data_read < 12 + pr->auth_psize)
600 pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
601 while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
602 pr->auth_data[pr->data_read++ - 12 -
603 pr->auth_psize] = (unsigned char) (len--, *data++);
604 if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
608 * If we haven't verified the authorisation, do so now.
613 pr->auth_protocol[pr->auth_plen] = '\0'; /* ASCIZ */
614 err = x11_verify(pr->peer_ip, pr->peer_port,
615 pr->disp, pr->auth_protocol,
616 pr->auth_data, pr->auth_dlen);
619 * If authorisation failed, construct and send an error
620 * packet, then terminate the connection.
625 unsigned char *reply;
627 message = dupprintf("PuTTY X11 proxy: %s", err);
628 msglen = strlen(message);
629 reply = snewn(8 + msglen+1 + 4, unsigned char); /* include zero */
630 msgsize = (msglen + 3) & ~3;
631 reply[0] = 0; /* failure */
632 reply[1] = msglen; /* length of reason string */
633 memcpy(reply + 2, pr->firstpkt + 2, 4); /* major/minor proto vsn */
634 PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */
635 memset(reply + 8, 0, msgsize);
636 memcpy(reply + 8, message, msglen);
637 sshfwd_write(pr->c, (char *)reply, 8 + msgsize);
646 * Now we know we're going to accept the connection. Strip
647 * the fake auth data, and optionally put real auth data in
651 char realauthdata[64];
653 int authstrlen = strlen(x11_authnames[pr->disp->localauthproto]);
654 int buflen = 0; /* initialise to placate optimiser */
655 static const char zeroes[4] = { 0,0,0,0 };
658 if (pr->disp->localauthproto == X11_MIT) {
659 assert(pr->disp->localauthdatalen <= lenof(realauthdata));
660 realauthlen = pr->disp->localauthdatalen;
661 memcpy(realauthdata, pr->disp->localauthdata, realauthlen);
662 } else if (pr->disp->localauthproto == X11_XDM &&
663 pr->disp->localauthdatalen == 16 &&
664 ((buf = sk_getxdmdata(s, &buflen))!=0)) {
666 realauthlen = (buflen+12+7) & ~7;
667 assert(realauthlen <= lenof(realauthdata));
668 memset(realauthdata, 0, realauthlen);
669 memcpy(realauthdata, pr->disp->localauthdata, 8);
670 memcpy(realauthdata+8, buf, buflen);
672 PUT_32BIT_MSB_FIRST(realauthdata+8+buflen, t);
673 des_encrypt_xdmauth(pr->disp->localauthdata+9,
674 (unsigned char *)realauthdata,
678 /* implement other auth methods here if required */
680 PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, authstrlen);
681 PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, realauthlen);
683 sk_write(s, (char *)pr->firstpkt, 12);
686 sk_write(s, x11_authnames[pr->disp->localauthproto],
688 sk_write(s, zeroes, 3 & (-authstrlen));
691 sk_write(s, realauthdata, realauthlen);
692 sk_write(s, zeroes, 3 & (-realauthlen));
699 * After initialisation, just copy data simply.
702 return sk_write(s, data, len);