2 * Platform-independent bits of X11 forwarding.
14 #define GET_32BIT_LSB_FIRST(cp) \
15 (((unsigned long)(unsigned char)(cp)[0]) | \
16 ((unsigned long)(unsigned char)(cp)[1] << 8) | \
17 ((unsigned long)(unsigned char)(cp)[2] << 16) | \
18 ((unsigned long)(unsigned char)(cp)[3] << 24))
20 #define PUT_32BIT_LSB_FIRST(cp, value) ( \
21 (cp)[0] = (char)(value), \
22 (cp)[1] = (char)((value) >> 8), \
23 (cp)[2] = (char)((value) >> 16), \
24 (cp)[3] = (char)((value) >> 24) )
26 #define GET_16BIT_LSB_FIRST(cp) \
27 (((unsigned long)(unsigned char)(cp)[0]) | \
28 ((unsigned long)(unsigned char)(cp)[1] << 8))
30 #define PUT_16BIT_LSB_FIRST(cp, value) ( \
31 (cp)[0] = (char)(value), \
32 (cp)[1] = (char)((value) >> 8) )
34 #define GET_32BIT_MSB_FIRST(cp) \
35 (((unsigned long)(unsigned char)(cp)[0] << 24) | \
36 ((unsigned long)(unsigned char)(cp)[1] << 16) | \
37 ((unsigned long)(unsigned char)(cp)[2] << 8) | \
38 ((unsigned long)(unsigned char)(cp)[3]))
40 #define PUT_32BIT_MSB_FIRST(cp, value) ( \
41 (cp)[0] = (char)((value) >> 24), \
42 (cp)[1] = (char)((value) >> 16), \
43 (cp)[2] = (char)((value) >> 8), \
44 (cp)[3] = (char)(value) )
46 #define GET_16BIT_MSB_FIRST(cp) \
47 (((unsigned long)(unsigned char)(cp)[0] << 8) | \
48 ((unsigned long)(unsigned char)(cp)[1]))
50 #define PUT_16BIT_MSB_FIRST(cp, value) ( \
51 (cp)[0] = (char)((value) >> 8), \
52 (cp)[1] = (char)(value) )
54 #define GET_16BIT(endian, cp) \
55 (endian=='B' ? GET_16BIT_MSB_FIRST(cp) : GET_16BIT_LSB_FIRST(cp))
57 #define PUT_16BIT(endian, cp, val) \
58 (endian=='B' ? PUT_16BIT_MSB_FIRST(cp, val) : PUT_16BIT_LSB_FIRST(cp, val))
60 const char *const x11_authnames[] = {
61 "", "MIT-MAGIC-COOKIE-1", "XDM-AUTHORIZATION-1"
66 unsigned char clientid[6];
70 unsigned char fakedata[64], realdata[64];
71 int fakeproto, realproto;
77 const struct plug_function_table *fn;
78 /* the above variable absolutely *must* be the first in this structure */
79 unsigned char firstpkt[12]; /* first X data packet */
82 unsigned char *auth_data;
83 int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize;
85 int throttled, throttle_override;
86 unsigned long peer_ip;
88 void *c; /* data used by ssh.c */
92 static int xdmseen_cmp(void *a, void *b)
94 struct XDMSeen *sa = a, *sb = b;
95 return sa->time > sb->time ? 1 :
96 sa->time < sb->time ? -1 :
97 memcmp(sa->clientid, sb->clientid, sizeof(sa->clientid));
100 void *x11_invent_auth(char *proto, int protomaxlen,
101 char *data, int datamaxlen, int proto_id)
103 struct X11Auth *auth = snew(struct X11Auth);
107 if (proto_id == X11_MIT) {
108 auth->fakeproto = X11_MIT;
110 /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
112 for (i = 0; i < 16; i++)
113 auth->fakedata[i] = random_byte();
115 assert(proto_id == X11_XDM);
116 auth->fakeproto = X11_XDM;
118 /* XDM-AUTHORIZATION-1. Cookie size is 16 bytes; byte 8 is zero. */
120 for (i = 0; i < 16; i++)
121 auth->fakedata[i] = (i == 8 ? 0 : random_byte());
122 auth->xdmseen = newtree234(xdmseen_cmp);
125 /* Now format for the recipient. */
126 strncpy(proto, x11_authnames[auth->fakeproto], protomaxlen);
128 for (i = 0; i < auth->fakelen; i++)
129 sprintf(ourdata + strlen(ourdata), "%02x", auth->fakedata[i]);
130 strncpy(data, ourdata, datamaxlen);
135 void x11_free_auth(void *authv)
137 struct X11Auth *auth = (struct X11Auth *)authv;
138 struct XDMSeen *seen;
140 if (auth->xdmseen != NULL) {
141 while ((seen = delpos234(auth->xdmseen, 0)) != NULL)
143 freetree234(auth->xdmseen);
149 * Fetch the real auth data for a given display string, and store
150 * it in an X11Auth structure. Returns NULL on success, or an error
153 void x11_get_real_auth(void *authv, char *display)
155 struct X11Auth *auth = (struct X11Auth *)authv;
157 auth->realproto = X11_NO_AUTH; /* in case next call does nothing */
159 auth->reallen = sizeof(auth->realdata);
160 platform_get_x11_auth(display, &auth->realproto,
161 auth->realdata, &auth->reallen);
164 #define XDM_MAXSKEW 20*60 /* 20 minute clock skew should be OK */
166 static char *x11_verify(unsigned long peer_ip, int peer_port,
167 struct X11Auth *auth, char *proto,
168 unsigned char *data, int dlen)
170 if (strcmp(proto, x11_authnames[auth->fakeproto]) != 0)
171 return "wrong authentication protocol attempted";
172 if (auth->fakeproto == X11_MIT) {
173 if (dlen != auth->fakelen)
174 return "MIT-MAGIC-COOKIE-1 data was wrong length";
175 if (memcmp(auth->fakedata, data, dlen) != 0)
176 return "MIT-MAGIC-COOKIE-1 data did not match";
178 if (auth->fakeproto == X11_XDM) {
182 struct XDMSeen *seen, *ret;
185 return "XDM-AUTHORIZATION-1 data was wrong length";
187 return "cannot do XDM-AUTHORIZATION-1 without remote address data";
188 des_decrypt_xdmauth(auth->fakedata+9, data, 24);
189 if (memcmp(auth->fakedata, data, 8) != 0)
190 return "XDM-AUTHORIZATION-1 data failed check"; /* cookie wrong */
191 if (GET_32BIT_MSB_FIRST(data+8) != peer_ip)
192 return "XDM-AUTHORIZATION-1 data failed check"; /* IP wrong */
193 if ((int)GET_16BIT_MSB_FIRST(data+12) != peer_port)
194 return "XDM-AUTHORIZATION-1 data failed check"; /* port wrong */
195 t = GET_32BIT_MSB_FIRST(data+14);
196 for (i = 18; i < 24; i++)
197 if (data[i] != 0) /* zero padding wrong */
198 return "XDM-AUTHORIZATION-1 data failed check";
200 if (abs(t - tim) > XDM_MAXSKEW)
201 return "XDM-AUTHORIZATION-1 time stamp was too far out";
202 seen = snew(struct XDMSeen);
204 memcpy(seen->clientid, data+8, 6);
205 assert(auth->xdmseen != NULL);
206 ret = add234(auth->xdmseen, seen);
209 return "XDM-AUTHORIZATION-1 data replayed";
211 /* While we're here, purge entries too old to be replayed. */
213 seen = index234(auth->xdmseen, 0);
214 assert(seen != NULL);
215 if (t - seen->time <= XDM_MAXSKEW)
217 sfree(delpos234(auth->xdmseen, 0));
220 /* implement other protocols here if ever required */
224 static void x11_log(Plug p, int type, SockAddr addr, int port,
225 const char *error_msg, int error_code)
227 /* We have no interface to the logging module here, so we drop these. */
230 static int x11_closing(Plug plug, const char *error_msg, int error_code,
233 struct X11Private *pr = (struct X11Private *) plug;
236 * We have no way to communicate down the forwarded connection,
237 * so if an error occurred on the socket, we just ignore it
238 * and treat it like a proper close.
245 static int x11_receive(Plug plug, int urgent, char *data, int len)
247 struct X11Private *pr = (struct X11Private *) plug;
249 if (sshfwd_write(pr->c, data, len) > 0) {
251 sk_set_frozen(pr->s, 1);
257 static void x11_sent(Plug plug, int bufsize)
259 struct X11Private *pr = (struct X11Private *) plug;
261 sshfwd_unthrottle(pr->c, bufsize);
265 * When setting up X forwarding, we should send the screen number
266 * from the specified local display. This function extracts it from
267 * the display string.
269 int x11_get_screen_number(char *display)
273 n = strcspn(display, ":");
276 n = strcspn(display, ".");
279 return atoi(display + n + 1);
282 /* Find the right display, returns an allocated string */
283 char *x11_display(const char *display) {
285 if(!display || !*display) {
286 /* try to find platform-specific local display */
287 if((ret = platform_get_x_display())==0)
288 /* plausible default for all platforms */
291 ret = dupstr(display);
293 /* no transport specified, use whatever we think is best */
294 char *s = dupcat(platform_x11_best_transport, ret, (char *)0);
302 * Called to set up the raw connection.
304 * Returns an error message, or NULL on success.
305 * also, fills the SocketsStructure
307 const char *x11_init(Socket * s, char *display, void *c, void *auth,
308 const char *peeraddr, int peerport, const Config *cfg)
310 static const struct plug_function_table fn_table = {
321 char *dummy_realhost;
324 struct X11Private *pr;
326 /* default display */
327 display = x11_display(display);
329 * Split up display name into host and display-number parts.
331 n = strcspn(display, ":");
332 assert(n != 0); /* x11_display() promises this */
334 displaynum = atoi(display + n + 1);
336 displaynum = 0; /* sensible default */
337 if (n > sizeof(host) - 1)
338 n = sizeof(host) - 1;
339 strncpy(host, display, n);
343 if(!strcmp(host, "unix")) {
344 /* use AF_UNIX sockets (doesn't make sense on all platforms) */
345 addr = platform_get_x11_unix_address(displaynum,
347 port = 0; /* to show we are not confused */
349 port = 6000 + displaynum;
354 addr = name_lookup(host, port, &dummy_realhost, cfg, ADDRTYPE_UNSPEC);
355 if ((err = sk_addr_error(addr)) != NULL) {
364 pr = snew(struct X11Private);
366 pr->auth_protocol = NULL;
367 pr->auth = (struct X11Auth *)auth;
370 pr->throttled = pr->throttle_override = 0;
373 pr->s = *s = new_connection(addr, dummy_realhost, port,
374 0, 1, 0, 0, (Plug) pr, cfg);
375 if ((err = sk_socket_error(*s)) != NULL) {
381 * See if we can make sense of the peer address we were given.
386 4 == sscanf(peeraddr, "%d.%d.%d.%d", i+0, i+1, i+2, i+3)) {
387 pr->peer_ip = (i[0] << 24) | (i[1] << 16) | (i[2] << 8) | i[3];
388 pr->peer_port = peerport;
395 sk_set_private_ptr(*s, pr);
399 void x11_close(Socket s)
401 struct X11Private *pr;
404 pr = (struct X11Private *) sk_get_private_ptr(s);
405 if (pr->auth_protocol) {
406 sfree(pr->auth_protocol);
407 sfree(pr->auth_data);
415 void x11_unthrottle(Socket s)
417 struct X11Private *pr;
420 pr = (struct X11Private *) sk_get_private_ptr(s);
423 sk_set_frozen(s, pr->throttled || pr->throttle_override);
426 void x11_override_throttle(Socket s, int enable)
428 struct X11Private *pr;
431 pr = (struct X11Private *) sk_get_private_ptr(s);
433 pr->throttle_override = enable;
434 sk_set_frozen(s, pr->throttled || pr->throttle_override);
438 * Called to send data down the raw connection.
440 int x11_send(Socket s, char *data, int len)
442 struct X11Private *pr;
445 pr = (struct X11Private *) sk_get_private_ptr(s);
448 * Read the first packet.
450 while (len > 0 && pr->data_read < 12)
451 pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++);
452 if (pr->data_read < 12)
456 * If we have not allocated the auth_protocol and auth_data
457 * strings, do so now.
459 if (!pr->auth_protocol) {
460 pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6);
461 pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8);
462 pr->auth_psize = (pr->auth_plen + 3) & ~3;
463 pr->auth_dsize = (pr->auth_dlen + 3) & ~3;
464 /* Leave room for a terminating zero, to make our lives easier. */
465 pr->auth_protocol = snewn(pr->auth_psize + 1, char);
466 pr->auth_data = snewn(pr->auth_dsize, unsigned char);
470 * Read the auth_protocol and auth_data strings.
472 while (len > 0 && pr->data_read < 12 + pr->auth_psize)
473 pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
474 while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
475 pr->auth_data[pr->data_read++ - 12 -
476 pr->auth_psize] = (unsigned char) (len--, *data++);
477 if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
481 * If we haven't verified the authentication, do so now.
486 pr->auth_protocol[pr->auth_plen] = '\0'; /* ASCIZ */
487 err = x11_verify(pr->peer_ip, pr->peer_port,
488 pr->auth, pr->auth_protocol,
489 pr->auth_data, pr->auth_dlen);
492 * If authentication failed, construct and send an error
493 * packet, then terminate the connection.
498 unsigned char *reply;
500 message = dupprintf("PuTTY X11 proxy: %s", err);
501 msglen = strlen(message);
502 reply = snewn(8 + msglen+1 + 4, unsigned char); /* include zero */
503 msgsize = (msglen + 3) & ~3;
504 reply[0] = 0; /* failure */
505 reply[1] = msglen; /* length of reason string */
506 memcpy(reply + 2, pr->firstpkt + 2, 4); /* major/minor proto vsn */
507 PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */
508 memset(reply + 8, 0, msgsize);
509 memcpy(reply + 8, message, msglen);
510 sshfwd_write(pr->c, (char *)reply, 8 + msgsize);
519 * Now we know we're going to accept the connection. Strip
520 * the fake auth data, and optionally put real auth data in
524 char realauthdata[64];
526 int authstrlen = strlen(x11_authnames[pr->auth->realproto]);
528 static const char zeroes[4] = { 0,0,0,0 };
531 if (pr->auth->realproto == X11_MIT) {
532 assert(pr->auth->reallen <= lenof(realauthdata));
533 realauthlen = pr->auth->reallen;
534 memcpy(realauthdata, pr->auth->realdata, realauthlen);
535 } else if (pr->auth->realproto == X11_XDM &&
536 pr->auth->reallen == 16 &&
537 ((buf = sk_getxdmdata(s, &buflen))!=0)) {
539 realauthlen = (buflen+12+7) & ~7;
540 assert(realauthlen <= lenof(realauthdata));
541 memset(realauthdata, 0, realauthlen);
542 memcpy(realauthdata, pr->auth->realdata, 8);
543 memcpy(realauthdata+8, buf, buflen);
545 PUT_32BIT_MSB_FIRST(realauthdata+8+buflen, t);
546 des_encrypt_xdmauth(pr->auth->realdata+9,
547 (unsigned char *)realauthdata,
551 /* implement other auth methods here if required */
553 PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, authstrlen);
554 PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, realauthlen);
556 sk_write(s, (char *)pr->firstpkt, 12);
559 sk_write(s, x11_authnames[pr->auth->realproto], authstrlen);
560 sk_write(s, zeroes, 3 & (-authstrlen));
563 sk_write(s, realauthdata, realauthlen);
564 sk_write(s, zeroes, 3 & (-realauthlen));
571 * After initialisation, just copy data simply.
574 return sk_write(s, data, len);