2 * Platform-independent bits of X11 forwarding.
13 #define GET_32BIT_LSB_FIRST(cp) \
14 (((unsigned long)(unsigned char)(cp)[0]) | \
15 ((unsigned long)(unsigned char)(cp)[1] << 8) | \
16 ((unsigned long)(unsigned char)(cp)[2] << 16) | \
17 ((unsigned long)(unsigned char)(cp)[3] << 24))
19 #define PUT_32BIT_LSB_FIRST(cp, value) ( \
20 (cp)[0] = (char)(value), \
21 (cp)[1] = (char)((value) >> 8), \
22 (cp)[2] = (char)((value) >> 16), \
23 (cp)[3] = (char)((value) >> 24) )
25 #define GET_16BIT_LSB_FIRST(cp) \
26 (((unsigned long)(unsigned char)(cp)[0]) | \
27 ((unsigned long)(unsigned char)(cp)[1] << 8))
29 #define PUT_16BIT_LSB_FIRST(cp, value) ( \
30 (cp)[0] = (char)(value), \
31 (cp)[1] = (char)((value) >> 8) )
33 #define GET_32BIT_MSB_FIRST(cp) \
34 (((unsigned long)(unsigned char)(cp)[0] << 24) | \
35 ((unsigned long)(unsigned char)(cp)[1] << 16) | \
36 ((unsigned long)(unsigned char)(cp)[2] << 8) | \
37 ((unsigned long)(unsigned char)(cp)[3]))
39 #define PUT_32BIT_MSB_FIRST(cp, value) ( \
40 (cp)[0] = (char)((value) >> 24), \
41 (cp)[1] = (char)((value) >> 16), \
42 (cp)[2] = (char)((value) >> 8), \
43 (cp)[3] = (char)(value) )
45 #define GET_16BIT_MSB_FIRST(cp) \
46 (((unsigned long)(unsigned char)(cp)[0] << 8) | \
47 ((unsigned long)(unsigned char)(cp)[1]))
49 #define PUT_16BIT_MSB_FIRST(cp, value) ( \
50 (cp)[0] = (char)((value) >> 8), \
51 (cp)[1] = (char)(value) )
53 #define GET_16BIT(endian, cp) \
54 (endian=='B' ? GET_16BIT_MSB_FIRST(cp) : GET_16BIT_LSB_FIRST(cp))
56 #define PUT_16BIT(endian, cp, val) \
57 (endian=='B' ? PUT_16BIT_MSB_FIRST(cp, val) : PUT_16BIT_LSB_FIRST(cp, val))
59 const char *const x11_authnames[] = {
60 "", "MIT-MAGIC-COOKIE-1", "XDM-AUTHORIZATION-1"
64 unsigned char fakedata[64], realdata[64];
65 int fakeproto, realproto;
70 const struct plug_function_table *fn;
71 /* the above variable absolutely *must* be the first in this structure */
72 unsigned char firstpkt[12]; /* first X data packet */
75 unsigned char *auth_data;
76 int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize;
78 int throttled, throttle_override;
79 unsigned long peer_ip;
81 void *c; /* data used by ssh.c */
85 void *x11_invent_auth(char *proto, int protomaxlen,
86 char *data, int datamaxlen, int proto_id)
88 struct X11Auth *auth = snew(struct X11Auth);
92 if (proto_id == X11_MIT) {
93 auth->fakeproto = X11_MIT;
95 /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
97 for (i = 0; i < 16; i++)
98 auth->fakedata[i] = random_byte();
100 assert(proto_id == X11_XDM);
101 auth->fakeproto = X11_XDM;
103 /* XDM-AUTHORIZATION-1. Cookie size is 16 bytes; byte 8 is zero. */
105 for (i = 0; i < 16; i++)
106 auth->fakedata[i] = (i == 8 ? 0 : random_byte());
109 /* Now format for the recipient. */
110 strncpy(proto, x11_authnames[auth->fakeproto], protomaxlen);
112 for (i = 0; i < auth->fakelen; i++)
113 sprintf(ourdata + strlen(ourdata), "%02x", auth->fakedata[i]);
114 strncpy(data, ourdata, datamaxlen);
119 void x11_free_auth(void *auth)
126 * Fetch the real auth data for a given display string, and store
127 * it in an X11Auth structure. Returns NULL on success, or an error
130 void x11_get_real_auth(void *authv, char *display)
132 struct X11Auth *auth = (struct X11Auth *)authv;
134 auth->realproto = X11_NO_AUTH; /* in case next call does nothing */
136 auth->reallen = sizeof(auth->realdata);
137 platform_get_x11_auth(display, &auth->realproto,
138 auth->realdata, &auth->reallen);
141 static char *x11_verify(unsigned long peer_ip, int peer_port,
142 struct X11Auth *auth, char *proto,
143 unsigned char *data, int dlen)
145 if (strcmp(proto, x11_authnames[auth->fakeproto]) != 0)
146 return "wrong authentication protocol attempted";
147 if (auth->fakeproto == X11_MIT) {
148 if (dlen != auth->fakelen)
149 return "MIT-MAGIC-COOKIE-1 data was wrong length";
150 if (memcmp(auth->fakedata, data, dlen) != 0)
151 return "MIT-MAGIC-COOKIE-1 data did not match";
153 if (auth->fakeproto == X11_XDM) {
159 return "XDM-AUTHORIZATION-1 data was wrong length";
161 return "cannot do XDM-AUTHORIZATION-1 without remote address data";
162 des_decrypt_xdmauth(auth->fakedata+9, data, 24);
163 if (memcmp(auth->fakedata, data, 8) != 0)
164 return "XDM-AUTHORIZATION-1 data failed check"; /* cookie wrong */
165 if (GET_32BIT_MSB_FIRST(data+8) != peer_ip)
166 return "XDM-AUTHORIZATION-1 data failed check"; /* IP wrong */
167 if ((int)GET_16BIT_MSB_FIRST(data+12) != peer_port)
168 return "XDM-AUTHORIZATION-1 data failed check"; /* port wrong */
169 t = GET_32BIT_MSB_FIRST(data+14);
170 for (i = 18; i < 24; i++)
171 if (data[i] != 0) /* zero padding wrong */
172 return "XDM-AUTHORIZATION-1 data failed check";
174 if (abs(t - tim) > 20*60) /* 20 minute clock skew should be OK */
175 return "XDM-AUTHORIZATION-1 time stamp was too far out";
177 /* implement other protocols here if ever required */
181 static int x11_closing(Plug plug, const char *error_msg, int error_code,
184 struct X11Private *pr = (struct X11Private *) plug;
187 * We have no way to communicate down the forwarded connection,
188 * so if an error occurred on the socket, we just ignore it
189 * and treat it like a proper close.
196 static int x11_receive(Plug plug, int urgent, char *data, int len)
198 struct X11Private *pr = (struct X11Private *) plug;
200 if (sshfwd_write(pr->c, data, len) > 0) {
202 sk_set_frozen(pr->s, 1);
208 static void x11_sent(Plug plug, int bufsize)
210 struct X11Private *pr = (struct X11Private *) plug;
212 sshfwd_unthrottle(pr->c, bufsize);
216 * When setting up X forwarding, we should send the screen number
217 * from the specified local display. This function extracts it from
218 * the display string.
220 int x11_get_screen_number(char *display)
224 n = strcspn(display, ":");
227 n = strcspn(display, ".");
230 return atoi(display + n + 1);
233 /* Find the right display, returns an allocated string */
234 char *x11_display(const char *display) {
236 if(!display || !*display) {
237 /* try to find platform-specific local display */
238 if(!(ret = platform_get_x_display()))
239 /* plausible default for all platforms */
242 ret = dupstr(display);
244 /* no transport specified, use whatever we think is best */
245 char *s = dupcat(platform_x11_best_transport, ret, (char *)0);
253 * Called to set up the raw connection.
255 * Returns an error message, or NULL on success.
256 * also, fills the SocketsStructure
258 const char *x11_init(Socket * s, char *display, void *c, void *auth,
259 const char *peeraddr, int peerport, const Config *cfg)
261 static const struct plug_function_table fn_table = {
271 char *dummy_realhost;
274 struct X11Private *pr;
276 /* default display */
277 display = x11_display(display);
279 * Split up display name into host and display-number parts.
281 n = strcspn(display, ":");
282 assert(n != 0); /* x11_display() promises this */
284 displaynum = atoi(display + n + 1);
286 displaynum = 0; /* sensible default */
287 if (n > sizeof(host) - 1)
288 n = sizeof(host) - 1;
289 strncpy(host, display, n);
293 if(!strcmp(host, "unix")) {
294 /* use AF_UNIX sockets (doesn't make sense on all platforms) */
295 addr = platform_get_x11_unix_address(displaynum,
297 port = 0; /* to show we are not confused */
299 port = 6000 + displaynum;
304 addr = name_lookup(host, port, &dummy_realhost, cfg, ADDRTYPE_UNSPEC);
305 if ((err = sk_addr_error(addr)) != NULL) {
314 pr = snew(struct X11Private);
316 pr->auth_protocol = NULL;
317 pr->auth = (struct X11Auth *)auth;
320 pr->throttled = pr->throttle_override = 0;
323 pr->s = *s = new_connection(addr, dummy_realhost, port,
324 0, 1, 0, 0, (Plug) pr, cfg);
325 if ((err = sk_socket_error(*s)) != NULL) {
331 * See if we can make sense of the peer address we were given.
336 4 == sscanf(peeraddr, "%d.%d.%d.%d", i+0, i+1, i+2, i+3)) {
337 pr->peer_ip = (i[0] << 24) | (i[1] << 16) | (i[2] << 8) | i[3];
338 pr->peer_port = peerport;
345 sk_set_private_ptr(*s, pr);
349 void x11_close(Socket s)
351 struct X11Private *pr;
354 pr = (struct X11Private *) sk_get_private_ptr(s);
355 if (pr->auth_protocol) {
356 sfree(pr->auth_protocol);
357 sfree(pr->auth_data);
365 void x11_unthrottle(Socket s)
367 struct X11Private *pr;
370 pr = (struct X11Private *) sk_get_private_ptr(s);
373 sk_set_frozen(s, pr->throttled || pr->throttle_override);
376 void x11_override_throttle(Socket s, int enable)
378 struct X11Private *pr;
381 pr = (struct X11Private *) sk_get_private_ptr(s);
383 pr->throttle_override = enable;
384 sk_set_frozen(s, pr->throttled || pr->throttle_override);
388 * Called to send data down the raw connection.
390 int x11_send(Socket s, char *data, int len)
392 struct X11Private *pr;
395 pr = (struct X11Private *) sk_get_private_ptr(s);
398 * Read the first packet.
400 while (len > 0 && pr->data_read < 12)
401 pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++);
402 if (pr->data_read < 12)
406 * If we have not allocated the auth_protocol and auth_data
407 * strings, do so now.
409 if (!pr->auth_protocol) {
410 pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6);
411 pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8);
412 pr->auth_psize = (pr->auth_plen + 3) & ~3;
413 pr->auth_dsize = (pr->auth_dlen + 3) & ~3;
414 /* Leave room for a terminating zero, to make our lives easier. */
415 pr->auth_protocol = snewn(pr->auth_psize + 1, char);
416 pr->auth_data = snewn(pr->auth_dsize, unsigned char);
420 * Read the auth_protocol and auth_data strings.
422 while (len > 0 && pr->data_read < 12 + pr->auth_psize)
423 pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
424 while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
425 pr->auth_data[pr->data_read++ - 12 -
426 pr->auth_psize] = (unsigned char) (len--, *data++);
427 if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
431 * If we haven't verified the authentication, do so now.
436 pr->auth_protocol[pr->auth_plen] = '\0'; /* ASCIZ */
437 err = x11_verify(pr->peer_ip, pr->peer_port,
438 pr->auth, pr->auth_protocol,
439 pr->auth_data, pr->auth_dlen);
442 * If authentication failed, construct and send an error
443 * packet, then terminate the connection.
448 unsigned char *reply;
450 message = dupprintf("PuTTY X11 proxy: %s", err);
451 msglen = strlen(message);
452 reply = snewn(8 + msglen+1 + 4, unsigned char); /* include zero */
453 msgsize = (msglen + 3) & ~3;
454 reply[0] = 0; /* failure */
455 reply[1] = msglen; /* length of reason string */
456 memcpy(reply + 2, pr->firstpkt + 2, 4); /* major/minor proto vsn */
457 PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */
458 memset(reply + 8, 0, msgsize);
459 memcpy(reply + 8, message, msglen);
460 sshfwd_write(pr->c, (char *)reply, 8 + msgsize);
469 * Now we know we're going to accept the connection. Strip
470 * the fake auth data, and optionally put real auth data in
474 char realauthdata[64];
476 int authstrlen = strlen(x11_authnames[pr->auth->realproto]);
479 static const char zeroes[4] = { 0,0,0,0 };
481 if (pr->auth->realproto == X11_MIT) {
482 assert(pr->auth->reallen <= lenof(realauthdata));
483 realauthlen = pr->auth->reallen;
484 memcpy(realauthdata, pr->auth->realdata, realauthlen);
485 } else if (pr->auth->realproto == X11_XDM &&
486 pr->auth->reallen == 16 &&
487 sk_getxdmdata(s, &ip, &port)) {
490 memset(realauthdata, 0, 24);
491 memcpy(realauthdata, pr->auth->realdata, 8);
492 PUT_32BIT_MSB_FIRST(realauthdata+8, ip);
493 PUT_16BIT_MSB_FIRST(realauthdata+12, port);
495 PUT_32BIT_MSB_FIRST(realauthdata+14, t);
496 des_encrypt_xdmauth(pr->auth->realdata+9,
497 (unsigned char *)realauthdata, 24);
499 /* implement other auth methods here if required */
501 PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, authstrlen);
502 PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, realauthlen);
504 sk_write(s, (char *)pr->firstpkt, 12);
507 sk_write(s, x11_authnames[pr->auth->realproto], authstrlen);
508 sk_write(s, zeroes, 3 & (-authstrlen));
511 sk_write(s, realauthdata, realauthlen);
512 sk_write(s, zeroes, 3 & (-realauthlen));
519 * After initialisation, just copy data simply.
522 return sk_write(s, data, len);