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 unsigned char fakedata
[64], realdata
[64];
31 int fakeproto
, realproto
;
37 const struct plug_function_table
*fn
;
38 /* the above variable absolutely *must* be the first in this structure */
39 unsigned char firstpkt
[12]; /* first X data packet */
42 unsigned char *auth_data
;
43 int data_read
, auth_plen
, auth_psize
, auth_dlen
, auth_dsize
;
45 int throttled
, throttle_override
;
46 unsigned long peer_ip
;
48 void *c
; /* data used by ssh.c */
52 static int xdmseen_cmp(void *a
, void *b
)
54 struct XDMSeen
*sa
= a
, *sb
= b
;
55 return sa
->time
> sb
->time ?
1 :
56 sa
->time
< sb
->time ?
-1 :
57 memcmp(sa
->clientid
, sb
->clientid
, sizeof(sa
->clientid
));
60 void *x11_invent_auth(char *proto
, int protomaxlen
,
61 char *data
, int datamaxlen
, int proto_id
)
63 struct X11Auth
*auth
= snew(struct X11Auth
);
67 if (proto_id
== X11_MIT
) {
68 auth
->fakeproto
= X11_MIT
;
70 /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
72 for (i
= 0; i
< 16; i
++)
73 auth
->fakedata
[i
] = random_byte();
76 assert(proto_id
== X11_XDM
);
77 auth
->fakeproto
= X11_XDM
;
79 /* XDM-AUTHORIZATION-1. Cookie size is 16 bytes; byte 8 is zero. */
81 for (i
= 0; i
< 16; i
++)
82 auth
->fakedata
[i
] = (i
== 8 ?
0 : random_byte());
83 auth
->xdmseen
= newtree234(xdmseen_cmp
);
86 /* Now format for the recipient. */
87 strncpy(proto
, x11_authnames
[auth
->fakeproto
], protomaxlen
);
89 for (i
= 0; i
< auth
->fakelen
; i
++)
90 sprintf(ourdata
+ strlen(ourdata
), "%02x", auth
->fakedata
[i
]);
91 strncpy(data
, ourdata
, datamaxlen
);
96 void x11_free_auth(void *authv
)
98 struct X11Auth
*auth
= (struct X11Auth
*)authv
;
101 if (auth
->xdmseen
!= NULL
) {
102 while ((seen
= delpos234(auth
->xdmseen
, 0)) != NULL
)
104 freetree234(auth
->xdmseen
);
110 * Fetch the real auth data for a given display string, and store
111 * it in an X11Auth structure. Returns NULL on success, or an error
114 void x11_get_real_auth(void *authv
, char *display
)
116 struct X11Auth
*auth
= (struct X11Auth
*)authv
;
118 auth
->realproto
= X11_NO_AUTH
; /* in case next call does nothing */
120 auth
->reallen
= sizeof(auth
->realdata
);
121 platform_get_x11_auth(display
, &auth
->realproto
,
122 auth
->realdata
, &auth
->reallen
);
125 #define XDM_MAXSKEW 20*60 /* 20 minute clock skew should be OK */
127 static char *x11_verify(unsigned long peer_ip
, int peer_port
,
128 struct X11Auth
*auth
, char *proto
,
129 unsigned char *data
, int dlen
)
131 if (strcmp(proto
, x11_authnames
[auth
->fakeproto
]) != 0)
132 return "wrong authentication protocol attempted";
133 if (auth
->fakeproto
== X11_MIT
) {
134 if (dlen
!= auth
->fakelen
)
135 return "MIT-MAGIC-COOKIE-1 data was wrong length";
136 if (memcmp(auth
->fakedata
, data
, dlen
) != 0)
137 return "MIT-MAGIC-COOKIE-1 data did not match";
139 if (auth
->fakeproto
== X11_XDM
) {
143 struct XDMSeen
*seen
, *ret
;
146 return "XDM-AUTHORIZATION-1 data was wrong length";
148 return "cannot do XDM-AUTHORIZATION-1 without remote address data";
149 des_decrypt_xdmauth(auth
->fakedata
+9, data
, 24);
150 if (memcmp(auth
->fakedata
, data
, 8) != 0)
151 return "XDM-AUTHORIZATION-1 data failed check"; /* cookie wrong */
152 if (GET_32BIT_MSB_FIRST(data
+8) != peer_ip
)
153 return "XDM-AUTHORIZATION-1 data failed check"; /* IP wrong */
154 if ((int)GET_16BIT_MSB_FIRST(data
+12) != peer_port
)
155 return "XDM-AUTHORIZATION-1 data failed check"; /* port wrong */
156 t
= GET_32BIT_MSB_FIRST(data
+14);
157 for (i
= 18; i
< 24; i
++)
158 if (data
[i
] != 0) /* zero padding wrong */
159 return "XDM-AUTHORIZATION-1 data failed check";
161 if (abs(t
- tim
) > XDM_MAXSKEW
)
162 return "XDM-AUTHORIZATION-1 time stamp was too far out";
163 seen
= snew(struct XDMSeen
);
165 memcpy(seen
->clientid
, data
+8, 6);
166 assert(auth
->xdmseen
!= NULL
);
167 ret
= add234(auth
->xdmseen
, seen
);
170 return "XDM-AUTHORIZATION-1 data replayed";
172 /* While we're here, purge entries too old to be replayed. */
174 seen
= index234(auth
->xdmseen
, 0);
175 assert(seen
!= NULL
);
176 if (t
- seen
->time
<= XDM_MAXSKEW
)
178 sfree(delpos234(auth
->xdmseen
, 0));
181 /* implement other protocols here if ever required */
185 static void x11_log(Plug p
, int type
, SockAddr addr
, int port
,
186 const char *error_msg
, int error_code
)
188 /* We have no interface to the logging module here, so we drop these. */
191 static int x11_closing(Plug plug
, const char *error_msg
, int error_code
,
194 struct X11Private
*pr
= (struct X11Private
*) plug
;
197 * We have no way to communicate down the forwarded connection,
198 * so if an error occurred on the socket, we just ignore it
199 * and treat it like a proper close.
206 static int x11_receive(Plug plug
, int urgent
, char *data
, int len
)
208 struct X11Private
*pr
= (struct X11Private
*) plug
;
210 if (sshfwd_write(pr
->c
, data
, len
) > 0) {
212 sk_set_frozen(pr
->s
, 1);
218 static void x11_sent(Plug plug
, int bufsize
)
220 struct X11Private
*pr
= (struct X11Private
*) plug
;
222 sshfwd_unthrottle(pr
->c
, bufsize
);
226 * When setting up X forwarding, we should send the screen number
227 * from the specified local display. This function extracts it from
228 * the display string.
230 int x11_get_screen_number(char *display
)
234 n
= strcspn(display
, ":");
237 n
= strcspn(display
, ".");
240 return atoi(display
+ n
+ 1);
243 /* Find the right display, returns an allocated string */
244 char *x11_display(const char *display
) {
246 if(!display
|| !*display
) {
247 /* try to find platform-specific local display */
248 if((ret
= platform_get_x_display())==0 || !*ret
)
249 /* plausible default for all platforms */
252 ret
= dupstr(display
);
254 /* no transport specified, use whatever we think is best */
255 char *s
= dupcat(platform_x11_best_transport
, ret
, (char *)0);
263 * Called to set up the raw connection.
265 * Returns an error message, or NULL on success.
266 * also, fills the SocketsStructure
268 const char *x11_init(Socket
* s
, char *display
, void *c
, void *auth
,
269 const char *peeraddr
, int peerport
, const Config
*cfg
)
271 static const struct plug_function_table fn_table
= {
282 char *dummy_realhost
;
285 struct X11Private
*pr
;
287 /* default display */
288 display
= x11_display(display
);
290 * Split up display name into host and display-number parts.
292 n
= strcspn(display
, ":");
293 assert(n
!= 0); /* x11_display() promises this */
295 displaynum
= atoi(display
+ n
+ 1);
297 displaynum
= 0; /* sensible default */
298 if (n
> sizeof(host
) - 1)
299 n
= sizeof(host
) - 1;
300 strncpy(host
, display
, n
);
304 if(!strcmp(host
, "unix")) {
305 /* use AF_UNIX sockets (doesn't make sense on all platforms) */
306 addr
= platform_get_x11_unix_address(displaynum
,
308 port
= 0; /* to show we are not confused */
310 port
= 6000 + displaynum
;
315 addr
= name_lookup(host
, port
, &dummy_realhost
, cfg
, ADDRTYPE_UNSPEC
);
316 if ((err
= sk_addr_error(addr
)) != NULL
) {
325 pr
= snew(struct X11Private
);
327 pr
->auth_protocol
= NULL
;
328 pr
->auth
= (struct X11Auth
*)auth
;
331 pr
->throttled
= pr
->throttle_override
= 0;
334 pr
->s
= *s
= new_connection(addr
, dummy_realhost
, port
,
335 0, 1, 0, 0, (Plug
) pr
, cfg
);
336 if ((err
= sk_socket_error(*s
)) != NULL
) {
342 * See if we can make sense of the peer address we were given.
347 4 == sscanf(peeraddr
, "%d.%d.%d.%d", i
+0, i
+1, i
+2, i
+3)) {
348 pr
->peer_ip
= (i
[0] << 24) | (i
[1] << 16) | (i
[2] << 8) | i
[3];
349 pr
->peer_port
= peerport
;
356 sk_set_private_ptr(*s
, pr
);
360 void x11_close(Socket s
)
362 struct X11Private
*pr
;
365 pr
= (struct X11Private
*) sk_get_private_ptr(s
);
366 if (pr
->auth_protocol
) {
367 sfree(pr
->auth_protocol
);
368 sfree(pr
->auth_data
);
376 void x11_unthrottle(Socket s
)
378 struct X11Private
*pr
;
381 pr
= (struct X11Private
*) sk_get_private_ptr(s
);
384 sk_set_frozen(s
, pr
->throttled
|| pr
->throttle_override
);
387 void x11_override_throttle(Socket s
, int enable
)
389 struct X11Private
*pr
;
392 pr
= (struct X11Private
*) sk_get_private_ptr(s
);
394 pr
->throttle_override
= enable
;
395 sk_set_frozen(s
, pr
->throttled
|| pr
->throttle_override
);
399 * Called to send data down the raw connection.
401 int x11_send(Socket s
, char *data
, int len
)
403 struct X11Private
*pr
;
406 pr
= (struct X11Private
*) sk_get_private_ptr(s
);
409 * Read the first packet.
411 while (len
> 0 && pr
->data_read
< 12)
412 pr
->firstpkt
[pr
->data_read
++] = (unsigned char) (len
--, *data
++);
413 if (pr
->data_read
< 12)
417 * If we have not allocated the auth_protocol and auth_data
418 * strings, do so now.
420 if (!pr
->auth_protocol
) {
421 pr
->auth_plen
= GET_16BIT(pr
->firstpkt
[0], pr
->firstpkt
+ 6);
422 pr
->auth_dlen
= GET_16BIT(pr
->firstpkt
[0], pr
->firstpkt
+ 8);
423 pr
->auth_psize
= (pr
->auth_plen
+ 3) & ~3;
424 pr
->auth_dsize
= (pr
->auth_dlen
+ 3) & ~3;
425 /* Leave room for a terminating zero, to make our lives easier. */
426 pr
->auth_protocol
= snewn(pr
->auth_psize
+ 1, char);
427 pr
->auth_data
= snewn(pr
->auth_dsize
, unsigned char);
431 * Read the auth_protocol and auth_data strings.
433 while (len
> 0 && pr
->data_read
< 12 + pr
->auth_psize
)
434 pr
->auth_protocol
[pr
->data_read
++ - 12] = (len
--, *data
++);
435 while (len
> 0 && pr
->data_read
< 12 + pr
->auth_psize
+ pr
->auth_dsize
)
436 pr
->auth_data
[pr
->data_read
++ - 12 -
437 pr
->auth_psize
] = (unsigned char) (len
--, *data
++);
438 if (pr
->data_read
< 12 + pr
->auth_psize
+ pr
->auth_dsize
)
442 * If we haven't verified the authentication, do so now.
447 pr
->auth_protocol
[pr
->auth_plen
] = '\0'; /* ASCIZ */
448 err
= x11_verify(pr
->peer_ip
, pr
->peer_port
,
449 pr
->auth
, pr
->auth_protocol
,
450 pr
->auth_data
, pr
->auth_dlen
);
453 * If authentication failed, construct and send an error
454 * packet, then terminate the connection.
459 unsigned char *reply
;
461 message
= dupprintf("PuTTY X11 proxy: %s", err
);
462 msglen
= strlen(message
);
463 reply
= snewn(8 + msglen
+1 + 4, unsigned char); /* include zero */
464 msgsize
= (msglen
+ 3) & ~3;
465 reply
[0] = 0; /* failure */
466 reply
[1] = msglen
; /* length of reason string */
467 memcpy(reply
+ 2, pr
->firstpkt
+ 2, 4); /* major/minor proto vsn */
468 PUT_16BIT(pr
->firstpkt
[0], reply
+ 6, msgsize
>> 2);/* data len */
469 memset(reply
+ 8, 0, msgsize
);
470 memcpy(reply
+ 8, message
, msglen
);
471 sshfwd_write(pr
->c
, (char *)reply
, 8 + msgsize
);
480 * Now we know we're going to accept the connection. Strip
481 * the fake auth data, and optionally put real auth data in
485 char realauthdata
[64];
487 int authstrlen
= strlen(x11_authnames
[pr
->auth
->realproto
]);
488 int buflen
= 0; /* initialise to placate optimiser */
489 static const char zeroes
[4] = { 0,0,0,0 };
492 if (pr
->auth
->realproto
== X11_MIT
) {
493 assert(pr
->auth
->reallen
<= lenof(realauthdata
));
494 realauthlen
= pr
->auth
->reallen
;
495 memcpy(realauthdata
, pr
->auth
->realdata
, realauthlen
);
496 } else if (pr
->auth
->realproto
== X11_XDM
&&
497 pr
->auth
->reallen
== 16 &&
498 ((buf
= sk_getxdmdata(s
, &buflen
))!=0)) {
500 realauthlen
= (buflen
+12+7) & ~7;
501 assert(realauthlen
<= lenof(realauthdata
));
502 memset(realauthdata
, 0, realauthlen
);
503 memcpy(realauthdata
, pr
->auth
->realdata
, 8);
504 memcpy(realauthdata
+8, buf
, buflen
);
506 PUT_32BIT_MSB_FIRST(realauthdata
+8+buflen
, t
);
507 des_encrypt_xdmauth(pr
->auth
->realdata
+9,
508 (unsigned char *)realauthdata
,
512 /* implement other auth methods here if required */
514 PUT_16BIT(pr
->firstpkt
[0], pr
->firstpkt
+ 6, authstrlen
);
515 PUT_16BIT(pr
->firstpkt
[0], pr
->firstpkt
+ 8, realauthlen
);
517 sk_write(s
, (char *)pr
->firstpkt
, 12);
520 sk_write(s
, x11_authnames
[pr
->auth
->realproto
], authstrlen
);
521 sk_write(s
, zeroes
, 3 & (-authstrlen
));
524 sk_write(s
, realauthdata
, realauthlen
);
525 sk_write(s
, zeroes
, 3 & (-realauthlen
));
532 * After initialisation, just copy data simply.
535 return sk_write(s
, data
, len
);