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
);