+void x11_free_display(struct X11Display *disp)
+{
+ if (disp->xdmseen != NULL) {
+ struct XDMSeen *seen;
+ while ((seen = delpos234(disp->xdmseen, 0)) != NULL)
+ sfree(seen);
+ freetree234(disp->xdmseen);
+ }
+ sfree(disp->hostname);
+ sfree(disp->unixsocketpath);
+ if (disp->localauthdata)
+ memset(disp->localauthdata, 0, disp->localauthdatalen);
+ sfree(disp->localauthdata);
+ if (disp->remoteauthdata)
+ memset(disp->remoteauthdata, 0, disp->remoteauthdatalen);
+ sfree(disp->remoteauthdata);
+ sfree(disp->remoteauthprotoname);
+ sfree(disp->remoteauthdatastring);
+ sk_addr_free(disp->addr);
+ sfree(disp);
+}
+
+#define XDM_MAXSKEW 20*60 /* 20 minute clock skew should be OK */
+
+static char *x11_verify(unsigned long peer_ip, int peer_port,
+ struct X11Display *disp, char *proto,
+ unsigned char *data, int dlen)
+{
+ if (strcmp(proto, x11_authnames[disp->remoteauthproto]) != 0)
+ return "wrong authorisation protocol attempted";
+ if (disp->remoteauthproto == X11_MIT) {
+ if (dlen != disp->remoteauthdatalen)
+ return "MIT-MAGIC-COOKIE-1 data was wrong length";
+ if (memcmp(disp->remoteauthdata, data, dlen) != 0)
+ return "MIT-MAGIC-COOKIE-1 data did not match";
+ }
+ if (disp->remoteauthproto == X11_XDM) {
+ unsigned long t;
+ time_t tim;
+ int i;
+ struct XDMSeen *seen, *ret;
+
+ if (dlen != 24)
+ return "XDM-AUTHORIZATION-1 data was wrong length";
+ if (peer_port == -1)
+ return "cannot do XDM-AUTHORIZATION-1 without remote address data";
+ des_decrypt_xdmauth(disp->remoteauthdata+9, data, 24);
+ if (memcmp(disp->remoteauthdata, data, 8) != 0)
+ return "XDM-AUTHORIZATION-1 data failed check"; /* cookie wrong */
+ if (GET_32BIT_MSB_FIRST(data+8) != peer_ip)
+ return "XDM-AUTHORIZATION-1 data failed check"; /* IP wrong */
+ if ((int)GET_16BIT_MSB_FIRST(data+12) != peer_port)
+ return "XDM-AUTHORIZATION-1 data failed check"; /* port wrong */
+ t = GET_32BIT_MSB_FIRST(data+14);
+ for (i = 18; i < 24; i++)
+ if (data[i] != 0) /* zero padding wrong */
+ return "XDM-AUTHORIZATION-1 data failed check";
+ tim = time(NULL);
+ if (abs(t - tim) > XDM_MAXSKEW)
+ return "XDM-AUTHORIZATION-1 time stamp was too far out";
+ seen = snew(struct XDMSeen);
+ seen->time = t;
+ memcpy(seen->clientid, data+8, 6);
+ assert(disp->xdmseen != NULL);
+ ret = add234(disp->xdmseen, seen);
+ if (ret != seen) {
+ sfree(seen);
+ return "XDM-AUTHORIZATION-1 data replayed";
+ }
+ /* While we're here, purge entries too old to be replayed. */
+ for (;;) {
+ seen = index234(disp->xdmseen, 0);
+ assert(seen != NULL);
+ if (t - seen->time <= XDM_MAXSKEW)
+ break;
+ sfree(delpos234(disp->xdmseen, 0));
+ }
+ }
+ /* implement other protocols here if ever required */
+ return NULL;
+}
+
+void x11_get_auth_from_authfile(struct X11Display *disp,
+ const char *authfilename)
+{
+ FILE *authfp;
+ char *buf, *ptr, *str[4];
+ int len[4];
+ int family, protocol;
+ int ideal_match = FALSE;
+ char *ourhostname = get_hostname();
+
+ /*
+ * Normally we should look for precisely the details specified in
+ * `disp'. However, there's an oddity when the display is local:
+ * displays like "localhost:0" usually have their details stored
+ * in a Unix-domain-socket record (even if there isn't actually a
+ * real Unix-domain socket available, as with OpenSSH's proxy X11
+ * server).
+ *
+ * This is apparently a fudge to get round the meaninglessness of
+ * "localhost" in a shared-home-directory context -- xauth entries
+ * for Unix-domain sockets already disambiguate this by storing
+ * the *local* hostname in the conveniently-blank hostname field,
+ * but IP "localhost" records couldn't do this. So, typically, an
+ * IP "localhost" entry in the auth database isn't present and if
+ * it were it would be ignored.
+ *
+ * However, we don't entirely trust that (say) Windows X servers
+ * won't rely on a straight "localhost" entry, bad idea though
+ * that is; so if we can't find a Unix-domain-socket entry we'll
+ * fall back to an IP-based entry if we can find one.
+ */
+ int localhost = !disp->unixdomain && sk_address_is_local(disp->addr);
+
+ authfp = fopen(authfilename, "rb");
+ if (!authfp)
+ return;
+
+ /* Records in .Xauthority contain four strings of up to 64K each */
+ buf = snewn(65537 * 4, char);
+
+ while (!ideal_match) {
+ int c, i, j, match = FALSE;
+
+#define GET do { c = fgetc(authfp); if (c == EOF) goto done; c = (unsigned char)c; } while (0)
+ /* Expect a big-endian 2-byte number giving address family */
+ GET; family = c;
+ GET; family = (family << 8) | c;
+ /* Then expect four strings, each composed of a big-endian 2-byte
+ * length field followed by that many bytes of data */
+ ptr = buf;
+ for (i = 0; i < 4; i++) {
+ GET; len[i] = c;
+ GET; len[i] = (len[i] << 8) | c;
+ str[i] = ptr;
+ for (j = 0; j < len[i]; j++) {
+ GET; *ptr++ = c;
+ }
+ *ptr++ = '\0';
+ }
+#undef GET
+
+ /*
+ * Now we have a full X authority record in memory. See
+ * whether it matches the display we're trying to
+ * authenticate to.
+ *
+ * The details we've just read should be interpreted as
+ * follows:
+ *
+ * - 'family' is the network address family used to
+ * connect to the display. 0 means IPv4; 6 means IPv6;
+ * 256 means Unix-domain sockets.
+ *
+ * - str[0] is the network address itself. For IPv4 and
+ * IPv6, this is a string of binary data of the
+ * appropriate length (respectively 4 and 16 bytes)
+ * representing the address in big-endian format, e.g.
+ * 7F 00 00 01 means IPv4 localhost. For Unix-domain
+ * sockets, this is the host name of the machine on
+ * which the Unix-domain display resides (so that an
+ * .Xauthority file on a shared file system can contain
+ * authority entries for Unix-domain displays on
+ * several machines without them clashing).
+ *
+ * - str[1] is the display number. I've no idea why
+ * .Xauthority stores this as a string when it has a
+ * perfectly good integer format, but there we go.
+ *
+ * - str[2] is the authorisation method, encoded as its
+ * canonical string name (i.e. "MIT-MAGIC-COOKIE-1",
+ * "XDM-AUTHORIZATION-1" or something we don't
+ * recognise).
+ *
+ * - str[3] is the actual authorisation data, stored in
+ * binary form.
+ */
+
+ if (disp->displaynum < 0 || disp->displaynum != atoi(str[1]))
+ continue; /* not the one */
+
+ for (protocol = 1; protocol < lenof(x11_authnames); protocol++)
+ if (!strcmp(str[2], x11_authnames[protocol]))
+ break;
+ if (protocol == lenof(x11_authnames))
+ continue; /* don't recognise this protocol, look for another */
+
+ switch (family) {
+ case 0: /* IPv4 */
+ if (!disp->unixdomain &&
+ sk_addrtype(disp->addr) == ADDRTYPE_IPV4) {
+ char buf[4];
+ sk_addrcopy(disp->addr, buf);
+ if (len[0] == 4 && !memcmp(str[0], buf, 4)) {
+ match = TRUE;
+ /* If this is a "localhost" entry, note it down
+ * but carry on looking for a Unix-domain entry. */
+ ideal_match = !localhost;
+ }
+ }
+ break;
+ case 6: /* IPv6 */
+ if (!disp->unixdomain &&
+ sk_addrtype(disp->addr) == ADDRTYPE_IPV6) {
+ char buf[16];
+ sk_addrcopy(disp->addr, buf);
+ if (len[0] == 16 && !memcmp(str[0], buf, 16)) {
+ match = TRUE;
+ ideal_match = !localhost;
+ }
+ }
+ break;
+ case 256: /* Unix-domain / localhost */
+ if ((disp->unixdomain || localhost)
+ && ourhostname && !strcmp(ourhostname, str[0]))
+ /* A matching Unix-domain socket is always the best
+ * match. */
+ match = ideal_match = TRUE;
+ break;
+ }
+
+ if (match) {
+ /* Current best guess -- may be overridden if !ideal_match */
+ disp->localauthproto = protocol;
+ sfree(disp->localauthdata); /* free previous guess, if any */
+ disp->localauthdata = snewn(len[3], unsigned char);
+ memcpy(disp->localauthdata, str[3], len[3]);
+ disp->localauthdatalen = len[3];
+ }
+ }
+
+ done:
+ fclose(authfp);
+ memset(buf, 0, 65537 * 4);
+ sfree(buf);
+ sfree(ourhostname);
+}
+
+static void x11_log(Plug p, int type, SockAddr addr, int port,
+ const char *error_msg, int error_code)
+{
+ /* We have no interface to the logging module here, so we drop these. */
+}
+
+static int x11_closing(Plug plug, const char *error_msg, int error_code,
+ int calling_back)
+{
+ struct X11Private *pr = (struct X11Private *) plug;
+
+ /*
+ * We have no way to communicate down the forwarded connection,
+ * so if an error occurred on the socket, we just ignore it
+ * and treat it like a proper close.
+ */
+ sshfwd_close(pr->c);
+ x11_close(pr->s);