+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;
+
+ authfp = fopen(authfilename, "rb");
+ if (!authfp)
+ return;
+
+ /* Records in .Xauthority contain four strings of up to 64K each */
+ buf = snewn(65537 * 4, char);
+
+ while (1) {
+ int c, i, j;
+
+#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:
+ 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))
+ goto found;
+ }
+ break;
+ case 6:
+ 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))
+ goto found;
+ }
+ break;
+ case 256:
+ if (disp->unixdomain && !strcmp(disp->hostname, str[0]))
+ goto found;
+ break;
+ }
+ }
+
+ found:
+ disp->localauthproto = protocol;
+ 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);
+}
+
+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,