Revamp of the local X11 connection code. We now parse X display

strings more rigorously, and then we look up the local X authority
data in .Xauthority _ourself_ rather than delegating to an external
xauth program. This is (negligibly) more efficient on Unix, assuming
I haven't got it wrong in some subtle way, but its major benefit is
that we can now support X authority lookups on Windows as well
provided the user points us at an appropriate X authority file in
the standard format. A new Windows-specific config option has been
added for this purpose.

[originally from svn r8305]

windows/wincfg.c

@@ -377,4 +377,14 @@ void win_setup_config_box(struct controlbox *b, HWND *hwndp, int has_help,
      */
     if (!midsession || (protocol == PROT_SERIAL))
         ser_setup_config_box(b, midsession, 0x1F, 0x0F);
+
+    /*
+     * $XAUTHORITY is not reliable on Windows, so we provide a
+     * means to override it.
+     */
+    s = ctrl_getset(b, "Connection/SSH/X11", "x11", "X11 forwarding");
+    ctrl_filesel(s, "X authority file for local display", 't',
+		 NULL, FALSE, "Select X authority file",
+		 HELPCTX(ssh_tunnels_xauthority),
+		 dlg_stdfilesel_handler, I(offsetof(Config, xauthfile)));
 }

windows/winhelp.h

@@ -121,6 +121,7 @@
 #define WINHELP_CTX_translation_linedraw "translation.linedraw:config-linedraw"
 #define WINHELP_CTX_ssh_tunnels_x11 "ssh.tunnels.x11:config-ssh-x11"
 #define WINHELP_CTX_ssh_tunnels_x11auth "ssh.tunnels.x11auth:config-ssh-x11auth"
+#define WINHELP_CTX_ssh_tunnels_xauthority "ssh.tunnels.xauthority:config-ssh-xauthority"
 #define WINHELP_CTX_ssh_tunnels_portfwd "ssh.tunnels.portfwd:config-ssh-portfwd"
 #define WINHELP_CTX_ssh_tunnels_portfwd_localhost "ssh.tunnels.portfwd.localhost:config-ssh-portfwd-localhost"
 #define WINHELP_CTX_ssh_tunnels_portfwd_ipversion "ssh.tunnels.portfwd.ipversion:config-ssh-portfwd-address-family"

windows/winmisc.c

@@ -8,14 +8,6 @@
 
 OSVERSIONINFO osVersion;
 
-void platform_get_x11_auth(char *display, int *proto,
-                           unsigned char *data, int *datalen)
-{
-    /* We don't support this at all under Windows. */
-}
-
-const char platform_x11_best_transport[] = "localhost";
-
 char *platform_get_x_display(void) {
     /* We may as well check for DISPLAY in case it's useful. */
     return dupstr(getenv("DISPLAY"));

windows/winsftp.c

@@ -19,6 +19,12 @@ int get_userpass_input(prompts_t *p, unsigned char *in, int inlen)
     return ret;
 }
 
+void platform_get_x11_auth(struct X11Display *display, const Config *cfg)
+{
+    /* Do nothing, therefore no auth. */
+}
+const int platform_uses_x11_unix_by_default = TRUE;
+
 /* ----------------------------------------------------------------------
  * File access abstraction.
  */

windows/winx11.c

@@ -0,0 +1,18 @@
+/*
+ * winx11.c: fetch local auth data for X forwarding.
+ */
+
+#include <ctype.h>
+#include <assert.h>
+#include <stdlib.h>
+
+#include "putty.h"
+#include "ssh.h"
+
+void platform_get_x11_auth(struct X11Display *disp, const Config *cfg)
+{
+    if (cfg->xauthfile.path[0])
+	x11_get_auth_from_authfile(disp, cfg->xauthfile.path);
+}
+
+const int platform_uses_x11_unix_by_default = FALSE;