w32: Fix extended length path handling for UNC specified files.

* src/sysutils.c (_gpgrt_fname_to_wchar): Fix the extended length path
support for UNC file names.  Also add an envvar to disable the entire
extended length path support.
--

GnuPG-bug-id: 5754
Fixes-commit: a4a692fcf1ed128693ec6d64d5e3163775aad10b

With the last fix we fixed the extended length path support but it
also truned outa wrong implementaion of it for UNC.  Before the
previous patch the UNC support was already wrong but it exhibited
itself only when the requested UNC was already long.  The patch then
kicked in the support more often and in particular always if an UNC was
used (due to the new checking for backslashes and not just the
length).

To avoid further surprises we now have an envvar to disable that
support entirely.  But if should be correct now ;-).

1 files changed, 26 insertions, 4 deletions

diff --git a/src/sysutils.c b/src/sysutils.c
index 132f1d3..7bebd4b 100644
--- a/src/sysutils.c
+++ b/src/sysutils.c
@@ -263,15 +263,27 @@ _gpgrt_setenv (const char *name, const char *value, int overwrite)
 wchar_t *
 _gpgrt_fname_to_wchar (const char *fname)
 {
+  static int no_extlenpath;
   wchar_t *wname;
   wchar_t *wfullpath = NULL;
   int success = 0;
 
+  if (!no_extlenpath)
+    {
+      const char *s = getenv ("GPGRT_DISABLE_EXTLENPATH");
+      if (s && atoi (s))
+        no_extlenpath = 1;
+      else
+        no_extlenpath = -1;
+    }
+
   wname = _gpgrt_utf8_to_wchar (fname);
   if (!wname)
     return NULL;
 
-  if (!strncmp (fname, "\\\\?\\", 4))
+  if (no_extlenpath > 0)
+    success = 1; /* Extended length path support has been disabled.  */
+  else if (!strncmp (fname, "\\\\?\\", 4) || !strncmp (fname, "//?/", 4))
     success = 1; /* Already translated.  */
   else if (strpbrk (fname, "/\\") || wcslen (wname) > 60)
     {
@@ -285,10 +297,16 @@ _gpgrt_fname_to_wchar (const char *fname)
       if (!wfullpath)
         goto leave;
 
-      if (*fname == '\\' && fname[1] == '\\' && fname[2])
+      if (((*fname == '\\' && fname[1] == '\\')
+           ||(*fname == '/' && fname[1] == '/')) && fname[2])
         {
-          wcscpy (wfullpath, L"\\\\?\\UNC\\");
-          extralen = 8;
+          /* Note that the GFPN call below will append the UNC name
+           * and thus two leading backslashes.  However, for an
+           * extended length path only one backslash is expected after
+           * the prefix.  We handle this by replacing the first
+           * backslash with the C from UNC after the GFPN call.  */
+          wcscpy (wfullpath, L"\\\\?\\UN");
+          extralen = 6;
         }
       else
         {
@@ -319,6 +337,10 @@ _gpgrt_fname_to_wchar (const char *fname)
       _gpgrt_free_wchar (wname);
       wname = wfullpath;
       wfullpath = NULL;
+
+      if (extralen == 6)
+        wname[6] = 'C';  /* Replace first backslash - see above.  */
+
       /* Need to make sure that all slashes are mapped. */
       for (w = wname; *w; w++)
         if (*w == L'/')