fix to file writable in certain XP directories

2 files changed, 158 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 19b8961..db0af69 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2006-03-09  Vince Darley  <vincentdarley@sourceforge.net>
+
+	* win/tclWinFile.c: fix to 'file writable' in certain XP
+	directories.  Thanks to fvogel and jfg.  [Patch 1344540]
+
 2006-03-08  Don Porter  <dgp@users.sourceforge.net>
 
 	* generic/tclExecute.c:	Complete missing bit of TIP 215 implementation
diff --git a/win/tclWinFile.c b/win/tclWinFile.c
index f65e1c1..1284671 100644
--- a/win/tclWinFile.c
+++ b/win/tclWinFile.c
@@ -11,7 +11,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclWinFile.c,v 1.82 2006/01/12 16:19:04 vincentdarley Exp $
+ * RCS: @(#) $Id: tclWinFile.c,v 1.83 2006/03/09 11:30:29 vincentdarley Exp $
  */
 
 /* #define _WIN32_WINNT	0x0500 */
@@ -188,6 +188,7 @@ static int		NativeStat(CONST TCHAR *path, Tcl_StatBuf *statPtr,
 			    int checkLinks);
 static unsigned short	NativeStatMode(DWORD attr, int checkLinks, int isExec);
 static int		NativeIsExec(CONST TCHAR *path);
+static int 		NativeIsWritable(DWORD attr, CONST TCHAR *path);
 static int		NativeReadReparse(CONST TCHAR *LinkDirectory,
 			    REPARSE_DATA_BUFFER* buffer);
 static int		NativeWriteReparse(CONST TCHAR *LinkDirectory,
@@ -1546,7 +1547,7 @@ NativeAccess(
 	return -1;
     }
 
-    if ((mode & W_OK) && (attr & FILE_ATTRIBUTE_READONLY)) {
+    if ((mode & W_OK) && !NativeIsWritable(attr, nativePath)) {
 	/*
 	 * File is not writable.
 	 */
@@ -1789,6 +1790,156 @@ NativeIsExec(
 /*
  *----------------------------------------------------------------------
  *
+ * NativeIsWritable --
+ *
+ *     Determine if a path is writable. On Windows this requires more than a
+ *     simple read only flag check for directories because Windows uses this
+ *     as a flag to customize the folder options. [Bug 1193497]
+ *
+ * Results:
+ *     1 = writable, 0 = not.
+ *
+ * Side effects:
+ *     May smash the last error value (errors are just reported by this
+ *     function as non-writable files).
+ *
+ *----------------------------------------------------------------------
+ */
+static int
+NativeIsWritable(
+    DWORD attr,
+    CONST TCHAR *nativePath)
+{
+    BYTE *secDescPtr = 0;
+    DWORD secDescLen = 0;
+    HANDLE hToken = NULL;
+    BOOL isWritable = FALSE;
+
+    /*
+     * One time initialization, dynamically load Windows NT features
+     */
+
+    static const SECURITY_INFORMATION infoBits = OWNER_SECURITY_INFORMATION 
+      | GROUP_SECURITY_INFORMATION | DACL_SECURITY_INFORMATION;
+
+    static BOOL (WINAPI *getFileSecurityProc)(LPCSTR, SECURITY_INFORMATION, 
+      PSECURITY_DESCRIPTOR, DWORD, LPDWORD);
+    static BOOL (WINAPI *openProcessTokenProc)(HANDLE, DWORD, PHANDLE);
+    static BOOL (WINAPI *duplicateTokenProc)(HANDLE, SECURITY_IMPERSONATION_LEVEL, 
+      PHANDLE);
+    static VOID (WINAPI *mapGenericMaskProc)(PDWORD, PGENERIC_MAPPING);
+    static BOOL (WINAPI *accessCheckProc)(PSECURITY_DESCRIPTOR, HANDLE, DWORD, 
+      PGENERIC_MAPPING, PPRIVILEGE_SET, LPDWORD, LPDWORD, LPBOOL);
+
+    static int initialized = 0;
+
+    if (!initialized) {
+        TCL_DECLARE_MUTEX(writableMutex)
+        Tcl_MutexLock(&writableMutex);
+        if (!initialized) {
+            HINSTANCE hInstance = LoadLibrary("Advapi32");
+            if (hInstance != NULL) {
+                getFileSecurityProc = (BOOL (WINAPI *)(LPCSTR, 
+                  SECURITY_INFORMATION, PSECURITY_DESCRIPTOR, DWORD, LPDWORD))
+                  GetProcAddress(hInstance, tclWinProcs->useWide ? 
+                  "GetFileSecurityW" : "GetFileSecurityA");
+                openProcessTokenProc = (BOOL (WINAPI *)(HANDLE, DWORD, 
+                  PHANDLE)) GetProcAddress(hInstance, "OpenProcessToken");
+                duplicateTokenProc = (BOOL (WINAPI *)(HANDLE, 
+                  SECURITY_IMPERSONATION_LEVEL, PHANDLE)) 
+                  GetProcAddress(hInstance, "DuplicateToken");
+                mapGenericMaskProc = (VOID (WINAPI *)(PDWORD, 
+                  PGENERIC_MAPPING)) GetProcAddress(hInstance, 
+                  "MapGenericMask");
+                accessCheckProc = (BOOL (WINAPI *)(PSECURITY_DESCRIPTOR,
+                  HANDLE, DWORD, PGENERIC_MAPPING, PPRIVILEGE_SET, 
+                  LPDWORD, LPDWORD, LPBOOL)) GetProcAddress(hInstance, 
+                  "AccessCheck");
+                if (getFileSecurityProc && openProcessTokenProc 
+                  && duplicateTokenProc && mapGenericMaskProc 
+                  && accessCheckProc) {
+                    initialized = 1;
+                }
+            }
+            if (!initialized)
+                initialized = -1;
+        }
+        Tcl_MutexUnlock(&writableMutex);
+    }
+
+    /*
+     * Windows NT features not available, default back to readonly flag
+     */
+    if (initialized < 0)
+        return attr & FILE_ATTRIBUTE_READONLY;
+
+    /*
+     * Read the security descriptor for the file or directory. Note the
+     * first call obtains the size of the security descriptor.
+     */
+
+    if (!getFileSecurityProc(nativePath, infoBits, NULL, 0, &secDescLen)) {
+        if (GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
+            DWORD secDescLen2 = 0;
+            secDescPtr = (BYTE *) ckalloc(secDescLen);
+            if (!getFileSecurityProc(nativePath, infoBits, secDescPtr, 
+              secDescLen, &secDescLen2) 
+              || (secDescLen < secDescLen2)) {
+                goto done;
+            }
+        } else {
+            goto done;
+        }
+    }
+
+    /*
+     * Get the security identity of the process and (if successful) use it
+     * with the security descriptor of the file to find out if the file really
+     * is writable.
+     */
+    if (openProcessTokenProc(GetCurrentProcess(), TOKEN_DUPLICATE, &hToken)) {
+        HANDLE hIToken = NULL;
+        BOOL status = duplicateTokenProc(hToken, SecurityIdentification, 
+          &hIToken);
+
+        CloseHandle(hToken);
+        if (status) {
+            PRIVILEGE_SET privilegeSet;
+            DWORD privilegeSetLength = sizeof(privilegeSet);
+            DWORD granted; /* unused */
+            DWORD accessDesired = ACCESS_WRITE;
+
+            /* Initialize generic mapping structure to map all. */
+            GENERIC_MAPPING GenericMapping;
+            memset(&GenericMapping, 0xff, sizeof(GENERIC_MAPPING));
+            GenericMapping.GenericRead = ACCESS_READ;
+            GenericMapping.GenericWrite = ACCESS_WRITE;
+            GenericMapping.GenericExecute = 0;
+            GenericMapping.GenericAll = ACCESS_READ | ACCESS_WRITE;
+            mapGenericMaskProc(&accessDesired, &GenericMapping);
+
+            accessCheckProc(secDescPtr, hIToken, accessDesired,
+              &GenericMapping, &privilegeSet, &privilegeSetLength, &granted, 
+              &isWritable);
+            CloseHandle(hIToken);
+        }
+    }
+
+    /*
+     * Release any temporary space we may be using and convert the writability
+     * value into a boolean for return.
+     */
+
+  done:
+    if (secDescPtr) {
+        ckfree(secDescPtr);
+    }
+    return isWritable != 0;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
  * TclpObjChdir --
  *
  *	This function replaces the library version of chdir().