From 913e96c7a1c138973912eb4b133a27796fd59e2e Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers3@gmail.com>
Date: Wed, 15 Jan 2014 12:07:06 -0600
Subject: [PATCH] win32_apply.c:  Simplify and fix win32_create_file()

win32_create_file() can be simplified by using CREATE_NEW and attempting
to delete the existing file if it exists.

This commit also adds FILE_FLAG_OPEN_REPARSE_POINT to the CreateFile()
call.  This is the equivalent to the O_NOFOLLOW addition to the UNIX
version in the previous commit.

Note that MS has contradictory documentation for the combination of
CREATE_ALWAYS and FILE_FLAG_OPEN_REPARSE_POINT, which further supports
the CREATE_NEW method changed to in this commit.
---
 src/win32_apply.c | 123 ++++++++++++++++++++--------------------------
 1 file changed, 52 insertions(+), 71 deletions(-)

diff --git a/src/win32_apply.c b/src/win32_apply.c
index df74519d..af8a4ef9 100644
--- a/src/win32_apply.c
+++ b/src/win32_apply.c
@@ -81,58 +81,68 @@ win32_start_extract(const wchar_t *path, struct apply_ctx *ctx)
 	return 0;
 }
 
+/* Delete a non-directory file, working around Windows quirks.  */
+static BOOL
+win32_delete_file_wrapper(const wchar_t *path)
+{
+	DWORD err;
+	DWORD attrib;
+
+	if (DeleteFile(path))
+		return TRUE;
+
+	err = GetLastError();
+	attrib = GetFileAttributes(path);
+	if ((attrib != INVALID_FILE_ATTRIBUTES) &&
+	    (attrib & FILE_ATTRIBUTE_READONLY))
+	{
+		/* Try again with FILE_ATTRIBUTE_READONLY cleared.  */
+		attrib &= ~FILE_ATTRIBUTE_READONLY;
+		if (SetFileAttributes(path, attrib)) {
+			if (DeleteFile(path))
+				return TRUE;
+			else
+				err = GetLastError();
+		}
+	}
+
+	SetLastError(err);
+	return FALSE;
+}
+
+
 /* Create a normal file, overwriting one already present.  */
 static int
 win32_create_file(const wchar_t *path, struct apply_ctx *ctx, u64 *cookie_ret)
 {
 	HANDLE h;
-	unsigned retry_count = 0;
-	DWORD dwFlagsAndAttributes = FILE_FLAG_BACKUP_SEMANTICS;
 
+	/* Notes:
+	 *
+	 * WRITE_OWNER and WRITE_DAC privileges are required for some reason,
+	 * even through we're creating a new file.
+	 *
+	 * FILE_FLAG_OPEN_REPARSE_POINT is required to prevent an existing
+	 * reparse point from redirecting the creation of the new file
+	 * (potentially to an arbitrary location).
+	 *
+	 * CREATE_ALWAYS could be used instead of CREATE_NEW.  However, there
+	 * are quirks that would need to be handled (e.g. having to set
+	 * FILE_ATTRIBUTE_HIDDEN and/or FILE_ATTRIBUTE_SYSTEM if the existing
+	 * file had them specified, and/or having to clear
+	 * FILE_ATTRIBUTE_READONLY on the existing file).  It's simpler to just
+	 * call win32_delete_file_wrapper() to delete the existing file in such
+	 * a way that already handles the FILE_ATTRIBUTE_READONLY quirk.
+	 */
 retry:
-	/* WRITE_OWNER and WRITE_DAC privileges are required for some reason,
-	 * even through we're creating a new file.  */
-	h = CreateFile(path, WRITE_OWNER | WRITE_DAC, 0, NULL,
-		       CREATE_ALWAYS, dwFlagsAndAttributes, NULL);
+	h = CreateFile(path, WRITE_OWNER | WRITE_DAC, 0, NULL, CREATE_NEW,
+		       FILE_FLAG_BACKUP_SEMANTICS |
+				FILE_FLAG_OPEN_REPARSE_POINT, NULL);
 	if (h == INVALID_HANDLE_VALUE) {
-		/* File couldn't be created.  */
 		DWORD err = GetLastError();
-		if (err == ERROR_ACCESS_DENIED && retry_count == 0) {
 
-			/* Access denied error for the first time.  Try
-			 * adjusting file attributes.  */
-
-			/* Get attributes of the existing file.  */
-			DWORD attribs = GetFileAttributes(path);
-			if (attribs != INVALID_FILE_ATTRIBUTES &&
-			    (attribs & (FILE_ATTRIBUTE_HIDDEN |
-					FILE_ATTRIBUTE_SYSTEM |
-					FILE_ATTRIBUTE_READONLY)))
-			{
-				/* If the existing file has
-				 * FILE_ATTRIBUTE_HIDDEN and/or
-				 * FILE_ATTRIBUTE_SYSTEM, they must be set in
-				 * the call to CreateFile().  This is true even
-				 * when FILE_ATTRIBUTE_NORMAL was not specified,
-				 * contrary to the MS "documentation".  */
-				dwFlagsAndAttributes |= (attribs &
-							 (FILE_ATTRIBUTE_HIDDEN |
-							  FILE_ATTRIBUTE_SYSTEM));
-				/* If the existing file has
-				 * FILE_ATTRIBUTE_READONLY, it must be cleared
-				 * before attempting to create a new file over
-				 * it.  This is true even when the process has
-				 * the SE_RESTORE_NAME privilege and requested
-				 * the FILE_FLAG_BACKUP_SEMANTICS flag to
-				 * CreateFile().  */
-				if (attribs & FILE_ATTRIBUTE_READONLY) {
-					SetFileAttributes(path,
-							  attribs & ~FILE_ATTRIBUTE_READONLY);
-				}
-				retry_count++;
-				goto retry;
-			}
-		}
+		if (err == ERROR_FILE_EXISTS && win32_delete_file_wrapper(path))
+			goto retry;
 		set_errno_from_win32_error(err);
 		return WIMLIB_ERR_OPEN;
 	}
@@ -154,35 +164,6 @@ error:
 	return WIMLIB_ERR_MKDIR;
 }
 
-/* Delete a non-directory file, working around Windows quirks.  */
-static BOOL
-win32_delete_file_wrapper(const wchar_t *path)
-{
-	DWORD err;
-	DWORD attrib;
-
-	if (DeleteFile(path))
-		return TRUE;
-
-	err = GetLastError();
-	attrib = GetFileAttributes(path);
-	if ((attrib != INVALID_FILE_ATTRIBUTES) &&
-	    (attrib & FILE_ATTRIBUTE_READONLY))
-	{
-		/* Try again with FILE_ATTRIBUTE_READONLY cleared.  */
-		attrib &= ~FILE_ATTRIBUTE_READONLY;
-		if (SetFileAttributes(path, attrib)) {
-			if (DeleteFile(path))
-				return TRUE;
-			else
-				err = GetLastError();
-		}
-	}
-
-	SetLastError(err);
-	return FALSE;
-}
-
 static int
 win32_create_hardlink(const wchar_t *oldpath, const wchar_t *newpath,
 		      struct apply_ctx *ctx)
-- 
2.43.0