From 1f974a47f89f8180b87eedd3343096bc03e74a23 Mon Sep 17 00:00:00 2001
From: Michael Brown <mbrown@fensystems.co.uk>
Date: Thu, 11 Feb 2021 13:39:34 +0000
Subject: [PATCH] [wim] Always process .wim image file last

The order of input files is undefined on a UEFI system, which could
potentially lead to a situation in which a file automatically
extracted from a .wim image takes priority over a file provided
explicitly.

This issue has not arisen in practice since wimboot is almost always
loaded by iPXE, and iPXE happens to preserve the order of downloaded
files within the virtual filesystem.

Fix by deferring processing of the .wim file until after all other
input files have been read.

Modify the automated test script to place the .wim download in between
two files that are both required for the test to pass.

Signed-off-by: Michael Brown <mbrown@fensystems.co.uk>
---
 src/efifile.c    | 22 ++++++++++++++--------
 src/main.c       | 24 ++++++++++++++++--------
 test/testwimboot |  2 +-
 3 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/src/efifile.c b/src/efifile.c
index 4e75d3f..a7a9cf3 100644
--- a/src/efifile.c
+++ b/src/efifile.c
@@ -145,6 +145,7 @@ void efi_extract ( EFI_HANDLE handle ) {
 		CHAR16 name[ VDISK_NAME_LEN + 1 /* WNUL */ ];
 	} __attribute__ (( packed )) info;
 	char name[ VDISK_NAME_LEN + 1 /* NUL */ ];
+	struct vdisk_file *wim = NULL;
 	struct vdisk_file *vfile;
 	EFI_FILE_PROTOCOL *root;
 	EFI_FILE_PROTOCOL *file;
@@ -212,17 +213,22 @@ void efi_extract ( EFI_HANDLE handle ) {
 		} else if ( wcscasecmp ( ( wname + ( wcslen ( wname ) - 4 ) ),
 					 L".wim" ) == 0 ) {
 			DBG ( "...found WIM file %ls\n", wname );
-			vdisk_patch_file ( vfile, patch_wim );
-			if ( ( ! bootmgfw ) &&
-			     ( bootmgfw = wim_add_file ( vfile, cmdline_index,
-							 bootmgfw_path,
-							 efi_bootarch() ) ) ) {
-				DBG ( "...extracted %ls\n", bootmgfw_path );
-			}
-			wim_add_files ( vfile, cmdline_index, efi_wim_paths );
+			wim = vfile;
 		}
 	}
 
+	/* Process WIM image */
+	if ( wim ) {
+		vdisk_patch_file ( wim, patch_wim );
+		if ( ( ! bootmgfw ) &&
+		     ( bootmgfw = wim_add_file ( wim, cmdline_index,
+						 bootmgfw_path,
+						 efi_bootarch() ) ) ) {
+			DBG ( "...extracted %ls\n", bootmgfw_path );
+		}
+		wim_add_files ( wim, cmdline_index, efi_wim_paths );
+	}
+
 	/* Check that we have a boot file */
 	if ( ! bootmgfw ) {
 		die ( "FATAL: no %ls or bootmgfw.efi found\n",
diff --git a/src/main.c b/src/main.c
index 67fc859..f7165b2 100644
--- a/src/main.c
+++ b/src/main.c
@@ -77,6 +77,9 @@ static const wchar_t *wim_paths[] = {
 /** bootmgr.exe file */
 static struct vdisk_file *bootmgr;
 
+/** WIM image file */
+static struct vdisk_file *bootwim;
+
 /** Minimal length of embedded bootmgr.exe */
 #define BOOTMGR_MIN_LEN 16384
 
@@ -364,14 +367,7 @@ static int add_file ( const char *name, void *data, size_t len ) {
 	} else if ( strcasecmp ( ( name + strlen ( name ) - 4 ),
 				 ".wim" ) == 0 ) {
 		DBG ( "...found WIM file %s\n", name );
-		vdisk_patch_file ( file, patch_wim );
-		if ( ( ! bootmgr ) &&
-		     ( bootmgr = wim_add_file ( file, cmdline_index,
-						bootmgr_path,
-						L"bootmgr.exe" ) ) ) {
-			DBG ( "...extracted bootmgr.exe\n" );
-		}
-		wim_add_files ( file, cmdline_index, wim_paths );
+		bootwim = file;
 	}
 
 	return 0;
@@ -447,6 +443,18 @@ int main ( void ) {
 	if ( cpio_extract ( initrd, initrd_len, add_file ) != 0 )
 		die ( "FATAL: could not extract initrd files\n" );
 
+	/* Process WIM image */
+	if ( bootwim ) {
+		vdisk_patch_file ( bootwim, patch_wim );
+		if ( ( ! bootmgr ) &&
+		     ( bootmgr = wim_add_file ( bootwim, cmdline_index,
+						bootmgr_path,
+						L"bootmgr.exe" ) ) ) {
+			DBG ( "...extracted bootmgr.exe\n" );
+		}
+		wim_add_files ( bootwim, cmdline_index, wim_paths );
+	}
+
 	/* Add INT 13 drive */
 	callback.drive = initialise_int13();
 
diff --git a/test/testwimboot b/test/testwimboot
index 642ee53..638abf8 100755
--- a/test/testwimboot
+++ b/test/testwimboot
@@ -59,6 +59,7 @@ def ipxe_script(uuid, version, arch, bootmgr, bcd, bootsdi, bootargs):
     #!ipxe
     kernel ../wimboot {bootargs}
     initrd -n qr.txt qr-{uuid}.txt qr.txt
+    initrd ../images/{version}/{arch}/sources/boot.wim boot.wim
     initrd ../winpeshl.ini winpeshl.ini
     """).lstrip()
     if bootmgr:
@@ -74,7 +75,6 @@ def ipxe_script(uuid, version, arch, bootmgr, bcd, bootsdi, bootargs):
         initrd ../images/{version}/{arch}/boot/boot.sdi boot.sdi
         """).lstrip()
     script += textwrap.dedent(f"""
-    initrd ../images/{version}/{arch}/sources/boot.wim boot.wim
     boot
     """).lstrip()
     return script