From 0bfc3978f4a6a10e4427fdab222b0e50c3c7283c Mon Sep 17 00:00:00 2001
From: Alberto Perez <aperezguevar@microsoft.com>
Date: Mon, 30 Jan 2023 14:52:15 -0600
Subject: [PATCH] Work around malformed path delimiters in file paths from DHCP

shim uses path delimiters to determine the file path for the second
stage.  Currently only / (slash) is detected, but some DHCP
implementations supply \ (backslash) as the path specifier.

This patch changes it to accept either delimiter.

Fixes issue #524.

Signed-off-by: Alberto Perez <aperezguevar@microsoft.com>
---
 netboot.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/netboot.c b/netboot.c
index cf5882c..832deec 100644
--- a/netboot.c
+++ b/netboot.c
@@ -263,7 +263,7 @@ static EFI_STATUS parseDhcp4()
 	UINT8 *dir = pkt_v4->BootpBootFile;
 
 	for (i = dir_len; i >= 0; i--) {
-		if (dir[i] == '/')
+		if ((dir[i] == '/') || (dir[i] == '\\'))
 			break;
 	}
 	dir_len = (i >= 0) ? i + 1 : 0;
@@ -277,6 +277,15 @@ static EFI_STATUS parseDhcp4()
 		strncpy(full_path, (CHAR8 *)dir, dir_len);
 		if (full_path[dir_len-1] == '/' && template[0] == '/')
 			full_path[dir_len-1] = '\0';
+		/*
+		 * If the path from DHCP is using backslash instead of slash,
+		 * accept that and use it in the template in the same position
+		 * as well.
+		 */
+		if (full_path[dir_len-1] == '\\' && template[0] == '/') {
+			full_path[dir_len-1] = '\0';
+			template[0] = '\\';
+		}
 	}
 	if (dir_len == 0 && dir[0] != '/' && template[0] == '/')
 		template_ofs++;
-- 
2.27.0

