From b5c3492f31a98f5ef0f9bec2c0665ad0b71ad5cb Mon Sep 17 00:00:00 2001
From: Sebastian Krahmer <[email protected]>
Date: Tue, 28 Nov 2017 17:24:38 +0800
Subject: [PATCH] AUDIT-0: http boot tracker bug

Fixing a memory leak in case of error, and a integer overflow, leading to a
heap overflow due to overly large chunk sizes.

We need to check against some maximum value, otherwise values like 0xffffffff
will eventually lead in the allocation functions to small sized buffers, since
the len is rounded up to the next reasonable alignment. The following memcpy
will then smash the heap, leading to RCE.

This is no big issue for pure http boot, since its going to execute an
untrusted kernel anyway, but it will break trusted boot scenarios, where only
signed code is allowed to be executed.

v2: Fix GCC 13 build failure (bsc#1201089)

Signed-off-by: Michael Chang <[email protected]>
---
 grub-core/net/efi/net.c | 4 +++-
 grub-core/net/http.c    | 5 ++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

--- a/grub-core/net/efi/net.c
+++ b/grub-core/net/efi/net.c
@@ -654,8 +654,10 @@
 
       rd = efi_net_interface (read, file, chunk, sz);
 
-      if (rd <= 0)
+      if (rd <= 0) {
+	grub_free (chunk);
 	return rd;
+      }
 
       if (buf)
 	{
--- a/grub-core/net/http.c
+++ b/grub-core/net/http.c
@@ -30,6 +30,7 @@
 GRUB_MOD_LICENSE ("GPLv3+");
 
 #define HTTP_PORT	((grub_uint16_t) 80)
+#define HTTP_MAX_CHUNK_SIZE GRUB_INT_MAX
 
 typedef struct http_data
 {
@@ -82,6 +83,8 @@
   if (data->in_chunk_len == 2)
     {
       data->chunk_rem = grub_strtoul (ptr, 0, 16);
+      if (data->chunk_rem > HTTP_MAX_CHUNK_SIZE)
+	  return GRUB_ERR_NET_PACKET_TOO_BIG;
       grub_errno = GRUB_ERR_NONE;
       if (data->chunk_rem == 0)
 	{