From c5fa5fa521644d4f41ba0f436826d0b0345645b2 Mon Sep 17 00:00:00 2001
From: Sebastian Krahmer <krahmer@suse.com>
Date: Tue, 28 Nov 2017 17:24:38 +0800
Subject: [PATCH 120/220] 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.

Signed-off-by: Michael Chang <mchang@suse.com>
---
 grub-core/net/efi/net.c | 4 +++-
 grub-core/net/http.c    | 5 ++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/grub-core/net/efi/net.c b/grub-core/net/efi/net.c
index 86bce65..4bb3080 100644
--- a/grub-core/net/efi/net.c
+++ b/grub-core/net/efi/net.c
@@ -645,8 +645,10 @@ grub_efihttp_chunk_read (grub_file_t file, char *buf,
 
       rd = efi_net_interface (read, file, chunk, sz);
 
-      if (rd <= 0)
+      if (rd <= 0) {
+	grub_free (chunk);
 	return rd;
+      }
 
       if (buf)
 	{
diff --git a/grub-core/net/http.c b/grub-core/net/http.c
index 00737c5..c9c5969 100644
--- a/grub-core/net/http.c
+++ b/grub-core/net/http.c
@@ -31,7 +31,8 @@ GRUB_MOD_LICENSE ("GPLv3+");
 
 enum
   {
-    HTTP_PORT = 80
+    HTTP_PORT = 80,
+    HTTP_MAX_CHUNK_SIZE = 0x80000000
   };
 
 
@@ -78,6 +79,8 @@ parse_line (grub_file_t file, http_data_t data, char *ptr, grub_size_t len)
   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)
 	{
-- 
1.8.3.1

