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package/busybox: add upstream gunzip security fix

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Fixes the following security issue:

- CVE-2021-28831: decompress_gunzip.c in BusyBox through 1.32.1 mishandles
  the error bit on the huft_build result pointer, with a resultant invalid
  free or segmentation fault, via malformed gzip data.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
This commit is contained in:
Peter Korsgaard 2021-04-06 15:11:59 +02:00
parent d043f5775a
commit 0f4ec05ed0
2 changed files with 61 additions and 0 deletions
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58
package/busybox/0004-decompress_gunzip-Fix-DoS-if-gzip-is-corrupt.patch Normal file
View File

@ -0,0 +1,58 @@
From f25d254dfd4243698c31a4f3153d4ac72aa9e9bd Mon Sep 17 00:00:00 2001
From: Samuel Sapalski <samuel.sapalski@nokia.com>
Date: Wed, 3 Mar 2021 16:31:22 +0100
Subject: [PATCH] decompress_gunzip: Fix DoS if gzip is corrupt
On certain corrupt gzip files, huft_build will set the error bit on
the result pointer. If afterwards abort_unzip is called huft_free
might run into a segmentation fault or an invalid pointer to
free(p).
In order to mitigate this, we check in huft_free if the error bit
is set and clear it before the linked list is freed.
Signed-off-by: Samuel Sapalski <samuel.sapalski@nokia.com>
Signed-off-by: Peter Kaestle <peter.kaestle@nokia.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
---
archival/libarchive/decompress_gunzip.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/archival/libarchive/decompress_gunzip.c b/archival/libarchive/decompress_gunzip.c
index eb3b64930..e93cd5005 100644
--- a/archival/libarchive/decompress_gunzip.c
+++ b/archival/libarchive/decompress_gunzip.c
@@ -220,10 +220,20 @@ static const uint8_t border[] ALIGN1 = {
* each table.
* t: table to free
*/
+#define BAD_HUFT(p) ((uintptr_t)(p) & 1)
+#define ERR_RET ((huft_t*)(uintptr_t)1)
static void huft_free(huft_t *p)
{
huft_t *q;
+ /*
+ * If 'p' has the error bit set we have to clear it, otherwise we might run
+ * into a segmentation fault or an invalid pointer to free(p)
+ */
+ if (BAD_HUFT(p)) {
+ p = (huft_t*)((uintptr_t)(p) ^ (uintptr_t)(ERR_RET));
+ }
+
/* Go through linked list, freeing from the malloced (t[-1]) address. */
while (p) {
q = (--p)->v.t;
@@ -289,8 +299,6 @@ static unsigned fill_bitbuffer(STATE_PARAM unsigned bitbuffer, unsigned *current
* or a valid pointer to a Huffman table, ORed with 0x1 if incompete table
* is given: "fixed inflate" decoder feeds us such data.
*/
-#define BAD_HUFT(p) ((uintptr_t)(p) & 1)
-#define ERR_RET ((huft_t*)(uintptr_t)1)
static huft_t* huft_build(const unsigned *b, const unsigned n,
const unsigned s, const struct cp_ext *cp_ext,
unsigned *m)
--
2.20.1

3
package/busybox/busybox.mk
View File

@ -11,6 +11,9 @@ BUSYBOX_LICENSE = GPL-2.0, bzip2-1.0.4
BUSYBOX_LICENSE_FILES = LICENSE archival/libarchive/bz/LICENSE
BUSYBOX_CPE_ID_VENDOR = busybox
# 0004-decompress_gunzip-Fix-DoS-if-gzip-is-corrupt.patch
BUSYBOX_IGNORE_CVES += CVE-2021-28831
define BUSYBOX_HELP_CMDS
@echo ' busybox-menuconfig - Run BusyBox menuconfig'
endef