* [Buildroot] [PATCH] package/busybox: add upstream gunzip security fix
@ 2021-04-06 13:07 Peter Korsgaard
2021-04-06 13:11 ` Peter Korsgaard
0 siblings, 1 reply; 2+ messages in thread
From: Peter Korsgaard @ 2021-04-06 13:07 UTC (permalink / raw)
To: buildroot
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>
---
...ss_gunzip-Fix-DoS-if-gzip-is-corrupt.patch | 58 +++++++++++++++++++
1 file changed, 58 insertions(+)
create mode 100644 package/busybox/0004-decompress_gunzip-Fix-DoS-if-gzip-is-corrupt.patch
diff --git a/package/busybox/0004-decompress_gunzip-Fix-DoS-if-gzip-is-corrupt.patch b/package/busybox/0004-decompress_gunzip-Fix-DoS-if-gzip-is-corrupt.patch
new file mode 100644
index 0000000000..d40cb4d6cd
--- /dev/null
+++ b/package/busybox/0004-decompress_gunzip-Fix-DoS-if-gzip-is-corrupt.patch
@@ -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
+
--
2.20.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [Buildroot] [PATCH] package/busybox: add upstream gunzip security fix
2021-04-06 13:07 [Buildroot] [PATCH] package/busybox: add upstream gunzip security fix Peter Korsgaard
@ 2021-04-06 13:11 ` Peter Korsgaard
0 siblings, 0 replies; 2+ messages in thread
From: Peter Korsgaard @ 2021-04-06 13:11 UTC (permalink / raw)
To: buildroot
>>>>> "Peter" == Peter Korsgaard <peter@korsgaard.com> writes:
> 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>
Ups, I forgot the _IGNORE_CVES entry. Will send a v2.
--
Bye, Peter Korsgaard
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-04-06 13:07 [Buildroot] [PATCH] package/busybox: add upstream gunzip security fix Peter Korsgaard
2021-04-06 13:11 ` Peter Korsgaard
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