0f4ec05ed0
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>
59 lines
2.1 KiB
Diff
59 lines
2.1 KiB
Diff
From f25d254dfd4243698c31a4f3153d4ac72aa9e9bd Mon Sep 17 00:00:00 2001
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From: Samuel Sapalski <samuel.sapalski@nokia.com>
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Date: Wed, 3 Mar 2021 16:31:22 +0100
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Subject: [PATCH] decompress_gunzip: Fix DoS if gzip is corrupt
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On certain corrupt gzip files, huft_build will set the error bit on
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the result pointer. If afterwards abort_unzip is called huft_free
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might run into a segmentation fault or an invalid pointer to
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free(p).
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In order to mitigate this, we check in huft_free if the error bit
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is set and clear it before the linked list is freed.
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Signed-off-by: Samuel Sapalski <samuel.sapalski@nokia.com>
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Signed-off-by: Peter Kaestle <peter.kaestle@nokia.com>
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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
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---
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archival/libarchive/decompress_gunzip.c | 12 ++++++++++--
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1 file changed, 10 insertions(+), 2 deletions(-)
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diff --git a/archival/libarchive/decompress_gunzip.c b/archival/libarchive/decompress_gunzip.c
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index eb3b64930..e93cd5005 100644
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--- a/archival/libarchive/decompress_gunzip.c
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+++ b/archival/libarchive/decompress_gunzip.c
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@@ -220,10 +220,20 @@ static const uint8_t border[] ALIGN1 = {
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* each table.
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* t: table to free
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*/
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+#define BAD_HUFT(p) ((uintptr_t)(p) & 1)
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+#define ERR_RET ((huft_t*)(uintptr_t)1)
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static void huft_free(huft_t *p)
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{
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huft_t *q;
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+ /*
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+ * If 'p' has the error bit set we have to clear it, otherwise we might run
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+ * into a segmentation fault or an invalid pointer to free(p)
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+ */
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+ if (BAD_HUFT(p)) {
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+ p = (huft_t*)((uintptr_t)(p) ^ (uintptr_t)(ERR_RET));
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+ }
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+
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/* Go through linked list, freeing from the malloced (t[-1]) address. */
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while (p) {
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q = (--p)->v.t;
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@@ -289,8 +299,6 @@ static unsigned fill_bitbuffer(STATE_PARAM unsigned bitbuffer, unsigned *current
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* or a valid pointer to a Huffman table, ORed with 0x1 if incompete table
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* is given: "fixed inflate" decoder feeds us such data.
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*/
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-#define BAD_HUFT(p) ((uintptr_t)(p) & 1)
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-#define ERR_RET ((huft_t*)(uintptr_t)1)
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static huft_t* huft_build(const unsigned *b, const unsigned n,
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const unsigned s, const struct cp_ext *cp_ext,
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unsigned *m)
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--
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2.20.1
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