package/libarchive: add upstream security fix for CVE-2019-19221

Fixes the following security issue:

- CVE-2019-19221: In Libarchive 3.4.0, archive_wstring_append_from_mbs in
  archive_string.c has an out-of-bounds read because of an incorrect mbrtowc
  or mbtowc call.  For example, bsdtar crashes via a crafted archive.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libarchive/0008-Bugfix-and-optimize-archive_wstring_append_from_mbs.patch

@@ -0,0 +1,103 @@
+From 22b1db9d46654afc6f0c28f90af8cdc84a199f41 Mon Sep 17 00:00:00 2001
+From: Martin Matuska <martin@matuska.org>
+Date: Thu, 21 Nov 2019 03:08:40 +0100
+Subject: [PATCH] Bugfix and optimize archive_wstring_append_from_mbs()
+
+The cal to mbrtowc() or mbtowc() should read up to mbs_length
+bytes and not wcs_length. This avoids out-of-bounds reads.
+
+mbrtowc() and mbtowc() return (size_t)-1 wit errno EILSEQ when
+they encounter an invalid multibyte character and (size_t)-2 when
+they they encounter an incomplete multibyte character. As we return
+failure and all our callers error out it makes no sense to continue
+parsing mbs.
+
+As we allocate `len` wchars at the beginning and each wchar has
+at least one byte, there will never be need to grow the buffer,
+so the code can be left out. On the other hand, we are always
+allocatng more memory than we need.
+
+As long as wcs_length == mbs_length == len we can omit wcs_length.
+We keep the old code commented if we decide to save memory and
+use autoexpanding wcs_length in the future.
+
+Fixes #1276
+
+Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
+[Peter: fixes CVE-2019-19221]
+---
+ libarchive/archive_string.c | 28 +++++++++++++++++-----------
+ 1 file changed, 17 insertions(+), 11 deletions(-)
+
+diff --git a/libarchive/archive_string.c b/libarchive/archive_string.c
+index 979a418b..bd39c96f 100644
+--- a/libarchive/archive_string.c
++++ b/libarchive/archive_string.c
+@@ -591,7 +591,7 @@ archive_wstring_append_from_mbs(struct archive_wstring *dest,
+ 	 * No single byte will be more than one wide character,
+ 	 * so this length estimate will always be big enough.
+ 	 */
+-	size_t wcs_length = len;
++	// size_t wcs_length = len;
+ 	size_t mbs_length = len;
+ 	const char *mbs = p;
+ 	wchar_t *wcs;
+@@ -600,7 +600,11 @@ archive_wstring_append_from_mbs(struct archive_wstring *dest,
+ 
+ 	memset(&shift_state, 0, sizeof(shift_state));
+ #endif
+-	if (NULL == archive_wstring_ensure(dest, dest->length + wcs_length + 1))
++	/*
++	 * As we decided to have wcs_length == mbs_length == len
++	 * we can use len here instead of wcs_length
++	 */
++	if (NULL == archive_wstring_ensure(dest, dest->length + len + 1))
+ 		return (-1);
+ 	wcs = dest->s + dest->length;
+ 	/*
+@@ -609,6 +613,12 @@ archive_wstring_append_from_mbs(struct archive_wstring *dest,
+ 	 * multi bytes.
+ 	 */
+ 	while (*mbs && mbs_length > 0) {
++		/*
++		 * The buffer we allocated is always big enough.
++		 * Keep this code path in a comment if we decide to choose
++		 * smaller wcs_length in the future
++		 */
++/*
+ 		if (wcs_length == 0) {
+ 			dest->length = wcs - dest->s;
+ 			dest->s[dest->length] = L'\0';
+@@ -618,24 +628,20 @@ archive_wstring_append_from_mbs(struct archive_wstring *dest,
+ 				return (-1);
+ 			wcs = dest->s + dest->length;
+ 		}
++*/
+ #if HAVE_MBRTOWC
+-		r = mbrtowc(wcs, mbs, wcs_length, &shift_state);
++		r = mbrtowc(wcs, mbs, mbs_length, &shift_state);
+ #else
+-		r = mbtowc(wcs, mbs, wcs_length);
++		r = mbtowc(wcs, mbs, mbs_length);
+ #endif
+ 		if (r == (size_t)-1 || r == (size_t)-2) {
+ 			ret_val = -1;
+-			if (errno == EILSEQ) {
+-				++mbs;
+-				--mbs_length;
+-				continue;
+-			} else
+-				break;
++			break;
+ 		}
+ 		if (r == 0 || r > mbs_length)
+ 			break;
+ 		wcs++;
+-		wcs_length--;
++		// wcs_length--;
+ 		mbs += r;
+ 		mbs_length -= r;
+ 	}
+-- 
+2.20.1
+