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From 42ce7953f48e5542297ff4381086b45ae28a02cf Mon Sep 17 00:00:00 2001
From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Wed, 2 Oct 2024 10:12:05 +0200
Subject: [PATCH] archival: disallow path traversals (CVE-2023-39810)
Create new configure option for archival/libarchive based extractions to
disallow path traversals.
As this is a paranoid option and might introduce backward
incompatibility, default it to no.
Fixes: CVE-2023-39810
Based on the patch by Peter Kaestle <peter.kaestle@nokia.com>
function old new delta
data_extract_all 921 945 +24
strip_unsafe_prefix 101 102 +1
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 25/0) Total: 25 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
CVE: CVE-2023-39810
Upstream-Status: Backport [https://git.busybox.net/busybox/commit/?id=9a8796436b9b0641e13480811902ea2ac57881d3]
Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
---
archival/Config.src | 11 +++++++++++
archival/libarchive/data_extract_all.c | 8 ++++++++
archival/libarchive/unsafe_prefix.c | 6 +++++-
scripts/kconfig/lxdialog/check-lxdialog.sh | 2 +-
testsuite/cpio.tests | 23 ++++++++++++++++++++++
5 files changed, 48 insertions(+), 2 deletions(-)
diff --git a/archival/Config.src b/archival/Config.src
index 6f4f30c43..cbcd7217c 100644
--- a/archival/Config.src
+++ b/archival/Config.src
@@ -35,4 +35,15 @@ config FEATURE_LZMA_FAST
This option reduces decompression time by about 25% at the cost of
a 1K bigger binary.
+config FEATURE_PATH_TRAVERSAL_PROTECTION
+ bool "Prevent extraction of filenames with /../ path component"
+ default n
+ help
+ busybox tar and unzip remove "PREFIX/../" (if it exists)
+ from extracted names.
+ This option enables this behavior for all other unpacking applets,
+ such as cpio, ar, rpm.
+ GNU cpio 2.15 has NO such sanity check.
+# try other archivers and document their behavior?
+
endmenu
diff --git a/archival/libarchive/data_extract_all.c b/archival/libarchive/data_extract_all.c
index 049c2c156..8a69711c1 100644
--- a/archival/libarchive/data_extract_all.c
+++ b/archival/libarchive/data_extract_all.c
@@ -65,6 +65,14 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
} while (--n != 0);
}
#endif
+#if ENABLE_FEATURE_PATH_TRAVERSAL_PROTECTION
+ /* Strip leading "/" and up to last "/../" path component */
+ dst_name = (char *)strip_unsafe_prefix(dst_name);
+#endif
+// ^^^ This may be a problem if some applets do need to extract absolute names.
+// (Probably will need to invent ARCHIVE_ALLOW_UNSAFE_NAME flag).
+// You might think that rpm needs it, but in my tests rpm's internal cpio
+// archive has names like "./usr/bin/FOO", not "/usr/bin/FOO".
if (archive_handle->ah_flags & ARCHIVE_CREATE_LEADING_DIRS) {
char *slash = strrchr(dst_name, '/');
diff --git a/archival/libarchive/unsafe_prefix.c b/archival/libarchive/unsafe_prefix.c
index 33e487bf9..667081195 100644
--- a/archival/libarchive/unsafe_prefix.c
+++ b/archival/libarchive/unsafe_prefix.c
@@ -14,7 +14,11 @@ const char* FAST_FUNC strip_unsafe_prefix(const char *str)
cp++;
continue;
}
- if (is_prefixed_with(cp, "/../"+1)) {
+ /* We are called lots of times.
+ * is_prefixed_with(cp, "../") is slower than open-coding it,
+ * with minimal code growth (~few bytes).
+ */
+ if (cp[0] == '.' && cp[1] == '.' && cp[2] == '/') {
cp += 3;
continue;
}
diff --git a/scripts/kconfig/lxdialog/check-lxdialog.sh b/scripts/kconfig/lxdialog/check-lxdialog.sh
index 7003e026a..b91a54be6 100755
--- a/scripts/kconfig/lxdialog/check-lxdialog.sh
+++ b/scripts/kconfig/lxdialog/check-lxdialog.sh
@@ -55,7 +55,7 @@ trap "rm -f $tmp" 0 1 2 3 15
check() {
$cc -x c - -o $tmp 2>/dev/null <<'EOF'
#include CURSES_LOC
-main() {}
+int main() { return 0; }
EOF
if [ $? != 0 ]; then
echo " *** Unable to find the ncurses libraries or the" 1>&2
diff --git a/testsuite/cpio.tests b/testsuite/cpio.tests
index 85e746589..a4462c53e 100755
--- a/testsuite/cpio.tests
+++ b/testsuite/cpio.tests
@@ -154,6 +154,29 @@ testing "cpio -R with extract" \
" "" ""
SKIP=
+# Create an archive containing a file with "../dont_write" filename.
+# See that it will not be allowed to unpack.
+# NB: GNU cpio 2.15 DOES NOT do such checks.
+optional FEATURE_PATH_TRAVERSAL_PROTECTION
+rm -rf cpio.testdir
+mkdir -p cpio.testdir/prepare/inner
+echo "file outside of destination was written" > cpio.testdir/prepare/dont_write
+echo "data" > cpio.testdir/prepare/inner/to_extract
+mkdir -p cpio.testdir/extract
+testing "cpio extract file outside of destination" "\
+(cd cpio.testdir/prepare/inner && echo -e '../dont_write\nto_extract' | cpio -o -H newc) | (cd cpio.testdir/extract && cpio -vi 2>&1)
+echo \$?
+ls cpio.testdir/dont_write 2>&1" \
+"\
+cpio: removing leading '../' from member names
+../dont_write
+to_extract
+1 blocks
+0
+ls: cpio.testdir/dont_write: No such file or directory
+" "" ""
+SKIP=
+
# Clean up
rm -rf cpio.testdir cpio.testdir2 2>/dev/null
--
2.48.1
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