libarchive: do not extract unsafe symlinks unless $EXTRACT_UNSAFE_SYMLINKS=1

function                                             old     new   delta
unsafe_symlink_target                                  -     147    +147
unzip_main                                          2711    2732     +21
copy_file                                           1657    1678     +21
tar_main                                             999     971     -28
data_extract_all                                    1038     984     -54
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 2/2 up/down: 189/-82)           Total: 107 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2017-08-10 11:52:42 +02:00
parent 0cf64c8b5d
commit bc9bbeb2b8
9 changed files with 85 additions and 55 deletions

View File

@@ -129,9 +129,7 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
if (res != 0 && !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)) {
/* shared message */
bb_perror_msg("can't create %slink '%s' to '%s'",
"hard",
dst_name,
hard_link
"hard", dst_name, hard_link
);
}
/* Hardlinks have no separate mode/ownership, skip chown/chmod */
@@ -181,7 +179,9 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
//TODO: what if file_header->link_target == NULL (say, corrupted tarball?)
/* To avoid a directory traversal attack via symlinks,
* for certain link targets postpone creation of symlinks.
* do not restore symlinks with ".." components
* or symlinks starting with "/", unless a magic
* envvar is set.
*
* For example, consider a .tar created via:
* $ tar cvf bug.tar anything.txt
@@ -199,24 +199,17 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
*
* Untarring bug.tar would otherwise place evil.py in '/tmp'.
*/
if (file_header->link_target[0] == '/'
|| strstr(file_header->link_target, "..")
) {
llist_add_to(&archive_handle->symlink_placeholders,
xasprintf("%s%c%s", file_header->name, '\0', file_header->link_target)
);
break;
}
res = symlink(file_header->link_target, dst_name);
if (res != 0
&& !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)
) {
/* shared message */
bb_perror_msg("can't create %slink '%s' to '%s'",
"sym",
dst_name,
file_header->link_target
);
if (!unsafe_symlink_target(file_header->link_target)) {
res = symlink(file_header->link_target, dst_name);
if (res != 0
&& !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)
) {
/* shared message */
bb_perror_msg("can't create %slink '%s' to '%s'",
"sym",
dst_name, file_header->link_target
);
}
}
break;
case S_IFSOCK: