tar,unzip: postpone creation of symlinks with "suspicious" targets
This mostly reverts commit bc9bbeb2b8
"libarchive: do not extract unsafe symlinks unless $EXTRACT_UNSAFE_SYMLINKS=1"
Users report that it is somewhat too restrictive. See
https://bugs.busybox.net/show_bug.cgi?id=8411
In particular, this interferes with unpacking of busybox-based
filesystems with links like "sbin/applet" -> "../bin/busybox".
The change is made smaller by deleting ARCHIVE_EXTRACT_QUIET flag -
it is unused since 2010, and removing conditionals on it
allows commonalizing some error message codes.
function old new delta
create_or_remember_symlink - 94 +94
create_symlinks_from_list - 64 +64
tar_main 1002 1006 +4
unzip_main 2732 2724 -8
data_extract_all 984 891 -93
unsafe_symlink_target 147 - -147
------------------------------------------------------------------------------
(add/remove: 2/1 grow/shrink: 1/2 up/down: 162/-248) Total: -86 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
@ -5,44 +5,37 @@
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#include "libbb.h"
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#include "bb_archive.h"
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int FAST_FUNC unsafe_symlink_target(const char *target)
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void FAST_FUNC create_or_remember_symlink(llist_t **symlink_placeholders,
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const char *target,
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const char *linkname)
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{
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const char *dot;
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if (target[0] == '/') {
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const char *var;
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unsafe:
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var = getenv("EXTRACT_UNSAFE_SYMLINKS");
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if (var) {
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if (LONE_CHAR(var, '1'))
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return 0; /* pretend it's safe */
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return 1; /* "UNSAFE!" */
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}
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bb_error_msg("skipping unsafe symlink to '%s' in archive,"
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" set %s=1 to extract",
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target,
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"EXTRACT_UNSAFE_SYMLINKS"
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if (target[0] == '/' || strstr(target, "..")) {
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llist_add_to(symlink_placeholders,
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xasprintf("%s%c%s", linkname, '\0', target)
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);
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/* Prevent further messages */
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setenv("EXTRACT_UNSAFE_SYMLINKS", "0", 0);
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return 1; /* "UNSAFE!" */
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return;
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}
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dot = target;
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for (;;) {
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dot = strchr(dot, '.');
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if (!dot)
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return 0; /* safe target */
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/* Is it a path component starting with ".."? */
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if ((dot[1] == '.')
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&& (dot == target || dot[-1] == '/')
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/* Is it exactly ".."? */
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&& (dot[2] == '/' || dot[2] == '\0')
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) {
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goto unsafe;
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}
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/* NB: it can even be trailing ".", should only add 1 */
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dot += 1;
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if (symlink(target, linkname) != 0) {
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/* shared message */
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bb_perror_msg_and_die("can't create %slink '%s' to '%s'",
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"sym", linkname, target
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);
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}
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}
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void FAST_FUNC create_symlinks_from_list(llist_t *list)
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{
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while (list) {
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char *target;
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target = list->data + strlen(list->data) + 1;
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if (symlink(target, list->data)) {
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/* shared message */
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bb_error_msg_and_die("can't create %slink '%s' to '%s'",
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"sym",
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list->data, target
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);
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}
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list = list->link;
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}
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}
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