Fix TOCTOU race conditions both inside the implementation of functions and the
contract: functions now only operate on directories. Callers wanting to
process the contents of a symlink (e.g. for remove_dir_contents) should
resolve the symlink themselves. This is an API break from 0.7.0, but the previous behaviour was insecure.
This is due to the same code pattern as caused CVE-2022-21658 in Rust itself:
it was possible to trick a privileged process doing a recursive delete in an
attacker controlled directory into deleting privileged files, on all operating
systems.
For instance, consider deleting a tree called 'etc' in a parent directory
called 'p'. Between calling remove_dir_all("a") and remove_dir_all("a")
actually starting its work, the attacker can move 'p' to 'p-prime', and
replace 'p' with a symlink to '/'. Then the privileged process deletes 'p/etc'
which is actually /etc, and now your system is broken. There are some
mitigations for this exact scenario, such as CWD relative file lookup, but
they are not guaranteed - any code using absolute paths will not have that
protection in place.
The same attack could be performed at any point in the directory tree being
deleted: if 'a' contains a child directory called 'etc', attacking the
deletion by replacing 'a' with a link is possible.
The new code in this release mitigates the attack within the directory tree
being deleted by using file-handle relative operations: to open 'a/etc', the
path 'etc' relative to 'a' is opened, where 'a' is represented by a file
descriptor (Unix) or handle (Windows). With the exception of the entry points
into the directory deletion logic, this is robust against manipulation of the
directory hierarchy, and remove_dir_all will only delete files and directories
contained in the tree it is deleting.
The entry path however is a challenge - as described above, there are some
potential mitigations, but since using them must be done by the calling code,
it is hard to be confident about the security properties of the path based
interface.
The new extension trait RemoveDir provides an interface where it is much
harder to get it wrong.
somedir.remove_dir_contents("name-of-child").
Callers can then make their own security evaluation about how to securely get
a directory handle. That is still not particularly obvious, and we're going to
follow up with a helper of some sort (probably in the fs_at crate). Once
that is available, the path based entry points will get deprecated.
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Bumps remove_dir_all from 0.7.0 to 0.8.0.
Changelog
Sourced from remove_dir_all's changelog.
... (truncated)
Commits
e1066ef
Release 0.8.07247a8b
Merge pull request from GHSA-mc8h-8q98-g5hrbe7a410
Update windows-sys requirement from 0.42.0 to 0.45.0 (#52)6ebf7f0
Use SPDX license format (#50)48e2043
Remove unusednum_cpus
dependency (#48)720ca0e
Updatewindows-sys
to0.42.0
(#47)8b66129
Migrate from winapi to windows-sys. (#42)d224855
Make parallelism a default-on feature (#38)08037c9
Remove nightly feature (#37)d8e02e6
Update env_logger requirement from 0.8.1 to 0.9.0 (#32)Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting
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