oss-sec mailing list archives
Re: Untrusted fs and invalid filenames
From: Steve Grubb <sgrubb () redhat com>
Date: Sun, 13 Mar 2011 14:55:44 -0400
On Saturday, March 12, 2011 12:03:45 pm Vasiliy Kulikov wrote:
While POSIX restricts the character set used in filenames, some Linux filesystems (at least ext2) permit reserved filenames ".", ".." and filenames with "/" inside. I have a crafted flash drive with ext2 that has such files:
I can confirm that ext3/4, xfs, cramfs, and reiserfs also allow these kinds of names. I'm sure that with some patience, there are more.
Guess what does "rm" with such filenames :-)
and tar
What I suggest is something like "-o untrusted" option to mount. This would mean that the system considers the input from such fs as a malicious input. Such mounted fs would try to consider the data on disk as untrusted and to be as robust as possible, e.g. check against "/"-filenames, against corrupted fs structures, etc. I'd be happy to hear opinions about the usefulness of this feature.
Something else I was noticing is that fsck does not also enforce the correct naming constraints. Maybe what can be done is fix fsck and force it to scan the file system before making it accessible. -Steve
Current thread:
- Untrusted fs and invalid filenames Vasiliy Kulikov (Mar 12)
- Re: Untrusted fs and invalid filenames Steve Grubb (Mar 13)
- Re: Untrusted fs and invalid filenames Eitan Adler (Mar 13)
- Re: Untrusted fs and invalid filenames Stephan Mueller (Mar 14)
- Re: Untrusted fs and invalid filenames Dan Rosenberg (Mar 14)
- Re: Untrusted fs and invalid filenames Stephan Mueller (Mar 14)
- Re: Untrusted fs and invalid filenames Steve Grubb (Mar 14)
- Re: Untrusted fs and invalid filenames Vasiliy Kulikov (Mar 14)
- Re: Untrusted fs and invalid filenames Ludwig Nussel (Mar 14)
- Re: Untrusted fs and invalid filenames Steve Grubb (Mar 14)
- Re: Untrusted fs and invalid filenames Dan Rosenberg (Mar 14)