lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Mon, 26 Oct 2009 17:31:57 +0100
From:	Jan Kara <jack@...e.cz>
To:	Pavel Machek <pavel@....cz>
Cc:	kernel list <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org, viro@...iv.linux.org.uk,
	jamie@...reable.org
Subject: Re: symlinks with permissions

  Hi,

On Sun 25-10-09 07:29:53, Pavel Machek wrote:
> ...yes, they do exist, in /proc/self/fd/* . Unfortunately, their
> permissions are not actually checked during open, resulting in
> (obscure) security hole: if you have fd open for reading, you can
> reopen it for write, even through unix permissions would not allow
> that.
> 
> Now... I'd like to close the hole. One way would be to actually check
> symlink permissions on open -- because those symlinks already have
> correct permissions.
  Hmm, I'm not sure I understand the problem. Symlink is just a file
containing a path. So if you try to open a symlink, you will actually open
a file to which the path points. So what security problem is here? Either
you can open the file symlink points to for writing or you cannot...
  Anyway, if you want to play with this,
fs/proc/base.c:proc_pid_follow_link
  is probably the function you are interested in.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists