bugtraq - Re: Re: Syscall implementation could lead to whether or not a file exists

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 linux-cve-announce 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]

Message-ID: <3652.203.33.133.31.1049671923.squirrel@d2.net.au>
Date: Mon, 7 Apr 2003 09:32:03 +1000 (EST)
From: <andrewg@...net.au>
To: <pavel@...e.cz>
Cc: <andrewg@...net.au>, <full-disclosure@...ts.netsys.com>,
   <bugtraq@...urityfocus.com>
Subject: Re: Re: Syscall implementation could lead to whether or not a file exists


> Hi!
>
>> 	After a while of experimentation, I found that the following
>> 	formuala seems to be relatively decent at avoiding false
>> 	positivites, on my RH box.
>>
>> 		cutoff = ((success_time + failure_time) / 3) - 2
>>
>> 	This is somewhat dependant on the load on the box, and where the
>> 	file is located, though it appears.
>>
>> 	On some OS's (notably freebsd in my testing) it will store the
>> 	results of into its cache (different to linux, in the sense that  it
>> 	throws
>> off the algo above.). Thus, if you just create a file 		and
time
>> open()ing that, then compare it with a file that has
>> 	been recently opened, you don't get a fair comparsision.
>>
>>
>> Fix:
>>
>> 	No known fix exists. Not exactly sure whether a fix is
>> 	appropiate, as the kernel is meant to be as fast as possible.
>
> Umm, this is nasty. Random delay in "return -EPERM" path would not
> help; making sure every syscall returning EPERM last at least 20usec
> would but implementing that would be hard.

Under linux, I would think you could do this in the return from the calling
of sys_call_table easily, in the interrupt handler ;)

However, extending the time the interrupt takes, imo, is bad.

> 								Pavel
> --
> When do you have heart between your knees?
> _______________________________________________
> Full-Disclosure - We believe in it.
> Charter: http://lists.netsys.com/full-disclosure-charter.html

Thanks,
Andrew Griffiths


_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.netsys.com/full-disclosure-charter.html