[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <51F0FDE5.9010006@pipping.org>
Date: Thu, 25 Jul 2013 12:28:53 +0200
From: Sebastian Pipping <sebastian@...ping.org>
To: kseifried@...hat.com
CC: oss-security@...ts.openwall.com
Subject: Re: CVE request: mysecureshell: local denial of service
(or worse)
Hello Kurt,
On 25.07.2013 10:33, Kurt Seifried wrote:
> On 07/23/2013 11:19 AM, Sebastian Pipping wrote:
>> mysecureshell [1] is an SFTP-only shell to be used with sshd.
>
>> The latest release 1.31 makes use of shared memory with permissions
>> 666 to maintain 128 slots with one struct for each
>> connection/process. An unprivileged user can mark mark all
>> remaining slots as occupied (and optionally wait for remaining
>> clients to leave to block those slots, too).
>
>> To demonstrate the issue, I have written a small command line
>> tool. It's free software and can be found at [2]. Use it like
>> this:
>
>> # make cc -std=c99 -Wall -Wextra -pedantic local-dos.c -o
>> local-dos
>
>> # ./local-dos USAGE: ./local-dos (block|unblock|show)
>
>> # watch -n 1 -d ./local-dos block [..]
>
>> Besides the local DoS it might be possible to attack the call to
>> chdir, since that is reading from shared memory, too.
>
>> Any ideas on other attacks based on writing to that block of
>> shared memory? File /bin/MySecureShell is mode 4755 setuid root if
>> that makes it more interesting :-)
>> [..]
>> [1] http://mysecureshell.sourceforge.net/
>> [2] https://github.com/hartwork/mysecureshell-issues
>
> To reiterate: so I can confirm CVE assignments, and prevent duplicate
> assignments you *MUST* provide links to the code commits/vulnerable
> code. I don't have the time to go hunting through your source code for
> them. People need to start making better CVE requests, or you're not
> going to get CVEs from me.
>
> I think if I repeat this enough times it'll work.
Upstream tarball
================
http://mysecureshell.free.fr/repository/index.php/debian/pool/main/m/mysecureshell/mysecureshell_1.31.tar.gz
Issue
=====
Mode 0666 for shared memory, local denial of service
Guilty code
===========
Online
~~~~~~
http://mysecureshell.cvs.sourceforge.net/viewvc/mysecureshell/mysecureshell/SftpServer/SftpWho.c?revision=1.3&view=markup#l73
Inlined (from SftpServer/SftpWho.c, lines 73 and after)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//try to join to existing shm
if ((shmid = shmget(key, sizeof(t_shm), 0)) == -1)
if (create == 1)
{
shmid = shmget(key, sizeof(t_shm), IPC_CREAT | IPC_EXCL | 0666);
eraze = 1;
}
Please let me know if you need anything more. Thanks for your time!
Best,
Sebastian
Powered by blists - more mailing lists
Please check out the
Open Source Software Security Wiki, which is counterpart to this
mailing list.
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
