bsdbsdftpd-6.0-ssl-0.6.1-1 attack allows remote users identification

[NetExpress]

Product bsbsdftpd-6.0-ssl-0.6.1-1 http://bsdftpd-ssl.sc.ru/

During a pen-test we have notice how is easy to identify valid users on
vulnerable systems, through a simple timing attack.

When I try to connect to ftp without ssl using a unreal user with bad
password I get
immediatly response of incorrect login, when I use real user with bad
password I get 2 second of wait before get message of incorrect login.

It seems to be very nice to the recent CAN-2003-0190 about OpenSSH/PAM
timing attack allows remote users identification

I have tested this on Linux RH 7.3 and RH 8.0

I belive the vulnerability is easy to exploit and may have high
severity, if combined with poor password policies and other security
problems that allow local privilege escalation.


Alessandro Fiorenzi

a.fiorenzi@infogroup.it aka netexpress

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[Damian Gerow]

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Thus spake NetExpress (netexpress@tiscali.it) [16/05/03 16:42]:
> Product bsbsdftpd-6.0-ssl-0.6.1-1 http://bsdftpd-ssl.sc.ru/
>=20
> During a pen-test we have notice how is easy to identify valid users on
> vulnerable systems, through a simple timing attack.
>=20
> When I try to connect to ftp without ssl using a unreal user with bad=20
> password I get
> immediatly response of incorrect login, when I use real user with bad
> password I get 2 second of wait before get message of incorrect login.
>=20
> It seems to be very nice to the recent CAN-2003-0190 about OpenSSH/PAM
> timing attack allows remote users identification
>=20
> I have tested this on Linux RH 7.3 and RH 8.0

I just tried this out on a FreeBSD system (4.8-RC x2), and I get the same
response time. Are you sure this is directly related to the ftp daemon, or
is it a PAM issue?

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[NetExpress]

Damian Gerow wrote:

>Thus spake NetExpress (netexpress@tiscali.it) [16/05/03 16:42]:
>
>
>>Product bsbsdftpd-6.0-ssl-0.6.1-1 http://bsdftpd-ssl.sc.ru/
>>
>>During a pen-test we have notice how is easy to identify valid users on
>>vulnerable systems, through a simple timing attack.
>>
>>When I try to connect to ftp without ssl using a unreal user with bad
>>password I get
>>immediatly response of incorrect login, when I use real user with bad
>>password I get 2 second of wait before get message of incorrect login.
>>
>>It seems to be very nice to the recent CAN-2003-0190 about OpenSSH/PAM
>>timing attack allows remote users identification
>>
>>I have tested this on Linux RH 7.3 and RH 8.0
>>
>>
>
>I just tried this out on a FreeBSD system (4.8-RC x2), and I get the same
>response time. Are you sure this is directly related to the ftp daemon, or
>is it a PAM issue?
>
>
You are right, is the same preoblem has affected OpenSSH/PAM timing
attack about which Marco Ivald from MediaService has post the bug and
the solution.

I have been in touch with Marco Ivaldi, he has found that is the same
kind of problem, an the same soltion, but is not really goot to get this
problem on the default installation . I mailed to the author but I get
no response

For the solution follow the same present on
http://lab.mediaservice.net/advisory/2003-01-openssh.txt

Alessandro Fiorenzi

[Mika =?iso-8859-15?Q?Bostr=F6m?=]

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On Fri, 16 May 2003, Damian Gerow wrote:
> Thus spake NetExpress (netexpress@tiscali.it) [16/05/03 16:42]:
> > Product bsbsdftpd-6.0-ssl-0.6.1-1 http://bsdftpd-ssl.sc.ru/
> >=20
> > During a pen-test we have notice how is easy to identify valid users on
> > vulnerable systems, through a simple timing attack.
> >=20
> > When I try to connect to ftp without ssl using a unreal user with bad=
=20
> > password I get
> > immediatly response of incorrect login, when I use real user with bad
> > password I get 2 second of wait before get message of incorrect login.
> >=20
> > It seems to be very nice to the recent CAN-2003-0190 about OpenSSH/PAM
> > timing attack allows remote users identification
> >=20
> > I have tested this on Linux RH 7.3 and RH 8.0
>=20
> I just tried this out on a FreeBSD system (4.8-RC x2), and I get the same
> response time. Are you sure this is directly related to the ftp daemon, =
or
> is it a PAM issue?

Looking back two weeks in BugTraq archives, I see the following
posting:
http://www.securityfocus.com/archive/1/320270/2003-04-30/2003-05-06/0

This suggests that many more programs are similarly vulnerable,
because they take shortcuts. After all, it is quite common and generally
even good practise to skip redundant code paths. The flipside of the
coin is that it may allow these kind of timing attacks.


--=20
Mika Bostr=F6m +358-50-410-9042 \-/ "The Hell is empty,
Bostik@lut.fi www.lut.fi/~bostik X and all the devils
Security freak, and proud of it. /-\ are here." -W.S.

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