Re: security vulnerability : SMTP daemon supports EHLO

2011-05-04 Thread Ralf Hildebrandt
* Roger Goh : > Hi, > > During a VA scan, it's reported that my postfix server has > a security vulnerability : > >EhloCheck: SMTP daemon supports EHLO That is NOT a vulnerability. -- Ralf Hildebrandt Geschäftsbereich IT | Abteilung Netzwerk Charité - Universitätsmedizin Berlin Campu

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Reindl Harald
Am 03.05.2011 19:00, schrieb Rich Wales: >> So what other 'vulnerable' configuration information EHLO reveals >> & how they can disabled/mitigated/fabricated ? > > You may want to suppress the SIZE information (maximum size of a > message that your server will accept). Some hackers might take >

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Victor Duchovni
On Tue, May 03, 2011 at 11:15:57AM -0700, Rich Wales wrote: > A followup question. If I suppress the advertising of an extended > feature by listing it in smtpd_discard_ehlo_keywords, does that also > disable the feature? Or do I have to do other things to actually > turn a feature off and make

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Rich Wales
>> You may want to suppress the SIZE information . . . . > > No, this is silly, one is better off advertising the maximum size > to avoid the vast majority unnecessary partial transmission of > overly large messages. An attacker can tie up SMTP server resources > whether the SIZE limit is known o

RE: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Murray S. Kucherawy
> -Original Message- > From: owner-postfix-us...@postfix.org > [mailto:owner-postfix-us...@postfix.org] On Behalf Of Rich Wales > Sent: Tuesday, May 03, 2011 9:18 AM > To: postfix users > Subject: Re: security vulnerability : SMTP daemon supports EHLO > > I can i

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Victor Duchovni
On Tue, May 03, 2011 at 10:00:58AM -0700, Rich Wales wrote: > > So what other 'vulnerable' configuration information EHLO reveals > > & how they can disabled/mitigated/fabricated ? > > You may want to suppress the SIZE information (maximum size of a > message that your server will accept). Some

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Rich Wales
> So what other 'vulnerable' configuration information EHLO reveals > & how they can disabled/mitigated/fabricated ? You may want to suppress the SIZE information (maximum size of a message that your server will accept). Some hackers might take this as a challenge and try to exploit it in a denia

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Rich Wales
> Can we mitigate it somewhat like what Roger Klorese suggested, > eg: restrict the info EHLO reveals or don't reveal actual hostname : All the configuration items you mentioned are things that affect what your Postfix will or won't do as a client talking to other servers. These configuration opti

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Wietse Venema
Roger Goh: > Hi, > > During a VA scan, it's reported that my postfix server has > a security vulnerability : > >EhloCheck: SMTP daemon supports EHLO EHLO is required by the SMTP standard (RFC 5321). Wietse

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Roger Goh
& from the url Roger Klorese provided, http://www.iss.net/security_center/reference/vuln/smtp-ehlo.htm it says : SMTP daemons that support Extended HELO (EHLO) can release information that could be useful to an attacker in performing an attack. Attackers have been known to use the EHLO command t

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Roger Goh
Ok, ok, no offence intended. Can we mitigate it somewhat like what Roger Klorese suggested, eg: restrict the info EHLO reveals or don't reveal actual hostname : smtp_helo_name ($myhostname) Use a fictitious hostname to send in the SMTP EHLO or HELO command (& how do I do this?

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Rich Wales
> During a VA scan, it's reported that my postfix server has a security > vulnerability : EhloCheck: SMTP daemon supports EHLO As Roger Klorese pointed out, there is an advertised, fuzzy vulnerability advisory out there regarding EHLO. However, as Noel Jones indicated, EHLO is a standard part o

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Roger B.A. Klorese
On May 3, 2011, at 8:49 AM, Reindl Harald wrote:Am 03.05.2011 17:34, schrieb Roger Goh:Hi,During a VA scan, it's reported that my postfix server hasa security vulnerability :   EhloCheck: SMTP daemon supports EHLOwhere exactly is the security hole?you should not trust the output of every tool blind

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Reindl Harald
Am 03.05.2011 17:34, schrieb Roger Goh: > Hi, > > During a VA scan, it's reported that my postfix server has > a security vulnerability : > >EhloCheck: SMTP daemon supports EHLO where exactly is the security hole? you should not trust the output of every tool blind without try to understan

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Noel Jones
On 5/3/2011 10:34 AM, Roger Goh wrote: Hi, During a VA scan, it's reported that my postfix server has a security vulnerability : EhloCheck: SMTP daemon supports EHLO EHLO is not a security vulnerability, rather it is a standard feature of SMTP (not just postfix, but all mail servers).

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Roger B.A. Klorese
On May 3, 2011, at 8:42 AM, Roger Goh wrote: > 1 more question: > > if there's a way to disable EHLO or fixing it via a patch, > how do I verify (without running VA scan) that this EHLO > vulnerability has been fixed? > What vulnerability?! Who doesn't use EHLO?!?! Perhaps you should use a

Re: security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Roger Goh
1 more question: if there's a way to disable EHLO or fixing it via a patch, how do I verify (without running VA scan) that this EHLO vulnerability has been fixed? TIA Roger

security vulnerability : SMTP daemon supports EHLO

2011-05-03 Thread Roger Goh
Hi, During a VA scan, it's reported that my postfix server has a security vulnerability : EhloCheck: SMTP daemon supports EHLO 1. How can I disable EHLO & still send/receive mails? 2. Or is there a later version of postfix (let me know the version) that addresses this or any patch to ap