RE: Un-Able to access some web site thru proxy

  • From: "Thomas W Shinder" <tshinder@xxxxxxxxxxx>
  • To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
  • Date: Mon, 6 Mar 2006 19:03:39 -0600

Will do!
Tom 


Thomas W Shinder, M.D.
Site: www.isaserver.org
Blog: http://blogs.isaserver.org/shinder/
Book: http://tinyurl.com/3xqb7
MVP -- ISA Firewalls


-----Original Message-----
From: Jim Harrison [mailto:Jim@xxxxxxxxxxxx] 
Sent: Monday, March 06, 2006 5:41 PM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Un-Able to access some web site thru proxy

http://www.ISAserver.org

Update (Tom, please update the blog, too)...

PSS has asked me to retract the "go get it" action. 
The official patch will be released soon and you'll see an announcement
here when that happens.

Sorry for any cornfussion.

-------------------------------------------------------
   Jim Harrison
   MCP(NT4, W2K), A+, Network+, PCG
   http://isaserver.org/Jim_Harrison/
   http://isatools.org
   Read the help / books / articles!
-------------------------------------------------------
 

-----Original Message-----
From: Thomas W Shinder [mailto:tshinder@xxxxxxxxxxx] 
Sent: Sunday, March 05, 2006 10:08
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Un-Able to access some web site thru proxy

http://www.ISAserver.org

You betchum! :) 


Thomas W Shinder, M.D.
Site: www.isaserver.org
Blog: http://blogs.isaserver.org/shinder/
Book: http://tinyurl.com/3xqb7
MVP -- ISA Firewalls


-----Original Message-----
From: Jim Harrison [mailto:Jim@xxxxxxxxxxxx]
Sent: Sunday, March 05, 2006 11:57 AM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Un-Able to access some web site thru proxy

http://www.ISAserver.org

Wurksfermi!
Thanx, Tom.

-------------------------------------------------------
   Jim Harrison
   MCP(NT4, W2K), A+, Network+, PCG
   http://isaserver.org/Jim_Harrison/
   http://isatools.org
   Read the help / books / articles!
-------------------------------------------------------
 

-----Original Message-----
From: Thomas W Shinder [mailto:tshinder@xxxxxxxxxxx]
Sent: Sunday, March 05, 2006 09:52
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Un-Able to access some web site thru proxy

http://www.ISAserver.org

Hi Jim,

This OK?

http://blogs.isaserver.org/shinder/isacentral/2006/03/05/explanation-on-
the-502-error-to-delta-and-sun-sites/

Tom 


Thomas W Shinder, M.D.
Site: www.isaserver.org
Blog: http://blogs.isaserver.org/shinder/
Book: http://tinyurl.com/3xqb7
MVP -- ISA Firewalls


-----Original Message-----
From: Jim Harrison [mailto:Jim@xxxxxxxxxxxx]
Sent: Sunday, March 05, 2006 11:23 AM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Un-Able to access some web site thru proxy

http://www.ISAserver.org

MJ,

Disabling filters may not help with www.delta.com, www.sun.com or any
site that causes ISA 2004 SP2 to generate the following message:

Error Code: 502 Proxy Error. The HTTP request includes a non-supported
header. Contact your ISA Server administrator. (12156)

The reason for the behavior you're seeing is that new logic that was
added in ISA 2004 SP2 to mitigate HTTP request smuggling.  The process
for this attack is a bit involved but the short story is that HRS
depends on sending response headers that include both "Content-length:
<anyvalue>" and "transfer-encoding: chunked".  
A whitepaper on the subject is available here:
https://www.watchfire.com/securearea/whitepapers.aspx 

RFC-2616 defines those two headers for the purpose of providing
quantitative content validation for the receiver and states *very
clearly* that the server MUST NOT combine them in the same response.  If
the server is configured such that it does violate this edict, RFC-2616
then requires the receiving entity to ignore the content-length value
and instead use the chunked-encoding technique to validate the length of
the HTTP body.  This places a processing burden on the receiving entity
(ISA, in this case), since a chunked-encoded transfer can't be
quantitatively validated until the transfer is completed.  In the case
of a proxy, additional processing is imposed due to caching behavior
that may be dependent on content-size.

The reason those sites are either failing outright (www.delta.com) or
rendering poorly (www.sun.com) is because we chose to reject those
responses out-of-hand.  Since RFC-2616 clearly states "don't combine
those headers" and doing so is a demonstrably malicious act, it seemed
unlikely that ISA would cause problems for any other than malicious
sites, and in fact, our testing validated this belief.  As it turns out,
there are quite a few legitimate sites out there that violate this part
of RFC-2616 and so we have had to rethink our answer to this problem.

Call PSS.
Tell them I sent you.
Ask for the private fix for ISA SE 34978.
Do
It
Now

Jim

-----Original Message-----
From: MJ [mailto:mjtech@xxxxxxxxx]
Sent: Sunday, March 05, 2006 7:56 AM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Un-Able to access some web site thru proxy

http://www.ISAserver.org

I got it to open by copying both lines.

I followed everything in it, and since we are only using the proxy part
of this ISA box I disabled everything as the article said, and restart
the firewall service, but I am still having the same problem.

I also read the ISA 2004 SP2 white paper but didn't see anything that
will help in this situation.

Any other ideas?

Thanks for you responses.



-----Original Message-----
From: Jim Harrison [mailto:Jim@xxxxxxxxxxxx]
Sent: Sunday, March 05, 2006 1:42 AM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Un-Able to access some web site thru proxy

http://www.ISAserver.org

Unwrap it.
The second line is part of the URL.

-----Original Message-----
From: MJ [mailto:mjtech@xxxxxxxxx]
Sent: Saturday, March 04, 2006 9:06 PM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Un-Able to access some web site thru proxy

http://www.ISAserver.org

Tom,

Thanks for the response, but the link you posted took me to "Error 404 -
Not Found"

I thin the document was moved somewhere else.

Thanks again.

-----Original Message-----
From: Thomas W Shinder [mailto:tshinder@xxxxxxxxxxx]
Sent: Saturday, March 04, 2006 10:54 PM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Un-Able to access some web site thru proxy

http://www.ISAserver.org

http://blogs.isaserver.org/shinder/news/2006/02/27/isa-firewall-sp-2-bra
nch-office-features-turn-em-off

HTH,
Tom


Thomas W Shinder, M.D.
Site: www.isaserver.org
Blog: http://blogs.isaserver.org/shinder/
Book: http://tinyurl.com/3xqb7
MVP -- ISA Firewalls


-----Original Message-----
From: Bryan [mailto:mjtech@xxxxxxxxx]
Sent: Saturday, March 04, 2006 7:02 PM
To: [ISAserver.org Discussion List]
Subject: [isalist] Un-Able to access some web site thru proxy

http://www.ISAserver.org

Hi *.*

We have ISA 2004 server that is working fine so far. After installing
SP2
things continue to work fine except one little problem:
When we try to access some web sites such as www.delta.com we're getting
the following message:
========================================================================
===

Technical Information (for support personnel) Error Code: 502 Proxy
Error. The HTTP request includes a non-supported header. Contact your
ISA Server administrator. (12156) IP Address: 205.174.16.50
Date: 3/5/2006 12:53:52 AM
Server: isaServerName.DomainName.com
Source: proxy
========================================================================
===


I am looking for a solution for this problem other than un-installing
SP2
because it really fixed more serious problems than this problem.
Also other than chaining to another ISA server with SP1.

The Result of my research indicated that this a bug with SP2, and
Microsoft is working on a hotfix for, which will be out some time soon.

just to let you all know I have contact MS Support as well, and they
told me the same thing, but because I know that there smart guys in this
list I thought of posting the question any ways hoping that some has a
work around till the hotfix is available.
MS Support will get back with me on Monday and they may have one of the
developers work with me to fix the problem Manually and if this happen I
promise I will post the solution here for whoever might come across the
same issue.

Thanks a lot guys and have a great day

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