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Subject AW: Tomcat (v 6.0.32) write response to wrong client socket
Date Mon, 14 Jul 2014 10:25:25 GMT
Hello Mark,

thank you for your answer. According to your informations I did some research as following:
1. I have looked for the key words of mix and response in
and in,  
And I got only one bug fix report of CVE-2011-1475 in this context. but it is not the same
case like ours, because:
	1. the bug is concerning BIO, but in our case it is NIO connector (Http11NioProtocol)
	2. it 's Tomcat 7.X but we got the problem on Tomcat 6.0.32

2. CVE-2011-3375 is about information leakage when certain error occurs and therefor is not
applicable to this case

3. I checked all of the filters and servlets in our application again and cannot find the
case of retaining a reference to the response and/or request objects beyond a single request
or any clues of thread unsafe.

The problem muss happed when the two requests income (income at the same time but response
time various ).  Is it somehow possible that tomcat mix them up ?
Any other suggestions?

Thank a lot for your effort!

Yanchun Yang

-----Urspr√ľngliche Nachricht-----
Von: Mark Thomas [mailto:] 
Gesendet: Mittwoch, 9. Juli 2014 11:49
An: Tomcat Users List
Betreff: Re: Tomcat (v 6.0.32) write response to wrong client socket

On 09/07/2014 08:43, wrote:
> Hello,
> We got a serious problem on our online banking applications: a user U1 of bank A got
to see the data of another user U2 of another bank B.
> It happened only once, before and after that went everything well.
> The two same online banking applications are running on one instance of tomcat (V.6.0.32)
and have different backend path.

That is quite an old version with a number of public security vulnerabilities to be using
for a banking application.

> The logs show that the problem must be not on the side of web application (frontend),
backend and firewall. The scenario looks as following:
> 1.      U1 log on the online banking of bank A and U2 log on the online banking of
> bank B, and the two sessions have been running well a while till
> 2.      later at the exactly same time U1 wanted to see the start page and U2
> booking
> detail
> 3.      U1 got to see the false data of the booking detail of U2.
> 4.         after that the two sessions went further well without any problem
> In the access log of the tomcat seems everything went well:
> Access log Bank A (U1):
> - - F862B9AD5DA9AC4A0D38B46D4E5B0D6C [15/Jun/2014:16:03:41 
> +0200]
> HTTP/1.1 GET /finprdcbo/defAccountStartPage.account
> ?DIRTY=Y&DEFAULT=1&node=STARTSEITE 200 69000 
> /ebanking/defAccountStatementDetail.account Mozilla/5.0 (Macintosh; 
> Intel Mac OS X 10.9; rv:29.0) Gecko/20100101 Firefox/29.0
> Access log Bank B (U2):
> - - 12A6E21F0D6321A95C553B160DBCC9A0 [15/Jun/2014:16:03:40 
> +0200]
> HTTP/1.1 POST /finprdzrb/defAccountStatementOfAccount.account  200 
> 45765 /ebanking/defAccountAssetOverview.account Mozilla/5.0 (X11; 
> Linux i686;
> rv:24.0) Gecko/20100101 Firefox/24.0

These logs show the requests coming from the same IP address. Since the requests are from
different users then there must be something acting as a reverse proxy. Is it the firewall?
Is it some other component?

> But the response of the request for booking detail from U2 was 
> mistakenly sent to U1.  We can confirm this by looking into the logs 
> of firewall as
> following:
> Firewall log of Session U2:
> Jun 15 16:04:16  Web-Requests Access m:WR-SG-SUMMARY
> (https) POST 
> /ebanking/defAccountStatementOfAccount.account => 
> , status:<n/a> , redirection URL:<n/a> , 
> referer:/ebanking/defAccountAssetOverview.account , mapping:blappl-zrb 
> , request size: 1089 , backend response size: <n/a> , audit
> token:308792478954626740 rid:U52nvH8AAAEAAAoy1CIAAAno
> sid:384490af19eb229b7f0874b6ef0323c8 ip:  12
> Fact :  "backend response size: <n/a>" means there is no reponse from 
> tomcat for the request of  POST 
> /ebanking/defAccountStatementOfAccount.account and a timeout is 
> trigged
> Firewall log of Session U1:
> Jun 15 16:03:40  Web-Requests Access SG_child[14145]: m:WR-SG-SUMMARY
> (https) GET 
> /ebanking/defAccountStartPage.account?DIRTY=Y&DEFAULT=1&node=STARTSEIT
> E => , 
> status:200 , redirection URL:<n/a> , 
> referer:/ebanking/defAccountStatementDetail.account , 
> mapping:blappl-cbo , request size: 614 , backend response size: 45765 
> , audit
> token:147310158715306970 request total 287469 , allow/deny filters 
> 3780 , backend responsiveness 208455 , response processing 74282 , 
> ICAP reqmod <n/a> , ICAP respmod <n/a> rid:U52nvH8AAAEAAATYu6cAAATi 
> sid:1dad4372b4a2f67d980e6e195aa954fe ip:  12
> Fact: "backend response size: 45765" means the reponse of Request of 
> U2 is mistakenly passed to U1. See the same size of the response in 
> the access log Bank B (U2):s

The firewall appears to be transforming the URL. That suggests it is the firewall that is
acting as the reverse proxy. (Aside: Transforming the URL like this is doable but does require
very careful configuration to ensure everything still works properly)

> My questions:
> 1.      Is such a problem (bug) already known?

Have you looked in the changelog?
Mixing up responses would be a security issue so have you looked in

> 2.      When will the tomcat access log be written? after sent of response or
> before?

It isn't quite that simple. In Tomcat 6 (it changes in 7.0.x) the access log is written after
the application has finished writing the response to the buffer but before the content of
that buffer is written to the client.

> 3.      how could the problem happen on the side of tomcat?

Depending on exactly how the application works, CVE-2011-3375 might be able to trigger this
but given that requires an error to occur it looks unlikely.

> 4.      how could the problem be hidden otherwise?

Most errors of this type are eventually traced to application errors.
The most frequent error is the application retaining a reference to the response and/or request
objects beyond a single request.


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