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From Mark Thomas <ma...@apache.org>
Subject Re: Tomcat (v 6.0.32) write response to wrong client socket
Date Wed, 09 Jul 2014 09:49:01 GMT
On 09/07/2014 08:43, Yanchun.Yang@finnova.ch 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):
> 10.25.4.8 - - 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):
> 10.25.4.8 - - 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
> vhost:wwwsec.zrb.clientis.ch:443 (https) POST /ebanking/defAccountStatementOfAccount.account
=> https://10.25.2.43:5215/finprdzrb/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:84.74.211.190  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
> vhost:wwwsec.oberuzwil.clientis.ch:443 (https) GET /ebanking/defAccountStartPage.account?DIRTY=Y&DEFAULT=1&node=STARTSEITE
=> https://10.25.2.43:5215/finprdcbo/defAccountStartPage.account , 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:84.73.20.65  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
http://tomcat.apache.org/security-6.html

> 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.

Mark


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