All,
On 4/18/24 10:16, Adwait Kumar Singh wrote:
I think we should *always* close connections in cases where it can lead to
request smuggling vulnerabilities like when there is an error during header
or request line parsing, but allowing the user to control connection close
when the status is being set by the user, should be safe?
It allows users to send back responses like InvalidInputException with a
400 status without being forced to close the connection.
Maybe the behavior depends upon the source of the response code. If
Tomcat itself determines that the connection should be terminated, it
should. But if the application is the one returning the 4xx error,
Tomcat should not terminate the connection.
Does that sound like a decent compromise and is it even possible to
differentiate?
-chris
On Thu, Apr 18, 2024 at 6:41 AM Rémy Maucherat <r...@apache.org> wrote:
On Thu, Apr 18, 2024 at 1:17 PM Mark Thomas <ma...@apache.org> wrote:
On 18/04/2024 09:07, Stefan Ansing wrote:
Hi,
We've observed some unexpected behaviour in Apache Tomcat (version
10.1.19)
where we see that HTTP/1.1 connections are closed whenever a servlet
application returns the following status codes: 400, 408, 411, 414,
500,
503, 501. This causes client applications to rapidly reconnect and
induce
high server-side CPU load due to doing TLS handshakes.
The 400 and 500 status codes are commonly used in RESTful
microservices to
communicate errors. Reviewing RFC 9112 I couldn't find any requirement
for
closing connections on these status codes.
After testing with Undertow (version 2.3.12), where we didn't see the
same
behaviour, we believe that these status codes do not necessitate a new
connection.
The Tomcat developers disagree. Connections are closed after these
status codes to avoid various forms of request smuggling attacks.
Checking the Tomcat sources makes me believe that the behaviour is
hard-coded[1]. I'm reaching out here to re-evaluate the list of status
codes and to discuss the possibilities of making the behaviour
configurable.
Making this list of status codes configurable seems reasonable. The
default can stay as current and if users want to change it then they
have to accept the associated security risks.
If it's insecure, then it would still be a valid CVE even if the
configuration is optional. We don't have an "allowSmuggling" attribute
on the connector to relax header or status line parsing, even though
many would have wanted it in the past ...
Rémy
Mark
A colleague of mine reported a bug for this issue:
https://bz.apache.org/bugzilla/show_bug.cgi?id=68901
Kind regards,
Stefan Ansing
[1]:
https://github.com/apache/tomcat/blame/bc900e0100de9879604b93af4722c272ab3d1a24/java/org/apache/coyote/http11/Http11Processor.java#L604-L617
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