Hello Thomas,
Am 15.02.2022 um 11:38 schrieb Thomas Hoffmann (Speed4Trade GmbH):
Hello Stefan,
by spec / RFC, a HEAD request is not allowed to return any body.
Greetings,
Thomas
This is true and that is why i'm writing to this list. In the described
case mod_jk returns a response body although it should not (at least i
think mod_jk is somehow responsible for that)
-----Ursprüngliche Nachricht-----
Von: Stefan Mayr <ste...@mayr-stefan.de>
Gesendet: Montag, 14. Februar 2022 23:07
An: users@tomcat.apache.org
Betreff: Re: mod_jk interference with ErrorDocument/Alias on HEAD request
Hello again,
a self-compiled mod_jk 1.2.48 shows the same issue.
Am 13.02.2022 um 18:37 schrieb Stefan Mayr:
Hi,
looking at the source code
https://github.com/apache/tomcat-connectors/blob/main/native/apache-2.
0/mod_jk.c#L2954#L2973
I did some more testing:
Variant 1: JkMount /demo/* ajp13_worker;use_server_errors=401
Variant 2: JkMount /demo/* ajp13_worker
ignoring what variant 2 changes for regular request: reading the
source comment my understanding is, that for both variants a HEAD
request (by definition must have an empty response body) should let
Apache httpd handle the error code.
But the return code for jk_handler looks different:
Variant 1: s.http_response_status
Variant 2: r->status
Although this looks different on the first glance it seems to be the same.
The response only seems correct for variant 1 - which is configured to
let Apache httpd handle all responses for status codes >= 401. For
variant 2 mod_jk seems to handle the response itself - contrary to
what the comment explains.
This leads to the next assumption, that whenever there is a special handling
for use_server_errors there should be something similar for the case with an
empty/non-existing response body.
There is
https://github.com/apache/tomcat-connectors/blob/main/native/common/jk_ajp_common.c#L1991#L1993
with no corresponding (pseudo) code like
if (!r->something_like_bodyct && r->http_response_status >=
JK_HTTP_BAD_REQUEST){
r->response_blocked = JK_TRUE;
}
Adding code like this (sorry, i could not find out how to determine if there is
a response body) fixes the issue with the wrong response body for a HEAD
request. But we miss the WWW-Authenticate header now.
Digging further we find
https://github.com/apache/tomcat-connectors/blob/main/native/apache-2.0/mod_jk.c#L331#L353
which has a special treatment for 401 HTTP Unauthorized. But again, only for
use_server_errors.
This should be fixable by extending the condition like this
if ((s->extension.use_server_error_pages &&
status >= s->extension.use_server_error_pages) ||
(!r->sent_bodyct && r->status >= HTTP_BAD_REQUEST)) {
But the WWW-Authenticate header is still missing. So i'm wrong, again.
Although it feels like i'm close.
Am 12.02.2022 um 14:24 schrieb Stefan Mayr:
Hello Tomcat users,
this week we were debugging a strange connection issue which I
tracked down to an interference between Apache httpd and mod_jk.
For the full picture, the infrastructure setup contains
1. a Loadbalancer providing HTTPS, HTTP/1.1 and HTTP/2 for Clients.
2. an Apache httpd 2.4 webserver (HTTP only) with mod_jk 3. a Tomcat
mit AJP-Connector
We have an application doing many different HEAD requests against an
application running in the Tomcat server. The requests contain an
Authorization header for Basic authentication. Expected response is a
HTTP 200 OK or HTTP 401 if this particular user is not allowed to
access that ressource. Because this is a HEAD request there must not
be a response body according to RFC 2616.
If there is a response body in the response to the HEAD request our
loadbalancer does strange things: aborts the connection if the
clients uses HTTP/2, SSL errors if using HTTP/1.1. But this is an
issue on its own which we might have to solve with the vendor.
Now comes the point where I need your help. We have a httpd
configuration with mod_jk which generates these invalid response
bodies on HEAD requests. I have a gut feeling this could be a bug
with mod_jk.
For demonstration purpose i created a minimal demo app which only is
a WEB-INF/web.xml <?xml version="1.0" encoding="UTF-8"?> <web-app
xmlns="https://jakarta.ee/xml/ns/jakartaee";
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee
https://jakarta.ee/xml/ns/jakartaee/web-app_5_0.xsd";
version="5.0">
<security-constraint>
<web-resource-collection>
<web-resource-name>Login</web-resource-name>
<url-pattern>/*</url-pattern>
</web-resource-collection>
<auth-constraint>
<role-name>manager</role-name>
</auth-constraint>
</security-constraint>
<security-role>
<role-name>manager</role-name>
</security-role>
<login-config>
<auth-method>BASIC</auth-method>
</login-config>
</web-app>
Then I place a JkMount in my Apache httpd configuration (+ minimal
worker.properties):
JkMount /demo/* ajp13_worker
Testing this with curl works like expected:
root@1ae8973f1b6b:~# curl -I -v localhost/demo/
* Trying 127.0.0.1:80...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 80 (#0)
> HEAD /demo/ HTTP/1.1
> Host: localhost
> User-Agent: curl/7.68.0
> Accept: */*
>
* Mark bundle as not supporting multiuse < HTTP/1.1 401 401
HTTP/1.1 401 401
< Date: Sat, 12 Feb 2022 12:57:33 GMT
Date: Sat, 12 Feb 2022 12:57:33 GMT
< Server: Apache/2.4.41 (Ubuntu)
Server: Apache/2.4.41 (Ubuntu)
< Cache-Control: private
Cache-Control: private
< WWW-Authenticate: Basic realm="Authentication required"
WWW-Authenticate: Basic realm="Authentication required"
< Content-Language: en
Content-Language: en
< Content-Type: text/html;charset=utf-8
Content-Type: text/html;charset=utf-8
<
* Connection #0 to host localhost left intact
But our default setup always includes custom error pages:
Alias /error/ "/usr/share/apache2/error/"
ErrorDocument 401 /error/HTTP_UNAUTHORIZED.html.var
If both of those lines are added this results in a response body for
the HEAD request.
root@1ae8973f1b6b:~# curl -I -v localhost/demo/
* Trying 127.0.0.1:80...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 80 (#0)
> HEAD /demo/ HTTP/1.1
> Host: localhost
> User-Agent: curl/7.68.0
> Accept: */*
>
* Mark bundle as not supporting multiuse < HTTP/1.1 401 401
HTTP/1.1 401 401
< Date: Sat, 12 Feb 2022 12:56:27 GMT
Date: Sat, 12 Feb 2022 12:56:27 GMT
< Server: Apache/2.4.41 (Ubuntu)
Server: Apache/2.4.41 (Ubuntu)
< Cache-Control: private
Cache-Control: private
< WWW-Authenticate: Basic realm="Authentication required"
WWW-Authenticate: Basic realm="Authentication required"
< Content-Language: en
Content-Language: en
< Content-Type: text/html;charset=utf-8
Content-Type: text/html;charset=utf-8
<
* Excess found: excess = 589 url = /demo/ (zero-length body)
* Connection #0 to host localhost left intact
Checking with tcpdump on port 8009 we see the expected response
without a body from the Tomcat AJP connector. The tcpdump von port 80
reveals httpd is adding the configured ErrorDocument as response body.
If we comment out either the Alias or ErrorDocument directive the
response is correct again.
Doing similar tests with CGI/PHP applications always show the correct
response without a response body. This only affects requests which
use mod_jk.
So far I could reproduce this on SLES12 SP5 and SLES15 SP3 running
Apache httpd 2.4.51 and a self compile mod_jk 1.2.46 (same with the
included mod_jk 1.2.43) at work. At home the same happens on a stock
openSUSE Leap 15.3 with Apache httpd 2.4.51 and mod_jk 1.2.43 as well
as on Ubuntu 20.04 with httpd 2.4.41 and mod_jk 1.2.46.
I didn't try to compile the latest mod_jk version yet because I
didn't spot a relevant point in the changelog.
Can anyone confirm this behaviour or point me to a configuration
directive i missed?
--
Regards,
Stefan Mayr
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