ModSecurity for HAProxy
-----------------------
This is a third party deamon which speaks SPOE. It gives requests send by HAProxy
to ModSecurity and returns the verdict.
Compilation
---------------
You must compile ModSecurity in standalone mode. Below an example for
ModSecurity-2.9.1. Note that ModSecurity depends the Apache APR. I assume that
the Apache dependencies are installed on the system.
./configure \
--prefix=$PWD/INSTALL \
--disable-apache2-module \
--enable-standalone-module \
--enable-pcre-study \
--without-lua \
--enable-pcre-jit
make
make -C standalone install
mkdir -p $PWD/INSTALL/include
cp standalone/*.h $PWD/INSTALL/include
cp apache2/*.h $PWD/INSTALL/include
Note that this compilation method works, but is a litle bit rustic. I can't
deal with Lua, I supposed that is a dependecies problem on my computer.
Start the service
---------------------
After you have compiled it, to start the service, you just need to use "spoa"
binary:
$> ./modsecurity -h
Usage: ./spoa [-h] [-d] [-p <port>] [-n <num-workers>] [-f <config-file>]
-h Print this message
-d Enable the debug mode
-f <config-file> Modsecurity configuration file
-m <max-frame-size> Specify the maximum frame size (default : 16384)
-p <port> Specify the port to listen on (default: 12345)
-n <num-workers> Specify the number of workers (default: 5)
-c <capability> Enable the support of the specified capability
-t <time> Set a delay to process a message (default: 0)
The value is specified in milliseconds by default,
but can be in any other unit if the number is suffixed
by a unit (us, ms, s)
Note: A worker is a thread.
Configure a SPOE to use the service
---------------------------------------
All information about SPOE configuration can be found in "doc/SPOE.txt". Here is
the configuration template to use for your SPOE with ModSecurity module:
[modsecurity]
spoe-agent modsecurity-agent
messages check-request
option var-prefix modsec
timeout hello 100ms
timeout idle 30s
timeout processing 15ms
use-backend spoe-modsecurity
spoe-message check-request
args unique-id method path query req.ver req.hdrs_bin req.body_size req.body
event on-frontend-http-request
The engine is in the scope "modsecurity". So to enable it, you must set the
following line in a frontend/listener section:
frontend my-front
...
filter spoe engine modsecurity config spoe-modsecurity.conf
...
Because, in SPOE configuration file, we declare to use the backend
"spoe-modsecurity" to communicate with the service, you must define it in
HAProxy configuration. For example:
backend spoe-modsecurity
mode tcp
balance roundrobin
timeout connect 5s
timeout server 3m
server modsec1 127.0.0.1:12345
The modsecurity action is returned in a variable called txn.modsec.code. It
contains the HTTP returned code. If the variable contains 0, the request is
clean.
http-request deny if { var(txn.modsec.code) -m int gt 0 }
With this rule, all the request not clean are rejected.
Known bugs, limitations and TODO list
-----------------------------------------
Modsecurity bugs:
-----------------
* When the audit_log is used with the directive "SecAuditLogType Serial", in
some systems, the APR mutex initialisation silently fails, this causes a
segmentation fault. For my own usage, I have a patched version of modsec where
I use another mutex than "APR_LOCK_DEFAULT" like "APR_LOCK_PROC_PTHREAD"
- rc = apr_global_mutex_create(&msce->auditlog_lock, NULL, APR_LOCK_DEFAULT, mp);
+ rc = apr_global_mutex_create(&msce->auditlog_lock, NULL, APR_LOCK_PROC_PTHREAD, mp);
* Configuration file loaded with wilcard (eg. Include rules/*.conf), are loaded
in reverse alphabetical order. You can found a patch below. The ModSecurity
team ignored this patch.
https://github.com/SpiderLabs/ModSecurity/issues/1285
http://www.arpalert.org/0001-Fix-bug-when-load-files.patch
Or insert includes without wildcards.
Todo:
-----
* Clarify the partial body analysis.
* The response body is not yet analyzed.
* ModSecurity can't modify the response body.
* Implements real log management. Actually, the log are sent on stderr.
* Implements daemon things (forks, write a pid, etc.).
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