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Custom ModSecurity Modules
--------------------------
This directory contains three examples how you can extend
ModSecurity without having to touch it directly, simply
by creating custom Apache modules.
NOTE: ModSecurity must be compiled with API support
to use this feature (the API is enabled by default,
but it will have been disabled if you used -DNO_MODSEC_API).
Building the Example Custom Modules
-----------------------------------
1) Example custom transformation function module
Module mod_tfn_reverse.c creates a custom transformation
function "reverse" that reverses the content it receives
on input.
# Compile as a normal user
apxs -I<MODSECURITY_SOURCE_CODE> -I/usr/include/libxml2 \
-ca mod_tfn_reverse.c
# Install as superuser
sudo apxs -i mod_tfn_reverse.la
2) Example custom operator module
Module mod_op_strstr.c creates a custom operator "strstr"
that implements fast matching using the Boyer-Moore-Horspool
algorithm.
# Compile as a normal user
apxs -I<MODSECURITY_SOURCE_CODE> -I/usr/include/libxml2 \
-ca mod_op_strstr.c
# Install as superuser
sudo apxs -i mod_op_strstr.la
3) Example custom target variable module
Module mod_var_remote_addr_port.c creates a custom variable "REMOTE_ADDR_PORT"
that combines the REMOTE_ADDR and REMOTE_PORT into a.b.c.d:port format.
# Compile as a normal user
apxs -I<MODSECURITY_SOURCE_CODE> -I/usr/include/libxml2 \
-ca mod_var_remote_addr_port.c
# Install as superuser
sudo apxs -i mod_var_remote_addr_port.la
3) Example custom request body parser module
Module mod_reqbody_example.c creates a custom request body parser named
"EXAMPLE". It does noting in particular, but shows the basic structure
of such a module.
# Compile as a normal user
apxs -I<MODSECURITY_SOURCE_CODE> -I/usr/include/libxml2 \
-ca mod_reqbody_example.c
# Install as superuser
sudo apxs -i mod_var_remote_addr_port.la
# Write a phase 1 rule to set the parser
SecAction "phase:1,pass,nolog,ctl:requestBodyProcessor=EXAMPLE"
Using the Modules
-----------------
Once the modules are built and installed, you load them like any other Apache module, but they must be loaded *after* the mod_security2.so module.
# Load ModSecurity
LoadModule security2_module modules/mod_security2.so
# Load ModSecurity custom modules
LoadModule tfn_reverse_module modules/mod_tfn_reverse.so
LoadModule op_strstr_module modules/mod_op_strstr.so
LoadModule var_remote_addr_port_module modules/mod_var_remote_addr_port.so
# All three custom var/op/tfn used
SecRule REMOTE_ADDR_PORT "@strstr 1.2.3.4:5678" "t:reverse"
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