Integrating ATS with ModSecurity V3 using LuaJIT and FFI

Opensource WAF for Apache Traffic Server.

Requirement

• ModSecurity v3.0.4
• ATS 8.0.8

How to Use

• Copy all lua files to /usr/local/var/lua
• Put the example modsecurity rule file (example.conf) to /usr/local/var/modsecurity , readable by the ATS process
• Add a line in /usr/local/etc/trafficserver/plugin.config and restart ats

tslua.so --enable-reload /usr/local/var/lua/ats-luajit-modsecurity.lua /usr/local/var/modsecurity/example.conf

• Changes can be made to example.conf and can be reloaded without restarting ATS. Just follow instructions here

Contents/Rules inside example.conf

• deny any request with query parameter of testparam=test2 with a 403 status response
• return any request with query parameter of testparam=test1 with 301 redirect response to https://www.yahoo.com/
• override any response with header test equal to 1 with a 403 status response
• override any response with header test equal to 2 with a 301 redirect response to https://www.yahoo.com/
• write debug log out to /tmp/debug.log

Working with CRS

• Go to here and get release v3.2.0
• Uncompress the contents and copy crs-setup.conf.example to /usr/local/var/modsecurity and rename it to crs-setup.conf
• Copy all files in rules directory to /usr/local/var/modsecurity/rules
• Copy owasp.conf in this repository to /usr/local/var/modsecurity
• Change /usr/local/etc/trafficserver/plugin.config to add the following line and restart ats

tslua.so --enable-reload /usr/local/var/lua/ats-luajit-modsecurity.lua /usr/local/var/modsecurity/owasp.conf

• The following example curl command against your server should get a status 403 Forbidden response

curl -v -H "User-Agent: Nikto" 'http://<your server>/'

Extra Notes with CRS

• Please check out this link for performance related information
• To turn on debugging, you can uncomment the following inside owasp.conf

SecDebugLog /tmp/debug.log
SecDebugLogLevel 9

• Rule ID 910100 in REQUEST-910-IP-REPUTATION.conf in rules directory requires GeoIP and have to be commented out if you do not built the modsecurity library with it.
• We use SecRuleRemoveById inside owasp.conf to remove rules checking for request and response body. This trick can be used to remove other rules that does not apply well in some situations

TODOs/Limitations

• No support for REQUEST_BODY examination (We need to buffer the request body for examination first before we send to origin.)
• No support for RESPONSE BODY examination (We need to uncompress the contents first if they are gzipped. And that will be expensive operation for proxy)
• How does this work with the lua engine inside ModSecurity V3?
• Unit Test using busted framework
• More functional testing needed
• Performance testing - impact to latency and capacity