ModSecurity: Block all IPs except for a list of defined IPs

Question

I have an apache server with ModSecurity. I need to block all IPs except for a few ones.

The list of IPs is like this:

194.83.128.0/21
191.143.32.0/19
145.126.72.0/21
101.28.248.0/22
40.64.64.0/22
180.11.124.0/22
190.230.64.0/18
109.154.0.0/16
42.60.0.0/16
43.223.0.0/16
2a03:e980::/29

Right now I applied this rule:

SecRule REMOTE_ADDR "@ipMatch 194.83.128.0/21,191.145.32.0/19,145.126.72.0/21,101.28.248.0/22,40.64.64.0/22,180.11.124.0/22,190.230.64.0/18,109.154.0.0/16,42.60.0.0/16,43.223.0.0/16,2a03:e980::/29" "id:162"

But the rule above seems to be doing a whitelist rather than blocking all IPs except for the ones defined in the rule.

I'm not sure how to achieve blocking all IPs except the ones on my list. Most of the documentation I have found is related to blocking or adding IPs to a deny list, when some action happens, like constantly accessing 404 pages.

Is there a way to block by default all the IPs, except the ones defined in my list?

Answer 1

There are a couple options that you can use here.

1. Just use Apache core. I'm assuming you have Apache 2.4. You can use the Require Directive:

<RequireAny>
    #IPv4 ranges to allow
    Require ip 194.83.128.0/21
    Require ip 191.143.32.0/19
    ...
</RequireAny>

This will allow only the IPs you add to that list.

2. Use modsecurity in Apache.

The rule you want is to do something similar to:

SecRule REMOTE_ADDR "@ipMatch 194.83.128.0/21,191.143.32.0/19,..." "id:50000,phase:1,nolog,allow,ctl:ruleEngine=Off"

Adding all your IP CIDR ranges on that list.

Optionally you can use store that list in a file (in this example, ips.txt) with one cidr range per line and use the @ipMatchFromFile operator:

SecRule REMOTE_ADDR "@ipMatchFromFile ips.txt" "id:50001,phase:1,nolog,allow,ctl:ruleEngine=Off"

In the modsecurity rule I added the nolog action so you won't see any matches from those IPs. If you want to take a peek and see that they are being recognized, use log instead.

Warning Note: please be 100% sure that no attacks are coming from your networks. Pay special attention to SSRF. Because this will disable modsecurity entirely from anything coming from your listed IP ranges.