cis-apache24-5.17

DevOps & Security

Ensure HTTP Header Referrer-Policy is set appropriately

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Server_Software/Apache_HTTP_Server/CIS_Apache_HTTP_Server_2.4_Benchmark_v2.3.0/cis-apache24-5.17/SKILL.md

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Ensure HTTP Header Referrer-Policy is set appropriately (Manual)

Profile Applicability

Level 2

Description

The server now allows for controlling the amount of "referrer" information being sent with requests. Limiting information to only what is needed is security best practice.

Rationale

HTTP/S traffic is vulnerabe to attack - limiting what is sent in a request to only what is needed will limit the threat vector.

Impact

You must only limit the header information to what is needed to support the request. Limiting it to much may disrupt the ability to get a proper/expected response.

Audit Procedure

Perform the following steps to determine if the recommended state is implemented:

Ensure a Header directive for Referrer-Policy is present in the Apache configuration and has the condition Header Set 'Referrer-Policy' shown below:
```
# grep -I Referrer-Policy $APACHE_PREFIX/conf/httpd.conf
```
```
Header set Referrer-Policy "<Directive>"
```

If header Referrer-Policy configuration is present and has as a compliant value, then the server is compliant.

Remediation

Perform the following to implement the recommended state:

Add or modify the Header directive for the Referrer-Policy header in the Apache configuration to have the appropriate condition as shown below.

Header set Referrer-Policy "<Directive>"

Default Value

Referrer-Policy Policy is not set by Default

References

CIS Controls

v8:

9.4 Restrict Unnecessary or Unauthorized Browser and Email Client Extensions
- Restrict, either through uninstalling or disabling, any unauthorized or unnecessary browser or email client plugins, extensions, and add-on applications.
13.10 Perform Application Layer Filtering
- Perform application layer filtering. Example implementations include a filtering proxy, application layer firewall, or gateway.

v7:

9.4 Apply Host-based Firewalls or Port Filtering
- Apply host-based firewalls or port filtering tools on end systems, with a default-deny rule that drops all traffic except those services and ports that are explicitly allowed.
18.2 Ensure Explicit Error Checking is Performed for All In-house Developed Software
- For in-house developed software, ensure that explicit error checking is performed and documented for all input, including for size, data type, and acceptable ranges or formats.