cis-apache24-8-4

name	cis-apache24-8.4
description	Ensure ETag Response Header Fields Do Not Include Inodes (Automated)
category	cis-apache
version	2.3.0
author	cyberstrike-official
tags	["cis","apache","linux","information-leakage","etag","inodes"]
cis_id	8.4
cis_benchmark	CIS Apache HTTP Server 2.4 Benchmark v2.3.0
tech_stack	["linux","apache"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

Ensure ETag Response Header Fields Do Not Include Inodes (Automated)

Profile Applicability

• Level 2

Description

The FileETag directive configures the file attributes that are used to create the ETag (entity tag) response header field when the document is based on a static file. The ETag value is used in cache management to save network bandwidth. The value returned may be based on combinations of the file inode, the modification time, and the file size.

Rationale

When the FileETag is configured to include the file inode number, remote attackers may be able to discern the inode number from returned values. The inode is considered sensitive information, as it could be useful in assisting in other attacks.

Audit

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

For the server and all virtual host and directory configurations verify that either

1. The FileETag directive is not present, or
2. The configured FileETag value does not contain any of the values all or inode or +inode.

Remediation

Perform the following to implement the recommended state:

Remove all instances of the FileETag directive. Alternatively, add or modify the FileETag directive in the server and each virtual host configuration to have either the value None or MTime Size.

Default Value

The default value is MTime Size.

References

1. http://httpd.apache.org/docs/2.4/mod/core.html#FileETag
2. https://nvd.nist.gov/vuln/detail/CVE-2003-1418

CIS Controls

v8:

• 9.2 Use DNS Filtering Services
  • Use DNS filtering services on all enterprise assets to block access to known malicious domains.

v7:

• 7.4 Maintain and Enforce Network-Based URL Filters
  • Enforce network-based URL filters that limit a system's ability to connect to websites not approved by the organization. This filtering shall be enforced for each of the organization's systems, whether they are physically at an organization's facilities or not.