Ensure ETag Response Header Fields Do Not Include Inodes

LowLevel 2Automatedapache

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. No FileETag directive may include All, INode or +INode (absent is compliant; the default is MTime Size). Reads the main configuration (APACHE_CONF overrides; default /etc/apache2/apache2.conf, /etc/httpd/conf/httpd.conf or /usr/local/apache2/conf/httpd.conf) and every Include/IncludeOptional file.

How it is checked

Audit method: Shell command

shell

c=${APACHE_CONF:-}; if [ -z "$c" ]; then for f in /etc/apache2/apache2.conf /etc/httpd/conf/httpd.conf /usr/local/apache2/conf/httpd.conf /etc/apache2/httpd.conf; do [ -f "$f" ] && { c=$f; break; }; done; fi; [ -r "$c" ] || exit 1; R=$(awk 'tolower($1)=="serverroot"{v=$2; gsub(/"/,"",v); print v; exit}' "$c"); [ -n "$R" ] || R=$(dirname "$c"); shopt -s nocasematch; inc(){ local p g l; [ ${#FUNCNAME[@]} -lt 16 ] || return 0; p=$1; case $p in /*) ;; *) p=$R/$p;; esac; [ -d "$p" ] && p="$p/*"; for g in $p; do [ -f "$g" ] || continue; while IFS= read -r l || [ -n "$l" ]; do if [[ $l =~ ^[[:space:]]*include(optional)?[[:space:]]+\"?([^\"[:space:]]+) ]]; then inc "${BASH_REMATCH[2]}"; else printf '%s\n' "$l"; fi; done < "$g"; done; }; cfg=$(inc "$c" | sed -e 's/^[[:space:]]*//' -e '/^#/d' -e '/^$/d'); shopt -u nocasematch; printf '%s\n' "$cfg" | awk 'tolower($1)=="fileetag"{for(i=2;i<=NF;i++){t=tolower($i); if(t=="all"||t=="inode"||t=="+inode") bad=1}} END{print bad?"noncompliant":"compliant"}'

Expected output: compliant

How it is fixed

Fix method: Guidance or infrastructure patch

Remove FileETag or set FileETag None (or MTime Size). Then run apachectl configtest and reload Apache.

Properties

Operating systems: Any
Tags: apacheinformation-disclosure
Reference: CIS Apache HTTP Server 2.4 Benchmark v2.4.0 - 8.4 Ensure ETag Response Header Fields Do Not Include Inodes

Check this host

Run this on a machine you are allowed to audit. The scan is read-only.

shell

tmaegis scan --target apache --level 2