Firefox encrypted media extensions must be disabled.

An XCCDF Rule

Description

Firefox's Encrypted Media Extensions support playback of media content that is subject to Digital Right Management. These extensions may be disabled completely by setting

Enabled under EncryptedMediaExtensions to false
Locked under EncryptedMediaExtensions to true

Rationale

Enable or disable Encrypted Media Extensions and optionally lock it. If "Enabled" is set to "false", Firefox does not download encrypted media extensions (such as Widevine) unless the user consents to installing them. If "Locked" is set to "true" and "Enabled" is set to "false", Firefox will not download encrypted media extensions (such as Widevine) or ask the user to install them. It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors. Applications are capable of providing a wide variety of functions and services. Some of the functions and services, provided by default, may not be necessary to support essential organizational operations (e.g., key missions, functions). Examples of non-essential capabilities include but are not limited to advertising software or browser plug-ins that are not related to requirements or provide a wide array of functionality not required for every mission but that cannot be disabled.

ID: xccdf_org.ssgproject.content_rule_firefox_policy-encrypted_media_extensions
Severity: Medium
References: CCI-000381

CM-7

FFOX-00-000037
Updated: about 1 year ago


firefox_cfg="policies.json"
# Default to /etc/firefox/policies to use for remediations.
firefox_dirs="/etc/firefox/policies"
permissions=644
declare __REMEDIATE_PYTHON
if [ -x /usr/bin/python ]; then
    __REMEDIATE_PYTHON=/usr/bin/python
elif [ -x /usr/bin/python3 ]; then
    __REMEDIATE_PYTHON=/usr/bin/python3
elif [ -x /usr/bin/python2 ]; then
    __REMEDIATE_PYTHON=/usr/bin/python2
else
    echo "Python required and no python interpreter found."
    exit 1
fi
declare __FIREFOX_DISTRIBUTION
if find /usr -iname firefox\* -type f -print | grep -qe "firefox.sh$\|firefox-bin$"; then
   __FIREFOX_DISTRIBUTION=$(dirname "$(find /usr -iname firefox\* -type f -print | grep -e "firefox.sh$\|firefox-bin$" | head -n1)")/distribution
fi
# If there's a policies file in the distribution directory already, modify it.
if [ -f ${__FIREFOX_DISTRIBUTION}/policies.json ]; then
        firefox_dirs="${__FIREFOX_DISTRIBUTION}"
fi
# Check the possible Firefox install directories
for firefox_dir in ${firefox_dirs}; do
    if ! [ -d "${firefox_dir}" ]; then
        mkdir -p "${firefox_dir}"
        chmod 755 "${firefox_dir}"
    fi
    # Make sure the Firefox .cfg file exists and has the appropriate permissions
    if ! [ -f "${firefox_dir}/${firefox_cfg}" ] ; then
        echo "{" > "${firefox_dir}/${firefox_cfg}"
        echo "    \"policies\": {" >> "${firefox_dir}/${firefox_cfg}"
        echo "    }" >> "${firefox_dir}/${firefox_cfg}"
        echo "}" >> "${firefox_dir}/${firefox_cfg}"
        chmod ${permissions} "${firefox_dir}/${firefox_cfg}"
    fi
    # If the key exists, change it. Otherwise, add it to the config_file.
    if [ -x ${__REMEDIATE_PYTHON} ]; then
        echo """
import json
_file=open('${firefox_dir}/${firefox_cfg}', 'r')
_tree=json.load(_file)
_file.close()


if 'EncryptedMediaExtensions' in _tree['policies']:
   pass
else:
   _tree['policies']['EncryptedMediaExtensions'] = dict()

_tree['policies']['EncryptedMediaExtensions']['Enabled'] = False


if 'EncryptedMediaExtensions' in _tree['policies']:
   pass
else:
   _tree['policies']['EncryptedMediaExtensions'] = dict()

_tree['policies']['EncryptedMediaExtensions']['Locked'] = True

_file=open('${firefox_dir}/${firefox_cfg}', 'w')
json.dump(_tree, _file, indent=4, sort_keys=True)
_file.close()
""" | ${__REMEDIATE_PYTHON}
        chmod ${permissions} "${firefox_dir}/${firefox_cfg}"
    fi
done

Firefox encrypted media extensions must be disabled.

Description

Rationale

Remediation - Shell Script