Firefox must be configured to disable the installation of extensions.

An XCCDF Rule

Description

Addon installation may be disabled in an administrative policy by setting the InstallAddonsPermission key under policies to false.

Rationale

A browser extension is a program that has been installed into the browser to add functionality. Where a plug-in interacts only with a web page and usually a third-party external application (e.g., Flash, Adobe Reader), an extension interacts with the browser program itself. Extensions are not embedded in web pages and must be downloaded and installed in order to work. Extensions allow browsers to avoid restrictions that apply to web pages. For example, an extension can be written to combine data from multiple domains and present it when a certain page is accessed, which can be considered cross-site scripting. If a browser is configured to allow unrestricted use of extensions, plug-ins can be loaded and installed from malicious sources and used on the browser.

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

CM-7

FFOX-00-000013
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 'InstallAddonsPermission' in _tree['policies']:
   pass
else:
   _tree['policies']['InstallAddonsPermission'] = dict()

_tree['policies']['InstallAddonsPermission']['Default'] = False

_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 must be configured to disable the installation of extensions.

Description

Rationale

Remediation - Shell Script