unsafe-browser

#!/bin/sh

set -e
set -u

# Import tor_is_working()
. /usr/local/lib/tails-shell-library/tor.sh

# Import the TBB_EXT variable, and guess_best_tor_browser_locale().
. /usr/local/lib/tails-shell-library/tor-browser.sh

# Import localized_tails_doc_page().
. /usr/local/lib/tails-shell-library/localization.sh

# Import try_cleanup_browser_chroot(), setup_browser_chroot(),
# configure_chroot_dns_servers(), configure_chroot_browser(),
# configure_chroot_browser(), set_chroot_browser_locale()
# set_chroot_browser_name(), set_chroot_browser_permissions()
# and run_browser_in_chroot().
. /usr/local/lib/tails-shell-library/chroot-browser.sh

error () {
    local cli_text="${CMD}: `gettext \"error:\"` ${@}"
    local dialog_text="<b><big>`gettext \"Error\"`</big></b>

${@}"
    echo "${cli_text}" >&2
    sudo -u "${SUDO_USER}" zenity --error --title "" --text "${dialog_text}"
    exit 1
}

verify_start () {
    # Make sure the user really wants to start the browser
    local dialog_msg="<b><big>`gettext \"Do you really want to launch the Unsafe Browser?\"`</big></b>

`gettext \"Network activity within the Unsafe Browser is <b>not anonymous</b>.\\nOnly use the Unsafe Browser if necessary, for example\\nif you have to login or register to activate your Internet connection.\"`"
    local launch="`gettext \"_Launch\"`"
    local exit="`gettext \"_Exit\"`"
    # Since zenity can't set the default button to cancel, we switch the
    # labels and interpret the return value as its negation.
    if sudo -u "${SUDO_USER}" zenity --question --title "" --ok-label "${exit}" \
       --cancel-label "${launch}" --text "${dialog_msg}"; then
        exit 0
    fi
}

show_start_notification () {
    local title="`gettext \"Starting the Unsafe Browser...\"`"
    local body="`gettext \"This may take a while, so please be patient.\"`"
    tails-notify-user "${title}" "${body}" 10000
}

show_shutdown_notification () {
    local title="`gettext \"Shutting down the Unsafe Browser...\"`"
    local body="`gettext \"This may take a while, and you may not restart the Unsafe Browser until it is properly shut down.\"`"
    tails-notify-user "${title}" "${body}" 10000
}

maybe_restart_tor () {
    # Restart Tor if it's not working (a captive portal may have prevented
    # Tor from bootstrapping, and a restart is the fastest way to get
    # wheels turning)
    if ! tor_is_working; then
        echo "* Restarting Tor"
        restart-tor
        if ! systemctl --quiet is-active tor@default.service; then
            error "`gettext \"Failed to restart Tor.\"`"
        fi
    fi
}

# Main script:

CMD="$(basename "${0}")"
LOCK="/var/lock/${CMD}"

. gettext.sh
TEXTDOMAIN="tails"
export TEXTDOMAIN

CONF_DIR="/var/lib/unsafe-browser"
COW="${CONF_DIR}/cow"
CHROOT="${CONF_DIR}/chroot"
BROWSER_NAME="unsafe-browser"
BROWSER_USER="clearnet"
HUMAN_READABLE_NAME="`gettext \"Unsafe Browser\"`"
NM_ENV_FILE="/var/lib/NetworkManager/env"
WARNING_PAGE='/usr/share/doc/tails/website/misc/unsafe_browser_warning'
HOME_PAGE="$(localized_tails_doc_page "${WARNING_PAGE}")"

# Prevent multiple instances of the script.
exec 9>"${LOCK}"
if ! flock -x -n 9; then
    error "`gettext \"Another Unsafe Browser is currently running, or being cleaned up. Please retry in a while.\"`"
fi

# Get the DNS servers that was obtained from NetworkManager, if any...
if [ -r "${NM_ENV_FILE}" ]; then
    # We also check that the file we are gonna *source* doesn't
    # contain any unexpected data, like (potentially malicious) shell
    # script. Note that while the regex used for deciding IP addresses
    # is far from perfect, it serves our purpose here.
    IP4_REGEX='[0-9]{1,3}(\.[0-9]{1,3}){3}'
    NAMESERVERS_REGEX="^IP4_NAMESERVERS=\"(${IP4_REGEX}( ${IP4_REGEX})*)?\"$"
    if grep --extended-regexp -qv "${NAMESERVERS_REGEX}" "${NM_ENV_FILE}"; then
        error "`gettext \"NetworkManager passed us garbage data when trying to deduce the clearnet DNS server.\"`"
    fi
    # Import the IP4_NAMESERVERS variable.
    eval "$(grep --extended-regexp "${NAMESERVERS_REGEX}" "${NM_ENV_FILE}")"
fi
# ... otherwise fail.
# FIXME: Or would it make sense to fallback to Google's DNS or OpenDNS?
# Some stupid captive portals may allow DNS to any host, but chances are
# that only the portal's DNS would forward to the login page.
if [ -z "${IP4_NAMESERVERS}" ]; then
    error "`gettext \"No DNS server was obtained through DHCP or manually configured in NetworkManager.\"`"
fi

verify_start
show_start_notification

echo "* Setting up chroot"
setup_chroot_for_browser "${CHROOT}" "${COW}" "${BROWSER_USER}" || \
    error "`gettext \"Failed to setup chroot.\"`"

echo "* Configuring chroot"
configure_chroot_browser "${CHROOT}" "${BROWSER_USER}" "${BROWSER_NAME}" \
    "${HUMAN_READABLE_NAME}" "${HOME_PAGE}" "${IP4_NAMESERVERS}" \
    "${TBB_EXT}"/langpack-*.xpi || \
        error "`gettext \"Failed to configure browser.\"`"

echo "* Starting Unsafe Browser"
run_browser_in_chroot "${CHROOT}" "${BROWSER_NAME}" "${BROWSER_USER}" \
    "${SUDO_USER}" || \
    error "`gettext \"Failed to run browser.\"`"

echo "* Exiting the Unsafe Browser"
show_shutdown_notification
maybe_restart_tor

exit 0