#!/bin/bash
#  _____               _           _
# |   __|___ ___ ___ _| |___ _____| |_ ___ ___ ___
# |   __|  _| -_| -_| . | . |     | . | . |   | -_|
# |__|  |_| |___|___|___|___|_|_|_|___|___|_|_|___|
#
#                              Freedom in the Cloud
#
# Random number generation functions
#
# License
# =======
#
# Copyright (C) 2014-2018 Bob Mottram <bob@freedombone.net>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# The type of hardware random number generator being used
# This can be empty, "beaglebone" or "onerng"
HWRNG_TYPE=

# Download location for OneRNG driver
ONERNG_PACKAGE="onerng_3.4-1_all.deb"
ONERNG_PACKAGE_DOWNLOAD="https://github.com/OneRNG/onerng.github.io/blob/master/sw/$ONERNG_PACKAGE?raw=true"
# Hash for OneRNG driver
ONERNG_PACKAGE_HASH='78f1c2f52ae573e3b398a695ece7ab9f41868252657ea269f0d5cf0bd4f2eb59'

# device name for OneRNG
ONERNG_DEVICE='ttyACM0'

function check_hwrng {
    if [[ $HWRNG_TYPE == "beaglebone" ]]; then
        # If hardware random number generation was enabled then make sure that the device exists.
        # if /dev/hwrng is not found then any subsequent cryptographic key generation would
        # suffer from low entropy and might be insecure
        if [ ! -e /dev/hwrng ]; then
            ls /dev/hw*
            echo $'The hardware random number generator is enabled but could not be detected on'
            echo $'/dev/hwrng.  There may be a problem with the installation or the Beaglebone hardware.'
            exit 75
        fi
    fi

    # If a OneRNG device was installed then verify its firmware
    #check_onerng_verification
}

function check_onerng_verification {
    if [[ $(is_completed "${FUNCNAME[0]}") == "1" ]]; then
        return
    fi
    if [[ $HWRNG_TYPE != "onerng" ]]; then
        return
    fi
    echo $'Checking OneRNG firmware verification'
    last_onerng_validation=$(grep "OneRNG: firmware verification" /var/log/syslog.1 | awk '/./{line=$0} END{print line}')
    if [[ $last_onerng_validation != *"passed OK"* ]]; then
        last_onerng_validation=$(grep "OneRNG: firmware verification" /var/log/syslog | awk '/./{line=$0} END{print line}')
        if [[ $last_onerng_validation != *"passed OK"* ]]; then
            echo "$last_onerng_validation"
            echo $'OneRNG firmware verification failed'
            exit 735026
        fi
    fi
    echo $'OneRNG firmware verification passed'
    # if haveged was previously installed then remove it
    apt-get -yq remove haveged
    mark_completed "${FUNCNAME[0]}"
}

function install_onerng {
    apt-get -yq install rng-tools at python-gnupg

    # Move to the installation directory
    if [ ! -d "$INSTALL_DIR" ]; then
        mkdir "$INSTALL_DIR"
    fi
    cd "$INSTALL_DIR" || exit 24762464

    # Download the package
    if [ ! -f $ONERNG_PACKAGE ]; then
        wget "$ONERNG_PACKAGE_DOWNLOAD"
        # shellcheck disable=SC2086
        mv $ONERNG_PACKAGE?raw=true $ONERNG_PACKAGE
    fi
    if [ ! -f $ONERNG_PACKAGE ]; then
        echo $"OneRNG package could not be downloaded"
        exit 59249
    fi

    # Check the hash
    hash=$(sha256sum $ONERNG_PACKAGE | awk -F ' ' '{print $1}')
    if [[ "$hash" != "$ONERNG_PACKAGE_HASH" ]]; then
        echo $"OneRNG package: $ONERNG_PACKAGE"
        echo $"Hash does not match. This could indicate that the package has been tampered with."
        echo $"OneRNG expected package hash: $ONERNG_PACKAGE_HASH"
        echo $"OneRNG actual hash: $hash"
        exit 25934
    fi

    # install the package
    dpkg -i $ONERNG_PACKAGE

    # Check that the install worked
    if [ ! -f /etc/onerng.conf ]; then
        echo $'OneRNG configuration file not found. The package may not have installed successfully.'
        exit 42904
    fi

    dialog --title $"OneRNG Device" \
           --msgbox $"Please plug in the OneRNG device" 6 40

    # check rng-tools configuration
    if ! grep -q "/dev/$ONERNG_DEVICE" /etc/default/rng-tools; then
        echo "HRNGDEVICE=/dev/$ONERNG_DEVICE" >> /etc/default/rng-tools
    fi

    systemctl restart rng-tools
}

function random_number_generator {
    if [[ $(is_completed "${FUNCNAME[0]}") == "1" ]]; then
        return
    fi
    if [[ $INSTALLED_WITHIN_DOCKER == "yes" ]]; then
        # it is assumed that docker uses the random number
        # generator of the host system
        return
    fi

    # if the hrng type has not been set but /dev/hwrng is detected
    if [[ $HWRNG_TYPE != "beaglebone" ]]; then
        if [ -e /dev/hwrng ]; then
            HWRNG_TYPE="beaglebone"
        fi
    fi

    case $HWRNG_TYPE in
        beaglebone)
            apt-get -yq install rng-tools
            sed -i 's|#HRNGDEVICE=/dev/hwrng|HRNGDEVICE=/dev/hwrng|g' /etc/default/rng-tools
            ;;
        onerng)
            function_check install_onerng
            install_onerng
            ;;
        *)
            # With some VMs, the hardware cycles counter is emulated and deterministic,
            # and thus predictible, so havege should not be used
            if [[ "$ARCHITECTURE" != "qemu"* ]]; then
                apt-get -yq install haveged
            fi
            ;;
    esac

    mark_completed "${FUNCNAME[0]}"
}

# NOTE: deliberately no exit 0