#!/bin/bash
#
# .---.                  .              .
# |                      |              |
# |--- .--. .-.  .-.  .-.|  .-. .--.--. |.-.  .-. .--.  .-.
# |    |   (.-' (.-' (   | (   )|  |  | |   )(   )|  | (.-'
# '    '     --'  --'  -' -  -' '  '   -' -'   -' '   -  --'
#
#                    Freedom in the Cloud
#
# It's useful to be able to store user passwords, but not a good
# idea to do that in plain text. This implements a simple password
# store. It gpg symmetric encrypts passwords using the backups
# private key as the passphrase.
#
# In order for an adversary to obtain the passwords they must have
# the backups GPG key, which is not obtainable from local or remote
# backups and can only happen if they get root access to the system
# (in which case it's game over anyhow) or if they can decrypt
# a master keydrive or obtain sufficient keydrive fragments.
#
# License
# =======
#
# Copyright (C) 2016 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/>.

PROJECT_NAME='freedombone'

export TEXTDOMAIN=${PROJECT_NAME}-pass
export TEXTDOMAINDIR="/usr/share/locale"

MY_BACKUP_KEY_ID=
CURR_USERNAME=
REMOVE_USERNAME=
CURR_APP=
REMOVE_APP=
CURR_PASSWORD=""
TESTS=

function get_backup_key_id {
    MY_BACKUP_KEY_ID=$(gpg --list-keys "(backup key)" | \
                           grep 'pub ' | awk -F ' ' '{print $2}' | \
                           awk -F '/' '{print $2}')
    if [ ${#MY_BACKUP_KEY_ID} -lt 4 ]; then
        echo $"Error: gpg backup key was not found"
        return 58213
    fi
}

function pass_show_help {
    echo ''
    echo $"${PROJECT_NAME}-pass"
    echo ''
    echo $'Password store using gpg'
    echo ''
    echo $'  -h --help                        Show help'
    echo $'  -u --user [name]                 Username'
    echo $'  -a --app [name]                  Name of the application'
    echo $'  -p --pass [password]             The password to store'
    echo ''
    echo $'To encrypt a password:'
    echo ''
    echo $"  ${PROJECT_NAME}-pass -u [username] -a [app] -p [password]"
    echo ''
    echo $'To retrieve a password:'
    echo $''
    echo $"  ${PROJECT_NAME}-pass -u [username] -a [app]"
    echo ''
    echo $'To remove passwords for a user:'
    echo $''
    echo $"  ${PROJECT_NAME}-pass -r [username]"
    echo ''
    echo $'To remove an application password for a user:'
    echo $''
    echo $"  ${PROJECT_NAME}-pass --u [username] --rmapp [name]"
    echo ''
    exit 0
}

function pad_string {
    pass_string="$1"
    str_length=${#pass_string}
    total_padding=$((128 - str_length))
    leading_padding=$((1 + RANDOM % $total_padding))
    trailing_padding=$((total_padding - leading_padding))
    leading=$(printf "%-${leading_padding}s")
    trailing=$(printf "%-${trailing_padding}s")
    echo "${leading}${pass_string}${trailing}"
}

function remove_padding {
    padded_string="$1"
    echo -e "${padded_string}" | tr -d '[:space:]'
}

function run_tests {
    pass="SuperSecretPassword"
    padded=$(pad_string "$pass")
    echo "|${padded}|"
    ${PROJECT_NAME}-pass -u root -a tests -p "$pass"
    returned_pass=$(${PROJECT_NAME}-pass -u root -a tests)
    if [[ "$pass" != "$returned_pass" ]]; then
        echo "pass     :${pass}:"
        echo "padded   :${padded}:"
        echo "returned :${pass}:"
        exit 73825
    fi
    ${PROJECT_NAME}-pass -u root --rmapp tests
    echo "Tests passed"
}

while [[ $# > 1 ]]
do
    key="$1"

    case $key in
        -h|--help)
            pass_show_help
            ;;
        -t|--test)
            shift
            TESTS=1
            ;;
        -u|--user|--username)
            shift
            CURR_USERNAME="${1}"
            ;;
        -r|--rm|--remove)
            shift
            REMOVE_USERNAME="${1}"
            ;;
        --rmapp|--removeapp)
            shift
            REMOVE_APP="${1}"
            ;;
        -a|--app|--application)
            shift
            CURR_APP="${1}"
            ;;
        -p|--pass|--password|--passphrase)
            shift
            CURR_PASSWORD="${1}"
            ;;
        *)
            # unknown option
            ;;
    esac
    shift
done

if [ ${REMOVE_USERNAME} ]; then
    if [ -d ~/.passwords/${REMOVE_USERNAME} ]; then
        rm -rf ~/.passwords/${REMOVE_USERNAME}
    fi
    exit 0
fi

get_backup_key_id

# Use the backups private key as a symmetric passphrase
MASTER_PASSWORD=$(gpg -q --armor --export-secret-key $MY_BACKUP_KEY_ID | sed '/---/d' | sed '/Version/d' | sed '/^$/d')

if [ $TESTS ]; then
    run_tests
    exit 0
fi

if [ ! $CURR_USERNAME ]; then
    echo $'Error: No username given'
    exit 1
fi

if [ ! -d /home/$CURR_USERNAME ]; then
    if [[ "$CURR_USERNAME" != "root" ]]; then
        echo $"Error: User $CURR_USERNAME does not exist"
        exit 2
    fi
fi

if [ ${REMOVE_APP} ]; then
    if [ -d ~/.passwords/${CURR_USERNAME}/${REMOVE_APP} ]; then
        shred -zu ~/.passwords/${CURR_USERNAME}/${REMOVE_APP}
    fi
    exit 0
fi

if [ ! $CURR_APP ]; then
    echo $'Error: No app name given'
    exit 3
fi

if [ ${#CURR_PASSWORD} -eq 0 ]; then
    # retrieve password
    if [ ! -f ~/.passwords/$CURR_USERNAME/$CURR_APP ]; then
        echo ""
        exit 4
    else
        pass=$(gpg -dq --passphrase "$MASTER_PASSWORD" ~/.passwords/$CURR_USERNAME/$CURR_APP)
        remove_padding "${pass}"
    fi
else
    # store password
    if [ ! -d ~/.passwords/$CURR_USERNAME ]; then
        mkdir -p ~/.passwords/$CURR_USERNAME
    fi
    # padding helps to ensure than nothing can be learned from the length of the cyphertext
    pad_string "${CURR_PASSWORD}" | gpg -ca --cipher-algo AES256 --passphrase "$MASTER_PASSWORD" > ~/.passwords/$CURR_USERNAME/$CURR_APP
    if [ ! -f ~/.passwords/$CURR_USERNAME/$CURR_APP ]; then
        exit 5
    fi
fi

exit 0