#!/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) 2016-2018 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/>.

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=
EXPORT_FILENAME=

MASTER_PASSWORD=''

# If this file is present then don't store passwords
NO_PASSWORD_STORE_FILE=~/.nostore

function get_backup_key_id {
    MY_BACKUP_KEY_ID=$(gpg --list-keys "(backup key)" | sed -n '2p' | sed 's/^[ \t]*//')
    if [ ${#MY_BACKUP_KEY_ID} -lt 4 ]; then
        echo $"Error: gpg backup key was not found"
        exit 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 $'     --export [filename]           Export to KeepassX XML'
    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")
    if [ ${#padded} -ne 128 ]; then
        echo $'Incorrect padded length'
        exit 78352
    fi
    if ! "${PROJECT_NAME}-pass" -u root -a tests -p "$pass"; then
        echo $'Unable to encrypt password'
        exit 72725
    fi
    echo $'Password encrypted'
    returned_pass=$(${PROJECT_NAME}-pass -u root -a tests)
    if [[ "$pass" != "$returned_pass" ]]; then
        echo "pass     :${pass}:"
        echo "padded   :${padded}:"
        echo "returned :${returned_pass}:"
        exit 73825
    fi
    echo $'Password decrypted'
    ${PROJECT_NAME}-pass -u root --rmapp tests
    echo "Tests passed"
}

function clear_passwords {
    # remove all passwords except for the root one, which is needed
    # for automatic database backups
    for d in /root/.passwords/*/ ; do
        USERNAME=$(echo "$d" | awk -F '/' '{print $4}')
        if [[ "$USERNAME" != 'root' ]]; then
            rm -rf "/root/.passwords/$USERNAME"
        fi
    done
    if [ ! -f $NO_PASSWORD_STORE_FILE ]; then
        touch $NO_PASSWORD_STORE_FILE
    fi
    echo $'Passwords cleared. Future passwords will not be stored.'
    exit 0
}

function export_to_keepass {
    filename="$1"

    { echo '<database>';
      echo '  <group>';
      echo "    <title>${PROJECT_NAME}</title>";
      echo '    <icon>48</icon>'; } > "$filename"

    for d in /root/.passwords/*/ ; do
        USERNAME=$(echo "$d" | awk -F '/' '{print $4}')
        { echo '    <group>';
          echo "      <title>$USERNAME</title>";
          echo '      <icon>0</icon>'; } >> "$filename"
        for a in /root/.passwords/$USERNAME/* ; do
            APP_NAME=$(basename "$a")
            app_password=$("${PROJECT_NAME}-pass" -u "$USERNAME" -a "$APP_NAME")
            { echo '      <entry>';
              echo "        <title>$APP_NAME</title>";
              echo "        <username>$USERNAME</username>";
              echo "        <password>$app_password</password>";
              echo '        <url/>';
              echo '        <comment/>';
              echo '        <icon>0</icon>';
              echo '        <expire>Never</expire>';
              echo '      </entry>'; } >> "$filename"
        done
        echo '    </group>' >> "$filename"
    done

    echo '  </group>' >> "$filename"
    echo '</database>' >> "$filename"

    echo $"Exported $filename"
}

while [ $# -gt 1 ]
do
    key="$1"

    case $key in
        -h|--help)
            pass_show_help
            ;;
        -t|--test)
            shift
            TESTS=1
            ;;
        -c|--clear|--erase)
            clear_passwords
            ;;
        -e|--enable)
            shift
            if [ -f $NO_PASSWORD_STORE_FILE ]; then
                rm $NO_PASSWORD_STORE_FILE
                echo $'Password storage has been enabled'
            fi
            ;;
        -u|--user|--username)
            shift
            CURR_USERNAME="${1}"
            ;;
        -r|--rm|--remove)
            shift
            REMOVE_USERNAME="${1}"
            ;;
        --rmapp|--removeapp)
            shift
            REMOVE_APP="${1}"
            ;;
        -a|--app|--application)
            shift
            CURR_APP="${1}"
            ;;
        --export)
            shift
            EXPORT_FILENAME="${1}"
            ;;
        --master)
            shift
            MASTER_PASSWORD="${1}"
            ;;
        -p|--pass|--password|--passphrase)
            shift
            CURR_PASSWORD="${1}"
            ;;
        *)
            # unknown option
            ;;
    esac
    shift
done

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

get_backup_key_id

if [ ${#MASTER_PASSWORD} -eq 0 ]; then
    if [ ! -d /root/.passwords/root ]; then
        mkdir -p /root/.passwords/root
    fi
    if [ ! -f /root/.passwords/root/master ]; then
        newpass=$(openssl rand -base64 64 | tr -dc A-Za-z0-9 | head -c 30)
        echo "$newpass" > /root/.passwords/root/master
        chmod 700 /root/.passwords/root/master
    fi
    MASTER_PASSWORD=$(cat /root/.passwords/root/master)
fi

if [ $TESTS ]; then
    run_tests
    exit 0
fi

if [ "$EXPORT_FILENAME" ]; then
    export_to_keepass "$EXPORT_FILENAME"
    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 [ "${REMOVE_APP}" ]; then
    if [ -d "${HOME}/.passwords/${CURR_USERNAME}/${REMOVE_APP}" ]; then
        rm "${HOME}/.passwords/${CURR_USERNAME}/${REMOVE_APP}"
    fi
    exit 0
fi

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

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

MASTER_PASSWORD=
exit 0