signal-auth-setup

#!/usr/bin/env bash
#
# (C) James Murphy 2016, licensed under GPLv2
#
# Script to setup system for signal authentication

if ! command -v signal-cli >/dev/null 2>&1; then
    echo >&2 "signal-cli not found, aborting."
    exit 1
fi

SIGNAL_CLI="$(which signal-cli)"
SIGNAL_HOME="/var/lib/signal-authenticator"

IFS="
"
function sanitize_phone_number {
    echo "$1" | tr -cd "0123456789+"
}

function looks_like_phone_number {
    if [[ "$1" =~ ^\+[0-9]+$ ]]; then
        return 0
    else
        return 1
    fi
}

if [[ "$1" == "-h" ]] || [[ "$1" == "--help" ]]; then
    printf \
"Usage: signal-auth-setup [-h|--help] [as-linked] [override]
Setup signal authentication on your system.
Options:
[no argument]\tSetup the signal-authenticator user's home by registering a
\t\tsignal number
as-linked\tSetup the signal-authenticator user's home by linking as a
\t\tsubordinate device of an existing signal authenticator.
override\tDon't abort if config alerady exists.
-h --help\tShow this help message.\n" && exit 0
fi

if [[ "$(id -u)" -ne 0 ]]; then
    echo >&2 "Must be root to setup for the system user, aborting."
    exit 1
fi

if [[ -f "$SIGNAL_HOME/.signal_authenticator" ]] || [[ -d "$SIGNAL_HOME/.signal" ]]; then
    if [[ "$1" != "override" ]] && [[ "$2" != "override" ]]; then
        echo >&2 "It looks like signal-authenticator's home is already setup, aborting."
        echo >&2 "Use the override argument to bypass."
        echo >&2 "Bypassing will completely remove all previous"\
            "configuration, including stored keys and fingerprints."
        exit 2
    else
        echo >&2 "It looks like signal-authenticator's home is already setup, continuing anyway."
    fi
fi

read -p "Input signal username to send tokens from (e.g. +15553331234): " USERNAME
USERNAME=$(sanitize_phone_number $USERNAME)
echo "Sanitized number: $USERNAME"
if ! looks_like_phone_number $USERNAME; then
    echo >&2 "Bad phone number: $USERNAME, aborting"
    exit 4
fi
echo "Creating $SIGNAL_HOME/.signal_authenticator"
echo "username=$USERNAME" > "$SIGNAL_HOME/.signal_authenticator"
chmod o-rwx "$SIGNAL_HOME/.signal_authenticator"
chown signal-authenticator:signal-authenticator "$SIGNAL_HOME/.signal_authenticator"

echo "Removing old config, if it exists"
rm -rf "$SIGNAL_HOME/.config/signal" >/dev/null 2>&1

echo "Registering signal username"
if [[ "$1" == "as-linked" ]] || [[ "$2" == "as-linked" ]]; then
    echo "Registering as subordinate (linked) device."
    echo "To complete linking, you must run signal-auth-link from the primary device."
    echo "It will ask for the following tsdevice:/ link."
    sudo -u signal-authenticator "$SIGNAL_CLI" -u "$USERNAME" link
    if [[ "$?" != "0" ]]; then
        echo >&2 "Failed to link, aborting."
        exit 3
    fi
else
    sudo -u signal-authenticator "$SIGNAL_CLI" -u "$USERNAME" register
    read -p "Verify code (sent SMS to $USERNAME): " CODE
    sudo -u signal-authenticator "$SIGNAL_CLI" -u "$USERNAME" verify "$CODE"
    if [[ "$?" != "0" ]]; then
        echo >&2 "Failed to verify $USERNAME, aborting."
        exit 3
    fi
fi
chmod -R o-rwx "$SIGNAL_HOME/.config/signal"
chown -R signal-authenticator:signal-authenticator "$SIGNAL_HOME/.config/signal"
echo "Your signal authentication is now setup."