Allows 2 independent persons to create a shared otp time based code

interpersonalAuthenticator.sh

#! /bin/bash

set -e
# set -v

# Accepts a first party and a second party and produces a shared
# One Time Password Time based code, usually referred to as 2FA

# Dependencies
# sudo apt-get install qrencode oathtool

# This function centers the text in the terminal
function center_echo {
    message="$*"
    columns=$(tput cols)
    spaces=$(((columns-${#message})/2))
    head -c ${spaces} < /dev/zero | tr '\0' ' '
    echo "${message}"
}

if [ $# -ne 2 ]
then
    >&2 echo "Incorrect Usage!"
    >&2 echo "${0} (first party) (second party)"
    exit 1
fi

party_one=${1}
party_two=${2}

size=32  # length of the shared secret
step=60  # lifespan of a single code in seconds
digits=6 # length of the codes (only 6, 7 and 8 are supported)
# Android currently only supports 6 digits
issuer=$(echo "Interpersonal Authenticator"| sed 's/ /%20/g')

center_echo Interpersonal Authenticator
center_echo "${party_one} <=> ${party_two}"

center_echo This program has been tested with the following authenticators
center_echo Please make sure you have one of these installed
center_echo Press Enter To Continue

echo "Android - Google Authenticator"
qrencode --level=H --margin=1 --type=ANSI256 https://bit.ly/19dDzPR
# https://play.google.com/store/apps/details?id=com.google.android.apps.authenticator2
center_echo Press Enter To Continue
read

echo "iOS - Google Authenticator"
qrencode --level=H --margin=1 --type=ANSI256 http://apple.co/1NoT8TE
# https://itunes.apple.com/us/app/id388497605
center_echo Press Enter To Continue
read

center_echo Generating random key with ${size} bytes

# Alternative method to generate random data
# Much faster (Good for testing)
# b32_secret_no_pad=$(openssl rand "${size}" | base32 --wrap=0 | tr -d '=')

center_echo If the program stalls you need to generate more entropy on your computer
# The URI really doesn't seem to like the "=" padding
b32_secret_no_pad=$(head -c ${size} /dev/random | base32 --wrap=0 | tr -d '=')
# If you do not have `base32` installed, you can download and compile https://github.com/RedRoosterKey/hex2b32
# b32_secret_no_pad=$(xxd -cols "${size}" --len "${size}" -ps /dev/random | hex2b32 --no-padding)

function qr_code {
    from=${1}
    to=${2}
    # Generate QR Codes in proper format
    # https://github.com/google/google-authenticator/wiki/Key-Uri-Format
    label=$(echo "Shared Code With ${to}" | sed 's/ /%20/g')
    uri="otpauth://totp/${label}?secret=${b32_secret_no_pad}&issuer=${issuer}&digits=${digits}&period=${step}"
    center_echo "${uri}"
    qrencode --level=L --margin=1 --type=ANSI256 "${uri}"
    center_echo "${from}: Please scan and press enter."
    read
}
qr_code "${party_one}" "${party_two}"
qr_code "${party_two}" "${party_one}"

# Generate Some codes
oathtool             --totp --base32 --time-step="${step}"s --digits="${digits}" --window=5 "${b32_secret_no_pad}" --verbose | while read line; do center_echo "${line}"; done
center_echo oathtool --totp --base32 --time-step="${step}"s --digits="${digits}"            "${b32_secret_no_pad}"