#!/bin/bash
#
#  passphrase_simple [4words|hex|uuid|base64|cleaned]
#
# Very simple passphrase generator using various methods
#
# For a better more complex one look at "passphrase_generator"
#
# NOTE: This may not generate passphrases that satisfy the 'old rules' of
# having lowercase, uppercase, digits, punctuation.  Though it does more than
# satisfy the typical minimum length requirements of such systems.
#
####
# Anthony Thyssen    29 Oct 2019
#

# Generate a random password
generate_password() {
  case "$1" in
  4words)
    # four random words, XKCD style, with separator symbol
    #
    # Word source
    dictionary="$HOME/lib/dict/dict_diceware_eff"
    [ -f "$dictionary" ] || dictionary=/usr/share/dict/words
    # Seperation symbol
    sep=$( shuf -en1 -- - _ + = \# \* : \| \~ ^ . , / \\\\ @ ! \? % \$ \& )
    # Create passphrase
    grep -E '^[[:alpha:]]{3,9}$' "$dictionary" |
       shuf -n4 | paste -d"$sep" -s
    ;;
  hex)
    # Deterministic password generation - always same for a specifc user
    # alternatives: shasum, sha224sum
    md5sum <<<"$user" | cut -f1 -d' '
    ;;
  uuid)
    # 32 hexadecimal with 4 hyphens
    uuidgen
    ;;
  base64)
    # 24 random base64 characters
    openssl rand -base64 18 | cut -c1-24
    ;;
  cleaned)
    # Substitute characters which could be misinterperted
    # EG: some character groups all look simular, EG: 0OQ
    # and some puncuation (like dot) may not print clearly
    openssl rand -base64 18 | cut -c1-24 |
       tr '0OQ1lI|!8B./+^#;' 'XYZabc67rst234uv'
    ;;
  *)
    echo >&2 "Usage: ${BASH_SOURCE##*/} [4words|hex|uuid|base64|cleaned]"
    exit 1
    ;;
  esac
}

generate_password "${1:-4words}"