path: root/makepass.zsh

#!/usr/bin/env zsh
# Filename:      makepass.zsh
# Purpose:       Creating random passwords.
# Authors:       Dennis Eriksen <d@ennis.no>
# Bug-Reports:   Email <git@dnns.no>
# License:       This file is licensed under the BSD 3-Clause license.
################################################################################
# This file generates random passwords
################################################################################
# Copyright (c) 2018-2023 Dennis Eriksen • d@ennis.no

#
# Globals
#

# typeset
# -a = array
# -i = integer
# -g = global
# -r = readonly

typeset -gri MAX=255         # max length of passwords
typeset -gri RANGE_MAX=42    # max length when using random length
typeset -gri RANGE_MIN=8     # min length when using random length
typeset -gri PASS_WORDS=8    # number of words in passphrases

typeset -gr  LOWER='abcdefghijklmnopqrstuvwxyz'
typeset -gr  UPPER='ABCDEFGHIJKLMNOPQRSTUVWXYZ'
typeset -gr  DIGIT='0123456789'
typeset -gr  OTHER='!#$%&/()=?+-_,.;:<>[]{}|@*'
typeset -gr  ALPHA=${LOWER}${UPPER}
typeset -gr  ALNUM=${ALPHA}${DIGIT}
typeset -gr  EVERY=${ALNUM}${OTHER}

typeset -gi  LENGTH=${MAKEPASS_LENGTH:-0}     # length of passwords. 0 means "random number between RANGE_MIN and RANGE_MAX"
typeset -gi  NUMBER=${MAKEPASS_NUMBER:-10}    # number of passwords
typeset -gi  PRINTLEN=${MAKEPASS_PRINTLEN:-0} # print length of passwords
typeset -g   NORMAL=${MAKEPASS_NORMAL:-$ALNUM'-_'}
typeset -g   SPECIAL=${MAKEPASS_SPECIAL:-$EVERY}
typeset -g   WORDLIST=${MAKEPASS_WORDLIST:-/usr/share/dict/words}

typeset -ga  WORDS      # Array of words from WORDLIST
typeset -gi  COL_WIDTH  # Width of columns we will be printing
typeset -gi  COL_NUM    # Number of columns to print

# GOTCHAs:
#
# $RANDOM - from the zsh documentation:
# > The values of RANDOM form an intentionally-repeatable pseudo-random sequence;
# > subshells that reference RANDOM will result in identical pseudo-random values
# > unless the value of RANDOM is referenced or seeded in the parent shell in
# > between subshell invocations.
# So remember to throw away a $RANDOM between subshell invocations!

#
# Functions
#

# main-function. This is where the magic happens
function main() {
  setopt localoptions

  # Getopts
  while getopts 'hl:n:p' opt; do
    case $opt in
      h)
        help && return 0;;
      l)
        [[ $OPTARG = <0-> && $OPTARG -le $MAX ]] || die "-l takes a number between 0 and $MAX"
        LENGTH=$OPTARG;;
      n)
        [[ $OPTARG = <1-> && $OPTARG -le $MAX ]] || die "-n takes a number between 1 and $MAX"
        NUMBER=$OPTARG;;
      p)
        PRINTLEN=1;;
      *)
        die "Unknown argument";;
    esac
  done
  shift $((OPTIND - 1))


  #
  # Some error-checking
  #

  # We only take one argument in addition to the optargs
  (( ARGC > 1 )) && die "only one argument"

  # if there is an argument, set it to $LENGTH
  [[ -n $1 ]] && LENGTH=$1

  # Check $LENGTH and $NUMBER
  # Both are integers so no need to check if they are numbers
  # If they were somehow assigned to, say "xx", they would be 0
  (( 0 <= LENGTH && LENGTH <= MAX )) || die "length must be a number between 0 and $MAX"
  (( 1 <= NUMBER && NUMBER <= MAX )) || die "number-argument must be between 1 and $MAX"


  #
  # Some other work
  #

  # Seed $RANDOM with a random 32bit integer from /dev/random
  local r4 # will be filled with 4 random bytes from /dev/random
  IFS= read -rk4 -u0 r4 < /dev/random || return
  local b1=$r4[1] b2=$r4[2] b3=$r4[3] b4=$r4[4]
  RANDOM=$(( #b1 << 24 | #b2 << 16 | #b3 << 8 | #b4 ))

  # We zero-pad printlength, so we need two extra chars if LENGTH < 100 (three
  # if LENGTH >= 100).
  (( PRINTLEN )) && { ((LENGTH < 100)) && PRINTLEN=2 || PRINTLEN=3 }

  # Calculate width of columns and number of columns to use
  # add two for spacing between columns
  COL_WIDTH=$(( ( LENGTH ? LENGTH : RANGE_MAX ) + 2 ))
  # $COLUMNS is a builtin variable for width of terminal
  # If $PRINTLEN is set, we have to add one for the space as well
  COL_NUM=$(( COLUMNS / ( COL_WIDTH + ( PRINTLEN ? PRINTLEN + 1 : 0 )) ))
  # Just in case COL_NUM=0 because of a small terminal or something
  (( COL_NUM )) || COL_NUM=1


  #
  # Print!
  #

  print_columns "Normal passwords" $NUMBER $NORMAL

  print; : $RANDOM # Throw away

  print_columns "Passwords with special characters" $((NUMBER/3*2+1)) $SPECIAL

  # Passphrases - but only if a wordlist is available
  if [[ -r $WORDLIST ]] && ((NUMBER / 2 > 0)); then
    print; : $RANDOM # Throw away
    print "Passphrases:"
    # Read wordlist into array
    WORDS=(${(f)"$(<$WORDLIST)"})
    # Run passphrase-function to output passphrases
    repeat $((NUMBER / 2)) passphrase
  fi
}

# Function to print passwords in neat columns
function print_columns() {
  : $RANDOM # Throw away
  local title=$1
  local num=$2
  local chars=$3
  local -i i=0

  local strings=($(repeat $num { randstring $chars }))

  print -- "${title}:"

  for s in $strings; do
    let i++
    (( PRINTLEN )) && printf "%0${PRINTLEN}i " $#s
    printf "%-${COL_WIDTH}s" $s
    ((i % COL_NUM == 0 || (i == num && i % COL_NUM > 0))) && print
  done
}

# Function to create random strings
function randstring() {
  local chars=${1:-$NORMAL}
  local string
  local -i len=$(( LENGTH \
                   ? LENGTH \
                   : RANDOM % (RANGE_MAX - RANGE_MIN + 1) + RANGE_MIN ))

  string+=$ALPHA[$((RANDOM % $#ALPHA + 1))]
  repeat $((len - 2)) string+=$chars[$((RANDOM % $#chars + 1))]
  (( len >= 2 )) && string+=$ALNUM[$((RANDOM % $#ALNUM + 1))]

  print -- $string; return
}

# Create random passphrase
function passphrase() {
  setopt localoptions rematch_pcre

  local prestring string

  # Put together $len random words, separated by '-'
  repeat $PASS_WORDS prestring+=$WORDS[$((RANDOM % $#WORDS + 1))]'-'
  prestring=$prestring[1,-2]  # remove trailing dash

  # This while-loop removes any characters NOT in '[^0-9a-zA-Z_-]'
  while [[ -n $prestring ]]; do
    if [[ $prestring =~ '[^0-9a-zA-Z_-]' ]]; then
      string+=${prestring[1,MBEGIN-1]}
      prestring=${prestring[MEND+1,-1]}
    else
      break
    fi
  done
  string+=$prestring # append the rest of $prestring

  printf '%s\n' $string; return
}

# Function to die
function die() {
  print -u2 -- "$@"
  print -u2 -- "Maybe try running \`$ZSH_SCRIPT -h\` for help"
  exit 1
}

# Help-function
function help() {
  print -- $'NAME
    makepass - create several random passwords

SYNOPSIS
    makepass [OPTIONS] [NUM]

    If a NUM is provided, passwords will be NUM characters long.

    By default `makepass` will output passwords from the three following classes:

    - Normal passwords - random strings with letters (both lower and upper
      case), numbers, and dashes and underscores.

    - Passwords with special characters - random strings generated from lower
      and upper case letters, numbers, and the following characters:
      !#$%&/()=?+-_,.;:<>[]{}|@*

    - Passphrases - if we find a dictionary, a series of eight random words
      from the dictionary, separated by dashes. The number of words can not be
      changed, but you do not have to use all of them. Use as mane as you want.

    The first character will always be alphabetic, and the last will always be
    alphanumeric.

DESCRIPTION
    makepass has the following options:

    -h
        output this help-text
    -l
        length of passwords. See MAKEPASS_LENGTH below
    -n
        number of passwords. See MAKEPASS_NUMBER below
    -p
        print length of number

ENVIRONMENT
    makepass examines the following environmental variables.

    MAKEPASS_LENGTH
        Specifies the length of passwords. Valid values are 0-255. If 0, a
        random value between 8 and 42 will be used for each password. -l
        overrides this environmental variable, and the argument NUM overrides
        that again. So `MAKEPASS_LENGTH=10 makepass -l 12 14` will give
        passwords that are 14 characters long, even though both -l and
        MAKEPASS_LENGTH also specifies a length.

    MAKEPASS_NUMBER
        The number of passwords to generate. This formula is used to determine
        how many passwords from each group should be generated:
        - (n) normal passwords
        - (n / 3 * 2 + 1) special passwords
        - (n / 2) passphrases
        Where n is 10 by default. Valid values for n are 1-255. Floating-poing
        math is not used, so results may vary.

    MAKEPASS_PRINTLEN
        If 1, print length of all passwords. If 0, don\'t.

    MAKEPASS_NORMAL
        String of characters from which to generate "normal" passwords.
        Defaults to:
        abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_

    MAKEPASS_SPECIAL
        String of characters from which to generate passwords with special
        characters. Defaults to the same characters as in MAKEPASS_NORMAL, plus
        these:
        !#$%&/()=?+-_,.;:<>[]{}|@*

    MAKEPASS_WORDLIST
        Specifies the dictionary we find words for passphrases in. If this is
        unset or empty, we try "/usr/share/dict/words". If that file does not
        exist, no passphrases will be provided.

NOTES
    This scripts makes use of $RANDOM - a builtin in zsh which produces a
    pseudo-random integer between 0 and 32767, newly generated each time the
    parameter is referenced. We initially seed the random number generator with
    a random 32bit integer generated from /dev/random. This should provide
    enough randomnes to generate sufficiently secure passwords.

AUTHOR
    Dennis Eriksen <https://dnns.no>'

  return 0
}

# Run main function! GOGOGO!
main "${@:-}"

# Last time I redid this script I benchmarked some ways to generate random
# strings. Here's the results:

# subshell with tr | fold | head
# % time (repeat 10000 { string=''; string=$(tr -cd '[:alpha:]' </dev/random | fold -w 20 | head -n1 ) } )
# 45.32s user 22.38s system 201% cpu 33.598 total
#
# subshell with head | tr | tail
# % time (repeat 10000 { string=''; string=$(head -n100 /dev/random | tr -cd '[:alpha:]' | tail -c20 ) } )
# 40.88s user 17.87s system 187% cpu 31.249 total
#
# subshell sysread | tr in brace-expansion instead of head/tail
# % time (repeat 10000 { string=''; string=${${:-"$(sysread -i 1 </dev/random | tr -cd '[:alpha:]')"}[1,20]} } )
# 24.13s user 11.38s system 120% cpu 29.442 total
#
# string-addition with randint32()-function to get random 32bit integer from /dev/random
# % time (repeat 10000 { string='';repeat 20 string+=$ALPHA[$((randint32() % $#ALPHA + 1))] })
# 8.17s user 3.28s system 99% cpu 11.475 total
#
# string-addition and $RANDOM
# % time (repeat 10000 { string='';repeat 20 string+=$ALPHA[$((RANDOM % $#ALPHA + 1))] } )
# 0.74s user 0.00s system 99% cpu 0.741 total

## END OF FILE #################################################################