unitproc/bknpass

   1 #!/bin/bash
   2 # Desc: Generate passphrase with specified number of bits of entropy
   3 # Usage: bknpass [integer]
   4 # Example: bknpass 256
   5 #   Result: 9tnzcl0m4dsm22a95525zj93jj
   6 # Version: 0.2.1
   7 # Depends: bash 5.1.8, GNU coreutils 8.32, bc 1.07.1, awk 5.1.0
   8 # License:
   9 #    `bknpass`, an alphanumeric password generator
  10 #    Copyright (C) 2022  Steven Baltakatei Sandoval (baltakatei.com)
  11 #
  12 #    This program is free software: you can redistribute it and/or modify
  13 #    it under the terms of the GNU General Public License as published by
  14 #    the Free Software Foundation, either version 3 of the License, or
  15 #    any later version.
  16 #
  17 #    This program is distributed in the hope that it will be useful,
  18 #    but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 #    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 #    GNU General Public License for more details.
  21 #
  22 #    A copy of the GNU General Public License may be found at
  23 #    <https://www.gnu.org/licenses/>.
  24
  25 yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
  26 die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
  27 try() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
  28 showUsage() {
  29     # Desc: Display script usage information
  30     # Usage: showUsage
  31     # Version 0.0.1
  32     # Input: none
  33     # Output: stdout
  34     # Depends: GNU-coreutils 8.30 (cat)
  35     cat <<'EOF'
  36     USAGE:
  37         bknpass [int entropy_bit_count]
  38
  39     EXAMPLE:
  40         bknpass 128
  41 EOF
  42 }; # Display information on how to use this script.
  43 main() {
  44     # Desc: main program
  45     # Usage: main "$@"
  46     # Input:      $1: integer bits of entropy
  47     # Output: stdout: string passphrase
  48     # Depends: bash 5.1.8, GNU coreutils 8.32, bc 1.07.1, awk 5.1.0
  49     # Ref/Attrib: [1] "Check existence of input argument in a Bash shell script". https://stackoverflow.com/a/6482403
  50     #             [2] "How do I test if a variable is a number in Bash?". https://stackoverflow.com/a/806923
  51     #             [3] "Round a Number in a Bash Script". https://bits.mdminhazulhaque.io/linux/round-number-in-bash-script.html
  52     #             [4] "Logarithms in GNU bc". https://web.archive.org/web/20210211050732/http://phodd.net/gnu-bc/bcfaq.html#bclog
  53     #             [5] "BIP 173". Note: bech32 charset. https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki
  54     #             [6] "Bash Function to generate random password". https://www.thegeekstuff.com/2010/04/unix-bash-function-examples/
  55     charset="qpzry9x8gf2tvdw0s3jn54khce6mua7l"; # bech32. See [5].
  56     charset="$(tr -s "$charset" < <(echo -n "$charset"))"; # remove repeat chars
  57     alphabet_size="$(echo -n "$charset" | wc -c)"; # number of unique chars
  58     log_base=2; # entropy unit base (i.e. 2 for "bits of entropy")
  59
  60     # Check inputs
  61     if [[ $# -gt 1 ]]; then showUsage; die "ERROR:Too many arguments:$#"; fi;
  62
  63     # Check for bc
  64     if ! command -v bc 1>/dev/null 2>&1; then die "ERROR:bc not available"; fi;
  65
  66     ## Get entropy_bit_count
  67     if [[ -z "$1" ]]; then
  68         ### prompt user
  69         showUsage;
  70         echo -n "Please specify the required strength of the password in bits of entropy (ex: 256):" 1>&2; # prompt via stderr
  71         read -r entropy_bit_count
  72     else
  73         entropy_bit_count="$1";
  74     fi; # See [1].
  75
  76     ## Check entropy_bit_count
  77     pattern="^[0-9]+$";
  78     if ! [[ $entropy_bit_count =~ $pattern ]] ; then die "ERROR:Not an integer:$entropy_bit_count"; fi; # See [2]
  79
  80     ## Calculate minimum count of chars needed for passphrase as float using 'bc'
  81     ###      Solve ln(a^n)/ln(2)=b for n where:
  82     ###      a=$alphabet_size
  83     ###      n=$char_count_float
  84     ###      b=$entropy_bit_count
  85     char_count_float="$(echo "$entropy_bit_count*l($log_base)/l($alphabet_size)" | bc -l)"; # See [4]
  86
  87     ## Round $char_count_float to next highest integer
  88     char_count="$(echo "$char_count_float" | awk '{print ($0-int($0)>0)?int($0)+1:int($0)}')"; # See [3]
  89
  90     ## Generate and output passphrase
  91     echo "$(LC_ALL=C tr -cd "$charset" < /dev/urandom | head -c "$char_count")"; # See [6]
  92 }; # main program
  93
  94 ( main "$@" ); # run 'main()' in subshell for 'die()' portability of script as sourced bash function.
  95
  96 #==References==
  97 #
  98 # - How to echo a string as stderr instead of stdout.
  99 #   https://stackoverflow.com/a/2990533
 100 #   Author: James Roth
 101 #   Date: 2010-06-07T14:52Z
 102 #   Date Accessed: 2020-01-20
 103 #
 104 # - How to check if script argument exists or not.
 105 #   https://stackoverflow.com/a/6482403
 106 #   Author: phoxix
 107 #   Date: 2011-06-26T05:55Z
 108 #   Date Accessed: 2020-01-20
 109 #
 110 # - How to check that a string is an integer using regular expression test.
 111 #   https://stackoverflow.com/a/806923
 112 #   Author: Charles Duffy
 113 #   Date: 2009-04-30T13:32Z
 114 #   Date Accessed: 2020-01-20
 115 #
 116 # - How to use `bc` to calculate logarithms in Bash
 117 #   http://phodd.net/gnu-bc/bcfaq.html#bashlog
 118 #   Author: unknown
 119 #   Date Accessed: 2020-01-20
 120 #
 121 # - How to use `awk` to convert and round up a float to an integer.
 122 #   https://bits.mdminhazulhaque.io/linux/round-number-in-bash-script.html
 123 #   Author: Md. Minhazul Haque
 124 #   Date: 2015-01-09
 125 #   Date Accessed: 2020-01-20
 126 #
 127 # - How to use `/dev/urandom`, `tr`, and `head` to generate a random password in Bash.
 128 #   https://www.thegeekstuff.com/2010/04/unix-bash-function-examples/
 129 #   Author: SASIKALA, Ramesh Natarajan
 130 #   Date: 2010-04-21
 131 #   Date Accessed: 2020-01-20
 132 #
 133 # - Bech32 base32 charset
 134 #   https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki
 135 #   Author: Pieter Wuille <pieter.wuille@gmail.com>
 136 #   Date: 2017-03-20
 137 #   License: BSD-2-Clause
 138 #   Date: Accessed: 2021-01-23
 139 #
 140 # - Dependencies: bash, bc, echo, awk, tr, head
 141 #
 142 #     - GNU bash, version 5.1.8(1)-release (x86_64-pc-linux-gnu)
 143 #       Copyright (C) 2020 Free Software Foundation, Inc.
 144 #       License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
 145 #       This is free software; you are free to change and redistribute it.
 146 #       There is NO WARRANTY, to the extent permitted by law.
 147 #
 148 #     - bc 1.07.1
 149 #       Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006, 2008, 2012-2017 Free Software Foundation, Inc.
 150 #
 151 #     - echo (GNU coreutils) 8.32
 152 #       Copyright (C) 2020 Free Software Foundation, Inc.
 153 #       License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
 154 #       This is free software: you are free to change and redistribute it.
 155 #       There is NO WARRANTY, to the extent permitted by law.
 156 #
 157 #       Written by Brian Fox and Chet Ramey.
 158 #
 159 #     - GNU Awk 5.1.0, API: 3.0 (GNU MPFR 4.1.0, GNU MP 6.2.1)
 160 #       Copyright (C) 1989, 1991-2020 Free Software Foundation.
 161 #
 162 #       This program is free software; you can redistribute it and/or modify
 163 #       it under the terms of the GNU General Public License as published by
 164 #       the Free Software Foundation; either version 3 of the License, or
 165 #       (at your option) any later version.
 166 #
 167 #       This program is distributed in the hope that it will be useful,
 168 #       but WITHOUT ANY WARRANTY; without even the implied warranty of
 169 #       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 170 #       GNU General Public License for more details.
 171 #
 172 #       You should have received a copy of the GNU General Public License
 173 #       along with this program. If not, see http://www.gnu.org/licenses/.
 174 #
 175 #     - tr (GNU coreutils) 8.32
 176 #       Copyright (C) 2020 Free Software Foundation, Inc.
 177 #       License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
 178 #       This is free software: you are free to change and redistribute it.
 179 #       There is NO WARRANTY, to the extent permitted by law.
 180 #
 181 #       Written by Jim Meyering.
 182 #
 183 #     - head (GNU coreutils) 8.32
 184 #       Copyright (C) 2020 Free Software Foundation, Inc.
 185 #       License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
 186 #       This is free software: you are free to change and redistribute it.
 187 #       There is NO WARRANTY, to the extent permitted by law.
 188 #
 189 #       Written by David MacKenzie and Jim Meyering.