fix(user/bkots):Fix shellcheck delinter complaints
[BK-2020-03.git] / unitproc / bknpass
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CommitLineData
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
25yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
26die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
27try() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
28showUsage() {
29 # Desc: Display script usage information
30 # Usage: showUsage
31 # Version 0.0.1
32 # Input: none
33 # Output: stdout
34 # Depends: GNU-coreutils 8.30 (cat)
35 cat <<'EOF'
36 USAGE:
37 bknpass [int entropy_bit_count]
38
39 EXAMPLE:
40 bknpass 128
41EOF
42}; # Display information on how to use this script.
43main() {
44 # Desc: main program
45 # Usage: main "$@"
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.