[BK-2020-03.git] / user / bknpass

#!/bin/bash

# Author: Steven Baltakatei Sandoval (baltakatei.com)
#
# License: This bash script, `bknpass`, is licensed under GPLv3 or
# later by Steven Baltakatei Sandoval:
#
#    `bknpass`, an alphanumeric password generator
#    Copyright (C) 2021  Steven Baltakatei Sandoval (baltakatei.com)
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    A copy of the GNU General Public License may be found at
#    <https://www.gnu.org/licenses/>.
#
# Description: This bash script generates alphanumeric passphrases
# with a char-count determined by a user-provided number of bits of
# entropy. The passphrase is then outputted to stdout with a trailing
# newline. It works as follows:
# 
#   - Prompt user for an integer. This integer is the number of bits
#     of entropy that the generated password should have.
#
#   - Check if user-provided string is an integer using `bash` regular
#     expression test.
#
#   - Calculate the minimum number of bech32 base32 characters
#     required to encode the specified number of bits of entropy.
#
#       - This step uses `bc` to calculate a logarithm float string
#         and `awk` to convert the float into an integer, rounding up.
#
#   - Use `tr`, `/dev/urandom`, and `head` to generate a random
#     alphanumeric string with the length calculated in the previous
#     step.
#
#   - Use `echo` to display the passphrase in stdout with a trailing
#     newline.
#
# Usage: bknpass [int]
#
# Example: bknpass 256
#
# Dependencies: bash, echo, bc, awk, tr, head. See end of file
#
# Tested on:
#
#   - GNU/Linux Debian 10


#==Initialization==

let ALPHABET_SIZE="32" # number of unique chars in bech32 base32 charset
LOG_BASE=2 # Set logarithm base to 2

# Define `echoerr` function which outputs text to stderr
    # Note: function copied from https://stackoverflow.com/a/2990533
function echoerr {
    echo "$@" 1>&2;
}

# Define `rpass` function which generates a base32 passphrase of length $1 (ex: `rpass 20` generates a 20-char string)
#   Note: function adapted from https://www.thegeekstuff.com/2010/04/unix-bash-function-examples/
#   Note: base32 charset uses bech32 charset
function rpass {
    cat /dev/urandom | LC_ALL=C tr -cd "qpzry9x8gf2tvdw0s3jn54khce6mua7l" | head -c ${1:-22}
}


#==Main Program==

# Define $ENTROPY_BIT_COUNT1 as argument $1 or prompt user if $1 is not defined.
#     Note: argument test adapted from https://stackoverflow.com/a/6482403
if [ -z "$1" ]
then
    echo "Entropy bit count argument (\$1) not supplied."
    # Get from user the number of bits of entropy.
    echoerr -n "Please specify the required strength of the password in bits of entropy (ex: 256):" # prompt via stderr
    read ENTROPY_BIT_COUNT1
else
    ENTROPY_BIT_COUNT1="$1"
fi

# Check if $ENTROPY_BIT_COUNT1 is an non-negative integer
#     Note: Regular expression test is adapted from https://stackoverflow.com/a/806923
RETEST1='^[0-9]+$'
if ! [[ $ENTROPY_BIT_COUNT1 =~ $RETEST1 ]] ; then
   echo "error: Not an integer." >&2; exit 1    
fi

# Calculate minimum count of chars needed to encode $ENTROPY_BIT_COUNT1 with alphabet size of $ALPHABET_SIZE as float
#     Solve ln(a^n)/ln(2)=b for n using `bc` where
#       a=$ALPHABET_SIZE
#       n=$CHAR_COUNT1_FLOAT
#       b=$ENTROPY_BIT_COUNT1
#     Note: `bc` logarithm usage adapted from http://phodd.net/gnu-bc/bcfaq.html#bashlog
CHAR_COUNT1_FLOAT=$(echo "$ENTROPY_BIT_COUNT1*l($LOG_BASE)/l($ALPHABET_SIZE)" | bc -l)
#     Note: Float will be of form "21.49744370650136860806".
#     Note: This particular example float should be rounded to "22" later.

# Round $CHAR_COUNT1_FLOAT1 up to next highest integer for use as argument in later bash functions.
#     Note: awk expression from https://bits.mdminhazulhaque.io/linux/round-number-in-bash-script.html
CHAR_COUNT1=$(echo "$CHAR_COUNT1_FLOAT" | awk '{print ($0-int($0)>0)?int($0)+1:int($0)}') 

# Generate passphrase
PASS1=$(rpass "$CHAR_COUNT1")
echo -e "$PASS1"


#==References==
#
# - How to echo a string as stderr instead of stdout.
#   https://stackoverflow.com/a/2990533
#   Author: James Roth
#   Date: 2010-06-07T14:52Z
#   Date Accessed: 2020-01-20
#
# - How to check if script argument exists or not.
#   https://stackoverflow.com/a/6482403
#   Author: phoxix
#   Date: 2011-06-26T05:55Z
#   Date Accessed: 2020-01-20
#
# - How to check that a string is an integer using regular expression test.
#   https://stackoverflow.com/a/806923
#   Author: Charles Duffy
#   Date: 2009-04-30T13:32Z
#   Date Accessed: 2020-01-20
#
# - How to use `bc` to calculate logarithms in Bash
#   http://phodd.net/gnu-bc/bcfaq.html#bashlog
#   Author: unknown
#   Date Accessed: 2020-01-20
#
# - How to use `awk` to convert and round up a float to an integer.
#   https://bits.mdminhazulhaque.io/linux/round-number-in-bash-script.html
#   Author: Md. Minhazul Haque
#   Date: 2015-01-09
#   Date Accessed: 2020-01-20
#
# - How to use `/dev/urandom`, `tr`, and `head` to generate a random password in Bash.
#   https://www.thegeekstuff.com/2010/04/unix-bash-function-examples/
#   Author: SASIKALA, Ramesh Natarajan
#   Date: 2010-04-21
#   Date Accessed: 2020-01-20
#
# - Bech32 base32 charset
#   https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki
#   Author: Pieter Wuille <pieter.wuille@gmail.com>
#   Date: 2017-03-20
#   License: BSD-2-Clause
#   Date: Accessed: 2021-01-23
#
# - Dependencies: bash, echo, bc, awk, tr, head.
#
#     - GNU bash, version 5.0.3(1)-release (x86_64-pc-linux-gnu)
#       Copyright (C) 2019 Free Software Foundation, Inc.
#       License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
#       This is free software; you are free to change and redistribute it.
#       There is NO WARRANTY, to the extent permitted by law.
#    
#     - echo (GNU coreutils) 8.30
#       Copyright (C) 2018 Free Software Foundation, Inc.
#       License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
#       This is free software: you are free to change and redistribute it.
#       There is NO WARRANTY, to the extent permitted by law.
#
#       Written by Brian Fox and Chet Ramey.
#    
#     - bc 1.07.1
#       Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006, 2008, 2012-2017 Free Software Foundation, Inc.
#    
#     - GNU Awk 4.2.1, API: 2.0 (GNU MPFR 4.0.2, GNU MP 6.1.2)
#       Copyright (C) 1989, 1991-2018 Free Software Foundation.
#    
#       This program is free software; you can redistribute it and/or modify
#       it under the terms of the GNU General Public License as published by
#       the Free Software Foundation; either version 3 of the License, or
#       (at your option) any later version.
#    
#       This program is distributed in the hope that it will be useful,
#       but WITHOUT ANY WARRANTY; without even the implied warranty of
#       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#       GNU General Public License for more details.
#    
#       You should have received a copy of the GNU General Public License
#       along with this program. If not, see http://www.gnu.org/licenses/.
#    
#     - tr (GNU coreutils) 8.30
#       Copyright (C) 2018 Free Software Foundation, Inc.
#       License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
#       This is free software: you are free to change and redistribute it.
#       There is NO WARRANTY, to the extent permitted by law.
#    
#       Written by Jim Meyering.
#    
#     - head (GNU coreutils) 8.30
#       Copyright (C) 2018 Free Software Foundation, Inc.
#       License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
#       This is free software: you are free to change and redistribute it.
#       There is NO WARRANTY, to the extent permitted by law.
#    
#       Written by David MacKenzie and Jim Meyering.
Commit	Line	Data
2feb5df8 SBS	1	#!/bin/bash
	2
	3	# Author: Steven Baltakatei Sandoval (baltakatei.com)
	4	#
	5	# License: This bash script, `bknpass`, is licensed under GPLv3 or
	6	# later by Steven Baltakatei Sandoval:
	7	#
	8	# `bknpass`, an alphanumeric password generator
	9	# Copyright (C) 2021 Steven Baltakatei Sandoval (baltakatei.com)
	10	#
	11	# This program is free software: you can redistribute it and/or modify
	12	# it under the terms of the GNU General Public License as published by
	13	# the Free Software Foundation, either version 3 of the License, or
	14	# any later version.
	15	#
	16	# This program is distributed in the hope that it will be useful,
	17	# but WITHOUT ANY WARRANTY; without even the implied warranty of
	18	# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	19	# GNU General Public License for more details.
	20	#
	21	# A copy of the GNU General Public License may be found at
	22	# <https://www.gnu.org/licenses/>.
	23	#
	24	# Description: This bash script generates alphanumeric passphrases
	25	# with a char-count determined by a user-provided number of bits of
	26	# entropy. The passphrase is then outputted to stdout with a trailing
	27	# newline. It works as follows:
	28	#
	29	# - Prompt user for an integer. This integer is the number of bits
	30	# of entropy that the generated password should have.
	31	#
	32	# - Check if user-provided string is an integer using `bash` regular
	33	# expression test.
	34	#
	35	# - Calculate the minimum number of bech32 base32 characters
	36	# required to encode the specified number of bits of entropy.
	37	#
	38	# - This step uses `bc` to calculate a logarithm float string
	39	# and `awk` to convert the float into an integer, rounding up.
	40	#
	41	# - Use `tr`, `/dev/urandom`, and `head` to generate a random
	42	# alphanumeric string with the length calculated in the previous
	43	# step.
	44	#
	45	# - Use `echo` to display the passphrase in stdout with a trailing
	46	# newline.
	47	#
	48	# Usage: bknpass [int]
	49	#
	50	# Example: bknpass 256
	51	#
	52	# Dependencies: bash, echo, bc, awk, tr, head. See end of file
	53	#
	54	# Tested on:
	55	#
	56	# - GNU/Linux Debian 10
	57
	58
	59	#==Initialization==
	60
	61	let ALPHABET_SIZE="32" # number of unique chars in bech32 base32 charset
	62	LOG_BASE=2 # Set logarithm base to 2
	63
	64	# Define `echoerr` function which outputs text to stderr
65	# Note: function copied from https://stackoverflow.com/a/2990533
66	function echoerr {
67	echo "$@" 1>&2;
68	}
69
70	# Define `rpass` function which generates a base32 passphrase of length $1 (ex: `rpass 20` generates a 20-char string)
71	# Note: function adapted from https://www.thegeekstuff.com/2010/04/unix-bash-function-examples/
72	# Note: base32 charset uses bech32 charset
73	function rpass {
74	cat /dev/urandom \| LC_ALL=C tr -cd "qpzry9x8gf2tvdw0s3jn54khce6mua7l" \| head -c ${1:-22}
75	}
76
77
78	#==Main Program==
79
80	# Define $ENTROPY_BIT_COUNT1 as argument $1 or prompt user if $1 is not defined.
81	# Note: argument test adapted from https://stackoverflow.com/a/6482403
82	if [ -z "$1" ]
83	then
84	echo "Entropy bit count argument (\$1) not supplied."
85	# Get from user the number of bits of entropy.
86	echoerr -n "Please specify the required strength of the password in bits of entropy (ex: 256):" # prompt via stderr
87	read ENTROPY_BIT_COUNT1
88	else
89	ENTROPY_BIT_COUNT1="$1"
90	fi
91
92	# Check if $ENTROPY_BIT_COUNT1 is an non-negative integer
93	# Note: Regular expression test is adapted from https://stackoverflow.com/a/806923
94	RETEST1='^[0-9]+$'
95	if ! [[ $ENTROPY_BIT_COUNT1 =~ $RETEST1 ]] ; then
96	echo "error: Not an integer." >&2; exit 1
97	fi
98
99	# Calculate minimum count of chars needed to encode $ENTROPY_BIT_COUNT1 with alphabet size of $ALPHABET_SIZE as float
100	# Solve ln(a^n)/ln(2)=b for n using `bc` where
101	# a=$ALPHABET_SIZE
102	# n=$CHAR_COUNT1_FLOAT
103	# b=$ENTROPY_BIT_COUNT1
104	# Note: `bc` logarithm usage adapted from http://phodd.net/gnu-bc/bcfaq.html#bashlog
105	CHAR_COUNT1_FLOAT=$(echo "$ENTROPY_BIT_COUNT1*l($LOG_BASE)/l($ALPHABET_SIZE)" \| bc -l)
106	# Note: Float will be of form "21.49744370650136860806".
107	# Note: This particular example float should be rounded to "22" later.
108
109	# Round $CHAR_COUNT1_FLOAT1 up to next highest integer for use as argument in later bash functions.
110	# Note: awk expression from https://bits.mdminhazulhaque.io/linux/round-number-in-bash-script.html
111	CHAR_COUNT1=$(echo "$CHAR_COUNT1_FLOAT" \| awk '{print ($0-int($0)>0)?int($0)+1:int($0)}')
112
113	# Generate passphrase
114	PASS1=$(rpass "$CHAR_COUNT1")
115	echo -e "$PASS1"
116
117
118	#==References==
119	#
120	# - How to echo a string as stderr instead of stdout.
121	# https://stackoverflow.com/a/2990533
122	# Author: James Roth
123	# Date: 2010-06-07T14:52Z
124	# Date Accessed: 2020-01-20
125	#
126	# - How to check if script argument exists or not.
127	# https://stackoverflow.com/a/6482403
128	# Author: phoxix
129	# Date: 2011-06-26T05:55Z
130	# Date Accessed: 2020-01-20
131	#
132	# - How to check that a string is an integer using regular expression test.
133	# https://stackoverflow.com/a/806923
134	# Author: Charles Duffy
135	# Date: 2009-04-30T13:32Z
136	# Date Accessed: 2020-01-20
137	#
138	# - How to use `bc` to calculate logarithms in Bash
139	# http://phodd.net/gnu-bc/bcfaq.html#bashlog
140	# Author: unknown
141	# Date Accessed: 2020-01-20
142	#
143	# - How to use `awk` to convert and round up a float to an integer.
144	# https://bits.mdminhazulhaque.io/linux/round-number-in-bash-script.html
145	# Author: Md. Minhazul Haque
146	# Date: 2015-01-09
147	# Date Accessed: 2020-01-20
148	#
149	# - How to use `/dev/urandom`, `tr`, and `head` to generate a random password in Bash.
150	# https://www.thegeekstuff.com/2010/04/unix-bash-function-examples/
151	# Author: SASIKALA, Ramesh Natarajan
152	# Date: 2010-04-21
153	# Date Accessed: 2020-01-20
154	#
155	# - Bech32 base32 charset
156	# https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki
157	# Author: Pieter Wuille <pieter.wuille@gmail.com>
158	# Date: 2017-03-20
159	# License: BSD-2-Clause
160	# Date: Accessed: 2021-01-23
161	#
162	# - Dependencies: bash, echo, bc, awk, tr, head.
163	#
164	# - GNU bash, version 5.0.3(1)-release (x86_64-pc-linux-gnu)
165	# Copyright (C) 2019 Free Software Foundation, Inc.
166	# License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
167	# This is free software; you are free to change and redistribute it.
168	# There is NO WARRANTY, to the extent permitted by law.
169	#
170	# - echo (GNU coreutils) 8.30
171	# Copyright (C) 2018 Free Software Foundation, Inc.
172	# License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
173	# This is free software: you are free to change and redistribute it.
174	# There is NO WARRANTY, to the extent permitted by law.
175	#
176	# Written by Brian Fox and Chet Ramey.
177	#
178	# - bc 1.07.1
179	# Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006, 2008, 2012-2017 Free Software Foundation, Inc.
180	#
181	# - GNU Awk 4.2.1, API: 2.0 (GNU MPFR 4.0.2, GNU MP 6.1.2)
182	# Copyright (C) 1989, 1991-2018 Free Software Foundation.
183	#
184	# This program is free software; you can redistribute it and/or modify
185	# it under the terms of the GNU General Public License as published by
186	# the Free Software Foundation; either version 3 of the License, or
187	# (at your option) any later version.
188	#
189	# This program is distributed in the hope that it will be useful,
190	# but WITHOUT ANY WARRANTY; without even the implied warranty of
191	# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
192	# GNU General Public License for more details.
193	#
194	# You should have received a copy of the GNU General Public License
195	# along with this program. If not, see http://www.gnu.org/licenses/.
196	#
197	# - tr (GNU coreutils) 8.30
198	# Copyright (C) 2018 Free Software Foundation, Inc.
199	# License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
200	# This is free software: you are free to change and redistribute it.
201	# There is NO WARRANTY, to the extent permitted by law.
202	#
203	# Written by Jim Meyering.
204	#
205	# - head (GNU coreutils) 8.30
206	# Copyright (C) 2018 Free Software Foundation, Inc.
207	# License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
208	# This is free software: you are free to change and redistribute it.
209	# There is NO WARRANTY, to the extent permitted by law.
210	#
211	# Written by David MacKenzie and Jim Meyering.