+#!/bin/bash
+
+# Date: 2020-01-20T16:34Z
+#
+# 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) 2020 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 alphanumeric 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.
+#
+# Dependencies: bash, echo, bc, awk, tr, head. See end of file
+#
+# Tested on:
+#
+# - GNU/Linux Debian 10
+
+
+#==Initialization==
+
+let ALPHABET_SIZE="26+26+10" # number of unique chars in [:alnum:], argument fed to `tr -c` in 'Generate passphrase' step)
+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 an alphanumeric passphrase of length $1 (ex: `rpass 22` generates a 22-char string)
+ # Note: function adapted from https://www.thegeekstuff.com/2010/04/unix-bash-function-examples/
+function rpass {
+ cat /dev/urandom | LC_ALL=C tr -cd "[:alnum:]" | 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". This particular 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
+#
+# - 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.
projects / BK-2020-03.git / commitdiff