#!/bin/bash
-
-# Author: Steven Baltakatei Sandoval (baltakatei.com)
-#
-# License: This bash script, `bknpass`, is licensed under GPLv3 or
-# later by Steven Baltakatei Sandoval:
-#
+# Desc: Generate passphrase with specified number of bits of entropy
+# Usage: bknpass [integer]
+# Example: bknpass 256
+# Result: 9tnzcl0m4dsm22a95525zj93jj
+# Version: 0.2.1
+# Depends: bash 5.1.8, GNU coreutils 8.32, bc 1.07.1, awk 5.1.0
+# License:
# `bknpass`, an alphanumeric password generator
-# Copyright (C) 2021 Steven Baltakatei Sandoval (baltakatei.com)
+# Copyright (C) 2022 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
#
# 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
+yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
+die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
+try() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
+showUsage() {
+ # Desc: Display script usage information
+ # Usage: showUsage
+ # Version 0.0.1
+ # Input: none
+ # Output: stdout
+ # Depends: GNU-coreutils 8.30 (cat)
+ cat <<'EOF'
+ USAGE:
+ bknpass [int entropy_bit_count]
-# Define `echoerr` function which outputs text to stderr
- # Note: function copied from https://stackoverflow.com/a/2990533
-function echoerr {
- echo "$@" 1>&2;
-}
+ EXAMPLE:
+ bknpass 128
+EOF
+}; # Display information on how to use this script.
+main() {
+ # Desc: main program
+ # Usage: main "$@"
+ # Input: $1: integer bits of entropy
+ # Output: stdout: string passphrase
+ # Depends: bash 5.1.8, GNU coreutils 8.32, bc 1.07.1, awk 5.1.0
+ # Ref/Attrib: [1] "Check existence of input argument in a Bash shell script". https://stackoverflow.com/a/6482403
+ # [2] "How do I test if a variable is a number in Bash?". https://stackoverflow.com/a/806923
+ # [3] "Round a Number in a Bash Script". https://bits.mdminhazulhaque.io/linux/round-number-in-bash-script.html
+ # [4] "Logarithms in GNU bc". https://web.archive.org/web/20210211050732/http://phodd.net/gnu-bc/bcfaq.html#bclog
+ # [5] "BIP 173". Note: bech32 charset. https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki
+ # [6] "Bash Function to generate random password". https://www.thegeekstuff.com/2010/04/unix-bash-function-examples/
+ charset="qpzry9x8gf2tvdw0s3jn54khce6mua7l"; # bech32. See [5].
+ charset="$(tr -s "$charset" < <(echo -n "$charset"))"; # remove repeat chars
+ alphabet_size="$(echo -n "$charset" | wc -c)"; # number of unique chars
+ log_base=2; # entropy unit base (i.e. 2 for "bits of entropy")
-# 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}
-}
+ # Check inputs
+ if [[ $# -gt 1 ]]; then showUsage; die "ERROR:Too many arguments:$#"; fi;
+ # Check for bc
+ if ! command -v bc 1>/dev/null 2>&1; then die "ERROR:bc not available"; fi;
-#==Main Program==
+ ## Get entropy_bit_count
+ if [[ -z "$1" ]]; then
+ ### prompt user
+ showUsage;
+ echo -n "Please specify the required strength of the password in bits of entropy (ex: 256):" 1>&2; # prompt via stderr
+ read -r entropy_bit_count
+ else
+ entropy_bit_count="$1";
+ fi; # See [1].
-# 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="$1"
-fi
+ ## Check entropy_bit_count
+ pattern="^[0-9]+$";
+ if ! [[ $entropy_bit_count =~ $pattern ]] ; then die "ERROR:Not an integer:$entropy_bit_count"; fi; # See [2]
-# 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 =~ $RETEST1 ]] ; then
- echo "error: Not an integer." >&2; exit 1
-fi
+ ## Calculate minimum count of chars needed for passphrase as float using 'bc'
+ ### Solve ln(a^n)/ln(2)=b for n where:
+ ### a=$alphabet_size
+ ### n=$char_count_float
+ ### b=$entropy_bit_count
+ char_count_float="$(echo "$entropy_bit_count*l($log_base)/l($alphabet_size)" | bc -l)"; # See [4]
-# 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 $char_count_float to next highest integer
+ char_count="$(echo "$char_count_float" | awk '{print ($0-int($0)>0)?int($0)+1:int($0)}')"; # See [3]
-# 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"
+ ## Generate and output passphrase
+ echo "$(LC_ALL=C tr -cd "$charset" < /dev/urandom | head -c "$char_count")"; # See [6]
+}; # main program
+( main "$@" ); # run 'main()' in subshell for 'die()' portability of script as sourced bash function.
#==References==
#
# License: BSD-2-Clause
# Date: Accessed: 2021-01-23
#
-# - Dependencies: bash, echo, bc, awk, tr, head.
+# - Dependencies: bash, bc, echo, awk, tr, head
#
-# - GNU bash, version 5.0.3(1)-release (x86_64-pc-linux-gnu)
-# Copyright (C) 2019 Free Software Foundation, Inc.
+# - GNU bash, version 5.1.8(1)-release (x86_64-pc-linux-gnu)
+# Copyright (C) 2020 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.
+#
+# - bc 1.07.1
+# Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006, 2008, 2012-2017 Free Software Foundation, Inc.
+#
+# - echo (GNU coreutils) 8.32
+# Copyright (C) 2020 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.
-#
+#
+# - GNU Awk 5.1.0, API: 3.0 (GNU MPFR 4.1.0, GNU MP 6.2.1)
+# Copyright (C) 1989, 1991-2020 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.
+# - tr (GNU coreutils) 8.32
+# Copyright (C) 2020 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.
+#
+# - head (GNU coreutils) 8.32
+# Copyright (C) 2020 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 / blobdiff