The following commands are available when this module is loaded:
Copyright (c) 2015-2017 Vegard IT GmbH, http://vegardit.com
SPDX-License-Identifier: Apache-2.0
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
Usage: -entropy-available [OPTION]...
Determines if enough entropy bits are available perform a non-blocking read from /dev/random. Exit code 1 indicates entropy pool is not sufficiently filled.
Options:
--help
Prints this help.
--selftest
Performs a self-test.
--
Terminates the option list.
Examples:
$ -entropy-available
1235
Implementation:
if [[ ! -e /proc/sys/kernel/random/read_wakeup_threshold ]]; then
echo "-entropy-available: Warning: Kernel parameter /proc/sys/kernel/random/read_wakeup_threshold is not present, assuming sufficient entropy is available."
return 0
fi
local avail=$(cat /proc/sys/kernel/random/entropy_avail)
local required=$(cat /proc/sys/kernel/random/read_wakeup_threshold)
echo "/proc/sys/kernel/random/entropy_avail: $avail"
echo "/proc/sys/kernel/random/read_wakeup_threshold: $required"
[[ $(( avail > required )) ]]Usage: -fill-entropy [OPTION]... [DURATION]
Fills /dev/random with pseudo-random values from /dev/urandom.
Requirements:
+ Command 'rngd' must be available.
+ Sudo 'rngd' is required.
Parameters:
DURATION (default: '1', integer: 1-?)
Number of seconds the entropy pool will be filled.
Options:
--help
Prints this help.
--selftest
Performs a self-test.
--
Terminates the option list.
Examples:
$ -fill-entropy
1235
Implementation:
echo -n "Available entropy bits before:"
cat /proc/sys/kernel/random/entropy_avail
echo "Generating..."
if rngd --help | grep -q -- --timeout; then
sudo rngd -r /dev/urandom -o /dev/random -f --timeout ${_DURATION}
else
-timeout ${_DURATION} sudo rngd -r /dev/urandom -o /dev/random -f
fi
echo -n "Available entropy bits after:"
cat /proc/sys/kernel/random/entropy_availUsage: -random-number [OPTION]... RANGE
Generates a random number of the given range. The range is inclusive.
Parameters:
RANGE (required, pattern: "[1-9][0-9]*-[1-9][0-9]*")
The numeric range LOW-HIGH, e.g. 1-5.
Options:
--help
Prints this help.
--selftest
Performs a self-test.
--
Terminates the option list.
Examples:
$ -random-number 1-1
1
$ -random-number 1-5
4
$ -random-number 200-299
253
Implementation:
shuf -i ${_RANGE} -n 1Usage: -random-string [OPTION]... LENGTH [CHARS]
Prints a random string of the given length containing the given characters.
Parameters:
LENGTH (required, integer: 1-?)
Length of the string to generate.
CHARS (default: '[:graph:]')
String to choose random characters from.
Options:
--help
Prints this help.
--selftest
Performs a self-test.
--
Terminates the option list.
Examples:
$ -random-string 12 0-9
686026902293
$ -random-string 8 a-zA-Z
ECtQptCz
$ -random-string 10 [:alnum:]
w2TZ8fHaRw
$ -random-string 10 [:alnum:][:punct:]
4pH?+40D):
Implementation:
local rc
env LC_CTYPE=C tr -dc "$_CHARS" < /dev/urandom | fold -w ${_LENGTH} | head -n 1
# https://stackoverflow.com/questions/19120263/why-exit-code-141-with-grep-q
rc=$?
(( rc == 141 )) && return 0 || return $rcUsage: -test-random [OPTION]...
Performs a selftest of all functions of this module by executing each function with option '--selftest'.
Options:
--help
Prints this help.
--selftest
Performs a self-test.
--
Terminates the option list.
Implementation:
-entropy-available --selftest && echo || return 1
-fill-entropy --selftest && echo || return 1
-random-number --selftest && echo || return 1
-random-string --selftest && echo || return 1