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package Crypt::SysRandom;
$Crypt::SysRandom::VERSION = '0.007';
use strict;
use warnings;
use Exporter 'import';
our @EXPORT_OK = 'random_bytes';
use Carp ();
use Errno ();
if (eval { require Crypt::SysRandom::XS }) {
*random_bytes = \&Crypt::SysRandom::XS::random_bytes;
} elsif (eval { require Win32::API }) {
my $genrand = Win32::API->new('advapi32', 'INT SystemFunction036(PVOID RandomBuffer, ULONG RandomBufferLength)')
or die "Could not import SystemFunction036: $^E";
sub random_bytes_win32 {
my ($count) = @_;
return '' if $count == 0;
my $buffer = chr(0) x $count;
$genrand->Call($buffer, $count) or Carp::croak("Could not read random bytes");
return $buffer;
}
*random_bytes = \&random_bytes_win32;
} elsif (-e '/dev/urandom') {
open my $fh, '<:raw', '/dev/urandom' or die "Couldn't open /dev/urandom: $!";
sub random_bytes_urandom {
my ($count) = @_;
my ($result, $offset) = ('', 0);
while ($offset < $count) {
my $read = sysread $fh, $result, $count - $offset, $offset;
next if not defined $read and $!{EINTR};
Carp::croak("Could not read random bytes") if not defined $read or $read == 0;
$offset += $read;
}
return $result;
}
*random_bytes = \&random_bytes_urandom;
} else {
die "No source of randomness found";
}
delete @Crypt::SysRandom::{qw(random_bytes_win32 random_bytes_urandom)};
1;
# ABSTRACT: Perl interface to system randomness
__END__
=pod
=encoding UTF-8
=head1 NAME
Crypt::SysRandom - Perl interface to system randomness
=head1 VERSION
version 0.007
=head1 SYNOPSIS
use Crypt::SysRandom 'random_bytes';
my $random = random_bytes(16);
=head1 DESCRIPTION
This module uses whatever interface is available to procure cryptographically random data from the system.
=head1 FUNCTIONS
=head2 random_bytes($count)
This will fetch a string of C<$count> random bytes containing cryptographically secure random date.
=head1 Backends
The current backends are tried in order:
=over 4
=item * L<Crypt::SysRandom::XS|Crypt::SysRandom::XS>
=item * C<RtlGenRandom> using L<Win32::API|Win32::API>
=item * C</dev/urandom>
=back
=head1 AUTHOR
Leon Timmermans <fawaka@gmail.com>
=head1 COPYRIGHT AND LICENSE
This software is copyright (c) 2025 by Leon Timmermans.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
=cut
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