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package Math::Prime::Util::Entropy;
use strict;
use warnings;
use Carp qw/carp croak confess/;
BEGIN {
$Math::Prime::Util::Entropy::AUTHORITY = 'cpan:DANAJ';
$Math::Prime::Util::Entropy::VERSION = '0.73';
}
sub _read_file {
my($file, $nbytes) = @_;
use Fcntl;
my($s, $buffer, $nread) = ('', '', 0);
return unless -r $file;
sysopen(my $fh, $file, O_RDONLY);
binmode $fh;
while ($nread < $nbytes) {
my $thisread = sysread $fh, $buffer, $nbytes-$nread;
last unless defined $thisread && $thisread > 0;
$s .= $buffer;
$nread += length($buffer);
}
return unless $nbytes == length($s);
return $s;
}
sub _try_urandom {
if (-r "/dev/urandom") {
return ('urandom', sub { _read_file("/dev/urandom",shift); }, 0, 1);
}
if (-r "/dev/random") {
return ('random', sub { _read_file("/dev/random",shift); }, 1, 1);
}
return;
}
sub _try_win32 {
return unless $^O eq 'MSWin32';
eval { require Win32; require Win32::API; require Win32::API::Type; 1; }
or return;
use constant CRYPT_SILENT => 0x40; # Never display a UI.
use constant PROV_RSA_FULL => 1; # Which service provider.
use constant VERIFY_CONTEXT => 0xF0000000; # Don't need existing keepairs
use constant W2K_MAJOR_VERSION => 5; # Windows 2000
use constant W2K_MINOR_VERSION => 0;
my ($major, $minor) = (Win32::GetOSVersion())[1, 2];
return if $major < W2K_MAJOR_VERSION;
if ($major == W2K_MAJOR_VERSION && $minor == W2K_MINOR_VERSION) {
# We are Windows 2000. Use the older CryptGenRandom interface.
my $crypt_acquire_context_a =
Win32::API->new('advapi32','CryptAcquireContextA','PPPNN','I');
return unless defined $crypt_acquire_context_a;
my $context = chr(0) x Win32::API::Type->sizeof('PULONG');
my $result = $crypt_acquire_context_a->Call(
$context, 0, 0, PROV_RSA_FULL, CRYPT_SILENT | VERIFY_CONTEXT );
return unless $result;
my $pack_type = Win32::API::Type::packing('PULONG');
$context = unpack $pack_type, $context;
my $crypt_gen_random =
Win32::API->new( 'advapi32', 'CryptGenRandom', 'NNP', 'I' );
return unless defined $crypt_gen_random;
return ('CryptGenRandom',
sub {
my $nbytes = shift;
my $buffer = chr(0) x $nbytes;
my $result = $crypt_gen_random->Call($context, $nbytes, $buffer);
croak "CryptGenRandom failed: $^E" unless $result;
return $buffer;
}, 0, 1); # Assume non-blocking and strong
} else {
my $rtlgenrand = Win32::API->new( 'advapi32', <<'_RTLGENRANDOM_PROTO_');
INT SystemFunction036(
PVOID RandomBuffer,
ULONG RandomBufferLength
)
_RTLGENRANDOM_PROTO_
return unless defined $rtlgenrand;
return ('RtlGenRand',
sub {
my $nbytes = shift;
my $buffer = chr(0) x $nbytes;
my $result = $rtlgenrand->Call($buffer, $nbytes);
croak "RtlGenRand failed: $^E" unless $result;
return $buffer;
}, 0, 1); # Assume non-blocking and strong
}
return;
}
sub _try_crypt_prng {
return unless eval { require Crypt::PRNG; 1; };
return ('Crypt::PRNG', sub { Crypt::PRNG::random_bytes(shift) }, 0, 1);
}
sub _try_crypt_random_seed {
return unless eval { require Crypt::Random::Seed; 1; };
return ('Crypt::Random::Seed', sub { my $source = Crypt::Random::Seed->new(NonBlocking=>1); return unless $source; $source->random_bytes(shift) }, 0, 1);
}
my $_method;
sub entropy_bytes {
my $nbytes = shift;
my @methodlist = ( \&_try_win32, # All we have for Windows
\&_try_urandom, # Best if available
\&_try_crypt_random_seed, # More sources, fallbacks
\&_try_crypt_prng, # Good CSPRNG, worse seeding
);
if (!defined $_method) {
foreach my $m (@methodlist) {
my ($name, $rsub, $isblocking, $isstrong) = $m->();
if (defined $name) {
$_method = $rsub;
last;
}
}
}
return unless defined $_method;
$_method->($nbytes);
}
1;
__END__
# ABSTRACT: Get a good random seed
=pod
=encoding utf8
=head1 NAME
Math::Prime::Util::Entropy - Get a good random seed
=head1 VERSION
Version 0.73
=head1 SYNOPSIS
=head1 DESCRIPTION
Provides a single method to get a good seed if possible. This is a streamlined
version of L<Crypt::Random::Seed>, with ideas from L<Bytes::Random::Secure::Tiny>.
=head2 entropy_bytes
Takes a number of bytes C<n> and returns either undef (no good seed available) or
a binary string with good entropy.
We try in order:
- the Win32 Crypto API
- /dev/urandom
- /dev/random
- L<Crypt::Random::Seed>
- L<Crypt::PRNG>
=head1 SEE ALSO
L<Math::Prime::Util>
L<Crypt::Random::Seed>
L<Bytes::Random::Secure>
L<Bytes::Random::Secure::Tiny>
L<Crypt::PRNG>
=head1 AUTHORS
Dana Jacobsen E<lt>dana@acm.orgE<gt>
=head1 COPYRIGHT
Copyright 2017 by Dana Jacobsen E<lt>dana@acm.orgE<gt>
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
=cut
|
