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lib/Authen/DecHpwd.pm  view on Meta::CPAN

=head1 NAME

Authen::DecHpwd - DEC VMS password hashing

=head1 SYNOPSIS

	use Authen::DecHpwd qw(
		UAI_C_AD_II UAI_C_PURDY UAI_C_PURDY_V UAI_C_PURDY_S
		lgi_hpwd
	);

	$hash = lgi_hpwd("JRANDOM", "PASSWORD", UAI_C_PURDY_S, 1234);

	use Authen::DecHpwd qw(vms_username vms_password);

	$username = vms_username($username);
	$password = vms_password($password);

=head1 DESCRIPTION

This module implements the C<SYS$HASH_PASSWORD> password hashing function
from VMS (also known as C<LGI$HPWD>), and some associated VMS username
and password handling functions.

The password hashing function is implemented in XS, with a hideously
slow pure Perl backup version for systems that can't handle XS.

=cut

package Authen::DecHpwd;

{ use 5.006; }
use warnings;
use strict;

use Digest::CRC 0.14 qw(crc32);

our $VERSION = "2.007";

use parent "Exporter";
our @EXPORT_OK = qw(
	UAI_C_AD_II UAI_C_PURDY UAI_C_PURDY_V UAI_C_PURDY_S
	lgi_hpwd
	vms_username vms_password
);

eval { local $SIG{__DIE__};
	require XSLoader;
	XSLoader::load(__PACKAGE__, $VERSION);
};

=head1 FUNCTIONS

=over

=item UAI_C_AD_II

=item UAI_C_PURDY

=item UAI_C_PURDY_V

=item UAI_C_PURDY_S

These constants are used to identify the four password hashing algorithms
used by VMS.  They are the C<UAI$C_> constants in VMS.

C<UAI_C_AD_II> refers to a 32-bit CRC algorithm.  The CRC polynomial used
is the IEEE CRC-32 polynomial, as used in Ethernet, and in this context
is known as "AUTODIN-II".  The hash is merely the CRC of the password.

C<UAI_C_PURDY>, C<UAI_C_PURDY_V>, and C<UAI_C_PURDY_S> refer to successive
refinements of an algorithm based on Purdy polynomials.  All of these
algorithms use the salt and username parameters as salt, use the whole
password, and return an eight-byte (64-bit) hash.  The main part
of the algorithm, the Purdy polynomial, is identical in all three.
They differ in the pre-hashing, particularly in the treatment of the
username parameter.

In C<UAI_C_PURDY> the username is truncated or space-padded to 12 characters
before being hashed in.  C<UAI_C_PURDY_V> accepts a variable-length username.
C<UAI_C_PURDY_S> accepts a variable-length username and also includes the
password length in the hash.  C<UAI_C_PURDY_S> also does some extra bit
rotations when hashing in the username and password strings, in order
to avoid aliasing.

=cut