NAME

Authen::DecHpwd - DEC VMS password hashing

SYNOPSIS

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

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

DESCRIPTION

This module implements the LGI$HPWD password hashing function from VMS.

FUNCTIONS

lgi_hpwd(USERNAME, PASSWORD, ALGORITHM, SALT)

This is the LGI$HPWD function from VMS (but with the parameters in a different order). It hashes the PASSWORD string in a manner determined by the other parameters, and returns the hash as a string of bytes.

ALGORITHM determines which hashing algorithm will be used. It must be the value of one of the algorithm constants supplied by this module (see below). The AUTODIN-II CRC algorithm is currently unimplemented.

SALT must be an integer in the range [0, 2^16). It modifies the hashing so that the same password does not always produce the same hash.

USERNAME is a string that is used as more salt. In VMS it is the username of the account to which the password controls access.

In VMS, the USERNAME and PASSWORD strings are constrained to contain only uppercase letters, digits, "$" and "_". On input lowercase letters in username or password are folded to uppercase, and spaces in the password are removed. Furthermore, usernames can be at most 31 characters long, and passwords at most 32 characters long. This function does not perform case folding or space removal, or enforce any of these restrictions. If such restrictions are desired then they must be applied separately before passing checked strings to this function.

UAI_C_AD_II

UAI_C_PURDY

UAI_C_PURDY_V

UAI_C_PURDY_S

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

UAI_C_AD_II refers to an AUTODIN-II 32-bit CRC algorithm. This is unimplemented by this module.

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

SEE ALSO

VMS::User

AUTHOR

The original C implementation of LGI$HPWD was written by Shawn Clifford. The code has since been developed by Davide Casale, Mario Ambrogetti, Terence Lee, Jean-loup Gailly, Solar Designer, and Andrew Main (Zefram).

Mike McCauley <mikem@open.com.au> created the first version of Authen::DecHpwd, establishing the Perl interface. This was based on Shawn Clifford's code without the later developments.

Andrew Main (Zefram) <zefram@fysh.org> created a new Authen::DecHpwd based on the more developed C code presently used.

COPYRIGHT

Copyright (C) 2002 Jean-loup Gailly <http://gailly.net>

Based in part on code from John the Ripper, Copyright (C) 1996-2002 Solar Designer

Copyright (C) 2006 Andrew Main (Zefram) <zefram@fysh.org>

This module 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 2 of the License, or (at your option) any later version.