bionic (3) Authen::Passphrase::VMSPurdy.3pm.gz
NAME
Authen::Passphrase::VMSPurdy - passphrases with the VMS Purdy polynomial system
SYNOPSIS
use Authen::Passphrase::VMSPurdy;
$ppr = Authen::Passphrase::VMSPurdy->new(
username => "jrandom", salt => 25362,
hash_hex => "832a0c270179584a");
$ppr = Authen::Passphrase::VMSPurdy->new(
username => "jrandom", salt_random => 1,
passphrase => "passphrase");
$ppr = Authen::Passphrase::VMSPurdy->from_crypt(
'$VMS3$1263832A0C270179584AJRANDOM');
$ppr = Authen::Passphrase::VMSPurdy->from_rfc2307(
'{CRYPT}$VMS3$1263832A0C270179584AJRANDOM');
$algorithm = $ppr->algorithm;
$username = $ppr->username;
$salt = $ppr->salt;
$hash = $ppr->hash;
$hash_hex = $ppr->hash_hex;
if($ppr->match($passphrase)) { ...
$passwd = $ppr->as_crypt;
$userPassword = $ppr->as_rfc2307;
DESCRIPTION
An object of this class encapsulates a passphrase hashed using one of the Purdy polynomial hash functions
used in VMS. This is a subclass of Authen::Passphrase, and this document assumes that the reader is
familiar with the documentation for that class.
The core of the Purdy polynomial hashing algorithm transforms one 64-bit number into another 64-bit
number. It was developed by George B. Purdy, and described in the paper "A High Security Log-in
Procedure" which can be found at
<http://portal.acm.org/citation.cfm?id=361089&dl=GUIDE&coll=ACM&CFID=15151515&CFTOKEN=6184618>.
For practical use in passphrase hashing, the Purdy polynomial must be augmented by a procedure to turn a
variable-length passphrase into the initial 64-bit number to be hashed. In VMS this pre-hashing phase
also incorporates the username of the account to which access is being controlled, in order to prevent
identical passphrases yielding identical hashes. This is a form of salting. Another salt parameter, a
16-bit integer, is also included, this one going under the name "salt".
There are three variants of the pre-hashing algorithm. The original version, known as "PURDY" and used
during field testing of VMS 2.0, truncates or space-pads the username to a fixed length. The second
version, known as "PURDY_V" and used from VMS 2.0 up to (but not including) VMS 5.4, properly handles the
variable-length nature of the username. The third version, known as "PURDY_S" and used from VMS 5.4
onwards, performs some extra bit rotations to avoid aliasing problems when pre-hashing long strings. All
three versions are supported by this module.
VMS heavily restricts the composition of both usernames and passphrases. They may only contain
alphanumerics, "$", and "_". Case is insignificant. Usernames must be between 1 and 31 characters long,
and passphrases must be between 1 and 32 characters long. This module enforces these rules. An invalid
passphrase is never accepted as matching.
CONSTRUCTORS
Authen::Passphrase::VMSPurdy->new(ATTR => VALUE, ...)
Generates a new passphrase recogniser object using the VMS Purdy polynomial algorithm family. The
following attributes may be given:
algorithm
A string indicating which variant of the algorithm is to be used. Valid values are "PURDY" (the
original), "PURDY_V" (modified to use full length of the username), and "PURDY_S" (extra
rotations to avoid aliasing when processing long strings). Default "PURDY_S".
username
A string to be used as the `username' salt parameter. It is limited to VMS username syntax.
salt
The salt, as an integer in the range [0, 65536).
salt_hex
The salt, as a string of four hexadecimal digits. The first two digits must give the least-
significant byte and the last two give the most-significant byte, with most-significant nybble
first within each byte.
salt_random
Causes salt to be generated randomly. The value given for this attribute is ignored. The source
of randomness may be controlled by the facility described in Data::Entropy.
hash
The hash, as a string of eight bytes.
hash_hex
The hash, as a string of 16 hexadecimal digits.
passphrase
A passphrase that will be accepted. It is limited to VMS passphrase syntax.
The username and salt must be given, and either the hash or the passphrase.
Authen::Passphrase::VMSPurdy->from_crypt(PASSWD)
Generates a new passphrase recogniser object using the VMS Purdy polynomial algorithm family, from a
crypt string. The string must consist of an algorithm identifier, the salt in hexadecimal, the hash
in hexadecimal, then the username. The salt must be given as four hexadecimal digits, the first two
giving the least-significant byte and the last two giving the most-significant byte, with most-
significant nybble first within each byte. The algorithm identifier must be "$VMS1$" for "PURDY",
"$VMS2$" for "PURDY_V", or "$VMS3$" for "PURDY_S". The whole crypt string must be uppercase.
Authen::Passphrase::VMSPurdy->from_rfc2307(USERPASSWORD)
Generates a new passphrase recogniser object using the VMS Purdy polynomial algorithm family, from an
RFC 2307 string. The string must consist of "{CRYPT}" (case insensitive) followed by an acceptable
crypt string.
METHODS
$ppr->algorithm
Returns the algorithm variant identifier string. It may be "PURDY" (the original), "PURDY_V"
(modified to use full length of the username), and "PURDY_S" (extra rotations to avoid aliasing when
processing long strings).
$ppr->username
Returns the username string. All alphabetic characters in it are uppercase, which is the canonical
form.
$ppr->salt
Returns the salt, as an integer.
$ppr->salt_hex
Returns the salt, as a string of four hexadecimal digits. The first two digits give the least-
significant byte and the last two give the most-significant byte, with most-significant nybble first
within each byte.
$ppr->hash
Returns the hash value, as a string of eight bytes.
$ppr->hash_hex
Returns the hash value, as a string of 16 uppercase hexadecimal digits.
$ppr->match(PASSPHRASE)
$ppr->as_crypt
$ppr->as_rfc2307
These methods are part of the standard Authen::Passphrase interface.
SEE ALSO
Authen::DecHpwd, Authen::Passphrase
AUTHOR
Andrew Main (Zefram) <zefram@fysh.org>
COPYRIGHT
Copyright (C) 2006, 2007, 2009, 2010, 2012 Andrew Main (Zefram) <zefram@fysh.org>
LICENSE
This module is free software; you can redistribute it and/or modify it under the same terms as Perl
itself.