--- /dev/null
+#!/usr/bin/perl
+#
+# Password history via Heimdal external strength checking.
+#
+# This script is meant to be called via the Heimdal external password strength
+# checking interface and maintains per-user password history that also rejects
+# one-character permutations. Password history is stored as Crypt::PBKDF2
+# hashes with random salt for each password.
+#
+# Written by Russ Allbery <eagle@eyrie.org>
+# Copyright 2013, 2014
+# The Board of Trustees of the Leland Stanford Junior University
+
+##############################################################################
+# Declarations and configuration
+##############################################################################
+
+require 5.010;
+use autodie;
+use strict;
+use warnings;
+
+use DB_File::Lock;
+use Crypt::PBKDF2;
+use Fcntl qw(O_CREAT O_RDWR);
+use File::Basename qw(basename);
+use Getopt::Long::Descriptive qw(describe_options);
+use IPC::Run qw(run);
+use JSON qw(encode_json decode_json);
+use POSIX qw(setgid setuid);
+use Readonly;
+use Sys::Syslog qw(openlog syslog LOG_AUTH LOG_INFO LOG_WARNING);
+
+# The most convenient interface to Berkeley DB files is ties.
+## no critic (Miscellanea::ProhibitTies)
+
+# The number of PBKDF2 iterations to use when hashing passwords. This number
+# should be chosen so as to force the hash operation to take approximately 0.1
+# seconds on current hardware.
+Readonly my $HASH_ITERATIONS => 65536;
+
+# Path to the history database. Currently, this must be a Berkeley DB file in
+# the old DB_HASH format. Keys will be principal names, and values will be a
+# JSON array of hashes. Each hash will have two keys: timestamp, which holds
+# the seconds since UNIX epoch at which the history entry was stored, and
+# hash, which holds the Crypt::PBKDF2 LDAP-style password hash.
+Readonly my $HISTORY_PATH => '/var/lib/heimdal-history/history.db';
+
+# User and group used to do all password history lookups and writes, assuming
+# that this program is invoked as root and can therefore change UID and GID.
+Readonly my $HISTORY_USER => '_history';
+Readonly my $HISTORY_GROUP => '_history';
+
+# Path to the Berkeley DB file (DB_HASH format) that stores statistics on
+# password length of accepted passwords. Each successful password validation
+# will increase the counter for that length. This is read and written with
+# $HISTORY_USER and $HISTORY_GROUP.
+Readonly my $LENGTH_STATS_PATH => '/var/lib/heimdal-history/lengths.db';
+
+# The message to return to the user if we reject the password because it was
+# found in the user's history.
+Readonly my $REJECT_MESSAGE => 'password was previously used';
+
+# The path to the external strength checking program to run. This is done
+# first before checking history, and if it fails, that failure is returned as
+# the failure for this program.
+Readonly my $STRENGTH_PROGRAM => '/usr/bin/heimdal-strength';
+
+# User and group used to do password strength checking. Generally, this
+# doesn't require any privileges since the strength dictionary is
+# world-readable.
+Readonly my $STRENGTH_USER => 'nobody';
+Readonly my $STRENGTH_GROUP => 'nogroup';
+
+##############################################################################
+# Utility functions
+##############################################################################
+
+# Change real and effective UID and GID to those for the given user and group.
+# Does nothing if not running as root.
+#
+# $user - User to change the UID to
+# $group - Group to change the GID to (and clear all supplemental groups)
+#
+# Returns: undef
+# Throws: Text exception on any failure
+sub drop_privileges {
+ my ($user, $group) = @_;
+
+ # If running as root, drop privileges. Fail if we can't get the UID and
+ # GID corresponding to our users.
+ if ($> == 0 || $< == 0) {
+ my $uid = getpwnam($user)
+ or die "$0: cannot get UID for $user\n";
+ my $gid = getgrnam($group)
+ or die "$0: cannot get GID for $group\n";
+ setgid($gid) or die "$0: cannot setgid to $gid: $!\n";
+ setuid($uid) or die "$0: cannot setuid to $uid: $!\n";
+ if ($> == 0 || $< == 0) {
+ die "$0: failed to drop permissions\n";
+ }
+ }
+ return;
+}
+
+##############################################################################
+# Logging
+##############################################################################
+
+# Given a list of keys and values for a log message as a hash reference,
+# return in encoded format following our logging protocol. The log format is
+# a set of <key>=<value> parameters separated by a space. Values containing
+# whitespace are quoted with double quotes, with any internal double quotes
+# doubled.
+#
+# Here also is defined a custom sort order for the encoded key/value pairs to
+# keep them in a reasonable order for a human to read.
+#
+# $params_ref - Reference to a hash of key/value pairs
+#
+# Returns: The encoded format as a string
+sub encode_log_message {
+ my ($params_ref) = @_;
+
+ # Define the custom sort order for keys.
+ my $order = 1;
+ my %order
+ = map { $_ => $order++ } qw(action principal error result reason);
+
+ # Build the message from the parameters.
+ my $message;
+ for my $key (sort { $order{$a} <=> $order{$b} } keys %{$params_ref}) {
+ my $value = $params_ref->{$key};
+ $value =~ s{ \" }{\"\"}xmsg;
+ if ($value =~ m{ [ \"] }xms) {
+ $value = qq{"$value"};
+ }
+ $message .= qq{$key=$value };
+ }
+ chomp($message);
+ return $message;
+}
+
+# Log a non-fatal error encountered while trying to check or store password
+# history. This is used for errors where the password is accepted, but we ran
+# into some anomalous event such as corrupted history data that should be
+# drawn to the attention of an administrator. The log format is a set of
+# <key>=<value> parameters, with the following keys:
+#
+# - action: the action performed (currently always "check")
+# - principal: the principal to check a password for
+# - error: an error message explaining the anomalous situation
+#
+# Values containing whitespace are quoted with double quotes, with any
+# internal double quotes doubled.
+#
+# $principal - Principal for which we checked a password
+# $error - The error message
+#
+# Returns: undef
+sub log_error {
+ my ($principal, $error) = @_;
+ my $message = encode_log_message(
+ action => 'check',
+ principal => $principal,
+ error => $error,
+ );
+ syslog(LOG_WARNING, '%s', $message);
+ return;
+}
+
+# Log the disposition of a particular password strength checking request. All
+# log messages are logged through syslog at class info. The log format is a
+# set of <key>=<value> parameters, with the following keys:
+#
+# - action: the action performed (currently always "check")
+# - principal: the principal to check a password for
+# - result: either "accepted" or "rejected"
+# - reason: the reason for a rejection
+#
+# Values containing whitespace are quoted with double quotes, with any
+# internal double quotes doubled.
+#
+# $principal - Principal for which we checked a password
+# $result - "accepted" or "rejected" per above
+# $reason - On rejection, the reason
+#
+# Returns: undef
+sub log_result {
+ my ($principal, $result, $reason) = @_;
+
+ # Create the message.
+ my %message = (
+ action => 'check',
+ principal => $principal,
+ result => $result,
+ );
+ if ($result eq 'rejected' && defined($reason)) {
+ $message{reason} = $reason;
+ }
+ my $message = encode_log_message(\%message);
+
+ # Log the message.
+ syslog(LOG_INFO, '%s', $message);
+ return;
+}
+
+##############################################################################
+# Crypto
+##############################################################################
+
+# Given a password, return the hash for that password. Hashing is done with
+# PBKDF2 using SHA-2 as the underlying hash function. As of version 0.133330,
+# this uses SHA-256.
+#
+# $password - Password to hash
+#
+# Returns: Hash encoded in the LDAP-compatible Crypt::PBKDF2 format
+sub password_hash {
+ my ($password) = @_;
+ my $hasher = Crypt::PBKDF2->new(
+ hash_class => 'HMACSHA2',
+ iterations => $HASH_ITERATIONS,
+ );
+ return $hasher->generate($password);
+}
+
+# Given a password and the password history for the user as a reference to a
+# array, check whether that password is found in the history. The history
+# array is expected to contain anonymous hashes. The only key of interest is
+# the "hash" key, whose value is expected to be a hash in the LDAP-compatible
+# Crypt::PBKDF2 format.
+#
+# Invalid history entries are ignored for the purposes of this check and
+# treated as if the entry did not exist.
+#
+# $principal - Principal to check (solely for logging purposes)
+# $password - Password to check
+# $history_ref - Reference to array of anonymous hashes with "hash" keys
+#
+# Returns: True if the password matches one of the history hashes, false
+# otherwise
+sub is_in_history {
+ my ($principal, $password, $history_ref) = @_;
+ my $hasher = Crypt::PBKDF2->new(hash_class => 'HMACSHA2');
+
+ # Walk the history looking at each hash key.
+ for my $entry (@{$history_ref}) {
+ my $hash = $entry->{hash};
+ next if !defined($hash);
+
+ # validate throws an exception if the hash is in an invalid format.
+ # Treat that case the same as a miss, but log it.
+ if (eval { $hasher->validate($hash, $password) }) {
+ return 1;
+ } elsif ($@) {
+ log_error($principal, "hash validate failed: $@");
+ }
+ }
+
+ # No match.
+ return;
+}
+
+##############################################################################
+# Database
+##############################################################################
+
+# Given a principal and a password, determine whether the password was found
+# in the password history for that user.
+#
+# $path - Path to the history file
+# $principal - Principal for which to check history
+# $password - Check history for this password
+#
+# Returns: True if $password is found in history, false otherwise
+# Throws: On failure to open, lock, or tie the database
+sub check_history {
+ my ($path, $principal, $password) = @_;
+
+ # Open and lock the database and retrieve the history for the user.
+ # We have to lock for write so that we can create the database if it
+ # doesn't already exist. Password change should be infrequent enough
+ # and our window is fast enough that it shouldn't matter. We do this
+ # in a separate scope so that the history hash goes out of scope and
+ # is freed and unlocked.
+ my $history_json;
+ {
+ my %history;
+ my $mode = O_CREAT | O_RDWR;
+ tie(%history, 'DB_File::Lock', [$path, $mode, oct(600)], 'write')
+ or die "$0: cannot open $path: $!\n";
+ $history_json = $history{$principal};
+ }
+
+ # If there is no history for the user, return the trivial false.
+ if (!defined($history_json)) {
+ return;
+ }
+
+ # Decode history from JSON. If this fails (corrupt history), treat it as
+ # if the user has no history, but log the error message.
+ my $history_ref = eval { decode_json($history_json) };
+ if (!defined($history_ref)) {
+ log_error($principal, "history JSON decoding failed: $@");
+ return;
+ }
+
+ # Finally, check the password against the hashes in history.
+ return is_in_history($principal, $password, $history_ref);
+}
+
+# Write a new history entry to the database given the principal and the
+# password to record. History records are stored as JSON arrays of objects,
+# with keys "timestamp" and "hash".
+#
+# $path - Path to the history file
+# $principal - Principal for which to check history
+# $password - Check history for this password
+#
+# Returns: undef
+# Throws: On failure to open, lock, or tie the database
+sub write_history {
+ my ($path, $principal, $password) = @_;
+
+ # Open and lock the database for write.
+ my %history;
+ my $mode = O_CREAT | O_RDWR;
+ tie(%history, 'DB_File::Lock', [$path, $mode, oct(600)], 'write')
+ or die "$0: cannot open $path: $!\n";
+
+ # Read the existing history. If the existing history is corrupt, treat
+ # that as equivalent to not having any history, but log an error.
+ my $history_json = $history{$principal};
+ my $history_ref;
+ if (defined($history_json)) {
+ $history_ref = eval { decode_json($history_json) };
+ if ($@) {
+ log_error($principal, "history JSON decoding failed: $@");
+ }
+ }
+ if (!defined($history_ref)) {
+ $history_ref = [];
+ }
+
+ # Add a new history entry.
+ my $entry = { timestamp => time(), hash => password_hash($password) };
+ unshift(@{$history_ref}, $entry);
+
+ # Store the encoded data back in the history database.
+ $history{$principal} = encode_json($history_ref);
+
+ # The database is closed and unlocked when %history goes out of scope.
+ # Unfortunately, we lose on error detection here, since there doesn't
+ # appear to be a way to determine whether all the writes succeeded. But
+ # losing a bit of history in the rare error case of failing to write to
+ # local disk is probably not a big deal.
+ return;
+}
+
+# Write statistics about password length. Given the length of the password
+# and the path to the length statistics database, increments the counter for
+# that password length.
+#
+# Any failure to open or write to the database is ignored, since this is
+# considered optional logging and should not block the password change.
+#
+# $path - Path to the length statistics file
+# $length - Length of the accepted password
+#
+# Returns: undef
+sub update_length_counts {
+ my ($path, $length) = @_;
+
+ # Open and lock the database for write.
+ my %lengths;
+ my $mode = O_CREAT | O_RDWR;
+ tie(%lengths, 'DB_File::Lock', [$path, $mode, oct(600)], 'write')
+ or return;
+
+ # Write each of the hashes.
+ $lengths{$length}++;
+
+ # The database is closed and unlocked when %lengths goes out of scope.
+ return;
+}
+
+##############################################################################
+# Heimdal password strength protocol
+##############################################################################
+
+# Run another external password strength checker and return the results. This
+# allows us to chain to another program that handles the actual strength
+# checking prior to handling history.
+#
+# $principal - Principal attempting to change their password
+# $password - The new password
+#
+# Returns: Scalar context: true if the password was accepted, false otherwise
+# List context: whether the password is okay, the exit status of the
+# strength checking program, and the error message if the first
+# element is false
+# Throws: Text exception on failure to execute the program, or read or write
+# from it or to it, or if it fails without an error
+sub strength_check {
+ my ($principal, $password) = @_;
+
+ # Run the external strength checking program. If we're root, we'll run it
+ # as the strength checking user and group.
+ my $in = "principal: $principal\nnew-password: $password\nend\n";
+ my $init = sub { drop_privileges($STRENGTH_USER, $STRENGTH_GROUP) };
+ my ($out, $err);
+ run([$STRENGTH_PROGRAM, $principal], \$in, \$out, \$err, init => $init);
+ my $status = ($? >> 8);
+
+ # Check the results.
+ my $okay = ($status == 0 && $out eq "APPROVED\n");
+
+ # If the program failed, collect the error message.
+ if (!$okay) {
+ if ($err) {
+ $err =~ s{ \n .* }{}xms;
+ } else {
+ die "$0: password strength checking failed without an error\n";
+ }
+ }
+
+ # Return the results.
+ return wantarray ? ($okay, $err, $status) : $okay;
+}
+
+# Read a Heimdal external password strength checking request from the provided
+# file handle and return the principal (ignored for our application) and the
+# password.
+#
+# The protocol expects the following data (without leading whitespace) on
+# standard input, in precisely this order:
+#
+# principal: <principal>
+# new-password: <password>
+# end
+#
+# There is one and only one space after the colon, and any subsequent spaces
+# are part of the value (such as leading spaces in the password).
+#
+# $fh - File handle from which to read
+#
+# Returns: Scalar context: the password
+# List context: a list of the password and the principal
+# Throws: Text exception on any protocol violations or IO errors
+sub read_change_data {
+ my ($fh) = @_;
+ my @keys = qw(principal new-password);
+ my %data;
+
+ # Read the data elements we expect. Verify that they come in the correct
+ # order and the correct format.
+ local $/ = "\n";
+ for my $key (@keys) {
+ my $line = readline($fh);
+ if (!defined($line)) {
+ die "$0: truncated input before $key: $!\n";
+ }
+ chomp($line);
+ if ($line =~ s{ \A \Q$key\E : [ ] }{}xms) {
+ $data{$key} = $line;
+ } else {
+ die "$0: unrecognized input line before $key\n";
+ }
+ }
+
+ # The final line of input must be a literal "end\n";
+ my $line = readline($fh);
+ if (!defined($line)) {
+ die "$0: truncated input before end: $!\n";
+ } elsif ($line ne "end\n") {
+ die "$0: unrecognized input line before end\n";
+ }
+
+ # Return the results.
+ my $password = $data{'new-password'};
+ my $principal = $data{principal};
+ return wantarray ? ($password, $principal) : $password;
+}
+
+##############################################################################
+# Main routine
+##############################################################################
+
+# Always flush output.
+STDOUT->autoflush;
+
+# Clean up the script name for error reporting.
+my $fullpath = $0;
+local $0 = basename($0);
+
+# Parse the argument list.
+my ($opt, $usage) = describe_options(
+ '%c %o',
+ ['database|d=s', 'Path to the history database, overriding the default'],
+ ['help|h', 'Print usage message and exit'],
+ ['manual|man|m', 'Print full manual and exit'],
+ ['stats|S=s', 'Path to hash of length statistics'],
+ ['strength|s=s', 'Path to strength checking program to run'],
+);
+if ($opt->help) {
+ print {*STDOUT} $usage->text
+ or die "$0: cannot write to standard output: $!\n";
+ exit(0);
+} elsif ($opt->manual) {
+ say {*STDOUT} 'Feeding myself to perldoc, please wait...'
+ or die "$0: cannot write to standard output: $!\n";
+ exec('perldoc', '-t', $fullpath);
+}
+my $database = $opt->database || $HISTORY_PATH;
+my $stats_db = $opt->stats || $LENGTH_STATS_PATH;
+
+# Open syslog for result reporting.
+openlog($0, 'pid', LOG_AUTH);
+
+# Read the principal and password that we're supposed to check.
+my ($password, $principal) = read_change_data(\*STDIN);
+
+# Delegate to the external strength checking program.
+my ($okay, $error, $status) = strength_check($principal, $password);
+if (!$okay) {
+ log_result($principal, 'rejected', $error);
+ warn "$error\n";
+ exit($status);
+}
+
+# Drop privileges for the rest of the program.
+drop_privileges($HISTORY_USER, $HISTORY_GROUP);
+
+# Hash the password and check history. Exit if a hash is in history.
+if (check_history($database, $principal, $password)) {
+ log_result($principal, 'rejected', $REJECT_MESSAGE);
+ warn "$REJECT_MESSAGE\n";
+ exit(0);
+}
+
+# The password is accepted. Record it, update the length counter, and return
+# success.
+log_result($principal, 'accepted');
+write_history($database, $principal, $password);
+say {*STDOUT} 'APPROVED'
+ or die "$0: cannot write to standard output: $!\n";
+update_length_counts($stats_db, length($password));
+exit(0);
+
+__END__
+
+##############################################################################
+# Documentation
+##############################################################################
+
+=for stopwords
+heimdal-history heimdal-strength Heimdal -hm BerkeleyDB timestamps POSIX
+whitespace API Allbery sublicense MERCHANTABILITY NONINFRINGEMENT syslog
+pseudorandom JSON LDAP-compatible PBKDF2 SHA-256
+
+=head1 NAME
+
+heimdal-history - Password history via Heimdal external strength checking
+
+=head1 SYNOPSIS
+
+B<heimdal-history> [B<-hm>] [B<-d> I<database>] [B<-S> I<length-stats-db>]
+ [B<-s> I<strength-program>] [B<principal>]
+
+=head1 DESCRIPTION
+
+B<heimdal-history> is an implementation of password history via the
+Heimdal external password strength checking interface. It stores separate
+history for each principal, hashed using Crypt::PBKDF2 with
+randomly-generated salt. (The randomness is from a weak pseudorandom
+number generator, not strongly random.)
+
+Password history is stored in a BerkeleyDB DB_HASH file. The key is the
+principal. The value is a JSON array of objects, each of which has two
+keys. C<timestamp> contains the time when the history entry was added (in
+POSIX seconds since UNIX epoch), and C<hash> contains the hash of a
+previously-used password in the Crypt::PBKDF2 LDAP-compatible format.
+Passwords are hashed using PBKDF2 (from PKCS#5) with SHA-256 as the
+underlying hash function using a number of rounds configured in this
+script. See L<Crypt::PBKDF2> for more information.
+
+B<heimdal-history> also checks password strength before checking history.
+It does so by invoking another program that also uses the Heimdal external
+password strength checking interface. By default, it runs
+B</usr/bin/heimdal-strength>. Only if that program approves the password
+does it hash it and check history.
+
+As with any implementation of the Heimdal external password strength
+checking protocol, B<heimdal-history> expects, on standard input:
+
+ principal: <principal>
+ new-password: <password>
+ end
+
+(with no leading whitespace). <principal> is the principal changing its
+password (passed to the other password strength checking program but
+otherwise unused here), and <password> is the new password. There must
+be exactly one space after the colon. Any subsequent spaces are taken to
+be part of the principal or password.
+
+If invoked as root, B<heimdal-history> will run the external strength
+checking program as user C<nobody> and group C<nogroup>, and will check
+and write to the history database as user C<_history> and group
+C<_history>. These users must exist on the system if it is run as root.
+
+The result of each password check will be logged to syslog (priority
+LOG_INFO, facility LOG_AUTH). Each log line will be a set of key/value
+pairs in the format C<< I<key>=I<value> >>. The keys are:
+
+=over 4
+
+=item action
+
+The action performed (currently always C<check>).
+
+=item principal
+
+The principal for which a password was checked.
+
+=item error
+
+An internal error message that did not stop the history check, but which
+may indicate that something is wrong with the history database (such as
+corrupted entries or invalid hashes). If this key is present, neither
+C<result> nor C<reason> will be present. There will be a subsequent log
+message from the same invocation giving the final result of the history
+check (assuming B<heimdal-history> doesn't exit with a fatal error).
+
+=item result
+
+Either C<accepted> or C<rejected>.
+
+=item reason
+
+If the password was rejected, the reason for the rejection.
+
+=back
+
+The value will be surrounded with double quotes if it contains a double
+quote or space. Any double quotes in the value will be doubled, so C<">
+becomes C<"">.
+
+=head1 OPTIONS
+
+=over 4
+
+=item B<-d> I<database>, B<--database>=I<database>
+
+Use I<database> as the history database file instead of the default
+(F</var/lib/heimdal-history/history.db>). Primarily used for testing,
+since Heimdal won't pass this argument.
+
+=item B<-h>, B<--help>
+
+Print a short usage message and exit.
+
+=item B<-m>, B<--manual>, B<--man>
+
+Display this manual and exit.
+
+=item B<-S> I<length-stats-db>, B<--stats>=I<length-stats-db>
+
+Use I<length-stats-db> as the database file for password length statistics
+instead of the default (F</var/lib/heimdal-history/lengths.db>).
+Primarily used for testing, since Heimdal won't pass this argument.
+
+=item B<-s> I<strength-program>, B<--strength>=I<strength-program>
+
+Run I<strength-program> as the external strength-checking program instead
+of the default (F</usr/bin/heimdal-strength>). Primarily used for
+testing, since Heimdal won't pass this argument.
+
+=back
+
+=head1 RETURN STATUS
+
+On approval of the password, B<heimdal-history> will print C<APPROVED> and
+a newline to standard output and exit with status 0.
+
+If the password is rejected by the strength checking program or if it (or
+a version with a single character removed) matches one of the hashes stored
+in the password history, B<heimdal-history> will print the reason for
+rejection to standard error and exit with status 0.
+
+On any internal error, B<heimdal-history> will print the error to standard
+error and exit with a non-zero status.
+
+=head1 FILES
+
+=over 4
+
+=item F</usr/bin/heimdal-strength>
+
+The default password strength checking program. This program must follow
+the Heimdal external password strength checking API.
+
+=item F</var/lib/heimdal-history/history.db>
+
+The default database path. If B<heimdal-strength> is run as root, this
+file needs to be readable and writable by user C<_history> and group
+C<_history>. If it doesn't exist, it will be created with mode 0600.
+
+=item F</var/lib/heimdal-history/history.db.lock>
+
+The lock file used to synchronize access to the history database. As with
+the history database, if B<heimdal-strength> is run as root, this file
+needs to be readable and writable by user C<_history> and group
+C<_history>.
+
+=item F</var/lib/heimdal-history/lengths.db>
+
+The default length statistics path, which will be a BerkeleyDB DB_HASH
+file of password lengths to counts of passwords with that length. If
+B<heimdal-strength> is run as root, this file needs to be readable and
+writable by user C<_history> and group C<_history>. If it doesn't exist,
+it will be created with mode 0600.
+
+=item F</var/lib/heimdal-history/lengths.db.lock>
+
+The lock file used to synchronize access to the length statistics
+database. As with the length statistics database, if B<heimdal-strength>
+is run as root, this file needs to be readable and writable by user
+C<_history> and group C<_history>.
+
+=back
+
+=head1 AUTHOR
+
+Russ Allbery <eagle@eyrie.org>
+
+=head1 COPYRIGHT AND LICENSE
+
+Copyright 2013, 2014 The Board of Trustees of the Leland Stanford Junior
+University
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
+=head1 SEE ALSO
+
+L<Crypt::PBKDF2>, L<heimdal-strength(1)>
+
+=cut
projects / kerberos / krb5-strength.git / commitdiff