3 # Password history via Heimdal external strength checking.
5 # This script is meant to be called via the Heimdal external password strength
6 # checking interface and maintains per-user password history. Password
7 # history is stored as Crypt::PBKDF2 hashes with random salt for each
10 ##############################################################################
11 # Declarations and configuration
12 ##############################################################################
20 use Const::Fast qw(const);
22 use Fcntl qw(O_CREAT O_RDWR);
23 use File::Basename qw(basename);
24 use Getopt::Long::Descriptive qw(describe_options);
26 use JSON::MaybeXS qw(encode_json decode_json);
27 use POSIX qw(setgid setuid);
28 use Sys::Syslog qw(openlog syslog LOG_AUTH LOG_INFO LOG_WARNING);
30 # The most convenient interface to Berkeley DB files is ties.
31 ## no critic (Miscellanea::ProhibitTies)
33 # The number of PBKDF2 iterations to use when hashing passwords. This number
34 # should be chosen so as to force the hash operation to take approximately 0.1
35 # seconds on current hardware.
36 const my $HASH_ITERATIONS => 45144;
38 # Path to the history database. Currently, this must be a Berkeley DB file in
39 # the old DB_HASH format. Keys will be principal names, and values will be a
40 # JSON array of hashes. Each hash will have two keys: timestamp, which holds
41 # the seconds since UNIX epoch at which the history entry was stored, and
42 # hash, which holds the Crypt::PBKDF2 LDAP-style password hash.
43 const my $HISTORY_PATH => '/var/lib/heimdal-history/history.db';
45 # User and group used to do all password history lookups and writes, assuming
46 # that this program is invoked as root and can therefore change UID and GID.
47 const my $HISTORY_USER => '_history';
48 const my $HISTORY_GROUP => '_history';
50 # Path to the Berkeley DB file (DB_HASH format) that stores statistics on
51 # password length of accepted passwords. Each successful password validation
52 # will increase the counter for that length. This is read and written with
53 # $HISTORY_USER and $HISTORY_GROUP.
54 const my $LENGTH_STATS_PATH => '/var/lib/heimdal-history/lengths.db';
56 # The message to return to the user if we reject the password because it was
57 # found in the user's history.
58 const my $REJECT_MESSAGE => 'Password was previously used';
60 # The path to the external strength checking program to run. This is done
61 # first before checking history, and if it fails, that failure is returned as
62 # the failure for this program.
63 const my $STRENGTH_PROGRAM => '/usr/bin/heimdal-strength';
65 # User and group used to do password strength checking. Generally, this
66 # doesn't require any privileges since the strength dictionary is
68 const my $STRENGTH_USER => 'nobody';
69 const my $STRENGTH_GROUP => 'nogroup';
71 # Global boolean variable saying whether to log with syslog. This is set
72 # based on the presence of the -q (--quiet) command-line option.
75 ##############################################################################
77 ##############################################################################
79 # Change real and effective UID and GID to those for the given user and group.
80 # Does nothing if not running as root.
82 # $user - User to change the UID to
83 # $group - Group to change the GID to (and clear all supplemental groups)
86 # Throws: Text exception on any failure
88 my ($user, $group) = @_;
90 # If running as root, drop privileges. Fail if we can't get the UID and
91 # GID corresponding to our users.
92 if ($> == 0 || $< == 0) {
93 my $uid = getpwnam($user)
94 or die "$0: cannot get UID for $user\n";
95 my $gid = getgrnam($group)
96 or die "$0: cannot get GID for $group\n";
97 setgid($gid) or die "$0: cannot setgid to $gid: $!\n";
98 setuid($uid) or die "$0: cannot setuid to $uid: $!\n";
99 if ($> == 0 || $< == 0) {
100 die "$0: failed to drop permissions\n";
106 ##############################################################################
108 ##############################################################################
110 # Given a list of keys and values for a log message as a hash reference,
111 # return in encoded format following our logging protocol. The log format is
112 # a set of <key>=<value> parameters separated by a space. Values containing
113 # whitespace are quoted with double quotes, with any internal double quotes
116 # Here also is defined a custom sort order for the encoded key/value pairs to
117 # keep them in a reasonable order for a human to read.
119 # $params_ref - Reference to a hash of key/value pairs
121 # Returns: The encoded format as a string
122 sub encode_log_message {
123 my ($params_ref) = @_;
125 # Define the custom sort order for keys.
128 = map { $_ => $order++ } qw(action principal error result reason);
130 # Build the message from the parameters.
132 for my $key (sort { $order{$a} <=> $order{$b} } keys %{$params_ref}) {
133 my $value = $params_ref->{$key};
134 $value =~ s{ \" }{\"\"}xmsg;
135 if ($value =~ m{ [ \"] }xms) {
136 $value = qq{"$value"};
138 $message .= qq{$key=$value };
144 # Log a non-fatal error encountered while trying to check or store password
145 # history. This is used for errors where the password is accepted, but we ran
146 # into some anomalous event such as corrupted history data that should be
147 # drawn to the attention of an administrator. The log format is a set of
148 # <key>=<value> parameters, with the following keys:
150 # - action: the action performed (currently always "check")
151 # - principal: the principal to check a password for
152 # - error: an error message explaining the anomalous situation
154 # Values containing whitespace are quoted with double quotes, with any
155 # internal double quotes doubled. No logging will be done if $SYSLOG is
158 # $principal - Principal for which we checked a password
159 # $error - The error message
163 my ($principal, $error) = @_;
167 my $message = encode_log_message(
169 principal => $principal,
172 syslog(LOG_WARNING, '%s', $message);
176 # Log the disposition of a particular password strength checking request. All
177 # log messages are logged through syslog at class info. The log format is a
178 # set of <key>=<value> parameters, with the following keys:
180 # - action: the action performed (currently always "check")
181 # - principal: the principal to check a password for
182 # - result: either "accepted" or "rejected"
183 # - reason: the reason for a rejection
185 # Values containing whitespace are quoted with double quotes, with any
186 # internal double quotes doubled. No logging will be done if $SYSLOG is
189 # $principal - Principal for which we checked a password
190 # $result - "accepted" or "rejected" per above
191 # $reason - On rejection, the reason
195 my ($principal, $result, $reason) = @_;
200 # Create the message.
203 principal => $principal,
206 if ($result eq 'rejected' && defined($reason)) {
207 $message{reason} = $reason;
209 my $message = encode_log_message(\%message);
212 syslog(LOG_INFO, '%s', $message);
216 ##############################################################################
218 ##############################################################################
220 # Given a password, return the hash for that password. Hashing is done with
221 # PBKDF2 using SHA-2 as the underlying hash function. As of version 0.133330,
224 # $password - Password to hash
225 # $iterations - Optional iteration count, defaulting to $HASH_ITERATIONS
227 # Returns: Hash encoded in the LDAP-compatible Crypt::PBKDF2 format
229 my ($password, $iterations) = @_;
230 $iterations //= $HASH_ITERATIONS;
231 my $hasher = Crypt::PBKDF2->new(
232 hash_class => 'HMACSHA2',
233 iterations => $iterations,
235 return $hasher->generate($password);
238 # Given a password and the password history for the user as a reference to a
239 # array, check whether that password is found in the history. The history
240 # array is expected to contain anonymous hashes. The only key of interest is
241 # the "hash" key, whose value is expected to be a hash in the LDAP-compatible
242 # Crypt::PBKDF2 format.
244 # Invalid history entries are ignored for the purposes of this check and
245 # treated as if the entry did not exist.
247 # $principal - Principal to check (solely for logging purposes)
248 # $password - Password to check
249 # $history_ref - Reference to array of anonymous hashes with "hash" keys
251 # Returns: True if the password matches one of the history hashes, false
254 my ($principal, $password, $history_ref) = @_;
255 my $hasher = Crypt::PBKDF2->new(hash_class => 'HMACSHA2');
257 # Walk the history looking at each hash key.
258 for my $entry (@{$history_ref}) {
259 my $hash = $entry->{hash};
260 next if !defined($hash);
262 # validate throws an exception if the hash is in an invalid format.
263 # Treat that case the same as a miss, but log it.
264 if (eval { $hasher->validate($hash, $password) }) {
267 log_error($principal, "hash validate failed: $@");
275 ##############################################################################
277 ##############################################################################
279 # Perform a binary search for a number of hash iterations that makes password
280 # hashing take the given target time on the current system.
284 # * The system load is low enough that this benchmark result is meaningful
285 # and not heavily influenced by other programs running on the system. The
286 # binary search may be unstable if the system load is too variable.
288 # * The static "password" string used for benchmarking will exhibit similar
289 # performance to the statistically average password.
291 # Information about the iteration search process is printed to standard output
292 # while the search runs.
294 # $target - The elapsed time, in real seconds, we're aiming for
295 # $delta - The permissible delta around the target time
297 # Returns: The number of hash iterations with that performance characteristic
298 # Throws: Text exception on failure to write to standard output
299 sub find_iteration_count {
300 my ($target, $delta) = @_;
304 # A static password to use for benchmarking.
305 my $password = 'this is a benchmark';
307 # Start at the current configured iteration count. If this doesn't take
308 # long enough, it becomes the new low mark and we try double that
309 # iteration count. Otherwise, do binary search.
311 # We time twenty iterations each time, chosen because it avoids the
312 # warnings from Benchmark about too few iterations for a reliable count.
314 my $iterations = $HASH_ITERATIONS;
316 my $hash = sub { password_hash($password, $iterations) };
317 my $times = Benchmark::timethis(20, $hash, q{}, 'none');
319 # Extract the CPU time from the formatted time string. This will be
320 # the total time for all of the iterations, so divide by the iteration
321 # count to recover the time per iteration.
322 my $report = Benchmark::timestr($times);
323 my ($time) = ($report =~ m{ ([\d.]+) [ ] CPU }xms);
326 # Tell the user what we discovered.
327 say {*STDOUT} "Performing $iterations iterations takes $time seconds"
328 or die "$0: cannot write to standard output: $!\n";
330 # If this is what we're looking for, we're done.
331 if (abs($time - $target) < $delta) {
335 # Determine the new iteration target.
336 if ($time > $target) {
341 if ($time < $target && $high == 0) {
342 $iterations = $iterations * 2;
344 $iterations = int(($high + $low) / 2);
348 # Report the result and return it.
349 say {*STDOUT} "Use $iterations iterations"
350 or die "$0: cannot write to standard output: $!\n";
354 ##############################################################################
356 ##############################################################################
358 # Given a principal and a password, determine whether the password was found
359 # in the password history for that user.
361 # $path - Path to the history file
362 # $principal - Principal for which to check history
363 # $password - Check history for this password
365 # Returns: True if $password is found in history, false otherwise
366 # Throws: On failure to open, lock, or tie the database
368 my ($path, $principal, $password) = @_;
370 # Open and lock the database and retrieve the history for the user.
371 # We have to lock for write so that we can create the database if it
372 # doesn't already exist. Password change should be infrequent enough
373 # and our window is fast enough that it shouldn't matter. We do this
374 # in a separate scope so that the history hash goes out of scope and
375 # is freed and unlocked.
379 my $mode = O_CREAT | O_RDWR;
381 %history, 'DB_File::Lock', $path, $mode, oct(600), $DB_HASH,
383 ) or die "$0: cannot open $path: $!\n";
384 $history_json = $history{$principal};
387 # If there is no history for the user, return the trivial false.
388 if (!defined($history_json)) {
392 # Decode history from JSON. If this fails (corrupt history), treat it as
393 # if the user has no history, but log the error message.
394 my $history_ref = eval { decode_json($history_json) };
395 if (!defined($history_ref)) {
396 log_error($principal, "history JSON decoding failed: $@");
400 # Finally, check the password against the hashes in history.
401 return is_in_history($principal, $password, $history_ref);
404 # Write a new history entry to the database given the principal and the
405 # password to record. History records are stored as JSON arrays of objects,
406 # with keys "timestamp" and "hash".
408 # $path - Path to the history file
409 # $principal - Principal for which to check history
410 # $password - Check history for this password
413 # Throws: On failure to open, lock, or tie the database
415 my ($path, $principal, $password) = @_;
417 # Open and lock the database for write.
419 my $mode = O_CREAT | O_RDWR;
420 tie(%history, 'DB_File::Lock', $path, $mode, oct(600), $DB_HASH, 'write')
421 or die "$0: cannot open $path: $!\n";
423 # Read the existing history. If the existing history is corrupt, treat
424 # that as equivalent to not having any history, but log an error.
425 my $history_json = $history{$principal};
427 if (defined($history_json)) {
428 $history_ref = eval { decode_json($history_json) };
430 log_error($principal, "history JSON decoding failed: $@");
433 if (!defined($history_ref)) {
437 # Add a new history entry.
438 my $entry = { timestamp => time(), hash => password_hash($password) };
439 unshift(@{$history_ref}, $entry);
441 # Store the encoded data back in the history database.
442 $history{$principal} = encode_json($history_ref);
444 # The database is closed and unlocked when %history goes out of scope.
445 # Unfortunately, we lose on error detection here, since there doesn't
446 # appear to be a way to determine whether all the writes succeeded. But
447 # losing a bit of history in the rare error case of failing to write to
448 # local disk is probably not a big deal.
452 # Write statistics about password length. Given the length of the password
453 # and the path to the length statistics database, increments the counter for
454 # that password length.
456 # Any failure to open or write to the database is ignored, since this is
457 # considered optional logging and should not block the password change.
459 # $path - Path to the length statistics file
460 # $length - Length of the accepted password
463 sub update_length_counts {
464 my ($path, $length) = @_;
466 # Open and lock the database for write.
468 my $mode = O_CREAT | O_RDWR;
469 tie(%lengths, 'DB_File::Lock', $path, $mode, oct(600), $DB_HASH, 'write')
472 # Write each of the hashes.
475 # The database is closed and unlocked when %lengths goes out of scope.
479 ##############################################################################
480 # Heimdal password quality protocol
481 ##############################################################################
483 # Run another external password quality checker and return the results. This
484 # allows us to chain to another program that handles the actual strength
485 # checking prior to handling history.
487 # $path - Password quality check program to run
488 # $principal - Principal attempting to change their password
489 # $password - The new password
491 # Returns: A list of three elements:
492 # - whether the password is okay
493 # - the exit status of the quality checking program
494 # - the error message if the first element is false
495 # Throws: Text exception on failure to execute the program, or read or
496 # write from it or to it, or if it fails without an error
498 my ($path, $principal, $password) = @_;
500 # Run the external quality checking program. If we're root, we'll run it
501 # as the strength checking user and group.
502 my $in = "principal: $principal\nnew-password: $password\nend\n";
503 my $init = sub { drop_privileges($STRENGTH_USER, $STRENGTH_GROUP) };
505 run([$path, $principal], \$in, \$out, \$err, init => $init);
506 my $status = ($? >> 8);
509 my $okay = ($status == 0 && $out eq "APPROVED\n");
511 # If the program failed, collect the error message.
514 $err =~ s{ \n .* }{}xms;
516 die "$0: password strength checking failed without an error\n";
520 # Return the results.
521 return ($okay, $err, $status);
524 # Read a Heimdal external password quality checking request from the provided
525 # file handle and return the principal (ignored for our application) and the
528 # The protocol expects the following data (without leading whitespace) on
529 # standard input, in precisely this order:
531 # principal: <principal>
532 # new-password: <password>
535 # There is one and only one space after the colon, and any subsequent spaces
536 # are part of the value (such as leading spaces in the password).
538 # $fh - File handle from which to read
540 # Returns: List of the password and the principal
541 # Throws: Text exception on any protocol violations or IO errors
542 sub read_change_data {
544 my @keys = qw(principal new-password);
547 # Read the data elements we expect. Verify that they come in the correct
548 # order and the correct format.
550 for my $key (@keys) {
551 my $line = readline($fh);
552 if (!defined($line)) {
553 die "$0: truncated input before $key: $!\n";
556 if ($line =~ s{ \A \Q$key\E : [ ] }{}xms) {
559 die "$0: unrecognized input line before $key\n";
563 # The final line of input must be a literal "end\n";
564 my $line = readline($fh);
565 if (!defined($line)) {
566 die "$0: truncated input before end: $!\n";
567 } elsif ($line ne "end\n") {
568 die "$0: unrecognized input line before end\n";
571 # Return the results.
572 return ($data{'new-password'}, $data{principal});
575 ##############################################################################
577 ##############################################################################
579 # Always flush output.
582 # Clean up the script name for error reporting.
584 local $0 = basename($0);
586 # Parse the argument list.
588 my ($opt, $usage) = describe_options(
590 ['benchmark|b=f', 'Benchmark hash iterations for this target time'],
591 ['check-only|c', 'Check password history without updating database'],
592 ['database|d=s', 'Path to the history database, overriding the default'],
593 ['help|h', 'Print usage message and exit'],
594 ['manual|man|m', 'Print full manual and exit'],
595 ['quiet|q', 'Suppress logging to syslog'],
596 ['stats|S=s', 'Path to database of length statistics'],
597 ['strength|s=s', 'Path to strength checking program to run'],
601 print {*STDOUT} $usage->text
602 or die "$0: cannot write to standard output: $!\n";
604 } elsif ($opt->manual) {
605 say {*STDOUT} 'Feeding myself to perldoc, please wait...'
606 or die "$0: cannot write to standard output: $!\n";
607 exec('perldoc', '-t', $fullpath);
609 my $database = $opt->database || $HISTORY_PATH;
610 my $stats_db = $opt->stats || $LENGTH_STATS_PATH;
611 my $strength = $opt->strength || $STRENGTH_PROGRAM;
613 # If asked to do benchmarking, ignore other arguments and just do that.
614 # Currently, we hard-code a 0.005-second granularity on our binary search.
615 if ($opt->benchmark) {
616 find_iteration_count($opt->benchmark, 0.005);
620 # Open syslog for result reporting.
624 openlog($0, 'pid', LOG_AUTH);
627 # Read the principal and password that we're supposed to check.
628 my ($password, $principal) = read_change_data(\*STDIN);
630 # Delegate to the external strength checking program.
631 my ($okay, $error, $status) = strength_check($strength, $principal, $password);
633 log_result($principal, 'rejected', $error);
638 # Drop privileges for the rest of the program.
639 drop_privileges($HISTORY_USER, $HISTORY_GROUP);
641 # Hash the password and check history. Exit if a hash is in history.
642 if (check_history($database, $principal, $password)) {
643 log_result($principal, 'rejected', $REJECT_MESSAGE);
644 warn "$REJECT_MESSAGE\n";
648 # The password is accepted. Record it, update the length counter, and return
650 log_result($principal, 'accepted');
651 if (!$opt->check_only) {
652 write_history($database, $principal, $password);
653 update_length_counts($stats_db, length($password));
655 say {*STDOUT} 'APPROVED'
656 or die "$0: cannot write to standard output: $!\n";
661 ##############################################################################
663 ##############################################################################
666 heimdal-history heimdal-strength Heimdal -chmq BerkeleyDB timestamps POSIX
667 whitespace API Allbery sublicense MERCHANTABILITY NONINFRINGEMENT syslog
668 pseudorandom JSON LDAP-compatible PBKDF2 SHA-256 KDC SPDX-License-Identifier
673 heimdal-history - Password history via Heimdal external strength checking
677 B<heimdal-history> [B<-chmq>] [B<-b> I<target-time>] [B<-d> I<database>]
678 [B<-S> I<length-stats-db>] [B<-s> I<strength-program>] [B<principal>]
682 B<heimdal-history> is an implementation of password history via the Heimdal
683 external password strength checking interface. It stores separate history for
684 each principal, hashed using Crypt::PBKDF2 with randomly-generated salt. (The
685 randomness is from a weak pseudorandom number generator, not strongly random.)
686 Password history is stored indefinitely (implementing infinite history); older
687 password hashes are never removed by this program.
689 Password history is stored in a BerkeleyDB DB_HASH file. The key is the
690 principal. The value is a JSON array of objects, each of which has two keys.
691 C<timestamp> contains the time when the history entry was added (in POSIX
692 seconds since UNIX epoch), and C<hash> contains the hash of a previously-used
693 password in the Crypt::PBKDF2 LDAP-compatible format. Passwords are hashed
694 using PBKDF2 (from PKCS#5) with SHA-256 as the underlying hash function using
695 a number of rounds configured in this script. See L<Crypt::PBKDF2> for more
698 B<heimdal-history> also checks password strength before checking history. It
699 does so by invoking another program that also uses the Heimdal external
700 password strength checking interface. By default, it runs
701 B</usr/bin/heimdal-strength>. Only if that program approves the password does
702 it hash it and check history.
704 For more information on how to set up password history, see L</CONFIGURATION>
707 As with any implementation of the Heimdal external password strength checking
708 protocol, B<heimdal-history> expects, on standard input:
710 principal: <principal>
711 new-password: <password>
714 (with no leading whitespace). <principal> is the principal changing its
715 password (passed to the other password strength checking program but otherwise
716 unused here), and <password> is the new password. There must be exactly one
717 space after the colon. Any subsequent spaces are taken to be part of the
718 principal or password.
720 If the password is accepted, B<heimdal-history> will assume that it will be
721 used and will update the history database to record the new password. It will
722 also update the password length statistics database to account for the new
725 If invoked as root, B<heimdal-history> will run the external strength checking
726 program as user C<nobody> and group C<nogroup>, and will check and write to
727 the history database as user C<_history> and group C<_history>. These users
728 must exist on the system if it is run as root.
730 The result of each password check will be logged to syslog (priority LOG_INFO,
731 facility LOG_AUTH). Each log line will be a set of key/value pairs in the
732 format C<< I<key>=I<value> >>. The keys are:
738 The action performed (currently always C<check>).
742 The principal for which a password was checked.
746 An internal error message that did not stop the history check, but which may
747 indicate that something is wrong with the history database (such as corrupted
748 entries or invalid hashes). If this key is present, neither C<result> nor
749 C<reason> will be present. There will be a subsequent log message from the
750 same invocation giving the final result of the history check (assuming
751 B<heimdal-history> doesn't exit with a fatal error).
755 Either C<accepted> or C<rejected>.
759 If the password was rejected, the reason for the rejection.
763 The value will be surrounded with double quotes if it contains a double quote
764 or space. Any double quotes in the value will be doubled, so C<"> becomes
771 =item B<-b> I<target-time>, B<--benchmark>=I<target-time>
773 Do not do a password history check. Instead, benchmark the hash algorithm
774 with various possible iteration counts and find an iteration count that
775 results in I<target-time> seconds of computation time required to hash a
776 password (which should be a real number). A result will be considered
777 acceptable if it is within 0.005 seconds of the target time. The results will
778 be printed to standard output and then B<heimdal-history> will exit
781 =item B<-c>, B<--check-only>
783 Check password history and password strength and print the results as normal,
784 but do not update the history or length statistics databases. This is a
785 read-only mode of operation that will not make any changes to the underlying
786 database, only report if a password would currently be accepted.
788 =item B<-d> I<database>, B<--database>=I<database>
790 Use I<database> as the history database file instead of the default
791 (F</var/lib/heimdal-history/history.db>). Primarily used for testing, since
792 Heimdal won't pass this argument.
794 =item B<-h>, B<--help>
796 Print a short usage message and exit.
798 =item B<-m>, B<--manual>, B<--man>
800 Display this manual and exit.
802 =item B<-q>, B<--quiet>
804 Suppress logging to syslog and only return the results on standard output and
805 standard error. Primarily used for testing, since Heimdal won't pass this
808 =item B<-S> I<length-stats-db>, B<--stats>=I<length-stats-db>
810 Use I<length-stats-db> as the database file for password length statistics
811 instead of the default (F</var/lib/heimdal-history/lengths.db>). Primarily
812 used for testing, since Heimdal won't pass this argument.
814 =item B<-s> I<strength-program>, B<--strength>=I<strength-program>
816 Run I<strength-program> as the external strength-checking program instead of
817 the default (F</usr/bin/heimdal-strength>). Primarily used for testing, since
818 Heimdal won't pass this argument.
824 Additional setup is required to use this history implementation with your
827 First, ensure that its dependencies are installed, and then examine the local
828 configuration settings at the top of the B<heimdal-history> program. By
829 default, it requires a C<_history> user and C<_history> group be present on
830 the system, and all history information will be read and written as that user
831 and group. It also requires a C<nobody> user and C<nogroup> group to be
832 present (this should be the default with most variants of UNIX), and all
833 strength checking will be done as that user and group. It uses various files
834 in F</var/lib/heimdal-history> to store history and statistical information by
835 default, so if using the defaults, create that directory and ensure it is
836 writable by the C<_history> user.
838 Once that setup is done, change your C<[password_quality]> configuration in
839 F<krb5.conf> or F<kdc.conf> to:
842 policies = external-check
843 external_program = /usr/local/bin/heimdal-history
845 The B<heimdal-history> program will automatically also run B<heimdal-strength>
846 as well, looking for it in F</usr/bin>. Change the C<$STRENGTH_PROGRAM>
847 setting at the top of the script if you have that program in a different
848 location. You should continue to configure B<heimdal-strength> as if you were
853 On approval of the password, B<heimdal-history> will print C<APPROVED> and a
854 newline to standard output and exit with status 0.
856 If the password is rejected by the strength checking program or if it (or a
857 version with a single character removed) matches one of the hashes stored in
858 the password history, B<heimdal-history> will print the reason for rejection
859 to standard error and exit with status 0.
861 On any internal error, B<heimdal-history> will print the error to standard
862 error and exit with a non-zero status.
868 =item F</usr/bin/heimdal-strength>
870 The default password strength checking program. This program must follow the
871 Heimdal external password strength checking API.
873 =item F</var/lib/heimdal-history/history.db>
875 The default database path. If B<heimdal-strength> is run as root, this file
876 needs to be readable and writable by user C<_history> and group C<_history>.
877 If it doesn't exist, it will be created with mode 0600.
879 =item F</var/lib/heimdal-history/history.db.lock>
881 The lock file used to synchronize access to the history database. As with the
882 history database, if B<heimdal-strength> is run as root, this file needs to be
883 readable and writable by user C<_history> and group C<_history>.
885 =item F</var/lib/heimdal-history/lengths.db>
887 The default length statistics path, which will be a BerkeleyDB DB_HASH file of
888 password lengths to counts of passwords with that length. If
889 B<heimdal-strength> is run as root, this file needs to be readable and
890 writable by user C<_history> and group C<_history>. If it doesn't exist, it
891 will be created with mode 0600.
893 =item F</var/lib/heimdal-history/lengths.db.lock>
895 The lock file used to synchronize access to the length statistics database.
896 As with the length statistics database, if B<heimdal-strength> is run as root,
897 this file needs to be readable and writable by user C<_history> and group
904 Russ Allbery <eagle@eyrie.org>
906 =head1 COPYRIGHT AND LICENSE
908 Copyright 2016-2017, 2020, 2023 Russ Allbery <eagle@eyrie.org>
910 Copyright 2013-2014 The Board of Trustees of the Leland Stanford Junior
913 Permission is hereby granted, free of charge, to any person obtaining a copy
914 of this software and associated documentation files (the "Software"), to deal
915 in the Software without restriction, including without limitation the rights
916 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
917 copies of the Software, and to permit persons to whom the Software is
918 furnished to do so, subject to the following conditions:
920 The above copyright notice and this permission notice shall be included in all
921 copies or substantial portions of the Software.
923 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
924 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
925 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
926 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
927 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
928 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
931 SPDX-License-Identifier: MIT
935 L<Crypt::PBKDF2>, L<heimdal-strength(1)>
940 # copyright-at-end-flag: t