User-Visible krb5-strength Changes

krb5-strength 3.2 (2020-05-17)

Add new -c (--check-only) option to heimdal-history to check whether a password would be accepted without updating the history or password length databases. Based on work by macrotex.

Increase hash iterations for heimdal-history by roughly a factor of four to increase the time required for a password hash to about 0.1 seconds on modern hardware. This will affect newly-stored history entries but will not invalidate existing password history entries.

Support building without CrackLib support by passing --without-cracklib to configure. This makes the code a bit simpler and lighter if you don't intend to ever use the CrackLib support.

krb5-strength-wordlist now requires Perl 5.010 or later.

Use explicit_bzero instead of memset, where available, to overwrite copies of passwords before freeing memory. This reduces the lifetime of passwords in memory.

Skip tests that require the stronger rule configuration in the embedded CrackLib when built against system CrackLib. This avoids test failures when built with system CrackLib.

Rework the check-valgrind target to use the new C TAP Harness valgrind support and automatically check the valgrind log files for errors at the end of the test suite.

Add SPDX-License-Identifier headers to all substantial source files other than those in the bundled version of CrackLib.

Update to rra-c-util 8.2:

Update to C TAP Harness 4.7:

krb5-strength 3.1 (2016-12-25)

A new configuration option, cracklib_maxlen, can be set to skip CrackLib checks of passwords longer than that length. The CrackLib rules were designed in a world in which most passwords were four to eight characters long and tend to spuriously reject longer passwords. SQLite dictionaries work better for checking longer passwords and passphrases. Patch from Jorj Bauer.

The require_classes configuration option can now require a particular number of character classes in the password (whatever those classes are). Patch from Toby Blake.

Change the error messages returned for passwords that fail strength checking to start with a capital letter. This appears to be more consistent with the error message conventions used inside Heimdal.

Change the DB_File::Lock calling method in heimdal-history to work properly with the (buggy) CPAN version of DB_File::Lock, instead of relying on Debian's patched version. Thanks to Bernt Jernberg for the report.

Apply the SuSE patch for a buffer overflow when using duplicate rules to the embedded CrackLib. No duplicating rules are used in the rule set included with this package, and this package doesn't expose the general API, so this was not exploitable, but best to close the latent issue. (The other recent CrackLib vulnerability, CVE-2016-6318, doesn't apply since all the GECOS manipulation code was removed from the embedded CrackLib in this package.)

Patch the mkdict and packer in the embedded copy of CrackLib to force C locale when sorting (avoiding a corrupted dictionary) and warn and skip out-of-order words rather than creating a corrupted dictionary. Patch from Mark Sirota.

Configuration instrutions are now in the heimdal-history and heimdal-strength man pages and a new krb5-strength man page (which documents configuration of the KDC plugin) instead of the README file to make it more accessible after the software has been installed.

Update to rra-c-util 6.2:

Update to C TAP Harness 4.1:

krb5-strength 3.0 (2014-03-25)

The krb5-strength plugin and heimdal-strength program now support a SQLite password dictionary. This format of dictionary can detect any password within edit distance one of a dictionary word, meaning that the dictionary word can be formed by adding, removing, or changing a single character in the password. A SQLite password dictionary can be used alone or in combination with any of the other supported dictionary types. SQLite dictionary support is based on work by David Mazières.

cdbmake-wordlist has been renamed to krb5-strength-wordlist. Generating CDB dictionaries now requires the -c option; see the documentation for more information. A SQLite database of dictionary words can now be created instead, using the -s option.

A password history implementation for Heimdal is now included. This is a separate Perl program, heimdal-history, that stacks with the external program implementation of strength checking. It is not available in the form of a plugin, only as a Heimdal external password quality check. (MIT Kerberos provides its own password history mechanism.) This program has more extensive Perl module dependencies than the other programs in this distribution.

A new configuration option, minimum_different, can be set to require that passwords contain at least that many unique characters. This can be used to reject long strings of identical characters or short patterns, which may pass other checks but still be too easy to guess.

Update to rra-c-util 5.4:

Update to C TAP Harness 3.0:

krb5-strength 2.2 (2013-12-16)

More complex character class requirements can be specified with the configuration option require_classes. This option lists the character classes the password must contain. These restrictions may be qualified with password length ranges, allowing the requirements to change with the length of the password. See README for more details and the option syntax.

cdbmake-wordlist now supports filtering out words based on maximum length (-L) and arbitrary user-provided regular expressions (-x). It also supports running in filter mode to produce a new wordlist instead of a CDB file (-o).

Close a file descriptor and memory leak in the included version of CrackLib. This problem was already fixed in CrackLib 2.9.0.

Update to rra-c-util 4.12:

Update to C TAP Harness 2.3:

krb5-strength 2.1 (2013-10-10)

Fix the package build when CDB support is disabled or TinyCDB was not found.

Some of the password rejection error messages have been changed to make them more accurate or comprehensible to the user.

Passing --with-tinycdb to configure now correctly makes TinyCDB support mandatory without adding bogus directories to the library and include search paths.

krb5-strength 2.0 (2013-10-07)

Add support for the MIT Kerberos password quality plugin interface, available in MIT Kerberos 1.9 and later, contributed by Greg Hudson and MIT. Drop the patch for MIT Kerberos 1.4 (and hence support for versions of MIT Kerberos prior to 1.9). A dictionary path set in krb5.conf takes precedence over the dictionary path provided by MIT Kerberos when the plugin is initialized, if both are set, to allow the dict_path configuration setting to be used for other plugins while using a separate dictionary for krb5-strength.

The default installation path for this plugin is now /usr/local/lib/krb5/plugins/pwqual/ (for both MIT and Heimdal), assuming a --libdir setting of /usr/local/lib. This may require updates to the Kerberos KDC configuration or moving the plugin when upgrading from earlier versions.

Add support for building with TinyCDB and then checking passwords against a CDB database. There is a new password_dictionary_cdb krb5.conf configuration setting that configures a CDB directory to use. The tests with a CDB dictionary are much simpler: passwords are rejected if found in the dictionary either literally, with one or two characters removed from the start or end, or with one character removed from both the start and the end. Both a CrackLib and a CDB dictionary can be specified to check both dictionaries. A new cdbmake-wordlist utility (written in Perl) is included to ease the process of creating a CDB database from a simple word list.

A minimum password length can now be enforced directly via the plugin or external check program without relying on CrackLib. To set a minimum password length, add a minimum_length setting to the krb5-strength section of [appdefaults] in krb5.conf.

New boolean settings require_ascii_printable and require_non_letter are supported in the krb5-strength setting of [appdefaults] in krb5.conf. The former rejects passwords containing characters other than printable ASCII characters (including space), and the latter requires that passwords contain at least one character that is not a letter (upper or lower case) or a space.

The plugin can now be configured without a dictionary, in which case only checks for a password based on the principal and the simpler checks available through the new configuration variables are done. This mode is mostly useful for testing, since such simple checking can more easily be done via less complex password strength configurations.

The check for passwords based on the principal now check for passwords formed by reversing or adding numbers before and after each separate component of the principal. This will catch passwords based on the realm or components of the realm, which will often catch passwords based on the name of the local institution.

The plugin now sets the Kerberos error message in the context to pass error information, resulting in higher-quality error reporting in the MIT Kerberos plugin.

CrackLib checks for passwords where a character is a simple increment or decrement of the previous character. In previous versions, the embedded version of CrackLib allowed at most four such occurrences in the entire password. This results in false positives on long passphrases, since such accidental letter relationships aren't uncommon in human languages. Change the embedded CrackLib to allow one such simple increment for every three characters in the password, which tightens the check somewhat for shorter passwords and loosens it considerably for longer passwords.

Expect the Heimdal password strength checking plugin header in kadm5/kadm5-pwcheck.h instead of outside of the kadm5 directory. This is the path used by current versions of Heimdal. Drop support for older versions of Heimdal that don't install this header file.

Update to rra-c-util 4.9:

Update to C TAP Harness 2.2:

krb5-strength 1.1 (2012-05-11)

Change the minimum password length in the embedded CrackLib to 8.

Reject passwords formed from the username portion of the principal with digits appended.

In the embedded CrackLib, also check for a duplicated dictionary word.

Support linking with the system CrackLib instead of the embedded and stricter copy by passing --with-cracklib to configure.

Fix variable sizes in the embedded CrackLib on 64-bit platforms. This may fix interoperability problems with databases created on platforms with a different native integer size. Thanks, Karl Lehnberger and Benj Carson.

Stop using local in the test suite for portability to Solaris /bin/sh.

Update to rra-c-util 4.4:

Update to C TAP Harness 1.12:

krb5-strength 1.0 (2010-02-16)

Add heimdal-strength, a program that checks password strength using the protocol for a Heimdal external check program.

The shared module now also exports the interface expected by Heimdal's dynamically loaded password strength checking API and can be used as a Heimdal kadmin plugin.

Add a new plugin API for MIT Kerberos modelled after the plugin API used for other MIT Kerberos plugins. Thanks to Marcus Watts for substantial research and contributions to the interface design. This work is incomplete in this release, missing the corresponding patch to MIT Kerberos.

Fixed the data format written by the included packer program to add enough nul bytes at the end of the data. Previously, there was not enough trailing nul bytes for the expected input format, leading to uninitialized memory reads in the password lookup.

Add a test suite using the driver and library from C TAP Harness 1.1.

Add portability code for platforms without a working snprintf or other deficiencies and updated the code to take advantage of those guarantees.

krb5-strength 0.5 (2007-07-18)

The check of the password against the principal checked against the fully-qualified principal, which is not the usual problem. Additionally check that the password doesn't match the principal with the realm removed or the reverse of that (case-insensitive).

krb5-strength 0.4 (2007-03-28)

The patches directory was omitted from the distribution. Really include it.

krb5-strength 0.3 (2007-03-23)

Initial public release. Includes a patch for MIT Kerberos, a slightly modified version of CrackLib, and glue wrapped around CrackLib to make a loadable module.

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