1 # Package metadata for krb5-strength.
3 # This file contains configuration for DocKnot used to generate
4 # documentation files (like README.md) and web pages. Other documentation
5 # in this package is generated automatically from these files as part of
6 # the release process. For more information, see DocKnot's documentation.
8 # DocKnot is available from <https://www.eyrie.org/~eagle/software/docknot/>.
10 # Copyright 2007, 2009-2010, 2012-2014, 2016-2017, 2020, 2023
11 # Russ Allbery <eagle@eyrie.org>
13 # SPDX-License-Identifier: MIT
18 maintainer: Russ Allbery <eagle@eyrie.org>
20 synopsis: Kerberos password strength checking plugin
25 Developed by Daria Phoebe Brashear and Ken Hornstein of Sine Nomine
26 Associates, on behalf of Stanford University.
28 The embedded version of CrackLib (all files in the `cracklib`
29 subdirectory) is covered by the Artistic license. See the file
30 `cracklib/LICENCE` for more information. Combined derivative works that
31 include this code, such as binaries built with the embedded CrackLib, will
32 need to follow the terms of the Artistic license as well as the above
35 - holder: Russ Allbery <eagle@eyrie.org>
36 years: 2016, 2020, 2023
37 - holder: The Board of Trustees of the Leland Stanford Junior University
38 years: 2006-2007, 2009-2010, 2012-2014
39 - holder: Alec Muffett
50 You will also need Perl 5.010 or later and the Const::Fast, DBI,
51 DBD::SQLite, JSON::MaybeXS, and Perl6::Slurp modules (from CPAN) to
52 bootstrap the test suite data from a Git checkout.
54 By default, the Heimdal external password check function is installed as
55 `/usr/local/bin/heimdal-strength`, and the plugin is installed as
56 `/usr/local/lib/krb5/plugins/pwqual/strength.so`. You can change these
57 paths with the `--prefix`, `--libdir`, and `--bindir` options to
60 By default, the embedded version of CrackLib will be used. To build with
61 the system version of CrackLib, pass `--with-cracklib` to `configure`.
62 You can optionally add a directory, giving the root directory where
63 CrackLib was installed, or separately set the include and library path
64 with `--with-cracklib-include` and `--with-cracklib-lib`. You can also
65 build without any CrackLib support by passing `--without-cracklib` to
68 krb5-strength will automatically build with TinyCDB if it is found. To
69 specify the installation path of TinyCDB, use `--with-tinycdb`. You can
70 also separately set the include and library path with
71 `--with-tinycdb-include` and `--with-tinycdb-lib`.
73 Similarly, krb5-strength will automatically build with SQLite if it is
74 found. To specify the installation path of SQLite, use `--with-sqlite`.
75 You can also separately set the include and library path with
76 `--with-sqlite-include` and `--with-sqlite-lib`.
78 After installing this software, see the man pages for krb5-strength,
79 heimdal-strength, and heimdal-history for configuration information.
84 tarname: krb5-strength
85 version: krb5-strength
88 package: krb5-strength
90 A Debian package is included in Debian 8.0 (jessie) and later
93 email: eagle@eyrie.org
94 github: rra/krb5-strength
95 web: https://www.eyrie.org/~eagle/software/krb5-strength/
97 browse: https://git.eyrie.org/?p=kerberos/krb5-strength.git
98 github: rra/krb5-strength
99 openhub: https://www.openhub.net/p/krb5-strength
103 url: https://git.eyrie.org/git/kerberos/krb5-strength.git
107 - name: heimdal-history
108 title: heimdal-history
109 - name: heimdal-strength
110 title: heimdal-strength
111 - name: krb5-strength
112 title: krb5-strength plugin
114 title: krb5-strength-wordlist
120 krb5-strength provides a password quality plugin for the MIT Kerberos KDC
121 (specifically the kadmind server) and Heimdal KDC, an external password
122 quality program for use with Heimdal, and a per-principal password history
123 implementation for Heimdal. Passwords can be tested with CrackLib,
124 checked against a CDB or SQLite database of known weak passwords with some
125 transformations, checked for length, checked for non-printable or
126 non-ASCII characters that may be difficult to enter reproducibly, required
127 to contain particular character classes, or any combination of these
131 Heimdal includes a capability to plug in external password quality checks
132 and comes with an example that checks passwords against CrackLib.
133 However, in testing at Stanford, we found that CrackLib with its default
134 transform rules does not catch passwords that can be guessed using the
135 same dictionary with other tools, such as Jack the Ripper. We then
136 discovered other issues with CrackLib with longer passwords, such as some
137 bad assumptions about how certain measures of complexity will scale, and
138 wanted to impose other limitations that it didn't support.
140 This plugin provides the ability to check password quality against the
141 standard version of CrackLib, or against a modified version of CrackLib
142 that only passes passwords that resist attacks from both Crack and Jack
143 the Ripper using the same rule sets. It also supports doing simpler
144 dictionary checks against a CDB database, which is fast with very large
145 dictionaries, or a SQLite database, which can reject all passwords within
146 edit distance one of a dictionary word. It can also impose other
147 programmatic checks on passwords such as character class requirements.
149 If you're just now starting with password checking, I recommend using the
150 SQLite database with a large wordlist and minimum password lengths. We
151 found this produced the best results with the least user frustration.
153 For Heimdal, krb5-strength includes both a program usable as an external
154 password quality check and a plugin that implements the dynamic module
155 API. For MIT Kerberos (1.9 or later), it includes a plugin for the
156 password quality (pwqual) plugin API.
158 krb5-strength can be built with either the system CrackLib or with the
159 modified version of CrackLib included in this package. Note, however,
160 that if you're building against the system CrackLib, Heimdal includes in
161 the distribution a strength-checking plugin and an external password check
162 program that use the system CrackLib. With Heimdal, it would probably be
163 easier to use that plugin or program than build this package unless you
164 want the modified CrackLib, one of the other dictionary types, or the
165 additional character class and length checks.
167 For information about the changes to the CrackLib included in this
168 toolkit, see `cracklib/HISTORY`. The primary changes are tighter rules,
169 which are more aggressive at finding dictionary words with characters
170 appended and prepended, which tighten the requirements for password
171 entropy, and which add stricter rules for longer passwords. They are also
172 minor changes to fix portability issues, remove some code that doesn't
173 make sense in the kadmind context, and close a few security issues. The
174 standard CrackLib distribution on at least some Linux distributions now
175 supports an additional interface to configure its behavior, and
176 krb5-strength should change in the future to use that interface and drop
179 krb5-strength also includes a password history implementation for Heimdal.
180 This is separate from the password strength implementation but can be
181 stacked with it so that both strength and history checks are performed.
182 This history implementation is available only via the Heimdal external
183 password quality interface. MIT Kerberos includes its own password
184 history implementation.
187 For Heimdal, you may use either the external password quality check tool,
188 installed as heimdal-strength, or the plugin as you choose. It has been
189 tested with Heimdal 1.2.1 and later, but has not recently been tested with
190 versions prior to 7.0.
192 For MIT Kerberos, version 1.9 or higher is required for the password
193 quality plugin interface. MIT Kerberos does not support an external
194 password quality check tool directly, so you will need to install the
197 You can optionally build against the system CrackLib library. Any version
198 should be supported, but note that some versions, particularly older
199 versions close to the original code, do things like printing diagnostics
200 to stderr, calling exit, and otherwise not being well-behaved for use
201 inside plugins or libraries. They also have known security
202 vulnerabilities. If using a system CrackLib library, use version 2.8.22
203 or later to avoid these problems.
205 You can also optionally build against the TinyCDB library, which provides
206 support for simpler and faster password checking against a CDB dictionary
207 file, and the SQLite library (a version new enough to support the
208 `sqlite3_open_v2` API; 3.7 should be more than sufficient), which provides
209 support for checking whether passwords are within edit distance one of a
212 For this module to be effective for either Heimdal or MIT Kerberos, you
213 will also need to construct a dictionary. The `mkdict` and `packer`
214 utilities to build a CrackLib dictionary from a word list are included in
215 this toolkit but not installed by default. You can run them out of the
216 `cracklib` directory after building. You can also use the utilities that
217 come with the stock CrackLib package (often already packaged in a Linux
218 distribution); the database format is compatible.
220 For building a CDB or SQLite dictionary, use the provided
221 `krb5-strength-wordlist` program. For CDB dictionries, the `cdb` utility
222 must be on your `PATH`. For SQLite, the DBI and DBD::SQLite Perl modules
223 are required. `krb5-strength-wordlist` requires Perl 5.010 or later.
225 For a word list to use as source for the dictionary, you can use
226 `/usr/share/dict/words` if it's available on your system, but it would be
227 better to find a more comprehensive word list. Since word lists are
228 bulky, often covered by murky copyrights, and easily locatable on the
229 Internet with a modicum of searching, none are included in this toolkit.
231 The password history program, heimdal-history, requires Perl 5.010 or
232 later plus the following CPAN modules:
237 * Getopt::Long::Descriptive
241 and their dependencies.
246 To run the test suite, you will need Perl 5.010 or later and the
247 dependencies of the `heimdal-history` program. The following additional
248 Perl modules will also be used by the test suite if present:
251 * Test::MinimumVersion
257 All are available on CPAN. Some tests will be skipped if the modules