                            krb5-strength 3.3
               (Kerberos password strength checking plugin)
               Maintained by Russ Allbery <eagle@eyrie.org>

  Copyright 2016, 2020, 2023 Russ Allbery <eagle@eyrie.org>.  Copyright
  2006-2007, 2009-2010, 2012-2014 The Board of Trustees of the Leland
  Stanford Junior University.  Copyright 1993 Alec Muffett.  This software
  is distributed under a BSD-style license.  Please see the section
  LICENSE below for more information.

BLURB

  krb5-strength provides a password quality plugin for the MIT Kerberos
  KDC (specifically the kadmind server) and Heimdal KDC, an external
  password quality program for use with Heimdal, and a per-principal
  password history implementation for Heimdal.  Passwords can be tested
  with CrackLib, checked against a CDB or SQLite database of known weak
  passwords with some transformations, checked for length, checked for
  non-printable or non-ASCII characters that may be difficult to enter
  reproducibly, required to contain particular character classes, or any
  combination of these tests.

DESCRIPTION

  Heimdal includes a capability to plug in external password quality
  checks and comes with an example that checks passwords against CrackLib.
  However, in testing at Stanford, we found that CrackLib with its default
  transform rules does not catch passwords that can be guessed using the
  same dictionary with other tools, such as Jack the Ripper.  We then
  discovered other issues with CrackLib with longer passwords, such as
  some bad assumptions about how certain measures of complexity will
  scale, and wanted to impose other limitations that it didn't support.

  This plugin provides the ability to check password quality against the
  standard version of CrackLib, or against a modified version of CrackLib
  that only passes passwords that resist attacks from both Crack and Jack
  the Ripper using the same rule sets.  It also supports doing simpler
  dictionary checks against a CDB database, which is fast with very large
  dictionaries, or a SQLite database, which can reject all passwords
  within edit distance one of a dictionary word.  It can also impose other
  programmatic checks on passwords such as character class requirements.

  If you're just now starting with password checking, I recommend using
  the SQLite database with a large wordlist and minimum password lengths.
  We found this produced the best results with the least user frustration.

  For Heimdal, krb5-strength includes both a program usable as an external
  password quality check and a plugin that implements the dynamic module
  API.  For MIT Kerberos (1.9 or later), it includes a plugin for the
  password quality (pwqual) plugin API.

  krb5-strength can be built with either the system CrackLib or with the
  modified version of CrackLib included in this package.  Note, however,
  that if you're building against the system CrackLib, Heimdal includes in
  the distribution a strength-checking plugin and an external password
  check program that use the system CrackLib.  With Heimdal, it would
  probably be easier to use that plugin or program than build this package
  unless you want the modified CrackLib, one of the other dictionary
  types, or the additional character class and length checks.

  For information about the changes to the CrackLib included in this
  toolkit, see cracklib/HISTORY.  The primary changes are tighter rules,
  which are more aggressive at finding dictionary words with characters
  appended and prepended, which tighten the requirements for password
  entropy, and which add stricter rules for longer passwords.  They are
  also minor changes to fix portability issues, remove some code that
  doesn't make sense in the kadmind context, and close a few security
  issues.  The standard CrackLib distribution on at least some Linux
  distributions now supports an additional interface to configure its
  behavior, and krb5-strength should change in the future to use that
  interface and drop the embedded copy.

  krb5-strength also includes a password history implementation for
  Heimdal.  This is separate from the password strength implementation but
  can be stacked with it so that both strength and history checks are
  performed.  This history implementation is available only via the
  Heimdal external password quality interface.  MIT Kerberos includes its
  own password history implementation.

REQUIREMENTS

  For Heimdal, you may use either the external password quality check
  tool, installed as heimdal-strength, or the plugin as you choose.  It
  has been tested with Heimdal 1.2.1 and later, but has not recently been
  tested with versions prior to 7.0.

  For MIT Kerberos, version 1.9 or higher is required for the password
  quality plugin interface.  MIT Kerberos does not support an external
  password quality check tool directly, so you will need to install the
  plugin.

  You can optionally build against the system CrackLib library.  Any
  version should be supported, but note that some versions, particularly
  older versions close to the original code, do things like printing
  diagnostics to stderr, calling exit, and otherwise not being
  well-behaved for use inside plugins or libraries.  They also have known
  security vulnerabilities.  If using a system CrackLib library, use
  version 2.8.22 or later to avoid these problems.

  You can also optionally build against the TinyCDB library, which
  provides support for simpler and faster password checking against a CDB
  dictionary file, and the SQLite library (a version new enough to support
  the sqlite3_open_v2 API; 3.7 should be more than sufficient), which
  provides support for checking whether passwords are within edit distance
  one of a dictionary word.

  For this module to be effective for either Heimdal or MIT Kerberos, you
  will also need to construct a dictionary.  The mkdict and packer
  utilities to build a CrackLib dictionary from a word list are included
  in this toolkit but not installed by default.  You can run them out of
  the cracklib directory after building.  You can also use the utilities
  that come with the stock CrackLib package (often already packaged in a
  Linux distribution); the database format is compatible.

  For building a CDB or SQLite dictionary, use the provided
  krb5-strength-wordlist program.  For CDB dictionries, the cdb utility
  must be on your PATH.  For SQLite, the DBI and DBD::SQLite Perl modules
  are required.  krb5-strength-wordlist requires Perl 5.010 or later.

  For a word list to use as source for the dictionary, you can use
  /usr/share/dict/words if it's available on your system, but it would be
  better to find a more comprehensive word list.  Since word lists are
  bulky, often covered by murky copyrights, and easily locatable on the
  Internet with a modicum of searching, none are included in this toolkit.

  The password history program, heimdal-history, requires Perl 5.010 or
  later plus the following CPAN modules:

  * Const::Fast
  * Crypt::PBKDF2
  * DB_File::Lock
  * Getopt::Long::Descriptive
  * IPC::Run
  * JSON::MaybeXS

  and their dependencies.

  To bootstrap from a Git checkout, or if you change the Automake files
  and need to regenerate Makefile.in, you will need Automake 1.11 or
  later.  For bootstrap or if you change configure.ac or any of the m4
  files it includes and need to regenerate configure or config.h.in, you
  will need Autoconf 2.64 or later.  Perl is also required to generate
  manual pages from a fresh Git checkout.  You will also need Perl 5.010
  or later and the Const::Fast, DBI, DBD::SQLite, JSON::MaybeXS, and
  Perl6::Slurp modules (from CPAN) to bootstrap the test suite data from a
  Git checkout.

BUILDING AND INSTALLATION

  You can build and install krb5-strength with the standard commands:

      ./configure
      make
      make install

  If you are building from a Git clone, first run ./bootstrap in the
  source directory to generate the build files.  make install will
  probably have to be done as root.  Building outside of the source
  directory is also supported, if you wish, by creating an empty directory
  and then running configure with the correct relative path.

  By default, the Heimdal external password check function is installed as
  /usr/local/bin/heimdal-strength, and the plugin is installed as
  /usr/local/lib/krb5/plugins/pwqual/strength.so.  You can change these
  paths with the --prefix, --libdir, and --bindir options to configure.

  By default, the embedded version of CrackLib will be used.  To build
  with the system version of CrackLib, pass --with-cracklib to configure.
  You can optionally add a directory, giving the root directory where
  CrackLib was installed, or separately set the include and library path
  with --with-cracklib-include and --with-cracklib-lib.  You can also
  build without any CrackLib support by passing --without-cracklib to
  configure.

  krb5-strength will automatically build with TinyCDB if it is found.  To
  specify the installation path of TinyCDB, use --with-tinycdb.  You can
  also separately set the include and library path with
  --with-tinycdb-include and --with-tinycdb-lib.

  Similarly, krb5-strength will automatically build with SQLite if it is
  found.  To specify the installation path of SQLite, use --with-sqlite.
  You can also separately set the include and library path with
  --with-sqlite-include and --with-sqlite-lib.

  Normally, configure will use krb5-config to determine the flags to use
  to compile with your Kerberos libraries.  To specify a particular
  krb5-config script to use, either set the PATH_KRB5_CONFIG environment
  variable or pass it to configure like:

      ./configure PATH_KRB5_CONFIG=/path/to/krb5-config

  If krb5-config isn't found, configure will look for the standard
  Kerberos libraries in locations already searched by your compiler.  If
  the the krb5-config script first in your path is not the one
  corresponding to the Kerberos libraries you want to use, or if your
  Kerberos libraries and includes aren't in a location searched by default
  by your compiler, you need to specify a different Kerberos installation
  root via --with-krb5=PATH.  For example:

      ./configure --with-krb5=/usr/pubsw

  You can also individually set the paths to the include directory and the
  library directory with --with-krb5-include and --with-krb5-lib.  You may
  need to do this if Autoconf can't figure out whether to use lib, lib32,
  or lib64 on your platform.

  To not use krb5-config and force library probing even if there is a
  krb5-config script on your path, set PATH_KRB5_CONFIG to a nonexistent
  path:

      ./configure PATH_KRB5_CONFIG=/nonexistent

  krb5-config is not used and library probing is always done if either
  --with-krb5-include or --with-krb5-lib are given.

  Pass --enable-silent-rules to configure for a quieter build (similar to
  the Linux kernel).  Use make warnings instead of make to build with full
  compiler warnings (requires either GCC or Clang and may require a
  relatively current version of the compiler).

  You can pass the --enable-reduced-depends flag to configure to try to
  minimize the shared library dependencies encoded in the binaries.  This
  omits from the link line all the libraries included solely because other
  libraries depend on them and instead links the programs only against
  libraries whose APIs are called directly.  This will only work with
  shared libraries and will only work on platforms where shared libraries
  properly encode their own dependencies (this includes most modern
  platforms such as all Linux).  It is intended primarily for building
  packages for Linux distributions to avoid encoding unnecessary shared
  library dependencies that make shared library migrations more difficult.
  If none of the above made any sense to you, don't bother with this flag.

  After installing this software, see the man pages for krb5-strength,
  heimdal-strength, and heimdal-history for configuration information.

TESTING

  krb5-strength comes with a test suite, which you can run after building
  with:

      make check

  If a test fails, you can run a single test with verbose output via:

      tests/runtests -o <name-of-test>

  Do this instead of running the test program directly since it will
  ensure that necessary environment variables are set up.

  To run the test suite, you will need Perl 5.010 or later and the
  dependencies of the heimdal-history program.  The following additional
  Perl modules will also be used by the test suite if present:

  * Perl6::Slurp
  * Test::MinimumVersion
  * Test::Perl::Critic
  * Test::Pod
  * Test::Spelling
  * Test::Strict

  All are available on CPAN.  Some tests will be skipped if the modules
  are not available.

  To enable tests that don't detect functionality problems but are used to
  sanity-check the release, set the environment variable RELEASE_TESTING
  to a true value.  To enable tests that may be sensitive to the local
  environment or that produce a lot of false positives without uncovering
  many problems, set the environment variable AUTHOR_TESTING to a true
  value.

SUPPORT

  The krb5-strength web page at:

      https://www.eyrie.org/~eagle/software/krb5-strength/

  will always have the current version of this package, the current
  documentation, and pointers to any additional resources.

  For bug tracking, use the issue tracker on GitHub:

      https://github.com/rra/krb5-strength/issues

  However, please be aware that I tend to be extremely busy and work
  projects often take priority.  I'll save your report and get to it as
  soon as I can, but it may take me a couple of months.

SOURCE REPOSITORY

  krb5-strength is maintained using Git.  You can access the current
  source on GitHub at:

      https://github.com/rra/krb5-strength

  or by cloning the repository at:

      https://git.eyrie.org/git/kerberos/krb5-strength.git

  or view the repository via the web at:

      https://git.eyrie.org/?p=kerberos/krb5-strength.git

  The eyrie.org repository is the canonical one, maintained by the author,
  but using GitHub is probably more convenient for most purposes.  Pull
  requests are gratefully reviewed and normally accepted.

LICENSE

  The krb5-strength package as a whole is covered by the following
  copyright statement and license:

    Copyright 2016, 2020, 2023 Russ Allbery <eagle@eyrie.org>
    Copyright 2006-2007, 2009-2010, 2012-2014
        The Board of Trustees of the Leland Stanford Junior University
    Copyright 1993 Alec Muffett

    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.

    Developed by Daria Phoebe Brashear and Ken Hornstein of Sine Nomine
    Associates, on behalf of Stanford University.

    The embedded version of CrackLib (all files in the cracklib
    subdirectory) is covered by the Artistic license.  See the file
    cracklib/LICENCE for more information.  Combined derivative works that
    include this code, such as binaries built with the embedded CrackLib,
    will need to follow the terms of the Artistic license as well as the
    above license.

  Some files in this distribution are individually released under
  different licenses, all of which are compatible with the above general
  package license but which may require preservation of additional
  notices.  All required notices, and detailed information about the
  licensing of each file, are recorded in the LICENSE file.

  Files covered by a license with an assigned SPDX License Identifier
  include SPDX-License-Identifier tags to enable automated processing of
  license information.  See https://spdx.org/licenses/ for more
  information.

  For any copyright range specified by files in this package as YYYY-ZZZZ,
  the range specifies every single year in that closed interval.
