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.IX Title "HEIMDAL-STRENGTH 1"
-.TH HEIMDAL-STRENGTH 1 "2013-10-07" "2.0" "krb5-strength"
+.TH HEIMDAL-STRENGTH 1 "2023-12-26" "3.3" "krb5-strength"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.if n .ad l
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBheimdal-strength\fR is an external password quality check program for
-Heimdal that verifies the strength of a password using an embedded copy of
-CrackLib, with some modifications to increase the aggressiveness of its
-rules. It is normally run via \fIkpasswdd\fR\|(8) using the Heimdal password
-quality check interface rather than directly.
+Heimdal that verifies the strength of a password. Passwords can be tested
+with CrackLib, checked against a \s-1CDB\s0 database of known weak passwords,
+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. It is normally run
+via \fBkpasswdd\fR\|(8) using the Heimdal password quality check interface rather
+than directly.
.PP
-To use this program, the path to a CrackLib database must be configured in
-krb5.conf via the \f(CW\*(C`password_dictionary\*(C'\fR setting in \f(CW\*(C`[appdefaults]\*(C'\fR. It
-uses the application name \f(CW\*(C`krb5\-strength\*(C'\fR when trying to find this
-setting. A typical setting would be:
+To use this program, it must be configured in \fIkrb5.conf\fR via settings
+in \f(CW\*(C`[appdefaults]\*(C'\fR for the application name \f(CW\*(C`krb5\-strength\*(C'\fR. A typical
+setting would be:
.PP
.Vb 3
\& krb5\-strength = {
\& }
.Ve
.PP
+which says to check passwords with CrackLib using the given path as the
+base path of the CrackLib dictionary. See \*(L"\s-1CONFIGURATION\*(R"\s0 below for
+details on the supported configuration options.
+.PP
\&\fBheimdal-strength\fR then expects the Heimdal password quality check
information on standard input, specifically:
.PP
rejecting the password on standard error and exit with a status of 0. If
some fatal error occurs, it will print that error to standard error and
exit with a non-zero status.
+.SH "CONFIGURATION"
+.IX Header "CONFIGURATION"
+The following \fIkrb5.conf\fR configuration options are supported:
+.IP "cracklib_maxlen" 4
+.IX Item "cracklib_maxlen"
+Normally, all passwords are checked with CrackLib if a CrackLib dictionary
+is defined. However, CrackLib's rules were designed for a world in which
+most passwords were four to eight characters long, and tends to spuriously
+reject a lot of passphrases. If this option is set to something other
+than its default of 0, passwords longer than that length bypass CrackLib
+checks. (Using a SQLite dictionary for longer passwords is strongly
+recommended.)
+.IP "minimum_different" 4
+.IX Item "minimum_different"
+If set to a numeric value, passwords with fewer than this number of unique
+characters will be rejected. This can be used to reject, for example,
+passwords that are long strings of the same character or repetitions of
+small numbers of characters, which may be too easy to guess.
+.IP "minimum_length" 4
+.IX Item "minimum_length"
+If set to a numeric value, passwords with fewer than that number of
+characters will be rejected, independent of any length restrictions in
+CrackLib. Note that this setting does not bypass the minimum length
+requirements in CrackLib itself.
+.IP "password_dictionary" 4
+.IX Item "password_dictionary"
+Specifies the base path to a CrackLib dictionary and enables password
+strength testing using CrackLib. The provided path should be the full
+path to the dictionary files, omitting the trailing \fI*.hwm\fR, \fI*.pwd\fR,
+and \fI*.pwi\fR extensions for the CrackLib dictionary.
+.IP "password_dictionary_cdb" 4
+.IX Item "password_dictionary_cdb"
+Specifies the base path to a \s-1CDB\s0 dictionary and enables \s-1CDB\s0 password
+dictionary lookups. The path must point to a CDB-format database whose
+keys are the known passwords or dictionary words. The values are ignored.
+You can use the \fBkrb5\-strength\-wordlist\fR utility to generate the \s-1CDB\s0
+database from a word list.
+.Sp
+The \s-1CDB\s0 dictionary lookups do not do the complex password mangling that
+CrackLib does. Instead, the password itself will be checked against the
+dictionary, and then variations of the password formed by removing the
+first character, the last character, the first and last characters, the
+first two characters, and the last two characters. If any of these
+strings are found in the \s-1CDB\s0 database, the password will be rejected;
+otherwise, it will be accepted, at least by this check.
+.Sp
+A CrackLib dictionary, a \s-1CDB\s0 dictionary, and a SQLite dictionary may all
+be configured at the same time or in any combination, in which case
+CrackLib will be run first, followed by \s-1CDB\s0 and then SQLite as
+appropriate.
+.IP "password_dictionary_sqlite" 4
+.IX Item "password_dictionary_sqlite"
+Specifies the base path to a SQLite dictionary and enables SQLite password
+dictionary lookups. The path must point to a SQLite 3 database with a
+table named \f(CW\*(C`passwords\*(C'\fR. This table should have two columns, \f(CW\*(C`password\*(C'\fR
+and \f(CW\*(C`drowssap\*(C'\fR, which, for each dictionary word, holds the word and the
+reversed form of the word. You can use the \fBkrb5\-strength\-wordlist\fR
+utility to generate the SQLite database from a word list.
+.Sp
+The SQLite dictionary lookups do not do the complex password mangling that
+CrackLib does, but they will detect and reject any password that is within
+edit distance one of a word in the dictionary, meaning that the dictionary
+word can be formed from the password by adding, deleting, or modifying a
+single character.
+.Sp
+A CrackLib dictionary, a \s-1CDB\s0 dictionary, and a SQLite dictionary may all
+be configured at the same time or in any combination, in which case
+CrackLib will be run first, followed by \s-1CDB\s0 and then SQLite as
+appropriate.
+.IP "require_ascii_printable" 4
+.IX Item "require_ascii_printable"
+If set to a true boolean value, rejects any password that contains
+non-ASCII characters or \s-1ASCII\s0 control characters. Spaces are allowed;
+tabs are not (at least assuming the \s-1POSIX C\s0 locale). No canonicalization
+or character set is defined for Kerberos passwords in general, so you may
+want to reject non-ASCII characters to avoid interoperability problems
+with computers with different default character sets or Unicode
+normalization forms.
+.IP "require_classes" 4
+.IX Item "require_classes"
+This option allows specification of more complex character class
+requirements. The value of this parameter should be one or more
+whitespace-separated rule. Each rule has the syntax:
+.Sp
+.Vb 1
+\& [<min>\-<max>:]<class>[,<class>...]
+.Ve
+.Sp
+where <class> is one of \f(CW\*(C`upper\*(C'\fR, \f(CW\*(C`lower\*(C'\fR, \f(CW\*(C`digit\*(C'\fR, or \f(CW\*(C`symbol\*(C'\fR. The
+symbol class includes all characters other than alphanumeric characters,
+including space. The listed classes must appear in the password.
+Separate multiple required classes with a comma (and no space).
+.Sp
+The character class checks will be done in whatever locale the plugin or
+password check program is run in, which will normally be the \s-1POSIX C\s0
+locale but may be different depending on local configuration.
+.Sp
+A simple example:
+.Sp
+.Vb 1
+\& require_classes = upper,lower,digit
+.Ve
+.Sp
+This requires all passwords contain at least one uppercase letter, at
+least one lowercase letter, and at least one digit.
+.Sp
+If present, <min> and <max> specify the minimum password length and
+maximum password length to which this rule applies. This allows one to
+specify character class requirements that change with password length.
+So, for example:
+.Sp
+.Vb 1
+\& require_classes = 8\-19:upper,lower 8\-15:digit 8\-11:symbol
+.Ve
+.Sp
+requires all passwords from 8 to 11 characters long contain all four
+character classes, passwords from 12 to 15 characters long contain upper
+and lower case and a digit, and passwords from 16 to 19 characters long
+contain both upper and lower case. Passwords longer than 20 characters
+have no character class restrictions. (This example is probably used in
+conjunction with minimum_length = 8.)
+.IP "require_non_letter" 4
+.IX Item "require_non_letter"
+If set to a true boolean value, the password must contain at least one
+character that is not a letter (uppercase or lowercase) or a space. This
+may be helpful in combination with passphrases; users may choose a stock
+English phrase, and this will force at least some additional complexity.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
-\&\fIkadm5\-strength\fR\|(3), \fIkpasswdd\fR\|(8), \fIkrb5.conf\fR\|(5)
+\&\fBkrb5\-strength\-wordlist\fR\|(1), \fBkadm5\-strength\fR\|(3), \fBkpasswdd\fR\|(8), \fBkrb5.conf\fR\|(5)
.PP
The \*(L"Password changing\*(R" section of the Heimdal info documentation
describes the interface that this program implements and how to configure
Heimdal to use it.
.PP
The current version of this program is available from its web page at
-<http://www.eyrie.org/~eagle/software/krb5\-strength/> as part of the
+<https://www.eyrie.org/~eagle/software/krb5\-strength/> as part of the
krb5\-strength package.
.SH "AUTHOR"
.IX Header "AUTHOR"
-Russ Allbery <rra@stanford.edu>
+Russ Allbery <eagle@eyrie.org>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
-Copyright 2010, 2013 The Board of Trustees of the Leland Stanford Junior
-University
+Copyright 2016 Russ Allbery <eagle@eyrie.org>
+.PP
+Copyright 2010, 2013\-2014 The Board of Trustees of the Leland Stanford
+Junior University
.PP
Copying and distribution of this file, with or without modification, are
permitted in any medium without royalty provided the copyright notice and
this notice are preserved. This file is offered as-is, without any
warranty.
+.PP
+SPDX-License-Identifier: \s-1FSFAP\s0
projects / kerberos / krb5-strength.git / blobdiff