check_password.c - OpenLDAP pwdChecker library

2007-06-06 Michael Steinmann <[email protected]>
2008-01-30 Pierre-Yves Bonnetain <[email protected]>
2009        Clement Oudot <[email protected]> - LTB-project
2009        Jerome HUET - LTB-project

check_password.c is an OpenLDAP pwdPolicyChecker module used to check the
strength and quality of user-provided passwords.

This module is used as an extension of the OpenLDAP password policy controls,
see slapo-ppolicy(5) section pwdCheckModule.

check_password.c will run a number of checks on the passwords to ensure minimum
strength and quality requirements are met. Passwords that do not meet these
requirements are rejected.


Password checks
---------------
 - passwords shorter than 6 characters are rejected if cracklib is used (because
   cracklib WILL reject them).

 - syntactic checks controls how many different character classes are used
   (lower, upper, digit and punctuation characters). The minimum number of
   classes is defined in a configuration file. You can set the minimum for each
   class.

 - passwords are checked against cracklib if cracklib is enabled at compile
   time. It can be disabled in configuration file.

INSTALLATION
------------
Use the provided Makefile to build the module.

Compilation constants :

CONFIG_FILE : Path to the configuration file. 
              Defaults to /etc/openldap/check_password.conf

DEBUG : If defined, check_password will syslog() its actions.

Build dependencies
cracklib header files (link with -lcrack). The Makefile does not look for
cracklib; you may need to provide the paths manually.

Install into the slapd server module path.  Change the installation
path to match with the OpenLDAP module path in the Makefile.

The module may be defined with slapd.conf parameter "modulepath".

USAGE
-----
To use this module you need to add objectClass pwdPolicyChecker with an 
attribute 'pwdCheckModule: check_password.so' to a password policy entry.

The module depends on a working cracklib installation including wordlist files.
If the wordlist files are not readable, the cracklib check will be skipped
silently.

Note: pwdPolicyChecker modules are loaded on *every* password change operation.

Configuration
-------------
The configuration file (/etc/openldap/check_password.conf by default) contains
parameters for the module. If the file is not found, parameters are given their
default value.

The syntax of the file is :

parameter value

with spaces being delimiters. Parameter names ARE case sensitive (this may
change in the future).

Current parameters :

-  useCracklib: integer. Default value: 1. Set it to 0 to disable cracklib verification.
   It has no effect if cracklib is not included at compile time.

-  minPoints: integer. Default value: 3. Minimum number of quality points a new
   password must have to be accepted. One quality point is awarded for each character
   class used in the password.

- minUpper: integer. Defaut value: 0. Minimum upper characters expected.

- minLower: integer. Defaut value: 0. Minimum lower characters expected.

- minDigit: integer. Defaut value: 0. Minimum digit characters expected.

- minPunct: integer. Defaut value: 0. Minimum punctuation characters expected.

Logs
----
If a user password is rejected by an OpenLDAP pwdChecker module, the user will
*not* get a detailed error message, this is by design.

Typical user message from ldappasswd(5):
  Result: Constraint violation (19)
  Additional info: Password fails quality checking policy

A more detailed message is written to the server log.

Server log:
  check_password_quality: module error: (check_password.so)
  Password for dn=".." does not pass required number of strength checks (2 of 3)


Caveats
-------
Runtime errors with this module (such as cracklib configuration problems) may
bring down the slapd process.

Use at your own risk.


TODO
----
* use proper malloc function, see ITS#4998


HISTORY
-------
* 2009-10-30 Clement OUDOT - LTB-project
  Version 1.1
   - Apply patch from Jerome HUET for minUpper/minLower/minDigit/minPunct

* 2009-02-05 Clement Oudot <[email protected]> - LINAGORA Group
  Version 1.0.3
  - Add useCracklib parameter in config file (with help of Pascal Pejac)
  - Prefix log messages with "check_password: "
  - Log what character type is found for quality checking

* 2008-01-31 Pierre-Yves Bonnetain <[email protected]>
  Version 1.0.2
  - Several bug fixes.
  - Add external config file

* 2007-06-06 Michael Steinmann <[email protected]>
  Version 1.0.1
  - add dn to error messages

* 2007-06-02 Michael Steinmann <[email protected]>
  Version 1.0