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
2011        Trevor Vaughan <[email protected]> - Onyx Point, Inc.

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.

This was originally packaged as
ltb-project-openldap-ppolicy-check-password-1.1. However, Onyx Point made a
great number of changes and improvements and has re-labeled it
ppolicy-check-password. All original license restrictions and user
privileges apply.

The original code can be downloaded from https://ltb-project.org/wiki/download.


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.

 - password checking can optionally be set to ensure that no more than a given
   number of characters from a character set can be used in a row.

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.

LDEBUG : If defined, check_password will print its actions to the console.

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".

On Red Hat systems, you will need to download the openldap source RPM that you want to build against and perform the following steps:

 - rpm -i <openldap source RPM>
 - rpmbuild -bc <rpm_build_dir>/SPECS/openldap.spec
 - cd <openldap-password-module_dir>
 - mkdir openldap-<version>
 - cd openldap-<version>
 - src_dir="<rpm_build_dir>/BUILD/openldap-<version>/openldap-<version>/"
 - cp -r $src_dir/build-servers $src_dir/include \
         $src_dir/libraries $src_dir/servers .

Then, the Makefile should work properly.


TESTING
-------
An application is provided to build tests for check_password.c. The Makefile
will produce 'cpass' which will run the tests defined in check_password_test.c.
It is highly suggested that you use this if you are going to modify
check_password.c.

You'll need to run cpass with: LD_LIBRARY_PATH=. ./cpass


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 :

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

-  min_points: 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.

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

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

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

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

- max_consecutive_per_class: integer. Default value: 5. Maximum number of
  characters that can appear consecutively from a given character class. 0
  disables.


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
* get rid of GOTO's


HISTORY
-------
* 2011-01-28 - Trevor Vaughan <[email protected]> - Onyx Point, Inc.
  Version 1.2
   - Ensure the the configuration file is only read once per run.
   - Add max_consecutive_per_class.
   - Add LDEBUG flag for local debugging.
   - Add test code and update Makefile

* 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