Writing rules and headers

Lemonldap::NG manages applications by their hostname (Apache’s virtualHosts). Rules are used to protect applications, headers are HTTP headers added to the request to give datas to the application (for logs, profiles,…).

Attention

Note that variables designed by $xx correspond to the name of the exported variables or macro names except for $ENV{<cgi-header>} which correspond to CGI header ($ENV{REMOTE_ADDR} for example).

Available $ENV variables

The %ENV table provides:

• all headers in CGI format (User-Agent becomes HTTP_USER_AGENT)

• some CGI variables depending on the context:

  • For portal: all CGI standard variables (you can add custom headers using fastcgi_param with Nginx),

  • For Apache handler: REMOTE_ADDR, QUERY_STRING, REQUEST_URI, SERVER_PORT, REQUEST_METHOD,

  • For Nginx handler: all variables given by fastcgi_param commands.

• For portal:

  • $ENV{urldc} : Origin URL before Handler redirection, in cleartext

  • $ENV{_url} : Origin URL before Handler redirection, base64 encoded

See also extended functions.

Rules

A rule associates a regular expression to a Perl boolean expression or a keyword.

Examples:

Goal	Regular expression	Rule
Restrict /admin/ directory to user bart.simpson	^/admin/
Restrict /js/ and /css/ directory to authenticated users	^/(css|js)/	accept
Deny access to /config/ directory	^/config/	deny
Do not restrict /public/	^/public/	skip
Do not restrict /skip/ and restrict other to authenticated users	^/skip/	$ENV{REQUEST_URI} =~ /skip/ ? skip : 1
Makes authentication optional, but authenticated users are seen as such (that is, user data are sent to the app through HTTP headers)	^/forum/	unprotect
Restrict access to the whole site to users that have the LDAP description field set to “LDAP administrator” (must be set in exported variables)	default

The “default” access rule is used if no other access rule match the current URL.

Tip

See the rules examples page for a few common use cases

Tip

• Comments can be used to order your rules: rules are applied in the alphabetical order of comment (or regexp in there is no comment). See security chapter to learn more about writing good rules.

• See performances to know how to use macros and groups in rules.

Rules can also be used to intercept logout URL:

Goal	Regular expression	Rule
Logout user from Lemonldap::NG and redirect it to http://intranet/	^/index.php?logout	logout_sso http://intranet/
Logout user from current application and redirect it to the menu (Apache only)	^/index.php?logout	logout_app https://auth.example.com/
Logout user from current application and from Lemonldap::NG and redirect it to http://intranet/ (Apache only)	^/index.php?logout	logout_app_sso http://intranet/

Danger

logout_app and logout_app_sso rules are not available on Nginx, only on Apache.

By default, user will be redirected on portal if no URL defined, or on the specified URL if any.

Attention

Only current application is concerned by logout_app* targets. Be careful with some applications which doesn’t verify Lemonldap::NG headers after having created their own cookies. If so, you can redirect users to a HTML page that explain that it is safe to close browser after disconnect.

Rules based on authentication level

LLNG set an “authentication level” during authentication process. This level depends on authentication backend used by this user. Default values are:

• 0 for Null

• 1 for CAS, old OpenID-2, Facebook,…

• 2 for web-form based authentication (LDAP, DBI,…)

• 3 for Yubikey

• 4 for Kerberos

• 5 for SSL

There are three ways to impose users a higher authentication level:

• writing a rule based on authentication level: $authenticationLevel > 3

• set a minimum level in virtual host options (default value for ALL access rules)

• a minimum authentication level can be set for each URI access rule. Useful if URI are protected by different types of handler (AuthBasic -> level 2, Main -> level set by authentication backend).

Tip

Instead of returning a 403 code, “minimum level” returns user to a form that explain that a higher level is required and propose to reauthenticate himself.

Using regexp capture in rules

If URL regexp captures something (using parenthesis), you can use them in the corresponding rule using $_rulematch[1]. Example: only user can access to its personal area:

• Regexp: /^public_html/(\w+)(/.*)?$

• Rule: $uid eq $_rulematch[1]

$_rulematch is an array that contains all captured strings. First index is 1.

Warning

This feature requires Perl ≥ 5.25.7

Headers

Headers are associations between an header name and a perl expression that returns a string. Headers are used to give user data to the application.

Examples:

Goal	Header name	Header value
Give the uid (for accounting)	Auth-User	$uid
Give a static value	Some-Thing	“static-value”
Give display name	Display-Name	$givenName.” “.$surName
Give a non ascii data	Display-Name

As described in performances chapter, you can use macros, local macros,…

Attention

• Since many HTTP servers refuse non ascii headers, it is recommended to use encode_base64() function to transmit those headers

• Don’t forget to add an empty string as second argument to encode_base64 function to avoid a “newline” characters insertion in result

• Header names must contain only letters and “-” character. With Nginx, you can bypass this restriction by using underscores_in_headers on; directive

Tip

By default, SSO cookie is hidden. So protected applications cannot retrieve SSO session key. But you can forward this key if absolutely needed:

Session-ID => $_session_id

Available functions

In addition to macros and name, you can use some functions in rules and headers:

• LLNG extended functions

• Your custom functions

Wildcards in hostnames

Since 2.0, a wildcard can be used in virtualhost name (not in aliases !): *.example.com matches all hostnames that belong to example.com domain. Version 2.0.9 improves this and allows better wildcards such as test-*.example.com or test-%.example.com. The % wilcard doesn’t match subdomains.

Even if a wildcard exists, if a virtualhost is explicitly declared, this rule is applied. Example with precedence order for test.sub.example.com:

1. test.sub.example.com

2. test%.sub.example.com

3. test*.sub.example.com

4. %.sub.example.com

5. *.sub.example.com

6. *.example.com (%.example.com does not match test.sub.example.com)