An LDAP v3 Client Library for Dart

The Lightweight Directory Access Protocol (LDAP) is a protocol for accessing directories.

An LDAP directory is organised as a hierarchy of entries, where one or more root entries are allowed. Each entry can be identified by a distinguished name, which is an ordered sequence of attribute/value pairs. Each entry contains a set of attributes. Attributes have a name and are associated with a set of one or more values (i.e. attributes can be repeated and are unordered).

This library can be used to query (search for and compare entries) and modify (add, delete and modify) LDAP directories.

This library supports the LDAP v3 protocol, which is defined in IETF RFC 4511.

Breaking changes from previous versions are described at the bottom of this page.

Using dartdap

Examples

To perform operations on an LDAP directory, the basic process is:

1. Create an LDAP connection (LdapConnection).
2. Perform LDAP operations (search, add, modify, modifyDN, compare, delete).
3. Close the connection (close).

The following examples are provided:

• main.dart - A basic sample using the LdapConnection() class
• pool.dart - Connection pool example
• paged_search.dart - demonstrates how to use the paged search control

Note: As of version 0.5.0, An experimental connection pool is also provided. Please read pool.md.

Create an LDAP connection

The first step is to instantiate an LdapConnection object using its constructor.

These properties of the connection can be changed from their defaults:

• hostname (defaults to "localhost");
• ssl: false is plain LDAP, true is LDAPS (LDAP over SSL/TLS) (defaults to false);
• port: port number (defaults to standard port for LDAP/LDAPS: 389 or 636);
• bindDN: distinguished name for binding, null means unauthenticated (default is null);
• password: password for binding.

These properties can be set using named parameters to the constructor, or with the setProtocol and setAuthentication methods.

Perform LDAP operations

This example performs a search operation.

The search method returns a Future to a SearchResult object, from which a stream of SearchEntry objects can be obtained. The results are obtained by listening to the stream (which in the example is done using the "await for" syntax).

The SearchEntry contains the entry's distinguished name and the attributes returned. The dn is a String. The attributes is a Map from the name of the attribute (a String) to an Attribute.

An Attribute has a values member, which returns a Set of the values of the attribute. It is a Set because LDAP allows attributes to have multiple values. It also has a name member, which is the name of the attribute as a String.

Close the connection

When finished with the connection, call the close method.

In the above example, the close is performed in the finally section, to ensure it gets closed even if an exception is thrown.

The close method returns a Future, which completes when the connection is completely closed.

Searching

A search request returns a stream of SearchResults.

There is EXPERIMENTAL support for search result references (referrals)

If SearchResult.referrals[] is not empty, it is an array of strings which are the DNs to repeat the search request. The SDK does not automatically follow referrals.

There are two search methods:

• ldap.search takes a dart Filter object.
• ldap.query takes an https://tools.ietf.org/html/rfc2254 string to construct the filter

Adding entries

try {
  var attrs = {
    "objectClass": ["organizationalUnit"],
    "description": "Example organizationalUnit entry"
  };

  await ldap.add("ou=Engineering,dc=example,dc=com", attrs);

} on LdapResultEntryAlreadyExistsException catch (_) {
  // cannot add entry because it already exists

} on LdapException catch (e) {
  // some other problem

}

Modifying entries

try {
  var mod1 = new Modification.replace("description", ["Engineering department"]);
  await ldap.modify("ou=Engineering,dc=example,dc=com", [mod1]);

} on LdapResultObjectClassViolationException catch (_) {
  // cannot modify entry because it would violate the schema rules

} on LdapException catch (e) {
  // some other problem
}

Moving entries

try {
  await ldap.modifyDN(oldDN, newDN);

} on LdapException catch (e) {
  // some other problem
}

Comparing entries

try {
  r = await ldap.compare("ou=Engineering,dc=example,dc=com",
                         "description", "Engineering Dept");
  if (r.resultCode == ResultCode.COMPARE_FALSE) {

  } else if (r.resultCode == ResultCode.COMPARE_TRUE) {

  } else {
    assert(false);
  }

} on LdapException catch (e) {
  // some other problem
}

Deleting entries

try {
  await ldap.delete("ou=Business Development,dc=example,dc=com");

} on LdapResultNoSuchObjectException catch (_) {
  // entry did not exist to delete

} on LdapException catch (e) {
  // some other problem
}

Connecting and authenticating

The LdapConnection provides a basic connection to the LdapServer. The caller is responsible for performing any Bind() operations, handling any disconnects, or retrying on failure.

As of 0.5.0, a protoype LdapConnectionPool() is provided that handles some of the these tasks. The pool implements the Ldap() interface, and will attempt to bind() with the provided credentials, and will retry a connection if the server is not available.

The Connection pool is still experimental, and provides only basic functionality.

See the documentation of LdapConnection and LdapConnectionPool for more details.

Exceptions

Methods in the package throws exceptions which are subclasses of the LdapException abstract class.

See the documentaiton of LdapException for more details.

Logging

This package uses the Dart logging package for logging.

The logging is mainly useful for debugging the package.

Loggers

The following loggers are used:

Logger: ldap.control

• finest = parsing of controls

Logger: ldap.session

• warnings = certificate issues
• fine = connections successfully established, and closing them
• finer = details about attempts to establish a connection

Logger: ldap.send.ldap for the LDAP messages sent.

• fine = LDAP messages sent.
• finest = details of LDAP message construction

Logger: ldap.send.bytes for the raw bytes sent to the socket. Probably only useful when debugging the dartdap package.

• severe = errors/exceptions when sending
• fine = number of raw bytes sent

Logger: ldap.recv.ldap for the LDAP messages receive (i.e. received ASN.1 objects processed as LDAP messages).

• fine = LDAP messages received.
• finer = LDAP messages processing.

Logger: ldap.recv.asn1 for the ASN.1 objects received (i.e. parsed from the raw bytes received). Probably only useful when debugging the dartdap package.

• fine = ASN.1 messages successfully parsed from the raw bytes
• finest = shows the actual bytes making up the value of the ASN.1 message

Logger: ldap.recv.bytes for the raw bytes received from the socket. Probably only useful when debugging the dartdap package.

• fine = number of raw bytes read
• finer = parsing activity of converting the bytes into ASN.1 objects
• finest = shows the actual bytes received and the number in the buffer to parse

Logging Examples

To take advantage of the hierarchy of loggers, enable hierarchicalLoggingEnabled and set the logging level on individual loggers. If the logging level is not explicitly set on a logger, it is inherited from its parent. The root logger is the ultimate parent; and its logging level is initally Level.INFO.

For example, to view high level connection and LDAP messages send/received:

import 'package:logging/logging.dart';

...

Logger.root.onRecord.listen((LogRecord rec) {
  print('${rec.time}: ${rec.loggerName}: ${rec.level.name}: ${rec.message}');
});

hierarchicalLoggingEnabled = true;

new Logger("ldap.session").level = Level.FINE;
new Logger("ldap.send.ldap").level = Level.FINE;
new Logger("ldap.recv.ldap").level = Level.FINE;

To debug messages received:

new Logger("ldap.recv.ldap").level = Level.ALL;
new Logger("ldap.recv.asn1").level = Level.FINER;
new Logger("ldap.recv.bytes").level = Level.FINE;

Note: in the above examples: SHOUT, SEVERE, WARNING and INFO will still be logged (except for those loggers and their children where the level has been set to Level.OFF). To disable those log messages change the root logger from its default of Level.INFO to Level.OFF.

For example, to suppress all log messages (including suppressing SHOUT, SEVERE, WARNING and INFO):

Logger.root.level = Level.OFF;

Or leave the root level at the default and only disable logging from the package:

new Logger("ldap").level = Level.OFF;

Breaking changes

0.6.2

LdapConnectionPool has been refactored.

0.6.0

• The library user is now responsible for waiting for all LDAP operations to complete before calling connection.close()

0.5.0

There are many breaking changes in 0.5.0. The most signifcant are:

• dartdap is now null safe.
• The LdapConnection class no longer handles automatic retry or error handling. A new LdapConnectionPool has been introduced that will host this functionality.

See the CHANGELOG.md

Version 0.4.0

• LdapConnection.search new signature is search(attributeName,searchExpression)
• A new LdapConnection.query(attr,searchQuery) supports rfc2254 query filters.

Version 0.1.x to 0.2.x

• LdapConnection changed to support automatic connection/reconnections (and authentication when needed). This allows connections to be safely reused (i.e. kept open for later operations without having to re-open the connection). Previously, there was no guarantee a previously working connection would still be working when an LDAP operation was performed later: it could have been disconnected by intermittent network errors or LDAP server timeouts. Previously, the only safe way to use a connection was to open one for each LDAP operation (which is very inefficient) or to always expect LDAP operations could fail and to open a new connection if it fails (verbose and inelegant code).

• The search method returns a Future to a SearchResult. Previously, it returned the SearchResult synchronously. This change was necessary because (with the introduction of automatic connections) a search could cause the connection to be opened, and bind request to be sent, before the search request is actually sent.

• Renaming of other classes and methods to consistently follow the Dart naming conventions. For example, LDAPConnection becomes LdapConnection, LDAPResult becomes LdapResult, LDAPUtil becomes LdapUtil.

• Exception raised if a bad certificate is encountered when opening a SSL/TLS connection. Provide a bad certificate handler function, if the application wants to override the default behaviour. Other than for testing, accepting bad certificates is a security risk: so, the default behaviour is the safer option.

• Internal classes hidden from public interface (e.g. ConnectionManager, LDAPUtil).

• LDAPConfiguration removed.

Version 0.0.x to 0.1.x

• Library is now called "dartdap" instead of "ldap_client". There was a disconnect in the naming: package X was imported, but only library Y was imported. That would have been ok if it had multiple libraries, but it currently only contains one publicly visible library. Also, many of the classes could apply an LDAP server too.

• LDAPException renamed to LdapException to follow the Dart naming conventions.

• New exception classed defined for all the LDAP result error conditions. All LDAP operations now throws these new exceptions. Instead of checking the resultCode in the LDAPResult returned by the LDAP operations, catch the new exceptions.

• SocketException exceptions are now being internally caught and thrown as LdapSocketException objects. This make it easier to detect common failure conditions. Instead of catching SocketException, catch the new LdapSocketException or one of its subclasses.

• LDAPConfiguration is deprecated. Programs should use whatever configuration mechanism they normally use (e.g. databases or configuration files) rather than having to use a special configuration mechanism only for dartdap (and still having to use the other configuration mechanism for the rest of the program). It is also unsafe due to a race condition that could occur if multiple connections are being established.

• Internal organisation of libraries/imports/exports have been cleaned up. This should not be noticable by existing code, unless it was directly referencing those internal libraries or files.

References

https://tools.ietf.org/html/rfc4511