LDAP binding for node.js
JavaScript C++ Python Shell
Latest commit 2558b50 Mar 6, 2017 @jeremycx committed on GitHub Update README.md

README.md

ldap-client 3.X.X

OpenLDAP client bindings for Node.js. Requires libraries from http://www.openldap.org installed.

Now uses Nan to ensure it will build for all version of Node.js.

3.X is an API-breaking release, but it should be easy to convert to the new API.

NOTE: The module has been renamed to ldap-client as npm no longer accepts capital letters.

Contributing

Any and all patches and pull requests are certainly welcome.

Thanks to:

  • Petr Běhan
  • YANG Xudong
  • Victor Powell
  • Many other contributors

Dependencies

Node >= 0.8

Install

You must ensure you have the latest OpenLDAP client libraries installed from http://www.openldap.org

To install the latest release from npm:

npm install --save ldap-client

You will also require the LDAP Development Libraries (on Ubuntu, sudo apt-get install libldap2-dev)

For SASL authentication support the Cyrus SASL libraries need to be installed and OpenLDAP needs to be built with SASL support.

Reconnection

If the connection fails during operation, the client library will handle the reconnection, calling the function specified in the connect option. This callback is a good place to put bind()s and other things you want to always be in place.

You must close() the instance to stop the reconnect behavior.

During long-running operation, you should be prepared to handle errors robustly - there is no telling when the underlying driver will be in the process of automatically reconnecting. ldap.search() and friends will happily return a Timeout or Can't contact LDAP server error if the server has temporarily gone away. So, though you may want to implement your app in the new LDAP() callback, it's perfectly acceptable (and maybe even recommended) to ignore the ready callback in new LDAP() and proceed anyway, knowing the library will eventually connect when it is able to.

API

new LDAP(options, readyCallback);

Options are provided as a JS object:

var LDAP = require('ldap-client');

var ldap = new LDAP({
    uri:             'ldap://server',   // string
    validatecert:    false,             // Verify server certificate
    connecttimeout:  -1,                // seconds, default is -1 (infinite timeout), connect timeout
    base:            'dc=com',          // default base for all future searches
    attrs:           '*',               // default attribute list for future searches
    filter:          '(objectClass=*)', // default filter for all future searches
    scope:           LDAP.SUBTREE,      // default scope for all future searches
    connect:         function(),        // optional function to call when connect/reconnect occurs
    disconnect:      function(),        // optional function to call when disconnect occurs        
}, function(err) {
    // connected and ready    
});

The connect handler is called on initial connect as well as on reconnect, so this function is a really good place to do a bind() or any other things you want to set up for every connection.

var ldap = new LDAP({
    uri: 'ldap://server',
    connect: function() {
        this.bind({
            binddn: 'cn=admin,dc=com',
            password: 'supersecret'
        }, function(err) {
           ...
        });
    }
}

TLS

TLS can be used via the ldaps:// protocol string in the URI attribute on instantiation. If you want to eschew server certificate checking (if you have a self-signed cserver certificate, for example), you can set the verifycert attribute to LDAP.LDAP_OPT_X_TLS_NEVER, or one of the following values:

var LDAP=require('ldap-client');

LDAP.LDAP_OPT_X_TLS_NEVER  = 0;
LDAP.LDAP_OPT_X_TLS_HARD   = 1;
LDAP.LDAP_OPT_X_TLS_DEMAND = 2;
LDAP.LDAP_OPT_X_TLS_ALLOW  = 3;
LDAP.LDAP_OPT_X_TLS_TRY    = 4;

ldap.bind()

Calling open automatically does an anonymous bind to check to make sure the connection is actually open. If you call bind(), you will upgrade the existing anonymous bind.

ldap.bind(bind_options, function(err));

Options are binddn and password:

bind_options = {
    binddn: '',
    password: ''
}

Aliased to ldap.simplebind() for backward compatibility.

ldap.saslbind()

Upgrade the existing anonymous bind to an authenticated bind using SASL.

ldap.saslbind([bind_options,] function(err));

Options are:

  • mechanism - If not provided SASL library will select based on the best mechanism available on the server.
  • user - Authentication user if required by mechanism
  • password - Authentication user's password if required by mechanism
  • realm - Non-default SASL realm if required by mechanism
  • proxyuser - Authorization (proxy) user if supported by mechanism
  • securityproperties - Optional SASL security properties

All parameters are optional. For example a GSSAPI (Kerberos) bind can be initiated as follows:

	ldap.saslbind(function(err) { if(err) throw err; });

For details refer to the SASL documentation.

ldap.search()

ldap.search(search_options, function(err, data));

Options are provided as a JS object:

search_options = {
    base: 'dc=com',
    scope: LDAP.SUBTREE,
    filter: '(objectClass=*)',
    attrs: '*'
}

If one omits any of the above options, then sensible defaults will be used. One can also provide search defaults as part of instantiation.

Scopes are specified as one of the following integers:

var LDAP=require('ldap-client');

LDAP.BASE = 0;
LDAP.ONELEVEL = 1;
LDAP.SUBTREE = 2;
LDAP.SUBORDINATE = 3;
LDAP.DEFAULT = -1;

List of attributes you want is passed as simple string - join their names with space if you need more ('objectGUID sAMAccountName cname' is example of valid attrs filter). '*' is also accepted.

Results are returned as an array of zero or more objects. Each object has attributes named after the LDAP attributes in the found record(s). Each attribute contains an array of values for that attribute (even if the attribute is single-valued - having to check typeof() before you can act on /anything/ is a pet peeve of mine). The exception to this rule is the 'dn' attribute - this is always a single-valued string.

Example of search result:

[ { gidNumber: [ '2000' ],
  objectClass: [ 'posixAccount', 'top', 'account' ],
  uidNumber: [ '3214' ],
  uid: [ 'fred' ],
  homeDirectory: [ '/home/fred' ],
  cn: [ 'fred' ],
  dn: 'cn=fred,dc=ssimicro,dc=com' } ]

Attributes themselves are usually returned as strings. There is a list of known binary attribute names hardcoded in C++ binding sources. Those are always returned as Buffers, but the list is incomplete so far.

Paged Search Results

LDAP servers are usually limited in how many items they are willing to return - for example 1000 is Microsoft AD LDS default limit. To get around this limit for larger directories, you have to use paging (as long as the server supports it, it's an optional feature). To get paged search, add the "pagesize" attribute to your search request:

search_options = {
    ...,
    pagesize: n
}
ldap.search(search_options, on_data);

function on_data(err,data,cookie) {
  // handle errors, deal with received data and...
  if (cookie) { // more data available
    search_options.cookie = cookie;
    ldap.search(search_options, on_data);
  } else {
    // search is complete
  }
}

RootDSE

As of version 1.2.0 you can also read the rootDSE entry of an ldap server. To do so, simply issue a read request with base set to an empty string:

search_options = {
  base: '',
  scope: Connection.BASE,
  attrs: '+'
  // ... other options as necessary
}

ldap.findandbind()

ldap.findandbind(fb_options, function(err, data))

Options are exactly like the search options, with the addition of a "password" attribute:

fb_options = {
    base: '',
    filter: '',
    scope: '',
    attrs: '',
    password: ''
}

Calls the callback with the record it authenticated against as the data argument.

findandbind() does two convenient things: It searches LDAP for a record that matches your search filter, and if one (and only one) result is retured, it then uses a second connection with the same options as the primary connection to attempt to authenticate to LDAP as the user found in the first step.

The idea here is to bind your main LDAP instance with an "admin-like" account that has the permissions to search. Your (hidden) secondary connection will be used only for authenticating users.

In contrast, the bind() method will, if successful, change the authentication on the primary connection.

ldap.bind({
    binddn: 'cn=admin,dc=com',
    password: 'supersecret'
}, function(err, data) {
   if (err) {
       ...
   }
   // now we're authenticated as admin on the main connection
   // and thus have the correct permissions for search
   
   ldap.findandbind({
       filter: '(&(username=johndoe)(status=enabled))',
       attrs: 'username homeDirectory'
   }, function(err, data) {
      if (err) {
          ...
      }
      // our main connection is still cn=admin
      // but there's a hidden connection bound
      // as "johndoe"
      console.log(data[0].homeDirectory[0]);
   }
}

If you ensure that the "admin" user (or whatever you bind as for the main connection) can not READ the password field, then passwords will never leave the LDAP server -- all authentication is done my the LDAP server itself.

ldap.add()

ldap.add(dn, [attrs], function(err))

dn is the full DN of the record you want to add, attrs to be provided as follows:

var attrs = [
    { attr: 'objectClass',  vals: [ 'organizationalPerson', 'person', 'top' ] },
    { attr: 'sn',           vals: [ 'Smith' ] },
    { attr: 'badattr',      vals: [ 'Fried' ] }
]

ldap.modify()

ldap.modify(dn, [ changes ], function(err))

Modifies the provided dn as per the changes array provided. Ops are one of "add", "delete" or "replace".

var changes = [
    { op: 'add',
      attr: 'title',
      vals: [ 'King of Callbacks' ]
    }
]

ldap.rename()

ldap.rename(dn, newrdn, function(err))

Will rename the entry to the new RDN provided.

Example:

ldap.rename('cn=name,dc=example,dc=com', 'cn=newname')

ldap.remove()

ldap.remove(dn, function(err))

Deletes an entry.

Example:

ldap.remove('cn=name,dc=example,dc=com', function(err) {
  if (err) {
    // Could not delete entry
  }
});

Escaping

Yes, Virginia, there's such a thing as LDAP injection attacks.

There are a few helper functions to ensure you are escaping your input properly.

escapefn(type, template) Returns a function that escapes the provided parameters and inserts them into the provided template:

var LDAP = require('ldap-client');
var userSearch = LDAP.escapefn('filter', 
    '(&(objectClass=%s)(cn=%s))');

...
ldap.search({
    filter: userSearch('posixUser', username),
    scope: LDAP.SUBTREE
}, function(err, data) {
    ...
});

Since the escaping rules are different for DNs vs search filters, type should be one of 'filter' or 'dn'.

To escape a single string, LDAP.stringEscapeFilter:

var LDAP=require('ldap-client');
var user = "John O'Doe";

LDAP.stringEscapeFilter('(username=' + user + ')');
// ==> '(username=John O\'Doe)'

Note there is no function for string escaping a DN - DN escaping has special rules for escaping the beginning and end of values in the DN, so the best way to safely escape DNs is to use the escapefn with a template:

var LDAP = require('ldap-client');
var escapeDN = LDAP.escapefn('dn', 
    'cn=%s,dc=sample,dc=com');

...
var safeDN = escapeDN(" O'Doe");
// => "cn=\ O\'Doe,dc=sample,dc=com"

Bugs

Domain errors don't work properly. Domains are deprecated as of node 4, so I don't think I'm going to track it down. If you need domain handling, let me know.

TODO Items

Basically, these are features I don't really need myself.

  • Filter escaping