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Authorizing MongoDB Atlas users against Okta's LDAP Groups

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Authorizing MongoDB Atlas users against Okta's LDAP Groups

Published: Sep 22, 2020 / Last updated: Nov 19, 2020 / By Andrew Doering.

Introduction

As could be understood by my recent blog postings, we have been migrating to an Okta LDAP entry point as our primary LDAP service. Working towards a Cloud Centric first expectation. As could be imagined, there have been some issues popping up while moving infrastructure and making necessary changes. This describes one of these issues. One of these issues was the way that MongoDB Atlas handled LDAP look ups during the authorization process.

Issue

When running MongoDB Versions equal to or lower than, 3.6.19, 4.0.20, 4.2.9 and using the Mongo Query Template for Authorization on LDAP Interface :

ou=groups,dc=<okta-instance-id>,dc=okta,dc=com??sub?(&(objectClass=groupofUniqueNames)(uniqueMember={USER}))

We would receive failed messages in the shell for MongoDB Atlas. While on the Okta side, we saw several rate limit messages.

MongoDB did group lookups in an inefficient way due to excluding the DN value and/or specifying a specific CN value from the lookup and attempting to broadly search for a single user within the group that the lookup is being performed on. Binding on every attempt to make a connection to Okta’s LDAP Interface. Effectively hammering Okta’s LDAP server - which has API limitations outlined here. There was an issue present on MongoDB’s public facing issue tracker (however, not realizing this before hand - we would never have known to look through 47968+ potential issues.)

We reached out to Okta to request an increase to the API limit in the mean time while continuing to test around the issue which they performed on the following:

/api/v1/users/{id}/groups | READ / WRITE | EXACT_MATCH | 1000 / minute

However, even with the API increase, we still ended up running into events in the Okta System Log resulting in group lookups not being completed due to rate limiting, and on the MongoDB/Authorization side - failed authorization results.

We ultimately raised a ticket internally with MongoDB Support, to ask if back porting the fix introduced into 4.4.* would be possible, however there was not an ETA at the present time.

Solution

After several weeks of waiting for the issue to be back ported. It finally has! Beginning with MongoDB Atlas Versions 3.6.20, 4.0.21, and 4.2.10 you can use Okta’s LDAP Interface Okta mastered Groups for Authorization.

The comments written directly by the PoC in charge of the incident filed:

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    Please note that in order to utilize the Okta-optimized codepath, you MUST request the DN attribute in the authorization query explicitly.

    Here's the example configuration (swap the `yourdomain` below to your okta tenant domain, as well as be aware of the `your_service_account` ):


    LDAP server: yourdomain.ldap.okta.com
    Server Port: 636
    Bind Username: uid=your_service_account@domain.tld,dc=yourdomain,dc=okta,dc=com
    User To DN Mapping: [ { "match": "(.+)", "substitution": "uid={0},ou=users,dc=yourdomain,dc=okta,dc=com" } ]
    Query Template: ou=groups,dc=yourdomain,dc=okta,dc=com?dn?one?(&(objectClass=groupofUniqueNames)(uniqueMember={USER}))

Once configured, you should be able to use Okta’s LDAP Interface in MongoDB Atlas and have successful Authorization results!

Update 2020/11/17

After writing and utilizing this more. We ran into issues with Mongo Compass, connecting to Mongo Atlas with Okta as the backend through the LDAPi. These issues are not present with mongo cli tools.

After doing a decent amount of research and requesting Splunk logs from Okta, we came to the conclusion that Mongo logs out after each request/connection/session initiated. They do not keep a constant session open while the Compass software is connected to the clusters.

In addition to this, instead of doing a single request to the cluster, multiple requests are made (usually 1 to 2) to each shard. The end result is that this spams the end user with (4 - 8) MFA requests.

Our Company Default Okta authentication policy are already setup in a relaxed way:

  • 7 days for a known factor session
  • 2 hour session lifetime
  • Prompt Mode in “per session” choice

When going through Mongo support, they requested us to change Prompt Mode from “Per Session” to “Per Device”. This wouldn’t be very effective, as “Per Device” relies mostly on session cookies or device context. Leaving the issue still present with no fix as of writing the update.

So far we are waiting for this to proceed on Mongo, and have opened up a case with Okta to potentially resolve this going forward. For references if anyone else experiences similar issues:

  • Mongo Case is: 00693506
  • Okta case is: 00992849

If you would like to or prefer to reach out to the vendors for potential solutions if I don’t post them here. Or leave a comment below.

Update 2020/11/19

MongoDB provided an update to us to use the following connection URI:

mongodb+srv://ldapuser:str0ngpassword@mymongo.xxx.xxx/test?authMechanism=PLAIN&maxPoolSize=1&readPreference=secondary&authSource=%24external&appname=MongoDB%20Compass&ssl=false

This does seem to work, notice the addition of &maxPoolSize=1, but, there are two concerns that I have with this:

  • &ssl=false
  • What limitations/implications does the addition of the value above have on the overall performance on mongo compass?

Initial reactions would be that Compass may not display/return all results within the cluster, as they may not have replicated over to the connected shard instance. I tested initially with &ssl=true without any major issue, so it seems like that the &ssl=false aspect may just be an error/mistype.

While I would consider this a workaround for the time being, there are definitely improvements that need to be made into the outbound LDAP requests being made on the Mongo side, or alternatively, Okta needs to implement more flexibility around the LDAP Interface itself.