LDAP Authentication for OpenSearch — Troubleshooting Guide 🔧

When LDAP is involved, things rarely fail loudly — they fail quietly, which is worse 😄. Here are the most common issues you’ll run into with OpenSearch + LDAP setups, and what they actually mean.

❌ No user 6069 found

This is the classic one.

Even though the bind succeeds, OpenSearch can’t see the user:

No user 6069 found
Authentication finally failed for 6069

What’s happening: LDAP connection is fine, but the search is returning nothing.

Check in this order:

userbase in config.yml

• Make sure it actually covers where the user lives in Microsoft Active Directory
• DC=pabc,DC=int works broadly
• Narrow OUs like OU=Finance,... will silently miss users outside that branch

user search filter

• For AD, this is the safe bet: (sAMAccountName={0})
• Avoid Jinja-style placeholders like {{username}} — they won’t work here

Bind user permissions

• Your bind DN must have read access to the subtree you’re searching
• If in doubt, assume it’s permissions until proven otherwise

💥 NumberFormatException on startup

NumberFormatException: For input string: "//HODC2.pabc.int"

Cause: You accidentally included the protocol in hosts.

Fix:

hosts:
  - HODC2.pabc.int:389   # correct

❌ Don’t do this:

ldap://HODC2.pabc.int
ldaps://HODC2.pabc.int

OpenSearch expects host:port only. SSL is controlled separately via enable_ssl.

🔐 Empty truststore / CA file error

Happens when you enable LDAPS but don’t give OpenSearch anything to trust:

Empty file path for truststore_filepath

Fix one of these:

• Set: pemtrustedcas_filepath: /path/to/ca.pem
• OR use cluster-wide truststore in opensearch.yml

Without this, TLS handshake will fail immediately.

🚫 verify_hostnames works on false, fails on true

If this breaks:

verify_hostnames: true

It usually means your certificate doesn’t match the hostname.

Root cause:

• The AD certificate does NOT include HODC2.pabc.int in SAN or CN

Fix options:

• ✅ Proper fix: reissue cert with correct SAN
• ⚠️ Temporary workaround: verify_hostnames: false

🧠 Config changes not taking effect

This one trips everyone.

You edit config.yml… restart… nothing changes 😐

Why:

OpenSearch Security stores everything inside its own internal index (.opendistro_security). After initial bootstrap, disk config is no longer used automatically.

Fix:

Push config properly: securityadmin.sh -f config.yml -t config

Then clear cache: DELETE _plugins/_security/api/cache

Otherwise you’re just staring at stale config and wondering why nothing moved.

That’s the core set of LDAP pain points you’ll hit most often. Once these are clear, everything else is usually just wiring and patience 😄