Import ldap.filter in security_manager override

[litesh1998]

Fix LDAP login failure caused by missing ldap.filter import

closes: #68224

When LDAP authentication is enabled, Airflow may return a 500 Internal Server Error during login.

The failure occurs in the LDAP search path where ldap.filter.escape_filter_chars() is called without importing the ldap.filter submodule first. With recent versions of python-ldap, importing ldap alone does not automatically expose the filter module, resulting in:

AttributeError: module 'ldap' has no attribute 'filter'

This change explicitly imports ldap.filter before it is used by the LDAP authentication flow.

Reproduction

1. Configure Airflow with LDAP authentication.
2. Install a recent version of python-ldap (e.g. 3.4.7).
3. Attempt to log in using an LDAP user.
4. Airflow returns HTTP 500 with:

AttributeError: module 'ldap' has no attribute 'filter'

Root Cause

ldap.filter.escape_filter_chars() is referenced during LDAP user lookup, but the ldap.filter module is not imported. Recent versions of python-ldap require the submodule to be imported explicitly.

Fix

Import ldap.filter before using ldap.filter.escape_filter_chars().

Testing

• Reproduced the issue on:

  • Apache Airflow 3.2.2
  • apache-airflow-providers-fab 3.6.5
  • python-ldap 3.4.7
  • Python 3.12

• Verified that LDAP authentication succeeds after the change.

• Verified that the 500 Internal Server Error no longer occurs during login.

[boring-cyborg]

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[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.

[dheerajturaga]

I just hit this issue on 3.2.2. Thanks for the fix @litesh1998 and congrats on your first contribution!