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Rotate SQL Managed Instance enabled by Azure Arc customer-managed keytab

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This article describes how to rotate customer-managed keytabs for SQL Managed Instance enabled by Azure Arc. These keytabs are used to enable Active Directory logins for the managed instance.

Prerequisites:

Before you proceed with this article, you must have an active directory connector in customer-managed keytab mode and a SQL Managed Instance enabled by Azure Arc created.

How to rotate customer-managed keytabs in a managed instance

The following steps need to be followed to rotate the keytab:

  1. Get kvno value for the current generation of credentials for the SQL MI Active Directory account.
  2. Create a new keytab file with entries for the current generation of credentials. Specifically, the kvno value should match from step (1.) above.
  3. Update the new keytab file with new entries for the new credentials for the SQL MI Active Directory account.
  4. Create a kubernetes secret holding the new keytab file contents in the same namespace as the SQL MI.
  5. Edit the SQL MI spec to point the Active Directory keytab secret setting to this new secret.
  6. Change the password in the Active Directory domain.

We have provided the following PowerShell and bash scripts that will take care of steps 1-5 for you:

  • rotate-sqlmi-keytab.sh - This bash script uses ktutil or adutil (if the --use-adutil flag is specified) to generate the new keytab for you.
  • rotate-sqlmi-keytab.ps1 - This PowerShell script uses ktpass.exe to generate the new keytab for you.

Executing the above script would result in the following keytab file for the user arcsqlmi@CONTOSO.COM, secret sqlmi-keytab-secret-kvno-2-3 and namespace test:

KVNO Timestamp           Principal
---- ------------------- ------------------------------------------------------
   2 02/16/2023 17:12:05 arcsqlmiuser@CONTOSO.COM (aes256-cts-hmac-sha1-96) 
   2 02/16/2023 17:12:05 arcsqlmiuser@CONTOSO.COM (arcfour-hmac) 
   2 02/16/2023 17:12:05 MSSQLSvc/arcsqlmi.contoso.com@CONTOSO.COM (aes256-cts-hmac-sha1-96) 
   2 02/16/2023 17:12:05 MSSQLSvc/arcsqlmi.contoso.com@CONTOSO.COM (arcfour-hmac) 
   2 02/16/2023 17:12:05 MSSQLSvc/arcsqlmi.contoso.com:31433@CONTOSO.COM (aes256-cts-hmac-sha1-96) 
   2 02/16/2023 17:12:05 MSSQLSvc/arcsqlmi.contoso.com:31433@CONTOSO.COM (arcfour-hmac) 
   3 02/16/2023 17:13:41 arcsqlmiuser@CONTOSO.COM (aes256-cts-hmac-sha1-96) 
   3 02/16/2023 17:13:41 arcsqlmiuser@CONTOSO.COM (arcfour-hmac) 
   3 02/16/2023 17:13:41 MSSQLSvc/arcsqlmi.contoso.com@CONTOSO.COM (aes256-cts-hmac-sha1-96) 
   3 02/16/2023 17:13:41 MSSQLSvc/arcsqlmi.contoso.com@CONTOSO.COM (arcfour-hmac) 
   3 02/16/2023 17:13:41 MSSQLSvc/arcsqlmi.contoso.com:31433@CONTOSO.COM (aes256-cts-hmac-sha1-96) 
   3 02/16/2023 17:13:41 MSSQLSvc/arcsqlmi.contoso.com:31433@CONTOSO.COM (arcfour-hmac)

And the following updated-secret.yaml spec:

apiVersion: v1
kind: Secret
type: Opaque
metadata:
  name: sqlmi-keytab-secret-kvno-2-3
  namespace: test
data:
  keytab:
    <keytab-contents>

Finally, change the password for arcsqlmi user account in the domain controller for the Active Directory domain contoso.com:

  1. Open Server Manager on the domain controller for the Active Directory domain contoso.com. You can either search for Server Manager or open it through the Start menu.

  2. Go to Tools > Active Directory Users and Computers

    Screenshot of Active Directory Users and Computers.

  3. Select the user that you want to change password for. Right-click to select the user. Select Reset password:

    Screenshot of the control to reset the password for an Active Directory user account.

  4. Enter new password and select OK.

Troubleshooting errors after rotation

In case there are errors when trying to use Active Directory Authentication after completing keytab rotation, the following files in the arc-sqlmi container in the SQL MI pod are a good place to start investigating the root cause:

  • security.log file located at /var/opt/mssql/log - This log file has logs for SQL's interactions with the Active Directory domain.
  • errorlog file located at /var/opt/mssql/log - This log file contains logs from the SQL Server running on the container.
  • mssql.keytab file located at /var/run/secrets/managed/keytabs/mssql - Verify that this keytab file contains the newly updated entries and matches the keytab file created by using the scripts provided above. The keytab file can be read using the klist command i.e. klist -k mssql.keytab -e

Additionally, after getting the kerberos Ticket-Granting Ticket (TGT) by using kinit command, verify the kvno of the SQL user matches the highest kvno in the mssql.keytab file in the arc-sqlmi container. For example, for arcsqlmi@CONTOSO.COM user:

  • Get the kerberos TGT from the Active Directory domain by running kinit arcsqlmi@CONTOSO.COM. This will prompt a user input for the password for arcsqlmi user.
  • Once this succeeds, the kvno can be queried by running kvno arcsqlmi@CONTOSO.COM.

We can also enable debug logging for the kinit command by running the following: KRB5_TRACE=/dev/stdout kinit -V arcsqlmi@CONTOSO.COM. This increases the verbosity and outputs the logs to stdout as the command is being executed.

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