KB4538382 - Implement support for Kerberos constrained delegation in SQL Server 2019 on Linux

Applies to: SQL Server 2019 on Linux


This change implements theS4U2Self/S4U2Proxy protocol that uses the Generic Security Service (GSS) API on top of the MIT Kerberos library to allowfor Kerberosconstrained delegation (but *not* resourcebased constrained delegation). This functionality requires setting aprivileged Active Directory (AD) account through mssql-conf by executing the following on the SQLServer Linux host:
sudo/opt/mssql/bin/mssql-conf set network.privilegedadaccount mssql
and setting up constrained delegationagainst the SQL Server SPNs for any authentication protocol on the ADcontroller, i.e. if using Powershell commands:
Set-ADAccountControl -Identity mssql -TrustedToAuthForDelegation $true
Set-ADUser -Identity mssql -Add @{'msDS-AllowedToDelegateTo'=@('MSSQLSvc/netbiosname:1433', 'MSSQLSvc/machine_fqdn:1433')}
It also requires to changethe Kerberos settings on the SQL Server Linux host to generate forwardabletickets by default, i.e. in /etc/krb5.conf one should see:
 forwardable = true


This improvement is included in the following cumulative update for SQL Server:
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