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Current state: Accepted
Discussion thread: here
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
From Kafka documentation
"By default, the SASL user name will be the primary part of the Kerberos principal. One can change that by
setting sasl.kerberos.principal.to.local.rules to a customized rule in server.properties. The format of
sasl.kerberos.principal.to.local.rules is a list where each rule works in the same way as
the auth_to_local in Kerberos configuration file (krb5.conf)
Each rules starts with RULE: and contains an expression in the format [n:string](regexp)s/pattern/replacement/g."
Currently, username translations based on rules are done maintaining the case of the input principal. For example, given the rule
However, this may not be desired given how different operating system handle usernames, whereas some are case-sensitive
and some are case-insensitive. For example, Linux is case-sensitive and Windows is case-insensitive.
To help with this issue, the rule can support to force the translated result to be all lower case.
We propose to extend "sasl.kerberos.principal.to.local.rules" config rule format/syntax by supporting an optional "/L" (toLowerCase) at the end of the rule. Since usernames are locale insensitive strings, we propose to use Locale.ENGLISH for the case conversion
For example, given the rules
However, it must be noted that this does not affect how pattern matches on input and therefore that will still be case-sensitive.
Compatibility, Deprecation, and Migration Plan
This is an extension to the existing sasl.kerberos.principal.to.local.rules format and there will be no impact on existing users.