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Status

Current state:   [One of "Under Discussion", "Accepted", "Rejected"]

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]
 

JIRA:

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

Describe the problems you are trying to solve.

Public Interfaces

Briefly list any new interfaces that will be introduced as part of this proposal or any existing interfaces that will be removed or changed. The purpose of this section is to concisely call out the public contract that will come along with this feature.

A public interface is any change to the following:

• Binary log format

• The network protocol and api behavior

• Any class in the public packages under clientsConfiguration, especially client configuration

  • org/apache/kafka/common/serialization

  • org/apache/kafka/common

  • org/apache/kafka/common/errors

  • org/apache/kafka/clients/producer

  • org/apache/kafka/clients/consumer (eventually, once stable)

• Monitoring

• Command line tools and arguments

• Anything else that will likely break existing users in some way when they upgrade

Proposed Changes

Describe the new thing you want to do in appropriate detail. This may be fairly extensive and have large subsections of its own. Or it may be a few sentences. Use judgement based on the scope of the change.

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users?
• If we are changing behavior how will we phase out the older behavior?
• If we need special migration tools, describe them here.
• When will we remove the existing behavior?

Rejected Alternatives

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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

Code Block
"RULE:[2:$1@$0](.*@EXAMPLE.COM)s/@.*//"

Code Block
If the source string is joe-qa/host@EXAMPLE.COM, the result is joe-qa If the source string is JOE-QA/host@EXAMPLE.COM, the result is JOE-QA If the source string is Joe-QA/host@EXAMPLE.COM, the result is Joe-QA

However, this may not be desired given how different operating system handle usernames, where 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.

Proposed Changes

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

"RULE:[2:$1@$0](joe-qa-.*@EXAMPLE.COM)s/.*/JOE-QA//L",
"RULE:[2:$1@$0](JOE-QA-.*@EXAMPLE.COM)s/.*/JOE-QA-UPPER//L",
"RULE:[2:$1@$0](.*@EXAMPLE.COM)s/@.*///L"

If the source string is joe-qa-cl1/host@EXAMPLE.COM, the result will be joe-qa
If the source string is JOE-QA-cl1/host@EXAMPLE.COM, the result will be joe-qa-upper
If the source string is joe_user/host@EXAMPLE.COM, the result will be joe_user
If the source string is JOE_USER/host@EXAMPLE.COM, the result will be joe_use

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.