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Status
Current state: ["Under Discussion"]
Discussion thread: here
JIRA: here
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Motivation
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
"RULE:[2:$1@$0](.*@EXAMPLE.COM)s/@.*//"
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, 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.
Reference
Proposed Changes
extend "sasl.kerberos.principal.to.local.rules" config rule format/syntax by supporting an optional "/L" (toLowerCase) at the end of the rule.
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.