Hive does not respect auth_to_local rules. Backport for HIVE-12981

I'm using the following auth_to_local rules:

RULE:[1:$1@$0](.*@\QDOMAIN-B\E$)s///L
RULE:[1:$1@$0](.*@\QDOMAIN-A\E$)s/@\QDOMAIN-A\E$///L
RULE:[2:$1@$0](.*@\QDOMAIN-A\E$)s/@\QDOMAIN-A\E$//
DEFAULT

An example on how they works:

Kerberos UPN            -> Hadoop ShortName
-------------------------------------------
userB@DOMAIN-B          -> userb@domain-b
userA@DOMAIN-A          -> usera
hdfs/hostname@DOMAIN-A  -> hdfs

I've written these rules to mimic SSSD's behaviour (system service to map Active Directory users to local linux account that's gaining a lot of traction in RHEL7).

My issue is that Hive does NOT respect the first rule: userB@DOMAIN-B is incorrectly mapped to userB instead of userb@domain-b. With this mapping the ShellBasedGroupMapping fails to resolve the correct groups and without the groups authorization in Sentry will not work.

Here's a short example:

$ klist
Ticket cache: FILE:/tmp/krb5cc_0
Default principal: userB@DOMAIN-B

$ beeline --color=true -u "jdbc:hive2://hs2hostname:10000/default;principal=hive/
Transaction isolation: TRANSACTION_REPEATABLE_READ
Beeline version 1.1.0-cdh5.14.0 by Apache Hive
0: jdbc:hive2://hs2hostname> set hive.access.subject.name;
---------------------------------------+
| set |
---------------------------------------+
| hive.access.subject.name=userb |
---------------------------------------+
1 row selected (0.093 seconds)
0: jdbc:hive2://hs2hostname> set hive.sentry.subject.name;
---------------------------------------+
| set |
---------------------------------------+
| hive.sentry.subject.name=userb |
---------------------------------------+
1 row selected (0.021 seconds)

This has also some security implications: userA@DOMAIN-B is incorrectly mapped to usera - a different users!!

HDFS had the same issue which has been fixed in HADOOP-12751 (backported in CDH5.10+).
With a little bit of googling I've found the following Hive issue HIVE-12981 that describes my issue exactly.

Could you guys please backport the patch to CDH 5.x??