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https://issues.apache.org/jira/browse/HBASE-2420?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12854706#action_12854706
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Andrew Purtell commented on HBASE-2420:
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It's about trust for enforcement of isolation. HBase can run as a single
principal across the whole cluster from the HDFS perspective no matter the
details of HBase internal security model. So as you put it the "hbase" user
would own the hfiles.
bq. Otherwise we'd have to do fine grained ACLs on all HFiles, and granting a
user access to a table would require granting them access to the files involved
in that table only.
That's one option.
Another is a scheme where HBase users are mapped to HBase roles which are
mapped to HDFS users which are aggregated as HDFS groups:
HBase user -> HBase role -> HDFS user -> HDFS group
This can provide some flexibility for various configurations from
simple-but-no-isolation to complex-but-paranoid. This scheme would have the
DFSClients in the region servers operate with multiple delegation tokens from
HDFS in a pass through manner.
The trade off is some complexity for being able to get some assurance of
isolation even if HBase is "broken" in some way.
> [DAC] HDFS and ZK access delegation
> -----------------------------------
>
> Key: HBASE-2420
> URL: https://issues.apache.org/jira/browse/HBASE-2420
> Project: Hadoop HBase
> Issue Type: Sub-task
> Reporter: Andrew Purtell
>
> HBase security will be in part layered on top of HDFS security, and whatever
> ZK offers as well. For sake of discussion we presume both HDFS and ZK use a
> Kerberos based authentication and authorization model, as proposed in the
> Hadoop Security Architecture document. There are two basic options for that,
> fine- or coarse-grained:
> h4. Coarse
> There could simply be a single delegation token granted to a HBase cluster
> from HDFS and ZK for all operations on behalf of all possible users of the
> HBase cluster. From the perspective of HDFS and ZK, there is only a single
> principal for each cluster.
> h4. Fine
> The HBase master could manage and renew HDFS and ZK delegation tokens on
> behalf of users authenticated to HBase via Kerberos. So when a client
> authenticates via KRB to the HMaster when looking up region locations as the
> first step to any HBase access, the HMaster would get a delegation token from
> the NameNode on behalf of the user. (The user would then hand the delegation
> token to the HRegionServers to allow access to store data via their embedded
> DFSClients.) It would be ideal if ZooKeeper authentication and authorization
> could tie in seamlessly. For example, at the same time the HMaster is getting
> a delegation token for the user for HDFS, it could also get another token for
> ZK on behalf of the user. A wrinkle here is token renewal. If a user
> transacts with a HRegionServer with an expired token, the HRegionServer would
> renew the token (or ask the HMaster to renew the token if superuser should
> not be delegated from HMaster to HRegionServer) transparently with the
> NameNode on behalf of the user. Something like that would be necessary on the
> ZK side also. To support this model, the HRegionServers and HMaster (or just
> HMaster) must act as a superuser principal capable of impersonating user
> principals. Presumably, with the ZK ensemble also. Thus ZK, like HDFS, must
> provide methods for a superuser to act on behalf of others. HDFS will have
> this facility.
> There are pros and cons for each approach. Coarse obviously is much more
> simple to implement and reason about. But it requires more trust in HBase to
> maintain isolation between users than the fine-grained approach. With the
> fine-grained approach, the regionservers get HDFS and ZK delegation tokens
> from the HBase client and this allows a policy where files and znodes created
> by one user+group cannot be read or written by another at the DFS (store)
> level or the ZK level. Assume group level permissions. Thus you can reason
> about isolation further down the stack, not just from client->HBase, but
> client->HBase->HDFS and client->ZK and client->HBase->ZK.
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