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https://issues.apache.org/jira/browse/HDFS-13040?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16334397#comment-16334397
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Daryn Sharp commented on HDFS-13040:
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I don’t think this looks right. At a minimum, the short user should not be
used or it may cause issues in a multi-realm environment. Using a proxy user
also means you are allowing the client privs to directly access the external
service used by the NN which may not be intended.
The client's credentials are clearly valid or it couldn’t get a RemoteException
from the NN. The client doesn’t transmit credentials, so the server-side doAs
context cannot authenticate to any external service. For it ever to work,
which it shouldn’t, there is a bug causing implicit fallback to the login
user’s credentials. Whether the client principal matches the NN’s principal
should be irrevelant.
The underlying problem needs to be more concisely stated. Let's start with the
exception the NN receives that triggers the long-winded RemoteException to the
client. Presumably the edit log is a REST based? Probably using the buggy
AuthenticatedURL?
BTW, you can actually use minikdc to login 2 distinct principals for a test.
> Kerberized inotify client fails despite kinit properly
> ------------------------------------------------------
>
> Key: HDFS-13040
> URL: https://issues.apache.org/jira/browse/HDFS-13040
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 2.6.0
> Environment: Kerberized, HA cluster, iNotify client, CDH5.10.2
> Reporter: Wei-Chiu Chuang
> Assignee: Wei-Chiu Chuang
> Priority: Major
> Attachments: HDFS-13040.001.patch, TransactionReader.java
>
>
> This issue is similar to HDFS-10799.
> HDFS-10799 turned out to be a client side issue where client is responsible
> for renewing kerberos ticket actively.
> However we found in a slightly setup even if client has valid Kerberos
> credentials, inotify still fails.
> Suppose client uses principal h...@example.com,
> namenode 1 uses server principal hdfs/nn1.example....@example.com
> namenode 2 uses server principal hdfs/nn2.example....@example.com
> *After Namenodes starts for longer than kerberos ticket lifetime*, the client
> fails with the following error:
> {noformat}
> 18/01/19 11:23:02 WARN security.UserGroupInformation:
> PriviledgedActionException as:h...@gce.cloudera.com (auth:KERBEROS)
> cause:org.apache.hadoop.ipc.RemoteException(java.io.IOException): We
> encountered an error reading
> https://nn2.example.com:8481/getJournal?jid=ns1&segmentTxId=8662&storageInfo=-60%3A353531113%3A0%3Acluster3,
>
> https://nn1.example.com:8481/getJournal?jid=ns1&segmentTxId=8662&storageInfo=-60%3A353531113%3A0%3Acluster3.
> During automatic edit log failover, we noticed that all of the remaining
> edit log streams are shorter than the current one! The best remaining edit
> log ends at transaction 8683, but we thought we could read up to transaction
> 8684. If you continue, metadata will be lost forever!
> at
> org.apache.hadoop.hdfs.server.namenode.RedundantEditLogInputStream.nextOp(RedundantEditLogInputStream.java:213)
> at
> org.apache.hadoop.hdfs.server.namenode.EditLogInputStream.readOp(EditLogInputStream.java:85)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.readOp(NameNodeRpcServer.java:1701)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.getEditsFromTxid(NameNodeRpcServer.java:1763)
> at
> org.apache.hadoop.hdfs.server.namenode.AuthorizationProviderProxyClientProtocol.getEditsFromTxid(AuthorizationProviderProxyClientProtocol.java:1011)
> at
> org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.getEditsFromTxid(ClientNamenodeProtocolServerSideTranslatorPB.java:1490)
> at
> org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
> at
> org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:617)
> at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1073)
> at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2216)
> at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2212)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:415)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1920)
> at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2210)
> {noformat}
> Typically if NameNode has an expired Kerberos ticket, the error handling for
> the typical edit log tailing would let NameNode to relogin with its own
> Kerberos principal. However, when inotify uses the same code path to retrieve
> edits, since the current user is the inotify client's principal, unless
> client uses the same principal as the NameNode, NameNode can't do it on
> behalf of the client.
> Therefore, a more appropriate approach is to use proxy user so that NameNode
> can retrieving edits on behalf of the client.
> I will attach a patch to fix it. This patch has been verified to work for a
> CDH5.10.2 cluster, however it seems impossible to craft a unit test for this
> fix because the way Hadoop UGI handles Kerberos credentials (I can't have a
> single process that logins as two Kerberos principals simultaneously and let
> them establish connection)
> A possible workaround is for the inotify client to use the active NameNode's
> server principal. However, that's not going to work when there's a namenode
> failover, because then the client's principal will not be consistent with the
> active NN's one, and then fails to authenticate.
> Credit: this bug was confirmed and reproduced by [~pifta] and [~r1pp3rj4ck]
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