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https://issues.apache.org/jira/browse/ZOOKEEPER-3138?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Grzegorz Grzybek updated ZOOKEEPER-3138:
----------------------------------------
Component/s: security
leaderElection
> Potential race condition with Quorum Peer mutual authentication via SASL
> ------------------------------------------------------------------------
>
> Key: ZOOKEEPER-3138
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3138
> Project: ZooKeeper
> Issue Type: Bug
> Components: leaderElection, quorum, security
> Affects Versions: 3.4.13
> Reporter: Grzegorz Grzybek
> Priority: Major
>
> I'm in the process of reconfiguring the ensemble to use mutual quorum peer
> authentication using SASL (ZOOKEEPER-1045).
> In order to understand the impact on my code, I've checked _how it works_.
> Now I'm running & debugging
> {{org.apache.zookeeper.server.quorum.auth.QuorumDigestAuthTest#testValidCredentials()}}
> test case.
> I have now six threads (3 peers contacting each other):
> * "QuorumConnectionThread-[myid=0]-2@1483" prio=5 tid=0x2b nid=NA runnable
> * "QuorumConnectionThread-[myid=0]-3@1491" prio=5 tid=0x36 nid=NA runnable
> * "QuorumConnectionThread-[myid=1]-1@1481" prio=5 tid=0x2d nid=NA runnable
> * "QuorumConnectionThread-[myid=1]-4@1505" prio=5 tid=0x3c nid=NA runnable
> * "QuorumConnectionThread-[myid=2]-2@1495" prio=5 tid=0x37 nid=NA runnable
> * "QuorumConnectionThread-[myid=2]-4@1506" prio=5 tid=0x3d nid=NA runnable
> at this point of invocation:
> {noformat}
> java.lang.Thread.State: RUNNABLE
> at
> org.apache.zookeeper.server.quorum.auth.SaslQuorumServerCallbackHandler.handleNameCallback(SaslQuorumServerCallbackHandler.java:101)
> at
> org.apache.zookeeper.server.quorum.auth.SaslQuorumServerCallbackHandler.handle(SaslQuorumServerCallbackHandler.java:82)
> at
> com.sun.security.sasl.digest.DigestMD5Server.validateClientResponse(DigestMD5Server.java:589)
> at
> com.sun.security.sasl.digest.DigestMD5Server.evaluateResponse(DigestMD5Server.java:244)
> at
> org.apache.zookeeper.server.quorum.auth.SaslQuorumAuthServer.authenticate(SaslQuorumAuthServer.java:100)
> at
> org.apache.zookeeper.server.quorum.QuorumCnxManager.handleConnection(QuorumCnxManager.java:467)
> at
> org.apache.zookeeper.server.quorum.QuorumCnxManager.receiveConnection(QuorumCnxManager.java:386)
> at
> org.apache.zookeeper.server.quorum.QuorumCnxManager$QuorumConnectionReceiverThread.run(QuorumCnxManager.java:422)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> at java.lang.Thread.run(Thread.java:748)
> {noformat}
> which is this line:
> {code:java}
> private void handleNameCallback(NameCallback nc) {
> // check to see if this user is in the user password database.
> if (credentials.get(nc.getDefaultName()) == null) {
> LOG.warn("User '{}' not found in list of DIGEST-MD5 authenticateable
> users.",
> nc.getDefaultName());
> return;
> }
> nc.setName(nc.getDefaultName());
> /* >>> */ userName = nc.getDefaultName(); /* <<< */
> }
> {code}
> each pair of threads is operating on single instance of
> {{org.apache.zookeeper.server.quorum.auth.SaslQuorumServerCallbackHandler#userName}}.
> In the stack trace we have both shared and local variables/fields:
> *
> {{o.a.z.server.quorum.QuorumCnxManager.QuorumConnectionReceiverThread#sock}}
> is thread-specific (ok)
> * {{o.a.z.server.quorum.QuorumCnxManager#authServer}} is peer-specific
> (instance of {{o.a.z.server.quorum.auth.SaslQuorumAuthServer}}) but without a
> state that changes
> * {{javax.security.sasl.SaslServer}} is thread-specific (ok) - this instance
> is created to handle sasl authentication, but is created using peer-specific
> JAAS subject (which is ok) and peer-specific
> {{o.a.z.server.quorum.auth.SaslQuorumAuthServer#serverLogin.callbackHadler}}
> {color:red}which is potentially a problem{color}
> Each (out of six) thread handles different connection, but each pair (for
> given QuorumPeer) calls
> {{o.a.z.server.quorum.auth.SaslQuorumServerCallbackHandler#handleNameCallback()}}
> which modifies shared (peer-specific) field - {{userName}}.
> I understand that [according to the example from
> Wiki|https://cwiki.apache.org/confluence/display/ZOOKEEPER/Server-Server+mutual+authentication]
> all peers may use the same credentials (in simplest case).
> But the "userName" comes from data sent by each peer, like this:
> {noformat}
> charset=utf-8,\
> username="test",\
> realm="zk-quorum-sasl-md5",\
> nonce="iBqYWtaCrEE013S6Dv6xiOsR9uX2l/qKZcEZ1pm2",\
> nc=00000001,\
> cnonce="LVaL9XYFjNxVBPCjPewXjEBsj9GuwIfBN/RXsKt5",\
> digest-uri="zookeeper-quorum/zk-quorum-sasl-md5",\
> maxbuf=65536,\
> response=dd4e9e2115ec2e304484d5191f3fc771,\
> qop=auth,\
> authzid="test"
> {noformat}
> *And I can imagine such JAAS configuration for DIGEST-MD5 SASL algorithm,
> that each peer uses own credentials and is able to validate other peers'
> specific credentials.*:
> {noformat}
> QuorumServer {
> org.apache.zookeeper.server.auth.DigestLoginModule required
> user_peer1="peer1";
> user_peer2="peer2";
> user_peer3="peer3";
> };
> QuorumLearner1 {
> org.apache.zookeeper.server.auth.DigestLoginModule required
> username="peer1"
> password="peer1";
> };
> QuorumLearner2 {
> org.apache.zookeeper.server.auth.DigestLoginModule required
> username="peer2"
> password="peer2";
> };
> QuorumLearner2 {
> org.apache.zookeeper.server.auth.DigestLoginModule required
> username="peer3"
> password="peer3";
> };
> {noformat}
> Isn't it a race condition? Like this (having 3 peers):
> ||thread handling peer 2 → peer 1 connection||thread handling peer 3 → peer 1
> connection||
> |sets o.a.z.s.q.auth.SaslQuorumServerCallbackHandler#userName to "peer2"| |
> | |sets o.a.z.s.q.auth.SaslQuorumServerCallbackHandler#userName to "peer3"|
> |sets PasswordCallback.password to
> o.a.z.s.q.auth.SaslQuorumServerCallbackHandler#credentials.get("peer3")| |
> | | continues ...|
> |com.sun.security.sasl.digest.DigestMD5Base#generateResponseValue() generates
> expected response using:
> * username: "peer2"
> * password of user "peer3"| |
> Please verify.
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