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From "Grzegorz Grzybek (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ZOOKEEPER-3138) Potential race condition with Quorum Peer mutual authentication via SASL
Date Wed, 05 Sep 2018 15:38:00 GMT
Grzegorz Grzybek created ZOOKEEPER-3138:
-------------------------------------------

             Summary: 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: quorum
    Affects Versions: 3.4.13
            Reporter: Grzegorz Grzybek


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}
org.apache.zookeeper.server.quorum.auth.SaslQuorumServerCallbackHandler.handleNameCallback(SaslQuorumServerCallbackHandler.java:101)
org.apache.zookeeper.server.quorum.auth.SaslQuorumServerCallbackHandler.handle(SaslQuorumServerCallbackHandler.java:82)
com.sun.security.sasl.digest.DigestMD5Server.validateClientResponse(DigestMD5Server.java:589)
com.sun.security.sasl.digest.DigestMD5Server.evaluateResponse(DigestMD5Server.java:244)
org.apache.zookeeper.server.quorum.auth.SaslQuorumAuthServer.authenticate(SaslQuorumAuthServer.java:100)
org.apache.zookeeper.server.quorum.QuorumCnxManager.handleConnection(QuorumCnxManager.java:467)
org.apache.zookeeper.server.quorum.QuorumCnxManager.receiveConnection(QuorumCnxManager.java:386)
org.apache.zookeeper.server.quorum.QuorumCnxManager$QuorumConnectionReceiverThread.run(QuorumCnxManager.java:422)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
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]:
{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";
};
...
{noformat}

All peers use the same credentials, 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.*

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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