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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