Apachecon Big Data EU 2105 talk on Hadoop and Kerberos; needs to viewed with slide animation to make sense

1. © Hortonworks Inc. 2015
Hadoop and Kerberos:
The madness beyond the
gate
Steve Loughran
stevel@hortonworks.com
@steveloughran
2015

2. Page 2
Me: Before Kerberos

3. © Hortonworks Inc.
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Me: After Kerberos

4. © Hortonworks Inc.
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HP Lovecraft Kerberos
Evil lurking in New England MIT Project Athena
Ancient, inhuman deities Kerberos Domain Controller
Manuscripts to drive the reader
insane
IETF RFC 4120
Entities never spoken of aloud UserGroupInformation
Doomed explorers of darkness You

5. © Hortonworks Inc. 2015
Leave now if you want
to retain your life of
naïve innocence
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6. © Hortonworks Inc.
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7. © Hortonworks Inc. 2015
export HADOOP_USER="root"
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8. © Hortonworks Inc. 2015
Modern Hadoop clusters
are locked down
through Kerberos
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9. © Hortonworks Inc. 2015
Discover Kerberos
before Kerberos
discovers you
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10. © Hortonworks Inc. 2015
Kerberos:
the gateway to hell
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11. © Hortonworks Inc.
This is not a metaphor
Art: Andrés Álvarez Iglesias

12. © Hortonworks Inc. 2015
KP
Kerberos is the gateway
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Authentication Service
Ticket Granting Service
Principal
user@REALM
user/hostname@REALM
(P, TGS, n1)
{KP.TGS, n1}KP, {ticket(P,TGS)} KTGS
Ticket(P, TGS) =
(TGS, P, tstart, tend, KPT)
KP
{KP.S, n2}KP, {ticket(P,S)} KS
{auth(P)}KP.TGS,{ticket(P,TGS)}KTGS,S,n2
KTGS
Kerberos Domain ControllerClient
auth(P)KP.TGS = {P, time)}KP.TGS

13. © Hortonworks Inc
Every service is a principal
alice@REALM
bob@REALM
oozie/ooziehost@REALM
namenode/nn1@REALM
hdfs/_HOST@REALM
hdfs/r04s12@REALM
hdfs/r04s13@REALM
yarn/_HOST@REALM
yarn/r04s12@REALM
HTTP/_HOST@REALM
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short names:
alice
bob
oozie
namenode
hdfs
yarn
HTTP

14. © Hortonworks Inc.
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Entering the darkness

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17. © Hortonworks Inc. 2015
HDFS Bootstrap: Kerberos Login
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shared keytab in /etc/hadoop
log in to kerberos
datanode/_HOST@REALM
tickets for TGS
namenode/nn@REALM

18. © Hortonworks Inc. 2015
HDFS Bootstrap: DNs register with NN
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shared keytab in /etc/hadoop
DN registration
Ticket for namenode/nn@REALM
ExportedBlockKeys
Request ticket for namenode/nn@REALM
namenode/nn@REALM
datanode/_HOST@REALM

19. © Hortonworks Inc.
Hadoop Tokens
• Issued and tracked by individual services
(HDFS, WebHDFS, Timeline Server, YARN RM, …)
• Grant some form of access:
Block tokens, Delegation Tokens
• Can be passed on to other processes
• Renewable via service APIs (RPC, HTTP)
• Revocable in server via service APIs
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read: O'Malley 2009, Hadoop Security Architecture

20. © Hortonworks Inc. 2015
HDFS IO: Block Tokens
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alice@REALM
Obtain ticket for namenode/nn@REALM
BlockToken
BlockToken
BlockToken: userId, (BlockPoolId, BlockId), keyId, expiryDate, access-modes
namenode/nn@REALM
open("file")

21. © Hortonworks Inc. 2015
service/host@REALM
Delegation Tokens delegate access
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alice@REALM BlockToken
HDFS
Delegation
Token
BlockToken
HDFS
Delegation
Token
HDFS
Delegation
Token
namenode/nn@REALM
Token
Obtain ticket for namenode/nn@REALM
Request delegation
token

22. © Hortonworks Inc. 2015
Launch Context
YARN app launch
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alice@REALM
HDFS
Delegation
Token
HDFS
resourcemanager/rm@REALM
nodemanager/_HOST@REALMalice
Launch Context
AM/RM
HDFS AM/RM
HDFS
HDFS
HDFS
AM/RM
namenode/nn@REALM
Obtain ticket for resourcemanager/rm@REALM
Request delegation
token
AM/RM
Token
Obtain tickvet for namenode/nn@REALM
AM/RM'
AM/RM'
AM/RM'
Refresh AM/RM

23. © Hortonworks Inc
That which must not be named: UGI
if(!UserGroupInformation.isSecurityEnabled()) {
stayInALifeOfNaiveInnocence();
} else {
sufferTheEnternalPainOfKerberos();
}
UserGroupInformation.checkTGTAndReloginFromKeytab();
UserGroupInformation.getLoginUser() // principal logged in as
UserGroupInformation.getCurrentUser() // principal acting as
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24. © Hortonworks Inc
UGI.doAs()
UserGroupInformation bob =
UserGroupInformation.createProxyUser("bob",
UserGroupInformation.getLoginUser());
FileSystem userFS = bob.doAs(
new PrivilegedExceptionAction<FileSystem>() {
public FileSystem run() throws Exception {
return FileSystem.get(FileSystem.getDefaultUri(), conf);
}
});
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25. © Hortonworks Inc
Hadoop RPC
@KerberosInfo(serverPrincipal = "my.kerberos.principal")
public interface MyRpc extends VersionedProtocol { … }
public class MyRpcPolicyProvider extends PolicyProvider {
public Service[] getServices() {
return new Service[] {
new Service("my.protocol.acl", MyRpc.class)
};
}
}
public class MyRpcSecurityInfo extends SecurityInfo { … }
META-INF/services/org.apache.hadoop.security.SecurityInfo
org.example.rpc.MyRpcSecurityInfo
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26. © Hortonworks Inc
IPC Server: get the current user identity
Messages.KillResponse killContainer(Messages.KillRequest request) {
UserGroupInformation callerUGI;
try {
callerUGI = UserGroupInformation.getCurrentUser();
} catch (IOException ie) {
LOG.info("Error getting UGI ", ie);
AuditLogger.logFailure("UNKNOWN", "Error getting UGI");
throw RPCUtil.getRemoteException(ie);
}
…
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27. © Hortonworks Inc
IPC Server: Authorize
String user = callerUGI.getShortUserName();
if (!checkAccess(callerUGI, MODIFY)) {
AuditLog.unauthorized(user,
KILL_CONTAINER_REQUEST,
"User doesn't have permissions to " + MODIFY);
throw RPCUtil.getRemoteException(
new AccessControlException(
+ user + " lacks access "
+ MODIFY_APP.name()));
}
AuditLog.authorized(user, KILL_CONTAINER_REQUEST)
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28. © Hortonworks Inc. 2015
SASL: RFC4422
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29. © Hortonworks Inc.
REST: SPNEGO (+ Delegation tokens)
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• Jersey + java.net
• httpclient? “if lucky it'll work”
HADOOP-11825: Move timeline client
Jersey+Kerberos+UGI support into a public implementation

30. © Hortonworks Inc.
Testing
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31. © Hortonworks Inc.
Error messages to fear
Art: Andrés Álvarez Iglesias
Failure unspecified at GSS-API level (Checksum failed)
No valid credentials provided (Failed to find any Kerberos tgt)
Server not found in Kerberos database
Clock skew too great
Principal not found
No valid credentials provided (Illegal key size)

32. © Hortonworks Inc.
Topics Avoided Not Covered
• Zookeeper
• JAAS
• Trying to use HTTPS in a YARN application
• Trying to use Full REST in a YARN application
• System properties to debug Kerberos & SPNEGO
• Group management
• HADOOP_PROXY_USER
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33. © Hortonworks Inc.
gitbook.com/@steveloughran
Questions?
Art: Andrés Álvarez Iglesias

34. © Hortonworks Inc.
Zookeeper
• SASL to negotiate security:
System.setProperty("zookeeper.sasl.client", "true");
• Permissions are not transitive down the tree
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List<ACL> perms = new ArrayList<>();
if (UserGroupInformation.isSecurityEnabled()) {
perms(new ACL(ZooDefs.Perms.ALL, ZooDefs.Ids.AUTH_IDS));
perms.add(new ACL(ZooDefs.Perms.READ,ZooDefs.Ids.ANYONE_ID_UNSAFE));
} else {
perms.add(new ACL(ZooDefs.Perms.ALL, ZooDefs.Ids.ANYONE_ID_UNSAFE));
}
zk.createPath(path, null, perms, CreateMode.PERSISTENT);

35. © Hortonworks Inc
System Properties for debugging
-Dsun.security.krb5.debug=true
-Dsun.security.spnego.debug=true
export HADOOP_JAAS_DEBUG=true
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36. © Hortonworks Inc.
Services
• RPC authentication via annotations & metadata in JAR
• YARN Web UIs: rely on RM proxy for authentication
• Authentication != Authorization
• Add audit logs on service endpoints
• YARN services: come up with a token refresh strategy:
keytab everywhere; keytab in AM; update from client
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37. © Hortonworks Inc.
JAAS
• Java Authentication and Authorization Service
• Core Kerberos classes and types (Principal)
• Text files to configure
–Different for different JVMs
–Need to double escape for windows paths
• UGI handles setting up a JAAS context & logging in
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38. © Hortonworks Inc.
Glossary
• Simple Authentication and Security Layer (SASL)
• GSSAPI Generic Security Service Application Program
Interface (RFC-2743+ others)
• JAAS: Java Authentication and Authorization Service
• Simple and Protected GSSAPI Negotiation Mechanism
(SPNEGO)
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