Jenkins failing to run after attempting to implement AD login

Question

I have a jenkins instance that I tried to set up with Active Directory. None of the users could log in with any credentials after, so I went onto the server and removed the Active Directory plugin in an attempt to remove the configuration and rebooted the server. I'm now seeing the following error

com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.active_directory.ActiveDirectorySecurityRealm
at com.thoughtworks.xstream.mapper.DefaultMapper.realClass(DefaultMapper.java:79)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.DynamicProxyMapper.realClass(DynamicProxyMapper.java:55)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.PackageAliasingMapper.realClass(PackageAliasingMapper.java:88)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.ClassAliasingMapper.realClass(ClassAliasingMapper.java:79)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.ArrayMapper.realClass(ArrayMapper.java:74)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.SecurityMapper.realClass(SecurityMapper.java:71)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at hudson.util.XStream2$CompatibilityMapper.realClass(XStream2.java:379)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at hudson.util.xstream.MapperDelegate.realClass(MapperDelegate.java:43)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at com.thoughtworks.xstream.mapper.CachingMapper.realClass(CachingMapper.java:48)
at hudson.util.RobustReflectionConverter.determineType(RobustReflectionConverter.java:461)
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:327)
Caused: jenkins.util.xstream.CriticalXStreamException:           hudson.plugins.active_directory.ActiveDirectorySecurityRealm : hudson.plugins.active_directory.ActiveDirectorySecurityRealm
---- Debugging information ----
message             :     hudson.plugins.active_directory.ActiveDirectorySecurityRealm
cause-exception     : com.thoughtworks.xstream.mapper.CannotResolveClassException
cause-message       : hudson.plugins.active_directory.ActiveDirectorySecurityRealm
class               : hudson.model.Hudson
required-type       : hudson.model.Hudson
converter-type      : hudson.util.RobustReflectionConverter
path                : /hudson/securityRealm
line number         : 15
version             : not available
-------------------------------
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:356)
at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:270)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1189)
at hudson.util.XStream2.unmarshal(XStream2.java:161)
at hudson.util.XStream2.unmarshal(XStream2.java:132)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1173)
at hudson.XmlFile.unmarshal(XmlFile.java:178)
Caused: java.io.IOException: Unable to read /data/jenkins/config.xml
at hudson.XmlFile.unmarshal(XmlFile.java:181)
at hudson.XmlFile.unmarshal(XmlFile.java:161)
at jenkins.model.Jenkins.loadConfig(Jenkins.java:3005)
at jenkins.model.Jenkins.access$1200(Jenkins.java:304)
at jenkins.model.Jenkins$14.run(Jenkins.java:3104)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:169)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:296)
at jenkins.model.Jenkins$5.runTask(Jenkins.java:1068)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:214)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) 
at java.lang.Thread.run(Thread.java:748)
Caused: org.jvnet.hudson.reactor.ReactorException
at org.jvnet.hudson.reactor.Reactor.execute(Reactor.java:282)
at jenkins.InitReactorRunner.run(InitReactorRunner.java:48)
at jenkins.model.Jenkins.executeReactor(Jenkins.java:1102)
at jenkins.model.Jenkins.<init>(Jenkins.java:904)
at hudson.model.Hudson.<init>(Hudson.java:85)
at hudson.model.Hudson.<init>(Hudson.java:81)
at hudson.WebAppMain$3.run(WebAppMain.java:233)
Caused: hudson.util.HudsonFailedToLoad
at hudson.WebAppMain$3.run(WebAppMain.java:250)

Is there another way to disable all occurrences of the plugin so we can log in?

Answer 1

This is likely because your /var/lib/jenkins/config.xml has a section in it that looks like the following:

  <securityRealm class="hudson.plugins.active_directory.ActiveDirectorySecurityRealm" plugin="[email protected]">
    <domains>
      <hudson.plugins.active__directory.ActiveDirectoryDomain>
        <name>ad.example.com</name>
        <bindPassword>{some obfuscated password here}</bindPassword>
      </hudson.plugins.active__directory.ActiveDirectoryDomain>
    </domains>
    <startTls>true</startTls>
    <groupLookupStrategy>RECURSIVE</groupLookupStrategy>
    <removeIrrelevantGroups>true</removeIrrelevantGroups>
    <tlsConfiguration>TRUST_ALL_CERTIFICATES</tlsConfiguration>
  </securityRealm>

You can gain admin access with the following steps. Note that this will (temporarily) give admin access to anonymous users, so use with caution!

Shut down Jenkins, remove the above securityRealm section from your config.xml, and also change the following section:

<useSecurity>true</useSecurity>

to this:

<useSecurity>false</useSecurity>

Start Jenkins again. At this point, you can use the web UI to re-install/configure authn/authz plugins.

See also this question on admin backdoors for Jenkins.