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Java provides several APIs that allow outside programs to monitor a running Java program. These APIs also permit the Java program to be monitored remotely by programs on distinct hosts. Such features are handy convenient for debugging the program , or fine-tuning its performance. However, if a Java program is deployed in production with remote monitoring enabled, an attacker can connect to the JVM and inspect its behavior and data, including potentially sensitive information. An attacker can also exert some control over the program's behavior. Consequently, remote monitoring must be disabled when running a Java program in production.

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The JVMTI contains extensive facilities to find out about the internals of a running JVM, including facilities to monitor and modify a running Java program. These facilities are rather low - level and require the use of the Java Native Interface (JNI) and C Language programming. However, they provide the opportunity to access fields that would not normally be accessible. Also, there are facilities that can change the behavior of a running Java program (for example, threads can be suspended or stopped). The JVMTI profiling tools can also measure the time that a thread takes to execute, leaving applications vulnerable to timing attacks.

The JVMTI works by using agents that communicate with the running JVM. These agents must be loaded at JVM startup and are usually specified via one of the command-line options {{–agentlib:}} or {{–agentpath:}}. However, agents can be specified in environment variables, although this feature can be disabled where security is a concern. The JVMTI is always enabled, and JVMTI agents may run under the default security manager without requiring any permissions to be granted.

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The JDPA facilities are similar to the reflection API, which is described in rule SEC05-J. Do not use reflection to increase accessibility of classes, methods, or fields. In particular, the JPDA provides methods to get and set field and array values. Access control is not enforced, so , for example, that even the values of private fields can be set by a remote process via the JPDA.

Introducing the default security manager means that various Various permissions must be granted in order for debugging to take place under the default security manager. The following policy file was used to run the JPDA Trace demonstration under the default security manager:

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Because JPDA supports remote debugging, a remote host can access the debugger. An attacker can exploit this feature to study sensitive information or modify the behavior of a running Java application unless appropriate protection is enabled. A security manager can ensure that only known, trusted hosts are given permissions to use the debugger interface.

Java SE Monitoring and Management

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Features

Java contains extensive facilities for monitoring and managing a JVM \[[JMX 2006|AA. Bibliography#JMX 2006]\]. In particular, the Java Management Extension (JMX) API enables the monitoring and control of class loading, thread state and stack traces, deadlock detection, memory usage, garbage collection, operating system information, and other operations \[[Sun 04a|AA. Bibliography#Sun 04a]\]. ThereIt arealso alsohas facilities for logging monitoring and management.

The Java SE Monitoring monitoring and Management management features fall into four broad categories:

• The Java Management Extensions ( JMX ) technology: This technology serves as the underlying interface for local and remote monitoring and management.
• Instrumentation for the Java Virtual Machine ( JVM): These facilities enable out-of-the-box monitoring and management of the JVM and are based on the JMX specification.
• Monitoring and Management Application Programming Interfaces (management API): These facilities use the java.lang.management package to provide the monitoring and management interface. Applications can use this package to monitor themselves or to let JMX technology-compliant tools to monitor and manage them.
• Monitoring and Management management tools: Tools such as Jconsole JConsole implement the JMX interface to provide monitoring and management facilities.

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 When remote monitoring and management is enabled, access is password-controlled by default. However, password control can be disabled. Disabling password authentication is insecure because any user who can discover the port number that the JMX service is listening on can monitor and control the Java applications running on the JVM \[[JMXG 2006|AA. Bibliography#JMXG 06]\].

The JVM Remoteremote monitoring and management facility uses a secure communication channel (Secure Sockets Layer [SSL]) by default. However, if an attacker can start a bogus remote method invocation (RMI) registry server on the monitored machine before the legitimate RMI registry server is started, JMX passwords can be intercepted. Also, SSL can be disabled when using remote monitoring and management, which could, again, compromise security. See _The Java SE Monitoring and Management Guide_ \[[JMXG 2006|AA. Bibliography#JMXG 06]\] for further details and for avoidancemitigation strategies.

There are also provisions to require proper authentication of the remote server. However, users may start a JVM with remote monitoring and management enabled, but with no security, and this would leave the JVM open to attack from outsiders. Although a user could not easily turn on accidently enabling remote monitoring and management by accidentis unlikely, they users might not realize that starting a JVM so enabled, without any security also switched on, could leave their JVM exposed to outside abuseattack.

If exploited, the monitoring and management facilities can seriously compromise the security of Java applications. For example, an attacker can obtain information about the number of classes loaded and threads running, thread state along with traces of live threads, system properties, VM arguments, and memory consumption.

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In this noncompliant code example, the JVMTI works by using agents that communicate with the running JVM. These agents are usually loaded at JVM startup via one of the command-line options , -agentlib or -agentpath. In the following command, libname is the name of the library to load while options are passed to the agent on startup.

// "libname" is the name of the library to load, or an absolute library path
// "options" are passed to the agent on start-up
${JDK_PATH}/bin/java -agentlib:libname=options ApplicationName

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This noncompliant code example uses command-line arguments to invoke the JVM so that it can be debugged from a running debugger application by listening for connections using shared memory at transport address mysharedmemory.

${JDK_PATH}/bin/java -agentlib:jdwp=transport=dt_shmem,
    address=mysharedmemory ApplicationName

Likewise, the command-line arguments -Xrunjdwp, which is equivalent to -agentlib, and -Xdebug, which is used by the jdb tool, command line arguments also enable application debugging.

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${JDK_PATH}/bin/java
    -Dcom.sun.management.jmxremote.port=8000 ApplicationName

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This compliant solution starts the JVM without any agents enabled. Avoid using the the -agentlib, -Xrunjdwp, and -Xdebug command-line arguments on production machines. This compliant solution also installs a the default security manager for good measure.

${JDK_PATH}/bin/java -Djava.security.manager ApplicationName

Clear the environment variable JAVA_TOOL_OPTIONS in the manner appropriate for your platform, for example, by setting it to an empty string value. This prevents JVMTI agents from receiving arguments via this routemechanism. The command-line argument -Xnoagent can also be used to disable the debugging features supported by the old Java debugger (oldjdb).

This compliant solution disables monitoring by remote machines. By default, local monitoring is enabled in Java 6. In earlier versions, the system property com.sun.management.jmxremote had to must be set to enable local monitoring. Although the unsupported -XX:+DisableAttachMechanism command-line option may be used to disable local Java tools from monitoring the JVM, it is always possible to use native debuggers and other tools to perform monitoring. Fortunately, monitoring tools require at least as many privileges as the owner of the JVM process possesses, reducing the threat of local exploitation through privilege escalation.

Local monitoring uses temporary files and sets the file permissions to those of the owner of the JVM process. Ensure that adequate file protection is in place on the system running the JVM so that the temporary files are accessed appropriately. See rule FIO03-J. Remove temporary files before termination for additional information.

The _Java SE Monitoring and Management Guide_ \[[JMXG 2006|AA. Bibliography#JMXG 06]\] provides further advice:

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Moving jconsole to a remote system removes its system resource load from the production environment.

Noncompliant Code Example (

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Remote Debugging)

Remote debugging requires the use of sockets as the transport (transport=dt_socket). Remote debugging also requires specification of the type of application (server=y, where y denotes that the JVM is the server and is waiting for a debugger application to connect to it) and the port number to listen on (address=9000).

${JDK_PATH}/bin/java -agentlib:jdwp=transport=dt_socket, 
    server=y,address=9000 ApplicationName

Remote debugging is dangerous because an attacker can spoof the client IP address and connect to the JPDA host. Depending on the attacker's position in the network, they he or she could glean extract debugging information by sniffing the network traffic that the JPDA host sends to the forged IP address.

Compliant Solution (

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Remote Debugging)

Restrict remote debugging to trusted hosts by modifying the security policy file to grant appropriate permissions only to those trusted hosts. For example, specify the permission java.net.SocketPermission for only the JPDA host and remove the permission from other hosts.

The JPDA host can serve either as a server or as a client. When the attacker cannot sniff the network to determine the identity of machines that use the JPDA host (for example, through use of a secure channel), prefer specifying specify the JPDA host as the client and the debugger application as the server by changing the value of the server argument to n.

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${JDK_PATH}/bin/java -agentlib:jdwp=transport=dt_socket, 
    server=n,address=9000 ApplicationName

When it is necessary to run a JVM with debugging enabled, avoid granting permissions that are not needed by the application. In particular, avoid granting socket permissions to arbitrary hosts, that is, omit the permission java.net.SocketPermission "*", "connect,accept".

Exceptions

ENV05-EX0: A Java program may be remotely monitored using any of these technologies if when it can be guaranteed that no program outside the local trust boundary can access the program. For example, if the program lives on a local network that is both completely trusted and disconnected from any larger networks, including the Internet, then remote monitoring is permitted.

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Deploying a Java application with the JVM Tool InterfaceJVMTI, JPDJPDA, or remote monitoring enabled can allow an attacker to monitor or modify its behavior.

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