新版本 ognl 有一个 UseStricterInvocation 模块，默认开启，执行 ognl 表达式容易出现： cannot be called from within OGNL invokeMethod() under stricter invocation mode

[hengyunabc]

$ ognl '@java.lang.ClassLoader@getSystemClassLoader().loadClass("aaa")'
Failed to execute ognl, exception message: ognl.MethodFailedException: Method "getSystemClassLoader" failed for object class java.lang.ClassLoader [java.lang.IllegalAccessException: Method [public static java.lang.ClassLoader java.lang.ClassLoader.getSystemClassLoader()] cannot be called from within OGNL invokeMethod() under stricter invocation mode.], please check $HOME/logs/arthas/arthas.log for more details.

    /**
     * Control usage of "stricter" invocation processing by invokeMethod() using the JVM options:
     * -Dognl.UseStricterInvocation=true
     * -Dognl.UseStricterInvocation=false
     * <p>
     * Note: Using the "true" value has the same effect as omitting the option completely.
     * The default behaviour is to use the "stricter" invocation processing.
     * Using the "false" value reverts to the older "less strict" invocation processing
     * (in the event the "stricter" processing causes issues for existing applications).
     */
    static final String USE_STRICTER_INVOCATION = "ognl.UseStricterInvocation";

需要和 arthas 本身的 options strict 对应起来。

[tasier]

I recently encountered this issue as well. Has it been resolved in the new version?

[p1n93r]

@tasier

The current version of Arthas (4.0.4) has not resolved this issue with OGNL. You can solve it using the following steps:

1. First, check Arthas' own classloader to get its classloader hash:

classloader -l | grep taobao

3. Specify the Arthas classloader hash and disable the OGNL strict option:

ognl -c 1eb98135 '#field = @com.taobao.arthas.core.util.reflect.FieldUtils@getDeclaredField(Class.forName("ognl.OgnlRuntime"),"_useStricterInvocation",true), #modifiers = @com.taobao.arthas.core.util.reflect.FieldUtils@getDeclaredField(#field.getClass(),"modifiers",true),#modifiers.setInt(#field, #field.getModifiers() & [email protected]@FINAL),#field.set(null,false)'

[tasier]

@tasier

The current version of Arthas (4.0.4) has not resolved this issue with OGNL. You can solve it using the following steps:

1. First, check Arthas' own classloader to get its classloader hash:

classloader -l | grep taobao

3. Specify the Arthas classloader hash and disable the OGNL strict option:

ognl -c 1eb98135 '#field = @com.taobao.arthas.core.util.reflect.FieldUtils@getDeclaredField(Class.forName("ognl.OgnlRuntime"),"_useStricterInvocation",true), #modifiers = @com.taobao.arthas.core.util.reflect.FieldUtils@getDeclaredField(#field.getClass(),"modifiers",true),#modifiers.setInt(#field, #field.getModifiers() & [email protected]@FINAL),#field.set(null,false)'

I seems not work for me. I also use Arthas 4.0.4. Following is the exception stack.

[arthas-command-execute] WARN c.t.a.c.command.klass100.OgnlCommand -ognl: failed execute express: #field = @com.taobao.arthas.core.util.reflect.FieldUtils@getDeclaredField(Class.forName("ognl.OgnlRuntime"),"_useStricterInvocation",true), #modifiers = @com.taobao.arthas.core.util.reflect.FieldUtils@getDeclaredField(#field.getClass(),"modifiers",true),#modifiers.setInt(#field, #field.getModifiers() & [email protected]@FINAL),#field.set(null,false)
com.taobao.arthas.core.command.express.ExpressException: java.lang.NullPointerException: target is null for method setInt
at com.taobao.arthas.core.command.express.OgnlExpress.get(OgnlExpress.java:39)
at com.taobao.arthas.core.command.klass100.OgnlCommand.process(OgnlCommand.java:106)
at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl.process(AnnotatedCommandImpl.java:82)
at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl.access$100(AnnotatedCommandImpl.java:18)
at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl$ProcessHandler.handle(AnnotatedCommandImpl.java:111)
at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl$ProcessHandler.handle(AnnotatedCommandImpl.java:108)
at com.taobao.arthas.core.shell.system.impl.ProcessImpl$CommandProcessTask.run(ProcessImpl.java:385)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:840)
Caused by: java.lang.NullPointerException: target is null for method setInt
at ognl.OgnlRuntime.callMethod(OgnlRuntime.java:2032)
at ognl.ASTMethod.getValueBody(ASTMethod.java:97)
at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
at ognl.SimpleNode.getValue(SimpleNode.java:258)
at ognl.ASTChain.getValueBody(ASTChain.java:141)
at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
at ognl.SimpleNode.getValue(SimpleNode.java:258)
at ognl.ASTSequence.getValueBody(ASTSequence.java:63)
at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
at ognl.SimpleNode.getValue(SimpleNode.java:258)
at ognl.Ognl.getValue(Ognl.java:586)
at ognl.Ognl.getValue(Ognl.java:688)
at ognl.Ognl.getValue(Ognl.java:658)
at com.taobao.arthas.core.command.express.OgnlExpress.get(OgnlExpress.java:36)

[p1n93r]

@tasier

If you're using JDK 17 or higher, you can try the following steps:

1. First, check Arthas' own classloader to get its classloader hash:

classloader -l | grep taobao

2. Specify the Arthas classloader hash and disable the OGNL strict option:

ognl -c 51e2f7d9 '#field = @com.taobao.arthas.core.util.reflect.FieldUtils@getDeclaredField(Class.forName("ognl.OgnlRuntime"),"_useStricterInvocation",true),#unsafe = @com.taobao.arthas.common.UnsafeUtils@UNSAFE, #staticFieldBaseMethod = new com.taobao.arthas.core.advisor.ArthasMethod(#unsafe.getClass(),"staticFieldBase","(Ljava/lang/reflect/Field;)Ljava/lang/Object"),#staticFieldOffsetMethod = new com.taobao.arthas.core.advisor.ArthasMethod(#unsafe.getClass(),"staticFieldOffset","(Ljava/lang/reflect/Field;)Ljava/lang/Object"),#putBooleanMethod = new com.taobao.arthas.core.advisor.ArthasMethod(#unsafe.getClass(),"putBoolean","(Ljava/lang/Object;JZ)V"),#staticFieldBase = #staticFieldBaseMethod.invoke(#unsafe,#field),#staticFieldOffset = #staticFieldOffsetMethod.invoke(#unsafe,#field),#putBooleanMethod.invoke(#unsafe, #staticFieldBase, #staticFieldOffset, false)'

Its effect is equivalent to the following code:

Field field = OgnlRuntime.class.getDeclaredField("_useStricterInvocation");
field.setAccessible(true);
// 获取字段的内存偏移量和基址
Object staticFieldBase = UnsafeUtils.UNSAFE.staticFieldBase(field);
long staticFieldOffset = UnsafeUtils.UNSAFE.staticFieldOffset(field);

// 修改字段的值
UnsafeUtils.UNSAFE.putBoolean(staticFieldBase, staticFieldOffset, strict);

[tasier]

@tasier

If you're using JDK 17 or higher, you can try the following steps:

1. First, check Arthas' own classloader to get its classloader hash:

classloader -l | grep taobao

2. Specify the Arthas classloader hash and disable the OGNL strict option:

ognl -c 51e2f7d9 '#field = @com.taobao.arthas.core.util.reflect.FieldUtils@getDeclaredField(Class.forName("ognl.OgnlRuntime"),"_useStricterInvocation",true),#unsafe = @com.taobao.arthas.common.UnsafeUtils@UNSAFE, #staticFieldBaseMethod = new com.taobao.arthas.core.advisor.ArthasMethod(#unsafe.getClass(),"staticFieldBase","(Ljava/lang/reflect/Field;)Ljava/lang/Object"),#staticFieldOffsetMethod = new com.taobao.arthas.core.advisor.ArthasMethod(#unsafe.getClass(),"staticFieldOffset","(Ljava/lang/reflect/Field;)Ljava/lang/Object"),#putBooleanMethod = new com.taobao.arthas.core.advisor.ArthasMethod(#unsafe.getClass(),"putBoolean","(Ljava/lang/Object;JZ)V"),#staticFieldBase = #staticFieldBaseMethod.invoke(#unsafe,#field),#staticFieldOffset = #staticFieldOffsetMethod.invoke(#unsafe,#field),#putBooleanMethod.invoke(#unsafe, #staticFieldBase, #staticFieldOffset, false)'

Its effect is equivalent to the following code:

Field field = OgnlRuntime.class.getDeclaredField("_useStricterInvocation");
field.setAccessible(true);
// 获取字段的内存偏移量和基址
Object staticFieldBase = UnsafeUtils.UNSAFE.staticFieldBase(field);
long staticFieldOffset = UnsafeUtils.UNSAFE.staticFieldOffset(field);

// 修改字段的值
UnsafeUtils.UNSAFE.putBoolean(staticFieldBase, staticFieldOffset, strict);

Thank you very much. It works now.
Does Arthas consider to support merge these two commands into one? such as

ognl -c `classloader -l | grep taobao`   '#field = @com.taobao.arthas.core.util.reflect.FieldUtils@getDeclaredField(Class.forName("ognl.OgnlRuntime"),"_useStricterInvocation",true),#unsafe = @com.taobao.arthas.common.UnsafeUtils@UNSAFE, #staticFieldBaseMethod = new com.taobao.arthas.core.advisor.ArthasMethod(#unsafe.getClass(),"staticFieldBase","(Ljava/lang/reflect/Field;)Ljava/lang/Object"),#staticFieldOffsetMethod = new com.taobao.arthas.core.advisor.ArthasMethod(#unsafe.getClass(),"staticFieldOffset","(Ljava/lang/reflect/Field;)Ljava/lang/Object"),#putBooleanMethod = new com.taobao.arthas.core.advisor.ArthasMethod(#unsafe.getClass(),"putBoolean","(Ljava/lang/Object;JZ)V"),#staticFieldBase = #staticFieldBaseMethod.invoke(#unsafe,#field),#staticFieldOffset = #staticFieldOffsetMethod.invoke(#unsafe,#field),#putBooleanMethod.invoke(#unsafe, #staticFieldBase, #staticFieldOffset, false)'

A bash shell command style like.