Set the -max_len argument in junit

[svdbtno]

We want to have more data available in the FuzzedDataProvider. Currently we only receive very few bytes. We would like to receive more therefore we want to set the -max_len for libFuzzer.
We currently get the following info log= INFO: -max_len is not provided; libFuzzer will not generate inputs larger than 4096 bytes.

We tried setting it using the following command: JAZZER_FUZZ=1 mvn test -Dtest=ourTest#testMethod -Djazzer.internal.args.0="-max_len=50000" and we tried JAZZER_FUZZ=1 mvn test -Dtest=ourTest#testMethod -Dmax_len=50000 both did not work. Any suggestions?

PS. jazzer.internal.args.0 is used, since we saw the following:

jazzer/src/main/java/com/code_intelligence/jazzer/junit/FuzzTestExecutor.java

Lines 270 to 280 in 1f2bdf9

	private static List<String> getLibFuzzerArgs(ExtensionContext extensionContext) {
	List<String> args = new ArrayList<>();
	for (int i = 0; ; i++) {
	Optional<String> arg = extensionContext.getConfigurationParameter("jazzer.internal.arg." + i);
	if (!arg.isPresent()) {
	break;
	}
	args.add(arg.get());
	}
	return args;
	}

[yawkat]

the junit integration in general is missing a bunch of features that make it unusable for some of our fuzz targets. e.g. setting the instrumented classes or the corpus.

It would be nice to have some generic, non-internal way of adding jazzer parameters to a FuzzTest.

[ramzanzan]

Add into junit-platform.properties lines:
jazzer.internal.arg.0=fakeArgv
jazzer.internal.arg.1=-lib_fuzzer_opt1=val1
jazzer.internal.arg.2=-lib_fuzzer_opt2=val2

@yawkat - Good feedback!
Sorry for our late reply. We made some strategic changes and pivoted to working on Jazzer updates as closed source only. We can give you more detailed support on a call/over email and try other options for you. Just need to understand in detail what you are trying to achieve, and we can give the best options to solve.
Ping me? david[dot]merian [at] code-intelligence[dot]com

@ramzanzan and @svdbtno - same as I wrote to @yawkat above, happy to chat with you all too about your specific wishes/challenges!

[ksiv]

Add into junit-platform.properties lines: jazzer.internal.arg.0=fakeArgv jazzer.internal.arg.1=-lib_fuzzer_opt1=val1 jazzer.internal.arg.2=-lib_fuzzer_opt2=val2

@svdbtno , @ramzanzan, thank you my friends, you have made my day. Here is my reworked option just in case someone needs it outside platform properties file:

   @BeforeAll
   public void setUp() {
      System.setProperty("jazzer.internal.arg.0","-fakeArgv");
      System.setProperty("jazzer.internal.arg.1","-max_len=8192");
      System.setProperty("jazzer.internal.arg.2","-print_final_stats=1");

      }

[Marcono1234]

It might be in general useful if the JUnit integration documentation mentioned how these properties can be set, and which commonly used properties exist.

Another useful property is jazzer.instrument to specify which classes to instrument (otherwise it is derived from the package of the test class?). The JUnit examples in this repository set this property, but it seems the documentation does not mention it anywhere.

Possibly related to #877