How to print called functions in android?

Question

I'm using frida on an APK and I'm trying to print out which function is being called, and especially which parameters are sent to it. My environment is set correctly as I can print out classes, and perform various actions in accordance to the docs.

This is the closest i've found: https://codeshare.frida.re/@razaina/get-a-stack-trace-in-your-hook/

But the code gives out errors (ThreadDef undefined and so on)

And the frida docs didn't help me get where I'm trying to.

Any guidance? suggestions? help?

Answer 1

The code from codeshare@razaina has bugs which can be easily fixed (threadef != ThreadDef)

var printBacktrace = function () {
    Java.perform(function() {
        var JLog = Java.use('android.util.Log'), JException = Java.use('java.lang.Exception');
        // getting stacktrace by throwing an exception
        console.warn(JLog.getStackTraceString(JException.$new()));
    });
};

Just call printBacktrace() w/e you want to see who called your hooked function.

If you want to hook all the methods of Java class you can use this snippet;

var Color = {
    RESET: "\x1b[39;49;00m", Black: "0;01", Blue: "4;01", Cyan: "6;01", Gray: "7;11", Green: "2;01", Purple: "5;01", Red: "1;01", Yellow: "3;01",
    Light: {
        Black: "0;11", Blue: "4;11", Cyan: "6;11", Gray: "7;01", Green: "2;11", Purple: "5;11", Red: "1;11", Yellow: "3;11"
    }
};

/**
 *
 * @param input. 
 *      If an object is passed it will print as json 
 * @param kwargs  options map {
 *     -l level: string;   log/warn/error
 *     -i indent: boolean;     print JSON prettify
 *     -c color: @see ColorMap
 * }
 */
var LOG = function (input, kwargs) {
    kwargs = kwargs || {};
    var logLevel = kwargs['l'] || 'log', colorPrefix = '\x1b[3', colorSuffix = 'm';
    if (typeof input === 'object')
        input = JSON.stringify(input, null, kwargs['i'] ? 2 : null);
    if (kwargs['c'])
        input = colorPrefix + kwargs['c'] + colorSuffix + input + Color.RESET;
    console[logLevel](input);
};

var printBacktrace = function () {
    Java.perform(function() {
        var android_util_Log = Java.use('android.util.Log'), java_lang_Exception = Java.use('java.lang.Exception');
        // getting stacktrace by throwing an exception
        LOG(android_util_Log.getStackTraceString(java_lang_Exception.$new()), { c: Color.Gray });
    });
};

function traceClass(targetClass) {
    var hook;
    try {
        hook = Java.use(targetClass);
    } catch (e) {
        console.error("trace class failed", e);
        return;
    }

    var methods = hook.class.getDeclaredMethods();
    hook.$dispose();

    var parsedMethods = [];
    methods.forEach(function (method) {
        var methodStr = method.toString();
        var methodReplace = methodStr.replace(targetClass + ".", "TOKEN").match(/\sTOKEN(.*)\(/)[1];
         parsedMethods.push(methodReplace);
    });

    uniqBy(parsedMethods, JSON.stringify).forEach(function (targetMethod) {
        traceMethod(targetClass + '.' + targetMethod);
    });
}

function traceMethod(targetClassMethod) {
    var delim = targetClassMethod.lastIndexOf('.');
    if (delim === -1)
        return;

    var targetClass = targetClassMethod.slice(0, delim);
    var targetMethod = targetClassMethod.slice(delim + 1, targetClassMethod.length);

    var hook = Java.use(targetClass);
    var overloadCount = hook[targetMethod].overloads.length;

    LOG({ tracing: targetClassMethod, overloaded: overloadCount }, { c: Color.Green });

    for (var i = 0; i < overloadCount; i++) {
        hook[targetMethod].overloads[i].implementation = function () {
            var log = { '#': targetClassMethod, args: [] };

            for (var j = 0; j < arguments.length; j++) {
                var arg = arguments[j];
                // quick&dirty fix for java.io.StringWriter char[].toString() impl because frida prints [object Object]
                if (j === 0 && arguments[j]) {
                    if (arguments[j].toString() === '[object Object]') {
                        var s = [];
                        for (var k = 0, l = arguments[j].length; k < l; k++) {
                            s.push(arguments[j][k]);
                        }
                        arg = s.join('');
                    }
                }
                log.args.push({ i: j, o: arg, s: arg ? arg.toString(): 'null'});
            }

            var retval;
            try {
                retval = this[targetMethod].apply(this, arguments); // might crash (Frida bug?)
                log.returns = { val: retval, str: retval ? retval.toString() : null };
            } catch (e) {
                console.error(e);
            }
            LOG(log, { c: Color.Blue });
            return retval;
        }
    }
}

// remove duplicates from array
function uniqBy(array, key) {
    var seen = {};
    return array.filter(function (item) {
        var k = key(item);
        return seen.hasOwnProperty(k) ? false : (seen[k] = true);
    });
}


var Main = function() {
    Java.perform(function () { // avoid java.lang.ClassNotFoundException
        [
            // "java.io.File",
            'java.net.Socket',
            'com.package.MyCustomClass'
        ].forEach(traceClass);

    });
};

Java.perform(Main);