工具函数的封装

打印堆栈

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function showStacks() {
    console.log(
        Java.use("android.util.Log")
            .getStackTraceString(
                Java.use("java.lang.Throwable").$new()
            )
    );
}

还有一个问题，就是在自吐算法hook的时候 ，肯定要根据抓包的数据包的data来搜索hook结果，数据包的data可能是各种格式，hex、base64等等，所以还需要封装base64、hex等打印数据的函数，因为在打印输入和输出的data的时候，不可能直接把 byte[] 给打印出来

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var ByteString = Java.use("com.android.okhttp.okio.ByteString");
function toBase64(tag, data) {
    console.log(tag + " Base64: ", ByteString.of(data).base64());
}
function toHex(tag, data) {
    console.log(tag + " Hex: ", ByteString.of(data).hex());
}
function toUtf8(tag, data) {
    console.log(tag + " Utf8: ", ByteString.of(data).utf8());
}

hook.js

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Java.perform(function () {

    function showStacks() {
        console.log(
            Java.use("android.util.Log")
                .getStackTraceString(
                    Java.use("java.lang.Throwable").$new()
                )
        );
    }
    var ByteString = Java.use("com.android.okhttp.okio.ByteString");
    function toBase64(tag, data) {
        console.log(tag + " Base64: ", ByteString.of(data).base64());
    }
    function toHex(tag, data) {
        console.log(tag + " Hex: ", ByteString.of(data).hex());
    }
    function toUtf8(tag, data) {
        console.log(tag + " Utf8: ", ByteString.of(data).utf8());
    }
    // toBase64([48,49,50,51,52]);
    // toHex([48,49,50,51,52]);
    // toUtf8([48,49,50,51,52]);
    //console.log(Java.enumerateLoadedClassesSync().join("\n"));

    var messageDigest = Java.use("java.security.MessageDigest");
    messageDigest.update.overload('byte').implementation = function (data) {
        console.log("MessageDigest.update('byte') is called!");
        return this.update(data);
    }
    messageDigest.update.overload('java.nio.ByteBuffer').implementation = function (data) {
        console.log("MessageDigest.update('java.nio.ByteBuffer') is called!");
        return this.update(data);
    }
    messageDigest.update.overload('[B').implementation = function (data) {
        console.log("MessageDigest.update('[B') is called!");
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " update data";
        toUtf8(tag, data);
        toHex(tag, data);
        toBase64(tag, data);
        console.log("=======================================================");
        return this.update(data);
    }
    messageDigest.update.overload('[B', 'int', 'int').implementation = function (data, start, length) {
        console.log("MessageDigest.update('[B', 'int', 'int') is called!");
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " update data";
        toUtf8(tag, data);
        toHex(tag, data);
        toBase64(tag, data);
        console.log("=======================================================", start, length);
        return this.update(data, start, length);
    }
    messageDigest.digest.overload().implementation = function () {
        console.log("MessageDigest.digest() is called!");
        var result = this.digest();
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " digest result";
        toHex(tag, result);
        toBase64(tag, result);
        console.log("=======================================================");
        return result;
    }
    messageDigest.digest.overload('[B').implementation = function (data) {
        console.log("MessageDigest.digest('[B') is called!");
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " digest data";
        toUtf8(tag, data);
        toHex(tag, data);
        toBase64(tag, data);
        var result = this.digest(data);
        var tags = algorithm + " digest result";
        toHex(tags, result);
        toBase64(tags, result);
        console.log("=======================================================");
        return result;
    }
    messageDigest.digest.overload('[B', 'int', 'int').implementation = function (data, start, length) {
        console.log("MessageDigest.digest('[B', 'int', 'int') is called!");
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " digest data";
        toUtf8(tag, data);
        toHex(tag, data);
        toBase64(tag, data);
        var result = this.digest(data, start, length);
        var tags = algorithm + " digest result";
        toHex(tags, result);
        toBase64(tags, result);
        console.log("=======================================================", start, length);
        return result;
    }

    var mac = Java.use("javax.crypto.Mac");
    mac.init.overload('java.security.Key', 'java.security.spec.AlgorithmParameterSpec').implementation = function (key, AlgorithmParameterSpec) {
        console.log("Mac.init('java.security.Key', 'java.security.spec.AlgorithmParameterSpec') is called!");
        return this.init(key, AlgorithmParameterSpec);
    }
    mac.init.overload('java.security.Key').implementation = function (key) {
        console.log("Mac.init('java.security.Key') is called!");
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " init Key";
        var keyBytes = key.getEncoded();
        toUtf8(tag, keyBytes);
        toHex(tag, keyBytes);
        toBase64(tag, keyBytes);
        console.log("=======================================================");
        return this.init(key);
    }
    mac.update.overload('byte').implementation = function (data) {
        console.log("Mac.update('byte') is called!");
        return this.update(data);
    }
    mac.update.overload('java.nio.ByteBuffer').implementation = function (data) {
        console.log("Mac.update('java.nio.ByteBuffer') is called!");
        return this.update(data);
    }
    mac.update.overload('[B').implementation = function (data) {
        console.log("Mac.update('[B') is called!");
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " update data";
        toUtf8(tag, data);
        toHex(tag, data);
        toBase64(tag, data);
        console.log("=======================================================");
        return this.update(data);
    }
    mac.update.overload('[B', 'int', 'int').implementation = function (data, start, length) {
        console.log("Mac.update('[B', 'int', 'int') is called!");
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " update data";
        toUtf8(tag, data);
        toHex(tag, data);
        toBase64(tag, data);
        console.log("=======================================================", start, length);
        return this.update(data, start, length);
    }
    mac.doFinal.overload().implementation = function () {
        console.log("Mac.doFinal() is called!");
        var result = this.doFinal();
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " doFinal result";
        toHex(tag, result);
        toBase64(tag, result);
        console.log("=======================================================");
        return result;
    }

    var cipher = Java.use("javax.crypto.Cipher");
    cipher.init.overload('int', 'java.security.cert.Certificate').implementation = function () {
        console.log("Cipher.init('int', 'java.security.cert.Certificate') is called!");
        return this.init.apply(this, arguments);
    }
    cipher.init.overload('int', 'java.security.Key', 'java.security.SecureRandom').implementation = function () {
        console.log("Cipher.init('int', 'java.security.Key', 'java.security.SecureRandom') is called!");
        return this.init.apply(this, arguments);
    }
    cipher.init.overload('int', 'java.security.cert.Certificate', 'java.security.SecureRandom').implementation = function () {
        console.log("Cipher.init('int', 'java.security.cert.Certificate', 'java.security.SecureRandom') is called!");
        return this.init.apply(this, arguments);
    }
    cipher.init.overload('int', 'java.security.Key', 'java.security.AlgorithmParameters', 'java.security.SecureRandom').implementation = function () {
        console.log("Cipher.init('int', 'java.security.Key', 'java.security.AlgorithmParameters', 'java.security.SecureRandom') is called!");
        return this.init.apply(this, arguments);
    }
    cipher.init.overload('int', 'java.security.Key', 'java.security.spec.AlgorithmParameterSpec', 'java.security.SecureRandom').implementation = function () {
        console.log("Cipher.init('int', 'java.security.Key', 'java.security.spec.AlgorithmParameterSpec', 'java.security.SecureRandom') is called!");
        return this.init.apply(this, arguments);
    }
    cipher.init.overload('int', 'java.security.Key', 'java.security.AlgorithmParameters').implementation = function () {
        console.log("Cipher.init('int', 'java.security.Key', 'java.security.AlgorithmParameters') is called!");
        return this.init.apply(this, arguments);
    }

    cipher.init.overload('int', 'java.security.Key').implementation = function () {
        console.log("Cipher.init('int', 'java.security.Key') is called!");
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " init Key";
        var className = JSON.stringify(arguments[1]);
        if(className.indexOf("OpenSSLRSAPrivateKey") === -1){
            var keyBytes = arguments[1].getEncoded();
            toUtf8(tag, keyBytes);
            toHex(tag, keyBytes);
            toBase64(tag, keyBytes);
        }
        console.log("=======================================================");
        return this.init.apply(this, arguments);
    }
    cipher.init.overload('int', 'java.security.Key', 'java.security.spec.AlgorithmParameterSpec').implementation = function () {
        console.log("Cipher.init('int', 'java.security.Key', 'java.security.spec.AlgorithmParameterSpec') is called!");
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " init Key";
        var keyBytes = arguments[1].getEncoded();
        toUtf8(tag, keyBytes);
        toHex(tag, keyBytes);
        toBase64(tag, keyBytes);
        var tags = algorithm + " init iv";
        var iv = Java.cast(arguments[2], Java.use("javax.crypto.spec.IvParameterSpec"));
        var ivBytes = iv.getIV();
        toUtf8(tags, ivBytes);
        toHex(tags, ivBytes);
        toBase64(tags, ivBytes);
        console.log("=======================================================");
        return this.init.apply(this, arguments);
    }

    cipher.doFinal.overload('java.nio.ByteBuffer', 'java.nio.ByteBuffer').implementation = function () {
        console.log("Cipher.doFinal('java.nio.ByteBuffer', 'java.nio.ByteBuffer') is called!");
        return this.doFinal.apply(this, arguments);
    }
    cipher.doFinal.overload('[B', 'int').implementation = function () {
        console.log("Cipher.doFinal('[B', 'int') is called!");
        return this.doFinal.apply(this, arguments);
    }
    cipher.doFinal.overload('[B', 'int', 'int', '[B').implementation = function () {
        console.log("Cipher.doFinal('[B', 'int', 'int', '[B') is called!");
        return this.doFinal.apply(this, arguments);
    }
    cipher.doFinal.overload('[B', 'int', 'int', '[B', 'int').implementation = function () {
        console.log("Cipher.doFinal('[B', 'int', 'int', '[B', 'int') is called!");
        return this.doFinal.apply(this, arguments);
    }
    cipher.doFinal.overload().implementation = function () {
        console.log("Cipher.doFinal() is called!");
        return this.doFinal.apply(this, arguments);
    }

    cipher.doFinal.overload('[B').implementation = function () {
        console.log("Cipher.doFinal('[B') is called!");
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " doFinal data";
        var data = arguments[0];
        toUtf8(tag, data);
        toHex(tag, data);
        toBase64(tag, data);
        var result = this.doFinal.apply(this, arguments);
        var tags = algorithm + " doFinal result";
        toHex(tags, result);
        toBase64(tags, result);
        console.log("=======================================================");
        return result;
    }
    cipher.doFinal.overload('[B', 'int', 'int').implementation = function () {
        console.log("Cipher.doFinal('[B', 'int', 'int') is called!");
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " doFinal data";
        var data = arguments[0];
        toUtf8(tag, data);
        toHex(tag, data);
        toBase64(tag, data);
        var result = this.doFinal.apply(this, arguments);
        var tags = algorithm + " doFinal result";
        toHex(tags, result);
        toBase64(tags, result);
        console.log("=======================================================", arguments[1], arguments[2]);
        return result;
    }

    var signature = Java.use("java.security.Signature");
    signature.update.overload('byte').implementation = function (data) {
        console.log("Signature.update('byte') is called!");
        return this.update(data);
    }
    signature.update.overload('java.nio.ByteBuffer').implementation = function (data) {
        console.log("Signature.update('java.nio.ByteBuffer') is called!");
        return this.update(data);
    }
    signature.update.overload('[B', 'int', 'int').implementation = function (data, start, length) {
        console.log("Signature.update('[B', 'int', 'int') is called!");
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " update data";
        toUtf8(tag, data);
        toHex(tag, data);
        toBase64(tag, data);
        console.log("=======================================================", start, length);
        return this.update(data, start, length);
    }
    signature.sign.overload('[B', 'int', 'int').implementation = function () {
        console.log("Signature.sign('[B', 'int', 'int') is called!");
        return this.sign.apply(this, arguments);
    }
    signature.sign.overload().implementation = function () {
        console.log("Signature.sign() is called!");
        var result = this.sign();
        var algorithm = this.getAlgorithm();
        var tag = algorithm + " sign result";
        toHex(tag, result);
        toBase64(tag, result);
        console.log("=======================================================");
        return result;
    }

});

应用场景

加密在Java层，并且调用了标准加密库的

加密在Java层，但是使用反射调用标准加密库的

加密在so层，但是用jni调用了Java标准加密库的

app被加固，但是调用了标准加密库的

通过打印堆栈可以辅助定位加密代码所在类

局限性

加密在Java层，自写的算法

加密在so层，C/C++写的算法

加密在Java层，并且调用了标准加密库，但是加密前后的数据都做了其他处理，这个的意思就是我们的hook代码只是把加密算法的直接输入和输出给打印出来了，但是输出可能有后续处理，比如base64，这样的话抓到的数据包里的数据在我们的hook输出里就搜不到，这个时候就需要对抓包到的数据我们自己去猜一下，比如url decode、base64 decode等等

hook到加密数据不代表一定是业务代码调用的，可能是框架调用的