Android App - Sharif University CTF 2016

apkファイルが配布される

jadxでデコンパイルすると以下の関数が見つかる

どちらもネイティブメソッドなのでコードを読む

code:java

@Override // android.view.View.OnClickListener

public void onClick(View view) {

new String(" ");

String editable = this.a.b.getText().toString();

Log.v("EditText", this.a.b.getText().toString());

new String("");

int processObjectArrayFromNative = this.a.processObjectArrayFromNative(editable);

int IsCorrect = this.a.IsCorrect(editable);

String str = String.valueOf(this.a.d + processObjectArrayFromNative) + " ";

try {

MessageDigest instance = MessageDigest.getInstance("MD5");

instance.update(str.getBytes());

byte[] digest = instance.digest();

StringBuffer stringBuffer = new StringBuffer();

for (byte b : digest) {

stringBuffer.append(Integer.toString((b & 255) + 256, 16).substring(1));

}

if (IsCorrect == 1 && this.a.e != "unknown") {

this.a.c.setText("Sharif_CTF(" + stringBuffer.toString() + ")");

}

if (IsCorrect == 1 && this.a.e == "unknown") {

this.a.c.setText("Just keep Trying :-)");

}

if (IsCorrect == 0) {

this.a.c.setText("Just keep Trying :-)");

}

} catch (NoSuchAlgorithmException e) {

e.printStackTrace();

}

}

エミュレータでapkを実行してこれを入力すれば良さそう

バージョンが古すぎてエミュレータで動かなかったので終わり