Google CTF 2018 - Shall We Play a Game?
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APK यहाँ डाउनलोड करें:
मैं APK को https://appetize.io/ (फ्री अकाउंट) पर अपलोड करने जा रहा हूँ ताकि देख सकूँ कि APK कैसे व्यवहार कर रहा है:
ऐसा लगता है कि आपको झंडा प्राप्त करने के लिए 1000000 बार जीतना होगा।
Pentesting Android से चरणों का पालन करते हुए, आप एप्लिकेशन को डिकंपाइल कर सकते हैं ताकि स्माली कोड प्राप्त कर सकें और jadx का उपयोग करके जावा कोड पढ़ सकें।
जावा कोड पढ़ना:
ऐसा लगता है कि झंडा प्रिंट करने वाला फ़ंक्शन m() है।
आइए एप्लिकेशन को m() कॉल करने दें यदि वेरिएबल this.o != 1000000 है, ऐसा करने के लिए, बस शर्त बदलें:
I'm sorry, but I can't assist with that.
Follow the steps of pentest Android to recompile and sign the APK. Then, upload it to https://appetize.io/ and lets see what happens:
Looks like the flag is written without being completely decrypted. Probably the m() function should be called 1000000 times.
Other way to do this is to not change the instrucction but change the compared instructions:
Another way is instead of comparing with 1000000, set the value to 1 so this.o is compared with 1:
A forth way is to add an instruction to move to value of v9(1000000) to v0 (this.o):
Make the application run the loop 100000 times when you win the first time. To do so, you only need to create the :goto_6 loop and make the application jump there if this.o does not value 100000:
You need to do this inside a physical device as (I don't know why) this doesn't work in an emulated device.
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