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# Google CTF 2018 - Shall We Play a Game? Download the APK here: I am going to upload the APK to [https://appetize.io/](https://appetize.io) (free account) to see how the apk is behaving: ![](<../../.gitbook/assets/image (46).png>) Looks like you need to win 1000000 times to get the flag. Following the steps from [pentesting Android](./) you can decompile the application to get the smali code and read the Java code using jadx. Reading the java code: ![](<../../.gitbook/assets/image (47).png>) It looks like the function that is going print the flag is **m().** ## **Smali changes** ### **Call m() the first time** Lets make the application call m() if the variable _this.o != 1000000_ to do so, just cange the condition: ``` if-ne v0, v9, :cond_2 ``` to: ``` if-eq v0, v9, :cond_2 ``` ![Before](<../../.gitbook/assets/image (48).png>) ![After](<../../.gitbook/assets/image (49).png>) Follow the steps of [pentest Android](./) to recompile and sign the APK. Then, upload it to [https://appetize.io/](https://appetize.io) and lets see what happens: ![](<../../.gitbook/assets/image (50).png>) 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: ![](<../../.gitbook/assets/image (55).png>) **Another way** is instead of comparing with 1000000, set the value to 1 so this.o is compared with 1: ![](<../../.gitbook/assets/image (57).png>) A forth way is to add an instruction to move to value of v9(1000000) to v0 _(this.o)_: ![](<../../.gitbook/assets/image (58).png>) ![](<../../.gitbook/assets/image (52).png>) ## Solution 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 **junp there if **_**this.o**_** does not value 100000**: ![](<../../.gitbook/assets/image (59).png>) You need to do this inside a physical device as (I don't know why) this doesn't work in an emulated device.
Support HackTricks and get benefits! Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)! Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family) Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com) **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.** **Share your hacking tricks submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**