Hacker101 CTF Writeup

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H1 Thermostat - FLAG1

0x00 Params

There are different messages sending through. We can decode them with base64.

encoded readable
eyJjbWQiOiJnZXRUZW1wIn0 {“cmd”:”getTemp”}
eyJ0ZW1wZXJhdHVyZSI6IDc3LCAic3VjY2VzcyI6IHRydWV9 {“temperature”: 77, “success”: true}
eyJjbWQiOiJzZXRUZW1wIiwidGVtcCI6Nzd9 {“cmd”:”setTemp”,”temp”:77}
eyJjbWQiOiJzZXRUZW1wIiwidGVtcCI6NzB9 {“cmd”:”setTemp”,”temp”:70}
eyJzdWNjZXNzIjogdHJ1ZX0= {“success”: true}

As the app shows current temperature is 73 and target 70.

Tried to manually change the temperature by encode


But got an error as following

{"success": false, "error": "MAC failure"}

0x01 Check Source

Something wrong with that MAC. Need go back to check the source for some help.

classes.dex -> com -> hacker101 -> level11 -> PlayloadRequest

Both flags can be found here.