[picoctf19] Ghostdiary
Ghostdiary was a heap exploit challenge during the recent PicoCTF. The challenge was worth 500 points, i.e. it was one of the "big three" exploit challenges this year. It has the most solves out of the three, but was also unlocked from the beginning. Which means that probably a lot of people tried it who got distracted or stuck at a later point before unlocking the rest. It was one of the more "traditional" challenges. The technique used to exploit it was a nullbyte overflow to cause backwards coalescing, abusing overlapping chunks to overwrite FD and gain code execution by overwriting malloc_hook.
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