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DarkCTF 2020: Rev/so_much

Rev/so_much

207 points

strcmp printf File

Solution

I've used ghidra to have a look into the decompiled code.

After quick examination I've came to conclusion that the code base on strcmp function. I've decided to override this function with my own implementation.

Prepared below code:

#define _GNU_SOURCE

int strcmp ( char * str1, char * str2 )
{
return 0;
}

int main()
{
return 0;
}

Compiled it and executed the program with LD_PRELOAD.

gcc -ldl -fpic -nostartfiles -shared mystrcmp.c -o mystrcmp.so
sudo LD_PRELOAD=./mystrcmp.so ./so_much anything

darkCTF{w0w_s0_m4ny_funct10ns}

DarkCTF 2020: Misc/Minetest 1

Misc/Minetest 1

303 points

``` Just a sanity check to see whether you installed Minetest successfully and got into the game

Challenge ```

Solution

Just install the game and import the given world. Once started we've got some logical gates. If you make circuit to have true on the output flag will show up.

DarkCTF{y0u_5ucess_fu11y_1ns7alled_m1n37e57}

DownUnderCTF 2020: Bad man

Bad man

200 points

Author: n00bmaster

We have recently received reports about a hacker who goes by the alias und3rm4t3r. He has been threatening innocent people for money and must be stopped. Help us find him and get us the flag.

Solution

I've found und3rm4t3r profile (https://twitter.com/und3rm4t3r/). One of the tweets seems interesting:

So, I've checked the wayback machine for a snapshot (https://web.archive.org/web/20200723112257/twitter.com/und3rm4t3r/) and found the flag :-)

DUCTF{w4y_b4ck_1n_t1m3_w3_g0}