[All WriteUps for this CTF here](https://github.com/ipv6-feet-under/WriteUps-S.H.E.L.L.CTF21): https://github.com/ipv6-feet-under/WriteUps-S.H.E.L.L.CTF21

# sakuna

In this challenge we were given an executable.
For analyzing this executable we used `cutter`.
Opening the executable in `cutter`, we quickly discovered that the `main()` function calls the `domain_expression` function.
When we navigate into the function, we are presented with bits of the flag:


We now need to correctly assemble the flag together. For that we can use the `strcat` function that is used:


`SHELL{` is stored in `[s1]`

`5hR1n3}` is stored in `[var_20h_2]`

`M3L0v4l3` is stored in `[s2]`

`nT_` is stored in `[var_58h]`

The first parameter of the `strcat` function is `rcx`, the second is `rdx`
Following the Assembly instructions we can now construct the flag step by step:

```
SHELL{M3L0v413nT_5hR1n3}
```

Original writeup (https://github.com/ipv6-feet-under/WriteUps-S.H.E.L.L.CTF21/tree/main/Reverse%20Engineering/sakuna).