Tags: assembly reverse
Rating:
# Access Denied 1.2 2018 – ASSEMBLY
* **Category:** reverse
* **Points:** 400
## Challenge
> 0xeax stumbled upon Shellphish team. They gave him an **asm** file that is broken and **another file** which has the data section of that asm file.
>
> See if you can help 0xeax in getting the flag so that he can join Shellphish.
>
> Download files from :
>
> Assembly File : [https://accessd.sfo2.digitaloceanspaces.com/assembly350/asmb.asm](asmb.asm)
>
> Data Section : [https://accessd.sfo2.digitaloceanspaces.com/assembly350/data](data)
## Solution
It is sufficient to merge the ASM code provided into two files and to execute it, e.g. an [on-line tool](https://www.tutorialspoint.com/compile_assembly_online.php) can be used.
```assembly
section .text
global main
main:
mov ecx, 41
lop:
mov eax, msg
add eax, ecx
mov edx, 0
mov edx, [eax]
xor edx, 0xb
mov [eax], edx
mov edx, 0
mov dx, [eax]
rol dx, 0x5
mov edx, 0
mov dl, [eax]
ror dl, 0x9d
sub ecx, 1
cmp ecx, 0
jge lop
mov edx, 41
mov ecx, msg
mov ebx, 1
mov eax, 4
int 0x80
mov eax, 1
int 0x80
section .data
msg db 0x6a, 0x68, 0x68, 0x6e, 0x78, 0x78, 0x6f, 0x6e, 0x65, 0x62, 0x6e, 0x6f, 0x70, 0x3a, 0x54, 0x67, 0x3b, 0x7d, 0x38, 0x54, 0x73, 0x33, 0x3d, 0x54, 0x3f, 0x78, 0x78, 0x38, 0x66, 0x69, 0x67, 0x72, 0x54, 0x3e, 0x3d, 0x33, 0x33, 0x7a, 0x78, 0x3e, 0x76
```
The flag is:
```
accessdenied{1_l0v3_x86_4ss3mbly_5688qs5}
```
