NC8 Mainframe Mangagement Interface is a series of CTF challenges in NSEC 2018. You can find the challenges in ringzer0ctf.
Spoiler Alert: If you haven't solve the challenges yet, do not read any further. The NC8 challenges are really fun to tackle by yourself.
Every instruction takes up 1 byte. The first 4 bits represent the instruction type, and the last 4 bits represent either registers, signed numbers or relative offsets (depending on the instruction).
| Opcode | Assembly |
|---|---|
| 0X | int <num> |
| 1X | mov <reg>, <num> |
| 2X | mov [<reg>], reg |
| 3X | mov <reg>, [<reg>] |
| 4X | add <reg>, <reg> |
| 5X | xor <reg>, <reg> |
| 6X | and <reg>, <reg> |
| 7X | or <reg>, <reg> |
| 8X | mul <reg>, <reg> |
| 9X | div <reg>, <reg> |
| AX | jz <rel> |
| BX | jnz <rel> |
| CX | jmp <rel> |
| DX | push <reg> |
| EX | push [<rel>] |
| FX | pop <reg> |
| Code | Description |
|---|---|
| 0 | Exit |
| 1 | Read one byte to r0 |
| 2 | Print one byte from r0 |
| 4 | Write the 32 secret bytes to [r0] (part4) |
| 10 & 11 | See the manual |
Warning: I didn't try to make my code easy to read, the assembler & disassembler is quite error prone and terrible.
cargo run data/partXXX for debugger.
cargo run --bin disasm data/partXXX for disassembler.
cargo run --bin asm data/partXXX.asm for assembler.
