> For the complete documentation index, see [llms.txt](https://alham-rizvi.gitbook.io/alhamrizvi/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://alham-rizvi.gitbook.io/alhamrizvi/picoctf-writeups/picoctf/binary-exploitation/rps.md).

# RPS

### RPS — PicoCTF Walkthrough (Binary Exploitation)

We’re given a Rock–Paper–Scissors game where we must win **5 times in a row** to get the flag.

### Core Logic

The important part is inside `play()`:

```c
if (strstr(player_turn, loses[computer_turn]))
```

Where:

```c
hands = {"rock", "paper", "scissors"};
loses = {"paper", "scissors", "rock"};
```

Meaning:

* If computer plays **rock** → you must input something containing `"paper"`
* If computer plays **paper** → input must contain `"scissors"`
* If computer plays **scissors** → input must contain `"rock"`

### Vulnerability

The program uses:

```c
strstr(player_turn, ...)
```

👉 `strstr()` checks for **substring**, not exact match.

So instead of giving one move, you can give **all moves at once**.

### Exploit

Input:

```
rockpaperscissors
```

This string contains:

* `"rock"`
* `"paper"`
* `"scissors"`

👉 No matter what the computer picks, your input always contains the winning move.

### Winning Condition

```c
if (wins >= 5) {
    puts(flag);
}
```

So just repeat the same input 5 times.

### Exploit Script (optional)

```python
from pwn import *

p = remote("host", port)

for _ in range(5):
    p.sendline("1")
    p.sendline("rockpaperscissors")

p.interactive()
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://alham-rizvi.gitbook.io/alhamrizvi/picoctf-writeups/picoctf/binary-exploitation/rps.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.