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Rust fixme 1

  • Description: Have you heard of Rust? Fix the syntax errors in this Rust file to print the flag!
  • Difficulty: Easy

🔎 Solution​

Begin by extracting the provided archive using tar -xzf fixme1.tar.gz. This will unpack the project directory, revealing the following files: Cargo.lock, Cargo.toml, src/main.rs

To compile and run the project, execute cargo run. At this stage, the program will fail to compile, throwing three errors. Let's walk through and resolve them one by one:

  1. Line 5 - A semicolon ; is missing at the end of the statement.
error: expected `;`, found keyword `let`
 --> src/main.rs:5:37
  |
5 |     let key = String::from("CSUCKS") // How do we end statements in Rust?
  |

Fixing by adding a semicolon at the end of the line:

let key = String::from("CSUCKS"); // How do we end statements in Rust?
  1. Line 18 - In Rust, to return a value from a function, use the return keyword.
error[E0425]: cannot find value `ret` in this scope
  --> src/main.rs:18:9
   |
18 |         ret; // How do we return in rust?
   |         ^^^ help: a local variable with a similar name exists: `res`

Change the line to:

// Create decrpytion object
let res = XORCryptor::new(&key);
if res.is_err() {
    return ; // How do we return in rust?
}
  1. Line 25 - When printing a variable using println!, use {} as a placeholder.
error: argument never used
  --> src/main.rs:26:9
   |
25 |         ":?", // How do we print out a variable in the println function?

Change ":?" to "{}"

    println!(
        "{}", // How do we print out a variable in the println function? 
        String::from_utf8_lossy(&decrypted_buffer)
    );

After fixing these issues, run the program again. If all corrections are applied correctly, the flag will be displayed.

┌──(kali㉿kali)-[~/Desktop/fixme1]
└─$ cargo run            
   Compiling rust_proj v0.1.0 (/home/kali/Desktop/fixme1)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.74s
     Running `target/debug/rust_proj`
picoCTF{4r3_y0u_4_ru$t4c30n_n0w?}

⚙️ Installing Rust​

If your system doesn't have Rust installed or cannot build the project, you can set it up with the following commands:

sudo apt update
sudo apt install curl build-essential
curl https://sh.rustup.rs -sSf | sh

Once installation is complete, initialize the Rust environment by running:

source $HOME/.cargo/env

You can verify the installation with:

cargo --version
rustc --version

🚩Flag​

picoCTF{4r3_y0u_4_ru$t4c30n_n0w?}