picoCTF - Rust fixme 1

Posted on Jan 27, 2026

Have you heard of Rust? Fix the syntax errors in this Rust file to print the flag! Download the Rust code here.

After retrieving the file, I downloaded and extracted the file

strikingsoul@ramones:~/Downloads$ gunzip fixme1.tar.gz 
strikingsoul@ramones:~/Downloads$ tar -xvf fixme1.tar 
fixme1/
fixme1/Cargo.toml
fixme1/Cargo.lock
fixme1/src/
fixme1/src/main.rs

I installed rust beforehand and tried to run the main file

strikingsoul@ramones:~/Downloads/fixme1$ rustc src/main.rs 
error: expected `;`, found keyword `let`
 --> src/main.rs:5:37
  |
5 |     let key = String::from("CSUCKS") // How do we end statement...
  |                                     ^ help: add `;` here
...
8 |     let hex_values = ["41", "30", "20", "63", "4a", "45", "54",...
  |     --- unexpected token

error: argument never used
  --> src/main.rs:26:9
   |
25 |         ":?", // How do we print out a variable in the println...
   |         ---- formatting specifier missing
26 |         String::from_utf8_lossy(&decrypted_buffer)
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ argument never used                                                                 
   |
help: format specifiers use curly braces, consider adding a format specifier
   |
25 |         ":?{}", // How do we print out a variable in the println function? 
   |            ++

error[E0432]: unresolved import `xor_cryptor`
 --> src/main.rs:1:5
  |
1 | use xor_cryptor::XORCryptor;
  |     ^^^^^^^^^^^ use of unresolved module or unlinked crate `xor_cryptor`                                                                
  |
help: you might be missing a crate named `xor_cryptor`, add it to your project and import it in your code
  |
1 + extern crate xor_cryptor;
  |

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`                                                                   

error: aborting due to 4 previous errors

Some errors have detailed explanations: E0425, E0432.
For more information about an error, try `rustc --explain E0425`.
strikingsoul@ramones:~/Downloads/fixme1$

Okay there was some errors

  1. Missing semicolon
  2. Typo in return statement
  3. Missing curly brackets in println

After fixing those and ran cargo build, I ran the program once again

strikingsoul@ramones:~/Downloads/fixme1$ ./target/debug/rust_proj 
"picoCTF{4r3_y0u_4_ru$t4c30n_n0w?}"

The flag is picoCTF{4r3_y0u_4_ru$t4c30n_n0w?}