gomcaptcha/mcaptcha-pow-ffi/src/lib.rs

// SPDX-FileCopyrightText: 2024 Aravinth Manivannan <realaravinth@batsense.net>
//
// SPDX-License-Identifier: Apache-2.0
// SPDX-License-Identifier: MIT

use mcaptcha_pow_sha256::ConfigBuilder;
use std::ffi::CStr;
use std::ffi::CString;

#[repr(C)]
pub struct ProofOfWork {
    pub nonce: u64,
    pub result: *const libc::c_char,
}

impl From<mcaptcha_pow_sha256::PoW<String>> for ProofOfWork {
    fn from(value: mcaptcha_pow_sha256::PoW<String>) -> Self {
        Self {
            nonce: value.nonce,
            result: CString::new(value.result).unwrap().into_raw(),
        }
    }
}

#[no_mangle]
pub extern "C" fn prove_work(
    salt: *const libc::c_char,
    phrase: *const libc::c_char,
    difficulty: u32,
) -> ProofOfWork {
    let (salt, phrase) = unsafe { (CStr::from_ptr(salt), CStr::from_ptr(phrase)) };
    let salt = salt.to_str().unwrap();
    let phrase = phrase.to_str().unwrap().to_string();
    let config = ConfigBuilder::default()
        .salt(salt.to_string())
        .build()
        .unwrap();
    config.prove_work(&phrase, difficulty).unwrap().into()
}

#[no_mangle]
pub extern "C" fn is_valid_proof(
    nonce: u64,
    result: *const libc::c_char,
    phrase: *const libc::c_char,
    salt: *const libc::c_char,
) -> bool {
    let (result, phrase, salt) = unsafe {
        (
            CStr::from_ptr(result),
            CStr::from_ptr(phrase),
            CStr::from_ptr(salt),
        )
    };
    let result = result.to_str().unwrap().to_string();
    let pow: mcaptcha_pow_sha256::PoW<String> = mcaptcha_pow_sha256::PoWBuilder::default()
        .nonce(nonce)
        .result(result)
        .build()
        .unwrap();
    let config = ConfigBuilder::default()
        .salt(salt.to_str().unwrap().to_string())
        .build()
        .unwrap();
    config.is_valid_proof(&pow, &phrase.to_str().unwrap().to_string())
}

#[no_mangle]
pub extern "C" fn is_sufficient_difficulty(
    nonce: u64,
    result: *const libc::c_char,
    salt: *const libc::c_char,
    difficulty: u32,
) -> bool {
    let (result, salt) = unsafe { (CStr::from_ptr(result), CStr::from_ptr(salt)) };
    let result = result.to_str().unwrap().to_string();
    let pow: mcaptcha_pow_sha256::PoW<String> = mcaptcha_pow_sha256::PoWBuilder::default()
        .nonce(nonce)
        .result(result)
        .build()
        .unwrap();
    let config = ConfigBuilder::default()
        .salt(salt.to_str().unwrap().to_string())
        .build()
        .unwrap();
    config.is_sufficient_difficulty(&pow, difficulty)
}

#[cfg(test)]
pub mod test {

    use super::*;
    use std::ffi::CString;

    #[test]
    fn test_pow() {
        let salt: String =
            "27b7eb6be3437b7da0d9329dea9a7c76f1640cd16d39fd94b5d0dd42c763c63c".into();
        let phrase: String =
            "b641c711c01079805a2a0888bf716b66c83419ab0c65455a49cb4d8b3e36c4ec".into();
        let difficulty = 50_000;

        let c = mcaptcha_pow_sha256::ConfigBuilder::default()
            .salt(salt.clone())
            .build()
            .unwrap();

        // calculate pow
        let mcaptcha_work = c.prove_work(&phrase, difficulty).unwrap();

        let ffi_work = super::prove_work(
            CString::new(salt.clone()).unwrap().into_raw(),
            CString::new(phrase.clone()).unwrap().into_raw(),
            difficulty,
        );

        assert_eq!(ffi_work.nonce, mcaptcha_work.nonce);

        let res = unsafe { CStr::from_ptr(ffi_work.result) };
        let res = res.to_str().unwrap();
        assert_eq!(res, mcaptcha_work.result);

        // verify pow
        assert!(super::is_valid_proof(
            mcaptcha_work.nonce,
            CString::new(mcaptcha_work.result.clone())
                .unwrap()
                .into_raw(),
            CString::new(phrase.clone()).unwrap().into_raw(),
            CString::new(salt.clone()).unwrap().into_raw(),
        ));

        assert!(!super::is_valid_proof(
            mcaptcha_work.nonce,
            CString::new(phrase.clone()).unwrap().into_raw(),
            CString::new(phrase.clone()).unwrap().into_raw(),
            CString::new(salt.clone()).unwrap().into_raw(),
        ));

        // is sufficient difficulty
        assert!(super::is_sufficient_difficulty(
            mcaptcha_work.nonce,
            CString::new(mcaptcha_work.result.clone())
                .unwrap()
                .into_raw(),
            CString::new(salt.clone()).unwrap().into_raw(),
            difficulty
        ));

        // is sufficient difficulty
        assert!(super::is_sufficient_difficulty(
            mcaptcha_work.nonce,
            CString::new(mcaptcha_work.result.clone())
                .unwrap()
                .into_raw(),
            CString::new(salt.clone()).unwrap().into_raw(),
            difficulty
        ));
    }
}