# Http Signature Normalization Actix-Web Extractor
_Experimental Extractor for request signatures_

- [crates.io](https://crates.io/crates/http-signature-normalization-actix-extractor)
- [docs.rs](https://docs.rs/http-signature-normalization-actix-extractor)
- [Hit me up on Mastodon](https://masto.asonix.dog/@asonix)

Http Signature Normalization is a minimal-dependency crate for producing HTTP Signatures with user-provided signing and verification. The API is simple; there's a series of steps for creation and verification with types that ensure reasonable usage. This library takes a different approach from the other implementation, which prefers Middlewares.

## Usage

This crate provides extensions the ClientRequest type from Actix Web, and provides middlewares for verifying HTTP Signatures, and optionally, Digest headers

#### First, add this crate to your dependencies
```toml
actix-rt = "2.7.0"
actix-web = "4.0.0"
thiserror = "1"
http-signature-normalization-actix-extractor = "0.1.0"
sha2 = "0.10"
```

#### Then, use it in your client

```rust
use actix_web::{http::StatusCode, web, App, HttpRequest, HttpResponse, HttpServer, ResponseError};
use http_signature_normalization_actix_extractor::{
    Algorithm, Config, ConfigGenerator, DeprecatedAlgorithm, Signed, VerifyKey,
};
use sha2::Sha256;

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    HttpServer::new(|| App::new().route("/", web::post().to(protected)))
        .bind("127.0.0.1:8010")?
        .run()
        .await
}

async fn protected(signed_request: Signed<String, Cfg, Sha256, Key>) -> &'static str {
    let (value, signature) = signed_request.into_parts();

    println!("{}", value);
    println!("{:#?}", signature);

    "hewwo, mr obama"
}

pub struct Cfg;

#[derive(Debug)]
pub struct Key;

#[derive(Debug, thiserror::Error)]
pub enum VerifyError {
    #[error("Unsupported algorithm")]
    Algorithm,

    #[error("Couldn't decode signature")]
    Decode,

    #[error("Invalid key")]
    Key,
}

impl ConfigGenerator for Cfg {
    fn config() -> Config {
        Config::new().require_header("accept")
    }
}

#[async_trait::async_trait(?Send)]
impl VerifyKey for Key {
    type Error = VerifyError;

    async fn init(
        _: &HttpRequest,
        key_id: &str,
        algorithm: Option<&Algorithm>,
    ) -> Result<Self, Self::Error> {
        match algorithm {
            Some(Algorithm::Hs2019 | Algorithm::Deprecated(DeprecatedAlgorithm::RsaSha256)) => (),
            _ => return Err(VerifyError::Algorithm),
        };

        if key_id != "my-key-id" {
            return Err(VerifyError::Key);
        }

        Ok(Key)
    }

    fn verify(&mut self, signature: &str, signing_string: &str) -> Result<bool, Self::Error> {
        use subtle::ConstantTimeEq;

        let decoded = base64::decode(&signature).map_err(|_| VerifyError::Decode)?;

        Ok(decoded.ct_eq(signing_string.as_bytes()).into())
    }
}

impl ResponseError for VerifyError {
    fn status_code(&self) -> StatusCode {
        StatusCode::BAD_REQUEST
    }

    fn error_response(&self) -> HttpResponse {
        HttpResponse::BadRequest().finish()
    }
}
```

### Contributing
Feel free to open issues for anything you find an issue with. Please note that any contributed code will be licensed under the AGPLv3.

### License
Copyright © 2022 Riley Trautman

HTTP Signature Normalization Actix Extractor is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

HTTP Signature Normalization Actix Extractor is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. This file is part of HTTP Signature Normalization Actix Extractor.

You should have received a copy of the GNU General Public License along with HTTP Signature Normalization Actix Extractor. If not, see [http://www.gnu.org/licenses/](http://www.gnu.org/licenses/).