# A Rust implementation of Prefixed API Key

This library is a Rust implementation of the [Prefixed API Key](https://github.com/seamapi/prefixed-api-key) typescript library. Though its interface differs slightly from the typescript version, this library provides the same set of features and functionality as the typescript version.

## Prefixed API Key (Seam-style)

> Example key: `mycompany_BRTRKFsL_51FwqftsmMDHHbJAMEXXHCgG`

> [See discussion on Hacker News](https://news.ycombinator.com/item?id=31333933#31336542)

Seam-style API Keys have many advantages:

- Double clicking the api key selects the entire api key
- The alphabet is standard across languages thanks [to the base58 RFC](https://datatracker.ietf.org/doc/html/draft-msporny-base58) and its usage in cryptocurrencies
- They are shorter than hex and base32 api keys
- They have prefixes [allowing secret scanning by github](https://docs.github.com/en/code-security/secret-scanning/about-secret-scanning)
- They have a hashed component so the server doesn't need to store the api key (reducing attack surface)
- They have unhashed short tokens which can be mutually used by the server and key bearer/customer to identify the api key
- They default to roughly the same number of entropy bits as UUIDv4

### The Format

Seam-style api keys look like this:

```ignore
mycompany_BRTRKFsL_51FwqftsmMDHHbJAMEXXHCgG
```

Let's break down each component of the API key...

```ignore
mycompany ..._...  BRTRKFsL ..._...  51FwqftsmMDHHbJAMEXXHCgG
^                  ^                 ^
Prefix             Short Token       Long Token
```

- The Prefix is used to identify the company or service creating the API Key.
  This is very helpful in secret scanning.
- The Short Token is stored by both the server and the key bearer/customer, it
  can be used to identify an API key in logs or displayed on a customer's
  dashboard. A token can be blocklisted by its short token.
- The Long Token is how we authenticate this key. The long token is never stored
  on the server, but a hash of it is stored on the server. When we receive an
  incoming request, we search our database for `short_token` and `hash(long_token)`.

## Getting Started

The original Typescript implementation of Prefixed API Keys has a few technical decisions hardcoded,
but this crates aims to give full control over which hashing algorithm and random number
generator are used. However this adds more complexity than may be desirable, so helpers are
available to make configuration relatively painless.

By installing the crate with the `sha2` feature flag, you can create an almost-entirely configured
`PrefixedApiKeyController` instance using the `seam_defaults` function, which configures the
controller the same way as Seam's Typescript implementation.

```rust
use prefixed_api_key::PrefixedApiKeyController;

fn main() {
    // A controller using `rand::rng::OsRng` as the RNG source, and
    // `sha2::Sha256` as the hashing algorithm.
    let builder_result = PrefixedApiKeyController::configure()
        .prefix("mycompany".to_owned())
        .seam_defaults()
        .finalize();

    assert!(builder_result.is_ok());

    let controller = builder_result.unwrap();

    // Generate a new PrefixedApiKey
    let (pak, hash) = controller.try_generate_key_and_hash().unwrap();

    // Assert that the returned key matches the hash
    assert!(controller.check_hash(&pak, &hash));

    // Stringify the key to be sent to the user. This creates a string from the
    // PrefixedApiKey which follows the `<prefix>_<short token>_<long token>` convention
    let pak_string = pak.to_string();
}
```

Using the `seam_defaults()` function with the `sha2` feature flag is equivalent to doing
the following without using the `sha2` feature:

```rust
use sha2::Sha256;
use prefixed_api_key::PrefixedApiKeyController;

fn main() {
    let controller = PrefixedApiKeyController::<_, Sha256>::configure()
        .prefix("mycompany".to_owned())
        .rng_osrng()
        .short_token_length(8)
        .long_token_length(24)
        .finalize();
}
```

## Testing

Library tests:

```ignore
cargo test --all-features
```

Verify minimum supported rust version (MSRV):

```ignore
cargo install cargo-msrv
cargo msrv verify
```

Testing code hygiene requires `clippy` and `rustfmt` components:

```ignore
cargo fmt --all -- --check
cargo clippy -- -D warnings
```

The library and hygiene tests will be run for all examples too