hessra-token 0.1.1

# Hessra Token

Core verification library for Hessra authentication tokens.

This crate provides functionality for verifying and attenuating biscuit tokens
used in the Hessra authentication system. It is designed to be WASM-compatible
and has no networking dependencies.

## Features

- **Token verification**: Verify tokens without contacting the authorization server
- **Token attestation**: Add service node attestations to tokens
- **WASM compatibility**: Can be compiled to WebAssembly for use in browsers (via the `wasm` feature)

## Usage

### Basic Token Verification

```rust
use hessra_token::{verify_token, biscuit_key_from_string};

fn main() -> Result<(), hessra_token::TokenError> {
    // Your base64-encoded token
    let token_base64 = "YOUR_TOKEN_STRING";

    // Parse public key from string format (ed25519/{hex} or secp256r1/{hex})
    let public_key = biscuit_key_from_string("ed25519/01234567890abcdef".to_string())?;

    // Verify the token
    verify_token(token_base64, public_key, "user123", "resource456")?;

    println!("Token verification successful!");
    Ok(())
}
```

### Service Chain Verification

For tokens that need to be verified against a chain of service nodes:

```rust
use hessra_token::{verify_service_chain_token, biscuit_key_from_string, ServiceNode};

fn main() -> Result<(), hessra_token::TokenError> {
    let token_base64 = "YOUR_TOKEN_STRING";
    let public_key = biscuit_key_from_string("ed25519/01234567890abcdef".to_string())?;

    // Define the service chain
    let service_nodes = vec![
        ServiceNode {
            component: "service1".to_string(),
            public_key: "ed25519/service1key".to_string(),
        },
        ServiceNode {
            component: "service2".to_string(),
            public_key: "ed25519/service2key".to_string(),
        },
    ];

    // Verify the token with service chain
    verify_service_chain_token(
        token_base64,
        public_key,
        "user123",
        "resource456",
        service_nodes,
        None, // Verify full chain, or specify a component to verify up to
    )?;

    println!("Token verification successful!");
    Ok(())
}
```

### Token Attenuation

To add service node attestations to tokens:

```rust
use hessra_token::{add_service_node_attenuation, decode_token, encode_token, KeyPair, PublicKey};

fn main() -> Result<(), hessra_token::TokenError> {
    let token_base64 = "YOUR_TOKEN_STRING";
    let token_bytes = decode_token(token_base64)?;

    // Public key for token verification
    let public_key = PublicKey::from_bytes(b"example_key", biscuit_auth::Algorithm::Ed25519)?;

    // Service node key pair
    let service_keypair = KeyPair::new();

    // Add service node attenuation
    let attenuated_token = add_service_node_attenuation(
        token_bytes,
        public_key,
        "my-service",
        &service_keypair,
    )?;

    // Encode back to base64 for storage or transmission
    let attenuated_token_base64 = encode_token(&attenuated_token);

    println!("Token attenuated: {}", attenuated_token_base64);
    Ok(())
}
```

## WebAssembly Support

To compile with WebAssembly support, enable the `wasm` feature:

```toml
[dependencies]
hessra-token = { version = "0.1.1", features = ["wasm"] }
```

## Lower-level API

If you need more control, lower-level functions are also available:

- `verify_biscuit_local` - Directly verify binary token data
- `verify_service_chain_biscuit_local` - Verify binary token data with service chain
- `parse_token` - Parse a base64 token string into a Biscuit for inspection
- `decode_token` - Convert base64 encoded token to binary data
- `encode_token` - Convert binary token data to base64 string

## Development

This crate is part of the Hessra SDK refactoring project. It provides the token functionality
that was previously part of the monolithic SDK.