Passki

A simple, secure, and easy-to-use WebAuthn/Passkey implementation for Rust.

Features

✨ Simple API - Easy-to-use interface for passkey registration and authentication
🔐 Multiple Algorithms - Support for EdDSA (Ed25519), ES256 (P-256), and RS256 (RSA)
🛡️ Security First - Built-in replay attack protection via signature counters
📦 Zero Runtime Dependencies - Only cryptography libraries, no web framework lock-in
✅ WebAuthn Level 2 Compliant - Follows the latest W3C specification
🦀 Pure Rust - Memory-safe implementation with no unsafe code

Installation

Add this to your Cargo.toml:

[dependencies]
passki = "0.1"

Quick Start

use passki::{
    Passki, AttestationConveyancePreference, ResidentKeyRequirement,
    UserVerificationRequirement, StoredPasskey,
};

// Initialize Passki with your relying party information
let passki = Passki::new(
    "example.com",              // Relying Party ID (domain)
    "https://example.com",      // Relying Party Origin
    "Example Corp"              // Relying Party Name
);

// Registration flow
// Step 1: Start registration and send challenge to client
let user_id = b"unique_user_identifier_12345"; // At least 16 bytes
let (registration_challenge, registration_state) = passki.start_passkey_registration(
    user_id,                                        // User ID (bytes)
    "alice@example.com",                            // Username
    "Alice Smith",                                  // Display name
    60000,                                          // Timeout (ms)
    AttestationConveyancePreference::None,          // Attestation
    ResidentKeyRequirement::Preferred,              // Resident key
    UserVerificationRequirement::Preferred,         // User verification
    None,                                           // Exclude existing credentials
).expect("user_id must be at least 16 bytes");

// Send registration_challenge to client (as JSON)
// Client uses WebAuthn API to create credential

// Step 2: Receive credential from client and complete registration
let stored_passkey = passki.finish_passkey_registration(
    &registration_credential,  // Credential from client
    &registration_state,       // State from step 1
)?;

// Save stored_passkey to your database associated with the user

// Authentication flow
// Step 1: Start authentication and send challenge to client
let (authentication_challenge, authentication_state) = passki.start_passkey_authentication(
    &user_passkeys,                            // User's stored passkeys
    60000,                                     // Timeout (ms)
    UserVerificationRequirement::Preferred,    // User verification
);

// Send authentication_challenge to client (as JSON)
// Client uses WebAuthn API to sign the challenge

// Step 2: Receive credential from client and verify authentication
let result = passki.finish_passkey_authentication(
    &authentication_credential,  // Credential from client
    &authentication_state,       // State from step 1
    &stored_passkey,             // User's passkey from database
)?;

// Update the counter in your database to prevent replay attacks
stored_passkey.counter = result.counter;

Supported Algorithms

Passki supports the following COSE algorithms:

EdDSA (Ed25519) - Algorithm ID: -8
ES256 (ECDSA with P-256 and SHA-256) - Algorithm ID: -7
RS256 (RSASSA-PKCS1-v1_5 with SHA-256) - Algorithm ID: -257

Security Considerations

🔒 Always use HTTPS in production to prevent man-in-the-middle attacks
🔄 Update signature counters after successful authentication to detect cloned authenticators
🎯 Verify origin matches your expected domain (Passki does this automatically)
💾 Store passkeys securely in your database with proper access controls
⏱️ Set appropriate timeouts for registration and authentication ceremonies
🔐 Use user verification when handling sensitive operations

Architecture

Passki follows a simple two-step pattern for both registration and authentication:

Start: Generate a challenge and return it to the client
Finish: Verify the response from the client

This design keeps state management simple and allows you to store session data however you prefer (in-memory, Redis, database, etc.).

Requirements

Rust 1.85 or later (Edition 2024)
A web server to handle HTTP requests
HTTPS in production (required by WebAuthn specification)

Examples

Check out the examples/ directory for a complete working example:

poem.rs - Full integration with Poem web framework showing registration and authentication flows

Run the example:

cargo run --example poem

Then visit http://localhost:3000 in your browser.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the Apache License, Version 2.0 (LICENSE or http://www.apache.org/licenses/LICENSE-2.0).

Acknowledgments

Passki is built on top of excellent Rust cryptography libraries:

ed25519-dalek - EdDSA signatures
p256 - ECDSA with P-256
rsa - RSA signatures
ciborium - CBOR encoding/decoding

passki 0.1.0