JsWebAuthnProvider

JavaScript/Browser implementation of WebAuthnProvider using the Web Authentication API.

This provider uses navigator.credentials to create and assert WebAuthn credentials in a browser environment. It requests ES256 (secp256r1, algorithm -7) keys and returns the public key as an uncompressed 65-byte secp256r1 point (0x04 prefix + X + Y).

For public key extraction during registration, three strategies are used in order of preference:

1. response.getPublicKey() -- returns SubjectPublicKeyInfo (SPKI); the last 65 bytes are the uncompressed secp256r1 point. Preferred because it is the most direct path.

2. Parse authenticatorData from the CBOR-encoded attestation object to locate the COSE key structure and extract the X/Y coordinates.

3. Pattern-match the raw attestationObject bytes for the COSE ES256 key prefix (a5 01 02 03 26 20 01 21 58 20) and extract X/Y coordinates.

This class is only usable in browser environments. Attempting to use it in Node.js (where navigator.credentials is not available) will throw WebAuthnException.NotSupported.

Parameters

val provider = JsWebAuthnProvider(
    rpId = "example.com",
    rpName = "My Stellar App"
)

// Register a new passkey
val registration = provider.register(
    challenge = challengeBytes,
    userId = userIdBytes,
    userName = "alice@example.com"
)
println("Credential ID: ${registration.credentialId.size} bytes")
println("Public key: ${registration.publicKey.size} bytes")

// Authenticate with the passkey
val authentication = provider.authenticate(challenge = payloadHash)
println("Signature: ${authentication.signature.size} bytes")