WebAuthn verification
The Cose namespace decodes the byte structures a WebAuthn or passkey ceremony produces and turns a COSE public key into a verifiable key. Signature checks go through KeyVerifier:
use RoundlyConsulting\Crypto\Facades\Crypto;
$authData = Crypto::authenticatorData($rawAuthenticatorData); // rpIdHash, flags, signCount, COSE key
$key = Crypto::coseKey($coseBytes); // COSE_Key bytes -> a verifiable public key
// or, from the attested credential: Crypto::coseKey($authData->coseKeyBytes)
$ok = Crypto::verifier()->verify($key, $signedData, $signature); // ES256 DER or raw, RS256, EdDSAOr call the classes the facade fronts directly:
use RoundlyConsulting\Crypto\Cose\AuthenticatorData;
use RoundlyConsulting\Crypto\Cose\CoseKey;
use RoundlyConsulting\Crypto\Signature\KeyVerifier;
$authData = AuthenticatorData::parse($rawAuthenticatorData); // rpIdHash, flags, signCount, COSE key
$key = CoseKey::fromCbor($coseBytes); // COSE_Key bytes -> a verifiable public key
$ok = (new KeyVerifier)->verify($key, $signedData, $signature); // ES256 DER or raw, RS256, EdDSACoseKey::fromCbor() — and Crypto::coseKey() — takes the COSE_Key bytes (a stored credential key, or $authData->coseKeyBytes), not a decoded array: a PHP string cannot say whether CBOR carried it as a byte string or a text string, and a strict COSE reader refuses a text-typed x, y, n or e.
The ceremony — challenge binding, origin, rpId hash, flag policy and sign-count reconciliation — stays in your relying-party code. This package only decodes bytes and checks signatures.
Authenticator data
$authData = AuthenticatorData::parse($rawAuthenticatorData);
$authData->rpIdHash; // 32 bytes
$authData->flags->userPresent; // UP
$authData->flags->userVerified; // UV
$authData->flags->backupEligible; // BE
$authData->flags->backupState; // BS
$authData->signCount; // int — unsigned 32-bit, never negative
$authData->aaguid; // ?string (present with attested credential data)
$authData->credentialId; // ?string
$authData->coseKey; // ?PublicKey — the verifiable credential key
$authData->coseKeyBytes; // ?string — the raw COSE key bytesAuthenticatorData::parse() validates structure strictly: a too-short buffer, a truncated or oversized credential id, a non-map COSE key or unexpected trailing bytes all throw MalformedCborException. Flags also expose attestedCredentialData (AT) and extensionData (ED).
Supported COSE keys
| COSE kty | Result | Algorithms / curves |
|---|---|---|
2 (EC2) | EcKey | ES256 / P-256, ES384 / P-384, ES512 / P-521 — alg must match the curve |
3 (RSA) | RsaKey | RS256 |
1 (OKP) | OkpKey | EdDSA / Ed25519 |
An unknown key type, curve or algorithm throws UnsupportedAlgorithmException; a missing or mistyped label throws MalformedCborException. The CoseAlgorithm enum maps the IANA identifiers (-7, -8, -35, -36, -257) to their JOSE equivalents via toSignatureAlgorithm().
The CBOR decoder
CborDecoder supports only the subset WebAuthn uses — integers, byte and text strings, definite-length arrays and maps, and false/true/null. It is canonical (CTAP2): indefinite lengths, tags, floats, non-shortest encodings and duplicate map keys are rejected, and nesting is capped at 16. It also refuses a text string that is not UTF-8 and a text map key PHP would store as an integer (“1”, “-1”), so a text label can never pass for the integer label it imitates:
use RoundlyConsulting\Crypto\Cose\CborDecoder;
$decoded = (new CborDecoder)->decode($attestationObjectBytes); // exactly one item; trailing bytes throw
$result = (new CborDecoder)->decodeFirst($bytes);
$result->value; // the decoded item
$result->bytesConsumed; // how many bytes it spannedShow your open-source love
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