utils.go

package virtualwebauthn

import (
	"crypto/rand"

	"github.com/fxamacker/cbor/v2"
)

type clientData struct {
	Type      string `json:"type"`
	Challenge string `json:"challenge"`
	Origin    string `json:"origin"`
}

func marshalCbor(v any) []byte {
	encoder, err := cbor.CTAP2EncOptions().EncMode()
	if err != nil {
		panic("failed to instantiate cbor encoder")
	}
	bytes, err := encoder.Marshal(v)
	if err != nil {
		panic("failed to encode to cbor")
	}
	return bytes
}

func randomBytes(length int) []byte {
	bytes := make([]byte, length)
	num, err := rand.Read(bytes)
	if err != nil || num != length {
		panic("failed to generate random bytes")
	}
	return bytes
}

func bigEndianBytes[T interface{ int | uint32 }](value T, length int) []byte {
	bytes := make([]byte, length)
	for i := 0; i < length; i++ {
		shift := (length - i - 1) * 8
		bytes[i] = byte(value >> shift & 0xFF)
	}
	return bytes
}

func authenticatorDataFlags(userPresent, userVerified, backupEligible, backupState, attestation, extensions bool) byte {
	// https://www.w3.org/TR/webauthn/#flags
	flags := byte(0)
	if userPresent {
		flags |= 1 << 0
	}
	if userVerified {
		flags |= 1 << 2
	}
	if backupEligible {
		flags |= 1 << 3
	}
	if backupState {
		flags |= 1 << 4
	}
	if attestation {
		flags |= 1 << 6
	}
	if extensions { // extensions not supported yet
		flags |= 1 << 7
	}
	return flags
}