Updated AuthenticatorData and related objects to be byte encodable

Author: dimitribouniol

Sources/WebAuthn/Ceremonies/Registration/AttestationObject.swift

@@ -22,6 +22,29 @@ public struct AttestationObject: Sendable {
     let rawAuthenticatorData: [UInt8]
     let format: AttestationFormat
     let attestationStatement: CBOR
+    
+    init(
+        authenticatorData: AuthenticatorData,
+        rawAuthenticatorData: [UInt8],
+        format: AttestationFormat,
+        attestationStatement: CBOR
+    ) {
+        self.authenticatorData = authenticatorData
+        self.rawAuthenticatorData = rawAuthenticatorData
+        self.format = format
+        self.attestationStatement = attestationStatement
+    }
+    
+    init(
+        authenticatorData: AuthenticatorData,
+        format: AttestationFormat,
+        attestationStatement: CBOR
+    ) {
+        self.authenticatorData = authenticatorData
+        self.rawAuthenticatorData = authenticatorData.bytes
+        self.format = format
+        self.attestationStatement = attestationStatement
+    }
 
     func verify(
         relyingPartyID: String,

Sources/WebAuthn/Ceremonies/Shared/AuthenticatorData.swift

@@ -120,6 +120,29 @@ extension AuthenticatorData {
 
         return (data, length)
     }
+    
+    public var bytes: [UInt8] {
+        assert(relyingPartyIDHash.count == 32, "AuthenticatorData contains relyingPartyIDHash of length \(relyingPartyIDHash.count), which will likely not be decodable.")
+        var bytes: [UInt8] = []
+        
+        bytes += relyingPartyIDHash
+        bytes += flags.bytes
+        bytes += withUnsafeBytes(of: UInt32(counter).bigEndian) { Array($0) }
+        
+        assert((!flags.attestedCredentialData && attestedData == nil) || (flags.attestedCredentialData && attestedData != nil), "AuthenticatorData contains mismatch between attestedCredentialData flag and attestedData, which will likely not be decodable.")
+        if flags.attestedCredentialData, let attestedData {
+            bytes += attestedData.authenticatorAttestationGUID.bytes
+            bytes += withUnsafeBytes(of: UInt16(attestedData.credentialID.count).bigEndian) { Array($0) }
+            bytes += attestedData.credentialID
+            bytes += attestedData.publicKey
+        }
+        
+        assert((!flags.extensionDataIncluded && extData == nil) || (flags.extensionDataIncluded && extData != nil), "AuthenticatorData contains mismatch between extensionDataIncluded flag and extData, which will likely not be decodable.")
+        if flags.extensionDataIncluded, let extData {
+            bytes += extData
+        }
+        return bytes
+    }
 }
 
 /// A helper type to determine how many bytes were consumed when decoding CBOR items.

Sources/WebAuthn/Ceremonies/Shared/AuthenticatorFlags.swift

@@ -12,7 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-struct AuthenticatorFlags: Equatable, Sendable {
+public struct AuthenticatorFlags: Equatable, Sendable {
 
     /**
      Taken from https://w3c.github.io/webauthn/#sctn-authenticator-data
@@ -58,4 +58,15 @@ extension AuthenticatorFlags {
         attestedCredentialData = Self.isFlagSet(on: byte, at: .attestedCredentialDataIncluded)
         extensionDataIncluded = Self.isFlagSet(on: byte, at: .extensionDataIncluded)
     }
+    
+    public var bytes: [UInt8] {
+        var byte: UInt8 = 0
+        byte |= userPresent ? 1 << Bit.userPresent.rawValue : 0
+        byte |= userVerified ? 1 << Bit.userVerified.rawValue : 0
+        byte |= isBackupEligible ? 1 << Bit.backupEligible.rawValue : 0
+        byte |= isCurrentlyBackedUp ? 1 << Bit.backupState.rawValue : 0
+        byte |= attestedCredentialData ? 1 << Bit.attestedCredentialDataIncluded.rawValue : 0
+        byte |= extensionDataIncluded ? 1 << Bit.extensionDataIncluded.rawValue : 0
+        return [byte]
+    }
 }