Fix large blob support

This patch fixes some issues that we missed in
#18:
- largeBlobs request deserialization
- largeBlobKey in credential management
- empty response for largeBlobs command with set

src/ctap2.rs

@@ -111,13 +111,14 @@ impl<'a> Request<'a> {
                 Request::ClientPin(cbor_deserialize(data).map_err(CtapMappingError::ParsingError)?)
             }
 
+            Operation::LargeBlobs => {
+                Request::LargeBlobs(cbor_deserialize(data).map_err(CtapMappingError::ParsingError)?)
+            }
+
             // NB: FIDO Alliance "stole" 0x40 and 0x41, so these are not available
             Operation::Vendor(vendor_operation) => Request::Vendor(vendor_operation),
 
-            Operation::BioEnrollment
-            | Operation::PreviewBioEnrollment
-            | Operation::Config
-            | Operation::LargeBlobs => {
+            Operation::BioEnrollment | Operation::PreviewBioEnrollment | Operation::Config => {
                 debug_now!("unhandled CBOR operation {:?}", operation);
                 return Err(CtapMappingError::InvalidCommand(op).into());
             }

src/ctap2/credential_management.rs

@@ -107,4 +107,7 @@ pub struct Response {
     // 0x0A
     #[serde(skip_serializing_if = "Option::is_none")]
     pub cred_protect: Option<CredentialProtectionPolicy>,
+    // 0x0B
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub large_blob_key: Option<Bytes<32>>,
 }

src/ctap2/large_blobs.rs

@@ -25,9 +25,10 @@ pub struct Request<'a> {
     pub pin_uv_auth_protocol: Option<u32>,
 }
 
-#[derive(Clone, Debug, Eq, PartialEq, SerializeIndexed, DeserializeIndexed)]
+#[derive(Clone, Debug, Default, Eq, PartialEq, SerializeIndexed, DeserializeIndexed)]
 #[serde_indexed(offset = 1)]
 pub struct Response {
     // 0x01
-    pub config: Bytes<LARGE_BLOB_MAX_FRAGMENT_LENGTH>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub config: Option<Bytes<LARGE_BLOB_MAX_FRAGMENT_LENGTH>>,
 }