Derive Serialize, and Deserialize for the TcbError

Any error that is meant out be propagated out of an enclave needs to
be able to be serialized and deserialized from the trusted side into the
untrusted side.

`Clone` was also added as the changes needed for `Serialize` and
`Deserialize` made it possible for the error to be cloneable.

dcap/types/src/tcb.rs

@@ -14,6 +14,7 @@ use crate::{CertificationData, Quote3};
 use alloc::string::{String, ToString};
 use alloc::vec::Vec;
 use const_oid::ObjectIdentifier;
+use serde::{Deserialize, Serialize};
 use x509_cert::attr::{AttributeTypeAndValue, AttributeValue};
 use x509_cert::der::asn1::OctetStringRef;
 use x509_cert::der::{Decode, DecodePem};
@@ -52,12 +53,12 @@ const PCE_SVN_OID: ObjectIdentifier = ObjectIdentifier::new_unwrap("1.2.840.1137
 const FMSPC_OID: ObjectIdentifier = ObjectIdentifier::new_unwrap("1.2.840.113741.1.13.1.4");
 
 /// Error parsing TCB info from PCK leaf certificate
-#[derive(Debug, PartialEq, displaydoc::Display)]
+#[derive(Debug, PartialEq, displaydoc::Display, Clone, Serialize, Deserialize)]
 pub enum Error {
     /// Missing the SGX OID extension: {0}
     MissingSgxExtension(String),
     /// Failed to parse TCB info: {0}
-    Der(x509_cert::der::Error),
+    Der(String),
     /// Expected an FMSPC size of 6 bytes, got {0}
     FmspcSize(usize),
     /// Unsupported quote certification data, should be `PckCertificateChain`
@@ -66,7 +67,7 @@ pub enum Error {
 
 impl From<x509_cert::der::Error> for Error {
     fn from(err: x509_cert::der::Error) -> Self {
-        Error::Der(err)
+        Error::Der(err.to_string())
     }
 }