Add Signed CSR payload validator to oemcrypto util and unit tests

Validator that can parse and validate SignedCsrPayload Cbor object.
The SignedCsrPayload is generated by
OEMCrypto_GetDeviceSignedCsrPayload() and will be put into prov4 CSR
request during factory uploading.

Test: opk_ta_p40
Bug: 300304834

Change-Id: Ib569dc22fe76dbaa98657e96aa4c93a272bbcd1b

libwvdrmengine/oemcrypto/util/include/signed_csr_payload_validator.h

@@ -0,0 +1,44 @@
+// Copyright 2023 Google LLC. All Rights Reserved. This file and proprietary
+// source code may only be used and distributed under the Widevine License
+// Agreement.
+//
+//  Reference implementation utilities of OEMCrypto APIs
+//
+#ifndef WVOEC_UTIL_SIGNED_CSR_PAYLOAD_VALIDATOR_H_
+#define WVOEC_UTIL_SIGNED_CSR_PAYLOAD_VALIDATOR_H_
+
+#include <sstream>
+#include <string>
+
+#include "cbor_validator.h"
+#include "cppbor.h"
+
+namespace wvoec {
+namespace util {
+// SignedCsrPayloadValidator parses and validates a Cbor struct of
+// SignedData<CsrPayload>. The definition of SignedData<T> and CsrPayload can be
+// found at:
+// https://source.corp.google.com/h/googleplex-android/platform/superproject/main/+/main:hardware/interfaces/security/rkp/aidl/android/hardware/security/keymint/generateCertificateRequestV2.cddl
+class SignedCsrPayloadValidator : public CborValidator {
+ public:
+  explicit SignedCsrPayloadValidator() {}
+  virtual ~SignedCsrPayloadValidator() override = default;
+  SignedCsrPayloadValidator(const SignedCsrPayloadValidator&) = delete;
+  SignedCsrPayloadValidator& operator=(const SignedCsrPayloadValidator&) =
+      delete;
+
+  // Verifies the Cbor struct of a client generated SignedData<CsrPayload>.
+  virtual CborMessageStatus Validate() override;
+  // Outputs SignedData<CsrPayload> in YAML.
+  virtual std::string GetFormattedMessage() const override;
+
+ private:
+  CborMessageStatus ValidateProtectedParams(
+      const cppbor::Bstr* protected_params);
+  CborMessageStatus ValidateDataToBeSigned(const cppbor::Bstr* data);
+  // Used to generate formatted message.
+  std::stringstream msg_ss_;
+};
+}  // namespace util
+}  // namespace wvoec
+#endif  // WVOEC_UTIL_SIGNED_CSR_PAYLOAD_VALIDATOR_H_