Identity Credential: Switch default implementation to use libeic.

Introduce platform-neutral C library ("libeic") which can be used to
implement an Identity Credential Trusted Application/Applet in Secure
Hardware.

The libeic library is intentionally low-level, has no dependencies
(not even libc), uses very little run-time memory (less than 500 bytes
during a provisioning or presentation session), and doesn't
dynamically allocate any memory. Crypto routines are provided by the
library user through a simple crypto interface defined in EicOps.

Also provide an Android-side HAL implementation designed to
communicate with libeic running in Secure Hardware outside
Android. Abstract out communications between HAL and TA in a couple of
SecureHardwareProxy* classes which mimic libeic 1:1.

The default implementation of the HAL is a combination of the
aforementioned HAL using libeic in-process backed by BoringSSL for the
crypto bits.

Test: atest VtsHalIdentityTargetTest
Test: atest android.security.identity.cts
Bug: 170146643
Change-Id: I3bf43fa7fd9362f94023052591801f2094a04607
diff --git a/identity/aidl/default/EicOpsImpl.h b/identity/aidl/default/EicOpsImpl.h
new file mode 100644
index 0000000..333cdce
--- /dev/null
+++ b/identity/aidl/default/EicOpsImpl.h
@@ -0,0 +1,46 @@
+/*
+ * Copyright 2020, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_HARDWARE_IDENTITY_EIC_OPS_IMPL_H
+#define ANDROID_HARDWARE_IDENTITY_EIC_OPS_IMPL_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+// Add whatever includes are needed for definitions below.
+//
+
+#include <openssl/hmac.h>
+#include <openssl/sha.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Set the following defines to match the implementation of the supplied
+// eicOps*() operations. See EicOps.h for details.
+//
+
+#define EIC_SHA256_CONTEXT_SIZE sizeof(SHA256_CTX)
+
+#define EIC_HMAC_SHA256_CONTEXT_SIZE sizeof(HMAC_CTX)
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // ANDROID_HARDWARE_IDENTITY_EMBEDDED_IC_H