identity: Add multi-document presentation support.

Also fix a bug so the same AuthKey is used for several getEntries()
calls on a credential. This matches the behavior in the Jetpack.

Bug: 197965513
Test: New CTS tests and new screen in CtsVerifier
Change-Id: I344f44b5655f0977ee650b518ce669e3c8a7b47a
diff --git a/identity/Session.cpp b/identity/Session.cpp
new file mode 100644
index 0000000..98ba3d3
--- /dev/null
+++ b/identity/Session.cpp
@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2021, 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.
+ */
+
+#define LOG_TAG "credstore"
+
+#include <android-base/logging.h>
+#include <android/binder_manager.h>
+#include <android/hardware/identity/support/IdentityCredentialSupport.h>
+
+#include <android/security/identity/ICredentialStore.h>
+#include <android/security/identity/ISession.h>
+
+#include "Session.h"
+#include "Util.h"
+
+namespace android {
+namespace security {
+namespace identity {
+
+using std::optional;
+
+using ::android::hardware::identity::IPresentationSession;
+using ::android::hardware::identity::IWritableIdentityCredential;
+
+using ::android::hardware::identity::support::ecKeyPairGetPkcs12;
+using ::android::hardware::identity::support::ecKeyPairGetPrivateKey;
+using ::android::hardware::identity::support::ecKeyPairGetPublicKey;
+using ::android::hardware::identity::support::hexdump;
+using ::android::hardware::identity::support::sha256;
+
+Status Session::getEphemeralKeyPair(vector<uint8_t>* _aidl_return) {
+    vector<uint8_t> keyPair;
+    Status status = halBinder_->getEphemeralKeyPair(&keyPair);
+    if (!status.isOk()) {
+        return halStatusToGenericError(status);
+    }
+    time_t nowSeconds = std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
+    time_t validityNotBefore = nowSeconds;
+    time_t validityNotAfter = nowSeconds + 24 * 60 * 60;
+    optional<vector<uint8_t>> pkcs12Bytes = ecKeyPairGetPkcs12(keyPair,
+                                                               "ephemeralKey",  // Alias for key
+                                                               "0",  // Serial, as a decimal number
+                                                               "Credstore",      // Issuer
+                                                               "Ephemeral Key",  // Subject
+                                                               validityNotBefore, validityNotAfter);
+    if (!pkcs12Bytes) {
+        return Status::fromServiceSpecificError(ICredentialStore::ERROR_GENERIC,
+                                                "Error creating PKCS#12 structure for key pair");
+    }
+    *_aidl_return = pkcs12Bytes.value();
+    return Status::ok();
+}
+
+Status Session::setReaderEphemeralPublicKey(const vector<uint8_t>& publicKey) {
+    Status status = halBinder_->setReaderEphemeralPublicKey(publicKey);
+    if (!status.isOk()) {
+        return halStatusToGenericError(status);
+    }
+    return Status::ok();
+}
+
+Status Session::setSessionTranscript(const vector<uint8_t>& sessionTranscript) {
+    Status status = halBinder_->setSessionTranscript(sessionTranscript);
+    if (!status.isOk()) {
+        return halStatusToGenericError(status);
+    }
+    return Status::ok();
+}
+
+Status Session::getCredentialForPresentation(const string& credentialName,
+                                             sp<ICredential>* _aidl_return) {
+    return store_->getCredentialCommon(credentialName, cipherSuite_, halBinder_, _aidl_return);
+}
+
+Status Session::getAuthChallenge(int64_t* _aidl_return) {
+    *_aidl_return = 0;
+    int64_t authChallenge;
+    Status status = halBinder_->getAuthChallenge(&authChallenge);
+    if (!status.isOk()) {
+        return halStatusToGenericError(status);
+    }
+    *_aidl_return = authChallenge;
+    return Status::ok();
+}
+
+}  // namespace identity
+}  // namespace security
+}  // namespace android