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

1 files changed, 0 insertions, 864 deletions

diff --git a/identity/aidl/default/IdentityCredential.cpp b/identity/aidl/default/IdentityCredential.cpp
deleted file mode 100644
index dfcd4f557f..0000000000
--- a/identity/aidl/default/IdentityCredential.cpp
+++ /dev/null
@@ -1,864 +0,0 @@
-/*
- * Copyright 2019, 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 "IdentityCredential"
-
-#include "IdentityCredential.h"
-#include "IdentityCredentialStore.h"
-#include "Util.h"
-
-#include <android/hardware/identity/support/IdentityCredentialSupport.h>
-
-#include <string.h>
-
-#include <android-base/logging.h>
-#include <android-base/stringprintf.h>
-
-#include <cppbor.h>
-#include <cppbor_parse.h>
-
-namespace aidl::android::hardware::identity {
-
-using ::aidl::android::hardware::keymaster::Timestamp;
-using ::android::base::StringPrintf;
-using ::std::optional;
-
-using namespace ::android::hardware::identity;
-
-int IdentityCredential::initialize() {
-    if (credentialData_.size() == 0) {
-        LOG(ERROR) << "CredentialData is empty";
-        return IIdentityCredentialStore::STATUS_INVALID_DATA;
-    }
-    auto [item, _, message] = cppbor::parse(credentialData_);
-    if (item == nullptr) {
-        LOG(ERROR) << "CredentialData is not valid CBOR: " << message;
-        return IIdentityCredentialStore::STATUS_INVALID_DATA;
-    }
-
-    const cppbor::Array* arrayItem = item->asArray();
-    if (arrayItem == nullptr || arrayItem->size() != 3) {
-        LOG(ERROR) << "CredentialData is not an array with three elements";
-        return IIdentityCredentialStore::STATUS_INVALID_DATA;
-    }
-
-    const cppbor::Tstr* docTypeItem = (*arrayItem)[0]->asTstr();
-    const cppbor::Bool* testCredentialItem =
-            ((*arrayItem)[1]->asSimple() != nullptr ? ((*arrayItem)[1]->asSimple()->asBool())
-                                                    : nullptr);
-    const cppbor::Bstr* encryptedCredentialKeysItem = (*arrayItem)[2]->asBstr();
-    if (docTypeItem == nullptr || testCredentialItem == nullptr ||
-        encryptedCredentialKeysItem == nullptr) {
-        LOG(ERROR) << "CredentialData unexpected item types";
-        return IIdentityCredentialStore::STATUS_INVALID_DATA;
-    }
-
-    docType_ = docTypeItem->value();
-    testCredential_ = testCredentialItem->value();
-
-    vector<uint8_t> hardwareBoundKey;
-    if (testCredential_) {
-        hardwareBoundKey = support::getTestHardwareBoundKey();
-    } else {
-        hardwareBoundKey = getHardwareBoundKey();
-    }
-
-    const vector<uint8_t>& encryptedCredentialKeys = encryptedCredentialKeysItem->value();
-    const vector<uint8_t> docTypeVec(docType_.begin(), docType_.end());
-    optional<vector<uint8_t>> decryptedCredentialKeys =
-            support::decryptAes128Gcm(hardwareBoundKey, encryptedCredentialKeys, docTypeVec);
-    if (!decryptedCredentialKeys) {
-        LOG(ERROR) << "Error decrypting CredentialKeys";
-        return IIdentityCredentialStore::STATUS_INVALID_DATA;
-    }
-
-    auto [dckItem, dckPos, dckMessage] = cppbor::parse(decryptedCredentialKeys.value());
-    if (dckItem == nullptr) {
-        LOG(ERROR) << "Decrypted CredentialKeys is not valid CBOR: " << dckMessage;
-        return IIdentityCredentialStore::STATUS_INVALID_DATA;
-    }
-    const cppbor::Array* dckArrayItem = dckItem->asArray();
-    if (dckArrayItem == nullptr || dckArrayItem->size() != 2) {
-        LOG(ERROR) << "Decrypted CredentialKeys is not an array with two elements";
-        return IIdentityCredentialStore::STATUS_INVALID_DATA;
-    }
-    const cppbor::Bstr* storageKeyItem = (*dckArrayItem)[0]->asBstr();
-    const cppbor::Bstr* credentialPrivKeyItem = (*dckArrayItem)[1]->asBstr();
-    if (storageKeyItem == nullptr || credentialPrivKeyItem == nullptr) {
-        LOG(ERROR) << "CredentialKeys unexpected item types";
-        return IIdentityCredentialStore::STATUS_INVALID_DATA;
-    }
-    storageKey_ = storageKeyItem->value();
-    credentialPrivKey_ = credentialPrivKeyItem->value();
-
-    return IIdentityCredentialStore::STATUS_OK;
-}
-
-ndk::ScopedAStatus IdentityCredential::deleteCredential(
-        vector<uint8_t>* outProofOfDeletionSignature) {
-    cppbor::Array array = {"ProofOfDeletion", docType_, testCredential_};
-    vector<uint8_t> proofOfDeletion = array.encode();
-
-    optional<vector<uint8_t>> signature = support::coseSignEcDsa(credentialPrivKey_,
-                                                                 proofOfDeletion,  // payload
-                                                                 {},               // additionalData
-                                                                 {});  // certificateChain
-    if (!signature) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_FAILED, "Error signing data"));
-    }
-
-    *outProofOfDeletionSignature = signature.value();
-    return ndk::ScopedAStatus::ok();
-}
-
-ndk::ScopedAStatus IdentityCredential::createEphemeralKeyPair(vector<uint8_t>* outKeyPair) {
-    optional<vector<uint8_t>> kp = support::createEcKeyPair();
-    if (!kp) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_FAILED, "Error creating ephemeral key pair"));
-    }
-
-    // Stash public key of this key-pair for later check in startRetrieval().
-    optional<vector<uint8_t>> publicKey = support::ecKeyPairGetPublicKey(kp.value());
-    if (!publicKey) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_FAILED,
-                "Error getting public part of ephemeral key pair"));
-    }
-    ephemeralPublicKey_ = publicKey.value();
-
-    *outKeyPair = kp.value();
-    return ndk::ScopedAStatus::ok();
-}
-
-ndk::ScopedAStatus IdentityCredential::setReaderEphemeralPublicKey(
-        const vector<uint8_t>& publicKey) {
-    readerPublicKey_ = publicKey;
-    return ndk::ScopedAStatus::ok();
-}
-
-ndk::ScopedAStatus IdentityCredential::createAuthChallenge(int64_t* outChallenge) {
-    uint64_t challenge = 0;
-    while (challenge == 0) {
-        optional<vector<uint8_t>> bytes = support::getRandom(8);
-        if (!bytes) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_FAILED,
-                    "Error getting random data for challenge"));
-        }
-
-        challenge = 0;
-        for (size_t n = 0; n < bytes.value().size(); n++) {
-            challenge |= ((bytes.value())[n] << (n * 8));
-        }
-    }
-
-    *outChallenge = challenge;
-    authChallenge_ = challenge;
-    return ndk::ScopedAStatus::ok();
-}
-
-// TODO: this could be a lot faster if we did all the splitting and pubkey extraction
-// ahead of time.
-bool checkReaderAuthentication(const SecureAccessControlProfile& profile,
-                               const vector<uint8_t>& readerCertificateChain) {
-    optional<vector<uint8_t>> acpPubKey =
-            support::certificateChainGetTopMostKey(profile.readerCertificate.encodedCertificate);
-    if (!acpPubKey) {
-        LOG(ERROR) << "Error extracting public key from readerCertificate in profile";
-        return false;
-    }
-
-    optional<vector<vector<uint8_t>>> certificatesInChain =
-            support::certificateChainSplit(readerCertificateChain);
-    if (!certificatesInChain) {
-        LOG(ERROR) << "Error splitting readerCertificateChain";
-        return false;
-    }
-    for (const vector<uint8_t>& certInChain : certificatesInChain.value()) {
-        optional<vector<uint8_t>> certPubKey = support::certificateChainGetTopMostKey(certInChain);
-        if (!certPubKey) {
-            LOG(ERROR)
-                    << "Error extracting public key from certificate in chain presented by reader";
-            return false;
-        }
-        if (acpPubKey.value() == certPubKey.value()) {
-            return true;
-        }
-    }
-    return false;
-}
-
-bool checkUserAuthentication(const SecureAccessControlProfile& profile,
-                             const VerificationToken& verificationToken,
-                             const HardwareAuthToken& authToken, uint64_t authChallenge) {
-    if (profile.secureUserId != authToken.userId) {
-        LOG(ERROR) << "secureUserId in profile (" << profile.secureUserId
-                   << ") differs from userId in authToken (" << authToken.userId << ")";
-        return false;
-    }
-
-    if (verificationToken.timestamp.milliSeconds == 0) {
-        LOG(ERROR) << "VerificationToken is not set";
-        return false;
-    }
-    if (authToken.timestamp.milliSeconds == 0) {
-        LOG(ERROR) << "AuthToken is not set";
-        return false;
-    }
-
-    if (profile.timeoutMillis == 0) {
-        if (authToken.challenge == 0) {
-            LOG(ERROR) << "No challenge in authToken";
-            return false;
-        }
-
-        if (authToken.challenge != int64_t(authChallenge)) {
-            LOG(ERROR) << "Challenge in authToken (" << uint64_t(authToken.challenge) << ") "
-                       << "doesn't match the challenge we created (" << authChallenge << ")";
-            return false;
-        }
-        return true;
-    }
-
-    // Timeout-based user auth follows. The verification token conveys what the
-    // time is right now in the environment which generated the auth token. This
-    // is what makes it possible to do timeout-based checks.
-    //
-    const Timestamp now = verificationToken.timestamp;
-    if (authToken.timestamp.milliSeconds > now.milliSeconds) {
-        LOG(ERROR) << "Timestamp in authToken (" << authToken.timestamp.milliSeconds
-                   << ") is in the future (now: " << now.milliSeconds << ")";
-        return false;
-    }
-    if (now.milliSeconds > authToken.timestamp.milliSeconds + profile.timeoutMillis) {
-        LOG(ERROR) << "Deadline for authToken (" << authToken.timestamp.milliSeconds << " + "
-                   << profile.timeoutMillis << " = "
-                   << (authToken.timestamp.milliSeconds + profile.timeoutMillis)
-                   << ") is in the past (now: " << now.milliSeconds << ")";
-        return false;
-    }
-    return true;
-}
-
-ndk::ScopedAStatus IdentityCredential::setRequestedNamespaces(
-        const vector<RequestNamespace>& requestNamespaces) {
-    requestNamespaces_ = requestNamespaces;
-    return ndk::ScopedAStatus::ok();
-}
-
-ndk::ScopedAStatus IdentityCredential::setVerificationToken(
-        const VerificationToken& verificationToken) {
-    verificationToken_ = verificationToken;
-    return ndk::ScopedAStatus::ok();
-}
-
-ndk::ScopedAStatus IdentityCredential::startRetrieval(
-        const vector<SecureAccessControlProfile>& accessControlProfiles,
-        const HardwareAuthToken& authToken, const vector<uint8_t>& itemsRequest,
-        const vector<uint8_t>& signingKeyBlob, const vector<uint8_t>& sessionTranscript,
-        const vector<uint8_t>& readerSignature, const vector<int32_t>& requestCounts) {
-    std::unique_ptr<cppbor::Item> sessionTranscriptItem;
-    if (sessionTranscript.size() > 0) {
-        auto [item, _, message] = cppbor::parse(sessionTranscript);
-        if (item == nullptr) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_INVALID_DATA,
-                    "SessionTranscript contains invalid CBOR"));
-        }
-        sessionTranscriptItem = std::move(item);
-    }
-    if (numStartRetrievalCalls_ > 0) {
-        if (sessionTranscript_ != sessionTranscript) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_SESSION_TRANSCRIPT_MISMATCH,
-                    "Passed-in SessionTranscript doesn't match previously used SessionTranscript"));
-        }
-    }
-    sessionTranscript_ = sessionTranscript;
-
-    // If there is a signature, validate that it was made with the top-most key in the
-    // certificate chain embedded in the COSE_Sign1 structure.
-    optional<vector<uint8_t>> readerCertificateChain;
-    if (readerSignature.size() > 0) {
-        readerCertificateChain = support::coseSignGetX5Chain(readerSignature);
-        if (!readerCertificateChain) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_READER_SIGNATURE_CHECK_FAILED,
-                    "Unable to get reader certificate chain from COSE_Sign1"));
-        }
-
-        if (!support::certificateChainValidate(readerCertificateChain.value())) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_READER_SIGNATURE_CHECK_FAILED,
-                    "Error validating reader certificate chain"));
-        }
-
-        optional<vector<uint8_t>> readerPublicKey =
-                support::certificateChainGetTopMostKey(readerCertificateChain.value());
-        if (!readerPublicKey) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_READER_SIGNATURE_CHECK_FAILED,
-                    "Unable to get public key from reader certificate chain"));
-        }
-
-        const vector<uint8_t>& itemsRequestBytes = itemsRequest;
-        vector<uint8_t> encodedReaderAuthentication =
-                cppbor::Array()
-                        .add("ReaderAuthentication")
-                        .add(std::move(sessionTranscriptItem))
-                        .add(cppbor::Semantic(24, itemsRequestBytes))
-                        .encode();
-        vector<uint8_t> encodedReaderAuthenticationBytes =
-                cppbor::Semantic(24, encodedReaderAuthentication).encode();
-        if (!support::coseCheckEcDsaSignature(readerSignature,
-                                              encodedReaderAuthenticationBytes,  // detached content
-                                              readerPublicKey.value())) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_READER_SIGNATURE_CHECK_FAILED,
-                    "readerSignature check failed"));
-        }
-    }
-
-    // Here's where we would validate the passed-in |authToken| to assure ourselves
-    // that it comes from the e.g. biometric hardware and wasn't made up by an attacker.
-    //
-    // However this involves calculating the MAC. However this requires access
-    // to the key needed to a pre-shared key which we don't have...
-    //
-
-    // To prevent replay-attacks, we check that the public part of the ephemeral
-    // key we previously created, is present in the DeviceEngagement part of
-    // SessionTranscript as a COSE_Key, in uncompressed form.
-    //
-    // We do this by just searching for the X and Y coordinates.
-    if (sessionTranscript.size() > 0) {
-        auto [getXYSuccess, ePubX, ePubY] = support::ecPublicKeyGetXandY(ephemeralPublicKey_);
-        if (!getXYSuccess) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_EPHEMERAL_PUBLIC_KEY_NOT_FOUND,
-                    "Error extracting X and Y from ePub"));
-        }
-        if (sessionTranscript.size() > 0 &&
-            !(memmem(sessionTranscript.data(), sessionTranscript.size(), ePubX.data(),
-                     ePubX.size()) != nullptr &&
-              memmem(sessionTranscript.data(), sessionTranscript.size(), ePubY.data(),
-                     ePubY.size()) != nullptr)) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_EPHEMERAL_PUBLIC_KEY_NOT_FOUND,
-                    "Did not find ephemeral public key's X and Y coordinates in "
-                    "SessionTranscript (make sure leading zeroes are not used)"));
-        }
-    }
-
-    // itemsRequest: If non-empty, contains request data that may be signed by the
-    // reader.  The content can be defined in the way appropriate for the
-    // credential, but there are three requirements that must be met to work with
-    // this HAL:
-    if (itemsRequest.size() > 0) {
-        // 1. The content must be a CBOR-encoded structure.
-        auto [item, _, message] = cppbor::parse(itemsRequest);
-        if (item == nullptr) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_INVALID_ITEMS_REQUEST_MESSAGE,
-                    "Error decoding CBOR in itemsRequest"));
-        }
-
-        // 2. The CBOR structure must be a map.
-        const cppbor::Map* map = item->asMap();
-        if (map == nullptr) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_INVALID_ITEMS_REQUEST_MESSAGE,
-                    "itemsRequest is not a CBOR map"));
-        }
-
-        // 3. The map must contain a key "nameSpaces" whose value contains a map, as described in
-        //    the example below.
-        //
-        //   NameSpaces = {
-        //     + NameSpace => DataElements ; Requested data elements for each NameSpace
-        //   }
-        //
-        //   NameSpace = tstr
-        //
-        //   DataElements = {
-        //     + DataElement => IntentToRetain
-        //   }
-        //
-        //   DataElement = tstr
-        //   IntentToRetain = bool
-        //
-        // Here's an example of an |itemsRequest| CBOR value satisfying above requirements 1.
-        // through 3.:
-        //
-        //    {
-        //        'docType' : 'org.iso.18013-5.2019',
-        //        'nameSpaces' : {
-        //            'org.iso.18013-5.2019' : {
-        //                'Last name' : false,
-        //                'Birth date' : false,
-        //                'First name' : false,
-        //                'Home address' : true
-        //            },
-        //            'org.aamva.iso.18013-5.2019' : {
-        //                'Real Id' : false
-        //            }
-        //        }
-        //    }
-        //
-        const cppbor::Map* nsMap = nullptr;
-        for (size_t n = 0; n < map->size(); n++) {
-            const auto& [keyItem, valueItem] = (*map)[n];
-            if (keyItem->type() == cppbor::TSTR && keyItem->asTstr()->value() == "nameSpaces" &&
-                valueItem->type() == cppbor::MAP) {
-                nsMap = valueItem->asMap();
-                break;
-            }
-        }
-        if (nsMap == nullptr) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_INVALID_ITEMS_REQUEST_MESSAGE,
-                    "No nameSpaces map in top-most map"));
-        }
-
-        for (size_t n = 0; n < nsMap->size(); n++) {
-            auto [nsKeyItem, nsValueItem] = (*nsMap)[n];
-            const cppbor::Tstr* nsKey = nsKeyItem->asTstr();
-            const cppbor::Map* nsInnerMap = nsValueItem->asMap();
-            if (nsKey == nullptr || nsInnerMap == nullptr) {
-                return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                        IIdentityCredentialStore::STATUS_INVALID_ITEMS_REQUEST_MESSAGE,
-                        "Type mismatch in nameSpaces map"));
-            }
-            string requestedNamespace = nsKey->value();
-            set<string> requestedKeys;
-            for (size_t m = 0; m < nsInnerMap->size(); m++) {
-                const auto& [innerMapKeyItem, innerMapValueItem] = (*nsInnerMap)[m];
-                const cppbor::Tstr* nameItem = innerMapKeyItem->asTstr();
-                const cppbor::Simple* simple = innerMapValueItem->asSimple();
-                const cppbor::Bool* intentToRetainItem =
-                        (simple != nullptr) ? simple->asBool() : nullptr;
-                if (nameItem == nullptr || intentToRetainItem == nullptr) {
-                    return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                            IIdentityCredentialStore::STATUS_INVALID_ITEMS_REQUEST_MESSAGE,
-                            "Type mismatch in value in nameSpaces map"));
-                }
-                requestedKeys.insert(nameItem->value());
-            }
-            requestedNameSpacesAndNames_[requestedNamespace] = requestedKeys;
-        }
-    }
-
-    // Validate all the access control profiles in the requestData.
-    bool haveAuthToken = (authToken.timestamp.milliSeconds != int64_t(0));
-    for (const auto& profile : accessControlProfiles) {
-        if (!secureAccessControlProfileCheckMac(profile, storageKey_)) {
-            LOG(ERROR) << "Error checking MAC for profile";
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_INVALID_DATA,
-                    "Error checking MAC for profile"));
-        }
-        int accessControlCheck = IIdentityCredentialStore::STATUS_OK;
-        if (profile.userAuthenticationRequired) {
-            if (!haveAuthToken ||
-                !checkUserAuthentication(profile, verificationToken_, authToken, authChallenge_)) {
-                accessControlCheck = IIdentityCredentialStore::STATUS_USER_AUTHENTICATION_FAILED;
-            }
-        } else if (profile.readerCertificate.encodedCertificate.size() > 0) {
-            if (!readerCertificateChain ||
-                !checkReaderAuthentication(profile, readerCertificateChain.value())) {
-                accessControlCheck = IIdentityCredentialStore::STATUS_READER_AUTHENTICATION_FAILED;
-            }
-        }
-        profileIdToAccessCheckResult_[profile.id] = accessControlCheck;
-    }
-
-    deviceNameSpacesMap_ = cppbor::Map();
-    currentNameSpaceDeviceNameSpacesMap_ = cppbor::Map();
-
-    requestCountsRemaining_ = requestCounts;
-    currentNameSpace_ = "";
-
-    itemsRequest_ = itemsRequest;
-    signingKeyBlob_ = signingKeyBlob;
-
-    // Finally, calculate the size of DeviceNameSpaces. We need to know it ahead of time.
-    expectedDeviceNameSpacesSize_ = calcDeviceNameSpacesSize();
-
-    numStartRetrievalCalls_ += 1;
-    return ndk::ScopedAStatus::ok();
-}
-
-size_t cborNumBytesForLength(size_t length) {
-    if (length < 24) {
-        return 0;
-    } else if (length <= 0xff) {
-        return 1;
-    } else if (length <= 0xffff) {
-        return 2;
-    } else if (length <= 0xffffffff) {
-        return 4;
-    }
-    return 8;
-}
-
-size_t cborNumBytesForTstr(const string& value) {
-    return 1 + cborNumBytesForLength(value.size()) + value.size();
-}
-
-size_t IdentityCredential::calcDeviceNameSpacesSize() {
-    /*
-     * This is how DeviceNameSpaces is defined:
-     *
-     *        DeviceNameSpaces = {
-     *            * NameSpace => DeviceSignedItems
-     *        }
-     *        DeviceSignedItems = {
-     *            + DataItemName => DataItemValue
-     *        }
-     *
-     *        Namespace = tstr
-     *        DataItemName = tstr
-     *        DataItemValue = any
-     *
-     * This function will calculate its length using knowledge of how CBOR is
-     * encoded.
-     */
-    size_t ret = 0;
-    size_t numNamespacesWithValues = 0;
-    for (const RequestNamespace& rns : requestNamespaces_) {
-        vector<RequestDataItem> itemsToInclude;
-
-        for (const RequestDataItem& rdi : rns.items) {
-            // If we have a CBOR request message, skip if item isn't in it
-            if (itemsRequest_.size() > 0) {
-                const auto& it = requestedNameSpacesAndNames_.find(rns.namespaceName);
-                if (it == requestedNameSpacesAndNames_.end()) {
-                    continue;
-                }
-                const set<string>& dataItemNames = it->second;
-                if (dataItemNames.find(rdi.name) == dataItemNames.end()) {
-                    continue;
-                }
-            }
-
-            // Access is granted if at least one of the profiles grants access.
-            //
-            // If an item is configured without any profiles, access is denied.
-            //
-            bool authorized = false;
-            for (auto id : rdi.accessControlProfileIds) {
-                auto it = profileIdToAccessCheckResult_.find(id);
-                if (it != profileIdToAccessCheckResult_.end()) {
-                    int accessControlForProfile = it->second;
-                    if (accessControlForProfile == IIdentityCredentialStore::STATUS_OK) {
-                        authorized = true;
-                        break;
-                    }
-                }
-            }
-            if (!authorized) {
-                continue;
-            }
-
-            itemsToInclude.push_back(rdi);
-        }
-
-        // If no entries are to be in the namespace, we don't include it...
-        if (itemsToInclude.size() == 0) {
-            continue;
-        }
-
-        // Key: NameSpace
-        ret += cborNumBytesForTstr(rns.namespaceName);
-
-        // Value: Open the DeviceSignedItems map
-        ret += 1 + cborNumBytesForLength(itemsToInclude.size());
-
-        for (const RequestDataItem& item : itemsToInclude) {
-            // Key: DataItemName
-            ret += cborNumBytesForTstr(item.name);
-
-            // Value: DataItemValue - entryData.size is the length of serialized CBOR so we use
-            // that.
-            ret += item.size;
-        }
-
-        numNamespacesWithValues++;
-    }
-
-    // Now that we now the nunber of namespaces with values, we know how many
-    // bytes the DeviceNamespaces map in the beginning is going to take up.
-    ret += 1 + cborNumBytesForLength(numNamespacesWithValues);
-
-    return ret;
-}
-
-ndk::ScopedAStatus IdentityCredential::startRetrieveEntryValue(
-        const string& nameSpace, const string& name, int32_t entrySize,
-        const vector<int32_t>& accessControlProfileIds) {
-    if (name.empty()) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_INVALID_DATA, "Name cannot be empty"));
-    }
-    if (nameSpace.empty()) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_INVALID_DATA, "Name space cannot be empty"));
-    }
-
-    if (requestCountsRemaining_.size() == 0) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_INVALID_DATA,
-                "No more name spaces left to go through"));
-    }
-
-    if (currentNameSpace_ == "") {
-        // First call.
-        currentNameSpace_ = nameSpace;
-    }
-
-    if (nameSpace == currentNameSpace_) {
-        // Same namespace.
-        if (requestCountsRemaining_[0] == 0) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_INVALID_DATA,
-                    "No more entries to be retrieved in current name space"));
-        }
-        requestCountsRemaining_[0] -= 1;
-    } else {
-        // New namespace.
-        if (requestCountsRemaining_[0] != 0) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_INVALID_DATA,
-                    "Moved to new name space but one or more entries need to be retrieved "
-                    "in current name space"));
-        }
-        if (currentNameSpaceDeviceNameSpacesMap_.size() > 0) {
-            deviceNameSpacesMap_.add(currentNameSpace_,
-                                     std::move(currentNameSpaceDeviceNameSpacesMap_));
-        }
-        currentNameSpaceDeviceNameSpacesMap_ = cppbor::Map();
-
-        requestCountsRemaining_.erase(requestCountsRemaining_.begin());
-        currentNameSpace_ = nameSpace;
-    }
-
-    // It's permissible to have an empty itemsRequest... but if non-empty you can
-    // only request what was specified in said itemsRequest. Enforce that.
-    if (itemsRequest_.size() > 0) {
-        const auto& it = requestedNameSpacesAndNames_.find(nameSpace);
-        if (it == requestedNameSpacesAndNames_.end()) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_NOT_IN_REQUEST_MESSAGE,
-                    "Name space was not requested in startRetrieval"));
-        }
-        const set<string>& dataItemNames = it->second;
-        if (dataItemNames.find(name) == dataItemNames.end()) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_NOT_IN_REQUEST_MESSAGE,
-                    "Data item name in name space was not requested in startRetrieval"));
-        }
-    }
-
-    // Enforce access control.
-    //
-    // Access is granted if at least one of the profiles grants access.
-    //
-    // If an item is configured without any profiles, access is denied.
-    //
-    int accessControl = IIdentityCredentialStore::STATUS_NO_ACCESS_CONTROL_PROFILES;
-    for (auto id : accessControlProfileIds) {
-        auto search = profileIdToAccessCheckResult_.find(id);
-        if (search == profileIdToAccessCheckResult_.end()) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_INVALID_DATA,
-                    "Requested entry with unvalidated profile id"));
-        }
-        int accessControlForProfile = search->second;
-        if (accessControlForProfile == IIdentityCredentialStore::STATUS_OK) {
-            accessControl = IIdentityCredentialStore::STATUS_OK;
-            break;
-        }
-        accessControl = accessControlForProfile;
-    }
-    if (accessControl != IIdentityCredentialStore::STATUS_OK) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                int(accessControl), "Access control check failed"));
-    }
-
-    entryAdditionalData_ = entryCreateAdditionalData(nameSpace, name, accessControlProfileIds);
-
-    currentName_ = name;
-    entryRemainingBytes_ = entrySize;
-    entryValue_.resize(0);
-
-    return ndk::ScopedAStatus::ok();
-}
-
-ndk::ScopedAStatus IdentityCredential::retrieveEntryValue(const vector<uint8_t>& encryptedContent,
-                                                          vector<uint8_t>* outContent) {
-    optional<vector<uint8_t>> content =
-            support::decryptAes128Gcm(storageKey_, encryptedContent, entryAdditionalData_);
-    if (!content) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_INVALID_DATA, "Error decrypting data"));
-    }
-
-    size_t chunkSize = content.value().size();
-
-    if (chunkSize > entryRemainingBytes_) {
-        LOG(ERROR) << "Retrieved chunk of size " << chunkSize
-                   << " is bigger than remaining space of size " << entryRemainingBytes_;
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_INVALID_DATA,
-                "Retrieved chunk is bigger than remaining space"));
-    }
-
-    entryRemainingBytes_ -= chunkSize;
-    if (entryRemainingBytes_ > 0) {
-        if (chunkSize != IdentityCredentialStore::kGcmChunkSize) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_INVALID_DATA,
-                    "Retrieved non-final chunk of size which isn't kGcmChunkSize"));
-        }
-    }
-
-    entryValue_.insert(entryValue_.end(), content.value().begin(), content.value().end());
-
-    if (entryRemainingBytes_ == 0) {
-        auto [entryValueItem, _, message] = cppbor::parse(entryValue_);
-        if (entryValueItem == nullptr) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_INVALID_DATA,
-                    "Retrieved data which is invalid CBOR"));
-        }
-        currentNameSpaceDeviceNameSpacesMap_.add(currentName_, std::move(entryValueItem));
-    }
-
-    *outContent = content.value();
-    return ndk::ScopedAStatus::ok();
-}
-
-ndk::ScopedAStatus IdentityCredential::finishRetrieval(vector<uint8_t>* outMac,
-                                                       vector<uint8_t>* outDeviceNameSpaces) {
-    if (currentNameSpaceDeviceNameSpacesMap_.size() > 0) {
-        deviceNameSpacesMap_.add(currentNameSpace_,
-                                 std::move(currentNameSpaceDeviceNameSpacesMap_));
-    }
-    vector<uint8_t> encodedDeviceNameSpaces = deviceNameSpacesMap_.encode();
-
-    if (encodedDeviceNameSpaces.size() != expectedDeviceNameSpacesSize_) {
-        LOG(ERROR) << "encodedDeviceNameSpaces is " << encodedDeviceNameSpaces.size() << " bytes, "
-                   << "was expecting " << expectedDeviceNameSpacesSize_;
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_INVALID_DATA,
-                StringPrintf(
-                        "Unexpected CBOR size %zd for encodedDeviceNameSpaces, was expecting %zd",
-                        encodedDeviceNameSpaces.size(), expectedDeviceNameSpacesSize_)
-                        .c_str()));
-    }
-
-    // If there's no signing key or no sessionTranscript or no reader ephemeral
-    // public key, we return the empty MAC.
-    optional<vector<uint8_t>> mac;
-    if (signingKeyBlob_.size() > 0 && sessionTranscript_.size() > 0 &&
-        readerPublicKey_.size() > 0) {
-        vector<uint8_t> docTypeAsBlob(docType_.begin(), docType_.end());
-        optional<vector<uint8_t>> signingKey =
-                support::decryptAes128Gcm(storageKey_, signingKeyBlob_, docTypeAsBlob);
-        if (!signingKey) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_INVALID_DATA,
-                    "Error decrypting signingKeyBlob"));
-        }
-
-        vector<uint8_t> sessionTranscriptBytes = cppbor::Semantic(24, sessionTranscript_).encode();
-        optional<vector<uint8_t>> eMacKey =
-                support::calcEMacKey(signingKey.value(), readerPublicKey_, sessionTranscriptBytes);
-        if (!eMacKey) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_FAILED, "Error calculating EMacKey"));
-        }
-        mac = support::calcMac(sessionTranscript_, docType_, encodedDeviceNameSpaces,
-                               eMacKey.value());
-        if (!mac) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_FAILED, "Error MACing data"));
-        }
-    }
-
-    *outMac = mac.value_or(vector<uint8_t>({}));
-    *outDeviceNameSpaces = encodedDeviceNameSpaces;
-    return ndk::ScopedAStatus::ok();
-}
-
-ndk::ScopedAStatus IdentityCredential::generateSigningKeyPair(
-        vector<uint8_t>* outSigningKeyBlob, Certificate* outSigningKeyCertificate) {
-    string serialDecimal = "1";
-    string issuer = "Android Identity Credential Key";
-    string subject = "Android Identity Credential Authentication Key";
-    time_t validityNotBefore = time(nullptr);
-    time_t validityNotAfter = validityNotBefore + 365 * 24 * 3600;
-
-    optional<vector<uint8_t>> signingKeyPKCS8 = support::createEcKeyPair();
-    if (!signingKeyPKCS8) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_FAILED, "Error creating signingKey"));
-    }
-
-    optional<vector<uint8_t>> signingPublicKey =
-            support::ecKeyPairGetPublicKey(signingKeyPKCS8.value());
-    if (!signingPublicKey) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_FAILED,
-                "Error getting public part of signingKey"));
-    }
-
-    optional<vector<uint8_t>> signingKey = support::ecKeyPairGetPrivateKey(signingKeyPKCS8.value());
-    if (!signingKey) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_FAILED,
-                "Error getting private part of signingKey"));
-    }
-
-    optional<vector<uint8_t>> certificate = support::ecPublicKeyGenerateCertificate(
-            signingPublicKey.value(), credentialPrivKey_, serialDecimal, issuer, subject,
-            validityNotBefore, validityNotAfter);
-    if (!certificate) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_FAILED, "Error creating signingKey"));
-    }
-
-    optional<vector<uint8_t>> nonce = support::getRandom(12);
-    if (!nonce) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_FAILED, "Error getting random"));
-    }
-    vector<uint8_t> docTypeAsBlob(docType_.begin(), docType_.end());
-    optional<vector<uint8_t>> encryptedSigningKey = support::encryptAes128Gcm(
-            storageKey_, nonce.value(), signingKey.value(), docTypeAsBlob);
-    if (!encryptedSigningKey) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_FAILED, "Error encrypting signingKey"));
-    }
-    *outSigningKeyBlob = encryptedSigningKey.value();
-    *outSigningKeyCertificate = Certificate();
-    outSigningKeyCertificate->encodedCertificate = certificate.value();
-    return ndk::ScopedAStatus::ok();
-}
-
-}  // namespace aidl::android::hardware::identity