Merge "Add attestation certificate generation and identity credential tags." am: 93bba950ed (545148b7) · Commits · e / os / android_hardware_interfaces

identity/aidl/default/WritableIdentityCredential.cpp

+35 −84

Original line number	Diff line number	Diff line
		@@ -16,6 +16,9 @@

		#define LOG_TAG "WritableIdentityCredential"

		#include "WritableIdentityCredential.h"
		#include "IdentityCredentialStore.h"

		#include <android/hardware/identity/support/IdentityCredentialSupport.h>

		#include <android-base/logging.h>
		@@ -23,6 +26,8 @@
		#include <cppbor/cppbor.h>
		#include <cppbor/cppbor_parse.h>

		#include <utility>

		#include "IdentityCredentialStore.h"
		#include "Util.h"
		#include "WritableIdentityCredential.h"
		@@ -33,26 +38,6 @@ using ::std::optional;
		using namespace ::android::hardware::identity;

		bool WritableIdentityCredential::initialize() {
		optional<vector<uint8_t>> keyPair = support::createEcKeyPair();
		if (!keyPair) {
		LOG(ERROR) << "Error creating credentialKey";
		return false;
		}

		optional<vector<uint8_t>> pubKey = support::ecKeyPairGetPublicKey(keyPair.value());
		if (!pubKey) {
		LOG(ERROR) << "Error getting public part of credentialKey";
		return false;
		}
		credentialPubKey_ = pubKey.value();

		optional<vector<uint8_t>> privKey = support::ecKeyPairGetPrivateKey(keyPair.value());
		if (!privKey) {
		LOG(ERROR) << "Error getting private part of credentialKey";
		return false;
		}
		credentialPrivKey_ = privKey.value();

		optional<vector<uint8_t>> random = support::getRandom(16);
		if (!random) {
		LOG(ERROR) << "Error creating storageKey";
		@@ -63,88 +48,54 @@ bool WritableIdentityCredential::initialize() {
		return true;
		}

		// TODO: use \|attestationApplicationId\| and \|attestationChallenge\| and also
		// ensure the returned certificate chain satisfy the requirements listed in
		// the docs for IWritableIdentityCredential::getAttestationCertificate()
		//
		// This function generates the attestation certificate using the passed in
		// \|attestationApplicationId\| and \|attestationChallenge\|. It will generate an
		// attestation certificate with current time and expires one year from now. The
		// certificate shall contain all values as specified in hal.
		ndk::ScopedAStatus WritableIdentityCredential::getAttestationCertificate(
		const vector<int8_t>& /attestationApplicationId/,
		const vector<int8_t>& /attestationChallenge/, vector<Certificate>* outCertificateChain) {
		// For now, we dynamically generate an attestion key on each and every
		// request and use that to sign CredentialKey. In a real implementation this
		// would look very differently.
		optional<vector<uint8_t>> attestationKeyPair = support::createEcKeyPair();
		if (!attestationKeyPair) {
		const vector<int8_t>& attestationApplicationId, //
		const vector<int8_t>& attestationChallenge, //
		vector<Certificate>* outCertificateChain) {
		if (!credentialPrivKey_.empty() \|\| !credentialPubKey_.empty() \|\| !certificateChain_.empty()) {
		return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
		IIdentityCredentialStore::STATUS_FAILED, "Error creating attestationKey"));
		IIdentityCredentialStore::STATUS_FAILED,
		"Error attestation certificate previously generated"));
		}

		optional<vector<uint8_t>> attestationPubKey =
		support::ecKeyPairGetPublicKey(attestationKeyPair.value());
		if (!attestationPubKey) {
		vector<uint8_t> challenge(attestationChallenge.begin(), attestationChallenge.end());
		vector<uint8_t> appId(attestationApplicationId.begin(), attestationApplicationId.end());

		optional<std::pair<vector<uint8_t>, vector<vector<uint8_t>>>> keyAttestationPair =
		support::createEcKeyPairAndAttestation(challenge, appId);
		if (!keyAttestationPair) {
		LOG(ERROR) << "Error creating credentialKey and attestation";
		return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
		IIdentityCredentialStore::STATUS_FAILED,
		"Error getting public part of attestationKey"));
		"Error creating credentialKey and attestation"));
		}

		optional<vector<uint8_t>> attestationPrivKey =
		support::ecKeyPairGetPrivateKey(attestationKeyPair.value());
		if (!attestationPrivKey) {
		return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
		IIdentityCredentialStore::STATUS_FAILED,
		"Error getting private part of attestationKey"));
		}

		string serialDecimal;
		string issuer;
		string subject;
		time_t validityNotBefore = time(nullptr);
		time_t validityNotAfter = validityNotBefore + 365 * 24 * 3600;

		// First create a certificate for \|credentialPubKey\| which is signed by
		// \|attestationPrivKey\|.
		//
		serialDecimal = "0"; // TODO: set serial to \|attestationChallenge\|
		issuer = "Android Open Source Project";
		subject = "Android IdentityCredential CredentialKey";
		optional<vector<uint8_t>> credentialPubKeyCertificate = support::ecPublicKeyGenerateCertificate(
		credentialPubKey_, attestationPrivKey.value(), serialDecimal, issuer, subject,
		validityNotBefore, validityNotAfter);
		if (!credentialPubKeyCertificate) {
		return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
		IIdentityCredentialStore::STATUS_FAILED,
		"Error creating certificate for credentialPubKey"));
		}

		// This is followed by a certificate for \|attestationPubKey\| self-signed by
		// \|attestationPrivKey\|.
		serialDecimal = "0"; // TODO: set serial
		issuer = "Android Open Source Project";
		subject = "Android IdentityCredential AttestationKey";
		optional<vector<uint8_t>> attestationKeyCertificate = support::ecPublicKeyGenerateCertificate(
		attestationPubKey.value(), attestationPrivKey.value(), serialDecimal, issuer, subject,
		validityNotBefore, validityNotAfter);
		if (!attestationKeyCertificate) {
		vector<uint8_t> keyPair = keyAttestationPair.value().first;
		certificateChain_ = keyAttestationPair.value().second;

		optional<vector<uint8_t>> pubKey = support::ecKeyPairGetPublicKey(keyPair);
		if (!pubKey) {
		return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
		IIdentityCredentialStore::STATUS_FAILED,
		"Error creating certificate for attestationPubKey"));
		"Error getting public part of credentialKey"));
		}
		credentialPubKey_ = pubKey.value();

		// Concatenate the certificates to form the chain.
		vector<uint8_t> certificateChain;
		certificateChain.insert(certificateChain.end(), credentialPubKeyCertificate.value().begin(),
		credentialPubKeyCertificate.value().end());
		certificateChain.insert(certificateChain.end(), attestationKeyCertificate.value().begin(),
		attestationKeyCertificate.value().end());

		optional<vector<vector<uint8_t>>> splitCertChain =
		support::certificateChainSplit(certificateChain);
		if (!splitCertChain) {
		optional<vector<uint8_t>> privKey = support::ecKeyPairGetPrivateKey(keyPair);
		if (!privKey) {
		return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
		IIdentityCredentialStore::STATUS_FAILED, "Error splitting certificate chain"));
		IIdentityCredentialStore::STATUS_FAILED,
		"Error getting private part of credentialKey"));
		}
		credentialPrivKey_ = privKey.value();

		// convert from vector<vector<uint8_t>>> to vector<Certificate>*
		*outCertificateChain = vector<Certificate>();
		for (const vector<uint8_t>& cert : splitCertChain.value()) {
		for (const vector<uint8_t>& cert : certificateChain_) {
		Certificate c = Certificate();
		c.encodedCertificate = byteStringToSigned(cert);
		outCertificateChain->push_back(std::move(c));

identity/aidl/default/WritableIdentityCredential.h

+4 −1

Original line number	Diff line number	Diff line
		@@ -64,10 +64,13 @@ class WritableIdentityCredential : public BnWritableIdentityCredential {
		string docType_;
		bool testCredential_;

		// These are set in initialize().
		// This is set in initialize().
		vector<uint8_t> storageKey_;

		// These are set in getAttestationCertificate().
		vector<uint8_t> credentialPrivKey_;
		vector<uint8_t> credentialPubKey_;
		vector<vector<uint8_t>> certificateChain_;

		// These fields are initialized during startPersonalization()
		size_t numAccessControlProfileRemaining_;

identity/support/Android.bp

+4 −0

Original line number	Diff line number	Diff line
		@@ -23,10 +23,14 @@ cc_library {
		"include",
		],
		shared_libs: [
		"android.hardware.keymaster@4.0",
		"libcrypto",
		"libbase",
		"libhidlbase",
		"libhardware",
		"libkeymaster_portable",
		"libsoft_attestation_cert",
		"libpuresoftkeymasterdevice",
		],
		static_libs: [
		"libcppbor",

identity/support/include/android/hardware/identity/support/IdentityCredentialSupport.h

+12 −0

Original line number	Diff line number	Diff line
		@@ -21,6 +21,7 @@
		#include <optional>
		#include <string>
		#include <tuple>
		#include <utility>
		#include <vector>

		namespace android {
		@@ -106,6 +107,17 @@ optional<vector<uint8_t>> encryptAes128Gcm(const vector<uint8_t>& key, const vec
		// ---------------------------------------------------------------------------
		// EC crypto functionality / abstraction (only supports P-256).
		// ---------------------------------------------------------------------------
		// Creates an 256-bit EC key using the NID_X9_62_prime256v1 curve, returns the
		// PKCS#8 encoded key-pair. Also generates an attestation
		// certificate using the \|challenge\| and \|applicationId\|, and returns the generated
		// certificate in X.509 certificate chain format.
		//
		// The attestation time fields used will be the current time, and expires in one year.
		//
		// The first parameter of the return value is the keyPair generated, second return in
		// the pair is the attestation certificate generated.
		optional<std::pair<vector<uint8_t>, vector<vector<uint8_t>>>> createEcKeyPairAndAttestation(
		const vector<uint8_t>& challenge, const vector<uint8_t>& applicationId);

		// Creates an 256-bit EC key using the NID_X9_62_prime256v1 curve, returns the
		// PKCS#8 encoded key-pair.

identity/support/src/IdentityCredentialSupport.cpp

+139 −0

Original line number	Diff line number	Diff line
		@@ -47,6 +47,13 @@
		#include <cppbor.h>
		#include <cppbor_parse.h>

		#include <android/hardware/keymaster/4.0/types.h>
		#include <keymaster/authorization_set.h>
		#include <keymaster/contexts/pure_soft_keymaster_context.h>
		#include <keymaster/contexts/soft_attestation_cert.h>
		#include <keymaster/keymaster_tags.h>
		#include <keymaster/km_openssl/attestation_utils.h>

		namespace android {
		namespace hardware {
		namespace identity {
		@@ -816,6 +823,138 @@ optional<vector<uint8_t>> hmacSha256(const vector<uint8_t>& key, const vector<ui
		return hmac;
		}

		// Generates the attestation certificate with the parameters passed in. Note
		// that the passed in \|activeTimeMilliSeconds\| \|expireTimeMilliSeconds\| are in
		// milli seconds since epoch. We are setting them to milliseconds due to
		// requirement in AuthorizationSet KM_DATE fields. The certificate created is
		// actually in seconds.
		optional<vector<vector<uint8_t>>> createAttestation(const EVP_PKEY* key,
		const vector<uint8_t>& applicationId,
		const vector<uint8_t>& challenge,
		uint64_t activeTimeMilliSeconds,
		uint64_t expireTimeMilliSeconds) {
		::keymaster::AuthorizationSet auth_set(
		::keymaster::AuthorizationSetBuilder()
		.Authorization(::keymaster::TAG_ATTESTATION_CHALLENGE, challenge.data(),
		challenge.size())
		.Authorization(::keymaster::TAG_ACTIVE_DATETIME, activeTimeMilliSeconds)
		// Even though identity attestation hal said the application
		// id should be in software enforced authentication set,
		// keymaster portable lib expect the input in this
		// parameter because the software enforced in input to keymaster
		// refers to the key software enforced properties. And this
		// parameter refers to properties of the attestation which
		// includes app id.
		.Authorization(::keymaster::TAG_ATTESTATION_APPLICATION_ID,
		applicationId.data(), applicationId.size())
		.Authorization(::keymaster::TAG_USAGE_EXPIRE_DATETIME, expireTimeMilliSeconds));

		// Unique id and device id is not applicable for identity credential attestation,
		// so we don't need to set those or application id.
		::keymaster::AuthorizationSet swEnforced(::keymaster::AuthorizationSetBuilder().Authorization(
		::keymaster::TAG_CREATION_DATETIME, activeTimeMilliSeconds));

		::keymaster::AuthorizationSet hwEnforced(
		::keymaster::AuthorizationSetBuilder()
		.Authorization(::keymaster::TAG_PURPOSE, KM_PURPOSE_SIGN)
		.Authorization(::keymaster::TAG_KEY_SIZE, 256)
		.Authorization(::keymaster::TAG_ALGORITHM, KM_ALGORITHM_EC)
		.Authorization(::keymaster::TAG_NO_AUTH_REQUIRED)
		.Authorization(::keymaster::TAG_DIGEST, KM_DIGEST_SHA_2_256)
		.Authorization(::keymaster::TAG_EC_CURVE, KM_EC_CURVE_P_256)
		.Authorization(::keymaster::TAG_IDENTITY_CREDENTIAL_KEY));

		const keymaster_cert_chain_t* attestation_chain =
		::keymaster::getAttestationChain(KM_ALGORITHM_EC, nullptr);

		if (attestation_chain == nullptr) {
		LOG(ERROR) << "Error getting attestation chain";
		return {};
		}

		const keymaster_key_blob_t* attestation_signing_key =
		::keymaster::getAttestationKey(KM_ALGORITHM_EC, nullptr);
		if (attestation_signing_key == nullptr) {
		LOG(ERROR) << "Error getting attestation key";
		return {};
		}

		keymaster_error_t error;
		::keymaster::CertChainPtr cert_chain_out;
		::keymaster::PureSoftKeymasterContext context;

		// set identity version to 10 per hal requirements specified in IWriteableCredential.hal
		// For now, the identity version in the attestation is set in the keymaster
		// version field in the portable keymaster lib, which is a bit misleading.
		uint identity_version = 10;
		error = generate_attestation_from_EVP(key, swEnforced, hwEnforced, auth_set, context,
		identity_version, *attestation_chain,
		*attestation_signing_key, &cert_chain_out);

		if (KM_ERROR_OK != error \|\| !cert_chain_out) {
		LOG(ERROR) << "Error generate attestation from EVP key" << error;
		return {};
		}

		// translate certificate format from keymaster_cert_chain_t to vector<uint8_t>.
		vector<vector<uint8_t>> attestationCertificate;
		for (int i = 0; i < cert_chain_out->entry_count; i++) {
		attestationCertificate.insert(
		attestationCertificate.end(),
		vector<uint8_t>(
		cert_chain_out->entries[i].data,
		cert_chain_out->entries[i].data + cert_chain_out->entries[i].data_length));
		}

		return attestationCertificate;
		}

		optional<std::pair<vector<uint8_t>, vector<vector<uint8_t>>>> createEcKeyPairAndAttestation(
		const vector<uint8_t>& challenge, const vector<uint8_t>& applicationId) {
		auto ec_key = ::keymaster::EC_KEY_Ptr(EC_KEY_new());
		auto pkey = ::keymaster::EVP_PKEY_Ptr(EVP_PKEY_new());
		auto group = ::keymaster::EC_GROUP_Ptr(EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1));

		if (ec_key.get() == nullptr \|\| pkey.get() == nullptr) {
		LOG(ERROR) << "Memory allocation failed";
		return {};
		}

		if (EC_KEY_set_group(ec_key.get(), group.get()) != 1 \|\|
		EC_KEY_generate_key(ec_key.get()) != 1 \|\| EC_KEY_check_key(ec_key.get()) < 0) {
		LOG(ERROR) << "Error generating key";
		return {};
		}

		if (EVP_PKEY_set1_EC_KEY(pkey.get(), ec_key.get()) != 1) {
		LOG(ERROR) << "Error getting private key";
		return {};
		}

		uint64_t now = time(nullptr);
		uint64_t secondsInOneYear = 365 * 24 * 60 * 60;
		uint64_t expireTimeMs = (now + secondsInOneYear) * 1000;

		optional<vector<vector<uint8_t>>> attestationCert =
		createAttestation(pkey.get(), applicationId, challenge, now * 1000, expireTimeMs);
		if (!attestationCert) {
		LOG(ERROR) << "Error create attestation from key and challenge";
		return {};
		}

		int size = i2d_PrivateKey(pkey.get(), nullptr);
		if (size == 0) {
		LOG(ERROR) << "Error generating public key encoding";
		return {};
		}

		vector<uint8_t> keyPair(size);
		unsigned char* p = keyPair.data();
		i2d_PrivateKey(pkey.get(), &p);

		return make_pair(keyPair, attestationCert.value());
		}

		optional<vector<uint8_t>> createEcKeyPair() {
		auto ec_key = EC_KEY_Ptr(EC_KEY_new());
		auto pkey = EVP_PKEY_Ptr(EVP_PKEY_new());