path: root/src/java/com/android/internal/net/eap/statemachine/EapAkaMethodStateMachine.java

/*
 * Copyright (C) 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.
 */

package com.android.internal.net.eap.statemachine;

import static com.android.internal.net.eap.EapAuthenticator.LOG;
import static com.android.internal.net.eap.message.EapData.EAP_NOTIFICATION;
import static com.android.internal.net.eap.message.EapData.EAP_TYPE_AKA;
import static com.android.internal.net.eap.message.EapMessage.EAP_CODE_FAILURE;
import static com.android.internal.net.eap.message.EapMessage.EAP_CODE_SUCCESS;
import static com.android.internal.net.eap.message.simaka.EapAkaTypeData.EAP_AKA_AUTHENTICATION_REJECT;
import static com.android.internal.net.eap.message.simaka.EapAkaTypeData.EAP_AKA_CHALLENGE;
import static com.android.internal.net.eap.message.simaka.EapAkaTypeData.EAP_AKA_CLIENT_ERROR;
import static com.android.internal.net.eap.message.simaka.EapAkaTypeData.EAP_AKA_IDENTITY;
import static com.android.internal.net.eap.message.simaka.EapAkaTypeData.EAP_AKA_NOTIFICATION;
import static com.android.internal.net.eap.message.simaka.EapAkaTypeData.EAP_AKA_SYNCHRONIZATION_FAILURE;
import static com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.EAP_AT_ANY_ID_REQ;
import static com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.EAP_AT_AUTN;
import static com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.EAP_AT_BIDDING;
import static com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.EAP_AT_ENCR_DATA;
import static com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.EAP_AT_FULLAUTH_ID_REQ;
import static com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.EAP_AT_IV;
import static com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.EAP_AT_MAC;
import static com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.EAP_AT_PERMANENT_ID_REQ;
import static com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.EAP_AT_RAND;

import android.annotation.Nullable;
import android.content.Context;
import android.net.eap.EapSessionConfig.EapAkaConfig;
import android.telephony.TelephonyManager;

import com.android.internal.annotations.VisibleForTesting;
import com.android.internal.net.eap.EapResult;
import com.android.internal.net.eap.EapResult.EapError;
import com.android.internal.net.eap.EapResult.EapFailure;
import com.android.internal.net.eap.EapResult.EapSuccess;
import com.android.internal.net.eap.crypto.Fips186_2Prf;
import com.android.internal.net.eap.exceptions.EapInvalidRequestException;
import com.android.internal.net.eap.exceptions.EapSilentException;
import com.android.internal.net.eap.exceptions.simaka.EapAkaInvalidAuthenticationResponse;
import com.android.internal.net.eap.exceptions.simaka.EapSimAkaAuthenticationFailureException;
import com.android.internal.net.eap.exceptions.simaka.EapSimAkaIdentityUnavailableException;
import com.android.internal.net.eap.exceptions.simaka.EapSimAkaInvalidAttributeException;
import com.android.internal.net.eap.exceptions.simaka.EapSimAkaInvalidLengthException;
import com.android.internal.net.eap.message.EapData.EapMethod;
import com.android.internal.net.eap.message.EapMessage;
import com.android.internal.net.eap.message.simaka.EapAkaTypeData;
import com.android.internal.net.eap.message.simaka.EapAkaTypeData.EapAkaTypeDataDecoder;
import com.android.internal.net.eap.message.simaka.EapSimAkaAttribute;
import com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.AtAutn;
import com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.AtAuts;
import com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.AtBidding;
import com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.AtClientErrorCode;
import com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.AtIdentity;
import com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.AtRandAka;
import com.android.internal.net.eap.message.simaka.EapSimAkaAttribute.AtRes;
import com.android.internal.net.eap.message.simaka.EapSimAkaTypeData.DecodeResult;

import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Set;

/**
 * EapAkaMethodStateMachine represents the valid paths possible for the EAP-AKA protocol.
 *
 * <p>EAP-AKA sessions will always follow the path:
 *
 * Created --+--> Identity --+--> Challenge --> Final
 *           |               |
 *           +---------------+
 *
 * Note: If the EAP-Request/AKA-Challenge message contains an AUTN with an invalid sequence number,
 * the peer will indicate a synchronization failure to the server and a new challenge will be
 * attempted.
 *
 * Note: EAP-Request/Notification messages can be received at any point in the above state machine
 * At most one EAP-AKA/Notification message is allowed per EAP-AKA session.
 *
 * @see <a href="https://tools.ietf.org/html/rfc4187">RFC 4187, Extensible Authentication
 * Protocol for Authentication and Key Agreement (EAP-AKA)</a>
 */
class EapAkaMethodStateMachine extends EapSimAkaMethodStateMachine {
    private static final String TAG = EapAkaMethodStateMachine.class.getSimpleName();

    // EAP-AKA identity prefix (RFC 4187#4.1.1.6)
    private static final String AKA_IDENTITY_PREFIX = "0";

    private final EapAkaTypeDataDecoder mEapAkaTypeDataDecoder;
    private final boolean mSupportsEapAkaPrime;

    protected EapAkaMethodStateMachine(
            Context context, byte[] eapIdentity, EapAkaConfig eapAkaConfig) {
        this(context, eapIdentity, eapAkaConfig, false);
    }

    EapAkaMethodStateMachine(
            Context context,
            byte[] eapIdentity,
            EapAkaConfig eapAkaConfig,
            boolean supportsEapAkaPrime) {
        this(
                (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE),
                eapIdentity,
                eapAkaConfig,
                EapAkaTypeData.getEapAkaTypeDataDecoder(),
                supportsEapAkaPrime);
    }

    @VisibleForTesting
    protected EapAkaMethodStateMachine(
            TelephonyManager telephonyManager,
            byte[] eapIdentity,
            EapAkaConfig eapAkaConfig,
            EapAkaTypeDataDecoder eapAkaTypeDataDecoder,
            boolean supportsEapAkaPrime) {
        super(
                telephonyManager.createForSubscriptionId(eapAkaConfig.subId),
                eapIdentity,
                eapAkaConfig);
        mEapAkaTypeDataDecoder = eapAkaTypeDataDecoder;
        mSupportsEapAkaPrime = supportsEapAkaPrime;

        transitionTo(new CreatedState());
    }

    @Override
    @EapMethod
    int getEapMethod() {
        return EAP_TYPE_AKA;
    }

    protected DecodeResult<EapAkaTypeData> decode(byte[] typeData) {
        return mEapAkaTypeDataDecoder.decode(typeData);
    }

    /**
     * This exists so we can override the identity prefix in the EapAkaPrimeMethodStateMachine.
     *
     * @return the Identity prefix for this EAP method
     */
    protected String getIdentityPrefix() {
        return AKA_IDENTITY_PREFIX;
    }

    protected ChallengeState buildChallengeState() {
        return new ChallengeState();
    }

    protected ChallengeState buildChallengeState(byte[] identity) {
        return new ChallengeState(identity);
    }

    protected class CreatedState extends EapMethodState {
        private final String mTAG = CreatedState.class.getSimpleName();

        public EapResult process(EapMessage message) {
            EapResult result = handleEapSuccessFailureNotification(mTAG, message);
            if (result != null) {
                return result;
            }

            DecodeResult<? extends EapAkaTypeData> decodeResult =
                    decode(message.eapData.eapTypeData);
            if (!decodeResult.isSuccessfulDecode()) {
                return buildClientErrorResponse(
                        message.eapIdentifier, getEapMethod(), decodeResult.atClientErrorCode);
            }

            EapAkaTypeData eapAkaTypeData = decodeResult.eapTypeData;
            switch (eapAkaTypeData.eapSubtype) {
                case EAP_AKA_IDENTITY:
                    return transitionAndProcess(new IdentityState(), message);
                case EAP_AKA_CHALLENGE:
                    return transitionAndProcess(buildChallengeState(), message);
                case EAP_AKA_NOTIFICATION:
                    return handleEapSimAkaNotification(
                            mTAG,
                            true, // isPreChallengeState
                            message.eapIdentifier,
                            eapAkaTypeData);
                default:
                    return buildClientErrorResponse(
                            message.eapIdentifier,
                            getEapMethod(),
                            AtClientErrorCode.UNABLE_TO_PROCESS);
            }
        }
    }

    protected class IdentityState extends EapMethodState {
        private final String mTAG = IdentityState.class.getSimpleName();

        private byte[] mIdentity;

        public EapResult process(EapMessage message) {
            EapResult result = handleEapSuccessFailureNotification(mTAG, message);
            if (result != null) {
                return result;
            }

            DecodeResult<? extends EapAkaTypeData> decodeResult =
                    decode(message.eapData.eapTypeData);
            if (!decodeResult.isSuccessfulDecode()) {
                return buildClientErrorResponse(
                        message.eapIdentifier, getEapMethod(), decodeResult.atClientErrorCode);
            }

            EapAkaTypeData eapAkaTypeData = decodeResult.eapTypeData;
            switch (eapAkaTypeData.eapSubtype) {
                case EAP_AKA_IDENTITY:
                    break;
                case EAP_AKA_CHALLENGE:
                    return transitionAndProcess(buildChallengeState(mIdentity), message);
                case EAP_AKA_NOTIFICATION:
                    return handleEapSimAkaNotification(
                            mTAG,
                            true, // isPreChallengeState
                            message.eapIdentifier,
                            eapAkaTypeData);
                default:
                    return buildClientErrorResponse(
                            message.eapIdentifier,
                            getEapMethod(),
                            AtClientErrorCode.UNABLE_TO_PROCESS);
            }

            if (!isValidIdentityAttributes(eapAkaTypeData)) {
                LOG.e(mTAG, "Invalid attributes: " + eapAkaTypeData.attributeMap.keySet());
                return buildClientErrorResponse(
                        message.eapIdentifier,
                        EAP_TYPE_AKA,
                        AtClientErrorCode.UNABLE_TO_PROCESS);
            }

            String imsi = mTelephonyManager.getSubscriberId();
            if (imsi == null) {
                LOG.e(mTAG, "Unable to get IMSI for subId=" + mEapUiccConfig.subId);
                return new EapError(
                        new EapSimAkaIdentityUnavailableException(
                                "IMSI for subId (" + mEapUiccConfig.subId + ") not available"));
            }
            String identityString = getIdentityPrefix() + imsi;
            mIdentity = identityString.getBytes(StandardCharsets.US_ASCII);
            LOG.d(mTAG, "EAP-AKA/Identity=" + LOG.pii(identityString));

            AtIdentity atIdentity;
            try {
                atIdentity = AtIdentity.getAtIdentity(mIdentity);
            } catch (EapSimAkaInvalidAttributeException ex) {
                LOG.wtf(mTAG, "Exception thrown while making AtIdentity attribute", ex);
                return new EapError(ex);
            }

            return buildResponseMessage(
                    getEapMethod(),
                    EAP_AKA_IDENTITY,
                    message.eapIdentifier,
                    Arrays.asList(atIdentity));
        }

        private boolean isValidIdentityAttributes(EapAkaTypeData eapAkaTypeData) {
            Set<Integer> attrs = eapAkaTypeData.attributeMap.keySet();

            // exactly one ID request type required
            int idRequests = 0;
            idRequests += attrs.contains(EAP_AT_PERMANENT_ID_REQ) ? 1 : 0;
            idRequests += attrs.contains(EAP_AT_ANY_ID_REQ) ? 1 : 0;
            idRequests += attrs.contains(EAP_AT_FULLAUTH_ID_REQ) ? 1 : 0;

            if (idRequests != 1) {
                return false;
            }

            // can't contain mac, iv, encr data
            if (attrs.contains(EAP_AT_MAC)
                    || attrs.contains(EAP_AT_IV)
                    || attrs.contains(EAP_AT_ENCR_DATA)) {
                return false;
            }
            return true;
        }
    }

    protected class ChallengeState extends EapMethodState {
        private final String mTAG = ChallengeState.class.getSimpleName();

        @VisibleForTesting boolean mHadSuccessfulChallenge = false;
        @VisibleForTesting protected final byte[] mIdentity;

        // IK and CK lengths defined as 16B (RFC 4187#1)
        private final int mIkLenBytes = 16;
        private final int mCkLenBytes = 16;

        // Tags for Successful and Synchronization responses
        private final byte mSuccess = (byte) 0xDB;
        private final byte mSynchronization = (byte) 0xDC;

        ChallengeState() {
            // use the EAP-Identity for the default value (RFC 4187#7)
            this(mEapIdentity);
        }

        ChallengeState(byte[] identity) {
            this.mIdentity = identity;
        }

        public EapResult process(EapMessage message) {
            if (message.eapCode == EAP_CODE_SUCCESS) {
                if (!mHadSuccessfulChallenge) {
                    LOG.e(mTAG, "Received unexpected EAP-Success");
                    return new EapError(
                            new EapInvalidRequestException(
                                    "Received an EAP-Success in the ChallengeState"));
                }
                transitionTo(new FinalState());
                return new EapSuccess(mMsk, mEmsk);
            } else if (message.eapCode == EAP_CODE_FAILURE) {
                transitionTo(new FinalState());
                return new EapFailure();
            } else if (message.eapData.eapType == EAP_NOTIFICATION) {
                return handleEapNotification(mTAG, message);
            }

            if (message.eapData.eapType != getEapMethod()) {
                return new EapError(new EapInvalidRequestException(
                        "Expected EAP Type " + getEapMethod()
                                + ", received " + message.eapData.eapType));
            }

            DecodeResult<? extends EapAkaTypeData> decodeResult =
                    decode(message.eapData.eapTypeData);
            if (!decodeResult.isSuccessfulDecode()) {
                return buildClientErrorResponse(
                        message.eapIdentifier, getEapMethod(), decodeResult.atClientErrorCode);
            }

            EapAkaTypeData eapAkaTypeData = decodeResult.eapTypeData;
            switch (eapAkaTypeData.eapSubtype) {
                case EAP_AKA_CHALLENGE:
                    break;
                case EAP_AKA_NOTIFICATION:
                    return handleEapSimAkaNotification(
                            mTAG,
                            false, // isPreChallengeState
                            message.eapIdentifier,
                            eapAkaTypeData);
                default:
                    return buildClientErrorResponse(
                            message.eapIdentifier,
                            getEapMethod(),
                            AtClientErrorCode.UNABLE_TO_PROCESS);
            }

            if (!isValidChallengeAttributes(eapAkaTypeData)) {
                LOG.e(mTAG, "Invalid attributes: " + eapAkaTypeData.attributeMap.keySet());
                return buildClientErrorResponse(
                        message.eapIdentifier, getEapMethod(), AtClientErrorCode.UNABLE_TO_PROCESS);
            }

            return handleChallengeAuthentication(message, eapAkaTypeData);
        }

        protected EapResult handleChallengeAuthentication(
                EapMessage message, EapAkaTypeData eapAkaTypeData) {
            RandChallengeResult result;
            try {
                result = getRandChallengeResult(eapAkaTypeData);
            } catch (EapAkaInvalidAuthenticationResponse ex) {
                return new EapError(ex);
            } catch (EapSimAkaInvalidLengthException | BufferUnderflowException ex) {
                LOG.e(mTAG, "Invalid response returned from SIM", ex);
                return buildClientErrorResponse(
                        message.eapIdentifier, getEapMethod(), AtClientErrorCode.UNABLE_TO_PROCESS);
            } catch (EapSimAkaAuthenticationFailureException ex) {
                // Return EAP-Response/AKA-Authentication-Reject when the AUTN is rejected
                // (RFC 4187#6.3.1)
                return buildAuthenticationRejectMessage(message.eapIdentifier);
            }

            if (!result.isSuccessfulResult()) {
                try {
                    return buildResponseMessage(
                            getEapMethod(),
                            EAP_AKA_SYNCHRONIZATION_FAILURE,
                            message.eapIdentifier,
                            Arrays.asList(new AtAuts(result.auts)));
                } catch (EapSimAkaInvalidAttributeException ex) {
                    LOG.wtf(mTAG, "Error creating an AtAuts attr", ex);
                    return new EapError(ex);
                }
            }

            EapResult eapResult =
                    generateAndPersistEapAkaKeys(result, message.eapIdentifier, eapAkaTypeData);
            if (eapResult != null) {
                return eapResult;
            }

            try {
                if (!isValidMac(mTAG, message, eapAkaTypeData, new byte[0])) {
                    return buildClientErrorResponse(
                            message.eapIdentifier,
                            getEapMethod(),
                            AtClientErrorCode.UNABLE_TO_PROCESS);
                }
            } catch (GeneralSecurityException
                    | EapSilentException
                    | EapSimAkaInvalidAttributeException ex) {
                // if the MAC can't be generated, we can't continue
                LOG.e(mTAG, "Error computing MAC for EapMessage", ex);
                return new EapError(ex);
            }

            // before sending a response, check for bidding-down attacks (RFC 5448#4)
            if (mSupportsEapAkaPrime) {
                AtBidding atBidding = (AtBidding) eapAkaTypeData.attributeMap.get(EAP_AT_BIDDING);
                if (atBidding != null && atBidding.doesServerSupportEapAkaPrime) {
                    LOG.w(
                            mTAG,
                            "Potential bidding down attack. AT_BIDDING attr included and EAP-AKA'"
                                + " is supported");
                    return buildAuthenticationRejectMessage(message.eapIdentifier);
                }
            }

            // server has been authenticated, so we can send a response
            try {
                mHadSuccessfulChallenge = true;
                return buildResponseMessageWithMac(
                        message.eapIdentifier,
                        EAP_AKA_CHALLENGE,
                        new byte[0],
                        Arrays.asList(AtRes.getAtRes(result.res)));
            } catch (EapSimAkaInvalidAttributeException ex) {
                LOG.wtf(mTAG, "Error creating AtRes value", ex);
                return new EapError(ex);
            }
        }

        @VisibleForTesting
        class RandChallengeResult {
            public final byte[] res;
            public final byte[] ik;
            public final byte[] ck;
            public final byte[] auts;

            RandChallengeResult(byte[] res, byte[] ik, byte[] ck)
                    throws EapSimAkaInvalidLengthException {
                if (!AtRes.isValidResLen(res.length)) {
                    throw new EapSimAkaInvalidLengthException("Invalid RES length");
                } else if (ik.length != mIkLenBytes) {
                    throw new EapSimAkaInvalidLengthException("Invalid IK length");
                } else if (ck.length != mCkLenBytes) {
                    throw new EapSimAkaInvalidLengthException("Invalid CK length");
                }

                this.res = res;
                this.ik = ik;
                this.ck = ck;
                this.auts = null;
            }

            RandChallengeResult(byte[] auts) throws EapSimAkaInvalidLengthException {
                if (auts.length != AtAuts.AUTS_LENGTH) {
                    throw new EapSimAkaInvalidLengthException("Invalid AUTS length");
                }

                this.res = null;
                this.ik = null;
                this.ck = null;
                this.auts = auts;
            }

            private boolean isSuccessfulResult() {
                return res != null && ik != null && ck != null;
            }
        }

        private boolean isValidChallengeAttributes(EapAkaTypeData eapAkaTypeData) {
            Set<Integer> attrs = eapAkaTypeData.attributeMap.keySet();

            // must contain: AT_RAND, AT_AUTN, AT_MAC
            return attrs.contains(EAP_AT_RAND)
                    && attrs.contains(EAP_AT_AUTN)
                    && attrs.contains(EAP_AT_MAC);
        }

        private RandChallengeResult getRandChallengeResult(EapAkaTypeData eapAkaTypeData)
                throws EapSimAkaAuthenticationFailureException, EapSimAkaInvalidLengthException {
            AtRandAka atRandAka = (AtRandAka) eapAkaTypeData.attributeMap.get(EAP_AT_RAND);
            AtAutn atAutn = (AtAutn) eapAkaTypeData.attributeMap.get(EAP_AT_AUTN);

            // pre-Base64 formatting needs to be: [Length][RAND][Length][AUTN]
            int randLen = atRandAka.rand.length;
            int autnLen = atAutn.autn.length;
            ByteBuffer formattedChallenge = ByteBuffer.allocate(1 + randLen + 1 + autnLen);
            formattedChallenge.put((byte) randLen);
            formattedChallenge.put(atRandAka.rand);
            formattedChallenge.put((byte) autnLen);
            formattedChallenge.put(atAutn.autn);

            byte[] challengeResponse =
                    processUiccAuthentication(
                            mTAG,
                            TelephonyManager.AUTHTYPE_EAP_AKA,
                            formattedChallenge.array());
            ByteBuffer buffer = ByteBuffer.wrap(challengeResponse);
            byte tag = buffer.get();

            switch (tag) {
                case mSuccess:
                    // response format: [tag][RES length][RES][IK length][IK][CK length][CK]
                    break;
                case mSynchronization:
                    // response format: [tag][AUTS length][AUTS]
                    byte[] auts = new byte[Byte.toUnsignedInt(buffer.get())];
                    buffer.get(auts);

                    LOG.i(mTAG, "Synchronization Failure");
                    LOG.d(
                            mTAG,
                            "RAND=" + LOG.pii(atRandAka.rand)
                                    + " AUTN=" + LOG.pii(atAutn.autn)
                                    + " AUTS=" + LOG.pii(auts));

                    return new RandChallengeResult(auts);
                default:
                    throw new EapAkaInvalidAuthenticationResponse(
                            "Invalid tag for UICC response: " + String.format("%02X", tag));
            }

            byte[] res = new byte[Byte.toUnsignedInt(buffer.get())];
            buffer.get(res);

            byte[] ik = new byte[Byte.toUnsignedInt(buffer.get())];
            buffer.get(ik);

            byte[] ck = new byte[Byte.toUnsignedInt(buffer.get())];
            buffer.get(ck);

            LOG.d(
                    mTAG,
                    "RAND=" + LOG.pii(atRandAka.rand)
                            + " AUTN=" + LOG.pii(atAutn.autn)
                            + " RES=" + LOG.pii(res)
                            + " IK=" + LOG.pii(ik)
                            + " CK=" + LOG.pii(ck));

            return new RandChallengeResult(res, ik, ck);
        }

        protected EapResult buildAuthenticationRejectMessage(int eapIdentifier) {
            return buildResponseMessage(
                    getEapMethod(),
                    EAP_AKA_AUTHENTICATION_REJECT,
                    eapIdentifier,
                    new ArrayList<>());
        }

        @Nullable
        protected EapResult generateAndPersistEapAkaKeys(
                RandChallengeResult result, int eapIdentifier, EapAkaTypeData eapAkaTypeData) {
            try {
                MessageDigest sha1 = MessageDigest.getInstance(MASTER_KEY_GENERATION_ALG);
                byte[] mkInputData = getMkInputData(result);
                generateAndPersistKeys(mTAG, sha1, new Fips186_2Prf(), mkInputData);
                return null;
            } catch (NoSuchAlgorithmException | BufferUnderflowException ex) {
                LOG.e(mTAG, "Error while creating keys", ex);
                return buildClientErrorResponse(
                        eapIdentifier, EAP_TYPE_AKA, AtClientErrorCode.UNABLE_TO_PROCESS);
            }
        }

        private byte[] getMkInputData(RandChallengeResult result) {
            int numInputBytes = mIdentity.length + result.ik.length + result.ck.length;
            ByteBuffer buffer = ByteBuffer.allocate(numInputBytes);
            buffer.put(mIdentity);
            buffer.put(result.ik);
            buffer.put(result.ck);
            return buffer.array();
        }
    }

    EapAkaTypeData getEapSimAkaTypeData(AtClientErrorCode clientErrorCode) {
        return new EapAkaTypeData(EAP_AKA_CLIENT_ERROR, Arrays.asList(clientErrorCode));
    }

    EapAkaTypeData getEapSimAkaTypeData(int eapSubtype, List<EapSimAkaAttribute> attributes) {
        return new EapAkaTypeData(eapSubtype, attributes);
    }
}