234 lines
10 KiB
Java
234 lines
10 KiB
Java
package eu.siacs.conversations.crypto.sasl;
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import android.annotation.TargetApi;
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import android.os.Build;
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import android.util.Base64;
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import android.util.LruCache;
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import org.bouncycastle.crypto.Digest;
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import org.bouncycastle.crypto.macs.HMac;
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import org.bouncycastle.crypto.params.KeyParameter;
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import java.math.BigInteger;
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import java.nio.charset.Charset;
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import java.security.InvalidKeyException;
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import java.security.SecureRandom;
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import eu.siacs.conversations.entities.Account;
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import eu.siacs.conversations.utils.CryptoHelper;
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import eu.siacs.conversations.xml.TagWriter;
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@TargetApi(Build.VERSION_CODES.HONEYCOMB_MR1)
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abstract class ScramMechanism extends SaslMechanism {
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// TODO: When channel binding (SCRAM-SHA1-PLUS) is supported in future, generalize this to indicate support and/or usage.
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private final static String GS2_HEADER = "n,,";
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private static final byte[] CLIENT_KEY_BYTES = "Client Key".getBytes();
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private static final byte[] SERVER_KEY_BYTES = "Server Key".getBytes();
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private static final LruCache<String, KeyPair> CACHE;
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static HMac HMAC;
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static Digest DIGEST;
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static {
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CACHE = new LruCache<String, KeyPair>(10) {
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protected KeyPair create(final String k) {
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// Map keys are "bytesToHex(JID),bytesToHex(password),bytesToHex(salt),iterations,SASL-Mechanism".
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// Changing any of these values forces a cache miss. `CryptoHelper.bytesToHex()'
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// is applied to prevent commas in the strings breaking things.
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final String[] kparts = k.split(",", 5);
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try {
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final byte[] saltedPassword, serverKey, clientKey;
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saltedPassword = hi(CryptoHelper.hexToString(kparts[1]).getBytes(),
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Base64.decode(CryptoHelper.hexToString(kparts[2]), Base64.DEFAULT), Integer.valueOf(kparts[3]));
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serverKey = hmac(saltedPassword, SERVER_KEY_BYTES);
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clientKey = hmac(saltedPassword, CLIENT_KEY_BYTES);
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return new KeyPair(clientKey, serverKey);
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} catch (final InvalidKeyException | NumberFormatException e) {
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return null;
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}
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}
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};
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}
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private final String clientNonce;
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protected State state = State.INITIAL;
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private String clientFirstMessageBare;
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private byte[] serverSignature = null;
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ScramMechanism(final TagWriter tagWriter, final Account account, final SecureRandom rng) {
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super(tagWriter, account, rng);
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// This nonce should be different for each authentication attempt.
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clientNonce = CryptoHelper.random(100, rng);
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clientFirstMessageBare = "";
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}
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private static synchronized byte[] hmac(final byte[] key, final byte[] input)
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throws InvalidKeyException {
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HMAC.init(new KeyParameter(key));
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HMAC.update(input, 0, input.length);
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final byte[] out = new byte[HMAC.getMacSize()];
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HMAC.doFinal(out, 0);
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return out;
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}
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public static synchronized byte[] digest(byte[] bytes) {
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DIGEST.reset();
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DIGEST.update(bytes, 0, bytes.length);
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final byte[] out = new byte[DIGEST.getDigestSize()];
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DIGEST.doFinal(out, 0);
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return out;
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}
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/*
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* Hi() is, essentially, PBKDF2 [RFC2898] with HMAC() as the
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* pseudorandom function (PRF) and with dkLen == output length of
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* HMAC() == output length of H().
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*/
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private static synchronized byte[] hi(final byte[] key, final byte[] salt, final int iterations)
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throws InvalidKeyException {
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byte[] u = hmac(key, CryptoHelper.concatenateByteArrays(salt, CryptoHelper.ONE));
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byte[] out = u.clone();
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for (int i = 1; i < iterations; i++) {
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u = hmac(key, u);
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for (int j = 0; j < u.length; j++) {
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out[j] ^= u[j];
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}
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}
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return out;
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}
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@Override
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public String getClientFirstMessage() {
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if (clientFirstMessageBare.isEmpty() && state == State.INITIAL) {
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clientFirstMessageBare = "n=" + CryptoHelper.saslEscape(CryptoHelper.saslPrep(account.getUsername())) +
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",r=" + this.clientNonce;
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state = State.AUTH_TEXT_SENT;
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}
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return Base64.encodeToString(
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(GS2_HEADER + clientFirstMessageBare).getBytes(Charset.defaultCharset()),
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Base64.NO_WRAP);
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}
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@Override
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public String getResponse(final String challenge) throws AuthenticationException {
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switch (state) {
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case AUTH_TEXT_SENT:
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if (challenge == null) {
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throw new AuthenticationException("challenge can not be null");
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}
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byte[] serverFirstMessage;
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try {
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serverFirstMessage = Base64.decode(challenge, Base64.DEFAULT);
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} catch (IllegalArgumentException e) {
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throw new AuthenticationException("Unable to decode server challenge", e);
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}
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final Tokenizer tokenizer = new Tokenizer(serverFirstMessage);
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String nonce = "";
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int iterationCount = -1;
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String salt = "";
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for (final String token : tokenizer) {
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if (token.charAt(1) == '=') {
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switch (token.charAt(0)) {
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case 'i':
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try {
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iterationCount = Integer.parseInt(token.substring(2));
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} catch (final NumberFormatException e) {
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throw new AuthenticationException(e);
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}
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break;
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case 's':
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salt = token.substring(2);
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break;
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case 'r':
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nonce = token.substring(2);
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break;
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case 'm':
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/*
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* RFC 5802:
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* m: This attribute is reserved for future extensibility. In this
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* version of SCRAM, its presence in a client or a server message
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* MUST cause authentication failure when the attribute is parsed by
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* the other end.
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*/
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throw new AuthenticationException("Server sent reserved token: `m'");
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}
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}
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}
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if (iterationCount < 0) {
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throw new AuthenticationException("Server did not send iteration count");
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}
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if (nonce.isEmpty() || !nonce.startsWith(clientNonce)) {
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throw new AuthenticationException("Server nonce does not contain client nonce: " + nonce);
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}
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if (salt.isEmpty()) {
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throw new AuthenticationException("Server sent empty salt");
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}
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final String clientFinalMessageWithoutProof = "c=" + Base64.encodeToString(
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GS2_HEADER.getBytes(), Base64.NO_WRAP) + ",r=" + nonce;
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final byte[] authMessage = (clientFirstMessageBare + ',' + new String(serverFirstMessage) + ','
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+ clientFinalMessageWithoutProof).getBytes();
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// Map keys are "bytesToHex(JID),bytesToHex(password),bytesToHex(salt),iterations,SASL-Mechanism".
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final KeyPair keys = CACHE.get(
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CryptoHelper.bytesToHex(account.getJid().asBareJid().toEscapedString().getBytes()) + ","
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+ CryptoHelper.bytesToHex(account.getPassword().getBytes()) + ","
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+ CryptoHelper.bytesToHex(salt.getBytes()) + ","
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+ String.valueOf(iterationCount) + ","
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+ getMechanism()
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);
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if (keys == null) {
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throw new AuthenticationException("Invalid keys generated");
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}
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final byte[] clientSignature;
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try {
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serverSignature = hmac(keys.serverKey, authMessage);
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final byte[] storedKey = digest(keys.clientKey);
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clientSignature = hmac(storedKey, authMessage);
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} catch (final InvalidKeyException e) {
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throw new AuthenticationException(e);
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}
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final byte[] clientProof = new byte[keys.clientKey.length];
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for (int i = 0; i < clientProof.length; i++) {
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clientProof[i] = (byte) (keys.clientKey[i] ^ clientSignature[i]);
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}
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final String clientFinalMessage = clientFinalMessageWithoutProof + ",p=" +
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Base64.encodeToString(clientProof, Base64.NO_WRAP);
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state = State.RESPONSE_SENT;
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return Base64.encodeToString(clientFinalMessage.getBytes(), Base64.NO_WRAP);
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case RESPONSE_SENT:
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try {
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final String clientCalculatedServerFinalMessage = "v=" +
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Base64.encodeToString(serverSignature, Base64.NO_WRAP);
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if (!clientCalculatedServerFinalMessage.equals(new String(Base64.decode(challenge, Base64.DEFAULT)))) {
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throw new Exception();
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}
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state = State.VALID_SERVER_RESPONSE;
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return "";
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} catch (Exception e) {
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throw new AuthenticationException("Server final message does not match calculated final message");
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}
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default:
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throw new InvalidStateException(state);
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}
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}
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private static class KeyPair {
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final byte[] clientKey;
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final byte[] serverKey;
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KeyPair(final byte[] clientKey, final byte[] serverKey) {
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this.clientKey = clientKey;
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this.serverKey = serverKey;
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}
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}
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}
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