1package eu.siacs.conversations.crypto.sasl;
  2
  3import android.util.Base64;
  4
  5import java.nio.charset.Charset;
  6import java.security.MessageDigest;
  7import java.security.NoSuchAlgorithmException;
  8
  9import eu.siacs.conversations.entities.Account;
 10import eu.siacs.conversations.utils.CryptoHelper;
 11
 12public class DigestMd5 extends SaslMechanism {
 13
 14    public static final String MECHANISM = "DIGEST-MD5";
 15    private State state = State.INITIAL;
 16
 17    public DigestMd5(final Account account) {
 18        super(account);
 19    }
 20
 21    @Override
 22    public int getPriority() {
 23        return 10;
 24    }
 25
 26    @Override
 27    public String getMechanism() {
 28        return MECHANISM;
 29    }
 30
 31    @Override
 32    public String getResponse(final String challenge) throws AuthenticationException {
 33        switch (state) {
 34            case INITIAL:
 35                state = State.RESPONSE_SENT;
 36                final String encodedResponse;
 37                try {
 38                    final Tokenizer tokenizer =
 39                            new Tokenizer(Base64.decode(challenge, Base64.DEFAULT));
 40                    String nonce = "";
 41                    for (final String token : tokenizer) {
 42                        final String[] parts = token.split("=", 2);
 43                        if (parts[0].equals("nonce")) {
 44                            nonce = parts[1].replace("\"", "");
 45                        } else if (parts[0].equals("rspauth")) {
 46                            return "";
 47                        }
 48                    }
 49                    final String digestUri = "xmpp/" + account.getServer();
 50                    final String nonceCount = "00000001";
 51                    final String x =
 52                            account.getUsername()
 53                                    + ":"
 54                                    + account.getServer()
 55                                    + ":"
 56                                    + account.getPassword();
 57                    final MessageDigest md = MessageDigest.getInstance("MD5");
 58                    final byte[] y = md.digest(x.getBytes(Charset.defaultCharset()));
 59                    final String cNonce = CryptoHelper.random(100);
 60                    final byte[] a1 =
 61                            CryptoHelper.concatenateByteArrays(
 62                                    y,
 63                                    (":" + nonce + ":" + cNonce)
 64                                            .getBytes(Charset.defaultCharset()));
 65                    final String a2 = "AUTHENTICATE:" + digestUri;
 66                    final String ha1 = CryptoHelper.bytesToHex(md.digest(a1));
 67                    final String ha2 =
 68                            CryptoHelper.bytesToHex(
 69                                    md.digest(a2.getBytes(Charset.defaultCharset())));
 70                    final String kd =
 71                            ha1 + ":" + nonce + ":" + nonceCount + ":" + cNonce + ":auth:" + ha2;
 72                    final String response =
 73                            CryptoHelper.bytesToHex(
 74                                    md.digest(kd.getBytes(Charset.defaultCharset())));
 75                    final String saslString =
 76                            "username=\""
 77                                    + account.getUsername()
 78                                    + "\",realm=\""
 79                                    + account.getServer()
 80                                    + "\",nonce=\""
 81                                    + nonce
 82                                    + "\",cnonce=\""
 83                                    + cNonce
 84                                    + "\",nc="
 85                                    + nonceCount
 86                                    + ",qop=auth,digest-uri=\""
 87                                    + digestUri
 88                                    + "\",response="
 89                                    + response
 90                                    + ",charset=utf-8";
 91                    encodedResponse =
 92                            Base64.encodeToString(
 93                                    saslString.getBytes(Charset.defaultCharset()), Base64.NO_WRAP);
 94                } catch (final NoSuchAlgorithmException e) {
 95                    throw new AuthenticationException(e);
 96                }
 97
 98                return encodedResponse;
 99            case RESPONSE_SENT:
100                state = State.VALID_SERVER_RESPONSE;
101                break;
102            case VALID_SERVER_RESPONSE:
103                if (challenge == null) {
104                    return null; // everything is fine
105                }
106            default:
107                throw new InvalidStateException(state);
108        }
109        return null;
110    }
111}