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