1package eu.siacs.conversations.crypto.sasl;
 2
 3import android.util.Base64;
 4
 5import java.math.BigInteger;
 6import java.nio.charset.Charset;
 7import java.security.MessageDigest;
 8import java.security.NoSuchAlgorithmException;
 9import java.security.SecureRandom;
10
11import eu.siacs.conversations.entities.Account;
12import eu.siacs.conversations.utils.CryptoHelper;
13import eu.siacs.conversations.xml.TagWriter;
14
15public class DigestMd5 extends SaslMechanism {
16	public DigestMd5(final TagWriter tagWriter, final Account account, final SecureRandom rng) {
17		super(tagWriter, account, rng);
18	}
19
20	public static String getMechanism() {
21		return "DIGEST-MD5";
22	}
23
24	private enum State {
25		INITIAL,
26		RESPONSE_SENT,
27	}
28
29	private State state = State.INITIAL;
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 = new Tokenizer(Base64.decode(challenge, Base64.DEFAULT));
39					String nonce = "";
40					for (final String token : tokenizer) {
41						final String[] parts = token.split("=");
42						if (parts[0].equals("nonce")) {
43							nonce = parts[1].replace("\"", "");
44						} else if (parts[0].equals("rspauth")) {
45							return "";
46						}
47					}
48					final String digestUri = "xmpp/" + account.getServer();
49					final String nonceCount = "00000001";
50					final String x = account.getUsername() + ":" + account.getServer() + ":"
51						+ account.getPassword();
52					final MessageDigest md = MessageDigest.getInstance("MD5");
53					final byte[] y = md.digest(x.getBytes(Charset.defaultCharset()));
54					final String cNonce = new BigInteger(100, rng).toString(32);
55					final byte[] a1 = CryptoHelper.concatenateByteArrays(y,
56							(":" + nonce + ":" + cNonce).getBytes(Charset
57																										.defaultCharset()));
58					final String a2 = "AUTHENTICATE:" + digestUri;
59					final String ha1 = CryptoHelper.bytesToHex(md.digest(a1));
60					final String ha2 = CryptoHelper.bytesToHex(md.digest(a2.getBytes(Charset
61									.defaultCharset())));
62					final String kd = ha1 + ":" + nonce + ":" + nonceCount + ":" + cNonce
63						+ ":auth:" + ha2;
64					final String response = CryptoHelper.bytesToHex(md.digest(kd.getBytes(Charset
65									.defaultCharset())));
66					final String saslString = "username=\"" + account.getUsername()
67						+ "\",realm=\"" + account.getServer() + "\",nonce=\""
68						+ nonce + "\",cnonce=\"" + cNonce + "\",nc=" + nonceCount
69						+ ",qop=auth,digest-uri=\"" + digestUri + "\",response="
70						+ response + ",charset=utf-8";
71					encodedResponse = Base64.encodeToString(
72							saslString.getBytes(Charset.defaultCharset()),
73							Base64.NO_WRAP);
74				} catch (final NoSuchAlgorithmException e) {
75					return "";
76				}
77
78				return encodedResponse;
79			case RESPONSE_SENT:
80				return "";
81		}
82		return "";
83	}
84}