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 State state = State.INITIAL;
25
26	@Override
27	public String getResponse(final String challenge) throws AuthenticationException {
28		switch (state) {
29			case INITIAL:
30				state = State.RESPONSE_SENT;
31				final String encodedResponse;
32				try {
33					final Tokenizer tokenizer = new Tokenizer(Base64.decode(challenge, Base64.DEFAULT));
34					String nonce = "";
35					for (final String token : tokenizer) {
36						final String[] parts = token.split("=");
37						if (parts[0].equals("nonce")) {
38							nonce = parts[1].replace("\"", "");
39						} else if (parts[0].equals("rspauth")) {
40							return "";
41						}
42					}
43					final String digestUri = "xmpp/" + account.getServer();
44					final String nonceCount = "00000001";
45					final String x = account.getUsername() + ":" + account.getServer() + ":"
46						+ account.getPassword();
47					final MessageDigest md = MessageDigest.getInstance("MD5");
48					final byte[] y = md.digest(x.getBytes(Charset.defaultCharset()));
49					final String cNonce = new BigInteger(100, rng).toString(32);
50					final byte[] a1 = CryptoHelper.concatenateByteArrays(y,
51							(":" + nonce + ":" + cNonce).getBytes(Charset.defaultCharset()));
52					final String a2 = "AUTHENTICATE:" + digestUri;
53					final String ha1 = CryptoHelper.bytesToHex(md.digest(a1));
54					final String ha2 = CryptoHelper.bytesToHex(md.digest(a2.getBytes(Charset
55									.defaultCharset())));
56					final String kd = ha1 + ":" + nonce + ":" + nonceCount + ":" + cNonce
57						+ ":auth:" + ha2;
58					final String response = CryptoHelper.bytesToHex(md.digest(kd.getBytes(Charset
59									.defaultCharset())));
60					final String saslString = "username=\"" + account.getUsername()
61						+ "\",realm=\"" + account.getServer() + "\",nonce=\""
62						+ nonce + "\",cnonce=\"" + cNonce + "\",nc=" + nonceCount
63						+ ",qop=auth,digest-uri=\"" + digestUri + "\",response="
64						+ response + ",charset=utf-8";
65					encodedResponse = Base64.encodeToString(
66							saslString.getBytes(Charset.defaultCharset()),
67							Base64.NO_WRAP);
68				} catch (final NoSuchAlgorithmException e) {
69					throw new AuthenticationException(e);
70				}
71
72				return encodedResponse;
73			case RESPONSE_SENT:
74				state = State.VALID_SERVER_RESPONSE;
75				break;
76			default:
77				throw new InvalidStateException(state);
78		}
79		return null;
80	}
81}