1package eu.siacs.conversations.crypto.axolotl;
2
3import android.util.Base64;
4import android.util.Log;
5import eu.siacs.conversations.Config;
6import eu.siacs.conversations.utils.Compatibility;
7import eu.siacs.conversations.xml.Element;
8import eu.siacs.conversations.xmpp.Jid;
9import java.security.InvalidAlgorithmParameterException;
10import java.security.InvalidKeyException;
11import java.security.NoSuchAlgorithmException;
12import java.security.NoSuchProviderException;
13import java.security.SecureRandom;
14import java.util.ArrayList;
15import java.util.List;
16import javax.crypto.BadPaddingException;
17import javax.crypto.Cipher;
18import javax.crypto.IllegalBlockSizeException;
19import javax.crypto.KeyGenerator;
20import javax.crypto.NoSuchPaddingException;
21import javax.crypto.SecretKey;
22import javax.crypto.spec.IvParameterSpec;
23import javax.crypto.spec.SecretKeySpec;
24
25public class XmppAxolotlMessage {
26 public static final String CONTAINERTAG = "encrypted";
27 private static final String HEADER = "header";
28 private static final String SOURCEID = "sid";
29 private static final String KEYTAG = "key";
30 private static final String REMOTEID = "rid";
31 private static final String IVTAG = "iv";
32 private static final String PAYLOAD = "payload";
33
34 private static final String KEYTYPE = "AES";
35 private static final String CIPHERMODE = "AES/GCM/NoPadding";
36 private static final String PROVIDER = "BC";
37 private final List<XmppAxolotlSession.AxolotlKey> keys;
38 private final Jid from;
39 private final int sourceDeviceId;
40 private byte[] innerKey;
41 private byte[] ciphertext = null;
42 private byte[] authtagPlusInnerKey = null;
43 private byte[] iv = null;
44
45 private XmppAxolotlMessage(final Element axolotlMessage, final Jid from)
46 throws IllegalArgumentException {
47 this.from = from;
48 Element header = axolotlMessage.findChild(HEADER);
49 try {
50 this.sourceDeviceId = Integer.parseInt(header.getAttribute(SOURCEID));
51 } catch (NumberFormatException e) {
52 throw new IllegalArgumentException("invalid source id");
53 }
54 List<Element> keyElements = header.getChildren();
55 this.keys = new ArrayList<>();
56 for (Element keyElement : keyElements) {
57 switch (keyElement.getName()) {
58 case KEYTAG:
59 try {
60 int recipientId = Integer.parseInt(keyElement.getAttribute(REMOTEID));
61 byte[] key = Base64.decode(keyElement.getContent().trim(), Base64.DEFAULT);
62 boolean isPreKey = keyElement.getAttributeAsBoolean("prekey");
63 this.keys.add(
64 new XmppAxolotlSession.AxolotlKey(recipientId, key, isPreKey));
65 } catch (NumberFormatException e) {
66 throw new IllegalArgumentException("invalid remote id");
67 }
68 break;
69 case IVTAG:
70 if (this.iv != null) {
71 throw new IllegalArgumentException("Duplicate iv entry");
72 }
73 iv = Base64.decode(keyElement.getContent().trim(), Base64.DEFAULT);
74 break;
75 default:
76 Log.w(Config.LOGTAG, "Unexpected element in header: " + keyElement);
77 break;
78 }
79 }
80 final Element payloadElement =
81 axolotlMessage.findChildEnsureSingle(PAYLOAD, AxolotlService.PEP_PREFIX);
82 if (payloadElement != null) {
83 ciphertext = Base64.decode(payloadElement.getContent().trim(), Base64.DEFAULT);
84 }
85 }
86
87 XmppAxolotlMessage(Jid from, int sourceDeviceId) {
88 this.from = from;
89 this.sourceDeviceId = sourceDeviceId;
90 this.keys = new ArrayList<>();
91 this.iv = generateIv();
92 this.innerKey = generateKey();
93 }
94
95 public static int parseSourceId(final Element axolotlMessage) throws IllegalArgumentException {
96 final Element header = axolotlMessage.findChild(HEADER);
97 if (header == null) {
98 throw new IllegalArgumentException("No header found");
99 }
100 try {
101 return Integer.parseInt(header.getAttribute(SOURCEID));
102 } catch (NumberFormatException e) {
103 throw new IllegalArgumentException("invalid source id");
104 }
105 }
106
107 public static XmppAxolotlMessage fromElement(Element element, Jid from) {
108 return new XmppAxolotlMessage(element, from);
109 }
110
111 private static byte[] generateKey() {
112 try {
113 KeyGenerator generator = KeyGenerator.getInstance(KEYTYPE);
114 generator.init(128);
115 return generator.generateKey().getEncoded();
116 } catch (NoSuchAlgorithmException e) {
117 throw new IllegalStateException(e);
118 }
119 }
120
121 private static byte[] generateIv() {
122 final SecureRandom random = new SecureRandom();
123 final byte[] iv = new byte[12];
124 random.nextBytes(iv);
125 return iv;
126 }
127
128 private static byte[] getPaddedBytes(String plaintext) {
129 int plainLength = plaintext.getBytes().length;
130 int pad = Math.max(64, (plainLength / 32 + 1) * 32) - plainLength;
131 SecureRandom random = new SecureRandom();
132 int left = random.nextInt(pad);
133 int right = pad - left;
134 StringBuilder builder = new StringBuilder(plaintext);
135 for (int i = 0; i < left; ++i) {
136 builder.insert(0, random.nextBoolean() ? "\t" : " ");
137 }
138 for (int i = 0; i < right; ++i) {
139 builder.append(random.nextBoolean() ? "\t" : " ");
140 }
141 return builder.toString().getBytes();
142 }
143
144 public boolean hasPayload() {
145 return ciphertext != null;
146 }
147
148 void encrypt(final String plaintext) throws CryptoFailedException {
149 try {
150 SecretKey secretKey = new SecretKeySpec(innerKey, KEYTYPE);
151 IvParameterSpec ivSpec = new IvParameterSpec(iv);
152 Cipher cipher =
153 Compatibility.twentyEight()
154 ? Cipher.getInstance(CIPHERMODE)
155 : Cipher.getInstance(CIPHERMODE, PROVIDER);
156 cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);
157 this.ciphertext =
158 cipher.doFinal(
159 Config.OMEMO_PADDING
160 ? getPaddedBytes(plaintext)
161 : plaintext.getBytes());
162 if (Config.PUT_AUTH_TAG_INTO_KEY && this.ciphertext != null) {
163 this.authtagPlusInnerKey = new byte[16 + 16];
164 byte[] ciphertext = new byte[this.ciphertext.length - 16];
165 System.arraycopy(this.ciphertext, 0, ciphertext, 0, ciphertext.length);
166 System.arraycopy(this.ciphertext, ciphertext.length, authtagPlusInnerKey, 16, 16);
167 System.arraycopy(this.innerKey, 0, authtagPlusInnerKey, 0, this.innerKey.length);
168 this.ciphertext = ciphertext;
169 }
170 } catch (NoSuchAlgorithmException
171 | NoSuchPaddingException
172 | InvalidKeyException
173 | IllegalBlockSizeException
174 | BadPaddingException
175 | NoSuchProviderException
176 | InvalidAlgorithmParameterException e) {
177 throw new CryptoFailedException(e);
178 }
179 }
180
181 public Jid getFrom() {
182 return this.from;
183 }
184
185 int getSenderDeviceId() {
186 return sourceDeviceId;
187 }
188
189 void addDevice(XmppAxolotlSession session) {
190 addDevice(session, false);
191 }
192
193 void addDevice(XmppAxolotlSession session, boolean ignoreSessionTrust) {
194 XmppAxolotlSession.AxolotlKey key;
195 if (authtagPlusInnerKey != null) {
196 key = session.processSending(authtagPlusInnerKey, ignoreSessionTrust);
197 } else {
198 key = session.processSending(innerKey, ignoreSessionTrust);
199 }
200 if (key != null) {
201 keys.add(key);
202 }
203 }
204
205 public byte[] getInnerKey() {
206 return innerKey;
207 }
208
209 public byte[] getIV() {
210 return this.iv;
211 }
212
213 public Element toElement() {
214 Element encryptionElement = new Element(CONTAINERTAG, AxolotlService.PEP_PREFIX);
215 Element headerElement = encryptionElement.addChild(HEADER);
216 headerElement.setAttribute(SOURCEID, sourceDeviceId);
217 for (XmppAxolotlSession.AxolotlKey key : keys) {
218 Element keyElement = new Element(KEYTAG);
219 keyElement.setAttribute(REMOTEID, key.deviceId);
220 if (key.prekey) {
221 keyElement.setAttribute("prekey", "true");
222 }
223 keyElement.setContent(Base64.encodeToString(key.key, Base64.NO_WRAP));
224 headerElement.addChild(keyElement);
225 }
226 headerElement.addChild(IVTAG).setContent(Base64.encodeToString(iv, Base64.NO_WRAP));
227 if (ciphertext != null) {
228 Element payload = encryptionElement.addChild(PAYLOAD);
229 payload.setContent(Base64.encodeToString(ciphertext, Base64.NO_WRAP));
230 }
231 return encryptionElement;
232 }
233
234 private byte[] unpackKey(XmppAxolotlSession session, Integer sourceDeviceId)
235 throws CryptoFailedException {
236 ArrayList<XmppAxolotlSession.AxolotlKey> possibleKeys = new ArrayList<>();
237 for (XmppAxolotlSession.AxolotlKey key : keys) {
238 if (key.deviceId == sourceDeviceId) {
239 possibleKeys.add(key);
240 }
241 }
242 if (possibleKeys.size() == 0) {
243 throw new NotEncryptedForThisDeviceException();
244 }
245 return session.processReceiving(possibleKeys);
246 }
247
248 XmppAxolotlKeyTransportMessage getParameters(XmppAxolotlSession session, Integer sourceDeviceId)
249 throws CryptoFailedException {
250 return new XmppAxolotlKeyTransportMessage(
251 session.getFingerprint(), unpackKey(session, sourceDeviceId), getIV());
252 }
253
254 public XmppAxolotlPlaintextMessage decrypt(XmppAxolotlSession session, Integer sourceDeviceId)
255 throws CryptoFailedException {
256 XmppAxolotlPlaintextMessage plaintextMessage = null;
257 byte[] key = unpackKey(session, sourceDeviceId);
258 if (key != null) {
259 try {
260 if (key.length < 32) {
261 throw new OutdatedSenderException(
262 "Key did not contain auth tag. Sender needs to update their OMEMO"
263 + " client");
264 }
265 final int authTagLength = key.length - 16;
266 byte[] newCipherText = new byte[key.length - 16 + ciphertext.length];
267 byte[] newKey = new byte[16];
268 System.arraycopy(ciphertext, 0, newCipherText, 0, ciphertext.length);
269 System.arraycopy(key, 16, newCipherText, ciphertext.length, authTagLength);
270 System.arraycopy(key, 0, newKey, 0, newKey.length);
271 ciphertext = newCipherText;
272 key = newKey;
273
274 final Cipher cipher =
275 Compatibility.twentyEight()
276 ? Cipher.getInstance(CIPHERMODE)
277 : Cipher.getInstance(CIPHERMODE, PROVIDER);
278 SecretKeySpec keySpec = new SecretKeySpec(key, KEYTYPE);
279 IvParameterSpec ivSpec = new IvParameterSpec(iv);
280
281 cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
282
283 String plaintext = new String(cipher.doFinal(ciphertext));
284 plaintextMessage =
285 new XmppAxolotlPlaintextMessage(
286 Config.OMEMO_PADDING ? plaintext.trim() : plaintext,
287 session.getFingerprint());
288
289 } catch (NoSuchAlgorithmException
290 | NoSuchPaddingException
291 | InvalidKeyException
292 | InvalidAlgorithmParameterException
293 | IllegalBlockSizeException
294 | BadPaddingException
295 | NoSuchProviderException e) {
296 throw new CryptoFailedException(e);
297 }
298 }
299 return plaintextMessage;
300 }
301
302 public static class XmppAxolotlPlaintextMessage {
303 private final String plaintext;
304 private final String fingerprint;
305
306 XmppAxolotlPlaintextMessage(String plaintext, String fingerprint) {
307 this.plaintext = plaintext;
308 this.fingerprint = fingerprint;
309 }
310
311 public String getPlaintext() {
312 return plaintext;
313 }
314
315 public String getFingerprint() {
316 return fingerprint;
317 }
318 }
319
320 public static class XmppAxolotlKeyTransportMessage {
321 private final String fingerprint;
322 private final byte[] key;
323 private final byte[] iv;
324
325 XmppAxolotlKeyTransportMessage(String fingerprint, byte[] key, byte[] iv) {
326 this.fingerprint = fingerprint;
327 this.key = key;
328 this.iv = iv;
329 }
330
331 public String getFingerprint() {
332 return fingerprint;
333 }
334
335 public byte[] getKey() {
336 return key;
337 }
338
339 public byte[] getIv() {
340 return iv;
341 }
342 }
343}