318 lines
12 KiB
Java
318 lines
12 KiB
Java
package eu.siacs.conversations.crypto.axolotl;
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import android.util.Base64;
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import android.util.Log;
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import java.security.InvalidAlgorithmParameterException;
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import java.security.InvalidKeyException;
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import java.security.NoSuchAlgorithmException;
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import java.security.NoSuchProviderException;
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import java.security.SecureRandom;
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import java.util.ArrayList;
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import java.util.List;
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import javax.crypto.BadPaddingException;
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import javax.crypto.Cipher;
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import javax.crypto.IllegalBlockSizeException;
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import javax.crypto.KeyGenerator;
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import javax.crypto.NoSuchPaddingException;
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import javax.crypto.SecretKey;
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import javax.crypto.spec.IvParameterSpec;
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import javax.crypto.spec.SecretKeySpec;
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import eu.siacs.conversations.Config;
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import eu.siacs.conversations.utils.Compatibility;
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import eu.siacs.conversations.xml.Element;
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import eu.siacs.conversations.xmpp.Jid;
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public class XmppAxolotlMessage {
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public static final String CONTAINERTAG = "encrypted";
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private static final String HEADER = "header";
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private static final String SOURCEID = "sid";
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private static final String KEYTAG = "key";
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private static final String REMOTEID = "rid";
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private static final String IVTAG = "iv";
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private static final String PAYLOAD = "payload";
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private static final String KEYTYPE = "AES";
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private static final String CIPHERMODE = "AES/GCM/NoPadding";
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private static final String PROVIDER = "BC";
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private final List<XmppAxolotlSession.AxolotlKey> keys;
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private final Jid from;
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private final int sourceDeviceId;
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private byte[] innerKey;
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private byte[] ciphertext = null;
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private byte[] authtagPlusInnerKey = null;
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private byte[] iv = null;
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private XmppAxolotlMessage(final Element axolotlMessage, final Jid from) throws IllegalArgumentException {
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this.from = from;
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Element header = axolotlMessage.findChild(HEADER);
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try {
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this.sourceDeviceId = Integer.parseInt(header.getAttribute(SOURCEID));
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} catch (NumberFormatException e) {
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throw new IllegalArgumentException("invalid source id");
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}
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List<Element> keyElements = header.getChildren();
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this.keys = new ArrayList<>();
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for (Element keyElement : keyElements) {
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switch (keyElement.getName()) {
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case KEYTAG:
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try {
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Integer recipientId = Integer.parseInt(keyElement.getAttribute(REMOTEID));
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byte[] key = Base64.decode(keyElement.getContent().trim(), Base64.DEFAULT);
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boolean isPreKey = keyElement.getAttributeAsBoolean("prekey");
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this.keys.add(new XmppAxolotlSession.AxolotlKey(recipientId, key, isPreKey));
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} catch (NumberFormatException e) {
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throw new IllegalArgumentException("invalid remote id");
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}
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break;
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case IVTAG:
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if (this.iv != null) {
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throw new IllegalArgumentException("Duplicate iv entry");
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}
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iv = Base64.decode(keyElement.getContent().trim(), Base64.DEFAULT);
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break;
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default:
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Log.w(Config.LOGTAG, "Unexpected element in header: " + keyElement.toString());
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break;
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}
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}
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final Element payloadElement = axolotlMessage.findChildEnsureSingle(PAYLOAD, AxolotlService.PEP_PREFIX);
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if (payloadElement != null) {
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ciphertext = Base64.decode(payloadElement.getContent().trim(), Base64.DEFAULT);
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}
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}
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XmppAxolotlMessage(Jid from, int sourceDeviceId) {
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this.from = from;
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this.sourceDeviceId = sourceDeviceId;
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this.keys = new ArrayList<>();
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this.iv = generateIv();
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this.innerKey = generateKey();
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}
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public static int parseSourceId(final Element axolotlMessage) throws IllegalArgumentException {
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final Element header = axolotlMessage.findChild(HEADER);
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if (header == null) {
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throw new IllegalArgumentException("No header found");
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}
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try {
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return Integer.parseInt(header.getAttribute(SOURCEID));
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} catch (NumberFormatException e) {
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throw new IllegalArgumentException("invalid source id");
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}
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}
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public static XmppAxolotlMessage fromElement(Element element, Jid from) {
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return new XmppAxolotlMessage(element, from);
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}
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private static byte[] generateKey() {
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try {
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KeyGenerator generator = KeyGenerator.getInstance(KEYTYPE);
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generator.init(128);
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return generator.generateKey().getEncoded();
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} catch (NoSuchAlgorithmException e) {
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throw new IllegalStateException(e);
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}
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}
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private static byte[] generateIv() {
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final SecureRandom random = new SecureRandom();
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final byte[] iv = new byte[12];
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random.nextBytes(iv);
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return iv;
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}
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private static byte[] getPaddedBytes(String plaintext) {
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int plainLength = plaintext.getBytes().length;
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int pad = Math.max(64, (plainLength / 32 + 1) * 32) - plainLength;
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SecureRandom random = new SecureRandom();
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int left = random.nextInt(pad);
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int right = pad - left;
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StringBuilder builder = new StringBuilder(plaintext);
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for (int i = 0; i < left; ++i) {
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builder.insert(0, random.nextBoolean() ? "\t" : " ");
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}
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for (int i = 0; i < right; ++i) {
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builder.append(random.nextBoolean() ? "\t" : " ");
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}
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return builder.toString().getBytes();
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}
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public boolean hasPayload() {
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return ciphertext != null;
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}
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void encrypt(String plaintext) throws CryptoFailedException {
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try {
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SecretKey secretKey = new SecretKeySpec(innerKey, KEYTYPE);
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IvParameterSpec ivSpec = new IvParameterSpec(iv);
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Cipher cipher = Compatibility.twentyEight() ? Cipher.getInstance(CIPHERMODE) : Cipher.getInstance(CIPHERMODE, PROVIDER);
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cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);
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this.ciphertext = cipher.doFinal(Config.OMEMO_PADDING ? getPaddedBytes(plaintext) : plaintext.getBytes());
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if (Config.PUT_AUTH_TAG_INTO_KEY && this.ciphertext != null) {
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this.authtagPlusInnerKey = new byte[16 + 16];
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byte[] ciphertext = new byte[this.ciphertext.length - 16];
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System.arraycopy(this.ciphertext, 0, ciphertext, 0, ciphertext.length);
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System.arraycopy(this.ciphertext, ciphertext.length, authtagPlusInnerKey, 16, 16);
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System.arraycopy(this.innerKey, 0, authtagPlusInnerKey, 0, this.innerKey.length);
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this.ciphertext = ciphertext;
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}
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} catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException
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| IllegalBlockSizeException | BadPaddingException | NoSuchProviderException
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| InvalidAlgorithmParameterException e) {
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throw new CryptoFailedException(e);
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}
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}
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public Jid getFrom() {
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return this.from;
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}
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int getSenderDeviceId() {
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return sourceDeviceId;
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}
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void addDevice(XmppAxolotlSession session) {
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addDevice(session, false);
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}
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void addDevice(XmppAxolotlSession session, boolean ignoreSessionTrust) {
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XmppAxolotlSession.AxolotlKey key;
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if (authtagPlusInnerKey != null) {
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key = session.processSending(authtagPlusInnerKey, ignoreSessionTrust);
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} else {
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key = session.processSending(innerKey, ignoreSessionTrust);
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}
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if (key != null) {
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keys.add(key);
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}
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}
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public byte[] getInnerKey() {
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return innerKey;
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}
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public byte[] getIV() {
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return this.iv;
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}
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public Element toElement() {
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Element encryptionElement = new Element(CONTAINERTAG, AxolotlService.PEP_PREFIX);
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Element headerElement = encryptionElement.addChild(HEADER);
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headerElement.setAttribute(SOURCEID, sourceDeviceId);
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for (XmppAxolotlSession.AxolotlKey key : keys) {
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Element keyElement = new Element(KEYTAG);
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keyElement.setAttribute(REMOTEID, key.deviceId);
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if (key.prekey) {
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keyElement.setAttribute("prekey", "true");
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}
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keyElement.setContent(Base64.encodeToString(key.key, Base64.NO_WRAP));
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headerElement.addChild(keyElement);
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}
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headerElement.addChild(IVTAG).setContent(Base64.encodeToString(iv, Base64.NO_WRAP));
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if (ciphertext != null) {
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Element payload = encryptionElement.addChild(PAYLOAD);
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payload.setContent(Base64.encodeToString(ciphertext, Base64.NO_WRAP));
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}
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return encryptionElement;
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}
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private byte[] unpackKey(XmppAxolotlSession session, Integer sourceDeviceId) throws CryptoFailedException {
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ArrayList<XmppAxolotlSession.AxolotlKey> possibleKeys = new ArrayList<>();
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for (XmppAxolotlSession.AxolotlKey key : keys) {
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if (key.deviceId == sourceDeviceId) {
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possibleKeys.add(key);
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}
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}
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if (possibleKeys.size() == 0) {
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throw new NotEncryptedForThisDeviceException();
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}
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return session.processReceiving(possibleKeys);
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}
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XmppAxolotlKeyTransportMessage getParameters(XmppAxolotlSession session, Integer sourceDeviceId) throws CryptoFailedException {
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return new XmppAxolotlKeyTransportMessage(session.getFingerprint(), unpackKey(session, sourceDeviceId), getIV());
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}
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public XmppAxolotlPlaintextMessage decrypt(XmppAxolotlSession session, Integer sourceDeviceId) throws CryptoFailedException {
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XmppAxolotlPlaintextMessage plaintextMessage = null;
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byte[] key = unpackKey(session, sourceDeviceId);
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if (key != null) {
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try {
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if (key.length < 32) {
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throw new OutdatedSenderException("Key did not contain auth tag. Sender needs to update their OMEMO client");
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}
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final int authTagLength = key.length - 16;
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byte[] newCipherText = new byte[key.length - 16 + ciphertext.length];
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byte[] newKey = new byte[16];
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System.arraycopy(ciphertext, 0, newCipherText, 0, ciphertext.length);
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System.arraycopy(key, 16, newCipherText, ciphertext.length, authTagLength);
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System.arraycopy(key, 0, newKey, 0, newKey.length);
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ciphertext = newCipherText;
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key = newKey;
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final Cipher cipher = Compatibility.twentyEight() ? Cipher.getInstance(CIPHERMODE) : Cipher.getInstance(CIPHERMODE, PROVIDER);
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SecretKeySpec keySpec = new SecretKeySpec(key, KEYTYPE);
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IvParameterSpec ivSpec = new IvParameterSpec(iv);
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cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
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String plaintext = new String(cipher.doFinal(ciphertext));
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plaintextMessage = new XmppAxolotlPlaintextMessage(Config.OMEMO_PADDING ? plaintext.trim() : plaintext, session.getFingerprint());
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} catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException
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| InvalidAlgorithmParameterException | IllegalBlockSizeException
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| BadPaddingException | NoSuchProviderException e) {
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throw new CryptoFailedException(e);
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}
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}
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return plaintextMessage;
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}
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public static class XmppAxolotlPlaintextMessage {
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private final String plaintext;
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private final String fingerprint;
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XmppAxolotlPlaintextMessage(String plaintext, String fingerprint) {
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this.plaintext = plaintext;
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this.fingerprint = fingerprint;
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}
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public String getPlaintext() {
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return plaintext;
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}
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public String getFingerprint() {
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return fingerprint;
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}
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}
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public static class XmppAxolotlKeyTransportMessage {
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private final String fingerprint;
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private final byte[] key;
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private final byte[] iv;
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XmppAxolotlKeyTransportMessage(String fingerprint, byte[] key, byte[] iv) {
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this.fingerprint = fingerprint;
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this.key = key;
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this.iv = iv;
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}
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public String getFingerprint() {
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return fingerprint;
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}
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public byte[] getKey() {
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return key;
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}
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public byte[] getIv() {
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return iv;
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}
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}
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}
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