package eu.siacs.conversations.crypto.axolotl; import android.util.Base64; import java.security.InvalidAlgorithmParameterException; import java.security.NoSuchAlgorithmException; import java.security.InvalidKeyException; import java.util.HashSet; import java.util.Set; import javax.crypto.BadPaddingException; import javax.crypto.Cipher; import javax.crypto.IllegalBlockSizeException; import javax.crypto.KeyGenerator; import javax.crypto.NoSuchPaddingException; import javax.crypto.SecretKey; import javax.crypto.spec.IvParameterSpec; import javax.crypto.spec.SecretKeySpec; import eu.siacs.conversations.entities.Contact; import eu.siacs.conversations.xml.Element; public class XmppAxolotlMessage { private byte[] innerKey; private byte[] ciphertext; private byte[] iv; private final Set headers; private final Contact contact; private final int sourceDeviceId; public static class XmppAxolotlMessageHeader { private final int recipientDeviceId; private final byte[] content; public XmppAxolotlMessageHeader(int deviceId, byte[] content) { this.recipientDeviceId = deviceId; this.content = content; } public XmppAxolotlMessageHeader(Element header) { if("header".equals(header.getName())) { this.recipientDeviceId = Integer.parseInt(header.getAttribute("rid")); this.content = Base64.decode(header.getContent(),Base64.DEFAULT); } else { throw new IllegalArgumentException("Argument not a
Element!"); } } public int getRecipientDeviceId() { return recipientDeviceId; } public byte[] getContents() { return content; } public Element toXml() { Element headerElement = new Element("header"); // TODO: generate XML headerElement.setAttribute("rid", getRecipientDeviceId()); headerElement.setContent(Base64.encodeToString(getContents(), Base64.DEFAULT)); return headerElement; } } public static class XmppAxolotlPlaintextMessage { private final AxolotlService.XmppAxolotlSession session; private final String plaintext; public XmppAxolotlPlaintextMessage(AxolotlService.XmppAxolotlSession session, String plaintext) { this.session = session; this.plaintext = plaintext; } public String getPlaintext() { return plaintext; } } public XmppAxolotlMessage(Contact contact, Element axolotlMessage) { this.contact = contact; this.sourceDeviceId = Integer.parseInt(axolotlMessage.getAttribute("id")); this.headers = new HashSet<>(); for(Element child:axolotlMessage.getChildren()) { switch(child.getName()) { case "header": headers.add(new XmppAxolotlMessageHeader(child)); break; case "message": iv = Base64.decode(child.getAttribute("iv"),Base64.DEFAULT); ciphertext = Base64.decode(child.getContent(),Base64.DEFAULT); break; default: break; } } } public XmppAxolotlMessage(Contact contact, int sourceDeviceId, String plaintext) { this.contact = contact; this.sourceDeviceId = sourceDeviceId; this.headers = new HashSet<>(); this.encrypt(plaintext); } private void encrypt(String plaintext) { try { KeyGenerator generator = KeyGenerator.getInstance("AES"); generator.init(128); SecretKey secretKey = generator.generateKey(); Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding"); cipher.init(Cipher.ENCRYPT_MODE, secretKey); this.innerKey = secretKey.getEncoded(); this.iv = cipher.getIV(); this.ciphertext = cipher.doFinal(plaintext.getBytes()); } catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IllegalBlockSizeException | BadPaddingException e) { } } public Contact getContact() { return this.contact; } public int getSenderDeviceId() { return sourceDeviceId; } public byte[] getCiphertext() { return ciphertext; } public Set getHeaders() { return headers; } public void addHeader(XmppAxolotlMessageHeader header) { headers.add(header); } public byte[] getInnerKey(){ return innerKey; } public byte[] getIV() { return this.iv; } public Element toXml() { // TODO: generate outer XML, add in header XML Element message= new Element("axolotl_message", AxolotlService.PEP_PREFIX); message.setAttribute("id", sourceDeviceId); for(XmppAxolotlMessageHeader header: headers) { message.addChild(header.toXml()); } Element payload = message.addChild("message"); payload.setAttribute("iv",Base64.encodeToString(iv, Base64.DEFAULT)); payload.setContent(Base64.encodeToString(ciphertext,Base64.DEFAULT)); return message; } public XmppAxolotlPlaintextMessage decrypt(AxolotlService.XmppAxolotlSession session, byte[] key) { XmppAxolotlPlaintextMessage plaintextMessage = null; try { Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding"); SecretKeySpec keySpec = new SecretKeySpec(key, "AES"); IvParameterSpec ivSpec = new IvParameterSpec(iv); cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec); String plaintext = new String(cipher.doFinal(ciphertext)); plaintextMessage = new XmppAxolotlPlaintextMessage(session, plaintext); } catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | InvalidAlgorithmParameterException | IllegalBlockSizeException | BadPaddingException e) { throw new AssertionError(e); } return plaintextMessage; } }