public async Task decryptOmemoEncryptedMessageAsync(OmemoEncryptedMessage msg, bool trustedKeysOnly)
{
XMPPAccount account = CONNECTION.account;
OmemoProtocolAddress receiverAddress = new OmemoProtocolAddress(account.getBareJid(), account.omemoDeviceId);
// Try to decrypt the message, in case no exception occurred, everything went fine:
OmemoDecryptionContext decryptCtx = new OmemoDecryptionContext(receiverAddress, account.omemoIdentityKey, account.omemoSignedPreKey, account.OMEMO_PRE_KEYS, trustedKeysOnly, OMEMO_STORAGE);
msg.decrypt(decryptCtx);
Debug.Assert(!msg.ENCRYPTED);
Logger.Debug("Successfully decrypted an " + nameof(OmemoEncryptedMessage) + " for '" + receiverAddress.BARE_JID + "'.");
// Republish bundle information in case the message is a key exchange message and used a PreKey:
if (decryptCtx.keyExchange)
{
Logger.Info("Received a OMEMO key exchange message. Republishing bundle for '" + receiverAddress.BARE_JID + "'...");
PreKeyModel newPreKey = decryptCtx.STORAGE.ReplaceOmemoPreKey(decryptCtx.usedPreKey);
account.OMEMO_PRE_KEYS.Remove(decryptCtx.usedPreKey);
account.OMEMO_PRE_KEYS.Add(newPreKey);
await announceBundleInfoAsync();
Logger.Info("Bundle for '" + receiverAddress.BARE_JID + "' republished.");
}
// Reply with an empty message to confirm the successful key exchange:
// TODO: This is no good way, since there it would be possible to stalk people without them knowing.
}
/// <summary>
/// Generates a new Ed25519 <see cref="SignedPreKeyModel"/> and returns it.
/// </summary>
/// <param name="id">The id of the <see cref="SignedPreKeyModel"/>.</param>
/// <param name="identiyKey">The private part of an <see cref="IdentityKeyPairModel"/> used for signing.</param>
public static SignedPreKeyModel GenerateSignedPreKey(uint id, ECPrivKeyModel identiyKey)
{
PreKeyModel preKey = GeneratePreKey(id);
byte[] signature = Ed25519.Sign(preKey.pubKey.key, identiyKey.key);
return(new SignedPreKeyModel(preKey, signature));
}
/// <summary>
/// Generates the signature of the given <paramref name="preKey"/> and returns it.
/// </summary>
/// <param name="preKey">The <see cref="PreKeyModel"/> that should be signed.</param>
/// <param name="identiyKey">The private Key used for signing the given <paramref name="preKey"/>.</param>
/// <returns>The signature of the given <paramref name="preKey"/>.</returns>
public static byte[] SignPreKey(PreKeyModel preKey, ECPrivKeyModel identiyKey)
{
byte[] pubKey = preKey.pubKey.ToByteArrayWithPrefix();
byte[] signature = new byte[Ed25519.SignatureSize];
Ed25519.Sign(identiyKey.key, 0, pubKey, 0, pubKey.Length, signature, 0);
return(signature);
}
public PreKeyModel ReplaceOmemoPreKey(PreKeyModel preKey)
{
using (MainDbContext ctx = new MainDbContext())
{
// Remove the old key:
dbAccount.omemoInfo.preKeys.Remove(preKey);
preKey.Remove(ctx, true);
// Generate a new one:
PreKeyModel newPreKey = KeyHelper.GeneratePreKey(dbAccount.omemoInfo.maxPreKeyId++);
dbAccount.omemoInfo.preKeys.Add(newPreKey);
dbAccount.omemoInfo.bundleInfoAnnounced = false;
// Store everything in the DB:
ctx.Add(newPreKey);
ctx.Update(dbAccount.omemoInfo);
return(newPreKey);
}
}
public async Task decryptOmemoEncryptedMessageAsync(OmemoEncryptedMessage msg, bool trustedKeysOnly)
{
XMPPAccount account = CONNECTION.account;
OmemoProtocolAddress receiverAddress = new OmemoProtocolAddress(account.getBareJid(), account.omemoDeviceId);
// Try to decrypt the message, in case no exception occurred, everything went fine:
OmemoDecryptionContext decryptCtx = new OmemoDecryptionContext(receiverAddress, account.omemoIdentityKey, account.omemoSignedPreKey, account.OMEMO_PRE_KEYS, trustedKeysOnly, OMEMO_STORAGE);
msg.decrypt(decryptCtx);
Debug.Assert(!msg.ENCRYPTED);
Logger.Debug("Successfully decrypted an " + nameof(OmemoEncryptedMessage) + " for '" + receiverAddress.BARE_JID + "'.");
// Republish bundle information in case the message is a key exchange message and used a PreKey:
if (decryptCtx.keyExchange)
{
Logger.Info("Received a OMEMO key exchange message. Republishing bundle for '" + receiverAddress.BARE_JID + "'...");
PreKeyModel newPreKey = decryptCtx.STORAGE.ReplaceOmemoPreKey(decryptCtx.usedPreKey);
account.OMEMO_PRE_KEYS.Remove(decryptCtx.usedPreKey);
account.OMEMO_PRE_KEYS.Add(newPreKey);
await announceBundleInfoAsync();
Logger.Info("Bundle for '" + receiverAddress.BARE_JID + "' republished.");
// Reply with an empty message to confirm the successful key exchange:
// TODO: This is no good way, since there it would be possible to stalk people without them knowing.
OmemoEncryptedMessage reply = new OmemoEncryptedMessage(msg.getTo(), msg.getFrom(), null, msg.TYPE, false);
OmemoDeviceGroup deviceGroup = new OmemoDeviceGroup(decryptCtx.senderAddress.BARE_JID);
deviceGroup.SESSIONS.Add(decryptCtx.senderAddress.DEVICE_ID, decryptCtx.session);
try
{
reply.encrypt(CONNECTION.account.omemoDeviceId, CONNECTION.account.omemoIdentityKey, OMEMO_STORAGE, new List <OmemoDeviceGroup> {
deviceGroup
});
await CONNECTION.SendAsync(reply);
}
catch (Exception e)
{
Logger.Error("[OMEMO HELPER] Failed to encrypt and the empty OMEMO message reply with: ", e);
}
Logger.Info($"Send an empty OMEMO message to confirm the successful key exchange with '{msg.getFrom()}'.");
}
}
public PreKeyModel ReplaceOmemoPreKey(PreKeyModel preKey)
{
// Not relevant for us
return(preKey);
}