Anton Chekulaev
4 years ago
parent
9002606917
commit
e33b8a5fa2
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package org.thoughtcrime.securesms.loki.api
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import android.content.Context
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import android.util.Log
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import com.goterl.lazycode.lazysodium.LazySodiumAndroid
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import com.goterl.lazycode.lazysodium.SodiumAndroid
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import com.goterl.lazycode.lazysodium.interfaces.Box
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import com.goterl.lazycode.lazysodium.interfaces.Sign
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import org.session.libsignal.libsignal.util.Hex
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import org.session.libsignal.service.api.messages.SignalServiceEnvelope
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import org.session.libsignal.service.internal.push.SignalServiceProtos.Envelope.Type.CLOSED_GROUP_CIPHERTEXT_VALUE
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import org.session.libsignal.service.internal.push.SignalServiceProtos.Envelope.Type.UNIDENTIFIED_SENDER_VALUE
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import org.session.libsignal.service.loki.api.crypto.SessionProtocol
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import org.session.libsignal.service.loki.utilities.removing05PrefixIfNeeded
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import org.session.libsignal.service.loki.utilities.toHexString
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import org.thoughtcrime.securesms.crypto.IdentityKeyUtil
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import org.thoughtcrime.securesms.database.DatabaseFactory
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import org.thoughtcrime.securesms.loki.utilities.KeyPairUtilities
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import org.thoughtcrime.securesms.util.TextSecurePreferences
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class SessionProtocolImpl(private val context: Context) : SessionProtocol {
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override fun encrypt(plaintext: ByteArray, recipientHexEncodedX25519PublicKey: String): ByteArray {
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val userED25519KeyPair = KeyPairUtilities.getUserED25519KeyPair(context) ?: throw SessionProtocol.Exception.NoUserED25519KeyPair
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val recipientX25519PublicKey = Hex.fromStringCondensed(recipientHexEncodedX25519PublicKey.removing05PrefixIfNeeded())
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val sodium = LazySodiumAndroid(SodiumAndroid())
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val verificationData = plaintext + userED25519KeyPair.publicKey.asBytes + recipientX25519PublicKey
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val signature = ByteArray(Sign.BYTES)
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try {
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sodium.cryptoSignDetached(signature, verificationData, verificationData.size.toLong(), userED25519KeyPair.secretKey.asBytes)
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} catch (exception: Exception) {
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Log.d("Loki", "Couldn't sign message due to error: $exception.")
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throw SessionProtocol.Exception.SigningFailed
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}
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val plaintextWithMetadata = plaintext + userED25519KeyPair.publicKey.asBytes + signature
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val ciphertext = ByteArray(plaintextWithMetadata.size + Box.SEALBYTES)
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try {
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sodium.cryptoBoxSeal(ciphertext, plaintextWithMetadata, plaintextWithMetadata.size.toLong(), recipientX25519PublicKey)
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} catch (exception: Exception) {
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Log.d("Loki", "Couldn't encrypt message due to error: $exception.")
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throw SessionProtocol.Exception.EncryptionFailed
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}
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return ciphertext
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}
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override fun decrypt(envelope: SignalServiceEnvelope): Pair<ByteArray, String> {
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val ciphertext = envelope.content ?: throw SessionProtocol.Exception.NoData
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val recipientX25519PrivateKey: ByteArray
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val recipientX25519PublicKey: ByteArray
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when (envelope.type) {
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UNIDENTIFIED_SENDER_VALUE -> {
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recipientX25519PrivateKey = IdentityKeyUtil.getIdentityKeyPair(context).privateKey.serialize()
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recipientX25519PublicKey = Hex.fromStringCondensed(TextSecurePreferences.getLocalNumber(context).removing05PrefixIfNeeded())
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}
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CLOSED_GROUP_CIPHERTEXT_VALUE -> {
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val hexEncodedGroupPublicKey = envelope.source
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val sskDB = DatabaseFactory.getSSKDatabase(context)
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if (!sskDB.isSSKBasedClosedGroup(hexEncodedGroupPublicKey)) { throw SessionProtocol.Exception.InvalidGroupPublicKey }
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val hexEncodedGroupPrivateKey = sskDB.getClosedGroupPrivateKey(hexEncodedGroupPublicKey) ?: throw SessionProtocol.Exception.NoGroupPrivateKey
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recipientX25519PrivateKey = Hex.fromStringCondensed(hexEncodedGroupPrivateKey)
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recipientX25519PublicKey = Hex.fromStringCondensed(hexEncodedGroupPublicKey.removing05PrefixIfNeeded())
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}
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else -> throw AssertionError()
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}
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val sodium = LazySodiumAndroid(SodiumAndroid())
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val signatureSize = Sign.BYTES
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val ed25519PublicKeySize = Sign.PUBLICKEYBYTES
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// 1. ) Decrypt the message
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val plaintextWithMetadata = ByteArray(ciphertext.size - Box.SEALBYTES)
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try {
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sodium.cryptoBoxSealOpen(plaintextWithMetadata, ciphertext, ciphertext.size.toLong(), recipientX25519PublicKey, recipientX25519PrivateKey)
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} catch (exception: Exception) {
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Log.d("Loki", "Couldn't decrypt message due to error: $exception.")
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throw SessionProtocol.Exception.DecryptionFailed
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}
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if (plaintextWithMetadata.size <= (signatureSize + ed25519PublicKeySize)) { throw SessionProtocol.Exception.DecryptionFailed }
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// 2. ) Get the message parts
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val signature = plaintextWithMetadata.sliceArray(plaintextWithMetadata.size - signatureSize until plaintextWithMetadata.size)
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val senderED25519PublicKey = plaintextWithMetadata.sliceArray(plaintextWithMetadata.size - (signatureSize + ed25519PublicKeySize) until plaintextWithMetadata.size - signatureSize)
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val plaintext = plaintextWithMetadata.sliceArray(0 until plaintextWithMetadata.size - (signatureSize + ed25519PublicKeySize))
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// 3. ) Verify the signature
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val verificationData = (plaintext + senderED25519PublicKey + recipientX25519PublicKey)
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try {
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val isValid = sodium.cryptoSignVerifyDetached(signature, verificationData, verificationData.size, senderED25519PublicKey)
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if (!isValid) { throw SessionProtocol.Exception.InvalidSignature }
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} catch (exception: Exception) {
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Log.d("Loki", "Couldn't verify message signature due to error: $exception.")
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throw SessionProtocol.Exception.InvalidSignature
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}
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// 4. ) Get the sender's X25519 public key
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val senderX25519PublicKey = ByteArray(Sign.CURVE25519_PUBLICKEYBYTES)
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sodium.convertPublicKeyEd25519ToCurve25519(senderX25519PublicKey, senderED25519PublicKey)
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return Pair(plaintext, "05" + senderX25519PublicKey.toHexString())
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}
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}
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@ -0,0 +1,40 @@
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package org.session.libsignal.service.loki.api.crypto
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import org.session.libsignal.service.api.messages.SignalServiceEnvelope
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interface SessionProtocol {
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sealed class Exception(val description: String) : kotlin.Exception(description) {
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// Encryption
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object NoUserED25519KeyPair : Exception("Couldn't find user ED25519 key pair.")
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object SigningFailed : Exception("Couldn't sign message.")
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object EncryptionFailed : Exception("Couldn't encrypt message.")
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// Decryption
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object NoData : Exception("Received an empty envelope.")
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object InvalidGroupPublicKey : Exception("Invalid group public key.")
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object NoGroupPrivateKey : Exception("Missing group private key.")
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object DecryptionFailed : Exception("Couldn't decrypt message.")
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object InvalidSignature : Exception("Invalid message signature.")
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}
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/**
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* Encrypts `plaintext` using the Session protocol for `hexEncodedX25519PublicKey`.
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*
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* @param plaintext the plaintext to encrypt. Must already be padded.
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* @param recipientHexEncodedX25519PublicKey the X25519 public key to encrypt for. Could be the Session ID of a user, or the public key of a closed group.
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*
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* @return the encrypted message.
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*/
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fun encrypt(plaintext: ByteArray, recipientHexEncodedX25519PublicKey: String): ByteArray
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/**
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* Decrypts `envelope.content` using the Session protocol. If the envelope type is `UNIDENTIFIED_SENDER` the message is assumed to be a one-to-one
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* message. If the envelope type is `CLOSED_GROUP_CIPHERTEXT` the message is assumed to be a closed group message. In the latter case `envelope.source`
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* must be set to the closed group's public key.
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*
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* @param envelope the envelope for which to decrypt the content.
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*
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* @return the padded plaintext.
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*/
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fun decrypt(envelope: SignalServiceEnvelope): Pair<ByteArray, String>
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}
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