adding srt aes encryption

library/src/main/java/com/pedro/library/util/streamclient/SrtStreamClient.kt

@@ -1,6 +1,7 @@
 package com.pedro.library.util.streamclient
 
 import com.pedro.srt.srt.SrtClient
+import com.pedro.srt.srt.packets.control.handshake.EncryptionType
 
 /**
  * Created by pedro on 12/10/23.
@@ -10,6 +11,13 @@ class SrtStreamClient(
   streamClientListener: StreamClientListener?
 ): StreamBaseClient(streamClientListener) {
 
+  /**
+   * Set passphrase for encrypt. Use empty value to disable it.
+   */
+  fun setPassphrase(passphrase: String, type: EncryptionType) {
+    srtClient.setPassphrase(passphrase, type)
+  }
+
   override fun setAuthorization(user: String?, password: String?) {
     srtClient.setAuthorization(user, password)
   }

srt/src/main/java/com/pedro/srt/srt/CommandsManager.kt

@@ -22,8 +22,10 @@ import com.pedro.srt.srt.packets.DataPacket
 import com.pedro.srt.srt.packets.SrtPacket
 import com.pedro.srt.srt.packets.control.Ack2
 import com.pedro.srt.srt.packets.control.Shutdown
+import com.pedro.srt.srt.packets.control.handshake.EncryptionType
 import com.pedro.srt.srt.packets.control.handshake.Handshake
 import com.pedro.srt.utils.Constants
+import com.pedro.srt.utils.EncryptionUtil
 import com.pedro.srt.utils.SrtSocket
 import com.pedro.srt.utils.TimeUtils
 import kotlinx.coroutines.sync.Mutex
@@ -51,6 +53,13 @@ class CommandsManager {
   var host = ""
   //Avoid write a packet in middle of other.
   private val writeSync = Mutex(locked = false)
+  private var encryptor: EncryptionUtil? = null
+
+  fun setPassphrase(passphrase: String, type: EncryptionType) {
+    encryptor = if (type == EncryptionType.AES192) throw IllegalArgumentException("AES_192 is unsupported in Android, use AES128 or AES256")
+    else if (passphrase.isEmpty()) null
+    else EncryptionUtil(type, passphrase)
+  }
 
   fun loadStartTs() {
     startTS = TimeUtils.getCurrentTimeMicro()
@@ -63,6 +72,7 @@ class CommandsManager {
   @Throws(IOException::class)
   suspend fun writeHandshake(socket: SrtSocket?, handshake: Handshake = Handshake()) {
     writeSync.withLock {
+      handshake.encryption = encryptor?.type ?: EncryptionType.NONE
       handshake.initialPacketSequence = sequenceNumber
       handshake.ipAddress = host
       handshake.write(getTs(), 0)
@@ -91,7 +101,7 @@ class CommandsManager {
         sequenceNumber = sequenceNumber++,
         packetPosition = packet.packetPosition,
         messageNumber = messageNumber++,
-        payload = packet.buffer,
+        payload = encryptor?.encrypt(packet.buffer) ?: packet.buffer,
         ts = getTs(),
         socketId = socketId
       )

srt/src/main/java/com/pedro/srt/srt/SrtClient.kt

@@ -30,6 +30,7 @@ import com.pedro.srt.srt.packets.control.KeepAlive
 import com.pedro.srt.srt.packets.control.Nak
 import com.pedro.srt.srt.packets.control.PeerError
 import com.pedro.srt.srt.packets.control.Shutdown
+import com.pedro.srt.srt.packets.control.handshake.EncryptionType
 import com.pedro.srt.srt.packets.control.handshake.ExtensionField
 import com.pedro.srt.srt.packets.control.handshake.Handshake
 import com.pedro.srt.srt.packets.control.handshake.HandshakeType
@@ -98,6 +99,16 @@ class SrtClient(private val connectCheckerSrt: ConnectCheckerSrt) {
     TODO("unimplemented")
   }
 
+  /**
+   * Set passphrase for encrypt. Use empty value to disable it.
+   */
+  fun setPassphrase(passphrase: String, type: EncryptionType) {
+    if (passphrase.length < 10 || passphrase.length > 79) {
+      throw IllegalArgumentException("passphrase must between 10 and 79 length")
+    }
+    commandsManager.setPassphrase(passphrase, type)
+  }
+
   /**
    * Must be called before connect
    */

srt/src/main/java/com/pedro/srt/utils/EncryptionUtil.kt

@@ -0,0 +1,45 @@
+package com.pedro.srt.utils
+
+import android.util.Log
+import com.pedro.srt.srt.packets.control.handshake.EncryptionType
+import java.security.SecureRandom
+import javax.crypto.Cipher
+import javax.crypto.SecretKeyFactory
+import javax.crypto.spec.PBEKeySpec
+
+/**
+ * Created by pedro on 12/11/23.
+ * Need API 26+
+ *
+ */
+class EncryptionUtil(val type: EncryptionType, passphrase: String) {
+
+  private val cipher: Cipher
+  private val iterations = 10_000 //reduce the number for performance but this make it less secure
+
+  init {
+    val keyLength = when (type) {
+      EncryptionType.NONE -> 0
+      EncryptionType.AES128 -> 128
+      EncryptionType.AES192 -> 192
+      EncryptionType.AES256 -> 256
+    }
+    cipher = Cipher.getInstance("AES_$keyLength/CBC/PKCS5PADDING")
+    val salt = ByteArray(128)
+    val secureRandom = SecureRandom()
+    secureRandom.nextBytes(salt)
+
+    val spec = PBEKeySpec(passphrase.toCharArray(), salt, iterations, keyLength)
+    val factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1")
+    val key = factory.generateSecret(spec)
+    cipher.init(Cipher.ENCRYPT_MODE, key)
+  }
+
+  fun encrypt(bytes: ByteArray): ByteArray {
+    return cipher.doFinal(bytes)
+  }
+
+  fun encrypt(bytes: ByteArray, offset: Int, length: Int): ByteArray {
+    return cipher.doFinal(bytes, offset, length)
+  }
+}