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better handling of discord-spec rtp packets
Signed-off-by: Lost <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,84 @@ | ||
| package dev.kord.voice.rtp | ||
|
|
||
| import dev.kord.common.annotation.KordVoice | ||
| import dev.kord.voice.XSalsa20Poly1305Codec | ||
| import io.ktor.utils.io.core.* | ||
| import okio.Buffer | ||
|
|
||
| /** | ||
| * A guestimated list of known Discord RTP payloads. | ||
| */ | ||
| sealed class PayloadType(val value: Byte) { | ||
| object Alive: PayloadType(0x37.toByte()) | ||
| object Audio: PayloadType(0x78.toByte()) | ||
| class Unknown(value: Byte): PayloadType(value) | ||
|
|
||
| companion object { | ||
| fun from(value: Byte) = when(value) { | ||
| 0x37.toByte() -> Alive | ||
| 0x78.toByte() -> Audio | ||
| else -> Unknown(value) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| @OptIn(ExperimentalUnsignedTypes::class) | ||
| @KordVoice | ||
| sealed class AudioPacket private constructor(internal val packet: RTPPacket) { | ||
| val sequence: UShort = packet.sequence | ||
| val timestamp: UInt = packet.timestamp | ||
| val ssrc: UInt = packet.ssrc | ||
| val payload: ByteArray = packet.payload | ||
| val payloadType: PayloadType = PayloadType.from(packet.payloadType) | ||
|
|
||
| class EncryptedPacket internal constructor( | ||
| packet: RTPPacket, | ||
| ) : AudioPacket(packet) { | ||
| fun decrypt(key: ByteArray): DecryptedPacket { | ||
| val nonce = ByteArray(NONCE_LENGTH) | ||
| packet.asByteArray().copyInto(nonce, 0, 0, RTP_HEADER_LENGTH) | ||
| val decrypted = XSalsa20Poly1305Codec.decrypt(payload, key, nonce) ?: error("fuck me") | ||
| return DecryptedPacket(packet.copy(payload = decrypted)) | ||
| } | ||
| } | ||
|
|
||
| fun asByteReadPacket() = ByteReadPacket(packet.asByteArray()) | ||
|
|
||
| class DecryptedPacket internal constructor( | ||
| packet: RTPPacket, | ||
| ) : AudioPacket(packet) { | ||
| fun encrypt(key: ByteArray): EncryptedPacket { | ||
| val nonce = ByteArray(NONCE_LENGTH) | ||
| packet.asByteArray().copyInto(nonce, 0, 0, RTP_HEADER_LENGTH) | ||
| val encrypted = XSalsa20Poly1305Codec.encrypt(payload, key, nonce) | ||
| return EncryptedPacket(packet.copy(payload = encrypted)) | ||
| } | ||
|
|
||
| @PublishedApi | ||
| internal companion object { | ||
| fun create( | ||
| sequence: UShort, | ||
| timestamp: UInt, | ||
| ssrc: UInt, | ||
| decryptedData: ByteArray | ||
| ): DecryptedPacket = DecryptedPacket( | ||
| RTPPacket(ssrc, timestamp, sequence, PayloadType.Audio.value, decryptedData) | ||
| ) | ||
| } | ||
| } | ||
|
|
||
| companion object { | ||
| private const val NONCE_LENGTH = 24 | ||
| private const val RTP_HEADER_LENGTH = 12 | ||
|
|
||
| @OptIn(ExperimentalStdlibApi::class) | ||
| fun encryptedFrom(data: ByteReadPacket): EncryptedPacket? { | ||
| return try { | ||
| val packet = RTPPacket.fromBytes(Buffer().write(data.copy().readBytes())) | ||
| EncryptedPacket(packet) | ||
| } catch(e: Exception) { | ||
| null | ||
| } | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,157 @@ | ||
| package dev.kord.voice.rtp | ||
|
|
||
| import okio.Buffer | ||
| import kotlin.experimental.and | ||
|
|
||
| /** | ||
| * Originally from [this github library](https://github.com/vidtec/rtp-packet/blob/0b54fdeab5666089215b0074c64a6735b8937f8d/src/main/java/org/vidtec/rfc3550/rtp/RTPPacket.java). | ||
| * | ||
| * Ported to Kotlin. | ||
| * | ||
| * Contains modifications to support RTP packets from Discord as they do not adhere to the standard RTP spec. | ||
| * | ||
| * Some changes include | ||
| * - Timestamps are stored as UInt (4 bytes) not long. | ||
| * - Sequences are stored as UShort (2 bytes) not long. | ||
| * - Payload Types are stored as UByte (1 byte) not short. | ||
| * - SSRCs are stored as UInt (4 bytes) not long. | ||
| * - And most notably, the extension header is not exactly after the RTP header. Discord instead encrypts it along with the payload... | ||
| */ | ||
| @Suppress("ArrayInDataClass") | ||
| @OptIn(ExperimentalUnsignedTypes::class) | ||
| internal data class RTPPacket( | ||
| val paddingBytes: UByte, | ||
| val payloadType: Byte, | ||
| val sequence: UShort, | ||
| val timestamp: UInt, | ||
| val ssrc: UInt, | ||
| val csrcIdentifiers: UIntArray, | ||
| val hasMarker: Boolean, | ||
| val hasExtension: Boolean, | ||
| val payload: ByteArray, | ||
| ) { | ||
| companion object { | ||
| const val VERSION = 2 | ||
|
|
||
| fun fromBytes(buffer: Buffer) = with(buffer) { | ||
| val initialLength = size | ||
|
|
||
| require(initialLength > 13) { "packet too short" } | ||
|
|
||
| /* | ||
| * first byte | bit table | ||
| * 0 = version | ||
| * 1 = padding bit | ||
| * 2 = extension bit | ||
| * 3-7 = csrc count | ||
| */ | ||
| val paddingBytes: UByte | ||
| val hasExtension: Boolean | ||
| val csrcCount: Byte | ||
| with(readByte()) { | ||
| require(((toInt() and 0xC0) == VERSION shl 6)) { "invalid version" } | ||
|
|
||
| paddingBytes = if (((toInt() and 0x20) == 0x20)) buffer[initialLength - 1].toUByte() else 0u; | ||
| hasExtension = (toInt() and 0x10) == 0x10 | ||
| csrcCount = toByte() and 0x0F | ||
| } | ||
|
|
||
| /* | ||
| * second byte | bit table | ||
| * 0 = marker | ||
| * 1-7 = payload type | ||
| */ | ||
| val marker: Boolean | ||
| val payloadType: Byte | ||
| with(readByte()) { | ||
| marker = (this and 0x80.toByte()) == 0x80.toByte() | ||
| payloadType = this and 0x7F | ||
| } | ||
|
|
||
| val sequence = readShort().toUShort() | ||
| val timestamp = readInt().toUInt() | ||
| val ssrc = readInt().toUInt() | ||
|
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| // each csrc takes up 4 bytes, plus more data is required | ||
| require(size > csrcCount * 4 + 1) { "packet too short" } | ||
| val csrcIdentifiers = UIntArray(csrcCount.toInt()) { readInt().toUInt() } | ||
|
|
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| val payload = readByteArray().apply { copyOfRange(0, size - paddingBytes.toInt()) } | ||
|
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||
| RTPPacket( | ||
| paddingBytes, | ||
| payloadType, | ||
| sequence, | ||
| timestamp, | ||
| ssrc, | ||
| csrcIdentifiers, | ||
| marker, | ||
| hasExtension, | ||
| payload | ||
| ) | ||
| } | ||
| } | ||
|
|
||
| init { | ||
| require(payloadType < 127 || payloadType > 0) { "invalid payload type" } | ||
| require(payload.isNotEmpty()) { "invalid payload" } | ||
| } | ||
|
|
||
| private val header = with(Buffer()) { | ||
| val hasPadding = if (paddingBytes > 0u) 0x20 else 0x00 | ||
| val hasExtension = if (hasExtension) 0x10 else 0x0 | ||
| writeByte((VERSION shl 6) or (hasPadding) or (hasExtension) or 0) | ||
| writeByte(payloadType.toInt()) | ||
| writeShort(sequence.toInt()) | ||
| writeInt(timestamp.toInt()) | ||
| writeInt(ssrc.toInt()) | ||
|
|
||
| readByteArray() | ||
| } | ||
|
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| fun asByteArray() = with(Buffer()) { | ||
| write(header) | ||
| write(payload) | ||
|
|
||
| if (paddingBytes > 0u) { | ||
| write(ByteArray(paddingBytes.toInt() - 1) { 0x0 }) | ||
| writeByte(paddingBytes.toInt()) | ||
| } | ||
|
|
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| buffer.readByteArray() | ||
| } | ||
|
|
||
| class Builder( | ||
| var ssrc: UInt, | ||
| var timestamp: UInt, | ||
| var sequence: UShort, | ||
| var payloadType: Byte, | ||
| var payload: ByteArray | ||
| ) { | ||
| var marker: Boolean = false | ||
| var paddingBytes: UByte = 0u | ||
| var hasExtension: Boolean = false | ||
| var csrcIdentifiers: UIntArray = uintArrayOf() | ||
|
|
||
| fun build() = RTPPacket( | ||
| paddingBytes, | ||
| payloadType, | ||
| sequence, | ||
| timestamp, | ||
| ssrc, | ||
| csrcIdentifiers, | ||
| marker, | ||
| hasExtension, | ||
| payload | ||
| ) | ||
| } | ||
| } | ||
|
|
||
| internal fun RTPPacket( | ||
| ssrc: UInt, | ||
| timestamp: UInt, | ||
| sequence: UShort, | ||
| payloadType: Byte, | ||
| payload: ByteArray, | ||
| builder: RTPPacket.Builder.() -> Unit = {} | ||
| ) = RTPPacket.Builder(ssrc, timestamp, sequence, payloadType, payload).apply(builder).build() |
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