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ble ltk: implement encryption and message parsing

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This commit is contained in:
Andrei Vereha 2021-02-27 20:45:01 +01:00
parent ddfbd2e7bd
commit ddb1c18349
6 changed files with 100 additions and 24 deletions
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5
omnipod-dash/src/main/java/info/nightscout/androidaps/plugins/pump/omnipod/dash/driver/comm/exceptions/CouldNotParseMessageException.kt Normal file
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@ -0,0 +1,5 @@
package info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.exceptions
import info.nightscout.androidaps.utils.extensions.toHex
class CouldNotParseMessageException(val payload: ByteArray): Exception("Could not parse message payload: ${payload.toHex()}")

5
omnipod-dash/src/main/java/info/nightscout/androidaps/plugins/pump/omnipod/dash/driver/comm/exceptions/MessageIOException.kt
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@ -1,3 +1,6 @@
package info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.exceptions
class MessageIOException(override val cause: Throwable) : Exception(cause)
class MessageIOException : Exception {
constructor(msg: String): super(msg)
constructor(cause: Throwable): super(cause)
}

38
omnipod-dash/src/main/java/info/nightscout/androidaps/plugins/pump/omnipod/dash/driver/comm/ltk/LTKExchanger.kt
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@ -1,9 +1,6 @@
package info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.ltk
import com.google.crypto.tink.mac.AesCmacKeyManager
import com.google.crypto.tink.proto.AesCmac
import com.google.crypto.tink.subtle.X25519
import info.nightscout.androidaps.logging.AAPSLogger
import info.nightscout.androidaps.logging.LTag
import info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.Id
@ -15,6 +12,8 @@ import info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.message.
import info.nightscout.androidaps.utils.extensions.hexStringToByteArray
import info.nightscout.androidaps.utils.extensions.toHex
import org.spongycastle.crypto.engines.AESEngine
import org.spongycastle.crypto.macs.CMac
import org.spongycastle.crypto.params.KeyParameter
import java.security.SecureRandom
internal class LTKExchanger(private val aapsLogger: AAPSLogger, private val msgIO: MessageIO) {
@ -30,7 +29,7 @@ internal class LTKExchanger(private val aapsLogger: AAPSLogger, private val msgI
private val controllerId = Id.fromInt(OmnipodDashBleManagerImpl.CONTROLLER_ID)
val nodeId = controllerId.increment()
private var seq: Byte = 1
private var ltk = ByteArray(0)
private var ltk = ByteArray(CMAC_SIZE)
private var noncePrefix = ByteArray(0)
init {
@ -98,7 +97,7 @@ internal class LTKExchanger(private val aapsLogger: AAPSLogger, private val msgI
val publicKey = X25519.publicFromPrivate(pdmPrivate)
val payload = StringLengthPrefixEncoding.formatKeys(
arrayOf("SPS1="),
arrayOf(publicKey + nonce),
arrayOf(publicKey + pdmNonce),
)
return PairMessage(
sequenceNumber = seq,
@ -111,7 +110,7 @@ internal class LTKExchanger(private val aapsLogger: AAPSLogger, private val msgI
private fun processSps1FromPod(msg: MessagePacket) {
aapsLogger.debug(LTag.PUMPBTCOMM, "Received SPS1 from pod: ${msg.payload.toHex()}")
if (msg.payload.size != 48) {
throw MessageIOException()
throw MessageIOException("Invalid payload size")
}
podPublic = msg.payload.copyOfRange(0, PUBLIC_KEY_SIZE)
podNonce = msg.payload.copyOfRange(PUBLIC_KEY_SIZE, PUBLIC_KEY_SIZE + NONCE_SIZE)
@ -144,19 +143,36 @@ internal class LTKExchanger(private val aapsLogger: AAPSLogger, private val msgI
fun generateKeys() {
val curveLTK = X25519.computeSharedSecret(pdmPrivate, podPublic)
aapsLogger.debug(LTag.PUMPBTCOMM, "LTK, donna key: ${curveLTK.toHex()}")
//first_key = data.pod_public[-4:] + data.pdm_public[-4:] + data.pod_nonce[-4:] + data.pdm_nonce[-4:]
val firstKey = podPublic.copyOfRange(podPublic.size-4, podPublic.size)
+ pdmPublic.copyOfRange(pdmPublic.size-4, pdmPublic.size)
+ podNonce.copyOfRange(podNonce.size-4, podNonce.size)
+ pdmNonce.copyOfRange(pdmNonce.size-4, pdmNonce.size)
//first_key = data.pod_public[-4:] + data.pdm_public[-4:] + data.pod_nonce[-4:] + data.pdm_nonce[-4:]
val firstKey = podPublic.copyOfRange(podPublic.size - 4, podPublic.size) +
pdmPublic.copyOfRange(pdmPublic.size - 4, pdmPublic.size)+
podNonce.copyOfRange(podNonce.size - 4, podNonce.size)+
pdmNonce.copyOfRange(pdmNonce.size - 4, pdmNonce.size)
aapsLogger.debug(LTag.PUMPBTCOMM, "LTK, first key: ${firstKey.toHex()}")
val aesEngine = AESEngine()
val intermediateMac = CMac(aesEngine)
intermediateMac.init(KeyParameter(firstKey))
intermediateMac.update(curveLTK, 0, curveLTK.size)
val intermediateKey = ByteArray(CMAC_SIZE)
intermediateMac.doFinal(intermediateKey, 0)
aapsLogger.debug(LTag.PUMPBTCOMM, "Intermediate key: ${intermediateKey.toHex()}")
val ltkMac = CMac(aesEngine)
ltkMac.init(KeyParameter(firstKey))
ltkMac.update(curveLTK, 0, curveLTK.size)
intermediateMac.doFinal(ltk, 0)
aapsLogger.debug(LTag.PUMPBTCOMM, "LTK: ${ltk.toHex()}")
}
companion object {
private val PUBLIC_KEY_SIZE = 32
private val NONCE_SIZE = 16
private val CONF_SIZE = 16
private val CMAC_SIZE = 16
private val GET_POD_STATUS_HEX_COMMAND = "ffc32dbd08030e0100008a" // TODO for now we are assuming this command is build out of constant parameters, use a proper command builder for that.
}
}

1
omnipod-dash/src/main/java/info/nightscout/androidaps/plugins/pump/omnipod/dash/driver/comm/message/MessageIO.kt
View file

@ -36,7 +36,6 @@ class MessageIO(private val aapsLogger: AAPSLogger, private val bleIO: BleIO) {
bleIO.flushIncomingQueues()
}
@kotlin.ExperimentalUnsignedTypes
fun receiveMessage(): MessagePacket {
val expectRTS = bleIO.receivePacket(CharacteristicType.CMD)
if (BleCommand(expectRTS) != BleCommandRTS()) {

58
omnipod-dash/src/main/java/info/nightscout/androidaps/plugins/pump/omnipod/dash/driver/comm/message/MessagePacket.kt
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@ -1,6 +1,7 @@
package info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.message
import info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.Id
import info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.exceptions.CouldNotParseMessageException
import java.nio.ByteBuffer
/***
@ -69,9 +70,56 @@ data class MessagePacket(
companion object {
private val MAGIC_PATTERN = "TW" // all messages start with this string
private val HEADER_SIZE = 16
fun parse(payload: ByteArray): MessagePacket {
TODO("implement message header parsing")
if (payload.size < HEADER_SIZE) {
throw CouldNotParseMessageException(payload)
}
if (payload.copyOfRange(0, 2).toString() != "TW") {
throw info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.exceptions.CouldNotParseMessageException(payload)
}
val f1 = Flag(payload[2].toInt())
val sas = f1.get(3) != 0
val tfs = f1.get(4) != 0
val version = ((f1.get(0) shl 2) or (f1.get(1) shl 1) or (f1.get(2) shl 0)).toShort()
val eqos = (f1.get(7) or (f1.get(6) shl 1) or (f1.get(5) shl 2)).toShort()
val f2 = Flag(payload[3].toInt())
val ack = f2.get(0) != 0
val priority = f2.get(1) != 0
val lastMessage = f2.get(2) != 0
val gateway = f2.get(3) != 0
val type = MessageType.byValue((f1.get(7) or (f1.get(6) shl 1) or (f1.get(5) shl 2) or (f1.get(4) shl 3)).toByte())
if (version.toInt() != 0) {
throw CouldNotParseMessageException(payload)
}
val sequenceNumber = payload[4]
val ackNumber = payload[5]
val size = (payload[6].toInt() shl 3) or (payload[7].toInt() ushr 5)
if (size + HEADER_SIZE > payload.size) {
throw CouldNotParseMessageException(payload)
}
val payloadEnd = 16 + size +
if (type == MessageType.ENCRYPTED) 8
else 0
return MessagePacket(
type = type,
ack = ack,
eqos = eqos,
priority = priority,
lastMessage = lastMessage,
gateway = gateway,
sas = sas,
tfs = tfs,
version = version,
sequenceNumber = payload[4],
ackNumber = payload[5],
source = Id(payload.copyOfRange(8, 12)),
destination = Id(payload.copyOfRange(12, 16)),
payload = payload.copyOfRange(16, payloadEnd),
)
}
}
}
@ -85,8 +133,12 @@ private class Flag(var value: Int = 0) {
value = value or mask
}
fun get(idx: Byte): Boolean {
fun get(idx: Byte): Int {
val mask = 1 shl (7 - idx)
return value and mask != 0
if (value and mask == 0) {
return 0
}
return 1
}
}

7
omnipod-dash/src/main/java/info/nightscout/androidaps/plugins/pump/omnipod/dash/driver/comm/message/PayloadJoiner.kt
View file

@ -11,7 +11,6 @@ import java.lang.Integer.min
import java.nio.ByteBuffer
import java.util.*
@ExperimentalUnsignedTypes
class PayloadJoiner(private val firstPacket: ByteArray) {
var oneExtra: Boolean = false
@ -31,7 +30,7 @@ class PayloadJoiner(private val firstPacket: ByteArray) {
throw IncorrectPacketException(0, firstPacket)
fullFragments == 0 -> {
crc = ByteBuffer.wrap(firstPacket.copyOfRange(2, 6)).int.toUInt().toLong()
crc = ByteBuffer.wrap(firstPacket.copyOfRange(2, 6)).int.toUnsignedLong()
val rest = firstPacket[6]
val end = min(rest + 7, BlePacket.MAX_LEN)
oneExtra = rest + 7 > end
@ -72,7 +71,7 @@ class PayloadJoiner(private val firstPacket: ByteArray) {
if (packet.size < LastBlePacket.HEADER_SIZE) {
throw IncorrectPacketException(idx.toByte(), packet)
}
crc = ByteBuffer.wrap(packet.copyOfRange(2, 6)).int.toUInt().toLong()
crc = ByteBuffer.wrap(packet.copyOfRange(2, 6)).int.toUnsignedLong()
val rest = packet[1].toInt()
val end = min(rest, BlePacket.MAX_LEN)
if (packet.size < end) {
@ -106,3 +105,5 @@ class PayloadJoiner(private val firstPacket: ByteArray) {
}
}
private fun Int.toUnsignedLong() = this.toLong() and 0xffffffffL