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/*
* Copyright (C) 2023 MURENA SAS
* Copyright (C) 2022 E FOUNDATION
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package foundation.e.advancedprivacy.trackers.service
import android.net.LocalServerSocket
import android.system.ErrnoException
import android.system.Os
import android.system.OsConstants
import foundation.e.advancedprivacy.core.utils.runSuspendCatching
import foundation.e.advancedprivacy.trackers.domain.usecases.FilterHostnameUseCase
import kotlinx.coroutines.CancellationException
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.Job
import kotlinx.coroutines.isActive
import kotlinx.coroutines.launch
import timber.log.Timber
import java.io.BufferedReader
import java.io.InputStreamReader
import java.io.PrintWriter
class DNSBlocker(
val filterHostnameUseCase: FilterHostnameUseCase
) {
private var resolverReceiver: LocalServerSocket? = null
companion object {
private const val SOCKET_NAME = "foundation.e.advancedprivacy"
}
private fun closeSocket() {
// Known bug and workaround that LocalServerSocket::close is not working well
// https://issuetracker.google.com/issues/36945762
if (resolverReceiver != null) {
try {
Os.shutdown(resolverReceiver!!.fileDescriptor, OsConstants.SHUT_RDWR)
resolverReceiver!!.close()
resolverReceiver = null
} catch (e: ErrnoException) {
if (e.errno != OsConstants.EBADF) {
Timber.w("Socket already closed")
} else {
Timber.e(e, "Exception: cannot close DNS port on stop $SOCKET_NAME !")
}
} catch (e: Exception) {
Timber.e(e, "Exception: cannot close DNS port on stop $SOCKET_NAME !")
}
}
}
fun listenJob(scope: CoroutineScope): Job = scope.launch(Dispatchers.IO) {
val resolverReceiver = runSuspendCatching {
LocalServerSocket(SOCKET_NAME)
}.getOrElse {
Timber.e(it, "Exception: cannot open DNS port on $SOCKET_NAME")
return@launch
}
this@DNSBlocker.resolverReceiver = resolverReceiver
Timber.d("DNSFilterProxy running on port $SOCKET_NAME")
while (isActive) {
runSuspendCatching {
val socket = resolverReceiver.accept()
val reader = BufferedReader(InputStreamReader(socket.inputStream))
val line = reader.readLine()
val params = line.split(",").toTypedArray()
val output = socket.outputStream
val writer = PrintWriter(output, true)
val domainName = params[0]
val appUid = params[1].toInt()
if (filterHostnameUseCase.shouldBlock(domainName, appUid)) {
writer.println("block")
} else {
writer.println("pass")
}
socket.close()
}.onFailure {
if (it is CancellationException) {
closeSocket()
throw it
} else {
Timber.w(it, "Exception while listening DNS resolver")
}
}
}
}
}
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