Merge pull request #48 from bobrofon/magisk-27-support

Magisk 27 support

app/src/main/java/ru/nsu/bobrofon/easysshfs/EasySSHFSActivity.kt

@@ -14,7 +14,6 @@ import androidx.appcompat.app.AppCompatActivity
 import androidx.core.content.ContextCompat
 import androidx.drawerlayout.widget.DrawerLayout
 import androidx.lifecycle.ViewModelProvider
-import com.topjohnwu.superuser.BusyBoxInstaller
 import com.topjohnwu.superuser.Shell
 import ru.nsu.bobrofon.easysshfs.log.LogFragment
 import ru.nsu.bobrofon.easysshfs.mountpointlist.MountPointsList
@@ -188,16 +187,11 @@ class EasySSHFSActivity : AppCompatActivity(), NavigationDrawerFragment.Navigati
         }
 
         fun initNewShell(): Shell {
-            return Shell.getShell()
+            return ShellBuilder.sharedShell()
         }
 
         init {
             Shell.enableVerboseLogging = BuildConfig.DEBUG
-            Shell.setDefaultBuilder(
-                Shell.Builder.create()
-                    .setFlags(Shell.FLAG_MOUNT_MASTER)
-                    .setInitializers(BusyBoxInstaller::class::java.get())
-            )
         }
     }
 

app/src/main/java/ru/nsu/bobrofon/easysshfs/ShellBuilder.kt

@@ -0,0 +1,87 @@
+package ru.nsu.bobrofon.easysshfs
+
+import android.util.Log
+import com.topjohnwu.superuser.BusyBoxInstaller
+import com.topjohnwu.superuser.Shell
+import com.topjohnwu.superuser.Shell.Builder
+import ru.nsu.bobrofon.easysshfs.log.AppLog
+import java.lang.ref.WeakReference
+
+object ShellBuilder {
+    private const val TAG = "ShellBuilder"
+
+    private var sharedShell = WeakReference<Shell?>(null)
+
+    @Synchronized
+    fun sharedShell(): Shell {
+        val oldShell = sharedShell.get()
+        if (oldShell == null) {
+            Log.i(TAG, "create new shared shell")
+            val newShell = build()
+            sharedShell = WeakReference(newShell)
+            return newShell
+        }
+        return oldShell
+    }
+
+    private fun build(): Shell {
+        val builder = Builder.create()
+            .setInitializers(BusyBoxInstaller::class::java.get())
+
+        return if (isMagiskV27x()) {
+            // TODO: remove logging after the following release (or maybe a few releases)
+            AppLog.instance().addMessage("Magisk SU v27+ detected")
+            // '--master-mount' actually spawns shell in an isolated mount namespace
+            // try to run shell in an init process namespace instead
+            // TODO: use Zygote namespace instead
+            builder.build("su", "-t", "1")
+        } else {
+            // assume that 'su' implementation supports '--master-mount' option
+            // (SuperSu or Magisk until v27.0)
+            builder.setFlags(Shell.FLAG_MOUNT_MASTER)
+            builder.build()
+        }
+    }
+
+    private fun isMagiskV27x(): Boolean {
+        val sh = Builder.create()
+            .setInitializers(BusyBoxInstaller::class::java.get())
+            .setFlags(Shell.FLAG_NON_ROOT_SHELL)
+            .build()
+
+        // The result should be something like this:
+        //   $ su -v 2>/dev/null
+        //   27.0:MAGISKSU
+        //   $ echo $?
+        //   0
+        val displayVersionCmd = "su -v"
+        val verResult = sh.newJob().add(displayVersionCmd).to(arrayListOf()).exec()
+        if (!verResult.isSuccess) {
+            Log.d(TAG, "failed to exec '$displayVersionCmd' (exit with ${verResult.code})")
+            return false
+        }
+        if (verResult.out.isEmpty()) {
+            Log.d(TAG, "'$displayVersionCmd' output is empty")
+            return false
+        }
+
+        // 27.0:MAGISKSU
+        val match = Regex("(\\d+)\\.?.*:MAGISKSU").matchEntire(verResult.out[0])
+        if (match == null) {
+            Log.d(TAG, "Magisk SU version signature is not found in ${verResult.out}")
+            return false
+        }
+        Log.d(TAG, "detected Magisk SU version signature in ${verResult.out}")
+        val majorVerString = match.groupValues[1] // 0 is the whole match
+        val majorVer = try {
+            majorVerString.toInt()
+        } catch (e: NumberFormatException) {
+            AppLog.instance().addMessage("failed to parse Magisk SU version '$majorVerString'")
+            Log.w(TAG, "failed to parse '$majorVerString'", e)
+            return false
+        }
+
+        Log.d(TAG, "detected Magisk SU version $majorVer")
+        return majorVer >= 27
+    }
+}