Use bundled 'nsenter' instead of '--master-mount' option of 'su'

app/CMakeLists.txt

@@ -4,6 +4,7 @@ cmake_minimum_required(VERSION 3.10.2)
 # The project generates following files:
 #   * lib/${ANDROID_ABI}/libssh.so
 #   * lib/${ANDROID_ABI}/libsshfs.so
+#   * lib/${ANDROID_ABI}/libnsenter.so
 #   * lib/${ANDROID_ABI}/libstub.so
 project(assets LANGUAGES NONE)
 
@@ -19,7 +20,7 @@ add_subdirectory(../sshfs-static "${SSHFS_BINARY_DIR}")
 # TODO(bobrofon): report issue
 add_subdirectory(src/main/cpp)
 
-set(ASSETS_EXECUTABLES ssh sshfs)
+set(ASSETS_EXECUTABLES ssh sshfs nsenter)
 
 foreach (exe IN LISTS ASSETS_EXECUTABLES)
     set(src_path "${SSHFS_BINARY_DIR}/${exe}-static-${ANDROID_ABI}")

app/build.gradle

@@ -34,7 +34,7 @@ android {
 
         externalNativeBuild {
             cmake {
-                targets "ssh", "sshfs"
+                targets "ssh", "sshfs", "nsenter"
             }
         }
     }

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

@@ -1,10 +1,11 @@
 // SPDX-License-Identifier: MIT
 package ru.nsu.bobrofon.easysshfs
 
+import android.content.Context
 import android.util.Log
 import com.topjohnwu.superuser.Shell
 import com.topjohnwu.superuser.Shell.Builder
-import ru.nsu.bobrofon.easysshfs.log.AppLog
+import java.io.File
 import java.lang.ref.WeakReference
 
 object ShellBuilder {
@@ -24,60 +25,32 @@ object ShellBuilder {
         return oldShell
     }
 
-    private fun build(): Shell {
-        val builder = Builder.create()
 
-        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
+    class NsenterInitiallizer : Shell.Initializer() {
+        override fun onInit(context: Context, shell: Shell): Boolean {
+            val nsenter = File(context.filesDir.path, "nsenter")
             // 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()
+            val cmd = "${nsenter.path} -m -t 1"
+
+            val result =
+                shell.newJob().add(cmd).to(mutableListOf<String>(), mutableListOf<String>()).exec()
+            return if (result.isSuccess) {
+                Log.i(
+                    TAG,
+                    "'$cmd' succeed: code=${result.code} stdout=${result.out} stderr=${result.err}"
+                )
+                super.onInit(context, shell)
+            } else {
+                Log.w(
+                    TAG,
+                    "'$cmd' failed: code=${result.code} stdout=${result.out} stderr=${result.err}"
+                )
+                false
+            }
         }
     }
 
-    private fun isMagiskV27x(): Boolean {
-        val sh = Builder.create().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
+    private fun build(): Shell {
+        return Builder.create().setInitializers(NsenterInitiallizer::class.java).build()
     }
 }

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

@@ -29,6 +29,7 @@ class VersionUpdater(
         // directly use .so files, it will be not possible.
         makeLibrarySymlink("ssh", "ssh", lastVersion != currentVersion)
         makeLibrarySymlink("sshfs", "sshfs", lastVersion != currentVersion)
+        makeLibrarySymlink("nsenter", "nsenter", lastVersion != currentVersion)
 
         if (lastVersion < 9) {
             update02to03()

sshfs-static/CMakeLists.txt

@@ -4,6 +4,7 @@ cmake_minimum_required(VERSION 3.10.2)
 # The project generates following files:
 #   * ssh-static-${arch}
 #   * sshfs-static-${arch}
+#   * nsenter-static-${arch}
 project(sshfs-static LANGUAGES NONE)
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/Buildroot.cmake")
@@ -13,7 +14,7 @@ set(BUILDROOT_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/buildroot")
 include("Buildroot")
 
 set(SSHFS_STATIC_SUPPORTED_ARCHS armeabi-v7a arm64-v8a x86 x86_64)
-set(SSHFS_STATIC_EXECUTABLES ssh sshfs)
+set(SSHFS_STATIC_EXECUTABLES ssh sshfs nsenter)
 
 foreach(arch IN LISTS SSHFS_STATIC_SUPPORTED_ARCHS)
 	set(buildroot_sshfs buildroot-sshfs-static-${arch})

sshfs-static/configs/sshfs-static-arm64-v8a.config

@@ -1,6 +1,6 @@
 #
 # Automatically generated file; DO NOT EDIT.
-# Buildroot 2025.11.11-sshfs Configuration
+# Buildroot 2022.02.1 Configuration
 #
 BR2_HAVE_DOT_CONFIG=y
 BR2_HOST_GCC_AT_LEAST_4_9=y
@@ -222,7 +222,7 @@ BR2_PACKAGE_HAS_TOOLCHAIN_EXTERNAL=y
 BR2_PACKAGE_PROVIDES_TOOLCHAIN_EXTERNAL="toolchain-external-custom"
 BR2_TOOLCHAIN_EXTERNAL_PREFIX="$(ARCH)-buildroot-linux-musl"
 BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_ARCH_SUPPORTS=y
-BR2_TOOLCHAIN_EXTERNAL_URL="https://github.com/bobrofon/buildroot/releases/download/2022.04.17-musl-trusty/aarch64-buildroot-linux-musl.tar.xz"
+BR2_TOOLCHAIN_EXTERNAL_URL="https://github.com/bobrofon/buildroot/releases/download/2026.04.24-musl-trusty/aarch64-buildroot-linux-musl.tar.xz"
 BR2_TOOLCHAIN_EXTERNAL_REL_BIN_PATH="bin"
 BR2_TOOLCHAIN_EXTERNAL_CUSTOM_PREFIX="$(ARCH)-buildroot-linux-musl"
 # BR2_TOOLCHAIN_EXTERNAL_GCC_11 is not set
@@ -4342,7 +4342,82 @@ BR2_PACKAGE_SYSTEMD_BOOTCHART_ARCH_SUPPORTS=y
 #
 # unscd needs a glibc toolchain
 #
-# BR2_PACKAGE_UTIL_LINUX is not set
+BR2_PACKAGE_UTIL_LINUX=y
+# BR2_PACKAGE_UTIL_LINUX_LIBBLKID is not set
+# BR2_PACKAGE_UTIL_LINUX_LIBFDISK is not set
+# BR2_PACKAGE_UTIL_LINUX_LIBMOUNT is not set
+# BR2_PACKAGE_UTIL_LINUX_LIBSMARTCOLS is not set
+# BR2_PACKAGE_UTIL_LINUX_LIBUUID is not set
+# BR2_PACKAGE_UTIL_LINUX_BINARIES is not set
+# BR2_PACKAGE_UTIL_LINUX_AGETTY is not set
+# BR2_PACKAGE_UTIL_LINUX_BFS is not set
+# BR2_PACKAGE_UTIL_LINUX_CAL is not set
+
+#
+# chfn/chsh needs a toolchain w/ wchar, locale, dynamic library
+#
+# BR2_PACKAGE_UTIL_LINUX_CHMEM is not set
+# BR2_PACKAGE_UTIL_LINUX_CRAMFS is not set
+# BR2_PACKAGE_UTIL_LINUX_EJECT is not set
+# BR2_PACKAGE_UTIL_LINUX_FALLOCATE is not set
+# BR2_PACKAGE_UTIL_LINUX_FDFORMAT is not set
+# BR2_PACKAGE_UTIL_LINUX_FSCK is not set
+# BR2_PACKAGE_UTIL_LINUX_HARDLINK is not set
+# BR2_PACKAGE_UTIL_LINUX_HWCLOCK is not set
+# BR2_PACKAGE_UTIL_LINUX_IPCRM is not set
+# BR2_PACKAGE_UTIL_LINUX_IPCS is not set
+# BR2_PACKAGE_UTIL_LINUX_KILL is not set
+# BR2_PACKAGE_UTIL_LINUX_LAST is not set
+# BR2_PACKAGE_UTIL_LINUX_LINE is not set
+# BR2_PACKAGE_UTIL_LINUX_LOGGER is not set
+
+#
+# login needs a uClibc or glibc toolchain w/ wchar, locale, dynamic library
+#
+# BR2_PACKAGE_UTIL_LINUX_LOSETUP is not set
+# BR2_PACKAGE_UTIL_LINUX_LSLOGINS is not set
+# BR2_PACKAGE_UTIL_LINUX_LSMEM is not set
+# BR2_PACKAGE_UTIL_LINUX_MESG is not set
+# BR2_PACKAGE_UTIL_LINUX_MINIX is not set
+# BR2_PACKAGE_UTIL_LINUX_MORE is not set
+# BR2_PACKAGE_UTIL_LINUX_MOUNT is not set
+# BR2_PACKAGE_UTIL_LINUX_MOUNTPOINT is not set
+# BR2_PACKAGE_UTIL_LINUX_NEWGRP is not set
+# BR2_PACKAGE_UTIL_LINUX_NOLOGIN is not set
+BR2_PACKAGE_UTIL_LINUX_NSENTER=y
+# BR2_PACKAGE_UTIL_LINUX_PG is not set
+# BR2_PACKAGE_UTIL_LINUX_PARTX is not set
+# BR2_PACKAGE_UTIL_LINUX_PIVOT_ROOT is not set
+# BR2_PACKAGE_UTIL_LINUX_RAW is not set
+# BR2_PACKAGE_UTIL_LINUX_RENAME is not set
+# BR2_PACKAGE_UTIL_LINUX_RFKILL is not set
+
+#
+# runuser needs a uClibc or glibc toolchain w/ wchar, locale, dynamic library
+#
+
+#
+# scheduling utilities need a toolchain w/ headers >= 3.14
+#
+# BR2_PACKAGE_UTIL_LINUX_SETPRIV is not set
+# BR2_PACKAGE_UTIL_LINUX_SETTERM is not set
+
+#
+# su needs a uClibc or glibc toolchain w/ wchar, locale, dynamic library
+#
+# BR2_PACKAGE_UTIL_LINUX_SULOGIN is not set
+# BR2_PACKAGE_UTIL_LINUX_SWITCH_ROOT is not set
+# BR2_PACKAGE_UTIL_LINUX_TUNELP is not set
+# BR2_PACKAGE_UTIL_LINUX_UL is not set
+# BR2_PACKAGE_UTIL_LINUX_UNSHARE is not set
+# BR2_PACKAGE_UTIL_LINUX_UTMPDUMP is not set
+# BR2_PACKAGE_UTIL_LINUX_UUIDD is not set
+# BR2_PACKAGE_UTIL_LINUX_VIPW is not set
+# BR2_PACKAGE_UTIL_LINUX_WALL is not set
+# BR2_PACKAGE_UTIL_LINUX_WIPEFS is not set
+# BR2_PACKAGE_UTIL_LINUX_WDCTL is not set
+# BR2_PACKAGE_UTIL_LINUX_WRITE is not set
+# BR2_PACKAGE_UTIL_LINUX_ZRAMCTL is not set
 # BR2_PACKAGE_WATCHDOG is not set
 # BR2_PACKAGE_WATCHDOGD is not set
 # BR2_PACKAGE_XDG_DBUS_PROXY is not set

sshfs-static/configs/sshfs-static-armeabi-v7a.config

@@ -1,6 +1,6 @@
 #
 # Automatically generated file; DO NOT EDIT.
-# Buildroot 2025.11.11-sshfs Configuration
+# Buildroot 2022.02.1 Configuration
 #
 BR2_HAVE_DOT_CONFIG=y
 BR2_HOST_GCC_AT_LEAST_4_9=y
@@ -258,7 +258,7 @@ BR2_TOOLCHAIN_EXTERNAL_MUSL=y
 BR2_PACKAGE_HAS_TOOLCHAIN_EXTERNAL=y
 BR2_PACKAGE_PROVIDES_TOOLCHAIN_EXTERNAL="toolchain-external-custom"
 BR2_TOOLCHAIN_EXTERNAL_PREFIX="$(ARCH)-buildroot-linux-musleabi"
-BR2_TOOLCHAIN_EXTERNAL_URL="https://github.com/bobrofon/buildroot/releases/download/2022.04.17-musl-trusty/arm-buildroot-linux-musleabi.tar.xz"
+BR2_TOOLCHAIN_EXTERNAL_URL="https://github.com/bobrofon/buildroot/releases/download/2026.04.24-musl-trusty/arm-buildroot-linux-musleabi.tar.xz"
 BR2_TOOLCHAIN_EXTERNAL_REL_BIN_PATH="bin"
 BR2_TOOLCHAIN_EXTERNAL_CUSTOM_PREFIX="$(ARCH)-buildroot-linux-musleabi"
 # BR2_TOOLCHAIN_EXTERNAL_GCC_11 is not set
@@ -333,8 +333,8 @@ BR2_TOOLCHAIN_EXTERNAL_GCC_10=y
 # BR2_TOOLCHAIN_EXTERNAL_HEADERS_3_3 is not set
 # BR2_TOOLCHAIN_EXTERNAL_HEADERS_3_2 is not set
 # BR2_TOOLCHAIN_EXTERNAL_HEADERS_3_1 is not set
-# BR2_TOOLCHAIN_EXTERNAL_HEADERS_3_0 is not set
-BR2_TOOLCHAIN_EXTERNAL_HEADERS_REALLY_OLD=y
+BR2_TOOLCHAIN_EXTERNAL_HEADERS_3_0=y
+# BR2_TOOLCHAIN_EXTERNAL_HEADERS_REALLY_OLD is not set
 
 #
 # Kernel headers older than 3.13 is not tested by Buildroot. Use at your own risk.
@@ -376,7 +376,8 @@ BR2_USE_MMU=y
 BR2_TARGET_OPTIMIZATION=""
 BR2_TARGET_LDFLAGS="-Wl,-z,max-page-size=16384"
 # BR2_ECLIPSE_REGISTER is not set
-BR2_TOOLCHAIN_HEADERS_AT_LEAST="2.6"
+BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_0=y
+BR2_TOOLCHAIN_HEADERS_AT_LEAST="3.0"
 BR2_TOOLCHAIN_GCC_AT_LEAST_4_3=y
 BR2_TOOLCHAIN_GCC_AT_LEAST_4_4=y
 BR2_TOOLCHAIN_GCC_AT_LEAST_4_5=y
@@ -735,10 +736,7 @@ BR2_PACKAGE_LTRACE_ARCH_SUPPORTS=y
 #
 # BR2_PACKAGE_MEMSTAT is not set
 # BR2_PACKAGE_NETPERF is not set
-
-#
-# netsniff-ng needs a toolchain w/ threads, headers >= 3.0
-#
+# BR2_PACKAGE_NETSNIFF_NG is not set
 
 #
 # nmon needs a glibc toolchain
@@ -922,10 +920,7 @@ BR2_PACKAGE_PROVIDES_HOST_GETTEXT="host-gettext-tiny"
 # BR2_PACKAGE_GENPART is not set
 # BR2_PACKAGE_GENROMFS is not set
 # BR2_PACKAGE_IMX_USB_LOADER is not set
-
-#
-# mmc-utils needs a toolchain w/ headers >= 3.0
-#
+# BR2_PACKAGE_MMC_UTILS is not set
 # BR2_PACKAGE_MTD is not set
 # BR2_PACKAGE_MTOOLS is not set
 # BR2_PACKAGE_NFS_UTILS is not set
@@ -4430,7 +4425,82 @@ BR2_PACKAGE_SYSTEMD_BOOTCHART_ARCH_SUPPORTS=y
 #
 # unscd needs a glibc toolchain
 #
-# BR2_PACKAGE_UTIL_LINUX is not set
+BR2_PACKAGE_UTIL_LINUX=y
+# BR2_PACKAGE_UTIL_LINUX_LIBBLKID is not set
+# BR2_PACKAGE_UTIL_LINUX_LIBFDISK is not set
+# BR2_PACKAGE_UTIL_LINUX_LIBMOUNT is not set
+# BR2_PACKAGE_UTIL_LINUX_LIBSMARTCOLS is not set
+# BR2_PACKAGE_UTIL_LINUX_LIBUUID is not set
+# BR2_PACKAGE_UTIL_LINUX_BINARIES is not set
+# BR2_PACKAGE_UTIL_LINUX_AGETTY is not set
+# BR2_PACKAGE_UTIL_LINUX_BFS is not set
+# BR2_PACKAGE_UTIL_LINUX_CAL is not set
+
+#
+# chfn/chsh needs a toolchain w/ wchar, locale, dynamic library
+#
+# BR2_PACKAGE_UTIL_LINUX_CHMEM is not set
+# BR2_PACKAGE_UTIL_LINUX_CRAMFS is not set
+# BR2_PACKAGE_UTIL_LINUX_EJECT is not set
+# BR2_PACKAGE_UTIL_LINUX_FALLOCATE is not set
+# BR2_PACKAGE_UTIL_LINUX_FDFORMAT is not set
+# BR2_PACKAGE_UTIL_LINUX_FSCK is not set
+# BR2_PACKAGE_UTIL_LINUX_HARDLINK is not set
+# BR2_PACKAGE_UTIL_LINUX_HWCLOCK is not set
+# BR2_PACKAGE_UTIL_LINUX_IPCRM is not set
+# BR2_PACKAGE_UTIL_LINUX_IPCS is not set
+# BR2_PACKAGE_UTIL_LINUX_KILL is not set
+# BR2_PACKAGE_UTIL_LINUX_LAST is not set
+# BR2_PACKAGE_UTIL_LINUX_LINE is not set
+# BR2_PACKAGE_UTIL_LINUX_LOGGER is not set
+
+#
+# login needs a uClibc or glibc toolchain w/ wchar, locale, dynamic library
+#
+# BR2_PACKAGE_UTIL_LINUX_LOSETUP is not set
+# BR2_PACKAGE_UTIL_LINUX_LSLOGINS is not set
+# BR2_PACKAGE_UTIL_LINUX_LSMEM is not set
+# BR2_PACKAGE_UTIL_LINUX_MESG is not set
+# BR2_PACKAGE_UTIL_LINUX_MINIX is not set
+# BR2_PACKAGE_UTIL_LINUX_MORE is not set
+# BR2_PACKAGE_UTIL_LINUX_MOUNT is not set
+# BR2_PACKAGE_UTIL_LINUX_MOUNTPOINT is not set
+# BR2_PACKAGE_UTIL_LINUX_NEWGRP is not set
+# BR2_PACKAGE_UTIL_LINUX_NOLOGIN is not set
+BR2_PACKAGE_UTIL_LINUX_NSENTER=y
+# BR2_PACKAGE_UTIL_LINUX_PG is not set
+# BR2_PACKAGE_UTIL_LINUX_PARTX is not set
+# BR2_PACKAGE_UTIL_LINUX_PIVOT_ROOT is not set
+# BR2_PACKAGE_UTIL_LINUX_RAW is not set
+# BR2_PACKAGE_UTIL_LINUX_RENAME is not set
+# BR2_PACKAGE_UTIL_LINUX_RFKILL is not set
+
+#
+# runuser needs a uClibc or glibc toolchain w/ wchar, locale, dynamic library
+#
+
+#
+# scheduling utilities need a toolchain w/ headers >= 3.14
+#
+# BR2_PACKAGE_UTIL_LINUX_SETPRIV is not set
+# BR2_PACKAGE_UTIL_LINUX_SETTERM is not set
+
+#
+# su needs a uClibc or glibc toolchain w/ wchar, locale, dynamic library
+#
+# BR2_PACKAGE_UTIL_LINUX_SULOGIN is not set
+# BR2_PACKAGE_UTIL_LINUX_SWITCH_ROOT is not set
+# BR2_PACKAGE_UTIL_LINUX_TUNELP is not set
+# BR2_PACKAGE_UTIL_LINUX_UL is not set
+# BR2_PACKAGE_UTIL_LINUX_UNSHARE is not set
+# BR2_PACKAGE_UTIL_LINUX_UTMPDUMP is not set
+# BR2_PACKAGE_UTIL_LINUX_UUIDD is not set
+# BR2_PACKAGE_UTIL_LINUX_VIPW is not set
+# BR2_PACKAGE_UTIL_LINUX_WALL is not set
+# BR2_PACKAGE_UTIL_LINUX_WIPEFS is not set
+# BR2_PACKAGE_UTIL_LINUX_WDCTL is not set
+# BR2_PACKAGE_UTIL_LINUX_WRITE is not set
+# BR2_PACKAGE_UTIL_LINUX_ZRAMCTL is not set
 # BR2_PACKAGE_WATCHDOG is not set
 # BR2_PACKAGE_WATCHDOGD is not set
 # BR2_PACKAGE_XDG_DBUS_PROXY is not set