tools/mpremote: Prevent deletion of /remote files via rm -r.

Removes the risk of inadvertently deleting files on the host by preventing
the deletion of files via `rm -r` on the `/remote` vfs mount point.

Fixes issue micropython#17147.

Signed-off-by: Jos Verlinde <jos_verlinde@hotmail.com>

Author: Josverl

tools/mpremote/mpremote/commands.py

@@ -303,6 +303,17 @@ def _mkdir(a, *b):
 
 def do_filesystem_recursive_rm(state, path, args):
     if state.transport.fs_isdir(path):
+        if state.transport.mounted:
+            r_cwd = state.transport.eval("os.getcwd()")
+            abs_path = os.path.normpath(
+                os.path.join(r_cwd, path) if not os.path.isabs(path) else path
+            )
+            if isinstance(state.transport, SerialTransport) and abs_path.startswith(
+                f'{SerialTransport.fs_hook_mount}/'
+            ):
+                raise CommandError(
+                    f"rm -r not permitted on {SerialTransport.fs_hook_mount} directory"
+                )
         for entry in state.transport.fs_listdir(path):
             do_filesystem_recursive_rm(state, _remote_path_join(path, entry.name), args)
         if path:

tools/mpremote/mpremote/transport_serial.py

@@ -42,6 +42,8 @@
 
 
 class SerialTransport(Transport):
+    fs_hook_mount = "/remote"  # MUST match the mount point in fs_hook_code
+
     def __init__(self, device, baudrate=115200, wait=0, exclusive=True, timeout=None):
         self.in_raw_repl = False
         self.use_raw_paste = True
@@ -375,7 +377,11 @@ def write_ctrl_d(self, out_callback):
         self.serial = self.serial.orig_serial
 
         # Provide a message about the remount.
-        out_callback(bytes(f"\r\nRemount local directory {self.cmd.root} at /remote\r\n", "utf8"))
+        out_callback(
+            bytes(
+                f"\r\nRemount local directory {self.cmd.root} at {self.fs_hook_mount}\r\n", "utf8"
+            )
+        )
 
         # Enter raw REPL and re-mount the remote filesystem.
         self.serial.write(b"\x01")
@@ -392,7 +398,7 @@ def write_ctrl_d(self, out_callback):
 
     def umount_local(self):
         if self.mounted:
-            self.exec('os.umount("/remote")')
+            self.exec(f'os.umount("{self.fs_hook_mount}")')
             self.mounted = False
             self.serial = self.serial.orig_serial
 
@@ -413,7 +419,7 @@ def umount_local(self):
     "CMD_RMDIR": 13,
 }
 
-fs_hook_code = """\
+fs_hook_code = f"""\
 import os, io, struct, micropython
 
 SEEK_SET = 0
@@ -746,8 +752,8 @@ def open(self, path, mode):
 
 
 def __mount():
-    os.mount(RemoteFS(RemoteCommand()), '/remote')
-    os.chdir('/remote')
+    os.mount(RemoteFS(RemoteCommand()), '{SerialTransport.fs_hook_mount}')
+    os.chdir('{SerialTransport.fs_hook_mount}')
 """
 
 # Apply basic compression on hook code.