Add Specs for mkdir post API to behave consistently across session types

[Nayeraneru]

Summary

This PR fixes #20697
Currently, powershell, Windows shell, and Unix (mkdir -p) automatically create intermediate directories. However, Windows Meterpreter relies on CreateDirectoryW, which fails if parent directories do not exist. This leads to inconsistent behavior depending on the session type.

Change

This PR introduces a recursive helper method meterpreter_mkdir_p and meterpreter_parent_directory to emulate mkdir -p behavior for Meterpreter sessions.

The implementation:

• Checks whether the target directory already exists.
• Attempts to create the directory.
• If creation fails due to a missing parent, it recursively creates the parent directory first.
• Retries directory creation after ensuring the parent exists.
• Normalizes path separators for cross-platform compatibility.
• Handles Windows drive roots correctly (e.g., C:\).

[jvoisin]

This looks a bit overengineered compared to a simple for loop splitting on path separator and creating folders. Or even better, adding an mkdir_p method to meterpreter tbh.

[Nayeraneru]

This looks a bit overengineered compared to a simple for loop splitting on path separator and creating folders. Or even better, adding an mkdir_p method to meterpreter tbh.

Thanks for the feedback. I agree that the iterative approach is simpler and more straightforward in many cases.

For paths like C:\Temp\A\B\C (where C:\Temp exists but A is missing), the loop version might fail if it doesn’t handle C: and separators correctly, or it would require manual parent checking. The recursive version automatically creates all missing directories (A, B, C).

For Unix-style paths like /tmp/A/B/C, the loop version works only if the parent directories already exist; otherwise, it fails unless extra checks are added. The recursive version works regardless of which intermediate directories exist.

So while iteration is simpler and easier to read, recursion mirrors mkdir -p behavior and handles missing parents naturally, providing safer and more consistent behavior in all scenarios.

[jvoisin]

What's wrong with something like his:

directories = directory.s.split(s.fs.file.separator)
if session.platform == 'windows'
  current_dir = directories.pop()  # to get the drive letter
end

current_dir = ''
directories do | dir |
  current_dir += s.fs.file.separator + dir
  session.fs.dir.mkdir(current_dir) unless directory?(current_dir)
end

[Nayeraneru]

What's wrong with something like his:

directories = directory.s.split(s.fs.file.separator)
if session.platform == 'windows'
  current_dir = directories.pop()  # to get the drive letter
end

current_dir = ''
directories do | dir |
  current_dir += s.fs.file.separator + dir
  session.fs.dir.mkdir(current_dir) unless directory?(current_dir)
end

Thanks for the suggestion and for sharing the example, It is very helpful.

I’ve updated the code to use the same iterative approach you described. One small change I made was around Windows drive handling: instead of deriving the drive from the split path, I detect the drive root (C: / C:\) directly from the normalized path, which avoids some ambiguity depending on how the path is structured.
I also normalize path separators up front and build the path incrementally to avoid duplicate separators, while keeping the same mkdir -p behavior overall.

Does this look reasonable to you, or would you suggest any further tweaks?

def meterpreter_mkdir_p(path)
  return nil if directory?(path)

  separator = session.fs.file.separator
  normalized = path.tr('\\/', separator)
  directories = normalized.split(separator)
  current_path = ''

  if normalized.match?(/\A[a-zA-Z]:#{Regexp.escape(separator)}?/)
    current_path = "#{directories.shift}#{separator}"
  elsif normalized.start_with?(separator)
    current_path = separator
  end

  directories.each do |dir|
    next if dir.empty?

    current_path =
      if current_path.end_with?(separator) || current_path.empty?
        "#{current_path}#{dir}"
      else
        "#{current_path}#{separator}#{dir}"
      end

    session.fs.dir.mkdir(current_path) unless directory?(current_path)
  end

  nil
end

note: meterpreter_parent_directory function is removed from the code

[msutovsky-r7]

The issue should be probably addressed on Meterpreter side, to avoid overhead of sending data for each path level. The specs should be kept though.

[Nayeraneru]

@msutovsky-r7 Could you please guide me on which file(s) I should work on? The codebase is quite overwhelming.

[msutovsky-r7]

I think we're gonna move changes from lib/msf/core/post/file.rb and address them in Meterpreter (metasploit-payloads and mettle). I would recommend remove changes from lib/msf/core/post/file.rb and leave only specs file as we can keep that and it's looking good.

[Nayeraneru]

Got it
I think I should work on metasploit-payloads/c/meterpreter/source/extension/stdapi/server/fs/fs_win.c

[msutovsky-r7]

Will wait here till this and this is merged. Thank you @Nayeraneru !