Enhance windows post/file support

[dwelch-r7]

Summary

Windows post file support is lacking in several key methods

• executable?
• writable?
• immutable?
• readable?
• attributes
• chmod
• find_writable_directories
• stat
  https://github.com/rapid7/metasploit-framework/blob/68210662174819c05cb2ed3ed0bb4f808219ca59/lib/msf/core/post/file.rb

Now obviously not all of these should or even can be implemented on windows, chmod would be a good example of this but at the same time having the function raise an exception in these cases means we have to have ugly guard clauses around code when a no-op would work just fine for example

discussion started from this PR #21477

Motivation

Windows and linux post file support should have parity where possible and not require guard clauses around the system type leaking into module code if not absolutely necessary

[h00die]

after doing a bunch of windows persistence, the lacking writable? was sorely missed

[bcoles]

after doing a bunch of windows persistence, the lacking writable? was sorely missed

There is a proposed writable? implementation here:

https://github.com/rapid7/metasploit-framework/pull/21227/changes#diff-8d9014beb4901667e765a71f6148fd15c048f5eaaa5a97a19404a272b913b592R127

[jheysel-r7]

after doing a bunch of windows persistence, the lacking writable? was sorely missed

There is a proposed writable? implementation here:

https://github.com/rapid7/metasploit-framework/pull/21227/changes#diff-8d9014beb4901667e765a71f6148fd15c048f5eaaa5a97a19404a272b913b592R127

Renaming a file and then renaming it back seems invasive for a library. I think we could open a write handle to a file to without changing it to evaluate the permissions of the user:

function Test-FileWritable {
    param([Parameter(Mandatory)][string]$Path)
    try {
        $fs = [System.IO.File]::Open(
            $Path,
            [System.IO.FileMode]::Open,
            [System.IO.FileAccess]::Write,
            [System.IO.FileShare]::ReadWrite   # don't disturb other readers/writers
        )
        $fs.Dispose()
        $true
    }
    catch [System.UnauthorizedAccessException] { $false }
    catch [System.IO.IOException]              { $false }  # locked/sharing violation
}

Opening with FileMode.Open shouldn't change anything (even the last-write time) while the kernel preforms the access check.

Doing the same in a shell is slightly harder but you can almost get away with the following:

@echo off
set "f=C:\path\to\file.txt"

if not exist "%f%" (
    echo File does not exist
    exit /b 2
)

(type nul >> "%f%") 2>nul && (
    echo Writable
) || (
    echo Not writable
)

This tests access for FILE_APPEND_DATA rather than generic write as the redirection >> makes cmd open the file for append. Not quite accurate but something to consider.