Handle weird PowerShell edge case

lib/msf/base/sessions/powershell.rb

@@ -86,6 +86,17 @@ def self.to_cmd(cmd_and_args)
         needs_single_quoting = true
       end
 
+      will_be_double_quoted_by_powershell = [' ', '\t', '\v'].any? do |bad_char|
+        arg.include?(bad_char)
+      end
+
+      if will_be_double_quoted_by_powershell
+        # This is horrible, and I'm so so sorry.
+        # If an argument ends with a series of backslashes, and it will be quoted by PowerShell when *it* launches the process (e.g. because the arg contains a space),
+        # PowerShell will not correctly handle backslashes immediately preceeding the quote that it *itself* adds. So we need to be responsible for this.
+        arg = arg.gsub(/(\\*)$/, '\\1\\1')
+      end
+
       if needs_single_quoting
         arg = "'#{arg}'"
       end

spec/lib/msf/base/sessions/command_shell_windows_spec.rb

@@ -34,7 +34,7 @@
     end
 
     it 'should handle the weird backslash escaping behaviour in front of quotes' do
-      expect(described_class.to_cmd(['test.exe'] + ['quote\\\\"'])).to eq('test.exe "quote\\\\\\\\"""')
+      expect(described_class.to_cmd(['test.exe'] + ['quote\\\\"'])).to eq('test.exe "quote\\\\\\\\""')
       expect(described_class.to_cmd(['test.exe'] + ['will be quoted\\\\'])).to eq('test.exe "will be quoted\\\\\\\\"')
       expect(described_class.to_cmd(['test.exe'] + ['will be quoted\\\\ '])).to eq('test.exe "will be quoted\\\\ "') # Should not be doubled up
       expect(described_class.to_cmd(['test.exe'] + ['"test"', 'test\\"', 'test\\\\"', 'test words\\\\\\\\', 'test words\\\\\\', '\\\\'])).to eq('test.exe """test""" "test\\\\"" "test\\\\\\\\"" "test words\\\\\\\\\\\\\\\\" "test words\\\\\\\\\\\\" \\\\')

test/modules/post/test/cmd_exec.rb

@@ -84,6 +84,10 @@ def valid_show_args_response?(output, expected:)
 
     # Match the binary name, to support the binary name containing relative or absolute paths, i.e.
     # "show_args.exe\r\none\r\ntwo",
+    if output_binary.nil?
+      vprint_status("#{__method__}: Malformed output: no process binary returned")
+      return false
+    end
     match = output_binary.include?(expected[0]) && output_args == expected[1..]
     if !match
       vprint_status("#{__method__}: expected: #{expected.inspect} - actual: #{output_lines.inspect}")