Land #10972, Rework session_compatible? check in post mixin, excluding ARCH_CMD modules

lib/msf/core/post_mixin.rb

@@ -138,13 +138,16 @@ module Msf::PostMixin
   #
   # Checks the session's type against this module's
   # <tt>module_info["SessionTypes"]</tt> as well as examining platform
-  # compatibility.  +sess_or_sid+ can be a Session object, Integer, or
-  # String.  In the latter cases it should be a key in
+  # and arch compatibility.
+  #
+  # +sess_or_sid+ can be a Session object, Integer, or
+  # String. In the latter cases it should be a key in
   # +framework.sessions+.
   #
   # @note Because it errs on the side of compatibility, a true return
   #   value from this method does not guarantee the module will work
-  #   with the session.
+  #   with the session. For example, ARCH_CMD modules can work on a
+  #   variety of platforms and archs and thus return true in this check.
   #
   # @param sess_or_sid [Msf::Session,Integer,String]
   #   A session or session ID to compare against this module for
@@ -160,28 +163,30 @@ module Msf::PostMixin
     end
 
     # Can't do anything without a session
-    return false if s.nil?
+    return false unless s
 
     # Can't be compatible if it's the wrong type
     if session_types
       return false unless session_types.include?(s.type)
     end
 
-    # Types are okay, now check the platform.
-    if self.platform and self.platform.kind_of?(Msf::Module::PlatformList)
-      return false unless self.platform.supports?(Msf::Module::PlatformList.transform(s.platform))
-    end
-
     # Check to make sure architectures match
     mod_arch = self.module_info['Arch']
-    unless mod_arch.nil?
+    if mod_arch
       mod_arch = [mod_arch] unless mod_arch.kind_of?(Array)
+      # Assume ARCH_CMD modules can work on supported SessionTypes
+      return true if mod_arch.include?(ARCH_CMD)
       return false unless mod_arch.include?(s.arch)
     end
 
+    # Arch is okay, now check the platform.
+    if self.platform && self.platform.kind_of?(Msf::Module::PlatformList)
+      return false unless self.platform.supports?(Msf::Module::PlatformList.transform(s.platform))
+    end
+
     # If we got here, we haven't found anything that definitely
     # disqualifies this session.  Assume that means we can use it.
-    return true
+    true
   end
 
   #