Add missing commits from rapid7#3770, lands rapid7#4393

Author: HD Moore

lib/msf/core/encoded_payload.rb

@@ -109,10 +109,13 @@ def encode
     if reqs['BadChars'] or reqs['Encoder'] or reqs['ForceEncode']
       encoders = pinst.compatible_encoders
 
-      # Fix encoding issue
+      # Make sure the encoder name from the user has the same String#encoding
+      # as the framework's list of encoder names so we can compare them later.
+      # This is important for when we get input from RPC.
       if reqs['Encoder']
         reqs['Encoder'] = reqs['Encoder'].encode(framework.encoders.keys[0].encoding)
       end
+
       # If the caller had a preferred encoder, use this encoder only
       if ((reqs['Encoder']) and (preferred = framework.encoders[reqs['Encoder']]))
         encoders = [ [reqs['Encoder'], preferred] ]
@@ -164,7 +167,7 @@ def encode
         if (reqs['ForceSaveRegisters'] and
             reqs['EncoderOptions'] and
             (reqs['EncoderOptions']['SaveRegisters'].to_s.length > 0) and
-            (! self.encoder.preserves_registers?))
+            (! self.encoder.can_preserve_registers?))
           wlog("#{pinst.refname}: Encoder #{encoder.refname} does not preserve registers and the caller needs #{reqs['EncoderOptions']['SaveRegisters']} preserved.",
             'core', LEV_1)
           next
@@ -236,6 +239,7 @@ def encode
         self.encoded = eout
         break
       }
+
       # If the encoded payload is nil, raise an exception saying that we
       # suck at life.
       if (self.encoded == nil)

lib/msf/core/encoder.rb

@@ -416,7 +416,7 @@ def to_native(buf)
   #
   # Determines whether the encoder can preserve registers at all
   #
-  def preserves_registers?
+  def can_preserve_registers?
     false
   end
 

lib/msf/core/payload/stager.rb

@@ -240,10 +240,11 @@ def encode_stage(stg)
     end
 
     # Allow the user to specify additional registers to preserve
-    saved_registers = (
-      datastore['StageEncoderSaveRegisters'].to_s + " "
+    saved_registers =
+      datastore['StageEncoderSaveRegisters'].to_s +
+      " " +
       encode_stage_preserved_registers
-    ).strip
+    saved_registers.strip!
 
     estg = nil
 
@@ -262,6 +263,7 @@ def encode_stage(stg)
       if encp.encoder
         print_status("Encoded stage with #{encp.encoder.refname}")
         estg = encp.encoded
+
         break
       end
     end

modules/encoders/x86/call4_dword_xor.rb

@@ -51,7 +51,7 @@ def decoder_stub(state)
   end
 
   # Indicate that this module can preserve some registers
-  def preserves_registers?
+  def can_preserve_registers?
     true
   end
 

modules/encoders/x86/countdown.rb

@@ -64,7 +64,7 @@ def encode_block(state, block)
   end
 
   # Indicate that this module can preserve some registers
-  def preserves_registers?
+  def can_preserve_registers?
     true
   end
 

modules/encoders/x86/fnstenv_mov.rb

@@ -55,7 +55,7 @@ def decoder_stub(state)
   end
 
   # Indicate that this module can preserve some registers
-  def preserves_registers?
+  def can_preserve_registers?
     true
   end
 

modules/encoders/x86/shikata_ga_nai.rb

@@ -69,7 +69,7 @@ def decoder_stub(state)
   end
 
   # Indicate that this module can preserve some registers
-  def preserves_registers?
+  def can_preserve_registers?
     true
   end