Add MCCP2 compressed stream support

lib/meow/session.rb

@@ -27,6 +27,7 @@ module MeowClient
     def run
       @form.wait
     ensure
+      @pipeline.close
       @transport.close
       @program.release(@transport, :close => false)
     end
@@ -83,6 +84,9 @@ module MeowClient
         receive_record(record) if record != nil
       end
       dispatch_speech
+    rescue Telnet::CompressionError
+      add_system_line(_("The compressed data stream could not be processed safely. The connection was closed."))
+      close_form
     rescue Exception => error
       Log.error("Meow session update failed: #{error.class}: #{error.message}") if defined?(Log)
       add_system_line(_("Session update error: %{message}") % {:message => error.message})

lib/meow/telnet.rb

@@ -1,3 +1,5 @@
+require "zlib"
+
 module MeowClient
   module Telnet
     IAC = 255
@@ -11,10 +13,13 @@ module MeowClient
     ECHO = 1
     SUPPRESS_GO_AHEAD = 3
     TERMINAL_TYPE = 24
+    COMPRESS2 = 86
     TTYPE_IS = 0
     TTYPE_SEND = 1
+    MAX_INFLATED_BYTES_PER_FEED = 1_048_576
 
     Result = Struct.new(:data, :replies, :events, keyword_init: true)
+    CompressionError = Class.new(StandardError)
 
     class Parser
       attr_reader :remote_echo
@@ -27,56 +32,101 @@ module MeowClient
         @remote_echo = false
         @remote_options = {}
         @local_options = {}
+        @inflater = nil
+        @compression_finished = false
       end
 
       def feed(bytes)
         output = +"".b
         replies = []
         events = []
-        bytes.to_s.b.each_byte do |byte|
-          case @state
-          when :data
-            if byte == IAC
-              @state = :iac
-            else
-              output << byte
-            end
-          when :iac
-            handle_iac(byte, output)
-          when :negotiation
-            reply, event = negotiate(@negotiation_command, byte)
-            replies << reply if reply != nil
-            events << event if event != nil
-            @state = :data
-          when :sb_option
-            @subnegotiation_option = byte
-            @subnegotiation.clear
-            @state = :sb
-          when :sb
-            if byte == IAC
-              @state = :sb_iac
-            else
-              @subnegotiation << byte
-            end
-          when :sb_iac
-            if byte == IAC
-              @subnegotiation << IAC
-              @state = :sb
-            elsif byte == SE
-              reply, event = finish_subnegotiation
-              replies << reply if reply != nil
-              events << event if event != nil
-              @state = :data
-            else
-              @state = :data
-            end
+        input = bytes.to_s.b
+        if @compression_finished && input != ""
+          raise CompressionError, "Data followed the end of the MCCP2 stream."
+        end
+
+        index = 0
+        while index < input.bytesize
+          if @inflater != nil
+            inflate(input.byteslice(index..-1), output, replies, events)
+            index = input.bytesize
+          else
+            consume_byte(input.getbyte(index), output, replies, events)
+            index += 1
           end
         end
         Result.new(:data => output, :replies => replies, :events => events)
+      rescue Zlib::Error => error
+        raise CompressionError, "Invalid MCCP2 stream: #{error.message}"
+      end
+
+      def close
+        inflater = @inflater
+        @inflater = nil
+        inflater.close if inflater != nil && !inflater.closed?
+        nil
+      rescue Zlib::Error
+        nil
       end
 
       private
 
+      def consume_byte(byte, output, replies, events)
+        case @state
+        when :data
+          if byte == IAC
+            @state = :iac
+          else
+            output << byte
+          end
+        when :iac
+          handle_iac(byte, output)
+        when :negotiation
+          reply, event = negotiate(@negotiation_command, byte)
+          replies << reply if reply != nil
+          events << event if event != nil
+          @state = :data
+        when :sb_option
+          @subnegotiation_option = byte
+          @subnegotiation.clear
+          @state = :sb
+        when :sb
+          if byte == IAC
+            @state = :sb_iac
+          else
+            @subnegotiation << byte
+          end
+        when :sb_iac
+          if byte == IAC
+            @subnegotiation << IAC
+            @state = :sb
+          elsif byte == SE
+            reply, event = finish_subnegotiation
+            replies << reply if reply != nil
+            events << event if event != nil
+            @state = :data
+          else
+            @state = :data
+          end
+        end
+      end
+
+      def inflate(bytes, output, replies, events)
+        inflated_bytes = 0
+        consume = proc do |chunk|
+          inflated_bytes += chunk.bytesize
+          if inflated_bytes > MAX_INFLATED_BYTES_PER_FEED
+            raise CompressionError, "MCCP2 output exceeded the safety limit."
+          end
+          chunk.each_byte { |byte| consume_byte(byte, output, replies, events) }
+        end
+
+        @inflater.inflate(bytes) { |chunk| consume.call(chunk) }
+        pending = @inflater.flush_next_out
+        consume.call(pending) if pending != ""
+        @compression_finished = true if @inflater.finished?
+      end
+
       def handle_iac(byte, output)
         case byte
         when IAC
@@ -99,7 +149,7 @@ module MeowClient
       def negotiate(command, option)
         case command
         when WILL
-          enabled = [ECHO, SUPPRESS_GO_AHEAD].include?(option)
+          enabled = [ECHO, SUPPRESS_GO_AHEAD, COMPRESS2].include?(option)
           changed = @remote_options[option] != enabled
           @remote_options[option] = enabled
           return [nil, nil] unless changed
@@ -131,6 +181,13 @@ module MeowClient
       end
 
       def finish_subnegotiation
+        if @subnegotiation_option == COMPRESS2 &&
+            @remote_options[COMPRESS2] == true &&
+            @subnegotiation.empty?
+          raise CompressionError, "MCCP2 compression was started more than once." if @inflater != nil
+          @inflater = Zlib::Inflate.new
+          return [nil, [:compression, true]]
+        end
         if @subnegotiation_option == TERMINAL_TYPE &&
             @local_options[TERMINAL_TYPE] == true &&
             @subnegotiation.getbyte(0) == TTYPE_SEND

lib/meow/text_pipeline.rb

@@ -94,6 +94,10 @@ module MeowClient
       prompt == nil ? [] : [prompt]
     end
 
+    def close
+      @telnet.close
+    end
+
     private
 
     def decode(bytes)