Fix handling of padding.

Fixes <socketry/async-http#112>.

Author: ioquatix

lib/protocol/http2/padded.rb

@@ -29,11 +29,11 @@ def pack(data, padding_size: nil, maximum_size: nil)
 
 					buffer = String.new.b
 
-					buffer << padding_size.chr
+					buffer << padding_size
 					buffer << data
 
-					if padding_size > 1
-						buffer << "\0" * (padding_size - 1)
+					if padding_size
+						buffer << ("\0" * padding_size)
 					end
 
 					super buffer
@@ -47,7 +47,9 @@ def pack(data, padding_size: nil, maximum_size: nil)
 			def unpack
 				if padded?
 					padding_size = @payload[0].ord
-					data_size = @payload.bytesize - padding_size
+					
+					# 1 byte for the padding octet, and padding_size bytes for the padding itself:
+					data_size = @payload.bytesize - (1 + padding_size)
 
 					if data_size < 0
 						raise ProtocolError, "Invalid padding length: #{padding_size}"

test/protocol/http2/data_frame.rb

@@ -54,14 +54,14 @@ def before
 		it "adds appropriate padding" do
 			frame.pack "Hello World!", padding_size: 4
 
-			expect(frame.length).to be == 16
+			expect(frame.length).to be == 17
 			expect(frame.payload[0].ord).to be == 4
 			expect(frame.unpack).to be == "Hello World!"
 
 			stream = StringIO.new
 			frame.write(stream)
 
-			expect(stream.string.bytesize).to be == 25
+			expect(stream.string.bytesize).to be == 26
 			stream.rewind
 
 			frame2 = subject.new
@@ -74,12 +74,12 @@ def before
 		it "detects invalid padding" do
 			frame.pack "Hello World!", padding_size: 4
 
-			expect(frame.length).to be == 16
+			expect(frame.length).to be == 17
 			expect(frame.payload[0].ord).to be == 4
 			expect(frame.unpack).to be == "Hello World!"
 
 			# Artifically set the padding to be the entire payload:
-			frame.payload[0] = (frame.payload.bytesize).chr
+			frame.payload[0] = (frame.payload.bytesize - 1).chr
 			expect(frame.unpack).to be == ""
 
 			# Artifically set the padding to be larger than the payload: