Ensure regex are linear time.

Author: samuel-williams-shopify

lib/protocol/http1/connection.rb

@@ -40,8 +40,8 @@ module HTTP1
 		WS = /[ \t]/ # Whitespace.
 		OWS = /#{WS}*/ # Optional whitespace.
 		VCHAR = /[!-~]/ # Match visible characters from ASCII 33 to 126.
-		FIELD_VALUE = /(?:#{VCHAR}+(?:#{WS}+#{VCHAR})*)*/.freeze
-		HEADER = /\A(#{FIELD_NAME}):#{OWS}(#{FIELD_VALUE})#{OWS}\z/.freeze
+		FIELD_VALUE = /#{VCHAR}+(?:#{WS}+#{VCHAR}+)*/.freeze
+		HEADER = /\A(#{FIELD_NAME}):#{OWS}(?:(#{FIELD_VALUE})#{OWS})?\z/.freeze
 
 		VALID_FIELD_NAME = /\A#{FIELD_NAME}\z/.freeze
 		VALID_FIELD_VALUE = /\A#{FIELD_VALUE}\z/.freeze
@@ -487,7 +487,7 @@ def read_headers
 					break if line.empty?
 
 					if match = line.match(HEADER)
-						fields << [match[1], match[2]]
+						fields << [match[1], match[2] || ""]
 					else
 						raise BadHeader, "Could not parse header: #{line.inspect}"
 					end

test/protocol/http1/parser.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2025, by Samuel Williams.
+
+require "protocol/http1/connection"
+
+describe Protocol::HTTP1 do
+	describe "REQUEST_LINE" do
+		it "parses in linear time"  do
+			skip_unless_method_defined(:linear_time?, Regexp.singleton_class)
+
+			expect(Regexp).to be(:linear_time?, Protocol::HTTP1::REQUEST_LINE)
+		end
+	end
+
+	describe "HEADER" do
+		it "parses in linear time"  do
+			skip_unless_method_defined(:linear_time?, Regexp.singleton_class)
+
+			expect(Regexp).to be(:linear_time?, Protocol::HTTP1::HEADER)
+		end
+	end
+
+	describe "VALID_FIELD_NAME" do
+		it "parses in linear time"  do
+			skip_unless_method_defined(:linear_time?, Regexp.singleton_class)
+
+			expect(Regexp).to be(:linear_time?, Protocol::HTTP1::VALID_FIELD_NAME)
+		end
+	end
+
+	describe "VALID_FIELD_VALUE" do
+		it "parses in linear time"  do
+			skip_unless_method_defined(:linear_time?, Regexp.singleton_class)
+
+			expect(Regexp).to be(:linear_time?, Protocol::HTTP1::VALID_FIELD_VALUE)
+		end
+	end
+end