Add MCCP2 compressed stream support

2026-09-17 16:18:16 +02:00
parent da967f4d56
commit 158ee2568c
8 changed files with 238 additions and 45 deletions
@@ -1,5 +1,7 @@
 # encoding: UTF-8

+require "zlib"
+
 require_relative "test_helper"
 require_relative "../lib/meow/telnet"

@@ -94,4 +96,104 @@ module MeowTelnetTest
    MeowTest.assert_empty(result.replies)
    MeowTest.assert_empty(result.events)
  end
+
+  MeowTest.test("Telnet negotiates MCCP2 once") do
+    parser = Telnet::Parser.new
+    packet = bytes(Telnet::IAC, Telnet::WILL, Telnet::COMPRESS2)
+    first = parser.feed(packet)
+    duplicate = parser.feed(packet)
+
+    MeowTest.assert_equal([bytes(Telnet::IAC, Telnet::DO, Telnet::COMPRESS2)], first.replies)
+    MeowTest.assert_empty(duplicate.replies)
+  end
+
+  MeowTest.test("Telnet starts MCCP2 only after negotiation") do
+    marker = bytes(Telnet::IAC, Telnet::SB, Telnet::COMPRESS2, Telnet::IAC, Telnet::SE)
+    parser = Telnet::Parser.new
+    before = parser.feed(marker)
+    parser.feed(bytes(Telnet::IAC, Telnet::WILL, Telnet::COMPRESS2))
+    after = parser.feed(marker + Zlib::Deflate.deflate("compressed text".b))
+
+    MeowTest.assert_equal([[:subnegotiation, Telnet::COMPRESS2]], before.events)
+    MeowTest.assert_equal("compressed text".b, after.data)
+    MeowTest.assert_equal([[:compression, true]], after.events)
+  ensure
+    parser.close if parser != nil
+  end
+
+  MeowTest.test("MCCP2 survives every activation and compressed input boundary") do
+    negotiation = bytes(Telnet::IAC, Telnet::WILL, Telnet::COMPRESS2)
+    marker = bytes(Telnet::IAC, Telnet::SB, Telnet::COMPRESS2, Telnet::IAC, Telnet::SE)
+    payload = "room description\r\n".b
+    packet = negotiation + marker + Zlib::Deflate.deflate(payload)
+    whole_parser = Telnet::Parser.new
+    split_parser = Telnet::Parser.new
+    whole = collect(whole_parser, [packet])
+    split = collect(split_parser, packet.bytes.map { |byte| bytes(byte) })
+
+    MeowTest.assert_equal(whole, split)
+    MeowTest.assert_equal(payload, split[:data])
+    MeowTest.assert_equal([[:compression, true]], split[:events])
+  ensure
+    whole_parser.close if whole_parser != nil
+    split_parser.close if split_parser != nil
+  end
+
+  MeowTest.test("MCCP2 inflated bytes continue through Telnet parsing") do
+    parser = Telnet::Parser.new
+    parser.feed(bytes(Telnet::IAC, Telnet::WILL, Telnet::COMPRESS2))
+    marker = bytes(Telnet::IAC, Telnet::SB, Telnet::COMPRESS2, Telnet::IAC, Telnet::SE)
+    payload = "hello".b + bytes(Telnet::IAC, Telnet::WILL, Telnet::ECHO) + " world".b
+    result = parser.feed(marker + Zlib::Deflate.deflate(payload))
+
+    MeowTest.assert_equal("hello world".b, result.data)
+    MeowTest.assert_equal([bytes(Telnet::IAC, Telnet::DO, Telnet::ECHO)], result.replies)
+    MeowTest.assert_equal([[:compression, true], [:remote_echo, true]], result.events)
+  ensure
+    parser.close if parser != nil
+  end
+
+
+
+  MeowTest.test("MCCP2 keeps one compressed stream across input chunks") do
+    parser = Telnet::Parser.new
+    deflater = Zlib::Deflate.new
+    parser.feed(bytes(Telnet::IAC, Telnet::WILL, Telnet::COMPRESS2))
+    marker = bytes(Telnet::IAC, Telnet::SB, Telnet::COMPRESS2, Telnet::IAC, Telnet::SE)
+    first = deflater.deflate("first ".b, Zlib::SYNC_FLUSH)
+    MeowTest.assert_equal("first ".b, parser.feed(marker + first).data)
+
+    second = deflater.deflate("second".b, Zlib::SYNC_FLUSH)
+    MeowTest.assert_equal("second".b, parser.feed(second).data)
+  ensure
+    parser.close if parser != nil
+    deflater.close if deflater != nil && !deflater.closed?
+  end
+
+  MeowTest.test("MCCP2 rejects malformed streams and data after stream end") do
+    marker = bytes(Telnet::IAC, Telnet::SB, Telnet::COMPRESS2, Telnet::IAC, Telnet::SE)
+    malformed = Telnet::Parser.new
+    malformed.feed(bytes(Telnet::IAC, Telnet::WILL, Telnet::COMPRESS2))
+    MeowTest.assert_raises(Telnet::CompressionError) { malformed.feed(marker + "not zlib".b) }
+
+    finished = Telnet::Parser.new
+    finished.feed(bytes(Telnet::IAC, Telnet::WILL, Telnet::COMPRESS2))
+    finished.feed(marker + Zlib::Deflate.deflate("done".b))
+    MeowTest.assert_raises(Telnet::CompressionError) { finished.feed("extra".b) }
+  ensure
+    malformed.close if malformed != nil
+    finished.close if finished != nil
+  end
+
+  MeowTest.test("MCCP2 limits inflated output per feed") do
+    parser = Telnet::Parser.new
+    parser.feed(bytes(Telnet::IAC, Telnet::WILL, Telnet::COMPRESS2))
+    marker = bytes(Telnet::IAC, Telnet::SB, Telnet::COMPRESS2, Telnet::IAC, Telnet::SE)
+    oversized = "a".b * (Telnet::MAX_INFLATED_BYTES_PER_FEED + 1)
+    MeowTest.assert_raises(Telnet::CompressionError) do
+      parser.feed(marker + Zlib::Deflate.deflate(oversized))
+    end
+  ensure
+    parser.close if parser != nil
+  end
 end