Add vanilla parity harness and harden server boundaries

internal/protocol/frame_test.go

@@ -0,0 +1,99 @@
+package protocol
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"io"
+	"testing"
+)
+
+func TestReadPacketCompressionThreshold(t *testing.T) {
+	for _, tc := range []struct {
+		name      string
+		writeAt   int32
+		readAt    int32
+		wantError error
+	}{
+		{name: "compressed at threshold", writeAt: 4, readAt: 4},
+		{name: "compressed below threshold", writeAt: 4, readAt: 9, wantError: ErrBadCompression},
+		{name: "uncompressed below threshold", writeAt: 16, readAt: 16},
+		{name: "uncompressed at threshold", writeAt: 16, readAt: 4, wantError: ErrBadCompression},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			frame := AppendPacket(nil, tc.writeAt, 3, []byte("payload"))
+			pkt, err := ReadPacket(bufio.NewReader(bytes.NewReader(frame)), tc.readAt)
+			if !errors.Is(err, tc.wantError) {
+				t.Fatalf("ReadPacket error = %v, want %v", err, tc.wantError)
+			}
+			if tc.wantError == nil && (pkt.ID != 3 || string(pkt.Data) != "payload") {
+				t.Fatalf("packet = id %d data %q", pkt.ID, pkt.Data)
+			}
+		})
+	}
+}
+
+func TestReadPacketRejectsWrongDecompressedLength(t *testing.T) {
+	frame := AppendPacket(nil, 1, 3, []byte("payload"))
+	r := NewReader(frame)
+	length, err := r.VarInt()
+	if err != nil {
+		t.Fatal(err)
+	}
+	payload := append([]byte(nil), frame[len(frame)-int(length):]...)
+	payload[0]++
+	bad := AppendVarInt(nil, int32(len(payload)))
+	bad = append(bad, payload...)
+	if _, err := ReadPacket(bufio.NewReader(bytes.NewReader(bad)), 1); err == nil {
+		t.Fatal("accepted compressed payload shorter than its declared length")
+	}
+}
+
+func TestReadPacketRejectsTrailingCompressedData(t *testing.T) {
+	frame := AppendPacket(nil, 1, 3, []byte("payload"))
+	r := NewReader(frame)
+	length, err := r.VarInt()
+	if err != nil {
+		t.Fatal(err)
+	}
+	payload := append([]byte(nil), frame[len(frame)-int(length):]...)
+	payload = append(payload, 0)
+	bad := AppendVarInt(nil, int32(len(payload)))
+	bad = append(bad, payload...)
+	if _, err := ReadPacket(bufio.NewReader(bytes.NewReader(bad)), 1); !errors.Is(err, ErrBadCompression) {
+		t.Fatalf("error = %v, want ErrBadCompression", err)
+	}
+}
+
+type shortWriter struct{ buf bytes.Buffer }
+
+func (w *shortWriter) Write(p []byte) (int, error) {
+	if len(p) > 2 {
+		p = p[:2]
+	}
+	return w.buf.Write(p)
+}
+
+func TestWritePacketCompletesShortWrites(t *testing.T) {
+	w := new(shortWriter)
+	if err := WritePacket(w, -1, 7, []byte("body")); err != nil {
+		t.Fatal(err)
+	}
+	pkt, err := ReadPacket(bufio.NewReader(bytes.NewReader(w.buf.Bytes())), -1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if pkt.ID != 7 || string(pkt.Data) != "body" {
+		t.Fatalf("packet = id %d data %q", pkt.ID, pkt.Data)
+	}
+}
+
+type zeroWriter struct{}
+
+func (zeroWriter) Write([]byte) (int, error) { return 0, nil }
+
+func TestWritePacketRejectsNoProgress(t *testing.T) {
+	if err := WritePacket(zeroWriter{}, -1, 1, nil); !errors.Is(err, io.ErrShortWrite) {
+		t.Fatalf("error = %v, want io.ErrShortWrite", err)
+	}
+}