zmq4: add r/w test for greeting

Updates go-zeromq#56.

protocol.go

@@ -35,6 +35,8 @@ const (
 	hasMoreBitFlag   = 0x1
 	isLongBitFlag    = 0x2
 	isCommandBitFlag = 0x4
+
+	zmtpMsgLen = 64
 )
 
 var (
@@ -90,46 +92,42 @@ type greeting struct {
 }
 
 func (g *greeting) read(r io.Reader) error {
-	var data [64]byte
+	var data [zmtpMsgLen]byte
 	_, err := io.ReadFull(r, data[:])
 	if err != nil {
-		return err
+		return xerrors.Errorf("could not read ZMTP greeting: %w", err)
 	}
 
-	err = g.unmarshal(data[:])
-	if err != nil {
-		return err
-	}
+	g.unmarshal(data[:])
 
 	if g.Sig.Header != sigHeader {
-		return errGreeting
+		return xerrors.Errorf("invalid ZMTP signature header: %w", errGreeting)
 	}
 
 	if g.Sig.Footer != sigFooter {
-		return errGreeting
+		return xerrors.Errorf("invalid ZMTP signature footer: %w", errGreeting)
 	}
 
 	// FIXME(sbinet): handle version negotiations as per
 	// https://rfc.zeromq.org/spec:23/ZMTP/#version-negotiation
 	if g.Version != defaultVersion {
-		return errGreeting
+		return xerrors.Errorf(
+			"invalid ZMTP version (got=%v, want=%v): %w",
+			g.Version, defaultVersion, errGreeting,
+		)
 	}
 
 	return nil
 }
 
-func (g *greeting) unmarshal(data []byte) error {
-	if len(data) < 64 {
-		return io.ErrShortBuffer
-	}
-	_ = data[:64]
+func (g *greeting) unmarshal(data []byte) {
+	_ = data[:zmtpMsgLen]
 	g.Sig.Header = data[0]
 	g.Sig.Footer = data[9]
 	g.Version[0] = data[10]
 	g.Version[1] = data[11]
 	copy(g.Mechanism[:], data[12:32])
 	g.Server = data[32]
-	return nil
 }
 
 func (g *greeting) write(w io.Writer) error {
@@ -138,7 +136,7 @@ func (g *greeting) write(w io.Writer) error {
 }
 
 func (g *greeting) marshal() []byte {
-	var buf [64]byte
+	var buf [zmtpMsgLen]byte
 	buf[0] = g.Sig.Header
 	// padding 1 ignored
 	buf[9] = g.Sig.Footer

protocol_test.go

@@ -0,0 +1,115 @@
+// Copyright 2020 The go-zeromq Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package zmq4
+
+import (
+	"bytes"
+	"io"
+	"testing"
+
+	"golang.org/x/xerrors"
+)
+
+func TestGreeting(t *testing.T) {
+	for _, tc := range []struct {
+		name string
+		data []byte
+		want error
+	}{
+		{
+			name: "valid",
+			data: func() []byte {
+				w := new(bytes.Buffer)
+				g := greeting{
+					Version: defaultVersion,
+				}
+				g.Sig.Header = sigHeader
+				g.Sig.Footer = sigFooter
+				g.write(w)
+				return w.Bytes()
+			}(),
+		},
+		{
+			name: "empty-buffer",
+			data: nil,
+			want: xerrors.Errorf("could not read ZMTP greeting: %w", io.EOF),
+		},
+		{
+			name: "unexpected-EOF",
+			data: make([]byte, 1),
+			want: xerrors.Errorf("could not read ZMTP greeting: %w", io.ErrUnexpectedEOF),
+		},
+		{
+			name: "invalid-header",
+			data: func() []byte {
+				w := new(bytes.Buffer)
+				g := greeting{
+					Version: defaultVersion,
+				}
+				g.Sig.Header = sigFooter // err
+				g.Sig.Footer = sigFooter
+				g.write(w)
+				return w.Bytes()
+			}(),
+			want: xerrors.Errorf("invalid ZMTP signature header: %w", errGreeting),
+		},
+		{
+			name: "invalid-footer",
+			data: func() []byte {
+				w := new(bytes.Buffer)
+				g := greeting{
+					Version: defaultVersion,
+				}
+				g.Sig.Header = sigHeader
+				g.Sig.Footer = sigHeader // err
+				g.write(w)
+				return w.Bytes()
+			}(),
+			want: xerrors.Errorf("invalid ZMTP signature footer: %w", errGreeting),
+		},
+		{
+			name: "invalid-version", // FIXME(sbinet): adapt for when/if we support multiple ZMTP versions
+			data: func() []byte {
+				w := new(bytes.Buffer)
+				g := greeting{
+					Version: [2]uint8{1, 1},
+				}
+				g.Sig.Header = sigHeader
+				g.Sig.Footer = sigFooter
+				g.write(w)
+				return w.Bytes()
+			}(),
+			want: xerrors.Errorf("invalid ZMTP version (got=%v, want=%v): %w",
+				[2]uint{1, 1},
+				defaultVersion,
+				errGreeting,
+			),
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			var (
+				g greeting
+				r = bytes.NewReader(tc.data)
+			)
+
+			err := g.read(r)
+			switch {
+			case err == nil && tc.want == nil:
+				// ok
+			case err == nil && tc.want != nil:
+				t.Fatalf("expected an error (%s)", tc.want)
+			case err != nil && tc.want == nil:
+				t.Fatalf("could not read ZMTP greeting: %+v", err)
+			case err != nil && tc.want != nil:
+				if got, want := err.Error(), tc.want.Error(); got != want {
+					t.Fatalf("invalid ZMTP greeting error:\ngot= %+v\nwant=%+v\n",
+						got, want,
+					)
+				}
+			}
+
+		})
+	}
+}