From: Jeff Halter <redacted>
Date: Sun, 5 Jun 2022 19:00:02 +0000 (-0700)
Subject: Handle zero length comment and file paths for Nostalgia compatibility
X-Git-Url: https://git.r.bdr.sh/rbdr/mobius/commitdiff_plain/050407a3b7f719ed6ce9367eb803bf948075e50e?ds=sidebyside

Handle zero length comment and file paths for Nostalgia compatibility
---

diff --git a/hotline/file_path.go b/hotline/file_path.go
index f7da298..3ff2435 100644
--- a/hotline/file_path.go
+++ b/hotline/file_path.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/binary"
 	"errors"
+	"io"
 	"path"
 	"strings"
 )
@@ -19,37 +20,39 @@ type FilePathItem struct {
 	Name []byte
 }
 
-func NewFilePathItem(b []byte) FilePathItem {
-	return FilePathItem{
-		Len:  b[2],
-		Name: b[3:],
-	}
-}
-
 type FilePath struct {
 	ItemCount [2]byte
 	Items     []FilePathItem
 }
 
-const minFilePathLen = 2
-
 func (fp *FilePath) UnmarshalBinary(b []byte) error {
-	if b == nil {
-		return nil
-	}
-	if len(b) < minFilePathLen {
-		return errors.New("insufficient bytes")
-	}
-	err := binary.Read(bytes.NewReader(b[0:2]), binary.BigEndian, &fp.ItemCount)
-	if err != nil {
+	reader := bytes.NewReader(b)
+	err := binary.Read(reader, binary.BigEndian, &fp.ItemCount)
+	if err != nil && !errors.Is(err, io.EOF) {
 		return err
 	}
+	if errors.Is(err, io.EOF) {
+		return nil
+	}
 
-	pathData := b[2:]
 	for i := uint16(0); i < fp.Len(); i++ {
-		segLen := pathData[2]
-		fp.Items = append(fp.Items, NewFilePathItem(pathData[:segLen+3]))
-		pathData = pathData[3+segLen:]
+		// skip two bytes for the file path delimiter
+		_, _ = reader.Seek(2, io.SeekCurrent)
+
+		// read the length of the next pathItem
+		segLen, err := reader.ReadByte()
+		if err != nil {
+			return err
+		}
+
+		pBytes := make([]byte, segLen)
+
+		_, err = reader.Read(pBytes)
+		if err != nil && !errors.Is(err, io.EOF) {
+			return err
+		}
+
+		fp.Items = append(fp.Items, FilePathItem{Len: segLen, Name: pBytes})
 	}
 
 	return nil
diff --git a/hotline/file_path_test.go b/hotline/file_path_test.go
index 4c2f6db..f25941e 100644
--- a/hotline/file_path_test.go
+++ b/hotline/file_path_test.go
@@ -41,6 +41,17 @@ func TestFilePath_UnmarshalBinary(t *testing.T) {
 			},
 			wantErr: false,
 		},
+		{
+			name: "handles empty data payload",
+			args: args{b: []byte{
+				0x00, 0x00,
+			}},
+			want: FilePath{
+				ItemCount: [2]byte{0x00, 0x00},
+				Items:     []FilePathItem(nil),
+			},
+			wantErr: false,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -78,7 +89,7 @@ func Test_readPath(t *testing.T) {
 					0x61, 0x61, 0x61,
 				},
 			},
-			want: "",
+			want:    "",
 			wantErr: true,
 		},
 		{
@@ -87,7 +98,6 @@ func Test_readPath(t *testing.T) {
 				fileRoot: "/usr/local/var/mobius/Files",
 				filePath: nil,
 				fileName: []byte("foo"),
-
 			},
 			want: "/usr/local/var/mobius/Files/foo",
 		},
@@ -153,4 +163,4 @@ func Test_readPath(t *testing.T) {
 			}
 		})
 	}
-}
\ No newline at end of file
+}
diff --git a/hotline/flattened_file_object.go b/hotline/flattened_file_object.go
index 6f38e46..a43677b 100644
--- a/hotline/flattened_file_object.go
+++ b/hotline/flattened_file_object.go
@@ -110,20 +110,10 @@ type FlatFileDataForkHeader struct {
 }
 
 func (ffif *FlatFileInformationFork) UnmarshalBinary(b []byte) error {
-
 	nameSize := b[70:72]
 	bs := binary.BigEndian.Uint16(nameSize)
-
 	nameEnd := 72 + bs
 
-	commentSize := b[nameEnd : nameEnd+2]
-	commentLen := binary.BigEndian.Uint16(commentSize)
-
-	commentStartPos := int(nameEnd) + 2
-	commentEndPos := int(nameEnd) + 2 + int(commentLen)
-
-	comment := b[commentStartPos:commentEndPos]
-
 	ffif.Platform = b[0:4]
 	ffif.TypeSignature = b[4:8]
 	ffif.CreatorSignature = b[8:12]
@@ -135,8 +125,16 @@ func (ffif *FlatFileInformationFork) UnmarshalBinary(b []byte) error {
 	ffif.NameScript = b[68:70]
 	ffif.NameSize = b[70:72]
 	ffif.Name = b[72:nameEnd]
-	ffif.CommentSize = b[nameEnd : nameEnd+2]
-	ffif.Comment = comment
+
+	if len(b) > int(nameEnd) {
+		ffif.CommentSize = b[nameEnd : nameEnd+2]
+		commentLen := binary.BigEndian.Uint16(ffif.CommentSize)
+
+		commentStartPos := int(nameEnd) + 2
+		commentEndPos := int(nameEnd) + 2 + int(commentLen)
+
+		ffif.Comment = b[commentStartPos:commentEndPos]
+	}
 
 	return nil
 }
diff --git a/hotline/flattened_file_object_test.go b/hotline/flattened_file_object_test.go
index 9a57e7e..1d43818 100644
--- a/hotline/flattened_file_object_test.go
+++ b/hotline/flattened_file_object_test.go
@@ -2,6 +2,7 @@ package hotline
 
 import (
 	"fmt"
+	"github.com/davecgh/go-spew/spew"
 	"github.com/stretchr/testify/assert"
 	"os"
 	"testing"
@@ -65,3 +66,41 @@ func TestNewFlattenedFileObject(t *testing.T) {
 		})
 	}
 }
+
+func TestFlatFileInformationFork_UnmarshalBinary(t *testing.T) {
+	type args struct {
+		b []byte
+	}
+	tests := []struct {
+		name    string
+		args    args
+		wantErr assert.ErrorAssertionFunc
+	}{
+		{
+			name: "when zero length comment size is omitted (Nostalgia client behavior)",
+			args: args{
+				b: []byte{
+					0x41, 0x4d, 0x41, 0x43, 0x3f, 0x3f, 0x3f, 0x3f, 0x3f, 0x3f, 0x3f, 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x09, 0x62, 0x65, 0x61, 0x72, 0x2e, 0x74, 0x69, 0x66, 0x66,
+				},
+			},
+			wantErr: assert.NoError,
+		},
+		{
+			name: "when zero length comment size is included",
+			args: args{
+				b: []byte{
+					0x41, 0x4d, 0x41, 0x43, 0x3f, 0x3f, 0x3f, 0x3f, 0x3f, 0x3f, 0x3f, 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x09, 0x62, 0x65, 0x61, 0x72, 0x2e, 0x74, 0x69, 0x66, 0x66, 0x00, 0x00,
+				},
+			},
+			wantErr: assert.NoError,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ffif := &FlatFileInformationFork{}
+			tt.wantErr(t, ffif.UnmarshalBinary(tt.args.b), fmt.Sprintf("UnmarshalBinary(%v)", tt.args.b))
+
+			spew.Dump(ffif)
+		})
+	}
+}