Fix: Parsing of CID inline attachments

envelope.go

@@ -305,12 +305,12 @@ func parseMultiPartBody(root *Part, e *Envelope) error {
 
 	// Locate attachments
 	e.Attachments = root.BreadthMatchAll(func(p *Part) bool {
-		return p.Disposition == cdAttachment || p.ContentType == ctAppOctetStream
+		return (p.Disposition == cdAttachment || p.ContentType == ctAppOctetStream) && p.ContentID == "" && p.FileName != ""
 	})
 
 	// Locate inlines
 	e.Inlines = root.BreadthMatchAll(func(p *Part) bool {
-		return p.Disposition == cdInline && !strings.HasPrefix(p.ContentType, ctMultipartPrefix)
+		return p.Disposition == cdInline && !strings.HasPrefix(p.ContentType, ctMultipartPrefix) && p.ContentID != ""
 	})
 
 	// Locate others parts not considered in attachments or inlines

envelope_fuzz_test.go

@@ -1,5 +1,4 @@
 //go:build go1.18
-// +build go1.18
 
 package enmime
 

error_test.go

@@ -3,6 +3,7 @@ package enmime
 import (
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -117,16 +118,16 @@ func TestErrorEnvelopeWarnings(t *testing.T) {
 				}
 			}
 			if !satisfied {
-				var errorList string
+				var errorList strings.Builder
 				for _, perr := range e.Errors {
-					errorList += perr.Error()
-					errorList += "\n"
+					errorList.WriteString(perr.Error())
+					errorList.WriteString("\n")
 				}
 				t.Errorf(
 					"File %q should have error of type %q, got these instead:\n%s",
 					tt.filename,
 					tt.perror,
-					errorList)
+					errorList.String())
 			}
 		})
 	}

internal/textproto/reader.go

@@ -273,6 +273,8 @@ func (r *Reader) ReadCodeLine(expectCode int) (code int, message string, err err
 func (r *Reader) ReadResponse(expectCode int) (code int, message string, err error) {
 	code, continued, message, err := r.readCodeLine(expectCode)
 	multi := continued
+	var messageBuilder strings.Builder
+	messageBuilder.WriteString(message)
 	for continued {
 		line, err := r.ReadLine()
 		if err != nil {
@@ -283,12 +285,15 @@ func (r *Reader) ReadResponse(expectCode int) (code int, message string, err err
 		var moreMessage string
 		code2, continued, moreMessage, err = parseCodeLine(line, 0)
 		if err != nil || code2 != code {
-			message += "\n" + strings.TrimRight(line, "\r\n")
+			messageBuilder.WriteString("\n")
+			messageBuilder.WriteString(strings.TrimRight(line, "\r\n"))
 			continued = true
 			continue
 		}
-		message += "\n" + moreMessage
+		messageBuilder.WriteString("\n")
+		messageBuilder.WriteString(moreMessage)
 	}
+	message = messageBuilder.String()
 	if err != nil && multi && message != "" {
 		// replace one line error message with all lines (full message)
 		err = &textproto.Error{Code: code, Msg: message}

internal/textproto/textproto.go

@@ -26,6 +26,7 @@ package textproto
 
 import (
 	"bufio"
+	"context"
 	"io"
 	"net"
 )
@@ -59,7 +60,8 @@ func (c *Conn) Close() error {
 // Dial connects to the given address on the given network using net.Dial
 // and then returns a new Conn for the connection.
 func Dial(network, addr string) (*Conn, error) {
-	c, err := net.Dial(network, addr)
+	d := &net.Dialer{}
+	c, err := d.DialContext(context.Background(), network, addr)
 	if err != nil {
 		return nil, err
 	}

testdata/mail/inlinemultipart.raw

@@ -30,9 +30,9 @@ cmNlIChXZUpYRnh
 
 --0__=4EBB0828DFD318FF8f9e8a93df938690918c4EBB0828DFD318FF
 Content-Type: text/plain; name="test.txt"; name="test.txt"
-Content-Disposition: inline
 Content-Transfer-Encoding: 7bit
-Content-Disposition: attachment; filename="test.txt"
+Content-Disposition: inline; filename="test.txt"
+Content-Id: <8B8481A2-25CA-4886-9B5A-8EB9115DD064@skynet>
 
 Text attachment.