Merge pull request #270 from wneessen/feature/262_support-7bit-encoding

Add 7bit support for EML parsing

eml.go

@@ -207,6 +207,12 @@ func parseEMLBodyParts(parsedMsg *netmail.Message, bodybuf *bytes.Buffer, msg *M
 // parseEMLBodyPlain parses the mail body of plain type mails
 func parseEMLBodyPlain(mediatype string, parsedMsg *netmail.Message, bodybuf *bytes.Buffer, msg *Msg) error {
 	contentTransferEnc := parsedMsg.Header.Get(HeaderContentTransferEnc.String())
+	// According to RFC2045, if no Content-Transfer-Encoding is set, we can imply 7bit US-ASCII encoding
+	if contentTransferEnc == "" || strings.EqualFold(contentTransferEnc, EncodingUSASCII.String()) {
+		msg.SetEncoding(EncodingUSASCII)
+		msg.SetBodyString(ContentType(mediatype), bodybuf.String())
+		return nil
+	}
 	if strings.EqualFold(contentTransferEnc, NoEncoding.String()) {
 		msg.SetEncoding(NoEncoding)
 		msg.SetBodyString(ContentType(mediatype), bodybuf.String())
@@ -308,14 +314,22 @@ ReadNextPart:
 		}
 
 		switch {
+		case strings.EqualFold(mutliPartTransferEnc[0], EncodingUSASCII.String()):
+			part.SetEncoding(EncodingUSASCII)
+			part.SetContent(string(multiPartData))
+		case strings.EqualFold(mutliPartTransferEnc[0], NoEncoding.String()):
+			part.SetEncoding(NoEncoding)
+			part.SetContent(string(multiPartData))
 		case strings.EqualFold(mutliPartTransferEnc[0], EncodingB64.String()):
-			if err := handleEMLMultiPartBase64Encoding(multiPartData, part); err != nil {
+			part.SetEncoding(EncodingB64)
+			if err = handleEMLMultiPartBase64Encoding(multiPartData, part); err != nil {
 				return fmt.Errorf("failed to handle multipart base64 transfer-encoding: %w", err)
 			}
 		case strings.EqualFold(mutliPartTransferEnc[0], EncodingQP.String()):
+			part.SetEncoding(EncodingQP)
 			part.SetContent(string(multiPartData))
 		default:
-			return fmt.Errorf("unsupported Content-Transfer-Encoding")
+			return fmt.Errorf("unsupported Content-Transfer-Encoding: %s", mutliPartTransferEnc[0])
 		}
 
 		msg.parts = append(msg.parts, part)

eml_test.go

@@ -32,6 +32,29 @@ This is a test mail. Please do not reply to this. Also this line is very long so
 should be wrapped.
 
 
+Thank your for your business!
+The go-mail team
+
+--
+This is a signature`
+	exampleMailPlain7Bit = `Date: Wed, 01 Nov 2023 00:00:00 +0000
+MIME-Version: 1.0
+Message-ID: <[email protected]>
+Subject: Example mail // plain text without encoding
+User-Agent: go-mail v0.4.0 // https://github.com/wneessen/go-mail
+X-Mailer: go-mail v0.4.0 // https://github.com/wneessen/go-mail
+From: "Toni Tester" <[email protected]>
+To: <[email protected]>
+Cc: <[email protected]>
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 7bit
+
+Dear Customer,
+
+This is a test mail. Please do not reply to this. Also this line is very long so it
+should be wrapped.
+
+
 Thank your for your business!
 The go-mail team
 
@@ -525,6 +548,72 @@ hw22iFHl7YlpOmedZvtMTfQffXeXnvI+rTKNxguyvDKvB7U4qQAAAAlwSFlzAAALEwAACxMBAJqc
 GAAAABFJREFUCJljnMoAA0wMNGcCAEQrAKk9oHKhAAAAAElFTkSuQmCC
 
 --fe785e0384e2607697cc2ecb17cce003003bb7ca9112104f3e8ce727edb5--`
+	exampleMultiPart7BitBase64 = `Date: Wed, 01 Nov 2023 00:00:00 +0000
+MIME-Version: 1.0
+Message-ID: <[email protected]>
+Subject: Example mail // 7bit with base64 attachment
+User-Agent: go-mail v0.4.1 // https://github.com/wneessen/go-mail
+X-Mailer: go-mail v0.4.1 // https://github.com/wneessen/go-mail
+From: "Toni Tester" <[email protected]>
+To: <[email protected]>
+Cc: <[email protected]>
+Content-Type: multipart/mixed;
+ boundary="------------26A45336F6C6196BD8BBA2A2"
+
+This is a multi-part message in MIME format.
+--------------26A45336F6C6196BD8BBA2A2
+Content-Type: text/plain; charset=US-ASCII; format=flowed
+Content-Transfer-Encoding: 7bit
+
+testtest
+testtest
+testtest
+testtest
+testtest
+testtest
+
+--------------26A45336F6C6196BD8BBA2A2
+Content-Type: text/plain; charset=UTF-8;
+ name="testfile.txt"
+Content-Transfer-Encoding: base64
+Content-Disposition: attachment;
+ filename="testfile.txt"
+
+VGhpcyBpcyBhIHRlc3QgaW4gQmFzZTY0
+--------------26A45336F6C6196BD8BBA2A2--`
+	exampleMultiPart8BitBase64 = `Date: Wed, 01 Nov 2023 00:00:00 +0000
+MIME-Version: 1.0
+Message-ID: <[email protected]>
+Subject: Example mail // 8bit with base64 attachment
+User-Agent: go-mail v0.4.1 // https://github.com/wneessen/go-mail
+X-Mailer: go-mail v0.4.1 // https://github.com/wneessen/go-mail
+From: "Toni Tester" <[email protected]>
+To: <[email protected]>
+Cc: <[email protected]>
+Content-Type: multipart/mixed;
+ boundary="------------26A45336F6C6196BD8BBA2A2"
+
+This is a multi-part message in MIME format.
+--------------26A45336F6C6196BD8BBA2A2
+Content-Type: text/plain; charset=US-ASCII; format=flowed
+Content-Transfer-Encoding: 8bit
+
+testtest
+testtest
+testtest
+testtest
+testtest
+testtest
+
+--------------26A45336F6C6196BD8BBA2A2
+Content-Type: text/plain; charset=UTF-8;
+ name="testfile.txt"
+Content-Transfer-Encoding: base64
+Content-Disposition: attachment;
+ filename="testfile.txt"
+
+VGhpcyBpcyBhIHRlc3QgaW4gQmFzZTY0
+--------------26A45336F6C6196BD8BBA2A2--`
 )
 
 func TestEMLToMsgFromString(t *testing.T) {
@@ -534,6 +623,10 @@ func TestEMLToMsgFromString(t *testing.T) {
 		enc  string
 		sub  string
 	}{
+		{
+			"Plain text no encoding (7bit)", exampleMailPlain7Bit, "7bit",
+			"Example mail // plain text without encoding",
+		},
 		{
 			"Plain text no encoding", exampleMailPlainNoEnc, "8bit",
 			"Example mail // plain text without encoding",
@@ -866,6 +959,58 @@ func TestEMLToMsgFromStringMultipartMixedAlternativeRelated(t *testing.T) {
 	}
 }
 
+func TestEMLToMsgFromStringMultipartMixedWith7Bit(t *testing.T) {
+	wantSubject := "Example mail // 7bit with base64 attachment"
+	msg, err := EMLToMsgFromString(exampleMultiPart7BitBase64)
+	if err != nil {
+		t.Errorf("EML multipart mixed with 7bit: %s", err)
+	}
+	if subject := msg.GetGenHeader(HeaderSubject); len(subject) > 0 && !strings.EqualFold(subject[0], wantSubject) {
+		t.Errorf("EMLToMsgFromString of EML multipart mixed with 7bit: expected subject: %s,"+
+			" but got: %s", wantSubject, subject[0])
+	}
+	if len(msg.parts) != 1 {
+		t.Errorf("EMLToMsgFromString of EML multipart mixed with 7bit failed: expected 1 part, got: %d",
+			len(msg.parts))
+		return
+	}
+	if !strings.EqualFold(msg.parts[0].GetEncoding().String(), EncodingUSASCII.String()) {
+		t.Errorf("EMLToMsgFromString of EML multipart mixed with 7bit failed: expected encoding: %s, got %s",
+			EncodingUSASCII.String(), msg.parts[0].GetEncoding().String())
+	}
+	if len(msg.attachments) != 1 {
+		t.Errorf("EMLToMsgFromString of EML multipart mixed with 7bit failed: expected 1 attachment, got: %d",
+			len(msg.attachments))
+		return
+	}
+}
+
+func TestEMLToMsgFromStringMultipartMixedWith8Bit(t *testing.T) {
+	wantSubject := "Example mail // 8bit with base64 attachment"
+	msg, err := EMLToMsgFromString(exampleMultiPart8BitBase64)
+	if err != nil {
+		t.Errorf("EML multipart mixed with 8bit: %s", err)
+	}
+	if subject := msg.GetGenHeader(HeaderSubject); len(subject) > 0 && !strings.EqualFold(subject[0], wantSubject) {
+		t.Errorf("EMLToMsgFromString of EML multipart mixed with 8bit: expected subject: %s,"+
+			" but got: %s", wantSubject, subject[0])
+	}
+	if len(msg.parts) != 1 {
+		t.Errorf("EMLToMsgFromString of EML multipart mixed with 8bit failed: expected 1 part, got: %d",
+			len(msg.parts))
+		return
+	}
+	if !strings.EqualFold(msg.parts[0].GetEncoding().String(), NoEncoding.String()) {
+		t.Errorf("EMLToMsgFromString of EML multipart mixed with 8bit failed: expected encoding: %s, got %s",
+			NoEncoding.String(), msg.parts[0].GetEncoding().String())
+	}
+	if len(msg.attachments) != 1 {
+		t.Errorf("EMLToMsgFromString of EML multipart mixed with 8bit failed: expected 1 attachment, got: %d",
+			len(msg.attachments))
+		return
+	}
+}
+
 // stringToTempFile is a helper method that will create a temporary file form a give data string
 func stringToTempFile(data, name string) (string, string, error) {
 	tempDir, err := os.MkdirTemp("", fmt.Sprintf("*-%s", name))

encoding.go

@@ -27,6 +27,9 @@ const (
 	// EncodingQP represents the "quoted-printable" encoding as specified in RFC 2045.
 	EncodingQP Encoding = "quoted-printable"
 
+	// EncodingUSASCII represents encoding with only US-ASCII characters (aka 7Bit)
+	EncodingUSASCII Encoding = "7bit"
+
 	// NoEncoding avoids any character encoding (except of the mail headers)
 	NoEncoding Encoding = "8bit"
 )

encoding_test.go

@@ -16,6 +16,7 @@ func TestEncoding_String(t *testing.T) {
 		{"Encoding: Base64", EncodingB64, "base64"},
 		{"Encoding: QP", EncodingQP, "quoted-printable"},
 		{"Encoding: None/8bit", NoEncoding, "8bit"},
+		{"Encoding: US-ASCII/7bit", EncodingUSASCII, "7bit"},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {