feat: s/mime singing supports quoted printable encoding, also added tests

msg.go

@@ -2184,8 +2184,11 @@ func (m *Msg) signMessage(msg *Msg) (*Msg, error) {
 
 // createSignaturePart creates an additional part that be used for storing the S/MIME signature of the given body
 func (m *Msg) createSignaturePart(encoding Encoding, contentType ContentType, charSet Charset, body []byte) (*Part, error) {
-	message := m.sMime.prepareMessage(encoding, contentType, charSet, body)
-	signedMessage, err := m.sMime.signMessage(message)
+	message, err := m.sMime.prepareMessage(encoding, contentType, charSet, body)
+	if err != nil {
+		return nil, err
+	}
+	signedMessage, err := m.sMime.signMessage(*message)
 	if err != nil {
 		return nil, err
 	}

smime.go

@@ -13,6 +13,7 @@ import (
 	"encoding/pem"
 	"errors"
 	"fmt"
+	"mime/quotedprintable"
 	"strings"
 )
 
@@ -119,8 +120,32 @@ func (sm *SMime) signMessage(message string) (*string, error) {
 }
 
 // createMessage prepares the message that will be used for the sign method later
-func (sm *SMime) prepareMessage(encoding Encoding, contentType ContentType, charset Charset, body []byte) string {
-	return fmt.Sprintf("Content-Transfer-Encoding: %v\r\nContent-Type: %v; charset=%v\r\n\r\n%v", encoding, contentType, charset, string(body))
+func (sm *SMime) prepareMessage(encoding Encoding, contentType ContentType, charset Charset, body []byte) (*string, error) {
+	encodedMessage, err := sm.encodeMessage(encoding, string(body))
+	if err != nil {
+		return nil, err
+	}
+	preparedMessage := fmt.Sprintf("Content-Transfer-Encoding: %v\r\nContent-Type: %v; charset=%v\r\n\r\n%v", encoding, contentType, charset, *encodedMessage)
+	return &preparedMessage, nil
+}
+
+// encodeMessage encodes the message with the given encoding
+func (sm *SMime) encodeMessage(encoding Encoding, message string) (*string, error) {
+	if encoding != EncodingQP {
+		return &message, nil
+	}
+
+	buffer := bytes.Buffer{}
+	writer := quotedprintable.NewWriter(&buffer)
+	if _, err := writer.Write([]byte(message)); err != nil {
+		return nil, err
+	}
+	if err := writer.Close(); err != nil {
+		return nil, err
+	}
+	encodedMessage := buffer.String()
+
+	return &encodedMessage, nil
 }
 
 // encodeToPEM uses the method pem.Encode from the standard library but cuts the typical PEM preamble

smime_test.go

@@ -121,19 +121,109 @@ func TestPrepareMessage(t *testing.T) {
 	contentType := TypeTextPlain
 	charset := CharsetUTF8
 	body := []byte("This is the body!")
-	result := sMime.prepareMessage(encoding, contentType, charset, body)
+	result, err := sMime.prepareMessage(encoding, contentType, charset, body)
+	if err != nil {
+		t.Errorf("Error preparing message: %s", err)
+	}
 
-	if !strings.Contains(result, encoding.String()) {
-		t.Errorf("createMessage() did not return the correct encoding")
+	if !strings.Contains(*result, encoding.String()) {
+		t.Errorf("prepareMessage() did not return the correct encoding")
 	}
-	if !strings.Contains(result, contentType.String()) {
-		t.Errorf("createMessage() did not return the correct contentType")
+	if !strings.Contains(*result, contentType.String()) {
+		t.Errorf("prepareMessage() did not return the correct contentType")
 	}
-	if !strings.Contains(result, string(body)) {
-		t.Errorf("createMessage() did not return the correct body")
+	if !strings.Contains(*result, string(body)) {
+		t.Errorf("prepareMessage() did not return the correct body")
 	}
-	if result != fmt.Sprintf("Content-Transfer-Encoding: %s\r\nContent-Type: %s; charset=%s\r\n\r\n%s", encoding, contentType, charset, string(body)) {
-		t.Errorf("createMessage() did not sucessfully create the message")
+	if *result != fmt.Sprintf("Content-Transfer-Encoding: %s\r\nContent-Type: %s; charset=%s\r\n\r\n%s", encoding, contentType, charset, string(body)) {
+		t.Errorf("prepareMessage() did not sucessfully create the message")
+	}
+}
+
+// TestPrepareMessage_QuotedPrintable tests the prepareMessage method with quoted printable encoding
+func TestPrepareMessage_QuotedPrintable(t *testing.T) {
+	privateKey, certificate, intermediateCertificate, err := getDummyRSACryptoMaterial()
+	if err != nil {
+		t.Errorf("Error getting dummy crypto material: %s", err)
+	}
+
+	sMime, err := newSMimeWithRSA(privateKey, certificate, intermediateCertificate)
+	if err != nil {
+		t.Errorf("Error creating new SMime from keyPair: %s", err)
+	}
+
+	body := "This is the body with special chars like äöü ÄÖÜ ß!"
+	quotedPrintableBody := "This is the body with special chars like =C3=A4=C3=B6=C3=BC =C3=84=C3=96=C3=\r\n=9C =C3=9F!"
+	encoding := EncodingQP
+	contentType := TypeTextPlain
+	charset := CharsetUTF8
+	result, err := sMime.prepareMessage(encoding, contentType, charset, []byte(body))
+	if err != nil {
+		t.Errorf("Error preparing message: %s", err)
+	}
+
+	if !strings.Contains(*result, encoding.String()) {
+		t.Errorf("prepareMessage() did not return the correct encoding")
+	}
+	if !strings.Contains(*result, contentType.String()) {
+		t.Errorf("prepareMessage() did not return the correct contentType")
+	}
+	if !strings.Contains(*result, quotedPrintableBody) {
+		t.Errorf("prepareMessage() did not return the correct body")
+	}
+	if *result != fmt.Sprintf("Content-Transfer-Encoding: %s\r\nContent-Type: %s; charset=%s\r\n\r\n%s", encoding, contentType, charset, quotedPrintableBody) {
+		t.Errorf("prepareMessage() did not sucessfully create the message")
+	}
+}
+
+// TestEncodeMessage tests the TestEncodeMessage method without any encoding
+func TestEncodeMessage(t *testing.T) {
+	body := "This is the body with special chars like äöü ÄÖÜ ß!"
+	encoding := EncodingUSASCII
+
+	privateKey, certificate, intermediateCertificate, err := getDummyRSACryptoMaterial()
+	if err != nil {
+		t.Errorf("Error getting dummy crypto material: %s", err)
+	}
+
+	sMime, err := newSMimeWithRSA(privateKey, certificate, intermediateCertificate)
+	if err != nil {
+		t.Errorf("Error creating new SMime from keyPair: %s", err)
+	}
+
+	result, err := sMime.encodeMessage(encoding, body)
+	if err != nil {
+		t.Errorf("Error preparing message: %s", err)
+	}
+
+	if *result != body {
+		t.Errorf("encodeMessage() did not return the correct encoded message: %s", *result)
+	}
+}
+
+// TestEncodeMessage_QuotedPrintable tests the TestEncodeMessage method with quoted printable body
+func TestEncodeMessage_QuotedPrintable(t *testing.T) {
+	body := "This is the body with special chars like äöü ÄÖÜ ß!"
+	quotedPrintableBody := "This is the body with special chars like =C3=A4=C3=B6=C3=BC =C3=84=C3=96=C3=\r\n=9C =C3=9F!"
+	encoding := EncodingQP
+
+	privateKey, certificate, intermediateCertificate, err := getDummyRSACryptoMaterial()
+	if err != nil {
+		t.Errorf("Error getting dummy crypto material: %s", err)
+	}
+
+	sMime, err := newSMimeWithRSA(privateKey, certificate, intermediateCertificate)
+	if err != nil {
+		t.Errorf("Error creating new SMime from keyPair: %s", err)
+	}
+
+	result, err := sMime.encodeMessage(encoding, body)
+	if err != nil {
+		t.Errorf("Error preparing message: %s", err)
+	}
+
+	if *result != quotedPrintableBody {
+		t.Errorf("encodeMessage() did not return the correct encoded message: %s", *result)
 	}
 }