feat(GODT-906): support rfc2047-encoded content transfer encodings

pkg/message/parser.go

@@ -45,6 +45,11 @@ func Parse(r io.Reader, key, keyName string) (m *pmapi.Message, mimeBody, plainB
 		return
 	}
 
+	if err = convertEncodedTransferEncoding(p); err != nil {
+		err = errors.Wrap(err, "failed to convert encoded transfer encodings")
+		return
+	}
+
 	if err = convertForeignEncodings(p); err != nil {
 		err = errors.Wrap(err, "failed to convert foreign encodings")
 		return
@@ -89,6 +94,30 @@ func Parse(r io.Reader, key, keyName string) (m *pmapi.Message, mimeBody, plainB
 	return m, mimeBodyBuffer.String(), plainBody, attReaders, nil
 }
 
+// convertEncodedTransferEncoding decodes any RFC2047-encoded content transfer encodings.
+// Such content transfer encodings go against RFC but still exist in the wild anyway.
+func convertEncodedTransferEncoding(p *parser.Parser) error {
+	logrus.Trace("Converting encoded transfer encoding")
+
+	return p.NewWalker().
+		RegisterDefaultHandler(func(p *parser.Part) error {
+			encoding := p.Header.Get("Content-Transfer-Encoding")
+			if encoding == "" {
+				return nil
+			}
+
+			dec, err := pmmime.WordDec.DecodeHeader(encoding)
+			if err != nil {
+				return err
+			}
+
+			p.Header.Set("Content-Transfer-Encoding", dec)
+
+			return nil
+		}).
+		Walk()
+}
+
 func convertForeignEncodings(p *parser.Parser) error {
 	logrus.Trace("Converting foreign encodings")
 
@@ -104,12 +133,11 @@ func convertForeignEncodings(p *parser.Parser) error {
 			return p.ConvertToUTF8()
 		}).
 		RegisterDefaultHandler(func(p *parser.Part) error {
-			t, params, _ := p.ContentType()
 			// multipart/alternative, for example, can contain extra charset.
-			if params != nil && params["charset"] != "" {
+			if _, params, _ := p.ContentType(); params != nil && params["charset"] != "" {
 				return p.ConvertToUTF8()
 			}
-			logrus.WithField("type", t).Trace("Not converting part to utf-8")
+
 			return nil
 		}).
 		Walk()

pkg/message/parser/parser.go

@@ -22,6 +22,7 @@ import (
 	"io/ioutil"
 
 	"github.com/emersion/go-message"
+	"github.com/sirupsen/logrus"
 )
 
 type Parser struct {
@@ -33,8 +34,15 @@ func New(r io.Reader) (*Parser, error) {
 	p := new(Parser)
 
 	entity, err := message.Read(newEndOfMailTrimmer(r))
-	if err != nil && !message.IsUnknownCharset(err) {
-		return nil, err
+	if err != nil {
+		switch {
+		case message.IsUnknownCharset(err):
+			logrus.WithError(err).Warning("Message has an unknown charset")
+		case message.IsUnknownEncoding(err):
+			logrus.WithError(err).Warning("Message has an unknown encoding")
+		default:
+			return nil, err
+		}
 	}
 
 	if err := p.parseEntity(entity); err != nil {

pkg/message/parser_test.go

@@ -480,6 +480,37 @@ func TestParseWithTrailingEndOfMailIndicator(t *testing.T) {
 	assert.Equal(t, "boo!", plainBody)
 }
 
+func TestParseEncodedContentType(t *testing.T) {
+	f := getFileReader("rfc2047-content-transfer-encoding.eml")
+
+	m, _, plainBody, _, err := Parse(f, "", "")
+	require.NoError(t, err)
+
+	assert.Equal(t, `"Sender" <sender@sender.com>`, m.Sender.String())
+	assert.Equal(t, `<user@somewhere.org>`, m.ToList[0].String())
+
+	assert.Equal(t, "bodybodybody\n", plainBody)
+}
+
+func TestParseNonEncodedContentType(t *testing.T) {
+	f := getFileReader("non-encoded-content-transfer-encoding.eml")
+
+	m, _, plainBody, _, err := Parse(f, "", "")
+	require.NoError(t, err)
+
+	assert.Equal(t, `"Sender" <sender@sender.com>`, m.Sender.String())
+	assert.Equal(t, `<user@somewhere.org>`, m.ToList[0].String())
+
+	assert.Equal(t, "bodybodybody\n", plainBody)
+}
+
+func TestParseEncodedContentTypeBad(t *testing.T) {
+	f := getFileReader("rfc2047-content-transfer-encoding-bad.eml")
+
+	_, _, _, _, err := Parse(f, "", "") // nolint[dogsled]
+	require.Error(t, err)
+}
+
 func getFileReader(filename string) io.Reader {
 	f, err := os.Open(filepath.Join("testdata", filename))
 	if err != nil {

pkg/message/testdata/non-encoded-content-transfer-encoding.eml

@@ -0,0 +1,10 @@
+To: user@somewhere.org
+Subject: =?utf-8?Q?aoeuaoeuaoeu?=
+Date: Sat, 16 Jun 2020 17:36:02 +0200
+MIME-Version: 1.0
+Content-Type: text/plain;
+ charset="utf-8"
+Content-Transfer-Encoding: 8bit
+From: =?utf-8?Q?Sender?= <sender@sender.com>
+
+bodybodybody

pkg/message/testdata/rfc2047-content-transfer-encoding-bad.eml

@@ -0,0 +1,10 @@
+To: user@somewhere.org
+Subject: =?utf-8?Q?aoeuaoeuaoeu?=
+Date: Sat, 16 Jun 2020 17:36:02 +0200
+MIME-Version: 1.0
+Content-Type: text/plain;
+ charset="utf-8"
+Content-Transfer-Encoding: =?utf-8?Q?8bit
+From: =?utf-8?Q?Sender?= <sender@sender.com>
+
+bodybodybody

pkg/message/testdata/rfc2047-content-transfer-encoding.eml

@@ -0,0 +1,10 @@
+To: user@somewhere.org
+Subject: =?utf-8?Q?aoeuaoeuaoeu?=
+Date: Sat, 16 Jun 2020 17:36:02 +0200
+MIME-Version: 1.0
+Content-Type: text/plain;
+ charset="utf-8"
+Content-Transfer-Encoding: =?utf-8?Q?8bit?=
+From: =?utf-8?Q?Sender?= <sender@sender.com>
+
+bodybodybody

unreleased.md

@@ -5,6 +5,7 @@ Changelog [format](http://keepachangelog.com/en/1.0.0/)
 ## Unreleased
 
 ### Added
+* GODT-906 Handle RFC2047-encoded content transfer encoding values.
 
 ### Changed
 * GODT-893 Bump go-rfc5322 dependency to v0.2.1 to properly detect syntax errors during parsing.