From 611c25799d994db44bdad4490b7c285380dc51d2 Mon Sep 17 00:00:00 2001
From: William Poussier <wI2L@users.noreply.github.com>
Date: Wed, 13 Sep 2017 14:44:39 +0200
Subject: [PATCH] executors/imap: proper support for Content-Transfer-Encoding
 header. (#84)

---
 executors/imap/decode.go | 97 ++++++++++++++++++++++------------------
 1 file changed, 54 insertions(+), 43 deletions(-)

diff --git a/executors/imap/decode.go b/executors/imap/decode.go
index 5c7408e2..efef8421 100644
--- a/executors/imap/decode.go
+++ b/executors/imap/decode.go
@@ -3,6 +3,7 @@ package imap
 import (
 	"bytes"
 	"crypto/md5"
+	"encoding/base64"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -34,61 +35,71 @@ func hash(in string) string {
 
 func extract(rsp imap.Response, l venom.Logger) (*Mail, error) {
 	tm := &Mail{}
-	var params map[string]string
 
 	header := imap.AsBytes(rsp.MessageInfo().Attrs["RFC822.HEADER"])
 	tm.UID = imap.AsNumber((rsp.MessageInfo().Attrs["UID"]))
 	body := imap.AsBytes(rsp.MessageInfo().Attrs["RFC822.TEXT"])
-	if mmsg, _ := mail.ReadMessage(bytes.NewReader(header)); mmsg != nil {
-		var errds error
-		tm.Subject, errds = decodeHeader(mmsg, "Subject")
-		if errds != nil {
-			log.Warnf("Cannot decode subject: %s", errds)
-			return nil, nil
-		}
-		var errdf error
-		tm.From, errdf = decodeHeader(mmsg, "From")
-		if errdf != nil {
-			log.Warnf("Cannot decode from: %s", errdf)
-			return nil, nil
-		}
 
-		var errpm error
-		_, params, errpm = mime.ParseMediaType(mmsg.Header.Get("Content-Type"))
-		if errpm != nil {
-			return nil, fmt.Errorf("Error while read Content-Type:%s", errpm)
-		}
+	mmsg, err := mail.ReadMessage(bytes.NewReader(header))
+	if err != nil {
+		return nil, err
+	}
+	tm.Subject, err = decodeHeader(mmsg, "Subject")
+	if err != nil {
+		log.Warnf("Cannot decode subject: %s", err)
+		return nil, nil
+	}
+	tm.From, err = decodeHeader(mmsg, "From")
+	if err != nil {
+		log.Warnf("Cannot decode from: %s", err)
+		return nil, nil
 	}
 
-	r := quotedprintable.NewReader(bytes.NewReader(body))
-	bodya, errra := ioutil.ReadAll(r)
-	if errra == nil {
-		tm.Body = string(bodya)
-		return tm, nil
-	} else if len(params) > 0 {
-		r := bytes.NewReader(body)
-		mr := multipart.NewReader(r, params["boundary"])
-		for {
-			p, err := mr.NextPart()
-			if err == io.EOF {
-				continue
-			}
-			if err != nil {
-				l.Debugf("Error while read Part:%s", err)
+	encoding := mmsg.Header.Get("Content-Transfer-Encoding")
+	var r io.Reader = bytes.NewReader(body)
+	switch encoding {
+	case "7bit", "8bit", "binary":
+		// noop, reader already initialized.
+	case "quoted-printable":
+		r = quotedprintable.NewReader(r)
+	case "base64":
+		r = base64.NewDecoder(base64.StdEncoding, r)
+	}
+	l.Debugf("Mail Content-Transfer-Encoding is %s ", encoding)
+
+	contentType, params, err := mime.ParseMediaType(mmsg.Header.Get("Content-Type"))
+	if err != nil {
+		return nil, fmt.Errorf("Error while reading Content-Type:%s", err)
+	}
+	if contentType == "multipart/mixed" || contentType == "multipart/alternative" {
+		if boundary, ok := params["boundary"]; ok {
+			mr := multipart.NewReader(r, boundary)
+			for {
+				p, errm := mr.NextPart()
+				if errm == io.EOF {
+					continue
+				}
+				if errm != nil {
+					l.Debugf("Error while read Part:%s", err)
+					break
+				}
+				slurp, errm := ioutil.ReadAll(p)
+				if errm != nil {
+					l.Debugf("Error while ReadAll Part:%s", err)
+					continue
+				}
+				tm.Body = string(slurp)
 				break
 			}
-			slurp, err := ioutil.ReadAll(p)
-			if err != nil {
-				l.Debugf("Error while ReadAll Part:%s", err)
-				continue
-			}
-			tm.Body = string(slurp)
-			break
+		}
+	} else {
+		body, err = ioutil.ReadAll(r)
+		if err != nil {
+			return nil, err
 		}
 	}
-
 	if tm.Body == "" {
-		tm.Body = string(bodya)
+		tm.Body = string(body)
 	}
 	return tm, nil
 }