From f256d205ed933769a1018ed428903d2f95f9d121 Mon Sep 17 00:00:00 2001
From: Ralph Slooten <axllent@gmail.com>
Date: Wed, 18 Oct 2023 17:40:40 +1300
Subject: [PATCH] Feature: Reset message date on release (#194)

When releasing a message the date header is now updated with the current date & time.
---
 internal/tools/message.go | 46 ++++++++++++++++++++++++++++++++++++---
 server/apiv1/api.go       | 18 ++++++++++++---
 2 files changed, 58 insertions(+), 6 deletions(-)

diff --git a/internal/tools/message.go b/internal/tools/message.go
index b28cc1893..02d0ff86c 100644
--- a/internal/tools/message.go
+++ b/internal/tools/message.go
@@ -11,8 +11,7 @@ import (
 )
 
 // RemoveMessageHeaders scans a message for headers, if found them removes them.
-// It will only remove a single instance of any header, and is intended to remove
-// Bcc & Message-Id.
+// It will only remove a single instance of any given message header.
 func RemoveMessageHeaders(msg []byte, headers []string) ([]byte, error) {
 	reader := bytes.NewReader(msg)
 	m, err := mail.ReadMessage(reader)
@@ -49,7 +48,7 @@ func RemoveMessageHeaders(msg []byte, headers []string) ([]byte, error) {
 			}
 
 			if len(hdr) > 0 {
-				logger.Log().Debugf("[release] removing %s header", hdr)
+				logger.Log().Debugf("[release] removed %s header", hdr)
 				msg = bytes.Replace(msg, hdr, []byte(""), 1)
 			}
 		}
@@ -57,3 +56,44 @@ func RemoveMessageHeaders(msg []byte, headers []string) ([]byte, error) {
 
 	return msg, nil
 }
+
+// UpdateMessageHeader scans a message for a header and updates its value if found.
+func UpdateMessageHeader(msg []byte, header, value string) ([]byte, error) {
+	reader := bytes.NewReader(msg)
+	m, err := mail.ReadMessage(reader)
+	if err != nil {
+		return nil, err
+	}
+
+	if m.Header.Get(header) != "" {
+		reBlank := regexp.MustCompile(`^\s+`)
+		reHdr := regexp.MustCompile(`(?i)^` + regexp.QuoteMeta(header+":"))
+
+		scanner := bufio.NewScanner(bytes.NewReader(msg))
+		found := false
+		hdr := []byte("")
+		for scanner.Scan() {
+			line := scanner.Bytes()
+			if !found && reHdr.Match(line) {
+				// add the first line starting with <header>:
+				hdr = append(hdr, line...)
+				hdr = append(hdr, []byte("\r\n")...)
+				found = true
+			} else if found && reBlank.Match(line) {
+				// add any following lines starting with a whitespace (tab or space)
+				hdr = append(hdr, line...)
+				hdr = append(hdr, []byte("\r\n")...)
+			} else if found {
+				// stop scanning, we have the full <header>
+				break
+			}
+		}
+
+		if len(hdr) > 0 {
+			logger.Log().Debugf("[release] replaced %s header", hdr)
+			msg = bytes.Replace(msg, hdr, []byte(header+": "+value+"\r\n"), 1)
+		}
+	}
+
+	return msg, nil
+}
diff --git a/server/apiv1/api.go b/server/apiv1/api.go
index 5ad4951f3..1afd70342 100644
--- a/server/apiv1/api.go
+++ b/server/apiv1/api.go
@@ -9,6 +9,7 @@ import (
 	"net/mail"
 	"strconv"
 	"strings"
+	"time"
 
 	"github.com/axllent/mailpit/config"
 	"github.com/axllent/mailpit/internal/htmlcheck"
@@ -632,7 +633,7 @@ func ReleaseMessage(w http.ResponseWriter, r *http.Request) {
 		from = senders[0].Address
 	}
 
-	msg, err = tools.RemoveMessageHeaders(msg, []string{"Bcc", "Message-Id"})
+	msg, err = tools.RemoveMessageHeaders(msg, []string{"Bcc"})
 	if err != nil {
 		httpError(w, err.Error())
 		return
@@ -652,10 +653,21 @@ func ReleaseMessage(w http.ResponseWriter, r *http.Request) {
 		from = config.SMTPRelayConfig.ReturnPath
 	}
 
+	// update message date
+	msg, err = tools.UpdateMessageHeader(msg, "Date", time.Now().Format(time.RFC1123Z))
+	if err != nil {
+		httpError(w, err.Error())
+		return
+	}
+
 	// generate unique ID
 	uid := uuid.New().String() + "@mailpit"
-	// add unique ID
-	msg = append([]byte("Message-Id: <"+uid+">\r\n"), msg...)
+	// update Message-Id with unique ID
+	msg, err = tools.UpdateMessageHeader(msg, "Message-Id", "<"+uid+">")
+	if err != nil {
+		httpError(w, err.Error())
+		return
+	}
 
 	if err := smtpd.Send(from, tos, msg); err != nil {
 		logger.Log().Errorf("[smtp] error sending message: %s", err.Error())