fix(BRIDGE-256): fix reversed order of headers with multiple values.

pkg/message/build.go

@@ -531,11 +531,12 @@ func toMessageHeader(hdr proton.Headers) message.Header {
 	// go-message's message.Header are in reversed order (you should only add fields at the top, so storing in reverse order offer faster performances).
 	for i := len(hdr.Order) - 1; i >= 0; i-- {
 		key := hdr.Order[i]
-		for _, val := range hdr.Values[key] {
+		values := hdr.Values[key]
+		for j := len(values) - 1; j >= 0; j-- {
 			// Using AddRaw instead of Add to save key-value pair as byte buffer within Header.
 			// This buffer is used latter on in message writer to construct message and avoid crash
 			// when key length is more than 76 characters long.
-			res.AddRaw([]byte(key + ": " + val + "\r\n"))
+			res.AddRaw([]byte(key + ": " + values[j] + "\r\n"))
 		}
 	}
 

pkg/message/build_framework_test.go

@@ -101,6 +101,11 @@ func newTestMessageFromRFC822(t *testing.T, literal []byte) proton.Message {
 	var parsedHeaders proton.Headers
 	parsedHeaders.Values = make(map[string][]string)
 	h.Entries(func(key, val string) {
+		currentVal, ok := parsedHeaders.Values[key]
+		if ok {
+			parsedHeaders.Values[key] = append(currentVal, val)
+			return
+		}
 		parsedHeaders.Values[key] = []string{val}
 		parsedHeaders.Order = append(parsedHeaders.Order, key)
 	})

pkg/message/header_test.go

@@ -145,6 +145,9 @@ From: Dummy Recipient <dummy@proton.me>
 Date: Tue, 15 Oct 2024 07:54:39 +0000
 Mime-Version: 1.0
 Content-Type: multipart/mixed;boundary=---------------------a136fc3851075ca3f022f5c3ec6bf8f5
+X-Attached: image1.jpg
+X-Attached: image2.jpg
+X-Attached: image3.jpg
 Message-Id: <1rYR51zNVZdyCXVvAZ8C9N8OaBg4wO_wg6VlSoLK_Mv-2AaiF5UL-vE_tIZ6FdYP8ylsuV3fpaKUpVwuUcnQ6ql_83aEgZvfC5QcZbind1k=@proton.me>
 X-Pm-Spamscore: 0
 Received: from mail.protonmail.ch by mail.protonmail.ch; Tue, 15 Oct 2024 07:54:43 +0000
@@ -178,7 +181,7 @@ lorem`)
 	lines := strings.Split(str, "\r\n")
 
 	// Check we have the expected order
-	require.Equal(t, len(lines), 17)
+	require.Equal(t, len(lines), 20)
 
 	// The fields added or modified are at the top
 	require.True(t, strings.HasPrefix(lines[0], "Content-Type: multipart/mixed;boundary=")) // we changed the boundary
@@ -194,10 +197,13 @@ lorem`)
 	require.Equal(t, `Subject: header test`, lines[8])
 	require.Equal(t, `Date: Tue, 15 Oct 2024 07:54:39 +0000`, lines[9])
 	require.Equal(t, `Mime-Version: 1.0`, lines[10])
-	require.Equal(t, `Message-Id: <1rYR51zNVZdyCXVvAZ8C9N8OaBg4wO_wg6VlSoLK_Mv-2AaiF5UL-vE_tIZ6FdYP8ylsuV3fpaKUpVwuUcnQ6ql_83aEgZvfC5QcZbind1k=@proton.me>`, lines[11])
+	require.Equal(t, `X-Attached: image1.jpg`, lines[11])
-	require.Equal(t, `X-Pm-Spamscore: 0`, lines[12])
+	require.Equal(t, `X-Attached: image2.jpg`, lines[12])
-	require.Equal(t, `Received: from mail.protonmail.ch by mail.protonmail.ch; Tue, 15 Oct 2024 07:54:43 +0000`, lines[13])
+	require.Equal(t, `X-Attached: image3.jpg`, lines[13])
-	require.Equal(t, `X-Original-To: test@proton.me`, lines[14])
+	require.Equal(t, `Message-Id: <1rYR51zNVZdyCXVvAZ8C9N8OaBg4wO_wg6VlSoLK_Mv-2AaiF5UL-vE_tIZ6FdYP8ylsuV3fpaKUpVwuUcnQ6ql_83aEgZvfC5QcZbind1k=@proton.me>`, lines[14])
-	require.Equal(t, `Return-Path: <dummy@proton.me>`, lines[15])
+	require.Equal(t, `X-Pm-Spamscore: 0`, lines[15])
-	require.Equal(t, `Delivered-To: test@proton.me`, lines[16])
+	require.Equal(t, `Received: from mail.protonmail.ch by mail.protonmail.ch; Tue, 15 Oct 2024 07:54:43 +0000`, lines[16])
+	require.Equal(t, `X-Original-To: test@proton.me`, lines[17])
+	require.Equal(t, `Return-Path: <dummy@proton.me>`, lines[18])
+	require.Equal(t, `Delivered-To: test@proton.me`, lines[19])
 }