From 2bba7b902baa29e58b8c4ce76d150c25e111ebb5 Mon Sep 17 00:00:00 2001
From: Winni Neessen <wn@neessen.net>
Date: Tue, 17 Oct 2023 10:41:42 +0200
Subject: [PATCH] Updated error handling and encoding comparison in EML parsing

This commit changes the usage of error value and improves the string comparison for encoding types in EML file parsing. It ensures file closure after read operations to avoid memory leaks. Error messages are made dynamic for improved error reporting. Comments on function has also been made more descriptive.
---
 eml.go | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/eml.go b/eml.go
index 7dd3686..110f831 100644
--- a/eml.go
+++ b/eml.go
@@ -31,10 +31,10 @@ func EMLToMsg(fp string) (*Msg, error) {
 		return m, fmt.Errorf("failed to parse EML file: %w", err)
 	}
 
-	if err := parseEMLHeaders(&pm.Header, m); err != nil {
+	if err = parseEMLHeaders(&pm.Header, m); err != nil {
 		return m, fmt.Errorf("failed to parse EML headers: %w", err)
 	}
-	if err := parseEMLBodyParts(pm, mbbuf, m); err != nil {
+	if err = parseEMLBodyParts(pm, mbbuf, m); err != nil {
 		return m, fmt.Errorf("failed to parse EML body parts: %w", err)
 	}
 
@@ -59,6 +59,10 @@ func readEML(fp string) (*nm.Message, *bytes.Buffer, error) {
 	if _, err = buf.ReadFrom(pm.Body); err != nil {
 		return nil, nil, err
 	}
+
+	if err = fh.Close(); err != nil {
+		return nil, nil, fmt.Errorf("failed to close EML file: %w", err)
+	}
 	return pm, &buf, nil
 }
 
@@ -75,7 +79,7 @@ func parseEMLHeaders(mh *nm.Header, m *Msg) error {
 	// Extract address headers
 	if v := mh.Get(HeaderFrom.String()); v != "" {
 		if err := m.From(v); err != nil {
-			return fmt.Errorf(`failed to parse "From:" header: %w`, err)
+			return fmt.Errorf(`failed to parse %q header: %w`, HeaderFrom, err)
 		}
 	}
 	ahl := map[AddrHeader]func(...string) error{
@@ -94,7 +98,7 @@ func parseEMLHeaders(mh *nm.Header, m *Msg) error {
 				als = append(als, a.String())
 			}
 			if err := f(als...); err != nil {
-				return fmt.Errorf(`failed to parse "To:" header: %w`, err)
+				return fmt.Errorf(`failed to parse %q header: %w`, HeaderTo, err)
 			}
 		}
 	}
@@ -123,7 +127,7 @@ func parseEMLHeaders(mh *nm.Header, m *Msg) error {
 	return nil
 }
 
-// parseEMLBodyParts ...
+// parseEMLBodyParts parses the body of a EML based on the different content types and encodings
 func parseEMLBodyParts(pm *nm.Message, mbbuf *bytes.Buffer, m *Msg) error {
 	// Extract the transfer encoding of the body
 	mt, par, err := mime.ParseMediaType(pm.Header.Get(HeaderContentType.String()))
@@ -137,26 +141,26 @@ func parseEMLBodyParts(pm *nm.Message, mbbuf *bytes.Buffer, m *Msg) error {
 	cte := pm.Header.Get(HeaderContentTransferEnc.String())
 	switch strings.ToLower(mt) {
 	case TypeTextPlain.String():
-		if cte == NoEncoding.String() {
+		if strings.EqualFold(cte, NoEncoding.String()) {
 			m.SetEncoding(NoEncoding)
 			m.SetBodyString(TypeTextPlain, mbbuf.String())
 			break
 		}
-		if cte == EncodingQP.String() {
+		if strings.EqualFold(cte, EncodingQP.String()) {
 			m.SetEncoding(EncodingQP)
 			qpr := quotedprintable.NewReader(mbbuf)
 			qpbuf := bytes.Buffer{}
-			if _, err := qpbuf.ReadFrom(qpr); err != nil {
+			if _, err = qpbuf.ReadFrom(qpr); err != nil {
 				return fmt.Errorf("failed to read quoted-printable body: %w", err)
 			}
 			m.SetBodyString(TypeTextPlain, qpbuf.String())
 			break
 		}
-		if cte == EncodingB64.String() {
+		if strings.EqualFold(cte, EncodingB64.String()) {
 			m.SetEncoding(EncodingB64)
 			b64d := base64.NewDecoder(base64.StdEncoding, mbbuf)
 			b64buf := bytes.Buffer{}
-			if _, err := b64buf.ReadFrom(b64d); err != nil {
+			if _, err = b64buf.ReadFrom(b64d); err != nil {
 				return fmt.Errorf("failed to read base64 body: %w", err)
 			}
 			m.SetBodyString(TypeTextPlain, b64buf.String())