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Add content type, charset processing and refactor encoding process

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Extended the settings for content type and charset from headers. Also, refactored the handling of encoding types - 'QP' and 'B64' - within the mail header and body parsing sections. The process of handling encoding for plain type mail specifically is now encapsulated in a new function, parseEMLBodyPlain. These changes enhance code readability, maintainability, and error handling efficiency.
This commit is contained in:
Winni Neessen 2024-02-09 15:56:39 +01:00
parent 4202f705a0
commit 53566a93cd
Signed by: wneessen
GPG key ID: 385AC9889632126E
1 changed files with 85 additions and 31 deletions
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116
eml.go
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@ -111,6 +111,28 @@ func parseEMLHeaders(mh *nm.Header, m *Msg) error {
HeaderXMailer, HeaderXMSMailPriority, HeaderXPriority,
}
// Extract content type, charset and encoding first
if v := mh.Get(HeaderContentTransferEnc.String()); v != "" {
switch {
case strings.EqualFold(v, EncodingQP.String()):
m.SetEncoding(EncodingQP)
case strings.EqualFold(v, EncodingB64.String()):
m.SetEncoding(EncodingB64)
default:
m.SetEncoding(NoEncoding)
}
}
if v := mh.Get(HeaderContentType.String()); v != "" {
ct, cs := parseContentType(v)
if cs != "" {
m.SetCharset(Charset(cs))
}
m.setEncoder()
if ct != "" {
m.SetGenHeader(HeaderContentType, ct)
}
}
// Extract address headers
if v := mh.Get(HeaderFrom.String()); v != "" {
if err := m.From(v); err != nil {
@ -156,6 +178,9 @@ func parseEMLHeaders(mh *nm.Header, m *Msg) error {
for _, h := range commonHeaders {
if v := mh.Get(h.String()); v != "" {
m.SetGenHeader(h, v)
if strings.EqualFold(h.String(), "subject") {
fmt.Printf("SUBJECT: %s\n", m.GetGenHeader(HeaderSubject)[0])
}
}
}
@ -173,43 +198,52 @@ func parseEMLBodyParts(pm *nm.Message, bodybuf *bytes.Buffer, m *Msg) error {
m.SetCharset(Charset(v))
}
cte := pm.Header.Get(HeaderContentTransferEnc.String())
switch strings.ToLower(mediatype) {
case TypeTextPlain.String():
if strings.EqualFold(cte, NoEncoding.String()) {
m.SetEncoding(NoEncoding)
m.SetBodyString(TypeTextPlain, bodybuf.String())
break
switch {
case strings.EqualFold(mediatype, TypeTextPlain.String()),
strings.EqualFold(mediatype, TypeTextHTML.String()):
if err := parseEMLBodyPlain(mediatype, pm, bodybuf, m); err != nil {
return fmt.Errorf("failed to parse plain body: %w", err)
}
if strings.EqualFold(cte, EncodingQP.String()) {
m.SetEncoding(EncodingQP)
qpr := quotedprintable.NewReader(bodybuf)
qpbuf := bytes.Buffer{}
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 strings.EqualFold(cte, EncodingB64.String()) {
m.SetEncoding(EncodingB64)
b64d := base64.NewDecoder(base64.StdEncoding, bodybuf)
b64buf := bytes.Buffer{}
if _, err = b64buf.ReadFrom(b64d); err != nil {
return fmt.Errorf("failed to read base64 body: %w", err)
}
m.SetBodyString(TypeTextPlain, b64buf.String())
break
}
case TypeMultipartAlternative.String():
case strings.EqualFold(mediatype, TypeMultipartAlternative.String()):
if err := parseEMLMultipartAlternative(params, bodybuf, m); err != nil {
return fmt.Errorf("failed to parse multipart/alternative: %w", err)
return fmt.Errorf("failed to parse multipart/alternative body: %w", err)
}
default:
}
return nil
}
// parseEMLBodyPlain parses the mail body of plain type mails
func parseEMLBodyPlain(mediatype string, pm *nm.Message, bodybuf *bytes.Buffer, m *Msg) error {
cte := pm.Header.Get(HeaderContentTransferEnc.String())
if strings.EqualFold(cte, NoEncoding.String()) {
m.SetEncoding(NoEncoding)
m.SetBodyString(ContentType(mediatype), bodybuf.String())
return nil
}
if strings.EqualFold(cte, EncodingQP.String()) {
m.SetEncoding(EncodingQP)
qpr := quotedprintable.NewReader(bodybuf)
qpbuf := bytes.Buffer{}
if _, err := qpbuf.ReadFrom(qpr); err != nil {
return fmt.Errorf("failed to read quoted-printable body: %w", err)
}
m.SetBodyString(ContentType(mediatype), qpbuf.String())
return nil
}
if strings.EqualFold(cte, EncodingB64.String()) {
m.SetEncoding(EncodingB64)
b64d := base64.NewDecoder(base64.StdEncoding, bodybuf)
b64buf := bytes.Buffer{}
if _, err := b64buf.ReadFrom(b64d); err != nil {
return fmt.Errorf("failed to read base64 body: %w", err)
}
m.SetBodyString(ContentType(mediatype), b64buf.String())
return nil
}
return fmt.Errorf("unsupported Content-Transfer-Encoding")
}
// parseEMLMultipartAlternative parses a multipart/alternative body part of a EML
func parseEMLMultipartAlternative(params map[string]string, bodybuf *bytes.Buffer, m *Msg) error {
boundary, ok := params["boundary"]
@ -242,7 +276,7 @@ func parseEMLMultipartAlternative(params map[string]string, bodybuf *bytes.Buffe
}
switch {
case strings.EqualFold(mpTransferEnc[0], EncodingB64.String()):
if err := handleEMLMultiPartBase64Encoding(mpTransferEnc, mpdata, p); err != nil {
if err := handleEMLMultiPartBase64Encoding(mpdata, p); err != nil {
return fmt.Errorf("failed to handle multipart base64 transfer-encoding: %w", err)
}
}
@ -257,6 +291,8 @@ func parseEMLMultipartAlternative(params map[string]string, bodybuf *bytes.Buffe
return nil
}
// parseEMLMultiPartCharset parses the Charset from a ContentType header and assigns it to a Part
// TODO: This might be redundant to parseContentType
func parseEMLMultiPartCharset(mpContentTypeSplit []string, p *Part) {
if len(mpContentTypeSplit) > 1 && strings.HasPrefix(strings.ToLower(mpContentTypeSplit[1]), "charset=") {
valSplit := strings.Split(mpContentTypeSplit[1], "=")
@ -266,7 +302,8 @@ func parseEMLMultiPartCharset(mpContentTypeSplit []string, p *Part) {
}
}
func handleEMLMultiPartBase64Encoding(mpTransferEnc []string, mpdata []byte, p *Part) error {
// handleEMLMultiPartBase64Encoding sets the content body of a base64 encoded Part
func handleEMLMultiPartBase64Encoding(mpdata []byte, p *Part) error {
p.SetEncoding(EncodingB64)
cont, err := base64.StdEncoding.DecodeString(string(mpdata))
if err != nil {
@ -275,3 +312,20 @@ func handleEMLMultiPartBase64Encoding(mpTransferEnc []string, mpdata []byte, p *
p.SetContent(string(cont))
return nil
}
// parseContentType parses the Content-Type header and returns the type and charse as
// separate string values
func parseContentType(cth string) (ct string, cs string) {
cts := strings.SplitN(cth, "; ", 2)
if len(cts) != 2 {
return
}
ct = cts[0]
if strings.HasPrefix(strings.ToLower(cts[1]), "charset=") {
css := strings.SplitN(cts[1], "=", 2)
if len(css) == 2 {
cs = css[1]
}
}
return
}