forked from veqryn/go-email
/
parser.go
201 lines (176 loc) · 5.53 KB
/
parser.go
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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
package email
import (
"bufio"
"bytes"
"encoding/base64"
"fmt"
"io"
"io/ioutil"
"mime"
"mime/multipart"
"mime/quotedprintable"
"net/mail"
"strings"
)
// ParseMessage parses and returns a Message from an io.Reader
// containing the raw text of an email message.
// (If the raw email is a string or []byte, use strings.NewReader()
// or bytes.NewReader() to create a reader.)
// Any "quoted-printable" or "base64" encoded bodies will be decoded.
func ParseMessage(r io.Reader) (*Message, error) {
msg, err := mail.ReadMessage(&leftTrimReader{r: bufioReader(r)})
if err != nil {
return nil, err
}
// decode any Q-encoded values
for _, values := range msg.Header {
for idx, val := range values {
values[idx] = decodeRFC2047(val)
}
}
return parseMessageWithHeader(Header(msg.Header), msg.Body)
}
// parseMessageWithHeader parses and returns a Message from an already filled
// Header, and an io.Reader containing the raw text of the body/payload.
// (If the raw body is a string or []byte, use strings.NewReader()
// or bytes.NewReader() to create a reader.)
// Any "quoted-printable" or "base64" encoded bodies will be decoded.
func parseMessageWithHeader(headers Header, bodyReader io.Reader) (*Message, error) {
bufferedReader := contentReader(headers, bodyReader)
var err error
var mediaType string
var mediaTypeParams map[string]string
var preamble []byte
var epilogue []byte
var body []byte
var parts []*Message
var subMessage *Message
if contentType := headers.Get("Content-Type"); len(contentType) > 0 {
mediaType, mediaTypeParams, err = mime.ParseMediaType(contentType)
if err != nil {
return nil, err
}
} // Lack of contentType is not a problem
// Can only have one of the following: Parts, SubMessage, or Body
if strings.HasPrefix(mediaType, "multipart") {
boundary := mediaTypeParams["boundary"]
preamble, err = readPreamble(bufferedReader, boundary)
if err == nil {
parts, err = readParts(bufferedReader, boundary)
if err == nil {
epilogue, err = readEpilogue(bufferedReader)
}
}
} else if strings.HasPrefix(mediaType, "message") {
subMessage, err = ParseMessage(bufferedReader)
} else {
body, err = ioutil.ReadAll(bufferedReader)
}
if err != nil {
return nil, err
}
return &Message{
Header: headers,
Preamble: preamble,
Epilogue: epilogue,
Body: body,
SubMessage: subMessage,
Parts: parts,
}, nil
}
// readParts parses out the parts of a multipart body, including the preamble and epilogue.
func readParts(bodyReader io.Reader, boundary string) ([]*Message, error) {
parts := make([]*Message, 0, 1)
multipartReader := multipart.NewReader(bodyReader, boundary)
for part, partErr := multipartReader.NextPart(); partErr != io.EOF; part, partErr = multipartReader.NextPart() {
if partErr != nil && partErr != io.EOF {
return []*Message{}, partErr
}
newEmailPart, msgErr := parseMessageWithHeader(Header(part.Header), part)
part.Close()
if msgErr != nil {
return []*Message{}, msgErr
}
parts = append(parts, newEmailPart)
}
return parts, nil
}
// readEpilogue ...
func readEpilogue(r io.Reader) ([]byte, error) {
epilogue, err := ioutil.ReadAll(r)
for len(epilogue) > 0 && isASCIISpace(epilogue[len(epilogue)-1]) {
epilogue = epilogue[:len(epilogue)-1]
}
if len(epilogue) > 0 {
return epilogue, err
}
return nil, err
}
// readPreamble ...
func readPreamble(r *bufio.Reader, boundary string) ([]byte, error) {
preamble, err := ioutil.ReadAll(&preambleReader{r: r, boundary: []byte("--" + boundary)})
if len(preamble) > 0 {
return preamble, err
}
return nil, err
}
// preambleReader ...
type preambleReader struct {
r *bufio.Reader
boundary []byte
}
// Read ...
func (r *preambleReader) Read(p []byte) (int, error) {
if len(p) == 0 {
return 0, nil
}
// Peek and read up to the --boundary, then EOF
peek, err := r.r.Peek(len(p))
if err != nil && err != io.EOF {
return 0, fmt.Errorf("Preamble Read: %v", err)
}
idx := bytes.Index(peek, r.boundary)
if idx < 0 {
// Couldn't find the boundary, so read all the bytes we can,
// but leave room for a new-line + boundary that got cut in half by the buffer,
// that way it can be matched against on the next read
return r.r.Read(p[:max(1, len(peek)-(len(r.boundary)+2))])
}
// Account for possible new-line / whitespace at start of the boundary, which shouldn't be removed
for idx > 0 && isASCIISpace(peek[idx-1]) {
idx--
}
if idx == 0 {
// The boundary (or new-line + boundary) is at the start of the reader, so there is no preamble
return 0, io.EOF
}
n, err := r.r.Read(p[:idx])
if err != nil && err != io.EOF {
return n, err
}
return n, io.EOF
}
// contentReader ...
func contentReader(headers Header, bodyReader io.Reader) *bufio.Reader {
if headers.Get("Content-Transfer-Encoding") == "quoted-printable" {
headers.Del("Content-Transfer-Encoding")
return bufioReader(quotedprintable.NewReader(bodyReader))
}
if headers.Get("Content-Transfer-Encoding") == "base64" {
headers.Del("Content-Transfer-Encoding")
return bufioReader(base64.NewDecoder(base64.StdEncoding, bodyReader))
}
return bufioReader(bodyReader)
}
// decodeRFC2047 ...
func decodeRFC2047(s string) string {
// GO 1.5 does not decode headers, but this may change in future releases...
decoded, err := (&mime.WordDecoder{}).DecodeHeader(s)
if err != nil || len(decoded) == 0 {
return s
}
return decoded
}