package gomime import ( "fmt" "io" "mime" "mime/quotedprintable" "regexp" "strings" "unicode/utf8" "encoding/base64" "golang.org/x/text/encoding" "golang.org/x/text/encoding/htmlindex" ) var wordDec = &mime.WordDecoder{ CharsetReader: func(charset string, input io.Reader) (io.Reader, error) { dec, err := selectDecoder(charset) if err != nil { return nil, err } if dec == nil { // utf-8 return input, nil } return dec.Reader(input), nil }, } // expected trimmed low case func getEncoding(charset string) (enc encoding.Encoding, err error) { preparsed := strings.Trim(strings.ToLower(charset), " \t\r\n") // koi re := regexp.MustCompile("(cs)?koi[-_ ]?8?[-_ ]?(r|ru|u|uk)?$") matches := re.FindAllStringSubmatch(preparsed, -1) if len(matches) == 1 && len(matches[0]) == 3 { preparsed = "koi8-" switch matches[0][2] { case "u", "uk": preparsed += "u" default: preparsed += "r" } } // windows-XXXX re = regexp.MustCompile("(cp|(cs)?win(dows)?)[-_ ]?([0-9]{3,4})$") matches = re.FindAllStringSubmatch(preparsed, -1) if len(matches) == 1 && len(matches[0]) == 5 { switch matches[0][4] { case "874", "1250", "1251", "1252", "1253", "1254", "1255", "1256", "1257", "1258": preparsed = "windows-" + matches[0][4] } } // iso re = regexp.MustCompile("iso[-_ ]?([0-9]{4})[-_ ]?([0-9]+|jp)?[-_ ]?(i|e)?") matches = re.FindAllStringSubmatch(preparsed, -1) if len(matches) == 1 && len(matches[0]) == 4 { if matches[0][1] == "2022" && matches[0][2] == "jp" { preparsed = "iso-2022-jp" } if matches[0][1] == "8859" { switch matches[0][2] { case "1", "2", "3", "4", "5", "7", "8", "9", "10", "11", "13", "14", "15", "16": preparsed = "iso-8859-" + matches[0][2] if matches[0][3] == "i" { preparsed += "-" + matches[0][3] } case "": preparsed = "iso-8859-1" } } } // latin is tricky re = regexp.MustCompile("^(cs|csiso)?l(atin)?[-_ ]?([0-9]{1,2})$") matches = re.FindAllStringSubmatch(preparsed, -1) if len(matches) == 1 && len(matches[0]) == 4 { switch matches[0][3] { case "1": preparsed = "windows-1252" case "2", "3", "4", "5": preparsed = "iso-8859-" + matches[0][3] case "6": preparsed = "iso-8859-10" case "8": preparsed = "iso-8859-14" case "9": preparsed = "iso-8859-15" case "10": preparsed = "iso-8859-16" } } // missing substitutions switch preparsed { case "csutf8", "iso-utf-8", "utf8mb4": preparsed = "utf-8" case "eucjp", "ibm-eucjp": preparsed = "euc-jp" case "euckr", "ibm-euckr", "cp949": preparsed = "euc-kr" case "euccn", "ibm-euccn": preparsed = "gbk" case "zht16mswin950", "cp950": preparsed = "big5" case "csascii", "ansi_x3.4-1968", "ansi_x3.4-1986", "ansi_x3.110-1983", "cp850", "cp858", "us", "iso646", "iso-646", "iso646-us", "iso_646.irv:1991", "cp367", "ibm367", "ibm-367", "iso-ir-6": preparsed = "ascii" case "ibm852": preparsed = "iso-8859-2" case "iso-ir-199", "iso-celtic": preparsed = "iso-8859-14" case "iso-ir-226": preparsed = "iso-8859-16" case "macroman": preparsed = "macintosh" } enc, _ = htmlindex.Get(preparsed) if enc == nil { err = fmt.Errorf("can not get encodig for '%s' (or '%s')", charset, preparsed) } return } func selectDecoder(charset string) (decoder *encoding.Decoder, err error) { var enc encoding.Encoding lcharset := strings.Trim(strings.ToLower(charset), " \t\r\n") switch lcharset { case "utf7", "utf-7", "unicode-1-1-utf-7": return NewUtf7Decoder(), nil default: enc, err = getEncoding(lcharset) } if err == nil { decoder = enc.NewDecoder() } return } // DecodeHeader if needed. Returns error if raw contains non-utf8 characters func DecodeHeader(raw string) (decoded string, err error) { if decoded, err = wordDec.DecodeHeader(raw); err != nil { decoded = raw } if !utf8.ValidString(decoded) { err = fmt.Errorf("header contains non utf8 chars: %v", err) } return } // EncodeHeader using quoted printable and utf8 func EncodeHeader(s string) string { return mime.QEncoding.Encode("utf-8", s) } // DecodeCharset decodes the orginal using content type parameters. When // charset missing it checks the content is utf8-valid. func DecodeCharset(original []byte, mediaType string, contentTypeParams map[string]string) ([]byte, error) { var decoder *encoding.Decoder var err error if charset, ok := contentTypeParams["charset"]; ok { decoder, err = selectDecoder(charset) } else { if !strings.HasPrefix(mediaType, "text/") || utf8.Valid(original) { return original, nil } err = fmt.Errorf("non-utf8 content without charset specification") } if err != nil { return original, err } utf8, err := decoder.Bytes(original) if err != nil { return original, err } return utf8, nil } // DecodeContentEncoding wraps the reader with decoder based on content encoding func DecodeContentEncoding(r io.Reader, contentEncoding string) (d io.Reader) { switch strings.ToLower(contentEncoding) { case "quoted-printable": d = quotedprintable.NewReader(r) case "base64": d = base64.NewDecoder(base64.StdEncoding, r) case "7bit", "8bit", "binary", "": // Nothing to do d = r } return }