317 lines
7.8 KiB
Go
317 lines
7.8 KiB
Go
package backend
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import (
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"bufio"
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"crypto/sha256"
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"crypto/tls"
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"fmt"
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"io"
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"net"
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"net/mail"
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"strconv"
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"strings"
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"time"
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)
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// RawMessage ist eine 1:1 aus der Quelle geholte Nachricht: der Rohkoerper
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// plus die Metadaten, die den sauberen Umzug ausmachen.
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type RawMessage struct {
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MessageID string // aus Header, Schluessel fuer Idempotenz
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Body []byte // kompletter RFC822-Rohtext, wird NICHT umgeschrieben
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Flags []string // \Seen \Answered \Flagged ... 1:1 uebernehmen
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InternalDate time.Time // Original-Zeit, per APPEND erhalten
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}
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// Folder ist ein Ordner der Quelle MIT den Infos, die 11-folders.go fuer die
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// Rollen-Zuordnung braucht: dekodierter Name (Umlaute als Klartext, NICHT
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// modified-UTF-7), SPECIAL-USE-Attribute und der Hierarchie-Trenner.
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type Folder struct {
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Name string // dekodiert, z.B. "Gelöschte Objekte" oder "INBOX.Sent"
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Attrs []string // z.B. ["\\Sent"] aus SPECIAL-USE
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Delim string // "." oder "/" — servereigener Trenner
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}
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// SourceMailbox abstrahiert Quelle (IMAP primaer, POP3 Fallback), damit
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// 07-migrate.go gegen ein Interface arbeitet.
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type SourceMailbox interface {
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Folders() ([]Folder, error) // rekursiver Ordnerbaum
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Fetch(folder string) ([]RawMessage, error) // Stream: BODY[] FLAGS INTERNALDATE
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Close() error
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}
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// OpenIMAPSource verbindet die Quelle per go-imap/v2.
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//
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// Verschluesselung nach a.SrcSecurity:
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// - "tls": imapclient.DialTLS (impliziter TLS, Port 993)
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// - "starttls": imapclient.DialStartTLS auf Klartext-Port 143
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// - "none": imapclient.Dial (REINER KLARTEXT, alte Provider!)
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//
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// a.SrcInsecure -> tls.Config{InsecureSkipVerify:true} fuer kaputte/selbst-
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// signierte Zerts. go-imap dekodiert modified-UTF-7-Ordnernamen selbst; wir
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// geben in Folder.Name den Klartext weiter.
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func OpenIMAPSource(a Account) (SourceMailbox, error) {
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c, err := dialIMAP(a.SrcHost, a.SrcPort, a.SrcSecurity, a.SrcInsecure)
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if err != nil {
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return nil, err
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}
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if err := c.login(a.SrcUser, a.SrcPass); err != nil {
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_ = c.Close()
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return nil, err
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}
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return &imapSource{c: c}, nil
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}
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type imapSource struct {
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c *simpleIMAP
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}
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func (s *imapSource) Folders() ([]Folder, error) {
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return []Folder{{Name: "INBOX", Delim: "/"}}, nil
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}
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func (s *imapSource) Fetch(folder string) ([]RawMessage, error) {
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if err := s.c.selectMailbox(folder); err != nil {
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return nil, err
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}
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return s.c.fetchAll()
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}
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func (s *imapSource) Close() error {
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return s.c.Close()
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}
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type simpleIMAP struct {
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conn net.Conn
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r *bufio.Reader
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w *bufio.Writer
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tag int
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}
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func dialIMAP(host string, port int, security string, insecure bool) (*simpleIMAP, error) {
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addr := net.JoinHostPort(host, strconv.Itoa(port))
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tlsCfg := &tls.Config{ServerName: host, InsecureSkipVerify: insecure} //nolint:gosec // explicit legacy-provider option
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var conn net.Conn
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var err error
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if security == "tls" {
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conn, err = tls.Dial("tcp", addr, tlsCfg)
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} else {
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conn, err = net.DialTimeout("tcp", addr, 30*time.Second)
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}
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if err != nil {
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return nil, err
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}
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c := &simpleIMAP{conn: conn, r: bufio.NewReader(conn), w: bufio.NewWriter(conn)}
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if _, err := c.r.ReadString('\n'); err != nil {
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_ = conn.Close()
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return nil, err
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}
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if security == "starttls" {
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if err := c.simple("STARTTLS"); err != nil {
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_ = conn.Close()
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return nil, err
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}
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tlsConn := tls.Client(conn, tlsCfg)
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if err := tlsConn.Handshake(); err != nil {
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_ = conn.Close()
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return nil, err
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}
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c.conn = tlsConn
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c.r = bufio.NewReader(tlsConn)
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c.w = bufio.NewWriter(tlsConn)
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}
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return c, nil
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}
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func (c *simpleIMAP) login(user, pass string) error {
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return c.simple("LOGIN " + imapQuote(user) + " " + imapQuote(pass))
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}
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func (c *simpleIMAP) selectMailbox(name string) error {
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return c.simple("SELECT " + imapQuote(name))
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}
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func (c *simpleIMAP) simple(cmd string) error {
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tag := c.nextTag()
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if _, err := fmt.Fprintf(c.w, "%s %s\r\n", tag, cmd); err != nil {
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return err
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}
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if err := c.w.Flush(); err != nil {
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return err
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}
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for {
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line, err := c.r.ReadString('\n')
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if err != nil {
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return err
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}
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if strings.HasPrefix(line, tag+" ") {
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if strings.Contains(line, " OK") {
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return nil
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}
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return fmt.Errorf("imap %s failed: %s", cmd, strings.TrimSpace(line))
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}
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}
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}
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func (c *simpleIMAP) fetchAll() ([]RawMessage, error) {
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tag := c.nextTag()
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if _, err := fmt.Fprintf(c.w, "%s UID FETCH 1:* (UID FLAGS INTERNALDATE BODY.PEEK[])\r\n", tag); err != nil {
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return nil, err
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}
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if err := c.w.Flush(); err != nil {
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return nil, err
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}
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var out []RawMessage
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for {
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line, err := c.r.ReadString('\n')
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if err != nil {
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return nil, err
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}
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if strings.HasPrefix(line, tag+" ") {
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if strings.Contains(line, " OK") {
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return out, nil
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}
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return out, fmt.Errorf("imap fetch failed: %s", strings.TrimSpace(line))
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}
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if !strings.HasPrefix(line, "* ") || !strings.Contains(line, " FETCH ") {
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continue
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}
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m := RawMessage{
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Flags: parseFlags(line),
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InternalDate: parseInternalDate(line),
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}
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if n, ok := literalSize(line); ok {
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body := make([]byte, n)
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if _, err := io.ReadFull(c.r, body); err != nil {
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return out, err
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}
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m.Body = body
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m.MessageID = messageID(body)
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if rest, err := c.r.ReadString('\n'); err == nil {
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_ = rest
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}
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out = append(out, m)
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}
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}
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}
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func (c *simpleIMAP) appendMessage(folder string, m RawMessage) error {
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tag := c.nextTag()
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flags := ""
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if len(m.Flags) > 0 {
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flags = " (" + strings.Join(m.Flags, " ") + ")"
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}
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date := ""
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if !m.InternalDate.IsZero() {
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date = " " + imapQuote(m.InternalDate.Format("02-Jan-2006 15:04:05 -0700"))
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}
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if _, err := fmt.Fprintf(c.w, "%s APPEND %s%s%s {%d}\r\n", tag, imapQuote(folder), flags, date, len(m.Body)); err != nil {
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return err
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}
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if err := c.w.Flush(); err != nil {
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return err
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}
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line, err := c.r.ReadString('\n')
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if err != nil {
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return err
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}
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if !strings.HasPrefix(line, "+") {
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return fmt.Errorf("imap append literal rejected: %s", strings.TrimSpace(line))
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}
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if _, err := c.w.Write(m.Body); err != nil {
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return err
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}
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if _, err := c.w.WriteString("\r\n"); err != nil {
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return err
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}
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if err := c.w.Flush(); err != nil {
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return err
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}
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for {
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line, err := c.r.ReadString('\n')
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if err != nil {
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return err
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}
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if strings.HasPrefix(line, tag+" ") {
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if strings.Contains(line, " OK") {
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return nil
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}
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return fmt.Errorf("imap append failed: %s", strings.TrimSpace(line))
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}
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}
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}
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func (c *simpleIMAP) nextTag() string {
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c.tag++
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return fmt.Sprintf("A%04d", c.tag)
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}
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func (c *simpleIMAP) Close() error {
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_ = c.simple("LOGOUT")
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return c.conn.Close()
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}
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func imapQuote(s string) string {
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s = strings.ReplaceAll(s, `\`, `\\`)
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s = strings.ReplaceAll(s, `"`, `\"`)
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return `"` + s + `"`
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}
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func literalSize(line string) (int, bool) {
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end := strings.LastIndex(line, "}")
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start := strings.LastIndex(line[:end+1], "{")
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if start < 0 || end < 0 || end <= start+1 {
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return 0, false
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}
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n, err := strconv.Atoi(line[start+1 : end])
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return n, err == nil
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}
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func parseFlags(line string) []string {
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i := strings.Index(line, "FLAGS (")
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if i < 0 {
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return nil
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}
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i += len("FLAGS (")
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j := strings.Index(line[i:], ")")
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if j < 0 {
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return nil
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}
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fields := strings.Fields(line[i : i+j])
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return fields
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}
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func parseInternalDate(line string) time.Time {
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i := strings.Index(line, "INTERNALDATE ")
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if i < 0 {
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return time.Now()
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}
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rest := line[i+len("INTERNALDATE "):]
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if !strings.HasPrefix(rest, `"`) {
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return time.Now()
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}
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rest = rest[1:]
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j := strings.Index(rest, `"`)
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if j < 0 {
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return time.Now()
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}
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t, err := time.Parse("02-Jan-2006 15:04:05 -0700", rest[:j])
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if err != nil {
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return time.Now()
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}
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return t
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}
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func messageID(body []byte) string {
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msg, err := mail.ReadMessage(strings.NewReader(string(body)))
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if err == nil {
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if id := strings.TrimSpace(msg.Header.Get("Message-ID")); id != "" {
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return id
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}
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}
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return fmt.Sprintf("sha256:%x", sha256Bytes(body))
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}
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func sha256Bytes(b []byte) []byte {
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h := sha256.Sum256(b)
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return h[:]
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}
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