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imap.go
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imap.go
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package certexpire
import (
"bytes"
"net"
"time"
)
func imapHasStartTLS(m []byte) bool {
match := []byte("STARTTLS")
s := bytes.IndexByte(m, '[')
if s < 0 {
return false
}
e := bytes.IndexByte(m[s:], ']')
if e < 0 {
return false
}
fs := bytes.Fields(m[s+1 : s+e])
for _, f := range fs {
if bytes.Equal(f, match) {
return true
}
}
return false
}
func imapprelude(conn net.Conn) error {
r := NewLineReader(conn)
l, err := r.Line()
if err != nil {
return err
}
if !bytes.Equal(l[0:4], []byte("* OK")) {
return ErrProtocol
}
if !imapHasStartTLS(l[4:]) {
return ErrProtocol
}
_, err = conn.Write([]byte("001 STARTTLS\r\n"))
if err != nil {
return err
}
l, err = r.Line()
if err != nil {
return err
}
if bytes.Index(l, []byte("001 OK")) < 0 {
return ErrProtocol
}
return nil
}
// GetCertIMAP returns the expiration date of an IMAP STARTTLS cert.
func GetCertIMAP(servername, port string, timeout time.Duration, proxy *Proxy) (*CertValues, error) {
conn, err := TCPDailer(servername+":"+port, proxy, timeout)
if err != nil {
return nil, err
}
conn.SetDeadline(deadline(timeout))
defer conn.Close()
if err := imapprelude(conn); err != nil {
return nil, err
}
return GetCertificate(conn, servername, timeout)
}