84 lines
1.9 KiB
Go
84 lines
1.9 KiB
Go
package common
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import (
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"errors"
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"net/smtp"
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"strings"
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ntlmssp "github.com/Azure/go-ntlmssp"
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)
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type smtpAutoAuth struct {
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username string
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password string
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mech string
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}
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func AutoSMTPAuth(username, password string) smtp.Auth {
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return &smtpAutoAuth{username: username, password: password}
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}
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func (a *smtpAutoAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
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useLoginAuth := SMTPForceAuthLogin
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if !useLoginAuth && shouldUseSMTPLoginAuth() {
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useLoginAuth = !(server != nil && len(server.Auth) == 1 && smtpServerSupportsAuth(server, "NTLM"))
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}
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if useLoginAuth {
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a.mech = "LOGIN"
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return "LOGIN", []byte{}, nil
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}
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switch {
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case smtpServerSupportsAuth(server, "PLAIN"):
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a.mech = "PLAIN"
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return smtp.PlainAuth("", a.username, a.password, SMTPServer).Start(server)
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case smtpServerSupportsAuth(server, "LOGIN"):
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a.mech = "LOGIN"
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return "LOGIN", []byte{}, nil
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case smtpServerSupportsAuth(server, "NTLM"):
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a.mech = "NTLM"
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negotiateMessage, err := ntlmssp.NewNegotiateMessage("", "")
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if err != nil {
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return "", nil, err
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}
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return "NTLM", negotiateMessage, nil
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default:
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a.mech = "PLAIN"
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return smtp.PlainAuth("", a.username, a.password, SMTPServer).Start(server)
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}
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}
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func (a *smtpAutoAuth) Next(fromServer []byte, more bool) ([]byte, error) {
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if !more {
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return nil, nil
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}
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switch a.mech {
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case "LOGIN":
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switch string(fromServer) {
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case "Username:":
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return []byte(a.username), nil
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case "Password:":
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return []byte(a.password), nil
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default:
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return nil, errors.New("unknown SMTP AUTH LOGIN challenge")
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}
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case "NTLM":
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return ntlmssp.NewAuthenticateMessage(fromServer, a.username, a.password, nil)
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default:
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return nil, errors.New("unexpected SMTP auth challenge")
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}
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}
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func smtpServerSupportsAuth(server *smtp.ServerInfo, mechanism string) bool {
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if server == nil {
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return false
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}
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for _, auth := range server.Auth {
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if strings.EqualFold(auth, mechanism) {
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return true
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}
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}
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return false
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}
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