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smtp: add --ehlo-domain/--helo-domain to set the client greeting name #753

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smtp: add --ehlo-domain/--helo-domain to set the client greeting name #753

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18 changes: 16 additions & 2 deletions modules/smtp/scanner.go
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Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,12 @@ type Flags struct {

// SMTPSecure indicates that the entire transaction should be wrapped in a TLS session.
SMTPSecure bool `long:"smtps" description:"Perform a TLS handshake immediately upon connecting."`

// EHLODomain is the client domain sent with EHLO; empty falls back to the target domain.
EHLODomain string `long:"ehlo-domain" description:"Client domain to send with the EHLO command (default: target domain)"`

// HELODomain is the client domain sent with HELO; empty falls back to the target domain.
HELODomain string `long:"helo-domain" description:"Client domain to send with the HELO command (default: target domain)"`
}

func NewModule() *zgrab2.TypedModule[Flags, Scanner, *Scanner] {
Expand Down Expand Up @@ -254,15 +260,23 @@ func (scanner *Scanner) Scan(ctx context.Context, dialGroup *zgrab2.DialerGroup,
shouldSendEHLO := !scanner.config.SendHELOOverride && (serverSupportsEHLO || scanner.config.SendEHLOOverride)
if shouldSendEHLO {
// server supports EHLO, use Extended Hello
ret, err := smtpConn.SendCommand(getCommand("EHLO", target.Domain))
domain := scanner.config.EHLODomain
if domain == "" {
domain = target.Domain
}
ret, err := smtpConn.SendCommand(getCommand("EHLO", domain))
if err != nil {
return appErrStatus(), result, fmt.Errorf("could not send EHLO command: %w", err)
}
result.EHLO = ret
moduleMetadata.incrementHostsSupportingEHLO() // mark that we found a host that supports EHLO
} else {
// send a HELO msg since server doesn't support EHLO
ret, err := smtpConn.SendCommand(getCommand("HELO", target.Domain))
domain := scanner.config.HELODomain
if domain == "" {
domain = target.Domain
}
ret, err := smtpConn.SendCommand(getCommand("HELO", domain))
if err != nil {
return appErrStatus(), result, fmt.Errorf("could not send HELO command: %w", err)
}
Expand Down