2018-03-15 17:10:10 +00:00
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// Package pop3 provides a zgrab2 module that scans for POP3 mail
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// servers.
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// Default Port: 110 (TCP)
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//
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// The --send-help and --send-noop flags tell the scanner to send a
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// HELP or NOOP command and read the response.
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//
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// The --pop3s flag tells the scanner to perform a TLS handshake
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// immediately after connecting, before even attempting to read
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// the banner.
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// The --starttls flag tells the scanner to send the STLS command,
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// and then negotiate a TLS connection.
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// The scanner uses the standard TLS flags for the handshake.
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// --pop3s and --starttls are mutually exclusive.
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// --pop3s does not change the default port number from 110, so
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// it should usually be coupled with e.g. --port 995.
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//
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// The --send-quit flag tells the scanner to send a QUIT command
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// before disconnecting.
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//
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// So, if no flags are specified, the scanner simply reads the banner
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// returned by the server and disconnects.
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//
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// The output contains the banner and the responses to any commands that
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// were sent, and if or --pop3s --starttls were set, the standard TLS logs.
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package pop3
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import (
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"fmt"
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log "github.com/sirupsen/logrus"
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"github.com/zmap/zgrab2"
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"strings"
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)
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// ScanResults instances are returned by the module's Scan function.
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type ScanResults struct {
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// Banner is the string sent by the server immediately after connecting.
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Banner string `json:"banner,omitempty"`
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// NOOP is the server's response to the NOOP command, if one is sent.
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NOOP string `json:"noop,omitempty"`
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// HELP is the server's response to the HELP command, if it is sent.
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HELP string `json:"help,omitempty"`
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// StartTLS is the server's response to the STARTTLS command, if it is sent.
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StartTLS string `json:"starttls,omitempty"`
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// QUIT is the server's response to the QUIT command, if it is sent.
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QUIT string `json:"quit,omitempty"`
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// TLSLog is the standard TLS log, if --starttls or --pop3s is enabled.
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TLSLog *zgrab2.TLSLog `json:"tls,omitempty"`
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}
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// Flags holds the command-line configuration for the POP3 scan module.
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// Populated by the framework.
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type Flags struct {
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zgrab2.BaseFlags
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zgrab2.TLSFlags
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// SendHELP indicates that the client should send the HELP command.
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SendHELP bool `long:"send-help" description:"Send the HELP command"`
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// SendNOOP indicates that the NOOP command should be sent.
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SendNOOP bool `long:"send-noop" description:"Send the NOOP command before closing."`
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// SendQUIT indicates that the QUIT command should be sent.
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SendQUIT bool `long:"send-quit" description:"Send the QUIT command before closing."`
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// POP3Secure indicates that the client should do a TLS handshake immediately after connecting.
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POP3Secure bool `long:"pop3s" description:"Immediately negotiate a TLS connection"`
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// StartTLS indicates that the client should attempt to update the connection to TLS.
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StartTLS bool `long:"starttls" description:"Send STLS before negotiating"`
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// Verbose indicates that there should be more verbose logging.
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Verbose bool `long:"verbose" description:"More verbose logging, include debug fields in the scan results"`
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}
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// Module implements the zgrab2.Module interface.
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type Module struct {
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}
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// Scanner implements the zgrab2.Scanner interface.
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type Scanner struct {
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config *Flags
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}
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// RegisterModule registers the zgrab2 module.
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func RegisterModule() {
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var module Module
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_, err := zgrab2.AddCommand("pop3", "pop3", "Probe for pop3", 110, &module)
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if err != nil {
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log.Fatal(err)
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}
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}
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// NewFlags returns a default Flags object.
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func (module *Module) NewFlags() interface{} {
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return new(Flags)
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}
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// NewScanner returns a new Scanner instance.
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func (module *Module) NewScanner() zgrab2.Scanner {
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return new(Scanner)
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}
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// Validate checks that the flags are valid.
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// On success, returns nil.
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// On failure, returns an error instance describing the error.
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func (flags *Flags) Validate(args []string) error {
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if flags.StartTLS && flags.POP3Secure {
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log.Error("Cannot send both --starttls and --pop3s")
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return zgrab2.ErrInvalidArguments
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}
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return nil
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}
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// Help returns the module's help string.
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func (flags *Flags) Help() string {
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return ""
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}
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// Init initializes the Scanner.
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func (scanner *Scanner) Init(flags zgrab2.ScanFlags) error {
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f, _ := flags.(*Flags)
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scanner.config = f
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return nil
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}
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// InitPerSender initializes the scanner for a given sender.
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func (scanner *Scanner) InitPerSender(senderID int) error {
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return nil
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}
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// GetName returns the Scanner name defined in the Flags.
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func (scanner *Scanner) GetName() string {
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return scanner.config.Name
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}
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2018-06-26 17:51:10 +00:00
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// GetTrigger returns the Trigger defined in the Flags.
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func (scanner *Scanner) GetTrigger() string {
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return scanner.config.Trigger
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}
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2018-03-15 17:10:10 +00:00
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// Protocol returns the protocol identifier of the scan.
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func (scanner *Scanner) Protocol() string {
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return "pop3"
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}
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// GetPort returns the port being scanned.
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func (scanner *Scanner) GetPort() uint {
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return scanner.config.Port
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}
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func getPOP3Error(response string) error {
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if !strings.HasPrefix(response, "-") {
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return nil
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}
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return fmt.Errorf("POP3 error: %s", response[1:])
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}
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// Scan performs the POP3 scan.
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// 1. Open a TCP connection to the target port (default 110).
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// 2. If --pop3s is set, perform a TLS handshake using the command-line
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// flags.
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// 3. Read the banner.
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// 4. If --send-help is sent, send HELP, read the result.
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// 5. If --send-noop is sent, send NOOP, read the result.
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// 6. If --starttls is sent, send STLS, read the result, negotiate a
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// TLS connection using the command-line flags.
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// 7. If --send-quit is sent, send QUIT and read the result.
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// 8. Close the connection.
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func (scanner *Scanner) Scan(target zgrab2.ScanTarget) (zgrab2.ScanStatus, interface{}, error) {
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c, err := target.Open(&scanner.config.BaseFlags)
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if err != nil {
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return zgrab2.TryGetScanStatus(err), nil, err
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}
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defer c.Close()
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result := &ScanResults{}
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if scanner.config.POP3Secure {
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tlsConn, err := scanner.config.TLSFlags.GetTLSConnection(c)
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if err != nil {
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return zgrab2.TryGetScanStatus(err), nil, err
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}
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result.TLSLog = tlsConn.GetLog()
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if err := tlsConn.Handshake(); err != nil {
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return zgrab2.TryGetScanStatus(err), result, err
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}
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c = tlsConn
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}
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conn := Connection{Conn: c}
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banner, err := conn.ReadResponse()
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if err != nil {
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return zgrab2.TryGetScanStatus(err), nil, err
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}
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result.Banner = banner
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if scanner.config.SendHELP {
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ret, err := conn.SendCommand("HELP")
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if err != nil {
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return zgrab2.TryGetScanStatus(err), result, err
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}
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result.HELP = ret
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}
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if scanner.config.SendNOOP {
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ret, err := conn.SendCommand("NOOP")
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if err != nil {
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return zgrab2.TryGetScanStatus(err), result, err
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}
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result.NOOP = ret
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}
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if scanner.config.StartTLS {
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ret, err := conn.SendCommand("STLS")
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if err != nil {
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return zgrab2.TryGetScanStatus(err), result, err
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}
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result.StartTLS = ret
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if err := getPOP3Error(ret); err != nil {
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return zgrab2.TryGetScanStatus(err), result, err
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}
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tlsConn, err := scanner.config.TLSFlags.GetTLSConnection(conn.Conn)
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if err != nil {
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return zgrab2.TryGetScanStatus(err), result, err
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}
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result.TLSLog = tlsConn.GetLog()
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if err := tlsConn.Handshake(); err != nil {
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return zgrab2.TryGetScanStatus(err), result, err
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}
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conn.Conn = tlsConn
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}
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if scanner.config.SendQUIT {
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ret, err := conn.SendCommand("QUIT")
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if err != nil {
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if err != nil {
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return zgrab2.TryGetScanStatus(err), nil, err
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}
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}
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result.QUIT = ret
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}
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return zgrab2.SCAN_SUCCESS, result, nil
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2018-06-26 17:51:10 +00:00
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}
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