Sendmail RCPT TO Command Arbitrary File Overwrite

#
# (C) Tenable Network Security, Inc.
#

include( 'compat.inc' );

if(description)
{
  script_id(10259);
  script_version ("$Revision: 1.33 $");
  script_cvs_date("$Date: 2016/12/09 21:04:55 $");

  script_name(english:"Sendmail RCPT TO Command Arbitrary File Overwrite");
  script_summary(english:"Checks if the remote mail server can be used to gain a shell");

  script_set_attribute(
    attribute:'synopsis',
    value:'The remote SMTP server is vulnerable to authentication bypass.'
  );

  script_set_attribute(
    attribute:'description',
    value:'The remote SMTP server did not complain when issued the
command :
	MAIL FROM: root@this_host
	RCPT TO: /tmp/nessus_test

This probably means that it is possible to send mail directly
to files, which is a serious threat, since this allows
anyone to overwrite any file on the remote server.

*** This security hole might be a false positive, since
*** some MTAs will not complain to this test, but instead
*** just drop the message silently.
*** Check for the presence of file \'nessus_test\' in /tmp !'
  );

  script_set_attribute(
    attribute:'solution',
    value:'This plugin tests for a generic condition.
    It may be remedied by upgrading, reconfiguring, or changing your SMTP Server (MTA).'
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:C");


 script_set_attribute(attribute:"plugin_publication_date", value: "1999/08/30");
  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_end_attributes();

 script_category(ACT_GATHER_INFO);
 script_copyright(english:"This script is Copyright (C) 1999-2016 Tenable Network Security, Inc.");
 script_family(english:"SMTP problems");
 script_dependencie("find_service1.nasl", "sendmail_expn.nasl", "smtpserver_detect.nasl");
 script_exclude_keys("SMTP/wrapped", "SMTP/microsoft_esmtp_5", "SMTP/qmail", "SMTP/postfix");
 script_require_ports("Services/smtp", 25);
 exit(0);
}

#
# The script code starts here
#

include("smtp_func.inc");

port = get_kb_item("Services/smtp");
if(!port)port = 25;
if (get_kb_item('SMTP/'+port+'/broken')) exit(0);

if(get_port_state(port))
{
 soc = open_sock_tcp(port);
 if(soc)
 {
 data = smtp_recv_banner(socket:soc);
 if(!data || "Sendmail" >!< data)exit(0); # Only Sendmail vulnerable
 crp = string("HELO example.com\r\n");
 send(socket:soc, data:crp);
 data = recv_line(socket:soc, length:1024);
 crp = string("MAIL FROM: root@",get_host_name(),"\r\n");
 send(socket:soc, data:crp);
 data = recv_line(socket:soc, length:1024);
 crp = string("RCPT TO: /tmp/nessus_test\r\n");
 send(socket:soc, data:crp);

 data = recv_line(socket:soc, length:4);
 if(data == "250 "){
 	security_hole(port);
 	data = recv_line(socket:soc, length:1024);

	crp = string("DATA\r\nYour MTA is vulnerable to the 'mailto files' attack\r\n.\r\nQUIT\r\n");
 	send(socket:soc, data:crp);
	}
 close(soc);
 }
}