Development changes since 0.7.2

Milter/dsn.py

@@ -0,0 +1,168 @@
+import smtplib
+import spf
+import socket
+from email.Message import Message
+
+nospf_msg = """This is an automatically generated Delivery Status Notification.
+
+THIS IS A WARNING MESSAGE ONLY.
+
+YOU DO *NOT* NEED TO RESEND YOUR MESSAGE.
+
+Delivery to the following recipients has been delayed.
+
+	%(rcpt)s
+
+Subject: %(subject)s 
+
+Someone at IP address %(connectip)s sent an email claiming
+to be from %(sender)s.  
+
+If that wasn't you, then your domain, %(sender_domain)s,
+was forged - i.e. used without your knowlege or authorization by
+someone attempting to steal your mail identity.  This is a very
+serious problem, and you need to provide authentication for your
+SMTP (email) servers to prevent criminals from forging your
+domain.  The simplest step is usually to publish an SPF record
+with your Sender Policy.  
+
+For more information, see: http://spfhelp.net
+
+I hate to annoy you with a DSN (Delivery Status
+Notification) from a possibly forged email, but since you
+have not published a sender policy, there is no other way
+of bringing this to your attention.
+
+If it *was* you that sent the email, then your email domain
+or configuration is in error.  If you don't know anything
+about mail servers, then pass this on to your SMTP (mail)
+server administrator.  We have accepted the email anyway, in
+case it is important, but we couldn't find anything about
+the mail submitter at %(connectip)s to distinguish it from a
+zombie (compromised/infected computer - usually a Windows
+PC).  There was no PTR record for its IP address (PTR names
+that contain the IP address don't count).  RFC2821 requires
+that your hello name be a FQN (Fully Qualified domain Name,
+i.e. at least one dot) that resolves to the IP address of
+the mail sender.  In addition, just like for PTR, we don't
+accept a helo name that contains the IP, since this doesn't
+help to identify you.  The hello name you used,
+%(heloname)s, was invalid.
+
+Furthermore, there was no SPF record for the sending domain
+%(sender_domain)s.  We even tried to find its IP in any A or
+MX records for your domain, but that failed also.  We really
+should reject mail from anonymous mail clients, but in case
+it is important, we are accepting it anyway.
+
+We are sending you this message to alert you to the fact that
+
+Either - Someone is forging your domain.
+Or - You have problems with your email configuration.
+Or - Possibly both.
+
+If you need further assistance, please do not hesitate to
+contact me again.
+
+Kind regards,
+Stuart D. Gathman
+postmaster@%(receiver)s
+"""
+
+softfail_msg = """
+This is an automatically generated Delivery Status Notification.
+
+THIS IS A WARNING MESSAGE ONLY.
+
+YOU DO *NOT* NEED TO RESEND YOUR MESSAGE.
+
+Delivery to the following recipients has been delayed.
+
+       %(rcpt)s
+
+Subject: %(subject)s
+Received-SPF: %(spf_result)s
+"""
+
+def send_dsn(mailfrom,receiver,msg=None):
+  "Send DSN.  If msg is None, do callback verification."
+  user,domain = mailfrom.split('@')
+  q = spf.query(None,None,None)
+  mxlist = q.dns(domain,'MX')
+  if not mxlist:
+    mxlist = (0,domain),
+  else:
+    mxlist.sort()
+  smtp = smtplib.SMTP()
+  for prior,host in mxlist:
+    try:
+      smtp.connect(host)
+      code,resp = smtp.helo(receiver)
+      # some wiley spammers have MX records that resolve to 127.0.0.1
+      if resp.split()[0] == receiver:
+        return (553,'Fraudulent MX for %s' % domain)
+      if not (200 <= code <= 299):
+	raise SMTPHeloError(code, resp)
+      if msg:
+        try:
+	  smtp.sendmail('<>',mailfrom,msg)
+	except smtplib.SMTPSenderRefused:
+	  # does not accept DSN, try postmaster (at the risk of mail loops)
+	  smtp.sendmail('<postmaster@%s>'%receiver,mailfrom,msg)
+      else:	# CBV
+	code,resp = smtp.docmd('MAIL FROM: <>')
+	if code != 250:
+	  raise SMTPSenderRefused(code, resp, '<>')
+	code,resp = smtp.rcpt(mailfrom)
+	if code not in (250,251):
+	  return (code,resp)		# permanent error
+	smtp.quit()
+      return None			# success
+    except smtplib.SMTPRecipientsRefused,x:
+      return x.recipients[mailfrom]	# permanent error
+    except smtplib.SMTPSenderRefused,x:
+      return x		# does not accept DSN
+    except smtplib.SMTPDataError,x:
+      return x				# permanent error
+    except smtplib.SMTPException:
+      pass		# any other error, try next MX
+    except socket.error:
+      pass		# MX didn't accept connections, try next one
+    smtp.close()
+  return (450,'No MX servers available')	# temp error
+
+def create_msg(q,rcptlist,origmsg):
+  heloname = q.h
+  sender = q.s
+  connectip = q.i
+  receiver = q.r
+  sender_domain = q.o
+  rcpt = '\n\t'.join(rcptlist)
+  try: subject = origmsg['Subject']
+  except: subject = '(none)'
+  try:
+    spf_result = origmsg['Received-SPF']
+    if not spf_result.startswith('softfail'):
+      spf_result = None
+  except: spf_result = None
+  msg = Message()
+  msg.add_header('To',sender)
+  msg.add_header('From','postmaster@%s'%receiver)
+  msg.add_header('Auto-Submitted','auto-generated (configuration error)')
+  msg.set_type('text/plain')
+  if spf_result:
+    msg.add_header('Subject','SPF softfail (POSSIBLE FORGERY)')
+    msg.set_payload(softfail_msg % locals())
+  else:
+    msg.add_header('Subject','Critical mail server configuration error')
+    msg.set_payload(nospf_msg % locals())
+  return msg
+
+if __name__ == '__main__':
+  q = spf.query('192.168.9.50',
+  'SRS0=pmeHL=RH=bmsi.com=stuart@bmsi.com',
+  'bmsred.bmsi.com',receiver='mail.bmsi.com')
+  msg = create_msg(q,'charlie@jsconnor.com')
+  #print msg.as_string()
+  # print send_dsn(f,msg.as_string())
+  print send_dsn(q.s,'mail.bmsi.com',msg.as_string())