#!/usr/bin/env python # A simple milter that has grown quite a bit. # $Log$ # Revision 1.110 2007/07/02 03:06:10 customdesigned # Ban ips on bad mailfrom offenses as well as bad rcpts. # # Revision 1.109 2007/06/23 20:53:05 customdesigned # Ban IPs based on too many invalid recipients in a connection. Requires # configuring check_user. Tighten HELO best_guess policy. # # Revision 1.108 2007/04/19 16:02:43 customdesigned # Do not process valid SRS recipients as delayed_failure. # # Revision 1.107 2007/04/15 01:01:13 customdesigned # Ban ips with too many bad rcpts on a connection. # # Revision 1.105 2007/04/13 17:20:09 customdesigned # Check access_file at startup. Compress rcpt to log. # # Revision 1.104 2007/04/05 17:59:07 customdesigned # Stop querying gossip server twice. # # Revision 1.103 2007/04/02 18:37:25 customdesigned # Don't disable gossip for temporary error. # # Revision 1.102 2007/03/30 18:13:41 customdesigned # Report bestguess and helo-spf as key-value pairs in Received-SPF # instead of in their own headers. # # Revision 1.101 2007/03/29 03:06:10 customdesigned # Don't count DSN and unqualified MAIL FROM as internal_domain. # # Revision 1.100 2007/03/24 00:30:24 customdesigned # Do not CBV for internal domains. # # Revision 1.99 2007/03/23 22:39:10 customdesigned # Get SMTP-Auth policy from access_file. # # Revision 1.98 2007/03/21 04:02:13 customdesigned # Properly log From: and Sender: # # Revision 1.97 2007/03/18 02:32:21 customdesigned # Gossip configuration options: client or standalone with optional peers. # # Revision 1.96 2007/03/17 21:22:48 customdesigned # New delayed DSN pattern. Retab (expandtab). # # Revision 1.95 2007/03/03 19:18:57 customdesigned # Fix continuing findsrs when srs.reverse fails. # # Revision 1.94 2007/03/03 18:46:26 customdesigned # Improve delayed failure detection. # # Revision 1.93 2007/02/07 23:21:26 customdesigned # Use re for auto-reply recognition. # # Revision 1.92 2007/01/26 03:47:23 customdesigned # Handle null in header value. # # Revision 1.91 2007/01/25 22:47:25 customdesigned # Persist blacklisting from delayed DSNs. # # Revision 1.90 2007/01/23 19:46:20 customdesigned # Add private relay. # # Revision 1.89 2007/01/22 02:46:01 customdesigned # Convert tabs to spaces. # # Revision 1.88 2007/01/19 23:31:38 customdesigned # Move parse_header to Milter.utils. # Test case for delayed DSN parsing. # Fix plock when source missing or cannot set owner/group. # # Revision 1.87 2007/01/18 16:48:44 customdesigned # Doc update. # Parse From header for delayed failure detection. # Don't check reputation of trusted host. # Track IP reputation only when missing PTR. # # Revision 1.86 2007/01/16 05:17:29 customdesigned # REJECT after data for blacklisted emails - so in case of mistakes, a # legitimate sender will know what happened. # # Revision 1.85 2007/01/11 04:31:26 customdesigned # Negative feedback for bad headers. Purge cache logs on startup. # # Revision 1.84 2007/01/10 04:44:25 customdesigned # Documentation updates. # # Revision 1.83 2007/01/08 23:20:54 customdesigned # Get user feedback. # # Revision 1.82 2007/01/06 04:21:30 customdesigned # Add config file to spfmilter # # Revision 1.81 2007/01/05 23:33:55 customdesigned # Make blacklist an AddrCache # # Revision 1.80 2007/01/05 23:12:12 customdesigned # Move parse_addr, iniplist, ip4re to Milter.utils # # Revision 1.79 2007/01/05 21:25:40 customdesigned # Move AddrCache to Milter package. # # Revision 1.78 2007/01/04 18:01:10 customdesigned # Do plain CBV when template missing. # # Revision 1.77 2006/12/31 03:07:20 customdesigned # Use HELO identity if good when MAILFROM is bad. # # Revision 1.76 2006/12/30 18:58:53 customdesigned # Skip reputation/whitelist/blacklist when rejecting on SPF. Add X-Hello-SPF. # # Revision 1.75 2006/12/28 01:54:32 customdesigned # Reject on bad_reputation or blacklist and nodspam. Match valid helo like # PTR for guessed SPF pass. # # Revision 1.74 2006/12/19 00:59:30 customdesigned # Add archive option to wiretap. # # Revision 1.73 2006/12/04 18:47:03 customdesigned # Reject multiple recipients to DSN. # Auto-disable gossip on DB error. # # Revision 1.72 2006/11/22 16:31:22 customdesigned # SRS domains were missing srs_reject check when SES was active. # # Revision 1.71 2006/11/22 01:03:28 customdesigned # Replace last use of deprecated rfc822 module. # # Revision 1.70 2006/11/21 18:45:49 customdesigned # Update a use of deprecated rfc822. Recognize report-type=delivery-status # # See ChangeLog # # Author: Stuart D. Gathman <stuart@bmsi.com> # Copyright 2001,2002,2003,2004,2005 Business Management Systems, Inc. # This code is under the GNU General Public License. See COPYING for details. import sys import os import StringIO import mime import email.Errors import Milter import tempfile import time import socket import re import shutil import gc import anydbm import Milter.dsn as dsn from Milter.dynip import is_dynip as dynip from Milter.utils import iniplist,parse_addr,parse_header,ip4re,addr2bin from Milter.config import MilterConfigParser from fnmatch import fnmatchcase from email.Utils import getaddresses,parseaddr # Import gossip if available try: import gossip import gossip.client import gossip.server except: gossip = None # Import pysrs if available try: import SRS srsre = re.compile(r'^SRS[01][+-=]',re.IGNORECASE) except: SRS = None try: import SES except: SES = None # Import spf if available try: import spf except: spf = None # Sometimes, MTAs reply to our DSN. We recognize this type of reply/DSN # and check for the original recipient SRS encoded in Message-ID. # If found, we blacklist that recipient. _subjpats = ( r'^failure notice', r'^subjectbounce', r'^returned mail', r'^undeliver', r'\bdelivery\b.*\bfail', r'\bdelivery problem', r'\bnot\s+be\s+delivered', r'\buser unknown\b', r'^failed', r'^mail failed', r'^echec de distribution', r'\berror\s+sending\b', r'^fallo en la entrega', r'\bfehlgeschlagen\b' ) refaildsn = re.compile('|'.join(_subjpats),re.IGNORECASE) # We don't want to whitelist recipients of Autoreplys and other robots. # There doesn't seem to be a foolproof way to recognize these, so # we use this heuristic. The worst that can happen is someone won't get # whitelisted when they should, or we'll whitelist some spammer for a while. _autopats = ( r'^read:', r'\bautoreply:\b', r'^return receipt', r'^Your message\b.*\bawaits moderator approval' ) reautoreply = re.compile('|'.join(_autopats),re.IGNORECASE) import logging # Thanks to Chris Liechti for config parsing suggestions # Global configuration defaults suitable for test framework. socketname = "/tmp/pythonsock" reject_virus_from = () wiretap_users = {} discard_users = {} wiretap_dest = None mail_archive = None _archive_lock = None blind_wiretap = True check_user = {} block_forward = {} hide_path = () log_headers = False block_chinese = False case_sensitive_localpart = False spam_words = () porn_words = () banned_exts = mime.extlist.split(',') scan_zip = False scan_html = True scan_rfc822 = True internal_connect = () trusted_relay = () private_relay = () trusted_forwarder = () internal_domains = () banned_users = () hello_blacklist = () smart_alias = {} dspam_dict = None dspam_users = {} dspam_userdir = None dspam_exempt = {} dspam_whitelist = {} whitelist_senders = {} dspam_screener = () dspam_internal = True # True if internal mail should be dspammed dspam_reject = () dspam_sizelimit = 180000 srs = None ses = None srs_reject_spoofed = False srs_domain = None spf_reject_neutral = () spf_accept_softfail = () spf_accept_fail = () spf_best_guess = False spf_reject_noptr = False supply_sender = False access_file = None timeout = 600 banned_ips = set() logging.basicConfig( stream=sys.stdout, level=logging.INFO, format='%(asctime)s %(message)s', datefmt='%Y%b%d %H:%M:%S' ) milter_log = logging.getLogger('milter') def read_config(list): cp = MilterConfigParser({ 'tempdir': "/var/log/milter/save", 'socket': "/var/run/milter/pythonsock", 'timeout': '600', 'scan_html': 'no', 'scan_rfc822': 'yes', 'scan_zip': 'no', 'block_chinese': 'no', 'log_headers': 'no', 'blind_wiretap': 'yes', 'maxage': '8', 'hashlength': '8', 'reject_spoofed': 'no', 'reject_noptr': 'no', 'supply_sender': 'no', 'best_guess': 'no', 'dspam_internal': 'yes', 'case_sensitive_localpart': 'no' }) cp.read(list) if cp.has_option('milter','datadir'): os.chdir(cp.get('milter','datadir')) # milter section tempfile.tempdir = cp.get('milter','tempdir') global socketname, timeout, check_user, log_headers global internal_connect, internal_domains, trusted_relay, hello_blacklist global case_sensitive_localpart, private_relay socketname = cp.get('milter','socket') timeout = cp.getint('milter','timeout') check_user = cp.getaddrset('milter','check_user') log_headers = cp.getboolean('milter','log_headers') internal_connect = cp.getlist('milter','internal_connect') internal_domains = cp.getlist('milter','internal_domains') trusted_relay = cp.getlist('milter','trusted_relay') private_relay = cp.getlist('milter','private_relay') hello_blacklist = cp.getlist('milter','hello_blacklist') case_sensitive_localpart = cp.getboolean('milter','case_sensitive_localpart') # defang section global scan_rfc822, scan_html, block_chinese, scan_zip, block_forward global banned_exts, porn_words, spam_words if cp.has_section('defang'): section = 'defang' # for backward compatibility, # banned extensions defaults to empty only when defang section exists banned_exts = cp.getlist(section,'banned_exts') else: # use milter section if no defang section for compatibility section = 'milter' scan_rfc822 = cp.getboolean(section,'scan_rfc822') scan_zip = cp.getboolean(section,'scan_zip') scan_html = cp.getboolean(section,'scan_html') block_chinese = cp.getboolean(section,'block_chinese') block_forward = cp.getaddrset(section,'block_forward') porn_words = cp.getlist(section,'porn_words') spam_words = cp.getlist(section,'spam_words') # scrub section global hide_path, reject_virus_from hide_path = cp.getlist('scrub','hide_path') reject_virus_from = cp.getlist('scrub','reject_virus_from') # wiretap section global blind_wiretap,wiretap_users,wiretap_dest,discard_users,mail_archive blind_wiretap = cp.getboolean('wiretap','blind') wiretap_users = cp.getaddrset('wiretap','users') discard_users = cp.getaddrset('wiretap','discard') wiretap_dest = cp.getdefault('wiretap','dest') if wiretap_dest: wiretap_dest = '<%s>' % wiretap_dest mail_archive = cp.getdefault('wiretap','archive') global smart_alias for sa,v in [ (k,cp.get('wiretap',k)) for k in cp.getlist('wiretap','smart_alias') ] + (cp.has_section('smart_alias') and cp.items('smart_alias',True) or []): print sa,v sm = [q.strip() for q in v.split(',')] if len(sm) < 2: milter_log.warning('malformed smart alias: %s',sa) continue if len(sm) == 2: sm.append(sa) if case_sensitive_localpart: key = (sm[0],sm[1]) else: key = (sm[0].lower(),sm[1].lower()) smart_alias[key] = sm[2:] # dspam section global dspam_dict, dspam_users, dspam_userdir, dspam_exempt, dspam_internal global dspam_screener,dspam_whitelist,dspam_reject,dspam_sizelimit global whitelist_senders whitelist_senders = cp.getaddrset('dspam','whitelist_senders') dspam_dict = cp.getdefault('dspam','dspam_dict') dspam_exempt = cp.getaddrset('dspam','dspam_exempt') dspam_whitelist = cp.getaddrset('dspam','dspam_whitelist') dspam_users = cp.getaddrdict('dspam','dspam_users') dspam_userdir = cp.getdefault('dspam','dspam_userdir') dspam_screener = cp.getlist('dspam','dspam_screener') dspam_reject = cp.getlist('dspam','dspam_reject') dspam_internal = cp.getboolean('dspam','dspam_internal') if cp.has_option('dspam','dspam_sizelimit'): dspam_sizelimit = cp.getint('dspam','dspam_sizelimit') # spf section global spf_reject_neutral,spf_best_guess,SRS,spf_reject_noptr global spf_accept_softfail,spf_accept_fail,supply_sender,access_file global trusted_forwarder if spf: spf.DELEGATE = cp.getdefault('spf','delegate') spf_reject_neutral = cp.getlist('spf','reject_neutral') spf_accept_softfail = cp.getlist('spf','accept_softfail') spf_accept_fail = cp.getlist('spf','accept_fail') spf_best_guess = cp.getboolean('spf','best_guess') spf_reject_noptr = cp.getboolean('spf','reject_noptr') supply_sender = cp.getboolean('spf','supply_sender') access_file = cp.getdefault('spf','access_file') trusted_forwarder = cp.getlist('spf','trusted_forwarder') srs_config = cp.getdefault('srs','config') if srs_config: cp.read([srs_config]) srs_secret = cp.getdefault('srs','secret') if SRS and srs_secret: global ses,srs,srs_reject_spoofed,srs_domain,banned_users database = cp.getdefault('srs','database') srs_reject_spoofed = cp.getboolean('srs','reject_spoofed') maxage = cp.getint('srs','maxage') hashlength = cp.getint('srs','hashlength') separator = cp.getdefault('srs','separator','=') if database: import SRS.DB srs = SRS.DB.DB(database=database,secret=srs_secret, maxage=maxage,hashlength=hashlength,separator=separator) else: srs = SRS.Guarded.Guarded(secret=srs_secret, maxage=maxage,hashlength=hashlength,separator=separator) if SES: ses = SES.new(secret=srs_secret,expiration=maxage) srs_domain = set(cp.getlist('srs','ses')) srs_domain.update(cp.getlist('srs','srs')) else: srs_domain = set(cp.getlist('srs','srs')) srs_domain.update(cp.getlist('srs','sign')) srs_domain.add(cp.getdefault('srs','fwdomain')) banned_users = cp.getlist('srs','banned_users') if gossip: global gossip_node if cp.has_option('gossip','server'): server = cp.get('gossip','server') host,port = gossip.splitaddr(server) gossip_node = gossip.client.Gossip(host,port) else: gossip_node = gossip.server.Gossip('gossip4.db',1000) for p in cp.getlist('gossip','peers'): host,port = gossip.splitaddr(p) gossip_node.peers.append(gossip.server.Peer(host,port)) def findsrs(fp): lastln = None for ln in fp: if lastln: if ln[0].isspace() and ln[0] != '\n': lastln += ln continue try: name,val = lastln.rstrip().split(None,1) pos = val.find('<SRS') if pos >= 0: end = val.find('>',pos+4) return srs.reverse(val[pos+1:end]) except: pass lnl = ln.lower() if lnl.startswith('action:'): if lnl.split()[-1] != 'failed': break for k in ('message-id:','x-mailer:','sender:','references:'): if lnl.startswith(k): lastln = ln break class SPFPolicy(object): "Get SPF policy by result from sendmail style access file." def __init__(self,sender): self.sender = sender self.domain = sender.split('@')[-1].lower() if access_file: try: acf = anydbm.open(access_file,'r') except: acf = None else: acf = None self.acf = acf def close(self): if self.acf: self.acf.close() def getPolicy(self,pfx): acf = self.acf if not acf: return None try: return acf[pfx + self.sender] except KeyError: try: return acf[pfx + self.domain] except KeyError: try: return acf[pfx] except KeyError: return None def getFailPolicy(self): policy = self.getPolicy('spf-fail:') if not policy: if self.domain in spf_accept_fail: policy = 'CBV' else: policy = 'REJECT' return policy def getNonePolicy(self): policy = self.getPolicy('spf-none:') if not policy: if spf_reject_noptr: policy = 'REJECT' else: policy = 'CBV' return policy def getSoftfailPolicy(self): policy = self.getPolicy('spf-softfail:') if not policy: if self.domain in spf_accept_softfail: policy = 'OK' elif self.domain in spf_reject_neutral: policy = 'REJECT' else: policy = 'CBV' return policy def getNeutralPolicy(self): policy = self.getPolicy('spf-neutral:') if not policy: if self.domain in spf_reject_neutral: policy = 'REJECT' policy = 'OK' return policy def getPermErrorPolicy(self): policy = self.getPolicy('spf-permerror:') if not policy: policy = 'REJECT' return policy def getPassPolicy(self): policy = self.getPolicy('spf-pass:') if not policy: policy = 'OK' return policy from Milter.cache import AddrCache cbv_cache = AddrCache(renew=7) cbv_cache.load('send_dsn.log',age=30) auto_whitelist = AddrCache(renew=30) auto_whitelist.load('auto_whitelist.log',age=120) blacklist = AddrCache(renew=30) blacklist.load('blacklist.log',age=60) class bmsMilter(Milter.Milter): """Milter to replace attachments poisonous to Windows with a WARNING message, check SPF, and other anti-forgery features, and implement wiretapping and smart alias redirection.""" def log(self,*msg): milter_log.info('[%d] %s',self.id,' '.join([str(m) for m in msg])) def __init__(self): self.tempname = None self.mailfrom = None # sender in SMTP form self.canon_from = None # sender in end user form self.fp = None self.bodysize = 0 self.id = Milter.uniqueID() # delrcpt can only be called from eom(). This accumulates recipient # changes which can then be applied by alter_recipients() def del_recipient(self,rcpt): rcpt = rcpt.lower() if not rcpt in self.discard_list: self.discard_list.append(rcpt) # addrcpt can only be called from eom(). This accumulates recipient # changes which can then be applied by alter_recipients() def add_recipient(self,rcpt): rcpt = rcpt.lower() if not rcpt in self.redirect_list: self.redirect_list.append(rcpt) # addheader can only be called from eom(). This accumulates added headers # which can then be applied by alter_headers() def add_header(self,name,val,idx=-1): self.new_headers.append((name,val,idx)) self.log('%s: %s' % (name,val)) def connect(self,hostname,unused,hostaddr): self.internal_connection = False self.trusted_relay = False # sometimes people put extra space in sendmail config, so we strip self.receiver = self.getsymval('j').strip() if hostaddr and len(hostaddr) > 0: ipaddr = hostaddr[0] if iniplist(ipaddr,internal_connect): self.internal_connection = True if iniplist(ipaddr,trusted_relay): self.trusted_relay = True else: ipaddr = '' self.connectip = ipaddr self.missing_ptr = dynip(hostname,self.connectip) if self.internal_connection: connecttype = 'INTERNAL' else: connecttype = 'EXTERNAL' if self.trusted_relay: connecttype += ' TRUSTED' if self.missing_ptr: connecttype += ' DYN' self.log("connect from %s at %s %s" % (hostname,hostaddr,connecttype)) if addr2bin(ipaddr) in banned_ips: self.log("REJECT: BANNED IP") self.setreply('550','5.7.1', 'Banned for dictionary attacks') return Milter.REJECT self.hello_name = None self.connecthost = hostname if hostname == 'localhost' and not ipaddr.startswith('127.') \ or hostname == '.': self.log("REJECT: PTR is",hostname) self.setreply('550','5.7.1', '"%s" is not a reasonable PTR name'%hostname) return Milter.REJECT self.offenses = 0 return Milter.CONTINUE def hello(self,hostname): self.hello_name = hostname self.log("hello from %s" % hostname) if ip4re.match(hostname): self.log("REJECT: numeric hello name:",hostname) self.setreply('550','5.7.1','hello name cannot be numeric ip') return Milter.REJECT if not self.internal_connection and hostname in hello_blacklist: self.log("REJECT: spam from self:",hostname) self.setreply('550','5.7.1', 'Your mail server lies. Its name is *not* %s.' % hostname) return Milter.REJECT if hostname == 'GC': n = gc.collect() self.log("gc:",n,' unreachable objects') self.log("auto-whitelist:",len(auto_whitelist),' entries') self.log("cbv_cache:",len(cbv_cache),' entries') self.setreply('550','5.7.1','%d unreachable objects'%n) return Milter.REJECT return Milter.CONTINUE def smart_alias(self,to): if smart_alias: if case_sensitive_localpart: t = parse_addr(to) else: t = parse_addr(to.lower()) if len(t) == 2: ct = '@'.join(t) else: ct = t[0] if case_sensitive_localpart: cf = self.canon_from else: cf = self.canon_from.lower() cf0 = cf.split('@',1) if len(cf0) == 2: cf0 = '@' + cf0[1] else: cf0 = cf for key in ((cf,ct),(cf0,ct)): if smart_alias.has_key(key): self.del_recipient(to) for t in smart_alias[key]: self.add_recipient('<%s>'%t) def offense(self,inc=1): self.offenses += inc if self.offenses > 3: try: ip = addr2bin(self.connectip) if ip not in banned_ips: banned_ips.add(ip) print >>open('banned_ips','a'),self.connectip except: pass return Milter.REJECT # multiple messages can be received on a single connection # envfrom (MAIL FROM in the SMTP protocol) seems to mark the start # of each message. def envfrom(self,f,*str): self.log("mail from",f,str) self.fp = StringIO.StringIO() self.tempname = None self.mailfrom = f self.forward = True self.bodysize = 0 self.hidepath = False self.discard = False self.dspam = True self.whitelist = False self.blacklist = False self.reject_spam = True self.data_allowed = True self.delayed_failure = None self.trust_received = self.trusted_relay self.trust_spf = self.trusted_relay self.redirect_list = [] self.discard_list = [] self.new_headers = [] self.recipients = [] self.cbv_needed = None self.whitelist_sender = False self.postmaster_reply = False t = parse_addr(f) if len(t) == 2: t[1] = t[1].lower() self.canon_from = '@'.join(t) # Some braindead MTAs can't be relied upon to properly flag DSNs. # This heuristic tries to recognize such. self.is_bounce = (f == '<>' or t[0].lower() in banned_users #and t[1] == self.hello_name ) # Check SMTP AUTH, also available: # auth_authen authenticated user # auth_author (ESMTP AUTH= param) # auth_ssf (connection security, 0 = unencrypted) # auth_type (authentication method, CRAM-MD5, DIGEST-MD5, PLAIN, etc) # cipher_bits SSL encryption strength # cert_subject SSL cert subject # verify SSL cert verified self.user = self.getsymval('{auth_authen}') if self.user: # Very simple SMTP AUTH policy by defaul: # any successful authentication is considered INTERNAL # FIXME: configure allowed MAIL FROM by user self.internal_connection = True self.log( "SMTP AUTH:",self.user, self.getsymval('{auth_type}'), "sslbits =",self.getsymval('{cipher_bits}'), "ssf =",self.getsymval('{auth_ssf}'), "INTERNAL" ) if self.getsymval('{verify}'): self.log("SSL AUTH:", self.getsymval('{cert_subject}'), "verify =",self.getsymval('{verify}') ) self.fp.write('From %s %s\n' % (self.canon_from,time.ctime())) self.internal_domain = False if len(t) == 2: user,domain = t for pat in internal_domains: if fnmatchcase(domain,pat): self.internal_domain = True break if self.internal_connection: if self.user: p = SPFPolicy('%s@%s'%(self.user,domain)) policy = p.getPolicy('smtp-auth:') p.close() else: policy = None if policy: if policy != 'OK': self.log("REJECT: unauthorized user",self.user, "at",self.connectip,"sending MAIL FROM",self.canon_from) self.setreply('550','5.7.1', 'SMTP user %s is not authorized to use MAIL FROM %s.' % (self.user,self.canon_from) ) return Milter.REJECT elif internal_domains and not self.internal_domain: self.log("REJECT: zombie PC at ",self.connectip, " sending MAIL FROM ",self.canon_from) self.setreply('550','5.7.1', 'Your PC is using an unauthorized MAIL FROM.', 'It is either badly misconfigured or controlled by organized crime.' ) return Milter.REJECT wl_users = whitelist_senders.get(domain,()) if user in wl_users or '' in wl_users: self.whitelist_sender = True self.rejectvirus = domain in reject_virus_from if user in wiretap_users.get(domain,()): self.add_recipient(wiretap_dest) self.smart_alias(wiretap_dest) if user in discard_users.get(domain,()): self.discard = True exempt_users = dspam_whitelist.get(domain,()) if user in exempt_users or '' in exempt_users: self.dspam = False else: self.rejectvirus = False domain = None if not self.hello_name: self.log("REJECT: missing HELO") self.setreply('550','5.7.1',"It's polite to say HELO first.") return Milter.REJECT self.umis = None self.spf = None if not (self.internal_connection or self.trusted_relay) \ and self.connectip and spf: rc = self.check_spf() if rc != Milter.CONTINUE: if rc != Milter.TEMPFAIL: self.offense() return rc else: rc = Milter.CONTINUE # FIXME: parse Received-SPF from trusted_relay for SPF result res = self.spf and self.spf_guess hres = self.spf and self.spf_helo # Check whitelist and blacklist if auto_whitelist.has_key(self.canon_from): if res == 'pass' or self.trusted_relay: self.whitelist = True self.log("WHITELIST",self.canon_from) else: self.dspam = False self.log("PROBATION",self.canon_from) elif cbv_cache.has_key(self.canon_from) and cbv_cache[self.canon_from] \ or domain in blacklist: if not self.internal_connection: self.offense() if not dspam_userdir: if domain in blacklist: self.log('REJECT: BLACKLIST',self.canon_from) self.setreply('550','5.7.1', 'Sender email local blacklist') else: res = cbv_cache[self.canon_from] desc = "CBV: %d %s" % res[:2] self.log('REJECT:',desc) self.setreply('550','5.7.1',*desc.splitlines()) return Milter.REJECT self.blacklist = True self.log("BLACKLIST",self.canon_from) else: global gossip if gossip and domain and rc == Milter.CONTINUE \ and not (self.internal_connection or self.trusted_relay): if self.spf and self.spf.result == 'pass': qual = 'SPF' elif res == 'pass': qual = 'GUESS' elif hres == 'pass': qual = 'HELO' domain = self.spf.h else: # No good identity: blame purported domain. Qualify by SPF # result so NEUTRAL will get separate reputation from SOFTFAIL. qual = res try: umis = gossip.umis(domain+qual,self.id+time.time()) res = gossip_node.query(umis,domain,qual,1) if res: res,hdr,val = res self.add_header(hdr,val) a = val.split(',') self.reputation = int(a[-2]) self.confidence = int(a[-1]) self.umis = umis # We would like to reject on bad reputation here, but we # need to give special consideration to postmaster. So # we have to wait until envrcpt(). Perhaps an especially # bad reputation could be rejected here. if self.reputation < -70 and self.confidence > 5: self.log('REJECT: REPUTATION') self.setreply('550','5.7.1', 'Your domain has been sending nothing but spam') return Milter.REJECT except: gossip = None raise return rc def check_spf(self): receiver = self.receiver for tf in trusted_forwarder: q = spf.query(self.connectip,'',tf,receiver=receiver,strict=False) res,code,txt = q.check() if res == 'none': res,code,txt = q.best_guess('v=spf1 a mx') if res == 'pass': self.log("TRUSTED_FORWARDER:",tf) break else: q = spf.query(self.connectip,self.canon_from,self.hello_name, receiver=receiver,strict=False) q.set_default_explanation( 'SPF fail: see http://openspf.org/why.html?sender=%s&ip=%s' % (q.s,q.i)) res,code,txt = q.check() q.result = res if res in ('unknown','permerror') and q.perm_error and q.perm_error.ext: self.cbv_needed = (q,res) # report SPF syntax error to sender res,code,txt = q.perm_error.ext # extended (lax processing) result txt = 'EXT: ' + txt p = SPFPolicy(q.s) # FIXME: try:finally to close policy db, or reuse with lock hres = None if res not in ('pass','error','temperror'): if self.mailfrom != '<>': # check hello name via spf unless spf pass h = spf.query(self.connectip,'',self.hello_name,receiver=receiver) hres,hcode,htxt = h.check() # FIXME: in a few cases, rejecting on HELO neutral causes problems # for senders forced to use their braindead ISPs email service. if hres in ('deny','fail','neutral','softfail'): self.log('REJECT: hello SPF: %s 550 %s' % (hres,htxt)) self.setreply('550','5.7.1',htxt, "The hostname given in your MTA's HELO response is not listed", "as a legitimate MTA in the SPF records for your domain. If you", "get this bounce, the message was not in fact a forgery, and you", "should IMMEDIATELY notify your email administrator of the problem." ) return Milter.REJECT if hres == 'none' and spf_best_guess \ and not dynip(self.hello_name,self.connectip): # HELO must match more exactly. Don't match PTR or zombies # will be able to get a best_guess pass on their ISPs domain. hres,hcode,htxt = h.best_guess('v=spf1 a mx') else: hres,hcode,htxt = res,code,txt ores = res if self.internal_domain and res == 'none': # we don't accept our own domains externally without an SPF record self.log('REJECT: spam from self',q.o) self.setreply('550','5.7.1',"I hate talking to myself!") return Milter.REJECT if spf_best_guess and res == 'none': #self.log('SPF: no record published, guessing') q.set_default_explanation( 'SPF guess: see http://openspf.org/why.html') # best_guess should not result in fail if self.missing_ptr: # ignore dynamic PTR for best guess res,code,txt = q.best_guess('v=spf1 a/24 mx/24') else: res,code,txt = q.best_guess() if res != 'pass' and hres == 'pass' and spf.domainmatch([q.h],q.o): res = 'pass' # get a guessed pass for valid matching HELO if self.missing_ptr and ores == 'none' and res != 'pass' \ and hres != 'pass': # this bad boy has no credentials whatsoever policy = p.getNonePolicy() if policy == 'CBV': if self.mailfrom != '<>': self.cbv_needed = (q,ores) # accept, but inform sender via DSN self.offenses = 3 # ban ip if any bad recipient elif policy != 'OK': self.log('REJECT: no PTR, HELO or SPF') self.setreply('550','5.7.1', "You must have a valid HELO or publish SPF: http://www.openspf.org ", "Contact your mail administrator IMMEDIATELY! Your mail server is ", "severely misconfigured. It has no PTR record (dynamic PTR records ", "that contain your IP don't count), an invalid or dynamic HELO, ", "and no SPF record." ) return Milter.REJECT if res in ('deny', 'fail'): policy = p.getFailPolicy() if policy == 'CBV': if self.mailfrom != '<>': self.cbv_needed = (q,res) elif policy != 'OK': self.log('REJECT: SPF %s %i %s' % (res,code,txt)) self.setreply(str(code),'5.7.1',txt) # A proper SPF fail error message would read: # forger.biz [1.2.3.4] is not allowed to send mail with the domain # "forged.org" in the sender address. Contact <postmaster@forged.org>. return Milter.REJECT if res == 'softfail': policy = p.getSoftfailPolicy() if policy == 'CBV': if self.mailfrom != '<>': self.cbv_needed = (q,res) elif policy != 'OK': self.log('REJECT: SPF %s %i %s' % (res,code,txt)) self.setreply('550','5.7.1', 'SPF softfail: If you get this Delivery Status Notice, your email', 'was probably legitimate. Your administrator has published SPF', 'records in a testing mode. The SPF record reported your email as', 'a forgery, which is a mistake if you are reading this. Please', 'notify your administrator of the problem immediately.' ) return Milter.REJECT if res == 'neutral': policy = p.getNeutralPolicy() if policy == 'CBV': if self.mailfrom != '<>': self.cbv_needed = (q,res) # FIXME: this makes Received-SPF show wrong result elif policy != 'OK': self.log('REJECT: SPF neutral for',q.s) self.setreply('550','5.7.1', 'mail from %s must pass SPF: http://openspf.org/why.html' % q.o, 'The %s domain is one that spammers love to forge. Due to' % q.o, 'the volume of forged mail, we can only accept mail that', 'the SPF record for %s explicitly designates as legitimate.' % q.o, 'Sending your email through the recommended outgoing SMTP', 'servers for %s should accomplish this.' % q.o ) return Milter.REJECT if res in ('unknown','permerror'): policy = p.getPermErrorPolicy() if policy == 'CBV': if self.mailfrom != '<>': self.cbv_needed = (q,res) elif policy != 'OK': self.log('REJECT: SPF %s %i %s' % (res,code,txt)) # latest SPF draft recommends 5.5.2 instead of 5.7.1 self.setreply(str(code),'5.5.2',txt, 'There is a fatal syntax error in the SPF record for %s' % q.o, 'We cannot accept mail from %s until this is corrected.' % q.o ) return Milter.REJECT if res in ('error','temperror'): self.log('TEMPFAIL: SPF %s %i %s' % (res,code,txt)) self.setreply(str(code),'4.3.0',txt) return Milter.TEMPFAIL kv = {} if hres and q.h != q.o: kv['helo_spf'] = hres if res != q.result: kv['bestguess'] = res self.add_header('Received-SPF',q.get_header(q.result,receiver,**kv),0) self.spf_guess = res self.spf_helo = hres self.spf = q return Milter.CONTINUE # hide_path causes a copy of the message to be saved - until we # track header mods separately from body mods - so use only # in emergencies. def envrcpt(self,to,*str): # mail to MAILER-DAEMON is generally spam that bounced if to.startswith('<MAILER-DAEMON@'): self.log('REJECT: RCPT TO:',to,str) return Milter.REJECT try: t = parse_addr(to) newaddr = False if len(t) == 2: t[1] = t[1].lower() user,domain = t if self.is_bounce and srs and domain in srs_domain: oldaddr = '@'.join(parse_addr(to)) try: if ses: newaddr = ses.verify(oldaddr) else: newaddr = oldaddr, if len(newaddr) > 1: newaddr = newaddr[0] self.log("ses rcpt:",newaddr) else: newaddr = srs.reverse(oldaddr) # Currently, a sendmail map reverses SRS. We just log it here. self.log("srs rcpt:",newaddr) self.dspam = False # verified as reply to mail we sent self.blacklist = False self.delayed_failure = False except: if not (self.internal_connection or self.trusted_relay): if srsre.match(oldaddr): self.log("REJECT: srs spoofed:",oldaddr) self.setreply('550','5.7.1','Invalid SRS signature') return Milter.REJECT if oldaddr.startswith('SES='): self.log("REJECT: ses spoofed:",oldaddr) self.setreply('550','5.7.1','Invalid SES signature') return Milter.REJECT # reject for certain recipients are delayed until after DATA if srs_reject_spoofed \ and not user.lower() in ('postmaster','abuse'): return self.forged_bounce() self.data_allowed = not srs_reject_spoofed if not self.internal_connection and domain in private_relay: self.log('REJECT: RELAY:',to) self.setreply('550','5.7.1','Unauthorized relay for %s' % domain) return Milter.REJECT # non DSN mail to SRS address will bounce due to invalid local part canon_to = '@'.join(t) if canon_to == 'postmaster@' + self.receiver: self.postmaster_reply = True self.recipients.append(canon_to) # FIXME: use newaddr to check rcpt users = check_user.get(domain) if self.discard: self.del_recipient(to) # don't check userlist if signed MFROM for now userl = user.lower() if users and not newaddr and not userl in users: self.log('REJECT: RCPT TO:',to,str) if gossip and self.umis: gossip_node.feedback(self.umis,1) self.umis = None return self.offense() # FIXME: should dspam_exempt be case insensitive? if user in block_forward.get(domain,()): self.forward = False exempt_users = dspam_exempt.get(domain,()) if user in exempt_users or '' in exempt_users: if self.blacklist: self.log('REJECT: BLACKLISTED, rcpt to',to,str) self.setreply('550','5.7.1','Sending domain has been blacklisted') return Milter.REJECT self.dspam = False if userl != 'postmaster' and self.umis \ and self.reputation < -50 and self.confidence > 1: self.log('REJECT: REPUTATION, rcpt to',to,str) self.setreply('550','5.7.1','Your domain has been sending mostly spam') return Milter.REJECT if domain in hide_path: self.hidepath = True if not domain in dspam_reject: self.reject_spam = False except: self.log("rcpt to",to,str) raise self.log("rcpt to",to,str) self.smart_alias(to) # get recipient after virtusertable aliasing #rcpt = self.getsymval("{rcpt_addr}") #self.log("rcpt-addr",rcpt); return Milter.CONTINUE # Heuristic checks for spam headers def check_header(self,name,val): lname = name.lower() # val is decoded header value if lname == 'subject': # check for common spam keywords for wrd in spam_words: if val.find(wrd) >= 0: self.log('REJECT: %s: %s' % (name,val)) self.setreply('550','5.7.1','That subject is not allowed') return Milter.REJECT # even if we wanted the Taiwanese spam, we can't read Chinese if block_chinese: if val.startswith('=?big5') or val.startswith('=?ISO-2022-JP'): self.log('REJECT: %s: %s' % (name,val)) self.setreply('550','5.7.1',"We don't understand chinese") return Milter.REJECT # check for spam that claims to be legal lval = val.lower().strip() for adv in ("adv:","adv.","adv ","[adv]","(adv)","advt:","advert:"): if lval.startswith(adv): self.log('REJECT: %s: %s' % (name,val)) self.setreply('550','5.7.1','Advertising not accepted here') return Milter.REJECT for adv in ("adv","(adv)","[adv]"): if lval.endswith(adv): self.log('REJECT: %s: %s' % (name,val)) self.setreply('550','5.7.1','Advertising not accepted here') return Milter.REJECT # check for porn keywords for w in porn_words: if lval.find(w) >= 0: self.log('REJECT: %s: %s' % (name,val)) self.setreply('550','5.7.1','That subject is not allowed') return Milter.REJECT # check for annoying forwarders if not self.forward: if lval.startswith("fwd:") or lval.startswith("[fw"): self.log('REJECT: %s: %s' % (name,val)) self.setreply('550','5.7.1','I find unedited forwards annoying') return Milter.REJECT # check for delayed bounce of CBV if self.postmaster_reply and srs: if refaildsn.search(lval): self.delayed_failure = val.strip() # if confirmed by finding our signed Message-ID, # original sender (encoded in Message-ID) is blacklisted elif lname == 'from': name,email = parseaddr(val) if email.lower().startswith('postmaster@'): # Yes, if From header comes last, this might not help much. # But this is a heuristic - if MTAs would send proper DSNs in # the first place, none of this would be needed. self.is_bounce = True # check for invalid message id elif lname == 'message-id' and len(val) < 4: self.log('REJECT: %s: %s' % (name,val)) return Milter.REJECT # check for common bulk mailers elif lname == 'x-mailer': mailer = val.lower() if mailer in ('direct email','calypso','mail bomber') \ or mailer.find('optin') >= 0: self.log('REJECT: %s: %s' % (name,val)) return Milter.REJECT return Milter.CONTINUE def forged_bounce(self): if self.mailfrom != '<>': self.log("REJECT: bogus DSN") self.setreply('550','5.7.1', "I do not accept normal mail from %s." % self.mailfrom.split('@')[0], "All such mail has turned out to be Delivery Status Notifications", "which failed to be marked as such. Please send a real DSN if", "you need to. Use another MAIL FROM if you need to send me mail." ) else: self.log('REJECT: bounce with no SRS encoding') self.setreply('550','5.7.1', "I did not send you that message. Please consider implementing SPF", "(http://openspf.org) to avoid bouncing mail to spoofed senders.", "Thank you." ) return Milter.REJECT def header(self,name,hval): if not self.data_allowed: return self.forged_bounce() lname = name.lower() # decode near ascii text to unobfuscate val = parse_header(hval) if not self.internal_connection and not (self.blacklist or self.whitelist): rc = self.check_header(name,val) if rc != Milter.CONTINUE: if gossip and self.umis: gossip_node.feedback(self.umis,1) return rc elif self.whitelist_sender and lname == 'subject': # check for AutoReplys if reautoreply.match(val): self.whitelist_sender = False self.log('AUTOREPLY: not whitelisted') # log selected headers if log_headers or lname in ('subject','x-mailer'): self.log('%s: %s' % (name,val)) elif self.trust_received and lname == 'received': self.trust_received = False self.log('%s: %s' % (name,val.splitlines()[0])) elif self.trust_spf and lname == 'received-spf': self.trust_spf = False self.log('%s: %s' % (name,val.splitlines()[0])) if self.fp: try: val = val.encode('us-ascii') except: val = hval self.fp.write("%s: %s\n" % (name,val)) # add header to buffer return Milter.CONTINUE def eoh(self): if not self.fp: return Milter.TEMPFAIL # not seen by envfrom if not self.data_allowed: return self.forged_bounce() for name,val,idx in self.new_headers: self.fp.write("%s: %s\n" % (name,val)) # add new headers to buffer self.fp.write("\n") # terminate headers if not self.internal_connection: msg = None # parse headers only if needed if not self.delayed_failure: self.fp.seek(0) msg = email.message_from_file(self.fp) if msg.get_param('report-type','').lower() == 'delivery-status': self.is_bounce = True self.delayed_failure = msg.get('subject','DSN') # log when neither sender nor from domains matches mail from domain if supply_sender and self.mailfrom != '<>': if not msg: self.fp.seek(0) msg = email.message_from_file(self.fp) mf_domain = self.canon_from.split('@')[-1] for rn,hf in getaddresses(msg.get_all('from',[]) + msg.get_all('sender',[])): t = parse_addr(hf) if len(t) == 2: hd = t[1].lower() if hd == mf_domain or mf_domain.endswith('.'+hd): break else: for f in msg.get_all('from',[]): self.log('From:',f) sender = msg.get_all('sender') if sender: for f in sender: self.log('Sender:',f) else: self.log("NOTE: Supplying MFROM as Sender"); self.add_header('Sender',self.mailfrom) del msg # copy headers to a temp file for scanning the body self.fp.seek(0) headers = self.fp.getvalue() self.fp.close() fd,fname = tempfile.mkstemp(".defang") self.tempname = fname self.fp = os.fdopen(fd,"w+b") self.fp.write(headers) # IOError (e.g. disk full) causes TEMPFAIL # check if headers are really spammy if dspam_dict and not self.internal_connection: ds = dspam.dspam(dspam_dict,dspam.DSM_PROCESS, dspam.DSF_CHAINED|dspam.DSF_CLASSIFY) try: ds.process(headers) if ds.probability > 0.93 and self.dspam and not self.whitelist: self.log('REJECT: X-DSpam-HeaderScore: %f' % ds.probability) self.setreply('550','5.7.1','Your Message looks spammy') return Milter.REJECT self.add_header('X-DSpam-HeaderScore','%f'%ds.probability) finally: ds.destroy() return Milter.CONTINUE def body(self,chunk): # copy body to temp file if self.fp: self.fp.write(chunk) # IOError causes TEMPFAIL in milter self.bodysize += len(chunk) return Milter.CONTINUE def _headerChange(self,msg,name,value): if value: # add header self.addheader(name,value) else: # delete all headers with name h = msg.getheaders(name) if h: for i in range(len(h),0,-1): self.chgheader(name,i-1,'') def _chk_ext(self,name): "Check a name for dangerous Winblows extensions." if not name: return name lname = name.lower() for ext in self.bad_extensions: if lname.endswith(ext): return name return None def _chk_attach(self,msg): "Filter attachments by content." # check for bad extensions mime.check_name(msg,self.tempname,ckname=self._chk_ext,scan_zip=scan_zip) # remove scripts from HTML if scan_html: mime.check_html(msg,self.tempname) # don't let a tricky virus slip one past us if scan_rfc822: msg = msg.get_submsg() if isinstance(msg,email.Message.Message): return mime.check_attachments(msg,self._chk_attach) return Milter.CONTINUE def alter_recipients(self,discard_list,redirect_list): for rcpt in discard_list: if rcpt in redirect_list: continue self.log("DISCARD RCPT: %s" % rcpt) # log discarded rcpt self.delrcpt(rcpt) for rcpt in redirect_list: if rcpt in discard_list: continue self.log("APPEND RCPT: %s" % rcpt) # log appended rcpt self.addrcpt(rcpt) if not blind_wiretap: self.addheader('Cc',rcpt) # def gossip_header(self): "Set UMIS from GOSSiP header." msg = email.message_from_file(self.fp) gh = msg.get('x-gossip') if gh: self.log('X-GOSSiP:',gh) self.umis,_ = gh.split(',',1) # check spaminess for recipients in dictionary groups # if there are multiple users getting dspammed, then # a signature tag for each is added to the message. # FIXME: quarantine messages rejected via fixed patterns above # this will give a fast start to stats def check_spam(self): "return True/False if self.fp, else return Milter.REJECT/TEMPFAIL/etc" self.screened = False if not dspam_userdir: return False ds = Dspam.DSpamDirectory(dspam_userdir) ds.log = self.log ds.headerchange = self._headerChange modified = False for rcpt in self.recipients: if dspam_users.has_key(rcpt.lower()): user = dspam_users.get(rcpt.lower()) if user: try: self.fp.seek(0) txt = self.fp.read() if user == 'spam' and self.internal_connection: sender = dspam_users.get(self.canon_from) if sender: self.log("SPAM: %s" % sender) # log user for SPAM ds.add_spam(sender,txt) txt = None self.fp.seek(0) self.gossip_header() self.fp = None return Milter.DISCARD elif user == 'falsepositive' and self.internal_connection: sender = dspam_users.get(self.canon_from) if sender: self.log("FP: %s" % sender) # log user for FP txt = ds.false_positive(sender,txt) self.fp = StringIO.StringIO(txt) self.gossip_header() self.delrcpt('<%s>' % rcpt) self.recipients = None self.rejectvirus = False return True elif not self.internal_connection or dspam_internal: if len(txt) > dspam_sizelimit: self.log("Large message:",len(txt)) return False if user == 'honeypot' and Dspam.VERSION >= '1.1.9': keep = False # keep honeypot mail self.fp = None if len(self.recipients) > 1: self.log("HONEYPOT:",rcpt,'SCREENED') if self.whitelist: # don't train when recipients includes honeypot return False if self.spf and self.mailfrom != '<>': # check that sender accepts quarantine DSN msg = mime.message_from_file(StringIO.StringIO(txt)) rc = self.send_dsn(self.spf,msg,'quarantine') del msg if rc != Milter.CONTINUE: return rc ds.check_spam(user,txt,self.recipients,quarantine=True, force_result=dspam.DSR_ISSPAM) else: ds.check_spam(user,txt,self.recipients,quarantine=keep, force_result=dspam.DSR_ISSPAM) self.log("HONEYPOT:",rcpt) return Milter.DISCARD if self.whitelist: # Sender whitelisted: tag, but force as ham. # User can change if actually spam. txt = ds.check_spam(user,txt,self.recipients, force_result=dspam.DSR_ISINNOCENT) elif self.blacklist: txt = ds.check_spam(user,txt,self.recipients, force_result=dspam.DSR_ISSPAM) else: txt = ds.check_spam(user,txt,self.recipients) if not txt: # DISCARD if quarrantined for any recipient. It # will be resent to all recipients if they submit # as a false positive. self.log("DSPAM:",user,rcpt) self.fp = None return Milter.DISCARD self.fp = StringIO.StringIO(txt) modified = True except Exception,x: self.log("check_spam:",x) milter_log.error("check_spam: %s",x,exc_info=True) # screen if no recipients are dspam_users if not modified and dspam_screener and not self.internal_connection \ and self.dspam: self.fp.seek(0) txt = self.fp.read() if len(txt) > dspam_sizelimit: self.log("Large message:",len(txt)) return False screener = dspam_screener[self.id % len(dspam_screener)] if not ds.check_spam(screener,txt,self.recipients, classify=True,quarantine=False): if self.whitelist: # messages is whitelisted but looked like spam, Train on Error self.log("TRAIN:",screener,'X-Dspam-Score: %f' % ds.probability) # user can't correct anyway if really spam, so discard tag ds.check_spam(screener,txt,self.recipients, force_result=dspam.DSR_ISINNOCENT) return False if self.reject_spam: self.log("DSPAM:",screener, 'REJECT: X-DSpam-Score: %f' % ds.probability) self.setreply('550','5.7.1','Your Message looks spammy') self.fp = None return Milter.REJECT self.log("DSPAM:",screener,"SCREENED") if self.spf and self.mailfrom != '<>': # check that sender accepts quarantine DSN self.fp.seek(0) msg = mime.message_from_file(self.fp) rc = self.send_dsn(self.spf,msg,'quarantine') if rc != Milter.CONTINUE: self.fp = None return rc del msg if not ds.check_spam(screener,txt,self.recipients,classify=True): self.fp = None return Milter.DISCARD # Message no longer looks spammy, deliver normally. We lied in the DSN. elif self.blacklist: # message is blacklisted but looked like ham, Train on Error self.log("TRAINSPAM:",screener,'X-Dspam-Score: %f' % ds.probability) ds.check_spam(screener,txt,self.recipients,quarantine=False, force_result=dspam.DSR_ISSPAM) self.fp = None self.setreply('550','5.7.1', 'Sender email local blacklist') return Milter.REJECT elif self.whitelist and ds.totals[1] < 1000: self.log("TRAIN:",screener,'X-Dspam-Score: %f' % ds.probability) # user can't correct anyway if really spam, so discard tag ds.check_spam(screener,txt,self.recipients, force_result=dspam.DSR_ISINNOCENT) return False # log spam score for screened messages self.add_header("X-DSpam-Score",'%f' % ds.probability) self.screened = True return modified # train late in eom(), after failed CBV # FIXME: need to undo if registered as ham with a dspam_user def train_spam(self): "Train screener with current message as spam" if not dspam_userdir: return if not dspam_screener: return ds = Dspam.DSpamDirectory(dspam_userdir) ds.log = self.log self.fp.seek(0) txt = self.fp.read() if len(txt) > dspam_sizelimit: self.log("Large message:",len(txt)) return screener = dspam_screener[self.id % len(dspam_screener)] # since message will be rejected, we do not quarantine ds.check_spam(screener,txt,self.recipients,force_result=dspam.DSR_ISSPAM, quarantine=False) self.log("TRAINSPAM:",screener,'X-Dspam-Score: %f' % ds.probability) def eom(self): if not self.fp: return Milter.ACCEPT # no message collected - so no eom processing if self.is_bounce and len(self.recipients) > 1: self.log("REJECT: DSN to multiple recipients") self.setreply('550','5.7.1', 'DSN to multiple recipients') return Milter.REJECT try: # check for delayed bounce if self.delayed_failure: self.fp.seek(0) sender = findsrs(self.fp) if sender: cbv_cache[sender] = 550,self.delayed_failure # make blacklisting persistent, since delayed DSNs are expensive blacklist[sender] = None try: # save message for debugging fname = tempfile.mktemp(".dsn") os.rename(self.tempname,fname) except: fname = self.tempname self.tempname = None self.log('BLACKLIST:',sender,fname) return Milter.DISCARD # analyze external mail for spam spam_checked = self.check_spam() # tag or quarantine for spam if not self.fp: if gossip and self.umis: gossip_node.feedback(self.umis,1) return spam_checked # analyze all mail for dangerous attachments and scripts self.fp.seek(0) msg = mime.message_from_file(self.fp) # pass header changes in top level message to sendmail msg.headerchange = self._headerChange # filter leaf attachments through _chk_attach assert not msg.ismodified() self.bad_extensions = ['.' + x for x in banned_exts] rc = mime.check_attachments(msg,self._chk_attach) except: # milter crashed trying to analyze mail exc_type,exc_value = sys.exc_info()[0:2] if dspam_userdir and exc_type == dspam.error: if not exc_value.strerror: exc_value.strerror = exc_value.args[0] if exc_value.strerror == 'Lock failed': milter_log.warn("LOCK: BUSY") # log filename self.setreply('450','4.2.0', 'Too busy discarding spam. Please try again later.') return Milter.TEMPFAIL fname = tempfile.mktemp(".fail") # save message that caused crash os.rename(self.tempname,fname) self.tempname = None if exc_type == email.Errors.BoundaryError: milter_log.warn("MALFORMED: %s",fname) # log filename if self.internal_connection: # accept anyway for now return Milter.ACCEPT self.setreply('554','5.7.7', 'Boundary error in your message, are you a spammer?') return Milter.REJECT if exc_type == email.Errors.HeaderParseError: milter_log.warn("MALFORMED: %s",fname) # log filename self.setreply('554','5.7.7', 'Header parse error in your message, are you a spammer?') return Milter.REJECT milter_log.error("FAIL: %s",fname) # log filename # let default exception handler print traceback and return 451 code raise if rc == Milter.REJECT: return rc; if rc == Milter.DISCARD: return rc; if rc == Milter.CONTINUE: rc = Milter.ACCEPT # for testbms.py compat defanged = msg.ismodified() if self.hidepath: del msg['Received'] if self.recipients == None: # false positive being recirculated self.recipients = msg.get_all('x-dspam-recipients',[]) if self.recipients: for rcptlist in self.recipients: for rcpt in rcptlist.split(','): self.addrcpt('<%s>' % rcpt.strip()) del msg['x-dspam-recipients'] else: self.addrcpt(self.mailfrom) else: self.alter_recipients(self.discard_list,self.redirect_list) # auto whitelist original recipients if not defanged and self.whitelist_sender: for canon_to in self.recipients: user,domain = canon_to.split('@') if internal_domains: for pat in internal_domains: if fnmatchcase(domain,pat): break else: auto_whitelist[canon_to] = None self.log('Auto-Whitelist:',canon_to) else: auto_whitelist[canon_to] = None self.log('Auto-Whitelist:',canon_to) for name,val,idx in self.new_headers: try: try: self.addheader(name,val,idx) except TypeError: val = val.replace('\x00',r'\x00') self.addheader(name,val,idx) except Milter.error: self.addheader(name,val) # older sendmail can't insheader # do not send CBV to internal domains (since we'll just get # the "Fraudulent MX" error). if self.cbv_needed and not self.internal_domain: q,res = self.cbv_needed if res == 'softfail': template_name = 'softfail' elif res in ('fail','deny'): template_name = 'fail' elif res in ('unknown','permerror'): template_name = 'permerror' elif res == 'neutral': template_name = 'neutral' else: template_name = 'strike3' rc = self.send_dsn(q,msg,template_name) self.cbv_needed = None if rc == Milter.REJECT: # Do not feedback here, because feedback should only occur # for messages that have gone to DATA. Reputation lets us # reject before DATA for persistent spam domains, saving # cycles and bandwidth. # Do feedback here, because CBV costs quite a bit more than # simply rejecting before DATA. Bad reputation will acrue to # the IP or HELO, since we won't get here for validated MAILFROM. # See Proverbs 26:4,5 if gossip and self.umis: gossip_node.feedback(self.umis,1) self.train_spam() return Milter.REJECT if rc != Milter.CONTINUE: return rc if mail_archive: global _archive_lock if not _archive_lock: import thread _archive_lock = thread.allocate_lock() _archive_lock.acquire() try: fin = open(self.tempname,'r') fout = open(mail_archive,'a') shutil.copyfileobj(fin,fout,8192) finally: _archive_lock.release() fin.close() fout.close() if not defanged and not spam_checked: if gossip and self.umis and self.screened: gossip_node.feedback(self.umis,0) os.remove(self.tempname) self.tempname = None # prevent re-removal self.log("eom") return rc # no modified attachments # Body modified, copy modified message to a temp file if defanged: if self.rejectvirus and not self.hidepath: self.log("REJECT virus from",self.mailfrom) self.setreply('550','5.7.1','Attachment type not allowed.', 'You attempted to send an attachment with a banned extension.') self.tempname = None return Milter.REJECT self.log("Temp file:",self.tempname) self.tempname = None # prevent removal of original message copy out = tempfile.TemporaryFile() try: msg.dump(out) out.seek(0) # Since we wrote headers with '\n' (no CR), # the following header/body split should always work. msg = out.read().split('\n\n',1)[-1] self.replacebody(msg) # feed modified message to sendmail if spam_checked: if gossip and self.umis: gossip_node.feedback(self.umis,0) self.log("dspam") return rc finally: out.close() return Milter.TEMPFAIL def send_dsn(self,q,msg,template_name): sender = q.s cached = cbv_cache.has_key(sender) if cached: self.log('CBV:',sender,'(cached)') res = cbv_cache[sender] else: fname = template_name+'.txt' try: template = file(template_name+'.txt').read() self.log('CBV:',sender,'Using:',fname) except IOError: template = None self.log('CBV:',sender,'PLAIN') m = dsn.create_msg(q,self.recipients,msg,template) if m: if srs: # Add SRS coded sender to various headers. When (incorrectly) # replying to our DSN, any of these which are preserved # allow us to track the source. msgid = srs.forward(sender,self.receiver) m.add_header('Message-Id','<%s>'%msgid) if 'x-mailer' in m: m.replace_header('x-mailer','"%s" <%s>' % (m['x-mailer'],msgid)) else: m.add_header('X-Mailer','"Python Milter" <%s>'%msgid) m.add_header('Sender','"Python Milter" <%s>'%msgid) m = m.as_string() print >>open(template_name+'.last_dsn','w'),m # if missing template, do plain CBV res = dsn.send_dsn(sender,self.receiver,m,timeout=timeout) if res: desc = "CBV: %d %s" % res[:2] if 400 <= res[0] < 500: self.log('TEMPFAIL:',desc) self.setreply('450','4.2.0',*desc.splitlines()) return Milter.TEMPFAIL cbv_cache[sender] = res self.log('REJECT:',desc) self.setreply('550','5.7.1',*desc.splitlines()) return Milter.REJECT cbv_cache[sender] = res return Milter.CONTINUE def close(self): if self.tempname: os.remove(self.tempname) # remove in case session aborted if self.fp: self.fp.close() return Milter.CONTINUE def abort(self): self.log("abort after %d body chars" % self.bodysize) return Milter.CONTINUE def main(): if access_file: try: acf = anydbm.open(access_file,'r') acf.close() except: milter_log.error('Unable to read: %s',access_file) return try: from glob import glob banned_ips = set(addr2bin(ip) for fn in glob('banned_ips*') for ip in open(fn)) print len(banned_ips),'banned ips' except: milter_log.exception('Error reading banned_ips') Milter.factory = bmsMilter flags = Milter.CHGBODY + Milter.CHGHDRS + Milter.ADDHDRS if wiretap_dest or smart_alias or dspam_userdir: flags = flags + Milter.ADDRCPT if srs or len(discard_users) > 0 or smart_alias or dspam_userdir: flags = flags + Milter.DELRCPT Milter.set_flags(flags) socket.setdefaulttimeout(60) milter_log.info("bms milter startup") Milter.runmilter("pythonfilter",socketname,timeout) milter_log.info("bms milter shutdown") if __name__ == "__main__": read_config(["/etc/mail/pymilter.cfg","milter.cfg"]) if dspam_dict: import dspam # low level spam check if dspam_userdir: import dspam import Dspam # high level spam check try: dspam_version = Dspam.VERSION except: dspam_version = '1.1.4' assert dspam_version >= '1.1.5' main()