#!/usr/bin/env python """SPF (Sender Policy Framework) implementation. Copyright (c) 2003, Terence Way Portions Copyright (c) 2004,2005 Stuart Gathman Portions Copyright (c) 2005 Scott Kitterman This module is free software, and you may redistribute it and/or modify it under the same terms as Python itself, so long as this copyright message and disclaimer are retained in their original form. IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF THIS CODE, EVEN IF THE AUTHOR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE CODE PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THERE IS NO OBLIGATION WHATSOEVER TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. For more information about SPF, a tool against email forgery, see http://www.openspf.org/ For news, bugfixes, etc. visit the home page for this implementation at http://www.wayforward.net/spf/ http://sourceforge.net/projects/pymilter/ """ # Changes: # 9-dec-2003, v1.1, Meng Weng Wong added PTR code, THANK YOU # 11-dec-2003, v1.2, ttw added macro expansion, exp=, and redirect= # 13-dec-2003, v1.3, ttw added %{o} original domain macro, # print spf result on command line, support default=, # support localhost, follow DNS CNAMEs, cache DNS results # during query, support Python 2.2 for Mac OS X # 16-dec-2003, v1.4, ttw fixed include handling (include is a mechanism, # complete with status results, so -include: should work. # Expand macros AFTER looking for status characters ?-+ # so altavista.com SPF records work. # 17-dec-2003, v1.5, ttw use socket.inet_aton() instead of DNS.addr2bin, so # n, n.n, and n.n.n forms for IPv4 addresses work, and to # ditch the annoying Python 2.4 FutureWarning # 18-dec-2003, v1.6, Failures on Intel hardware: endianness. Use ! on # struct.pack(), struct.unpack(). # # Development taken over by Stuart Gathman # and Scott Kitterman with # the blessing of Terrence Way. # # $Log: spf.py,v $ # Revision 1.26 2006/09/08 22:02:57 customdesigned # Merge changes from pyspf to pass test suite. # # Revision 1.25 2006/07/31 15:25:39 customdesigned # Permerror for multiple TXT SPF records. # # Revision 1.24 2006/07/28 01:21:33 customdesigned # Remove debug print # # Revision 1.23 2006/07/28 01:21:02 customdesigned # More fixes from pyspf # # Revision 1.22 2006/06/21 21:13:07 customdesigned # initialize perm_error # # Revision 1.21 2006/05/12 16:15:20 customdesigned # a:1.2.3.4 -> ip4:1.2.3.4 'lax' heuristic. # # Revision 1.20 2006/03/21 18:48:51 customdesigned # Import note_error from pyspf. Handle timeout on type99 lookup # specially (sender actually has no SPF record and a braindead DNS server). # # Revision 1.19 2006/02/24 02:12:54 customdesigned # Properly report hard PermError (lax mode fails also) by always setting # perm_error attribute with PermError exception. Improve reporting of # invalid domain PermError. # # Revision 1.18 2005/12/29 19:15:35 customdesigned # Handle NULL MX # # Revision 1.17 2005/12/23 21:44:15 customdesigned # Always include keyword data in Received-SPF header. # __author__ = "Terence Way" __email__ = "terry@wayforward.net" __version__ = "1.7: July 26, 2006" MODULE = 'spf' USAGE = """To check an incoming mail request: % python spf.py {ip} {sender} {helo} % python spf.py 69.55.226.139 tway@optsw.com mx1.wayforward.net To test an SPF record: % python spf.py "v=spf1..." {ip} {sender} {helo} % python spf.py "v=spf1 +mx +ip4:10.0.0.1 -all" 10.0.0.1 tway@foo.com a To fetch an SPF record: % python spf.py {domain} % python spf.py wayforward.net To test this script (and to output this usage message): % python spf.py """ import re import socket # for inet_ntoa() and inet_aton() import struct # for pack() and unpack() import time # for time() import DNS # http://pydns.sourceforge.net if not hasattr(DNS.Type,'SPF'): # patch in type99 support DNS.Type.SPF = 99 DNS.Type.typemap[99] = 'SPF' DNS.Lib.RRunpacker.getSPFdata = DNS.Lib.RRunpacker.getTXTdata def DNSLookup(name,qtype): try: req = DNS.DnsRequest(name, qtype=qtype) resp = req.req() #resp.show() # key k: ('wayforward.net', 'A'), value v return [((a['name'], a['typename']), a['data']) for a in resp.answers] except IOError,x: raise TempError,'DNS ' + str(x) except DNS.DNSError,x: raise TempError,'DNS ' + str(x) def isSPF(txt): "Return True if txt has SPF record signature." return txt.startswith('v=spf1 ') or txt == 'v=spf1' # 32-bit IPv4 address mask MASK = 0xFFFFFFFFL # Regular expression to look for modifiers RE_MODIFIER = re.compile(r'^([a-z][a-z0-9_\-\.]*)=',re.IGNORECASE) # Regular expression to find macro expansions RE_CHAR = re.compile(r'%(%|_|-|(\{[a-zA-Z][0-9]*r?[^\}]*\}))') # Regular expression to break up a macro expansion RE_ARGS = re.compile(r'([0-9]*)(r?)([^0-9a-zA-Z]*)') RE_DUAL_CIDR = re.compile(r'//(0|[1-9]\d*)$') RE_CIDR = re.compile(r'/(0|[1-9]\d*)$') PAT_IP4 = r'\.'.join([r'(?:\d|[1-9]\d|1\d\d|2[0-4]\d|25[0-5])']*4) RE_IP4 = re.compile(PAT_IP4+'$') RE_TOPLAB = re.compile( r'\.[0-9a-z]*[a-z][0-9a-z]*|[0-9a-z]+-[0-9a-z-]*[0-9a-z]$',re.IGNORECASE) RE_IP6 = re.compile( '(?:%(hex4)s:){6}%(ls32)s$' '|::(?:%(hex4)s:){5}%(ls32)s$' '|(?:%(hex4)s)?::(?:%(hex4)s:){4}%(ls32)s$' '|(?:(?:%(hex4)s:){0,1}%(hex4)s)?::(?:%(hex4)s:){3}%(ls32)s$' '|(?:(?:%(hex4)s:){0,2}%(hex4)s)?::(?:%(hex4)s:){2}%(ls32)s$' '|(?:(?:%(hex4)s:){0,3}%(hex4)s)?::%(hex4)s:%(ls32)s$' '|(?:(?:%(hex4)s:){0,4}%(hex4)s)?::%(ls32)s$' '|(?:(?:%(hex4)s:){0,5}%(hex4)s)?::%(hex4)s$' '|(?:(?:%(hex4)s:){0,6}%(hex4)s)?::$' % { 'ls32': r'(?:[0-9a-f]{1,4}:[0-9a-f]{1,4}|%s)'%PAT_IP4, 'hex4': r'[0-9a-f]{1,4}' }, re.IGNORECASE) # Local parts and senders have their delimiters replaced with '.' during # macro expansion # JOINERS = {'l': '.', 's': '.'} RESULTS = {'+': 'pass', '-': 'fail', '?': 'neutral', '~': 'softfail', 'pass': 'pass', 'fail': 'fail', 'permerror': 'permerror', 'error': 'error', 'neutral': 'neutral', 'softfail': 'softfail', 'none': 'none', 'local': 'local', 'trusted': 'trusted', 'ambiguous': 'ambiguous'} EXPLANATIONS = {'pass': 'sender SPF authorized', 'fail': 'SPF fail - not authorized', 'permerror': 'permanent error in processing', 'temperror': 'temporary DNS error in processing', 'softfail': 'domain owner discourages use of this host', 'neutral': 'access neither permitted nor denied', 'none': '', #Note: The following are not formally SPF results 'local': 'No SPF result due to local policy', 'trusted': 'No SPF check - trusted-forwarder.org', #Ambiguous only used in harsh mode for SPF validation 'ambiguous': 'No error, but results may vary' } #Default receiver policies - can be overridden. POLICY = {'tfwl': False, #Check trusted-forwarder.org 'skip_localhost': True, #Don't check SPF on local connections 'always_helo': False, #Only works if helo_first is also True. 'spf_helo_mustpass': True, #Treat HELO test returning softfail or #neutral as Fail - HELO should be a single IP per name. No reason to #accept SPF relaxed provisions for HELO. No affect if None. 'reject_helo_fail': False, 'spf_reject_fail': True, 'spf_reject_neutral': False, 'spf_accept_softfail': True, 'spf_best_guess': True, 'spf_strict': True, } # Recommended SMTP codes for certain SPF results. For results not in # this table the recommendation is to accept the message as authorized. # An SPF result is never enough to recommend that a message be accepted for # delivery. Additional checks are generally required. # The softfail result requires special processing. SMTP_CODES = { 'fail': [550,'5.7.1'], 'temperror': [451,'4.4.3'], 'permerror': [550,'5.5.2'], 'softfail': [451,'4.3.0'] } if not POLICY['spf_accept_softfail']: SMTP_CODES['softfail'] = (550,'5.7.1') if POLICY['spf_reject_neutral']: SMTP_CODES['neutral'] = (550,'5.7.1') # if set to a domain name, search _spf.domain namespace if no SPF record # found in source domain. DELEGATE = None # support pre 2.2.1.... try: bool, True, False = bool, True, False except NameError: False, True = 0, 1 def bool(x): return not not x # ...pre 2.2.1 # standard default SPF record for best_guess DEFAULT_SPF = 'v=spf1 a/24 mx/24 ptr' #Whitelisted forwarders here. Additional locally trusted forwarders can be #added to this record. TRUSTED_FORWARDERS = 'v=spf1 ?include:spf.trusted-forwarder.org -all' # maximum DNS lookups allowed MAX_LOOKUP = 10 #RFC 4408 Para 10.1 MAX_MX = 10 #RFC 4408 Para 10.1 MAX_PTR = 10 #RFC 4408 Para 10.1 MAX_CNAME = 10 # analogous interpretation to MAX_PTR MAX_RECURSION = 20 ALL_MECHANISMS = ('a', 'mx', 'ptr', 'exists', 'include', 'ip4', 'ip6', 'all') COMMON_MISTAKES = { 'prt': 'ptr', 'ip': 'ip4', 'ipv4': 'ip4', 'ipv6': 'ip6' } #If harsh processing, for the validator, is invoked, warn if results #likely deviate from the publishers intention. class AmbiguityWarning(Exception): "SPF Warning - ambiguous results" def __init__(self,msg,mech=None,ext=None): Exception.__init__(self,msg,mech) self.msg = msg self.mech = mech self.ext = ext def __str__(self): if self.mech: return '%s: %s'%(self.msg,self.mech) return self.msg class TempError(Exception): "Temporary SPF error" def __init__(self,msg,mech=None,ext=None): Exception.__init__(self,msg,mech) self.msg = msg self.mech = mech self.ext = ext def __str__(self): if self.mech: return '%s: %s'%(self.msg,self.mech) return self.msg class PermError(Exception): "Permanent SPF error" def __init__(self,msg,mech=None,ext=None): Exception.__init__(self,msg,mech) self.msg = msg self.mech = mech self.ext = ext def __str__(self): if self.mech: return '%s: %s'%(self.msg,self.mech) return self.msg def check(i, s, h,local=None,receiver=None): """Test an incoming MAIL FROM:, from a client with ip address i. h is the HELO/EHLO domain name. Returns (result, code, explanation) where result in ['pass', 'permerror', 'fail', 'temperror', 'softfail', 'none', 'neutral' ]. Example: #>>> check(i='61.51.192.42', s='liukebing@bcc.com', h='bmsi.com') """ return query(i=i, s=s, h=h,local=local,receiver=receiver).check() class query(object): """A query object keeps the relevant information about a single SPF query: i: ip address of SMTP client s: sender declared in MAIL FROM:<> l: local part of sender s d: current domain, initially domain part of sender s h: EHLO/HELO domain v: 'in-addr' for IPv4 clients and 'ip6' for IPv6 clients t: current timestamp p: SMTP client domain name o: domain part of sender s This is also, by design, the same variables used in SPF macro expansion. Also keeps cache: DNS cache. """ def __init__(self, i, s, h,local=None,receiver=None,strict=True): self.i, self.s, self.h = i, s, h if not s and h: self.s = 'postmaster@' + h self.l, self.o = split_email(s, h) self.t = str(int(time.time())) self.v = 'in-addr' self.d = self.o self.p = None if receiver: self.r = receiver else: self.r = 'unknown' # Since the cache does not track Time To Live, it is created # fresh for each query. It is important for efficiently using # multiple results provided in DNS answers. self.cache = {} self.defexps = dict(EXPLANATIONS) self.exps = dict(EXPLANATIONS) self.libspf_local = local # local policy self.lookups = 0 # strict can be False, True, or 2 (numeric) for harsh self.strict = strict def set_default_explanation(self,exp): exps = self.exps for i in 'softfail','fail','permerror': exps[i] = exp def getp(self): if not self.p: p = self.dns_ptr(self.i) if len(p) > 0: self.p = p[0] else: self.p = self.i return self.p def best_guess(self,spf=DEFAULT_SPF): """Return a best guess based on a default SPF record""" return self.check(spf) def check(self, spf=None): """ Returns (result, mta-status-code, explanation) where result in ['fail', 'softfail', 'neutral' 'permerror', 'pass', 'temperror', 'none'] Examples: >>> q = query(s='strong-bad@email.example.com', ... h='mx.example.org', i='192.0.2.3') >>> q.check(spf='v=spf1 ?all') ('neutral', 250, 'access neither permitted nor denied') >>> q.check(spf='v=spf1 ip4:192.0.0.0/8 ?all moo') ('permerror', 550, 'SPF Permanent Error: Unknown mechanism found: moo') >>> q.check(spf='v=spf1 =a ?all moo') ('permerror', 550, 'SPF Permanent Error: Unknown qualifier, RFC 4408 para 4.6.1, found in: =a') >>> q.check(spf='v=spf1 ip4:192.0.0.0/8 ~all') ('pass', 250, 'sender SPF authorized') >>> q.check(spf='v=spf1 ip4:192.0.0.0/8 -all moo=') ('pass', 250, 'sender SPF authorized') >>> q.check(spf='v=spf1 ip4:192.0.0.0/8 -all match.sub-domains_9=yes') ('pass', 250, 'sender SPF authorized') >>> q.strict = False >>> q.check(spf='v=spf1 ip4:192.0.0.0/8 -all moo') ('pass', 250, 'sender SPF authorized') >>> q.check(spf='v=spf1 ip4:192.1.0.0/16 moo -all') ('permerror', 550, 'SPF Permanent Error: Unknown mechanism found: moo') >>> q.check(spf='v=spf1 ip4:192.1.0.0/16 ~all') ('softfail', 250, 'domain owner discourages use of this host') >>> q.check(spf='v=spf1 -ip4:192.1.0.0/6 ~all') ('fail', 550, 'SPF fail - not authorized') # Assumes DNS available >>> q.check() ('none', 250, '') >>> q.check(spf='v=spf1 ip4:1.2.3.4 -a:example.net -all') ('fail', 550, 'SPF fail - not authorized') >>> q.libspf_local='ip4:192.0.2.3 a:example.org' >>> q.check(spf='v=spf1 ip4:1.2.3.4 -a:example.net -all') ('pass', 250, 'sender SPF authorized') """ self.mech = [] # unknown mechanisms # If not strict, certain PermErrors (mispelled # mechanisms, strict processing limits exceeded) # will continue processing. However, the exception # that strict processing would raise is saved here self.perm_error = None try: self.lookups = 0 if not spf: spf = self.dns_spf(self.d) if self.libspf_local and spf: spf = insert_libspf_local_policy( spf,self.libspf_local) return self.check1(spf, self.d, 0) except TempError,x: self.prob = x.msg if x.mech: self.mech.append(x.mech) return ('temperror',451, 'SPF Temporary Error: ' + str(x)) except PermError,x: if not self.perm_error: self.perm_error = x self.prob = x.msg if x.mech: self.mech.append(x.mech) # Pre-Lentczner draft treats this as an unknown result # and equivalent to no SPF record. return ('permerror', 550, 'SPF Permanent Error: ' + str(x)) def check1(self, spf, domain, recursion): # spf rfc: 3.7 Processing Limits # if recursion > MAX_RECURSION: # This should never happen in strict mode # because of the other limits we check, # so if it does, there is something wrong with # our code. It is not a PermError because there is not # necessarily anything wrong with the SPF record. if self.strict: raise AssertionError('Too many levels of recursion') # As an extended result, however, it should be # a PermError. raise PermError('Too many levels of recursion') try: try: tmp, self.d = self.d, domain return self.check0(spf,recursion) finally: self.d = tmp except AmbiguityWarning,x: self.prob = x.msg if x.mech: self.mech.append(x.mech) return ('ambiguous', 000, 'SPF Ambiguity Warning: %s' % x) def note_error(self,*msg): if self.strict: raise PermError(*msg) # if lax mode, note error and continue if not self.perm_error: try: raise PermError(*msg) except PermError, x: # FIXME: keep a list of errors for even friendlier # diagnostics. self.perm_error = x return self.perm_error def validate_mechanism(self,mech): """Parse and validate a mechanism. Returns mech,m,arg,cidrlength,result Examples: >>> q = query(s='strong-bad@email.example.com.', ... h='mx.example.org', i='192.0.2.3') >>> q.validate_mechanism('A') ('A', 'a', 'email.example.com', 32, 'pass') >>> q = query(s='strong-bad@email.example.com', ... h='mx.example.org', i='192.0.2.3') >>> q.validate_mechanism('A') ('A', 'a', 'email.example.com', 32, 'pass') >>> q.validate_mechanism('?mx:%{d}/27') ('?mx:%{d}/27', 'mx', 'email.example.com', 27, 'neutral') >>> try: q.validate_mechanism('ip4:1.2.3.4/247') ... except PermError,x: print x Invalid IP4 CIDR length: ip4:1.2.3.4/247 >>> try: q.validate_mechanism('a:example.com:8080') ... except PermError,x: print x Invalid domain found (use FQDN): example.com:8080 >>> try: q.validate_mechanism('ip4:1.2.3.444/24') ... except PermError,x: print x Invalid IP4 address: ip4:1.2.3.444/24 >>> try: q.validate_mechanism('-all:3030') ... except PermError,x: print x Invalid all mechanism format - only qualifier allowed with all: -all:3030 >>> q.validate_mechanism('-mx:%%%_/.Clara.de/27') ('-mx:%%%_/.Clara.de/27', 'mx', '% /.Clara.de', 27, 'fail') >>> q.validate_mechanism('~exists:%{i}.%{s1}.100/86400.rate.%{d}') ('~exists:%{i}.%{s1}.100/86400.rate.%{d}', 'exists', '192.0.2.3.com.100/86400.rate.email.example.com', 32, 'softfail') >>> q.validate_mechanism('a:mail.example.com.') ('a:mail.example.com.', 'a', 'mail.example.com', 32, 'pass') """ # a mechanism m, arg, cidrlength, cidr6length = parse_mechanism(mech, self.d) # map '?' '+' or '-' to 'neutral' 'pass' or 'fail' if m: result = RESULTS.get(m[0]) if result: # eat '?' '+' or '-' m = m[1:] else: # default pass result = 'pass' if m in COMMON_MISTAKES: self.note_error('Unknown mechanism found',mech) m = COMMON_MISTAKES[m] if m == 'a' and RE_IP4.match(arg): x = self.note_error( 'Use the ip4 mechanism for ip4 addresses',mech) m = 'ip4' # validate cidr and dual-cidr if m in ('a', 'mx', 'ptr'): if cidrlength is None: cidrlength = 32; elif cidrlength > 32: raise PermError('Invalid IP4 CIDR length',mech) if cidr6length is None: cidr6length = 128 elif cidr6length > 128: raise PermError('Invalid IP6 CIDR length',mech) elif m == 'ip4': if cidr6length is not None: raise PermError('Dual CIDR not allowed',mech) if cidrlength is None: cidrlength = 32; elif cidrlength > 32: raise PermError('Invalid IP4 CIDR length',mech) if not RE_IP4.match(arg): raise PermError('Invalid IP4 address',mech) elif m == 'ip6': if cidr6length is not None: raise PermError('Dual CIDR not allowed',mech) if cidrlength is None: cidrlength = 128 elif cidrlength > 128: raise PermError('Invalid IP6 CIDR length',mech) if not RE_IP6.match(arg): raise PermError('Invalid IP6 address',mech) else: if cidrlength is not None or cidr6length is not None: raise PermError('Dual CIDR not allowed',mech) cidrlength = 32 # validate domain-spec if m in ('a', 'mx', 'ptr', 'exists', 'include'): arg = self.expand(arg) # any trailing dot was removed by expand() if RE_TOPLAB.split(arg)[-1]: raise PermError('Invalid domain found (use FQDN)', arg) if m == 'include': if arg == self.d: if mech != 'include': raise PermError('include has trivial recursion',mech) raise PermError('include mechanism missing domain',mech) return mech,m,arg,cidrlength,result # validate 'all' mechanism per RFC 4408 ABNF if m == 'all' and mech.count(':'): # print '|'+ arg + '|', mech, self.d, self.note_error( 'Invalid all mechanism format - only qualifier allowed with all' ,mech) if m in ALL_MECHANISMS: return mech,m,arg,cidrlength,result if m[1:] in ALL_MECHANISMS: x = self.note_error( 'Unknown qualifier, RFC 4408 para 4.6.1, found in',mech) else: x = self.note_error('Unknown mechanism found',mech) return mech,m,arg,cidrlength,x def check0(self, spf,recursion): """Test this query information against SPF text. Returns (result, mta-status-code, explanation) where result in ['fail', 'unknown', 'pass', 'none'] """ if not spf: return ('none', 250, EXPLANATIONS['none']) # split string by whitespace, drop the 'v=spf1' spf = spf.split() # Catch case where SPF record has no spaces. # Can never happen with conforming dns_spf(), however # in the future we might want to give permerror # for common mistakes like IN TXT "v=spf1" "mx" "-all" # in relaxed mode. if spf[0] != 'v=spf1': raise PermError('Invalid SPF record in', self.d) spf = spf[1:] # copy of explanations to be modified by exp= exps = self.exps redirect = None # no mechanisms at all cause unknown result, unless # overridden with 'default=' modifier # default = 'neutral' mechs = [] # Look for modifiers # for mech in spf: m = RE_MODIFIER.split(mech)[1:] if len(m) != 2: mechs.append(self.validate_mechanism(mech)) continue if m[0] == 'exp': try: self.set_default_explanation(self.get_explanation(m[1])) except PermError: pass elif m[0] == 'redirect': self.check_lookups() redirect = self.expand(m[1]) elif m[0] == 'default': # default=- is the same as default=fail default = RESULTS.get(m[1], default) # spf rfc: 3.6 Unrecognized Mechanisms and Modifiers # Evaluate mechanisms # for mech,m,arg,cidrlength,result in mechs: if m == 'include': self.check_lookups() res,code,txt = self.check1(self.dns_spf(arg), arg, recursion + 1) if res == 'pass': break if res == 'none': self.note_error( 'No valid SPF record for included domain: %s'%arg, mech) res = 'neutral' continue elif m == 'all': break elif m == 'exists': self.check_lookups() try: if len(self.dns_a(arg)) > 0: break except AmbiguityWarning: # Exists wants no response sometimes so don't raise # the warning. pass elif m == 'a': self.check_lookups() if cidrmatch(self.i, self.dns_a(arg), cidrlength): break elif m == 'mx': self.check_lookups() if cidrmatch(self.i, self.dns_mx(arg), cidrlength): break elif m == 'ip4': if arg == self.d: raise PermError('Missing IP4 arg',mech) try: if cidrmatch(self.i, [arg], cidrlength): break except socket.error: raise PermError('syntax error',mech) elif m == 'ip6': if arg == self.d: raise PermError('Missing IP6 arg',mech) # Until we support IPV6, we should never # get an IPv6 connection. So this mech # will never match. pass elif m == 'ptr': self.check_lookups() if domainmatch(self.validated_ptrs(self.i), arg): break else: raise result else: # no matches if redirect: #Catch redirect to a non-existant SPF record. redirect_record = self.dns_spf(redirect) if not redirect_record: raise PermError('redirect domain has no SPF record', redirect) return self.check1(redirect_record, redirect, recursion + 1) else: result = default if result == 'fail': return (result, 550, exps[result]) else: return (result, 250, exps[result]) def check_lookups(self): self.lookups = self.lookups + 1 if self.lookups > MAX_LOOKUP*4: raise PermError('More than %d DNS lookups'%MAX_LOOKUP*4) if self.lookups > MAX_LOOKUP: self.note_error('Too many DNS lookups') def get_explanation(self, spec): """Expand an explanation.""" if spec: txt = ''.join(self.dns_txt(self.expand(spec))) return self.expand(txt,stripdot=False) else: return 'explanation : Required option is missing' def expand(self, str, stripdot=True): # macros='slodipvh' """Do SPF RFC macro expansion. Examples: >>> q = query(s='strong-bad@email.example.com', ... h='mx.example.org', i='192.0.2.3') >>> q.p = 'mx.example.org' >>> q.expand('%{d}') 'email.example.com' >>> q.expand('%{d4}') 'email.example.com' >>> q.expand('%{d3}') 'email.example.com' >>> q.expand('%{d2}') 'example.com' >>> q.expand('%{d1}') 'com' >>> q.expand('%{p}') 'mx.example.org' >>> q.expand('%{p2}') 'example.org' >>> q.expand('%{dr}') 'com.example.email' >>> q.expand('%{d2r}') 'example.email' >>> q.expand('%{l}') 'strong-bad' >>> q.expand('%{l-}') 'strong.bad' >>> q.expand('%{lr}') 'strong-bad' >>> q.expand('%{lr-}') 'bad.strong' >>> q.expand('%{l1r-}') 'strong' >>> q.expand('%{ir}.%{v}._spf.%{d2}') '3.2.0.192.in-addr._spf.example.com' >>> q.expand('%{lr-}.lp._spf.%{d2}') 'bad.strong.lp._spf.example.com' >>> q.expand('%{lr-}.lp.%{ir}.%{v}._spf.%{d2}') 'bad.strong.lp.3.2.0.192.in-addr._spf.example.com' >>> q.expand('%{ir}.%{v}.%{l1r-}.lp._spf.%{d2}') '3.2.0.192.in-addr.strong.lp._spf.example.com' >>> q.expand('%{p2}.trusted-domains.example.net') 'example.org.trusted-domains.example.net' >>> q.expand('%{p2}.trusted-domains.example.net.') 'example.org.trusted-domains.example.net' """ end = 0 result = '' for i in RE_CHAR.finditer(str): result += str[end:i.start()] macro = str[i.start():i.end()] if macro == '%%': result += '%' elif macro == '%_': result += ' ' elif macro == '%-': result += '%20' else: letter = macro[2].lower() if letter == 'p': self.getp() expansion = getattr(self, letter, 'Macro Error') if expansion: if expansion == 'Macro Error': raise PermError('Unknown Macro Encountered') result += expand_one(expansion, macro[3:-1], JOINERS.get(letter)) end = i.end() result += str[end:] if stripdot and result.endswith('.'): return result[:-1] return result def dns_spf(self, domain): """Get the SPF record recorded in DNS for a specific domain name. Returns None if not found, or if more than one record is found. """ # for performance, check for most common case of TXT first a = [t for t in self.dns_txt(domain) if isSPF(t)] if len(a) > 1: raise PermError('Two or more type TXT spf records found.') if len(a) == 1 and self.strict < 2: return a[0] # check official SPF type first when it becomes more popular try: b = [t for t in self.dns_99(domain) if isSPF(t)] except TempError,x: # some braindead DNS servers hang on type 99 query if self.strict > 1: raise x b = [] if len(b) > 1: raise PermError('Two or more type SPF spf records found.') if len(b) == 1: if self.strict > 1 and len(a) == 1 and a[0] != b[0]: #Changed from permerror to warning based on RFC 4408 Auth 48 change raise AmbiguityWarning( 'v=spf1 records of both type TXT and SPF (type 99) present, but not identical') return b[0] if len(a) == 1: return a[0] # return TXT if SPF wasn't found if DELEGATE: # use local record if neither found a = [t for t in self.dns_txt(domain+'._spf.'+DELEGATE) if isSPF(t) ] if len(a) == 1: return a[0] return None def dns_txt(self, domainname): "Get a list of TXT records for a domain name." if domainname: return [''.join(a) for a in self.dns(domainname, 'TXT')] return [] def dns_99(self, domainname): "Get a list of type SPF=99 records for a domain name." if domainname: return [''.join(a) for a in self.dns(domainname, 'SPF')] return [] def dns_mx(self, domainname): """Get a list of IP addresses for all MX exchanges for a domain name. """ # RFC 4408 section 5.4 "mx" # To prevent DoS attacks, more than 10 MX names MUST NOT be looked up mxnames = self.dns(domainname, 'MX') if len(mxnames) > MAX_MX: self.note_error('More than %d MX records returned'%MAX_MX) if self.strict: max = MAX_MX if self.strict > 1 and len(mxnames) == 0: raise AmbiguityWarning( 'No MX records found for mx mechanism', domainname) else: max = MAX_MX * 4 return [a for mx in mxnames[:max] for a in self.dns_a(mx[1])] def dns_a(self, domainname): """Get a list of IP addresses for a domainname.""" if not domainname: return [] if self.strict > 1: alist = self.dns(domainname, 'A') if len(alist) == 0: raise AmbiguityWarning('No A records found for', domainname) else: return alist return self.dns(domainname, 'A') def dns_aaaa(self, domainname): """Get a list of IPv6 addresses for a domainname.""" return self.dns(domainname, 'AAAA') def validated_ptrs(self, i): """Figure out the validated PTR domain names for a given IP address. """ # To prevent DoS attacks, more than 10 PTR names MUST NOT be looked up if self.strict: max = MAX_PTR if self.strict > 1: #Break out the number of PTR records returned for testing try: ptrnames = self.dns_ptr(i) ptrip = [p for p in ptrnames if i in self.dns_a(p)] if len(ptrnames) > max: warning = 'More than ' + str(max) + ' PTR records returned' raise AmbiguityWarning(warning, i) else: if len(ptrnames) == 0: raise AmbiguityWarning('No PTR records found for ptr mechanism', ptrnames) return ptrip except: raise AmbiguityWarning('No PTR records found for ptr mechanism', ptrnames) else: max = MAX_PTR * 4 return [p for p in self.dns_ptr(i)[:max] if i in self.dns_a(p)] def dns_ptr(self, i): """Get a list of domain names for an IP address.""" return self.dns(reverse_dots(i) + ".in-addr.arpa", 'PTR') def dns(self, name, qtype, cnames=None): """DNS query. If the result is in cache, return that. Otherwise pull the result from DNS, and cache ALL answers, so additional info is available for further queries later. CNAMEs are followed. If there is no data, [] is returned. pre: qtype in ['A', 'AAAA', 'MX', 'PTR', 'TXT', 'SPF'] post: isinstance(__return__, types.ListType) """ result = self.cache.get( (name, qtype) ) cname = None if not result: for k,v in DNSLookup(name,qtype): if k == (name, 'CNAME'): cname = v self.cache.setdefault(k, []).append(v) result = self.cache.get( (name, qtype), []) if not result and cname: if not cnames: cnames = {} elif len(cnames) >= MAX_CNAME: #return result # if too many == NX_DOMAIN raise PermError( 'Length of CNAME chain exceeds %d' % MAX_CNAME) cnames[name] = cname if cname in cnames: raise PermError,'CNAME loop' result = self.dns(cname, qtype, cnames=cnames) return result def get_header(self,res,receiver=None): if not receiver: receiver = self.r if res in ('pass','fail','softfail'): return '%s (%s: %s) client-ip=%s; envelope-from=%s; helo=%s;' % ( res,receiver,self.get_header_comment(res),self.i, self.l + '@' + self.o, self.h) if res == 'permerror': return '%s (%s: %s)' % (' '.join([res] + self.mech), receiver,self.get_header_comment(res)) return '%s (%s: %s)' % (res,receiver,self.get_header_comment(res)) def get_header_comment(self,res): """Return comment for Received-SPF header. """ sender = self.o if res == 'pass': return \ "domain of %s designates %s as permitted sender" \ % (sender,self.i) elif res == 'softfail': return \ "transitioning domain of %s does not designate %s as permitted sender" \ % (sender,self.i) elif res == 'neutral': return \ "%s is neither permitted nor denied by domain of %s" \ % (self.i,sender) elif res == 'none': return \ "%s is neither permitted nor denied by domain of %s" \ % (self.i,sender) #"%s does not designate permitted sender hosts" % sender elif res == 'permerror': return \ "permanent error in processing domain of %s: %s" \ % (sender, self.prob) elif res == 'error': return \ "temporary error in processing during lookup of %s" % sender elif res == 'fail': return \ "domain of %s does not designate %s as permitted sender" \ % (sender,self.i) raise ValueError("invalid SPF result for header comment: "+res) def split_email(s, h): """Given a sender email s and a HELO domain h, create a valid tuple (l, d) local-part and domain-part. Examples: >>> split_email('', 'wayforward.net') ('postmaster', 'wayforward.net') >>> split_email('foo.com', 'wayforward.net') ('postmaster', 'foo.com') >>> split_email('terry@wayforward.net', 'optsw.com') ('terry', 'wayforward.net') """ if not s: return 'postmaster', h else: parts = s.split('@', 1) if len(parts) == 2: return tuple(parts) else: return 'postmaster', s def parse_mechanism(str, d): """Breaks A, MX, IP4, and PTR mechanisms into a (name, domain, cidr,cidr6) tuple. The domain portion defaults to d if not present, the cidr defaults to 32 if not present. Examples: >>> parse_mechanism('a', 'foo.com') ('a', 'foo.com', None, None) >>> parse_mechanism('a:bar.com', 'foo.com') ('a', 'bar.com', None, None) >>> parse_mechanism('a/24', 'foo.com') ('a', 'foo.com', 24, None) >>> parse_mechanism('A:foo:bar.com/16', 'foo.com') ('a', 'foo:bar.com', 16, None) >>> parse_mechanism('-exists:%{i}.%{s1}.100/86400.rate.%{d}','foo.com') ('-exists', '%{i}.%{s1}.100/86400.rate.%{d}', None, None) >>> parse_mechanism('mx:%%%_/.Claranet.de/27','foo.com') ('mx', '%%%_/.Claranet.de', 27, None) >>> parse_mechanism('mx:%{d}/27','foo.com') ('mx', '%{d}', 27, None) >>> parse_mechanism('iP4:192.0.0.0/8','foo.com') ('ip4', '192.0.0.0', 8, None) """ a = RE_DUAL_CIDR.split(str) if len(a) == 3: str, cidr6 = a[0], int(a[1]) else: cidr6 = None a = RE_CIDR.split(str) if len(a) == 3: str, cidr = a[0], int(a[1]) else: cidr = None a = str.split(':',1) if len(a) < 2: return str.lower(), d, cidr, cidr6 return a[0].lower(), a[1], cidr, cidr6 def reverse_dots(name): """Reverse dotted IP addresses or domain names. Example: >>> reverse_dots('192.168.0.145') '145.0.168.192' >>> reverse_dots('email.example.com') 'com.example.email' """ a = name.split('.') a.reverse() return '.'.join(a) def domainmatch(ptrs, domainsuffix): """grep for a given domain suffix against a list of validated PTR domain names. Examples: >>> domainmatch(['FOO.COM'], 'foo.com') 1 >>> domainmatch(['moo.foo.com'], 'FOO.COM') 1 >>> domainmatch(['moo.bar.com'], 'foo.com') 0 """ domainsuffix = domainsuffix.lower() for ptr in ptrs: ptr = ptr.lower() if ptr == domainsuffix or ptr.endswith('.' + domainsuffix): return True return False def cidrmatch(i, ipaddrs, cidr_length = 32): """Match an IP address against a list of other IP addresses. Examples: >>> cidrmatch('192.168.0.45', ['192.168.0.44', '192.168.0.45']) 1 >>> cidrmatch('192.168.0.43', ['192.168.0.44', '192.168.0.45']) 0 >>> cidrmatch('192.168.0.43', ['192.168.0.44', '192.168.0.45'], 24) 1 """ try: c = cidr(i, cidr_length) for ip in ipaddrs: if cidr(ip, cidr_length) == c: return True except socket.error: pass return False def cidr(i, n): """Convert an IP address string with a CIDR mask into a 32-bit or 128-bit integer. i must be a string of numbers 0..255 separated by dots '.':: pre: forall([0 <= int(p) < 256 for p in i.split('.')]) n is a number of bits to mask:: pre: 0 <= n <= 32 Examples: >>> bin2addr(cidr('192.168.5.45', 32)) '192.168.5.45' >>> bin2addr(cidr('192.168.5.45', 24)) '192.168.5.0' >>> bin2addr(cidr('192.168.0.45', 8)) '192.0.0.0' """ return ~(MASK >> n) & MASK & addr2bin(i) def addr2bin(str): """Convert a string IPv4 address into an unsigned integer. Examples:: >>> addr2bin('127.0.0.1') 2130706433L >>> addr2bin('127.0.0.1') == socket.INADDR_LOOPBACK 1 >>> addr2bin('255.255.255.254') 4294967294L >>> addr2bin('192.168.0.1') 3232235521L Unlike DNS.addr2bin, the n, n.n, and n.n.n forms for IP addresses are handled as well:: >>> addr2bin('10.65536') 167837696L >>> 10 * (2 ** 24) + 65536 167837696 >>> addr2bin('10.93.512') 173867520L >>> 10 * (2 ** 24) + 93 * (2 ** 16) + 512 173867520 """ try: return struct.unpack("!L", socket.inet_aton(str))[0] except socket.error: if not socket.has_ipv6: raise h,l = struct.unpack("!QQ", socket.inet_pton(socket.AF_INET6,str)) return h << 64 | l; def bin2addr(addr): """Convert a numeric IPv4 address into string n.n.n.n form. Examples:: >>> bin2addr(socket.INADDR_LOOPBACK) '127.0.0.1' >>> bin2addr(socket.INADDR_ANY) '0.0.0.0' >>> bin2addr(socket.INADDR_NONE) '255.255.255.255' """ return socket.inet_ntoa(struct.pack("!L", addr)) def expand_one(expansion, str, joiner): if not str: return expansion ln, reverse, delimiters = RE_ARGS.split(str)[1:4] if not delimiters: delimiters = '.' expansion = split(expansion, delimiters, joiner) if reverse: expansion.reverse() if ln: expansion = expansion[-int(ln)*2+1:] return ''.join(expansion) def split(str, delimiters, joiner=None): """Split a string into pieces by a set of delimiter characters. The resulting list is delimited by joiner, or the original delimiter if joiner is not specified. Examples: >>> split('192.168.0.45', '.') ['192', '.', '168', '.', '0', '.', '45'] >>> split('terry@wayforward.net', '@.') ['terry', '@', 'wayforward', '.', 'net'] >>> split('terry@wayforward.net', '@.', '.') ['terry', '.', 'wayforward', '.', 'net'] """ result, element = [], '' for c in str: if c in delimiters: result.append(element) element = '' if joiner: result.append(joiner) else: result.append(c) else: element += c result.append(element) return result def insert_libspf_local_policy(spftxt,local=None): """Returns spftxt with local inserted just before last non-fail mechanism. This is how the libspf{2} libraries handle "local-policy". Examples: >>> insert_libspf_local_policy('v=spf1 -all') 'v=spf1 -all' >>> insert_libspf_local_policy('v=spf1 -all','mx') 'v=spf1 -all' >>> insert_libspf_local_policy('v=spf1','a mx ptr') 'v=spf1 a mx ptr' >>> insert_libspf_local_policy('v=spf1 mx -all','a ptr') 'v=spf1 mx a ptr -all' >>> insert_libspf_local_policy('v=spf1 mx -include:foo.co +all','a ptr') 'v=spf1 mx a ptr -include:foo.co +all' # FIXME: is this right? If so, "last non-fail" is a bogus description. >>> insert_libspf_local_policy('v=spf1 mx ?include:foo.co +all','a ptr') 'v=spf1 mx a ptr ?include:foo.co +all' >>> spf='v=spf1 ip4:1.2.3.4 -a:example.net -all' >>> local='ip4:192.0.2.3 a:example.org' >>> insert_libspf_local_policy(spf,local) 'v=spf1 ip4:1.2.3.4 ip4:192.0.2.3 a:example.org -a:example.net -all' """ # look to find the all (if any) and then put local # just after last non-fail mechanism. This is how # libspf2 handles "local policy", and some people # apparently find it useful (don't ask me why). if not local: return spftxt spf = spftxt.split()[1:] if spf: # local policy is SPF mechanisms/modifiers with no # 'v=spf1' at the start spf.reverse() #find the last non-fail mechanism for mech in spf: # map '?' '+' or '-' to 'neutral' 'pass' # or 'fail' if not RESULTS.get(mech[0]): # actually finds last mech with default result where = spf.index(mech) spf[where:where] = [local] spf.reverse() local = ' '.join(spf) break else: return spftxt # No local policy adds for v=spf1 -all # Processing limits not applied to local policy. Suggest # inserting 'local' mechanism to handle this properly #MAX_LOOKUP = 100 return 'v=spf1 '+local def _test(): import doctest, spf return doctest.testmod(spf) DNS.DiscoverNameServers() # Fails on Mac OS X? Add domain to /etc/resolv.conf if __name__ == '__main__': import sys if len(sys.argv) == 1: print USAGE _test() elif len(sys.argv) == 2: q = query(i='127.0.0.1', s='localhost', h='unknown', receiver=socket.gethostname()) print q.dns_spf(sys.argv[1]) elif len(sys.argv) == 4: print check(i=sys.argv[1], s=sys.argv[2], h=sys.argv[3], receiver=socket.gethostname()) elif len(sys.argv) == 5: i, s, h = sys.argv[2:] q = query(i=i, s=s, h=h, receiver=socket.gethostname(), strict=False) print q.check(sys.argv[1]) if q.perm_error and q.perm_error.ext: print q.perm_error.ext else: print USAGE