Source Code for Module dkim.dnsplug

 1  # This software is provided 'as-is', without any express or implied 
 2  # warranty.  In no event will the author be held liable for any damages 
 3  # arising from the use of this software. 
 4  # 
 5  # Permission is granted to anyone to use this software for any purpose, 
 6  # including commercial applications, and to alter it and redistribute it 
 7  # freely, subject to the following restrictions: 
 8  # 
 9  # 1. The origin of this software must not be misrepresented; you must not 
10  #    claim that you wrote the original software. If you use this software 
11  #    in a product, an acknowledgment in the product documentation would be 
12  #    appreciated but is not required. 
13  # 2. Altered source versions must be plainly marked as such, and must not be 
14  #    misrepresented as being the original software. 
15  # 3. This notice may not be removed or altered from any source distribution. 
16  # 
17  # Copyright (c) 2008 Greg Hewgill http://hewgill.com 
18  # 
19  # This has been modified from the original software. 
20  # Copyright (c) 2011 William Grant <me@williamgrant.id.au> 
21   
22   
23  __all__ = [ 
24      'get_txt' 
25      ] 
26   
27   
28 -def get_txt_dnspython(name): 
29      """Return a TXT record associated with a DNS name.""" 
30      try: 
31        a = dns.resolver.query(name, dns.rdatatype.TXT,raise_on_no_answer=False) 
32        for r in a.response.answer: 
33            if r.rdtype == dns.rdatatype.TXT: 
34                return b"".join(r.items[0].strings) 
35      except dns.resolver.NXDOMAIN: pass 
36      return None 
37   
38   
39 -def get_txt_pydns(name): 
40      """Return a TXT record associated with a DNS name.""" 
41      # Older pydns releases don't like a trailing dot. 
42      if name.endswith('.'): 
43          name = name[:-1] 
44      response = DNS.DnsRequest(name, qtype='txt').req() 
45      if not response.answers: 
46          return None 
47      return b''.join(response.answers[0]['data']) 
48   
49 -def get_txt_Milter_dns(name): 
50      """Return a TXT record associated with a DNS name.""" 
51      # Older pydns releases don't like a trailing dot. 
52      if name.endswith('.'): 
53          name = name[:-1] 
54      sess = Session() 
55      a = sess.dns(name,'TXT') 
56      if a: return b''.join(a[0]) 
57      return None 
58   
59  # Prefer dnspython if it's there, otherwise use pydns. 
60  try: 
61      import dns.resolver 
62      _get_txt = get_txt_dnspython 
63  except ImportError: 
64      try: 
65          from Milter.dns import Session 
66          _get_txt = get_txt_Milter_dns 
67      except ImportError: 
68          import DNS 
69          DNS.DiscoverNameServers() 
70          _get_txt = get_txt_pydns 
71   
72 -def get_txt(name): 
73      """Return a TXT record associated with a DNS name. 
74   
75      @param name: The bytestring domain name to look up. 
76      """ 
77      # pydns needs Unicode, but DKIM's d= is ASCII (already punycoded). 
78      try: 
79          unicode_name = name.decode('ascii') 
80      except UnicodeDecodeError: 
81          return None 
82      txt = _get_txt(unicode_name) 
83      if type(txt) is str: 
84        txt = txt.encode('utf-8') 
85      return txt 
86