Source Code for Module dkim.util

 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) 2011 William Grant <me@williamgrant.id.au> 
18   
19  import re 
20   
21  import logging 
22  try: 
23      from logging import NullHandler 
24  except ImportError: 
25 -    class NullHandler(logging.Handler): 
26 -        def emit(self, record): 
27              pass 
28   
29   
30  __all__ = [ 
31      'DuplicateTag', 
32      'get_default_logger', 
33      'InvalidTagSpec', 
34      'InvalidTagValueList', 
35      'parse_tag_value', 
36      ] 
37   
38   
39 -class InvalidTagValueList(Exception): 
40      pass 
41   
42   
43 -class DuplicateTag(InvalidTagValueList): 
44      pass 
45   
46   
47 -class InvalidTagSpec(InvalidTagValueList): 
48      pass 
49   
50   
51 -def parse_tag_value(tag_list): 
52      """Parse a DKIM Tag=Value list. 
53   
54      Interprets the syntax specified by RFC6376 section 3.2. 
55      Assumes that folding whitespace is already unfolded. 
56   
57      @param tag_list: A bytes string containing a DKIM Tag=Value list. 
58      """ 
59      tags = {} 
60      tag_specs = tag_list.strip().split(b';') 
61      # Trailing semicolons are valid. 
62      if not tag_specs[-1]: 
63          tag_specs.pop() 
64      for tag_spec in tag_specs: 
65          try: 
66              key, value = [x.strip() for x in tag_spec.split(b'=', 1)] 
67          except ValueError: 
68              raise InvalidTagSpec(tag_spec) 
69          if re.match(br'^[a-zA-Z](\w)*', key) is None: 
70              raise InvalidTagSpec(tag_spec) 
71          if key in tags: 
72              raise DuplicateTag(key) 
73          tags[key] = value 
74      return tags 
75   
76   
77 -def get_default_logger(): 
78      """Get the default dkimpy logger.""" 
79      logger = logging.getLogger('dkimpy') 
80      if not logger.handlers: 
81          logger.addHandler(NullHandler()) 
82      return logger 
83