Gene Shuman
83 lines
2.3 KiB
Python
83 lines
2.3 KiB
Python
# This software is provided 'as-is', without any express or implied
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# warranty. In no event will the author be held liable for any damages
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# arising from the use of this software.
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#
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# Permission is granted to anyone to use this software for any purpose,
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# including commercial applications, and to alter it and redistribute it
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# freely, subject to the following restrictions:
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#
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# 1. The origin of this software must not be misrepresented; you must not
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# claim that you wrote the original software. If you use this software
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# in a product, an acknowledgment in the product documentation would be
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# appreciated but is not required.
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# 2. Altered source versions must be plainly marked as such, and must not be
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# misrepresented as being the original software.
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# 3. This notice may not be removed or altered from any source distribution.
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#
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# Copyright (c) 2011 William Grant <me@williamgrant.id.au>
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import re
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import logging
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try:
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from logging import NullHandler
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except ImportError:
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class NullHandler(logging.Handler):
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def emit(self, record):
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pass
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__all__ = [
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'DuplicateTag',
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'get_default_logger',
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'InvalidTagSpec',
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'InvalidTagValueList',
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'parse_tag_value',
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]
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class InvalidTagValueList(Exception):
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pass
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class DuplicateTag(InvalidTagValueList):
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pass
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class InvalidTagSpec(InvalidTagValueList):
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pass
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def parse_tag_value(tag_list):
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"""Parse a DKIM Tag=Value list.
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Interprets the syntax specified by RFC4871 section 3.2.
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Assumes that folding whitespace is already unfolded.
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@param tag_list: A bytes string containing a DKIM Tag=Value list.
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"""
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tags = {}
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tag_specs = tag_list.strip().split(b';')
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# Trailing semicolons are valid.
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if not tag_specs[-1]:
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tag_specs.pop()
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for tag_spec in tag_specs:
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try:
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key, value = [x.strip() for x in tag_spec.split(b'=', 1)]
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except ValueError:
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raise InvalidTagSpec(tag_spec)
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if re.match(br'^[a-zA-Z](\w)*', key) is None:
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raise InvalidTagSpec(tag_spec)
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if key in tags:
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raise DuplicateTag(key)
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tags[key] = value
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return tags
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def get_default_logger():
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"""Get the default dkimpy logger."""
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logger = logging.getLogger('dkimpy')
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if not logger.handlers:
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logger.addHandler(NullHandler())
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return logger
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