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224ef3ec3b
This could use more edge case tests, but the basic functionality is tested. (Note that this changeset does not add tailored support for the RFC 6532 message/global MIME type, but the email package generic facilities will handle it.) Reviewed by Maciej Szulik.
214 lines
9.7 KiB
Python
214 lines
9.7 KiB
Python
"""This will be the home for the policy that hooks in the new
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code that adds all the email6 features.
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"""
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from email._policybase import Policy, Compat32, compat32, _extend_docstrings
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from email.utils import _has_surrogates
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from email.headerregistry import HeaderRegistry as HeaderRegistry
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from email.contentmanager import raw_data_manager
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__all__ = [
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'Compat32',
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'compat32',
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'Policy',
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'EmailPolicy',
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'default',
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'strict',
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'SMTP',
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'HTTP',
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]
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@_extend_docstrings
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class EmailPolicy(Policy):
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"""+
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PROVISIONAL
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The API extensions enabled by this policy are currently provisional.
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Refer to the documentation for details.
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This policy adds new header parsing and folding algorithms. Instead of
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simple strings, headers are custom objects with custom attributes
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depending on the type of the field. The folding algorithm fully
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implements RFCs 2047 and 5322.
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In addition to the settable attributes listed above that apply to
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all Policies, this policy adds the following additional attributes:
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utf8 -- if False (the default) message headers will be
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serialized as ASCII, using encoded words to encode
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any non-ASCII characters in the source strings. If
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True, the message headers will be serialized using
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utf8 and will not contain encoded words (see RFC
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6532 for more on this serialization format).
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refold_source -- if the value for a header in the Message object
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came from the parsing of some source, this attribute
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indicates whether or not a generator should refold
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that value when transforming the message back into
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stream form. The possible values are:
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none -- all source values use original folding
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long -- source values that have any line that is
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longer than max_line_length will be
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refolded
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all -- all values are refolded.
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The default is 'long'.
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header_factory -- a callable that takes two arguments, 'name' and
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'value', where 'name' is a header field name and
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'value' is an unfolded header field value, and
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returns a string-like object that represents that
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header. A default header_factory is provided that
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understands some of the RFC5322 header field types.
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(Currently address fields and date fields have
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special treatment, while all other fields are
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treated as unstructured. This list will be
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completed before the extension is marked stable.)
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content_manager -- an object with at least two methods: get_content
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and set_content. When the get_content or
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set_content method of a Message object is called,
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it calls the corresponding method of this object,
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passing it the message object as its first argument,
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and any arguments or keywords that were passed to
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it as additional arguments. The default
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content_manager is
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:data:`~email.contentmanager.raw_data_manager`.
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"""
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utf8 = False
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refold_source = 'long'
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header_factory = HeaderRegistry()
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content_manager = raw_data_manager
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def __init__(self, **kw):
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# Ensure that each new instance gets a unique header factory
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# (as opposed to clones, which share the factory).
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if 'header_factory' not in kw:
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object.__setattr__(self, 'header_factory', HeaderRegistry())
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super().__init__(**kw)
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def header_max_count(self, name):
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"""+
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The implementation for this class returns the max_count attribute from
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the specialized header class that would be used to construct a header
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of type 'name'.
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"""
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return self.header_factory[name].max_count
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# The logic of the next three methods is chosen such that it is possible to
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# switch a Message object between a Compat32 policy and a policy derived
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# from this class and have the results stay consistent. This allows a
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# Message object constructed with this policy to be passed to a library
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# that only handles Compat32 objects, or to receive such an object and
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# convert it to use the newer style by just changing its policy. It is
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# also chosen because it postpones the relatively expensive full rfc5322
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# parse until as late as possible when parsing from source, since in many
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# applications only a few headers will actually be inspected.
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def header_source_parse(self, sourcelines):
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"""+
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The name is parsed as everything up to the ':' and returned unmodified.
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The value is determined by stripping leading whitespace off the
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remainder of the first line, joining all subsequent lines together, and
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stripping any trailing carriage return or linefeed characters. (This
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is the same as Compat32).
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"""
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name, value = sourcelines[0].split(':', 1)
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value = value.lstrip(' \t') + ''.join(sourcelines[1:])
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return (name, value.rstrip('\r\n'))
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def header_store_parse(self, name, value):
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"""+
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The name is returned unchanged. If the input value has a 'name'
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attribute and it matches the name ignoring case, the value is returned
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unchanged. Otherwise the name and value are passed to header_factory
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method, and the resulting custom header object is returned as the
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value. In this case a ValueError is raised if the input value contains
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CR or LF characters.
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"""
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if hasattr(value, 'name') and value.name.lower() == name.lower():
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return (name, value)
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if isinstance(value, str) and len(value.splitlines())>1:
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raise ValueError("Header values may not contain linefeed "
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"or carriage return characters")
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return (name, self.header_factory(name, value))
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def header_fetch_parse(self, name, value):
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"""+
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If the value has a 'name' attribute, it is returned to unmodified.
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Otherwise the name and the value with any linesep characters removed
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are passed to the header_factory method, and the resulting custom
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header object is returned. Any surrogateescaped bytes get turned
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into the unicode unknown-character glyph.
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"""
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if hasattr(value, 'name'):
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return value
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return self.header_factory(name, ''.join(value.splitlines()))
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def fold(self, name, value):
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"""+
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Header folding is controlled by the refold_source policy setting. A
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value is considered to be a 'source value' if and only if it does not
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have a 'name' attribute (having a 'name' attribute means it is a header
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object of some sort). If a source value needs to be refolded according
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to the policy, it is converted into a custom header object by passing
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the name and the value with any linesep characters removed to the
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header_factory method. Folding of a custom header object is done by
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calling its fold method with the current policy.
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Source values are split into lines using splitlines. If the value is
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not to be refolded, the lines are rejoined using the linesep from the
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policy and returned. The exception is lines containing non-ascii
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binary data. In that case the value is refolded regardless of the
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refold_source setting, which causes the binary data to be CTE encoded
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using the unknown-8bit charset.
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"""
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return self._fold(name, value, refold_binary=True)
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def fold_binary(self, name, value):
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"""+
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The same as fold if cte_type is 7bit, except that the returned value is
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bytes.
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If cte_type is 8bit, non-ASCII binary data is converted back into
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bytes. Headers with binary data are not refolded, regardless of the
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refold_header setting, since there is no way to know whether the binary
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data consists of single byte characters or multibyte characters.
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If utf8 is true, headers are encoded to utf8, otherwise to ascii with
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non-ASCII unicode rendered as encoded words.
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"""
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folded = self._fold(name, value, refold_binary=self.cte_type=='7bit')
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charset = 'utf8' if self.utf8 else 'ascii'
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return folded.encode(charset, 'surrogateescape')
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def _fold(self, name, value, refold_binary=False):
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if hasattr(value, 'name'):
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return value.fold(policy=self)
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maxlen = self.max_line_length if self.max_line_length else float('inf')
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lines = value.splitlines()
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refold = (self.refold_source == 'all' or
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self.refold_source == 'long' and
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(lines and len(lines[0])+len(name)+2 > maxlen or
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any(len(x) > maxlen for x in lines[1:])))
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if refold or refold_binary and _has_surrogates(value):
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return self.header_factory(name, ''.join(lines)).fold(policy=self)
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return name + ': ' + self.linesep.join(lines) + self.linesep
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default = EmailPolicy()
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# Make the default policy use the class default header_factory
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del default.header_factory
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strict = default.clone(raise_on_defect=True)
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SMTP = default.clone(linesep='\r\n')
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HTTP = default.clone(linesep='\r\n', max_line_length=None)
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SMTPUTF8 = SMTP.clone(utf8=True)
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