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headerregistry.py
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"""Representing and manipulating email headers via custom objects. This module provides an implementation of the HeaderRegistry API. The implementation is designed to flexibly follow RFC5322 rules. Eventually HeaderRegistry will be a public API, but it isn't yet, and will probably change some before that happens. """ from types import MappingProxyType from email import utils from email import errors from email import _header_value_parser as parser class Address: def __init__(self, display_name='', username='', domain='', addr_spec=None): """Create an object representing a full email address. An address can have a 'display_name', a 'username', and a 'domain'. In addition to specifying the username and domain separately, they may be specified together by using the addr_spec keyword *instead of* the username and domain keywords. If an addr_spec string is specified it must be properly quoted according to RFC 5322 rules; an error will be raised if it is not. An Address object has display_name, username, domain, and addr_spec attributes, all of which are read-only. The addr_spec and the string value of the object are both quoted according to RFC5322 rules, but without any Content Transfer Encoding. """ inputs = ''.join(filter(None, (display_name, username, domain, addr_spec))) if '\r' in inputs or '\n' in inputs: raise ValueError("invalid arguments; address parts cannot contain CR or LF") # This clause with its potential 'raise' may only happen when an # application program creates an Address object using an addr_spec # keyword. The email library code itself must always supply username # and domain. if addr_spec is not None: if username or domain: raise TypeError("addrspec specified when username and/or " "domain also specified") a_s, rest = parser.get_addr_spec(addr_spec) if rest: raise ValueError("Invalid addr_spec; only '{}' " "could be parsed from '{}'".format( a_s, addr_spec)) if a_s.all_defects: raise a_s.all_defects[0] username = a_s.local_part domain = a_s.domain self._display_name = display_name self._username = username self._domain = domain @property def display_name(self): return self._display_name @property def username(self): return self._username @property def domain(self): return self._domain @property def addr_spec(self): """The addr_spec (username@domain) portion of the address, quoted according to RFC 5322 rules, but with no Content Transfer Encoding. """ nameset = set(self.username) if len(nameset) > len(nameset-parser.DOT_ATOM_ENDS): lp = parser.quote_string(self.username) else: lp = self.username if self.domain: return lp + '@' + self.domain if not lp: return '<>' return lp def __repr__(self): return "{}(display_name={!r}, username={!r}, domain={!r})".format( self.__class__.__name__, self.display_name, self.username, self.domain) def __str__(self): nameset = set(self.display_name) if len(nameset) > len(nameset-parser.SPECIALS): disp = parser.quote_string(self.display_name) else: disp = self.display_name if disp: addr_spec = '' if self.addr_spec=='<>' else self.addr_spec return "{} <{}>".format(disp, addr_spec) return self.addr_spec def __eq__(self, other): if type(other) != type(self): return False return (self.display_name == other.display_name and self.username == other.username and self.domain == other.domain) class Group: def __init__(self, display_name=None, addresses=None): """Create an object representing an address group. An address group consists of a display_name followed by colon and a list of addresses (see Address) terminated by a semi-colon. The Group is created by specifying a display_name and a possibly empty list of Address objects. A Group can also be used to represent a single address that is not in a group, which is convenient when manipulating lists that are a combination of Groups and individual Addresses. In this case the display_name should be set to None. In particular, the string representation of a Group whose display_name is None is the same as the Address object, if there is one and only one Address object in the addresses list. """ self._display_name = display_name self._addresses = tuple(addresses) if addresses else tuple() @property def display_name(self): return self._display_name @property def addresses(self): return self._addresses def __repr__(self): return "{}(display_name={!r}, addresses={!r}".format( self.__class__.__name__, self.display_name, self.addresses) def __str__(self): if self.display_name is None and len(self.addresses)==1: return str(self.addresses[0]) disp = self.display_name if disp is not None: nameset = set(disp) if len(nameset) > len(nameset-parser.SPECIALS): disp = parser.quote_string(disp) adrstr = ", ".join(str(x) for x in self.addresses) adrstr = ' ' + adrstr if adrstr else adrstr return "{}:{};".format(disp, adrstr) def __eq__(self, other): if type(other) != type(self): return False return (self.display_name == other.display_name and self.addresses == other.addresses) # Header Classes # class BaseHeader(str): """Base class for message headers. Implements generic behavior and provides tools for subclasses. A subclass must define a classmethod named 'parse' that takes an unfolded value string and a dictionary as its arguments. The dictionary will contain one key, 'defects', initialized to an empty list. After the call the dictionary must contain two additional keys: parse_tree, set to the parse tree obtained from parsing the header, and 'decoded', set to the string value of the idealized representation of the data from the value. (That is, encoded words are decoded, and values that have canonical representations are so represented.) The defects key is intended to collect parsing defects, which the message parser will subsequently dispose of as appropriate. The parser should not, insofar as practical, raise any errors. Defects should be added to the list instead. The standard header parsers register defects for RFC compliance issues, for obsolete RFC syntax, and for unrecoverable parsing errors. The parse method may add additional keys to the dictionary. In this case the subclass must define an 'init' method, which will be passed the dictionary as its keyword arguments. The method should use (usually by setting them as the value of similarly named attributes) and remove all the extra keys added by its parse method, and then use super to call its parent class with the remaining arguments and keywords. The subclass should also make sure that a 'max_count' attribute is defined that is either None or 1. XXX: need to better define this API. """ def __new__(cls, name, value): kwds = {'defects': []} cls.parse(value, kwds) if utils._has_surrogates(kwds['decoded']): kwds['decoded'] = utils._sanitize(kwds['decoded']) self = str.__new__(cls, kwds['decoded']) del kwds['decoded'] self.init(name, **kwds) return self def init(self, name, *, parse_tree, defects): self._name = name self._parse_tree = parse_tree self._defects = defects @property def name(self): return self._name @property def defects(self): return tuple(self._defects) def __reduce__(self): return ( _reconstruct_header, ( self.__class__.__name__, self.__class__.__bases__, str(self), ), self.__dict__) @classmethod def _reconstruct(cls, value): return str.__new__(cls, value) def fold(self, *, policy): """Fold header according to policy. The parsed representation of the header is folded according to RFC5322 rules, as modified by the policy. If the parse tree contains surrogateescaped bytes, the bytes are CTE encoded using the charset 'unknown-8bit". Any non-ASCII characters in the parse tree are CTE encoded using charset utf-8. XXX: make this a policy setting. The returned value is an ASCII-only string possibly containing linesep characters, and ending with a linesep character. The string includes the header name and the ': ' separator. """ # At some point we need to put fws here if it was in the source. header = parser.Header([ parser.HeaderLabel([ parser.ValueTerminal(self.name, 'header-name'), parser.ValueTerminal(':', 'header-sep')]), ]) if self._parse_tree: header.append( parser.CFWSList([parser.WhiteSpaceTerminal(' ', 'fws')])) header.append(self._parse_tree) return header.fold(policy=policy) def _reconstruct_header(cls_name, bases, value): return type(cls_name, bases, {})._reconstruct(value) class UnstructuredHeader: max_count = None value_parser = staticmethod(parser.get_unstructured) @classmethod def parse(cls, value, kwds): kwds['parse_tree'] = cls.value_parser(value) kwds['decoded'] = str(kwds['parse_tree']) class UniqueUnstructuredHeader(UnstructuredHeader): max_count = 1 class DateHeader: """Header whose value consists of a single timestamp. Provides an additional attribute, datetime, which is either an aware datetime using a timezone, or a naive datetime if the timezone in the input string is -0000. Also accepts a datetime as input. The 'value' attribute is the normalized form of the timestamp, which means it is the output of format_datetime on the datetime. """ max_count = None # This is used only for folding, not for creating 'decoded'. value_parser = staticmethod(parser.get_unstructured) @classmethod def parse(cls, value, kwds): if not value: kwds['defects'].append(errors.HeaderMissingRequiredValue()) kwds['datetime'] = None kwds['decoded'] = '' kwds['parse_tree'] = parser.TokenList() return if isinstance(value, str): value = utils.parsedate_to_datetime(value) kwds['datetime'] = value kwds['decoded'] = utils.format_datetime(kwds['datetime']) kwds['parse_tree'] = cls.value_parser(kwds['decoded']) def init(self, *args, **kw): self._datetime = kw.pop('datetime') super().init(*args, **kw) @property def datetime(self): return self._datetime class UniqueDateHeader(DateHeader): max_count = 1 class AddressHeader: max_count = None @staticmethod def value_parser(value): address_list, value = parser.get_address_list(value) assert not value, 'this should not happen' return address_list @classmethod def parse(cls, value, kwds): if isinstance(value, str): # We are translating here from the RFC language (address/mailbox) # to our API language (group/address). kwds['parse_tree'] = address_list = cls.value_parser(value) groups = [] for addr in address_list.addresses: groups.append(Group(addr.display_name, [Address(mb.display_name or '', mb.local_part or '', mb.domain or '') for mb in addr.all_mailboxes])) defects = list(address_list.all_defects) else: # Assume it is Address/Group stuff if not hasattr(value, '__iter__'): value = [value] groups = [Group(None, [item]) if not hasattr(item, 'addresses') else item for item in value] defects = [] kwds['groups'] = groups kwds['defects'] = defects kwds['decoded'] = ', '.join([str(item) for item in groups]) if 'parse_tree' not in kwds: kwds['parse_tree'] = cls.value_parser(kwds['decoded']) def init(self, *args, **kw): self._groups = tuple(kw.pop('groups')) self._addresses = None super().init(*args, **kw) @property def groups(self): return self._groups @property def addresses(self): if self._addresses is None: self._addresses = tuple(address for group in self._groups for address in group.addresses) return self._addresses class UniqueAddressHeader(AddressHeader): max_count = 1 class SingleAddressHeader(AddressHeader): @property def address(self): if len(self.addresses)!=1: raise ValueError(("value of single address header {} is not " "a single address").format(self.name)) return self.addresses[0] class UniqueSingleAddressHeader(SingleAddressHeader): max_count = 1 class MIMEVersionHeader: max_count = 1 value_parser = staticmethod(parser.parse_mime_version) @classmethod def parse(cls, value, kwds): kwds['parse_tree'] = parse_tree = cls.value_parser(value) kwds['decoded'] = str(parse_tree) kwds['defects'].extend(parse_tree.all_defects) kwds['major'] = None if parse_tree.minor is None else parse_tree.major kwds['minor'] = parse_tree.minor if parse_tree.minor is not None: kwds['version'] = '{}.{}'.format(kwds['major'], kwds['minor']) else: kwds['version'] = None def init(self, *args, **kw): self._version = kw.pop('version') self._major = kw.pop('major') self._minor = kw.pop('minor') super().init(*args, **kw) @property def major(self): return self._major @property def minor(self): return self._minor @property def version(self): return self._version class ParameterizedMIMEHeader: # Mixin that handles the params dict. Must be subclassed and # a property value_parser for the specific header provided. max_count = 1 @classmethod def parse(cls, value, kwds): kwds['parse_tree'] = parse_tree = cls.value_parser(value) kwds['decoded'] = str(parse_tree) kwds['defects'].extend(parse_tree.all_defects) if parse_tree.params is None: kwds['params'] = {} else: # The MIME RFCs specify that parameter ordering is arbitrary. kwds['params'] = {utils._sanitize(name).lower(): utils._sanitize(value) for name, value in parse_tree.params} def init(self, *args, **kw): self._params = kw.pop('params') super().init(*args, **kw) @property def params(self): return MappingProxyType(self._params) class ContentTypeHeader(ParameterizedMIMEHeader): value_parser = staticmethod(parser.parse_content_type_header) def init(self, *args, **kw): super().init(*args, **kw) self._maintype = utils._sanitize(self._parse_tree.maintype) self._subtype = utils._sanitize(self._parse_tree.subtype) @property def maintype(self): return self._maintype @property def subtype(self): return self._subtype @property def content_type(self): return self.maintype + '/' + self.subtype class ContentDispositionHeader(ParameterizedMIMEHeader): value_parser = staticmethod(parser.parse_content_disposition_header) def init(self, *args, **kw): super().init(*args, **kw) cd = self._parse_tree.content_disposition self._content_disposition = cd if cd is None else utils._sanitize(cd) @property def content_disposition(self): return self._content_disposition class ContentTransferEncodingHeader: max_count = 1 value_parser = staticmethod(parser.parse_content_transfer_encoding_header) @classmethod def parse(cls, value, kwds): kwds['parse_tree'] = parse_tree = cls.value_parser(value) kwds['decoded'] = str(parse_tree) kwds['defects'].extend(parse_tree.all_defects) def init(self, *args, **kw): super().init(*args, **kw) self._cte = utils._sanitize(self._parse_tree.cte) @property def cte(self): return self._cte class MessageIDHeader: max_count = 1 value_parser = staticmethod(parser.parse_message_id) @classmethod def parse(cls, value, kwds): kwds['parse_tree'] = parse_tree = cls.value_parser(value) kwds['decoded'] = str(parse_tree) kwds['defects'].extend(parse_tree.all_defects) # The header factory # _default_header_map = { 'subject': UniqueUnstructuredHeader, 'date': UniqueDateHeader, 'resent-date': DateHeader, 'orig-date': UniqueDateHeader, 'sender': UniqueSingleAddressHeader, 'resent-sender': SingleAddressHeader, 'to': UniqueAddressHeader, 'resent-to': AddressHeader, 'cc': UniqueAddressHeader, 'resent-cc': AddressHeader, 'bcc': UniqueAddressHeader, 'resent-bcc': AddressHeader, 'from': UniqueAddressHeader, 'resent-from': AddressHeader, 'reply-to': UniqueAddressHeader, 'mime-version': MIMEVersionHeader, 'content-type': ContentTypeHeader, 'content-disposition': ContentDispositionHeader, 'content-transfer-encoding': ContentTransferEncodingHeader, 'message-id': MessageIDHeader, } class HeaderRegistry: """A header_factory and header registry.""" def __init__(self, base_class=BaseHeader, default_class=UnstructuredHeader, use_default_map=True): """Create a header_factory that works with the Policy API. base_class is the class that will be the last class in the created header class's __bases__ list. default_class is the class that will be used if "name" (see __call__) does not appear in the registry. use_default_map controls whether or not the default mapping of names to specialized classes is copied in to the registry when the factory is created. The default is True. """ self.registry = {} self.base_class = base_class self.default_class = default_class if use_default_map: self.registry.update(_default_header_map) def map_to_type(self, name, cls): """Register cls as the specialized class for handling "name" headers. """ self.registry[name.lower()] = cls def __getitem__(self, name): cls = self.registry.get(name.lower(), self.default_class) return type('_'+cls.__name__, (cls, self.base_class), {}) def __call__(self, name, value): """Create a header instance for header 'name' from 'value'. Creates a header instance by creating a specialized class for parsing and representing the specified header by combining the factory base_class with a specialized class from the registry or the default_class, and passing the name and value to the constructed class's constructor. """ return self[name](name, value)