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_header_value_parser.py
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3150 lines (2741 loc) · 110 KB
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"""Header value parser implementing various email-related RFC parsing rules.
The parsing methods defined in this module implement various email related
parsing rules. Principal among them is RFC 5322, which is the followon
to RFC 2822 and primarily a clarification of the former. It also implements
RFC 2047 encoded word decoding.
RFC 5322 goes to considerable trouble to maintain backward compatibility with
RFC 822 in the parse phase, while cleaning up the structure on the generation
phase. This parser supports correct RFC 5322 generation by tagging white space
as folding white space only when folding is allowed in the non-obsolete rule
sets. Actually, the parser is even more generous when accepting input than RFC
5322 mandates, following the spirit of Postel's Law, which RFC 5322 encourages.
Where possible deviations from the standard are annotated on the 'defects'
attribute of tokens that deviate.
The general structure of the parser follows RFC 5322, and uses its terminology
where there is a direct correspondence. Where the implementation requires a
somewhat different structure than that used by the formal grammar, new terms
that mimic the closest existing terms are used. Thus, it really helps to have
a copy of RFC 5322 handy when studying this code.
Input to the parser is a string that has already been unfolded according to
RFC 5322 rules. According to the RFC this unfolding is the very first step, and
this parser leaves the unfolding step to a higher level message parser, which
will have already detected the line breaks that need unfolding while
determining the beginning and end of each header.
The output of the parser is a TokenList object, which is a list subclass. A
TokenList is a recursive data structure. The terminal nodes of the structure
are Terminal objects, which are subclasses of str. These do not correspond
directly to terminal objects in the formal grammar, but are instead more
practical higher level combinations of true terminals.
All TokenList and Terminal objects have a 'value' attribute, which produces the
semantically meaningful value of that part of the parse subtree. The value of
all whitespace tokens (no matter how many sub-tokens they may contain) is a
single space, as per the RFC rules. This includes 'CFWS', which is herein
included in the general class of whitespace tokens. There is one exception to
the rule that whitespace tokens are collapsed into single spaces in values: in
the value of a 'bare-quoted-string' (a quoted-string with no leading or
trailing whitespace), any whitespace that appeared between the quotation marks
is preserved in the returned value. Note that in all Terminal strings quoted
pairs are turned into their unquoted values.
All TokenList and Terminal objects also have a string value, which attempts to
be a "canonical" representation of the RFC-compliant form of the substring that
produced the parsed subtree, including minimal use of quoted pair quoting.
Whitespace runs are not collapsed.
Comment tokens also have a 'content' attribute providing the string found
between the parens (including any nested comments) with whitespace preserved.
All TokenList and Terminal objects have a 'defects' attribute which is a
possibly empty list all of the defects found while creating the token. Defects
may appear on any token in the tree, and a composite list of all defects in the
subtree is available through the 'all_defects' attribute of any node. (For
Terminal notes x.defects == x.all_defects.)
Each object in a parse tree is called a 'token', and each has a 'token_type'
attribute that gives the name from the RFC 5322 grammar that it represents.
Not all RFC 5322 nodes are produced, and there is one non-RFC 5322 node that
may be produced: 'ptext'. A 'ptext' is a string of printable ascii characters.
It is returned in place of lists of (ctext/quoted-pair) and
(qtext/quoted-pair).
XXX: provide complete list of token types.
"""
import re
import sys
import urllib # For urllib.parse.unquote
from string import hexdigits
from operator import itemgetter
from email import _encoded_words as _ew
from email import errors
from email import utils
#
# Useful constants and functions
#
_WSP = ' \t'
WSP = set(_WSP)
CFWS_LEADER = WSP | set('(')
SPECIALS = set(r'()<>@,:;.\"[]')
ATOM_ENDS = SPECIALS | WSP
DOT_ATOM_ENDS = ATOM_ENDS - set('.')
# '.', '"', and '(' do not end phrases in order to support obs-phrase
PHRASE_ENDS = SPECIALS - set('."(')
TSPECIALS = (SPECIALS | set('/?=')) - set('.')
TOKEN_ENDS = TSPECIALS | WSP
ASPECIALS = TSPECIALS | set("*'%")
ATTRIBUTE_ENDS = ASPECIALS | WSP
EXTENDED_ATTRIBUTE_ENDS = ATTRIBUTE_ENDS - set('%')
NLSET = {'\n', '\r'}
SPECIALSNL = SPECIALS | NLSET
def make_quoted_pairs(value):
"""Escape dquote and backslash for use within a quoted-string."""
return str(value).replace('\\', '\\\\').replace('"', '\\"')
def make_parenthesis_pairs(value):
"""Escape parenthesis and backslash for use within a comment."""
return str(value).replace('\\', '\\\\') \
.replace('(', '\\(').replace(')', '\\)')
def quote_string(value):
escaped = make_quoted_pairs(value)
return f'"{escaped}"'
# Match a RFC 2047 word, looks like =?utf-8?q?someword?=
rfc2047_matcher = re.compile(r'''
=\? # literal =?
[^?]* # charset
\? # literal ?
[qQbB] # literal 'q' or 'b', case insensitive
\? # literal ?
.*? # encoded word
\?= # literal ?=
''', re.VERBOSE | re.MULTILINE)
#
# TokenList and its subclasses
#
class TokenList(list):
token_type = None
syntactic_break = True
ew_combine_allowed = True
def __init__(self, *args, **kw):
super().__init__(*args, **kw)
self.defects = []
def __str__(self):
return ''.join(str(x) for x in self)
def __repr__(self):
return '{}({})'.format(self.__class__.__name__,
super().__repr__())
@property
def value(self):
return ''.join(x.value for x in self if x.value)
@property
def all_defects(self):
return sum((x.all_defects for x in self), self.defects)
def startswith_fws(self):
return self[0].startswith_fws()
@property
def as_ew_allowed(self):
"""True if all top level tokens of this part may be RFC2047 encoded."""
return all(part.as_ew_allowed for part in self)
@property
def comments(self):
comments = []
for token in self:
comments.extend(token.comments)
return comments
def fold(self, *, policy):
return _refold_parse_tree(self, policy=policy)
def pprint(self, indent=''):
print(self.ppstr(indent=indent))
def ppstr(self, indent=''):
return '\n'.join(self._pp(indent=indent))
def _pp(self, indent=''):
yield '{}{}/{}('.format(
indent,
self.__class__.__name__,
self.token_type)
for token in self:
if not hasattr(token, '_pp'):
yield (indent + ' !! invalid element in token '
'list: {!r}'.format(token))
else:
yield from token._pp(indent+' ')
if self.defects:
extra = ' Defects: {}'.format(self.defects)
else:
extra = ''
yield '{}){}'.format(indent, extra)
class WhiteSpaceTokenList(TokenList):
@property
def value(self):
return ' '
@property
def comments(self):
return [x.content for x in self if x.token_type=='comment']
class UnstructuredTokenList(TokenList):
token_type = 'unstructured'
class Phrase(TokenList):
token_type = 'phrase'
class Word(TokenList):
token_type = 'word'
class CFWSList(WhiteSpaceTokenList):
token_type = 'cfws'
class Atom(TokenList):
token_type = 'atom'
class Token(TokenList):
token_type = 'token'
encode_as_ew = False
class EncodedWord(TokenList):
token_type = 'encoded-word'
cte = None
charset = None
lang = None
class QuotedString(TokenList):
token_type = 'quoted-string'
@property
def content(self):
for x in self:
if x.token_type == 'bare-quoted-string':
return x.value
@property
def quoted_value(self):
res = []
for x in self:
if x.token_type == 'bare-quoted-string':
res.append(str(x))
else:
res.append(x.value)
return ''.join(res)
@property
def stripped_value(self):
for token in self:
if token.token_type == 'bare-quoted-string':
return token.value
class BareQuotedString(QuotedString):
token_type = 'bare-quoted-string'
def __str__(self):
return quote_string(''.join(str(x) for x in self))
@property
def value(self):
return ''.join(str(x) for x in self)
class Comment(WhiteSpaceTokenList):
token_type = 'comment'
def __str__(self):
return ''.join(sum([
["("],
[self.quote(x) for x in self],
[")"],
], []))
def quote(self, value):
if value.token_type == 'comment':
return str(value)
return str(value).replace('\\', '\\\\').replace(
'(', r'\(').replace(
')', r'\)')
@property
def content(self):
return ''.join(str(x) for x in self)
@property
def comments(self):
return [self.content]
class AddressList(TokenList):
token_type = 'address-list'
@property
def addresses(self):
return [x for x in self if x.token_type=='address']
@property
def mailboxes(self):
return sum((x.mailboxes
for x in self if x.token_type=='address'), [])
@property
def all_mailboxes(self):
return sum((x.all_mailboxes
for x in self if x.token_type=='address'), [])
class Address(TokenList):
token_type = 'address'
@property
def display_name(self):
if self[0].token_type == 'group':
return self[0].display_name
@property
def mailboxes(self):
if self[0].token_type == 'mailbox':
return [self[0]]
elif self[0].token_type == 'invalid-mailbox':
return []
return self[0].mailboxes
@property
def all_mailboxes(self):
if self[0].token_type == 'mailbox':
return [self[0]]
elif self[0].token_type == 'invalid-mailbox':
return [self[0]]
return self[0].all_mailboxes
class MailboxList(TokenList):
token_type = 'mailbox-list'
@property
def mailboxes(self):
return [x for x in self if x.token_type=='mailbox']
@property
def all_mailboxes(self):
return [x for x in self
if x.token_type in ('mailbox', 'invalid-mailbox')]
class GroupList(TokenList):
token_type = 'group-list'
@property
def mailboxes(self):
if not self or self[0].token_type != 'mailbox-list':
return []
return self[0].mailboxes
@property
def all_mailboxes(self):
if not self or self[0].token_type != 'mailbox-list':
return []
return self[0].all_mailboxes
class Group(TokenList):
token_type = "group"
@property
def mailboxes(self):
if self[2].token_type != 'group-list':
return []
return self[2].mailboxes
@property
def all_mailboxes(self):
if self[2].token_type != 'group-list':
return []
return self[2].all_mailboxes
@property
def display_name(self):
return self[0].display_name
class NameAddr(TokenList):
token_type = 'name-addr'
@property
def display_name(self):
if len(self) == 1:
return None
return self[0].display_name
@property
def local_part(self):
return self[-1].local_part
@property
def domain(self):
return self[-1].domain
@property
def route(self):
return self[-1].route
@property
def addr_spec(self):
return self[-1].addr_spec
class AngleAddr(TokenList):
token_type = 'angle-addr'
@property
def local_part(self):
for x in self:
if x.token_type == 'addr-spec':
return x.local_part
@property
def domain(self):
for x in self:
if x.token_type == 'addr-spec':
return x.domain
@property
def route(self):
for x in self:
if x.token_type == 'obs-route':
return x.domains
@property
def addr_spec(self):
for x in self:
if x.token_type == 'addr-spec':
if x.local_part:
return x.addr_spec
else:
return quote_string(x.local_part) + x.addr_spec
else:
return '<>'
class ObsRoute(TokenList):
token_type = 'obs-route'
@property
def domains(self):
return [x.domain for x in self if x.token_type == 'domain']
class Mailbox(TokenList):
token_type = 'mailbox'
@property
def display_name(self):
if self[0].token_type == 'name-addr':
return self[0].display_name
@property
def local_part(self):
return self[0].local_part
@property
def domain(self):
return self[0].domain
@property
def route(self):
if self[0].token_type == 'name-addr':
return self[0].route
@property
def addr_spec(self):
return self[0].addr_spec
class InvalidMailbox(TokenList):
token_type = 'invalid-mailbox'
@property
def display_name(self):
return None
local_part = domain = route = addr_spec = display_name
class Domain(TokenList):
token_type = 'domain'
as_ew_allowed = False
@property
def domain(self):
return ''.join(super().value.split())
class DotAtom(TokenList):
token_type = 'dot-atom'
class DotAtomText(TokenList):
token_type = 'dot-atom-text'
as_ew_allowed = True
class NoFoldLiteral(TokenList):
token_type = 'no-fold-literal'
as_ew_allowed = False
class AddrSpec(TokenList):
token_type = 'addr-spec'
as_ew_allowed = False
@property
def local_part(self):
return self[0].local_part
@property
def domain(self):
if len(self) < 3:
return None
return self[-1].domain
@property
def value(self):
if len(self) < 3:
return self[0].value
return self[0].value.rstrip()+self[1].value+self[2].value.lstrip()
@property
def addr_spec(self):
nameset = set(self.local_part)
if len(nameset) > len(nameset-DOT_ATOM_ENDS):
lp = quote_string(self.local_part)
else:
lp = self.local_part
if self.domain is not None:
return lp + '@' + self.domain
return lp
class ObsLocalPart(TokenList):
token_type = 'obs-local-part'
as_ew_allowed = False
class DisplayName(Phrase):
token_type = 'display-name'
ew_combine_allowed = False
@property
def display_name(self):
res = TokenList(self)
if len(res) == 0:
return res.value
if res[0].token_type == 'cfws':
res.pop(0)
else:
if (isinstance(res[0], TokenList) and
res[0][0].token_type == 'cfws'):
res[0] = TokenList(res[0][1:])
if res[-1].token_type == 'cfws':
res.pop()
else:
if (isinstance(res[-1], TokenList) and
res[-1][-1].token_type == 'cfws'):
res[-1] = TokenList(res[-1][:-1])
return res.value
@property
def value(self):
quote = False
if self.defects:
quote = True
else:
for x in self:
if x.token_type == 'quoted-string':
quote = True
if len(self) != 0 and quote:
pre = post = ''
if (self[0].token_type == 'cfws' or
isinstance(self[0], TokenList) and
self[0][0].token_type == 'cfws'):
pre = ' '
if (self[-1].token_type == 'cfws' or
isinstance(self[-1], TokenList) and
self[-1][-1].token_type == 'cfws'):
post = ' '
return pre+quote_string(self.display_name)+post
else:
return super().value
class LocalPart(TokenList):
token_type = 'local-part'
as_ew_allowed = False
@property
def value(self):
if self[0].token_type == "quoted-string":
return self[0].quoted_value
else:
return self[0].value
@property
def local_part(self):
# Strip whitespace from front, back, and around dots.
res = [DOT]
last = DOT
last_is_tl = False
for tok in self[0] + [DOT]:
if tok.token_type == 'cfws':
continue
if (last_is_tl and tok.token_type == 'dot' and
last[-1].token_type == 'cfws'):
res[-1] = TokenList(last[:-1])
is_tl = isinstance(tok, TokenList)
if (is_tl and last.token_type == 'dot' and
tok[0].token_type == 'cfws'):
res.append(TokenList(tok[1:]))
else:
res.append(tok)
last = res[-1]
last_is_tl = is_tl
res = TokenList(res[1:-1])
return res.value
class DomainLiteral(TokenList):
token_type = 'domain-literal'
as_ew_allowed = False
@property
def domain(self):
return ''.join(super().value.split())
@property
def ip(self):
for x in self:
if x.token_type == 'ptext':
return x.value
class MIMEVersion(TokenList):
token_type = 'mime-version'
major = None
minor = None
class Parameter(TokenList):
token_type = 'parameter'
sectioned = False
extended = False
charset = 'us-ascii'
@property
def section_number(self):
# Because the first token, the attribute (name) eats CFWS, the second
# token is always the section if there is one.
return self[1].number if self.sectioned else 0
@property
def param_value(self):
# This is part of the "handle quoted extended parameters" hack.
for token in self:
if token.token_type == 'value':
return token.stripped_value
if token.token_type == 'quoted-string':
for token in token:
if token.token_type == 'bare-quoted-string':
for token in token:
if token.token_type == 'value':
return token.stripped_value
return ''
class InvalidParameter(Parameter):
token_type = 'invalid-parameter'
class Attribute(TokenList):
token_type = 'attribute'
@property
def stripped_value(self):
for token in self:
if token.token_type.endswith('attrtext'):
return token.value
class Section(TokenList):
token_type = 'section'
number = None
class Value(TokenList):
token_type = 'value'
@property
def stripped_value(self):
token = self[0]
if token.token_type == 'cfws':
token = self[1]
if token.token_type.endswith(
('quoted-string', 'attribute', 'extended-attribute')):
return token.stripped_value
return self.value
class MimeParameters(TokenList):
token_type = 'mime-parameters'
syntactic_break = False
@property
def params(self):
# The RFC specifically states that the ordering of parameters is not
# guaranteed and may be reordered by the transport layer. So we have
# to assume the RFC 2231 pieces can come in any order. However, we
# output them in the order that we first see a given name, which gives
# us a stable __str__.
params = {} # Using order preserving dict from Python 3.7+
for token in self:
if not token.token_type.endswith('parameter'):
continue
if token[0].token_type != 'attribute':
continue
name = token[0].value.strip()
if name not in params:
params[name] = []
params[name].append((token.section_number, token))
for name, parts in params.items():
parts = sorted(parts, key=itemgetter(0))
first_param = parts[0][1]
charset = first_param.charset
# Our arbitrary error recovery is to ignore duplicate parameters,
# to use appearance order if there are duplicate rfc 2231 parts,
# and to ignore gaps. This mimics the error recovery of get_param.
if not first_param.extended and len(parts) > 1:
if parts[1][0] == 0:
parts[1][1].defects.append(errors.InvalidHeaderDefect(
'duplicate parameter name; duplicate(s) ignored'))
parts = parts[:1]
# Else assume the *0* was missing...note that this is different
# from get_param, but we registered a defect for this earlier.
value_parts = []
i = 0
for section_number, param in parts:
if section_number != i:
# We could get fancier here and look for a complete
# duplicate extended parameter and ignore the second one
# seen. But we're not doing that. The old code didn't.
if not param.extended:
param.defects.append(errors.InvalidHeaderDefect(
'duplicate parameter name; duplicate ignored'))
continue
else:
param.defects.append(errors.InvalidHeaderDefect(
"inconsistent RFC2231 parameter numbering"))
i += 1
value = param.param_value
if param.extended:
try:
value = urllib.parse.unquote_to_bytes(value)
except UnicodeEncodeError:
# source had surrogate escaped bytes. What we do now
# is a bit of an open question. I'm not sure this is
# the best choice, but it is what the old algorithm did
value = urllib.parse.unquote(value, encoding='latin-1')
else:
try:
# Explicitly look up the codec for warning generation, see gh-140030
# Can be removed in 3.17
import codecs
codecs.lookup(charset)
value = value.decode(charset, 'surrogateescape')
except (LookupError, UnicodeEncodeError):
# XXX: there should really be a custom defect for
# unknown character set to make it easy to find,
# because otherwise unknown charset is a silent
# failure.
value = value.decode('us-ascii', 'surrogateescape')
if utils._has_surrogates(value):
param.defects.append(errors.UndecodableBytesDefect())
value_parts.append(value)
value = ''.join(value_parts)
yield name, value
def __str__(self):
params = []
for name, value in self.params:
if value:
params.append('{}={}'.format(name, quote_string(value)))
else:
params.append(name)
params = '; '.join(params)
return ' ' + params if params else ''
class ParameterizedHeaderValue(TokenList):
# Set this false so that the value doesn't wind up on a new line even
# if it and the parameters would fit there but not on the first line.
syntactic_break = False
@property
def params(self):
for token in reversed(self):
if token.token_type == 'mime-parameters':
return token.params
return {}
class ContentType(ParameterizedHeaderValue):
token_type = 'content-type'
as_ew_allowed = False
maintype = 'text'
subtype = 'plain'
class ContentDisposition(ParameterizedHeaderValue):
token_type = 'content-disposition'
as_ew_allowed = False
content_disposition = None
class ContentTransferEncoding(TokenList):
token_type = 'content-transfer-encoding'
as_ew_allowed = False
cte = '7bit'
class HeaderLabel(TokenList):
token_type = 'header-label'
as_ew_allowed = False
class MsgID(TokenList):
token_type = 'msg-id'
as_ew_allowed = False
def fold(self, policy):
# message-id tokens may not be folded.
return str(self) + policy.linesep
class MessageID(MsgID):
token_type = 'message-id'
class InvalidMessageID(MessageID):
token_type = 'invalid-message-id'
class MessageIDList(TokenList):
token_type = 'message-id-list'
@property
def message_ids(self):
return [x for x in self if x.token_type=='msg-id']
class Header(TokenList):
token_type = 'header'
#
# Terminal classes and instances
#
class Terminal(str):
as_ew_allowed = True
ew_combine_allowed = True
syntactic_break = True
def __new__(cls, value, token_type):
self = super().__new__(cls, value)
self.token_type = token_type
self.defects = []
return self
def __repr__(self):
return "{}({})".format(self.__class__.__name__, super().__repr__())
def pprint(self):
print(self.__class__.__name__ + '/' + self.token_type)
@property
def all_defects(self):
return list(self.defects)
def _pp(self, indent=''):
return ["{}{}/{}({}){}".format(
indent,
self.__class__.__name__,
self.token_type,
super().__repr__(),
'' if not self.defects else ' {}'.format(self.defects),
)]
def pop_trailing_ws(self):
# This terminates the recursion.
return None
@property
def comments(self):
return []
def __getnewargs__(self):
return(str(self), self.token_type)
class WhiteSpaceTerminal(Terminal):
@property
def value(self):
return ' '
def startswith_fws(self):
return self and self[0] in WSP
class ValueTerminal(Terminal):
@property
def value(self):
return self
def startswith_fws(self):
return False
class EWWhiteSpaceTerminal(WhiteSpaceTerminal):
@property
def value(self):
return ''
def __str__(self):
return ''
class _InvalidEwError(errors.HeaderParseError):
"""Invalid encoded word found while parsing headers."""
# XXX these need to become classes and used as instances so
# that a program can't change them in a parse tree and screw
# up other parse trees. Maybe should have tests for that, too.
DOT = ValueTerminal('.', 'dot')
ListSeparator = ValueTerminal(',', 'list-separator')
ListSeparator.as_ew_allowed = False
ListSeparator.syntactic_break = False
RouteComponentMarker = ValueTerminal('@', 'route-component-marker')
#
# Parser
#
# Parse strings according to RFC822/2047/2822/5322 rules.
#
# This is a stateless parser. Each get_XXX function accepts a string and
# returns either a Terminal or a TokenList representing the RFC object named
# by the method and a string containing the remaining unparsed characters
# from the input. Thus a parser method consumes the next syntactic construct
# of a given type and returns a token representing the construct plus the
# unparsed remainder of the input string.