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Diffstat (limited to 'modules/language/python/module/email/header.py')
| -rw-r--r-- | modules/language/python/module/email/header.py | 579 |
1 files changed, 579 insertions, 0 deletions
diff --git a/modules/language/python/module/email/header.py b/modules/language/python/module/email/header.py new file mode 100644 index 0000000..ac3f46c --- /dev/null +++ b/modules/language/python/module/email/header.py @@ -0,0 +1,579 @@ +module(email,header) +# Copyright (C) 2002-2007 Python Software Foundation +# Author: Ben Gertzfield, Barry Warsaw +# Contact: email-sig@python.org + +"""Header encoding and decoding functionality.""" + +__all__ = [ + 'Header', + 'decode_header', + 'make_header', + ] + +import re +import binascii + +import email.quoprimime as quoprimime +import email.base64mime as base64mime + +from email.errors import HeaderParseError +import email.charset as _charset +Charset = _charset.Charset + +NL = '\n' +SPACE = ' ' +BSPACE = b' ' +SPACE8 = ' ' * 8 +EMPTYSTRING = '' +MAXLINELEN = 78 +FWS = ' \t' + +USASCII = Charset('us-ascii') +UTF8 = Charset('utf-8') + +# Match encoded-word strings in the form =?charset?q?Hello_World?= +ecre = re.compile(r''' + =\? # literal =? + (?P<charset>[^?]*?) # non-greedy up to the next ? is the charset + \? # literal ? + (?P<encoding>[qb]) # either a "q" or a "b", case insensitive + \? # literal ? + (?P<encoded>.*?) # non-greedy up to the next ?= is the encoded string + \?= # literal ?= + ''', re.VERBOSE | re.IGNORECASE | re.MULTILINE) + +# Field name regexp, including trailing colon, but not separating whitespace, +# according to RFC 2822. Character range is from tilde to exclamation mark. +# For use with .match() +fcre = re.compile(r'[\041-\176]+:$') + +# Find a header embedded in a putative header value. Used to check for +# header injection attack. +_embedded_header = re.compile(r'\n[^ \t]+:') + + + +# Helpers +_max_append = quoprimime._max_append + + + +def decode_header(header): + """Decode a message header value without converting charset. + + Returns a list of (string, charset) pairs containing each of the decoded + parts of the header. Charset is None for non-encoded parts of the header, + otherwise a lower-case string containing the name of the character set + specified in the encoded string. + + header may be a string that may or may not contain RFC2047 encoded words, + or it may be a Header object. + + An email.errors.HeaderParseError may be raised when certain decoding error + occurs (e.g. a base64 decoding exception). + """ + # If it is a Header object, we can just return the encoded chunks. + if hasattr(header, '_chunks'): + return [(_charset._encode(string, str(charset)), str(charset)) + for string, charset in header._chunks] + # If no encoding, just return the header with no charset. + if not ecre.search(header): + return [(header, None)] + # First step is to parse all the encoded parts into triplets of the form + # (encoded_string, encoding, charset). For unencoded strings, the last + # two parts will be None. + words = [] + for line in header.splitlines(): + parts = ecre.split(line) + first = True + while parts: + unencoded = parts.pop(0) + if first: + unencoded = unencoded.lstrip() + first = False + if unencoded: + words.append((unencoded, None, None)) + if parts: + charset = parts.pop(0).lower() + encoding = parts.pop(0).lower() + encoded = parts.pop(0) + words.append((encoded, encoding, charset)) + # Now loop over words and remove words that consist of whitespace + # between two encoded strings. + droplist = [] + for n, w in enumerate(words): + if n>1 and w[1] and words[n-2][1] and words[n-1][0].isspace(): + droplist.append(n-1) + for d in reversed(droplist): + del words[d] + + # The next step is to decode each encoded word by applying the reverse + # base64 or quopri transformation. decoded_words is now a list of the + # form (decoded_word, charset). + decoded_words = [] + for encoded_string, encoding, charset in words: + if encoding is None: + # This is an unencoded word. + decoded_words.append((encoded_string, charset)) + elif encoding == 'q': + word = quoprimime.header_decode(encoded_string) + decoded_words.append((word, charset)) + elif encoding == 'b': + paderr = len(encoded_string) % 4 # Postel's law: add missing padding + if paderr: + encoded_string += '==='[:4 - paderr] + try: + word = base64mime.decode(encoded_string) + except binascii.Error: + raise HeaderParseError('Base64 decoding error') + else: + decoded_words.append((word, charset)) + else: + raise AssertionError('Unexpected encoding: ' + encoding) + # Now convert all words to bytes and collapse consecutive runs of + # similarly encoded words. + collapsed = [] + last_word = last_charset = None + for word, charset in decoded_words: + if isinstance(word, str): + word = bytes(word, 'raw-unicode-escape') + if last_word is None: + last_word = word + last_charset = charset + elif charset != last_charset: + collapsed.append((last_word, last_charset)) + last_word = word + last_charset = charset + elif last_charset is None: + last_word += BSPACE + word + else: + last_word += word + collapsed.append((last_word, last_charset)) + return collapsed + + + +def make_header(decoded_seq, maxlinelen=None, header_name=None, + continuation_ws=' '): + """Create a Header from a sequence of pairs as returned by decode_header() + + decode_header() takes a header value string and returns a sequence of + pairs of the format (decoded_string, charset) where charset is the string + name of the character set. + + This function takes one of those sequence of pairs and returns a Header + instance. Optional maxlinelen, header_name, and continuation_ws are as in + the Header constructor. + """ + h = Header(maxlinelen=maxlinelen, header_name=header_name, + continuation_ws=continuation_ws) + for s, charset in decoded_seq: + # None means us-ascii but we can simply pass it on to h.append() + if charset is not None and not isinstance(charset, Charset): + charset = Charset(charset) + h.append(s, charset) + return h + + + +class Header: + def __init__(self, s=None, charset=None, + maxlinelen=None, header_name=None, + continuation_ws=' ', errors='strict'): + """Create a MIME-compliant header that can contain many character sets. + + Optional s is the initial header value. If None, the initial header + value is not set. You can later append to the header with .append() + method calls. s may be a byte string or a Unicode string, but see the + .append() documentation for semantics. + + Optional charset serves two purposes: it has the same meaning as the + charset argument to the .append() method. It also sets the default + character set for all subsequent .append() calls that omit the charset + argument. If charset is not provided in the constructor, the us-ascii + charset is used both as s's initial charset and as the default for + subsequent .append() calls. + + The maximum line length can be specified explicitly via maxlinelen. For + splitting the first line to a shorter value (to account for the field + header which isn't included in s, e.g. `Subject') pass in the name of + the field in header_name. The default maxlinelen is 78 as recommended + by RFC 2822. + + continuation_ws must be RFC 2822 compliant folding whitespace (usually + either a space or a hard tab) which will be prepended to continuation + lines. + + errors is passed through to the .append() call. + """ + if charset is None: + charset = USASCII + elif not isinstance(charset, Charset): + charset = Charset(charset) + self._charset = charset + self._continuation_ws = continuation_ws + self._chunks = [] + if s is not None: + self.append(s, charset, errors) + if maxlinelen is None: + maxlinelen = MAXLINELEN + self._maxlinelen = maxlinelen + if header_name is None: + self._headerlen = 0 + else: + # Take the separating colon and space into account. + self._headerlen = len(header_name) + 2 + + def __str__(self): + """Return the string value of the header.""" + self._normalize() + uchunks = [] + lastcs = None + lastspace = None + for string, charset in self._chunks: + # We must preserve spaces between encoded and non-encoded word + # boundaries, which means for us we need to add a space when we go + # from a charset to None/us-ascii, or from None/us-ascii to a + # charset. Only do this for the second and subsequent chunks. + # Don't add a space if the None/us-ascii string already has + # a space (trailing or leading depending on transition) + nextcs = charset + if nextcs == _charset.UNKNOWN8BIT: + original_bytes = string.encode('ascii', 'surrogateescape') + string = original_bytes.decode('ascii', 'replace') + if uchunks: + hasspace = string and self._nonctext(string[0]) + if lastcs not in (None, 'us-ascii'): + if nextcs in (None, 'us-ascii') and not hasspace: + uchunks.append(SPACE) + nextcs = None + elif nextcs not in (None, 'us-ascii') and not lastspace: + uchunks.append(SPACE) + lastspace = string and self._nonctext(string[-1]) + lastcs = nextcs + uchunks.append(string) + return EMPTYSTRING.join(uchunks) + + # Rich comparison operators for equality only. BAW: does it make sense to + # have or explicitly disable <, <=, >, >= operators? + def __eq__(self, other): + # other may be a Header or a string. Both are fine so coerce + # ourselves to a unicode (of the unencoded header value), swap the + # args and do another comparison. + return other == str(self) + + def append(self, s, charset=None, errors='strict'): + """Append a string to the MIME header. + + Optional charset, if given, should be a Charset instance or the name + of a character set (which will be converted to a Charset instance). A + value of None (the default) means that the charset given in the + constructor is used. + + s may be a byte string or a Unicode string. If it is a byte string + (i.e. isinstance(s, str) is false), then charset is the encoding of + that byte string, and a UnicodeError will be raised if the string + cannot be decoded with that charset. If s is a Unicode string, then + charset is a hint specifying the character set of the characters in + the string. In either case, when producing an RFC 2822 compliant + header using RFC 2047 rules, the string will be encoded using the + output codec of the charset. If the string cannot be encoded to the + output codec, a UnicodeError will be raised. + + Optional `errors' is passed as the errors argument to the decode + call if s is a byte string. + """ + if charset is None: + charset = self._charset + elif not isinstance(charset, Charset): + charset = Charset(charset) + if not isinstance(s, str): + input_charset = charset.input_codec or 'us-ascii' + if input_charset == _charset.UNKNOWN8BIT: + s = s.decode('us-ascii', 'surrogateescape') + else: + s = s.decode(input_charset, errors) + # Ensure that the bytes we're storing can be decoded to the output + # character set, otherwise an early error is raised. + output_charset = charset.output_codec or 'us-ascii' + if output_charset != _charset.UNKNOWN8BIT: + try: + s.encode(output_charset, errors) + except UnicodeEncodeError: + if output_charset!='us-ascii': + raise + charset = UTF8 + self._chunks.append((s, charset)) + + def _nonctext(self, s): + """True if string s is not a ctext character of RFC822. + """ + return s.isspace() or s in ('(', ')', '\\') + + def encode(self, splitchars=';, \t', maxlinelen=None, linesep='\n'): + r"""Encode a message header into an RFC-compliant format. + + There are many issues involved in converting a given string for use in + an email header. Only certain character sets are readable in most + email clients, and as header strings can only contain a subset of + 7-bit ASCII, care must be taken to properly convert and encode (with + Base64 or quoted-printable) header strings. In addition, there is a + 75-character length limit on any given encoded header field, so + line-wrapping must be performed, even with double-byte character sets. + + Optional maxlinelen specifies the maximum length of each generated + line, exclusive of the linesep string. Individual lines may be longer + than maxlinelen if a folding point cannot be found. The first line + will be shorter by the length of the header name plus ": " if a header + name was specified at Header construction time. The default value for + maxlinelen is determined at header construction time. + + Optional splitchars is a string containing characters which should be + given extra weight by the splitting algorithm during normal header + wrapping. This is in very rough support of RFC 2822's `higher level + syntactic breaks': split points preceded by a splitchar are preferred + during line splitting, with the characters preferred in the order in + which they appear in the string. Space and tab may be included in the + string to indicate whether preference should be given to one over the + other as a split point when other split chars do not appear in the line + being split. Splitchars does not affect RFC 2047 encoded lines. + + Optional linesep is a string to be used to separate the lines of + the value. The default value is the most useful for typical + Python applications, but it can be set to \r\n to produce RFC-compliant + line separators when needed. + """ + self._normalize() + if maxlinelen is None: + maxlinelen = self._maxlinelen + # A maxlinelen of 0 means don't wrap. For all practical purposes, + # choosing a huge number here accomplishes that and makes the + # _ValueFormatter algorithm much simpler. + if maxlinelen == 0: + maxlinelen = 1000000 + formatter = _ValueFormatter(self._headerlen, maxlinelen, + self._continuation_ws, splitchars) + lastcs = None + hasspace = lastspace = None + for string, charset in self._chunks: + if hasspace is not None: + hasspace = string and self._nonctext(string[0]) + if lastcs not in (None, 'us-ascii'): + if not hasspace or charset not in (None, 'us-ascii'): + formatter.add_transition() + elif charset not in (None, 'us-ascii') and not lastspace: + formatter.add_transition() + lastspace = string and self._nonctext(string[-1]) + lastcs = charset + hasspace = False + lines = string.splitlines() + if lines: + formatter.feed('', lines[0], charset) + else: + formatter.feed('', '', charset) + for line in lines[1:]: + formatter.newline() + if charset.header_encoding is not None: + formatter.feed(self._continuation_ws, ' ' + line.lstrip(), + charset) + else: + sline = line.lstrip() + fws = line[:len(line)-len(sline)] + formatter.feed(fws, sline, charset) + if len(lines) > 1: + formatter.newline() + if self._chunks: + formatter.add_transition() + value = formatter._str(linesep) + if _embedded_header.search(value): + raise HeaderParseError("header value appears to contain " + "an embedded header: {!r}".format(value)) + return value + + def _normalize(self): + # Step 1: Normalize the chunks so that all runs of identical charsets + # get collapsed into a single unicode string. + chunks = [] + last_charset = None + last_chunk = [] + for string, charset in self._chunks: + if charset == last_charset: + last_chunk.append(string) + else: + if last_charset is not None: + chunks.append((SPACE.join(last_chunk), last_charset)) + last_chunk = [string] + last_charset = charset + if last_chunk: + chunks.append((SPACE.join(last_chunk), last_charset)) + self._chunks = chunks + + + +class _ValueFormatter: + def __init__(self, headerlen, maxlen, continuation_ws, splitchars): + self._maxlen = maxlen + self._continuation_ws = continuation_ws + self._continuation_ws_len = len(continuation_ws) + self._splitchars = splitchars + self._lines = [] + self._current_line = _Accumulator(headerlen) + + def _str(self, linesep): + self.newline() + return linesep.join(self._lines) + + def __str__(self): + return self._str(NL) + + def newline(self): + end_of_line = self._current_line.pop() + if end_of_line != (' ', ''): + self._current_line.push(*end_of_line) + if len(self._current_line) > 0: + if self._current_line.is_onlyws(): + self._lines[-1] += str(self._current_line) + else: + self._lines.append(str(self._current_line)) + self._current_line.reset() + + def add_transition(self): + self._current_line.push(' ', '') + + def feed(self, fws, string, charset): + # If the charset has no header encoding (i.e. it is an ASCII encoding) + # then we must split the header at the "highest level syntactic break" + # possible. Note that we don't have a lot of smarts about field + # syntax; we just try to break on semi-colons, then commas, then + # whitespace. Eventually, this should be pluggable. + if charset.header_encoding is None: + self._ascii_split(fws, string, self._splitchars) + return + # Otherwise, we're doing either a Base64 or a quoted-printable + # encoding which means we don't need to split the line on syntactic + # breaks. We can basically just find enough characters to fit on the + # current line, minus the RFC 2047 chrome. What makes this trickier + # though is that we have to split at octet boundaries, not character + # boundaries but it's only safe to split at character boundaries so at + # best we can only get close. + encoded_lines = charset.header_encode_lines(string, self._maxlengths()) + # The first element extends the current line, but if it's None then + # nothing more fit on the current line so start a new line. + try: + first_line = encoded_lines.pop(0) + except IndexError: + # There are no encoded lines, so we're done. + return + if first_line is not None: + self._append_chunk(fws, first_line) + try: + last_line = encoded_lines.pop() + except IndexError: + # There was only one line. + return + self.newline() + self._current_line.push(self._continuation_ws, last_line) + # Everything else are full lines in themselves. + for line in encoded_lines: + self._lines.append(self._continuation_ws + line) + + def _maxlengths(self): + # The first line's length. + yield self._maxlen - len(self._current_line) + while True: + yield self._maxlen - self._continuation_ws_len + + def _ascii_split(self, fws, string, splitchars): + # The RFC 2822 header folding algorithm is simple in principle but + # complex in practice. Lines may be folded any place where "folding + # white space" appears by inserting a linesep character in front of the + # FWS. The complication is that not all spaces or tabs qualify as FWS, + # and we are also supposed to prefer to break at "higher level + # syntactic breaks". We can't do either of these without intimate + # knowledge of the structure of structured headers, which we don't have + # here. So the best we can do here is prefer to break at the specified + # splitchars, and hope that we don't choose any spaces or tabs that + # aren't legal FWS. (This is at least better than the old algorithm, + # where we would sometimes *introduce* FWS after a splitchar, or the + # algorithm before that, where we would turn all white space runs into + # single spaces or tabs.) + parts = re.split("(["+FWS+"]+)", fws+string) + if parts[0]: + parts[:0] = [''] + else: + parts.pop(0) + for fws, part in zip(*[iter(parts)]*2): + self._append_chunk(fws, part) + + def _append_chunk(self, fws, string): + self._current_line.push(fws, string) + if len(self._current_line) > self._maxlen: + # Find the best split point, working backward from the end. + # There might be none, on a long first line. + for ch in self._splitchars: + for i in range(self._current_line.part_count()-1, 0, -1): + if ch.isspace(): + fws = self._current_line[i][0] + if fws and fws[0]==ch: + break + prevpart = self._current_line[i-1][1] + if prevpart and prevpart[-1]==ch: + break + else: + continue + break + else: + fws, part = self._current_line.pop() + if self._current_line._initial_size > 0: + # There will be a header, so leave it on a line by itself. + self.newline() + if not fws: + # We don't use continuation_ws here because the whitespace + # after a header should always be a space. + fws = ' ' + self._current_line.push(fws, part) + return + remainder = self._current_line.pop_from(i) + self._lines.append(str(self._current_line)) + self._current_line.reset(remainder) + + +class _Accumulator(list): + + def __init__(self, initial_size=0): + self._initial_size = initial_size + super().__init__() + + def push(self, fws, string): + self.append((fws, string)) + + def pop_from(self, i=0): + popped = self[i:] + self[i:] = [] + return popped + + def pop(self): + if self.part_count()==0: + return ('', '') + return super().pop() + + def __len__(self): + return sum((len(fws)+len(part) for fws, part in self), + self._initial_size) + + def __str__(self): + return EMPTYSTRING.join((EMPTYSTRING.join((fws, part)) + for fws, part in self)) + + def reset(self, startval=None): + if startval is None: + startval = [] + self[:] = startval + self._initial_size = 0 + + def is_onlyws(self): + return self._initial_size==0 and (not self or str(self).isspace()) + + def part_count(self): + return super().__len__() |