mirror of https://github.com/python/cpython
514 lines
21 KiB
Python
514 lines
21 KiB
Python
# Copyright (C) 2002 Python Software Foundation
|
||
# Author: che@debian.org (Ben Gertzfield), barry@zope.com (Barry Warsaw)
|
||
|
||
"""Header encoding and decoding functionality."""
|
||
|
||
import re
|
||
import binascii
|
||
from types import StringType, UnicodeType
|
||
|
||
import email.quopriMIME
|
||
import email.base64MIME
|
||
from email.Errors import HeaderParseError
|
||
from email.Charset import Charset
|
||
|
||
try:
|
||
from email._compat22 import _floordiv
|
||
except SyntaxError:
|
||
# Python 2.1 spells integer division differently
|
||
from email._compat21 import _floordiv
|
||
|
||
try:
|
||
True, False
|
||
except NameError:
|
||
True = 1
|
||
False = 0
|
||
|
||
CRLFSPACE = '\r\n '
|
||
CRLF = '\r\n'
|
||
NL = '\n'
|
||
SPACE = ' '
|
||
USPACE = u' '
|
||
SPACE8 = ' ' * 8
|
||
EMPTYSTRING = ''
|
||
UEMPTYSTRING = u''
|
||
|
||
MAXLINELEN = 76
|
||
|
||
ENCODE = 1
|
||
DECODE = 2
|
||
|
||
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)
|
||
|
||
pcre = re.compile('([,;])')
|
||
|
||
# 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]+:$')
|
||
|
||
|
||
|
||
# Helpers
|
||
_max_append = email.quopriMIME._max_append
|
||
|
||
|
||
|
||
def decode_header(header):
|
||
"""Decode a message header value without converting charset.
|
||
|
||
Returns a list of (decoded_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.
|
||
|
||
An email.Errors.HeaderParseError may be raised when certain decoding error
|
||
occurs (e.g. a base64 decoding exception).
|
||
"""
|
||
# If no encoding, just return the header
|
||
header = str(header)
|
||
if not ecre.search(header):
|
||
return [(header, None)]
|
||
decoded = []
|
||
dec = ''
|
||
for line in header.splitlines():
|
||
# This line might not have an encoding in it
|
||
if not ecre.search(line):
|
||
decoded.append((line, None))
|
||
continue
|
||
parts = ecre.split(line)
|
||
while parts:
|
||
unenc = parts.pop(0).strip()
|
||
if unenc:
|
||
# Should we continue a long line?
|
||
if decoded and decoded[-1][1] is None:
|
||
decoded[-1] = (decoded[-1][0] + SPACE + unenc, None)
|
||
else:
|
||
decoded.append((unenc, None))
|
||
if parts:
|
||
charset, encoding = [s.lower() for s in parts[0:2]]
|
||
encoded = parts[2]
|
||
dec = None
|
||
if encoding == 'q':
|
||
dec = email.quopriMIME.header_decode(encoded)
|
||
elif encoding == 'b':
|
||
try:
|
||
dec = email.base64MIME.decode(encoded)
|
||
except binascii.Error:
|
||
# Turn this into a higher level exception. BAW: Right
|
||
# now we throw the lower level exception away but
|
||
# when/if we get exception chaining, we'll preserve it.
|
||
raise HeaderParseError
|
||
if dec is None:
|
||
dec = encoded
|
||
|
||
if decoded and decoded[-1][1] == charset:
|
||
decoded[-1] = (decoded[-1][0] + dec, decoded[-1][1])
|
||
else:
|
||
decoded.append((dec, charset))
|
||
del parts[0:3]
|
||
return decoded
|
||
|
||
|
||
|
||
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 explicit 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 76.
|
||
|
||
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
|
||
if not isinstance(charset, Charset):
|
||
charset = Charset(charset)
|
||
self._charset = charset
|
||
self._continuation_ws = continuation_ws
|
||
cws_expanded_len = len(continuation_ws.replace('\t', SPACE8))
|
||
# BAW: I believe `chunks' and `maxlinelen' should be non-public.
|
||
self._chunks = []
|
||
if s is not None:
|
||
self.append(s, charset, errors)
|
||
if maxlinelen is None:
|
||
maxlinelen = MAXLINELEN
|
||
if header_name is None:
|
||
# We don't know anything about the field header so the first line
|
||
# is the same length as subsequent lines.
|
||
self._firstlinelen = maxlinelen
|
||
else:
|
||
# The first line should be shorter to take into account the field
|
||
# header. Also subtract off 2 extra for the colon and space.
|
||
self._firstlinelen = maxlinelen - len(header_name) - 2
|
||
# Second and subsequent lines should subtract off the length in
|
||
# columns of the continuation whitespace prefix.
|
||
self._maxlinelen = maxlinelen - cws_expanded_len
|
||
|
||
def __str__(self):
|
||
"""A synonym for self.encode()."""
|
||
return self.encode()
|
||
|
||
def __unicode__(self):
|
||
"""Helper for the built-in unicode function."""
|
||
uchunks = []
|
||
lastcs = None
|
||
for s, 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.
|
||
nextcs = charset
|
||
if uchunks:
|
||
if lastcs is not None:
|
||
if nextcs is None or nextcs == 'us-ascii':
|
||
uchunks.append(USPACE)
|
||
nextcs = None
|
||
elif nextcs is not None and nextcs <> 'us-ascii':
|
||
uchunks.append(USPACE)
|
||
lastcs = nextcs
|
||
uchunks.append(unicode(s, str(charset)))
|
||
return UEMPTYSTRING.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 string, swap the args and do another comparison.
|
||
return other == self.encode()
|
||
|
||
def __ne__(self, other):
|
||
return not self == other
|
||
|
||
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, StringType) is true), 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 this case, when producing an RFC 2822 compliant header
|
||
using RFC 2047 rules, the Unicode string will be encoded using the
|
||
following charsets in order: us-ascii, the charset hint, utf-8. The
|
||
first character set not to provoke a UnicodeError is used.
|
||
|
||
Optional `errors' is passed as the third argument to any unicode() or
|
||
ustr.encode() call.
|
||
"""
|
||
if charset is None:
|
||
charset = self._charset
|
||
elif not isinstance(charset, Charset):
|
||
charset = Charset(charset)
|
||
# If the charset is our faux 8bit charset, leave the string unchanged
|
||
if charset <> '8bit':
|
||
# We need to test that the string can be converted to unicode and
|
||
# back to a byte string, given the input and output codecs of the
|
||
# charset.
|
||
if isinstance(s, StringType):
|
||
# Possibly raise UnicodeError if the byte string can't be
|
||
# converted to a unicode with the input codec of the charset.
|
||
incodec = charset.input_codec or 'us-ascii'
|
||
ustr = unicode(s, incodec, errors)
|
||
# Now make sure that the unicode could be converted back to a
|
||
# byte string with the output codec, which may be different
|
||
# than the iput coded. Still, use the original byte string.
|
||
outcodec = charset.output_codec or 'us-ascii'
|
||
ustr.encode(outcodec, errors)
|
||
elif isinstance(s, UnicodeType):
|
||
# Now we have to be sure the unicode string can be converted
|
||
# to a byte string with a reasonable output codec. We want to
|
||
# use the byte string in the chunk.
|
||
for charset in USASCII, charset, UTF8:
|
||
try:
|
||
outcodec = charset.output_codec or 'us-ascii'
|
||
s = s.encode(outcodec, errors)
|
||
break
|
||
except UnicodeError:
|
||
pass
|
||
else:
|
||
assert False, 'utf-8 conversion failed'
|
||
self._chunks.append((s, charset))
|
||
|
||
def _split(self, s, charset, maxlinelen, splitchars):
|
||
# Split up a header safely for use with encode_chunks.
|
||
splittable = charset.to_splittable(s)
|
||
encoded = charset.from_splittable(splittable, True)
|
||
elen = charset.encoded_header_len(encoded)
|
||
# If the line's encoded length first, just return it
|
||
if elen <= maxlinelen:
|
||
return [(encoded, charset)]
|
||
# If we have undetermined raw 8bit characters sitting in a byte
|
||
# string, we really don't know what the right thing to do is. We
|
||
# can't really split it because it might be multibyte data which we
|
||
# could break if we split it between pairs. The least harm seems to
|
||
# be to not split the header at all, but that means they could go out
|
||
# longer than maxlinelen.
|
||
if charset == '8bit':
|
||
return [(s, charset)]
|
||
# BAW: I'm not sure what the right test here is. What we're trying to
|
||
# do is be faithful to RFC 2822's recommendation that ($2.2.3):
|
||
#
|
||
# "Note: Though structured field bodies are defined in such a way that
|
||
# folding can take place between many of the lexical tokens (and even
|
||
# within some of the lexical tokens), folding SHOULD be limited to
|
||
# placing the CRLF at higher-level syntactic breaks."
|
||
#
|
||
# For now, I can only imagine doing this when the charset is us-ascii,
|
||
# although it's possible that other charsets may also benefit from the
|
||
# higher-level syntactic breaks.
|
||
elif charset == 'us-ascii':
|
||
return self._split_ascii(s, charset, maxlinelen, splitchars)
|
||
# BAW: should we use encoded?
|
||
elif elen == len(s):
|
||
# We can split on _maxlinelen boundaries because we know that the
|
||
# encoding won't change the size of the string
|
||
splitpnt = maxlinelen
|
||
first = charset.from_splittable(splittable[:splitpnt], False)
|
||
last = charset.from_splittable(splittable[splitpnt:], False)
|
||
else:
|
||
# Binary search for split point
|
||
first, last = _binsplit(splittable, charset, maxlinelen)
|
||
# first is of the proper length so just wrap it in the appropriate
|
||
# chrome. last must be recursively split.
|
||
fsplittable = charset.to_splittable(first)
|
||
fencoded = charset.from_splittable(fsplittable, True)
|
||
chunk = [(fencoded, charset)]
|
||
return chunk + self._split(last, charset, self._maxlinelen, splitchars)
|
||
|
||
def _split_ascii(self, s, charset, firstlen, splitchars):
|
||
chunks = _split_ascii(s, firstlen, self._maxlinelen,
|
||
self._continuation_ws, splitchars)
|
||
return zip(chunks, [charset]*len(chunks))
|
||
|
||
def _encode_chunks(self, newchunks, maxlinelen):
|
||
# MIME-encode a header with many different charsets and/or encodings.
|
||
#
|
||
# Given a list of pairs (string, charset), return a MIME-encoded
|
||
# string suitable for use in a header field. Each pair may have
|
||
# different charsets and/or encodings, and the resulting header will
|
||
# accurately reflect each setting.
|
||
#
|
||
# Each encoding can be email.Utils.QP (quoted-printable, for
|
||
# ASCII-like character sets like iso-8859-1), email.Utils.BASE64
|
||
# (Base64, for non-ASCII like character sets like KOI8-R and
|
||
# iso-2022-jp), or None (no encoding).
|
||
#
|
||
# Each pair will be represented on a separate line; the resulting
|
||
# string will be in the format:
|
||
#
|
||
# =?charset1?q?Mar=EDa_Gonz=E1lez_Alonso?=\n
|
||
# =?charset2?b?SvxyZ2VuIEL2aW5n?="
|
||
chunks = []
|
||
for header, charset in newchunks:
|
||
if charset is None or charset.header_encoding is None:
|
||
s = header
|
||
else:
|
||
s = charset.header_encode(header)
|
||
# Don't add more folding whitespace than necessary
|
||
if chunks and chunks[-1].endswith(' '):
|
||
extra = ''
|
||
else:
|
||
extra = ' '
|
||
_max_append(chunks, s, maxlinelen, extra)
|
||
joiner = NL + self._continuation_ws
|
||
return joiner.join(chunks)
|
||
|
||
def encode(self, splitchars=';, '):
|
||
"""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.
|
||
|
||
This method will do its best to convert the string to the correct
|
||
character set used in email, and encode and line wrap it safely with
|
||
the appropriate scheme for that character set.
|
||
|
||
If the given charset is not known or an error occurs during
|
||
conversion, this function will return the header untouched.
|
||
|
||
Optional splitchars is a string containing characters to split long
|
||
ASCII lines on, in rough support of RFC 2822's `highest level
|
||
syntactic breaks'. This doesn't affect RFC 2047 encoded lines.
|
||
"""
|
||
newchunks = []
|
||
maxlinelen = self._firstlinelen
|
||
lastlen = 0
|
||
for s, charset in self._chunks:
|
||
# The first bit of the next chunk should be just long enough to
|
||
# fill the next line. Don't forget the space separating the
|
||
# encoded words.
|
||
targetlen = maxlinelen - lastlen - 1
|
||
if targetlen < charset.encoded_header_len(''):
|
||
# Stick it on the next line
|
||
targetlen = maxlinelen
|
||
newchunks += self._split(s, charset, targetlen, splitchars)
|
||
lastchunk, lastcharset = newchunks[-1]
|
||
lastlen = lastcharset.encoded_header_len(lastchunk)
|
||
return self._encode_chunks(newchunks, maxlinelen)
|
||
|
||
|
||
|
||
def _split_ascii(s, firstlen, restlen, continuation_ws, splitchars):
|
||
lines = []
|
||
maxlen = firstlen
|
||
for line in s.splitlines():
|
||
# Ignore any leading whitespace (i.e. continuation whitespace) already
|
||
# on the line, since we'll be adding our own.
|
||
line = line.lstrip()
|
||
if len(line) < maxlen:
|
||
lines.append(line)
|
||
maxlen = restlen
|
||
continue
|
||
# Attempt to split the line 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.
|
||
for ch in splitchars:
|
||
if line.find(ch) >= 0:
|
||
break
|
||
else:
|
||
# There's nothing useful to split the line on, not even spaces, so
|
||
# just append this line unchanged
|
||
lines.append(line)
|
||
maxlen = restlen
|
||
continue
|
||
# Now split the line on the character plus trailing whitespace
|
||
cre = re.compile(r'%s\s*' % ch)
|
||
if ch in ';,':
|
||
eol = ch
|
||
else:
|
||
eol = ''
|
||
joiner = eol + ' '
|
||
joinlen = len(joiner)
|
||
wslen = len(continuation_ws.replace('\t', SPACE8))
|
||
this = []
|
||
linelen = 0
|
||
for part in cre.split(line):
|
||
curlen = linelen + max(0, len(this)-1) * joinlen
|
||
partlen = len(part)
|
||
onfirstline = not lines
|
||
# We don't want to split after the field name, if we're on the
|
||
# first line and the field name is present in the header string.
|
||
if ch == ' ' and onfirstline and \
|
||
len(this) == 1 and fcre.match(this[0]):
|
||
this.append(part)
|
||
linelen += partlen
|
||
elif curlen + partlen > maxlen:
|
||
if this:
|
||
lines.append(joiner.join(this) + eol)
|
||
# If this part is longer than maxlen and we aren't already
|
||
# splitting on whitespace, try to recursively split this line
|
||
# on whitespace.
|
||
if partlen > maxlen and ch <> ' ':
|
||
subl = _split_ascii(part, maxlen, restlen,
|
||
continuation_ws, ' ')
|
||
lines.extend(subl[:-1])
|
||
this = [subl[-1]]
|
||
else:
|
||
this = [part]
|
||
linelen = wslen + len(this[-1])
|
||
maxlen = restlen
|
||
else:
|
||
this.append(part)
|
||
linelen += partlen
|
||
# Put any left over parts on a line by themselves
|
||
if this:
|
||
lines.append(joiner.join(this))
|
||
return lines
|
||
|
||
|
||
|
||
def _binsplit(splittable, charset, maxlinelen):
|
||
i = 0
|
||
j = len(splittable)
|
||
while i < j:
|
||
# Invariants:
|
||
# 1. splittable[:k] fits for all k <= i (note that we *assume*,
|
||
# at the start, that splittable[:0] fits).
|
||
# 2. splittable[:k] does not fit for any k > j (at the start,
|
||
# this means we shouldn't look at any k > len(splittable)).
|
||
# 3. We don't know about splittable[:k] for k in i+1..j.
|
||
# 4. We want to set i to the largest k that fits, with i <= k <= j.
|
||
#
|
||
m = (i+j+1) >> 1 # ceiling((i+j)/2); i < m <= j
|
||
chunk = charset.from_splittable(splittable[:m], True)
|
||
chunklen = charset.encoded_header_len(chunk)
|
||
if chunklen <= maxlinelen:
|
||
# m is acceptable, so is a new lower bound.
|
||
i = m
|
||
else:
|
||
# m is not acceptable, so final i must be < m.
|
||
j = m - 1
|
||
# i == j. Invariant #1 implies that splittable[:i] fits, and
|
||
# invariant #2 implies that splittable[:i+1] does not fit, so i
|
||
# is what we're looking for.
|
||
first = charset.from_splittable(splittable[:i], False)
|
||
last = charset.from_splittable(splittable[i:], False)
|
||
return first, last
|