gh-98188: Fix EmailMessage.get_payload to decode data when CTE value has extra text (GH-127547)
Up to this point message handling has been very strict with regards to content encoding values: mixed case was accepted, but trailing blanks or other text would cause decoding failure, even if the first token was a valid encoding. By Postel's Rule we should go ahead and decode as long as we can recognize that first token. We have not thought of any security or backward compatibility concerns with this fix.
This fix does introduce a new technique/pattern to the Message code: we look to see if the header has a 'cte' attribute, and if so we use that. This effectively promotes the header API exposed by HeaderRegistry to an API that any header parser "should" support. This seems like a reasonable thing to do. It is not, however, a requirement, as the string value of the header is still used if there is no cte attribute.
The full fix (ignore any trailing blanks or blank-separated trailing text) applies only to the non-compat32 API. compat32 is only fixed to the extent that it now ignores trailing spaces. Note that the HeaderRegistry parsing still records a HeaderDefect if there is extra text.
(cherry picked from commit a62ba52f14)
Co-authored-by: RanKKI <hliu86.me@gmail.com>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
* Fix for email.generator.Generator with whitespace between encoded words.
email.generator.Generator currently does not handle whitespace between
encoded words correctly when the encoded words span multiple lines. The
current generator will create an encoded word for each line. If the end
of the line happens to correspond with the end real word in the
plaintext, the generator will place an unencoded space at the start of
the subsequent lines to represent the whitespace between the plaintext
words.
A compliant decoder will strip all the whitespace from between two
encoded words which leads to missing spaces in the round-tripped
output.
The fix for this is to make sure that whitespace between two encoded
words ends up inside of one or the other of the encoded words. This
fix places the space inside of the second encoded word.
A second problem happens with continuation lines. A continuation line that
starts with whitespace and is followed by a non-encoded word is fine because
the newline between such continuation lines is defined as condensing to
a single space character. When the continuation line starts with whitespace
followed by an encoded word, however, the RFCs specify that the word is run
together with the encoded word on the previous line. This is because normal
words are filded on syntactic breaks by encoded words are not.
The solution to this is to add the whitespace to the start of the encoded word
on the continuation line.
Test cases are from GH-92081
* Rename a variable so it's not confused with the final variable.
(cherry picked from commit a6fdb31b67)
Co-authored-by: Toshio Kuratomi <a.badger@gmail.com>
It was raised if the charset itself contains characters not encodable
in UTF-8 (in particular \udcxx characters representing non-decodable
bytes in the source).
I am re-submitting an older PR which was abandoned but is still relevant, #10783 by @timb07.
The issue being solved () is still relevant. The original PR #10783 was closed as
the final request changes were not applied and since abandoned.
In this new PR I have re-used the original patch plus applied both comments from the review, by @maxking and @pganssle.
For reference, here is the original PR description:
In email.utils.parsedate_to_datetime(), a failure to parse the date, or invalid date components (such as hour outside 0..23) raises an exception. Document this behaviour, and add tests to test_email/test_utils.py to confirm this behaviour.
In email.headerregistry.DateHeader.parse(), check when parsedate_to_datetime() raises an exception and add a new defect InvalidDateDefect; preserve the invalid value as the string value of the header, but set the datetime attribute to None.
Add tests to test_email/test_headerregistry.py to confirm this behaviour; also added test to test_email/test_inversion.py to confirm emails with such defective date headers round trip successfully.
This pull request incorporates feedback gratefully received from @bitdancer, @brettcannon, @Mariatta and @warsaw, and replaces the earlier PR #2254.
Automerge-Triggered-By: GH:warsaw
* bpo-39040: Fix parsing of email headers with encoded-words inside a quoted string.
It is fairly common to find malformed mime headers (especially content-disposition
headers) where the parameter values, instead of being encoded to RFC
standards, are "encoded" by doing RFC 2047 "encoded word" encoding, and
then enclosing the whole thing in quotes. The processing of these malformed
headers was incorrectly leaving the spaces between encoded words in the decoded
text (whitespace between adjacent encoded words is supposed to be stripped on
decoding). This changeset fixes the encoded word processing inside quoted strings
(bare-quoted-string) to do correct RFC 2047 decoding by stripping that
whitespace.
Special characters in email address header display names are normally
put within double quotes. However, encoded words (=?charset?x?...?=) are
not allowed withing double quotes. When the header contains a word with
special characters and another word that must be encoded, the first one
must also be encoded.
In the next example, the display name in the From header is quoted and
therefore the comma is allowed; in the To header, the comma is not
within quotes and not encoded, which is not allowed and therefore
rejected by some mail servers.
From: "Foo Bar, France" <foo@example.com>
To: Foo Bar, =?utf-8?q?Espa=C3=B1a?= <foo@example.com>
https://bugs.python.org/issue37482
* bpo-21315: Fix parsing of encoded words with missing leading ws.
Because of missing leading whitespace, encoded word would get parsed as
unstructured token. This patch fixes that by looking for encoded words when
splitting tokens with whitespace.
Missing trailing whitespace around encoded word now register a defect
instead.
Original patch suggestion by David R. Murray on bpo-21315.
* bpo-35805: Add parser for Message-ID header.
This parser is based on the definition of Identification Fields from RFC 5322
Sec 3.6.4.
This should also prevent folding of Message-ID header using RFC 2047 encoded
words and hence fix bpo-35805.
* Prevent folding of non-ascii message-id headers.
* Add fold method to MsgID token to prevent folding.
The original algorithm tried to delegate the folding to the tokens so
that those tokens whose folding rules differed could specify the
differences. However, this resulted in a lot of duplicated code because
most of the rules were the same.
The new algorithm moves all folding logic into a set of functions
external to the token classes, but puts the information about which
tokens can be folded in which ways on the tokens...with the exception of
mime-parameters, which are a special case (which was not even
implemented in the old folder).
This algorithm can still probably be improved and hopefully simplified
somewhat.
Note that some of the test expectations are changed. I believe the
changes are toward more desirable and consistent behavior: in general
when (re) folding a line the canonical version of the tokens is
generated, rather than preserving errors or extra whitespace.
It is unlikely anyone is using the fact that the dictionary returned
by the 'params' attribute was previously writable, but even if someone
is the API is provisional so this kind of change is acceptable (and
needed, to get the API "right" before it becomes official).
Patch by Stéphane Wirtel.
This applies only to the new parser. The old parser decodes encoded words
inside quoted strings already, although it gets the whitespace wrong
when it does so.
This version of the patch only handles the most common case (a single encoded
word surrounded by quotes), but I haven't seen any other variations of this in
the wild yet, so its good enough for now.
This adds EmailMessage and, MIMEPart subclasses of Message
with new API methods, and a ContentManager class used by
the new methods. Also a new policy setting, content_manager.
Patch was reviewed by Stephen J. Turnbull and Serhiy Storchaka,
and reflects their feedback.
I will ideally add some examples of using the new API to the
documentation before the final release.
There is more to be done here in terms of accepting RFC invalid
input that some mailers accept, but this covers the valid
RFC places where encoded words can occur in structured headers.
The problem was I was only checking for decimal digits after the third '?',
not for *hex* digits :(.
This changeset also fixes a couple of comment typos, deletes an unused
function relating to encoded word parsing, and removed an invalid
'if' test from the folding function that was revealed by the tests
written to validate this issue.
This code passes all the same tests that the existing RFC mime header
parser passes, plus a bunch of additional ones.
There are a couple of commented out tests where there are issues with the
folding. The folding doesn't normally get invoked for headers parsed from
source, and the cases are marginal anyway (headers with invalid binary data)
so I'm not worried about them, but will fix them after the beta.
There are things that can be done to make this API even more convenient, but I
think this is a solid foundation worth having. And the parser is a full RFC
parser, so it handles cases that the current parser doesn't. (There are also
probably cases where it fails when the current parser doesn't, but I haven't
found them yet ;)
Oh, yeah, and there are some really ugly bits in the parser for handling some
'postel' cases that are unfortunately common.
I hope/plan to to eventually refactor a lot of the code in the parser which
should reduce the line count...but there is no escaping the fact that the
error recovery is welter of special cases.
When I made the checkin of the provisional email policy, I knew that
Address and Group needed to be made accessible from somewhere. The more
I looked at it, though, the more it became clear that since this is a
provisional API anyway, there's no good reason to hide headerregistry as
a private API. It was designed to ultimately be part of the public API,
and so it should be part of the provisional API.
This patch fully documents the headerregistry API, and deletes the
abbreviated version of those docs I had added to the provisional policy
docs.
Miss Islington (bot)