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| author | Paul Barker <paul@pbarker.dev> | 2021-06-07 11:02:51 +0100 |
|---|---|---|
| committer | Konstantin Ryabitsev <konstantin@linuxfoundation.org> | 2021-06-07 08:49:23 -0400 |
| commit | 366bcd1fd8a10b6125e591f0c35cc85b10c9c950 (patch) | |
| tree | 182506f7ad4dbf44584802642ad1bf6aa39efbf7 | |
| parent | a727eaeb9a7183262659b8192fc823e409bba49a (diff) | |
| download | b4-366bcd1fd8a10b6125e591f0c35cc85b10c9c950.tar.gz | |
Handle MIME encoded-word in DKIM-Signature headers
As recently found in patatt [1], mail gateways and archivers may mangle
headers like DKIM-Signature if they are sent as an excessively long
line. An example of this occuring was found when the DKIM-Signature
header generated by Microsoft Office 365 collided with the
header re-encoding performed by lists.sr.ht when generating mbox
archive files. This encoding causes dkim.verify() to fail.
The Python email.header module provides the decode_header() and
make_header() functions which can be used to handle MIME encoded-word
syntax or other header manglings which may occur. Fixing up the header
content using these functions before calling dkim.verify() allows the
verification to succeed.
[1]: https://lore.kernel.org/tools/20210531140539.7630-1-paul@pbarker.dev/
Signed-off-by: Paul Barker <paul@pbarker.dev>
Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Link: https://lore.kernel.org/r/20210607100252.8253-2-paul@pbarker.dev
| -rw-r--r-- | b4/__init__.py | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/b4/__init__.py b/b4/__init__.py index a163364..168b722 100644 --- a/b4/__init__.py +++ b/b4/__init__.py @@ -1006,6 +1006,10 @@ class LoreMessage: seenatts = list() for hn, hval in dkhdrs: + # Handle MIME encoded-word syntax or other types of header encoding if + # present. + if '?q?' in hval: + hval = str(email.header.make_header(email.header.decode_header(hval))) errors = list() hdata = LoreMessage.get_parts_from_header(hval) logger.debug('Loading DKIM attestation for d=%s, s=%s', hdata['d'], hdata['s']) |