If the Content-Transfer-Encoding header field of a message part has trailing whitespace, for example "base64 ", get_payload(decode=True) does not return the properly decoded payload.
Here is a minimal code example. Sample message file attached.
import email
from email import policy
with open('msg.txt', 'rb') as f:
msg = email.message_from_binary_file(f, policy=policy.default)
parts = list(msg.walk())
parts[1].get_payload(decode=True)
> b'SGVsbG8uIFRlc3Rpbmc=\n'
The parsed content-transfer-encoding header "cte" value is truncated, but it's string value is not.
>>> header = parts[1].get('content-transfer-encoding')
>>> header.cte
'base64'
>>> str(header)
'base64 '
Which is what appears to be used in the decode attempt
https://github.com/python/cpython/blob/main/Lib/email/message.py#L289
- CPython versions tested on: 3.9.13, 3.10.7
- Operating system and architecture: macOS 12.6 Intel