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Title: email: encoded headers lose their quoting when refolded
Type: behavior Stage:
Components: Library (Lib) Versions: Python 3.9
Status: open Resolution:
Dependencies: Superseder:
Assigned To: Nosy List: Emil.Styrke, barry, maxking, r.david.murray
Priority: normal Keywords:

Created on 2021-03-19 09:45 by Emil.Styrke, last changed 2022-04-11 14:59 by admin.

File name Uploaded Description Edit Emil.Styrke, 2021-03-19 09:45 unittest displaying the issue
Messages (1)
msg389061 - (view) Author: Emil Styrke (Emil.Styrke) Date: 2021-03-19 09:45
When a header with an encoded (QP or Base64) display_name is refolded, it may lose (some of) its encoding.  If it then contains illegal "atext" tokens, an invalid header will result.

For example, `From: =?utf-8?Q?a=2C=20123456789012345678901234567890123456?= <>` will become `From: a, 123456789012345678901234567890123456 <>`  This contains a comma character which needs to be quoted: correct rendering would be `From: "a, 123456789012345678901234567890123456" <>`. Note that this example isn't even folded to multiple lines, since the decoded text is short enough to fit in one line.

This can be triggered by `BytesParser(policy=policy.default).parsebytes("From: =?utf-8?Q?a=2C=20123456789012345678901234567890123456?= <>").as_bytes()`, but the offending code seems to be in or below `email.policy.EmailPolicy.fold`.  See attached file for examples with and without folding.
Date User Action Args
2022-04-11 14:59:43adminsetgithub: 87720
2021-03-19 18:30:12shihai1991setnosy: + barry, r.david.murray, maxking
2021-03-19 09:45:02Emil.Styrkecreate