gh-143921: Narrow the control character check in imaplib commands#153067
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Only NUL, CR and LF are rejected now. Other control characters are valid in quoted strings and can occur in mailbox names returned by the server, so they are now accepted and sent quoted. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 3.15. |
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GH-153135 is a backport of this pull request to the 3.15 branch. |
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…nds (GH-153067) (GH-153135) Only NUL, CR and LF are rejected now. Other control characters are valid in quoted strings and can occur in mailbox names returned by the server, so they are now accepted and sent quoted. (cherry picked from commit d0921ef) Co-authored-by: Serhiy Storchaka <storchaka@gmail.com> Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
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The broad check rejected all of 0x00-0x1F and 0x7F, but only NUL, CR and LF are actually unsafe (command injection / binary truncation).
TAB and other control characters are valid QUOTED-CHARs per RFC 3501 and RFC 9051, and a mailbox name containing them can be returned by the server via LIST, so the client must be able to send it back in SELECT, STATUS, etc. Rejecting such names made imaplib unable to operate on a folder that legitimately exists.
Now that GH-152703 restored argument quoting, such arguments are sent as quoted strings; only NUL, CR and LF (which cannot be represented even in a quoted string) are still rejected.
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