gh-128110: Fix rfc2047 handling in email parser address headers #130749
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RFC 2047 Section 6.2 requires that "any 'linear-white-space' that separates a pair of adjacent 'encoded-word's is ignored." The modern header value parser correctly implements that for unstructured headers, but had missed a case in structured headers. This could cause a parsed address header to include extraneous spaces in a display-name. Fixed in get_atom() by converting a trailing CFWSList token after an encoded-word to an EWWhiteSpaceTerminal if another encoded-word follows. Deliberately left similar code in get_dotatom() unmodified. A dotatom can only appear within an addr-spec. RFC 2047 Section 5 prohibits use of an encoded-word in any portion of an addr-spec, so its appearance in a dotatom is invalid. Adding (and testing) special white-space handling in an invalid dotatom seems an unnecessary complication.
caje731
approved these changes
Mar 12, 2025
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RFC 2047 Section 6.2 requires that "any 'linear-white-space' that separates a pair of adjacent 'encoded-word's is ignored." The modern header value parser correctly implements that for unstructured headers, but had missed a case in structured headers. This could cause a parsed address header to include extraneous spaces in a display-name.
Fixed in get_atom() by converting a trailing CFWSList token after an encoded-word to an EWWhiteSpaceTerminal if another encoded-word follows.
Deliberately left similar code in get_dotatom() unmodified. A dotatom can only appear within an addr-spec. RFC 2047 Section 5 prohibits use of an encoded-word in any portion of an addr-spec, so its appearance in a dotatom is invalid. Adding (and testing) special white-space handling in an invalid dotatom seems an unnecessary complication.
Fixes gh-128110
Suggest label: topic-email