parser: reject [ and ] in %option= values to prevent m4-quote injection#729
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parser: reject [ and ] in %option= values to prevent m4-quote injection#729MarkLee131 wants to merge 1 commit into
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The OPTION-state quoted-string rule at src/scan.l:480 accepts arbitrary non-quote, non-newline bytes, including [ and ]. Those values are later interpolated into m4 input as `m4_define([[NAME]],[[%s]])` in filter.c and main.c. A `]]` inside the value breaks out of m4's quoting and lets a .l file run arbitrary m4 builtins (m4_syscmd / m4_esyscmd / m4_include) during `flex foo.l`. PR westes#81 (7528bc0, 2016) added ESCAPED_QSTART / ESCAPED_QEND escaping for action and code-block contexts, but the same fix was never extended to %option= values. Only `prefix=` had a brackets-rejection guard. Apply the same guard to all eight %option= values that flow into m4: outfile, header-file, yydecl, yyclass, extra-type, pre-action, post-action, yyterminate. (prefix already had the check; the helper replaces the inline one.) Verified each value rejects [ and ] with a clear error message, and a normal .l file still builds.
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Fix #728:
The OPTION-state quoted-string rule at src/scan.l:480 accepts arbitrary non-quote, non-newline bytes, including [ and ]. Those values are later interpolated into m4 input as
m4_define([[NAME]],[[%s]])in filter.c and main.c. A]]inside the value breaks out of m4's quoting and lets a .l file run arbitrary m4 builtins (m4_syscmd / m4_esyscmd / m4_include) duringflex foo.l.PR #81 (7528bc0, 2016) added ESCAPED_QSTART / ESCAPED_QEND escaping for action and code-block contexts, but the same fix was never extended to %option= values. Only
prefix=had a brackets-rejection guard.Apply the same guard to all eight %option= values that flow into m4: outfile, header-file, yydecl, yyclass, extra-type, pre-action, post-action, yyterminate. (prefix already had the check; the helper replaces the inline one.)
Verified each value rejects [ and ] with a clear error message, and a normal .l file still builds.