Warn when a groups filter matches no users - #398
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A groups pattern-list made up entirely of negated patterns matches no
user, so the filter never selects anyone. Detect this at config load in
both login_duo and pam_duo and log a warning, since the more likely
intent is to require Duo for everyone except a group ("*,!group").
Adds unit coverage for the subpattern cases and login_duo integration
tests for the warn/no-warn paths, plus a note in both man pages'
PATTERNS sections.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
jeffreyparker
approved these changes
Jul 23, 2026
A comma-separated groups pattern-list may contain empty subpatterns from a leading, trailing, or doubled comma (e.g. ",!wheel" or "!wheel,,!admin"). An empty subpattern matches no group, so such a list still matches no user. duo_groups_all_negated() previously stopped at the first non-'!' character and so returned false for these lists, suppressing the warning. Skip empty subpatterns instead of treating them as a positive match, and cover both forms with regression tests. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
jeffreyparker
approved these changes
Jul 23, 2026
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Summary of the change
A groups pattern-list made up entirely of negated patterns matches no user, so the filter never selects anyone. Detect this at config load in both login_duo and pam_duo and log a warning, since the more likely intent is to require Duo for everyone except a group ("*,!group").
Adds unit coverage for the subpattern cases and login_duo integration tests for the warn/no-warn paths, plus a note in both man pages' PATTERNS sections.
Test Plan
New and existing tests pass