auth: fixes for SA 2026-07

[miodvallat]

Short description

Fixes for PowerDNS Security Advisory 2026-07 (to be published later today)

CVE-2026-42005

Checklist

I have:

• read the CONTRIBUTING.md document
• read and accepted the Developer Certificate of Origin document, including the AI Policy, and added a "Signed-off-by" to my commits
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[coveralls]

Coverage Report for CI Build 28149789053

Coverage decreased (-0.003%) to 71.081%

Details

• Coverage decreased (-0.003%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 75 coverage regressions across 16 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

75 previously-covered lines in 16 files lost coverage.

Top 10 Files by Coverage Loss	Lines Losing Coverage	Coverage
pdns/recursordist/test-syncres_cc1.cc	13	79.9%
pdns/recursordist/syncres.cc	8	81.27%
pdns/dnsdistdist/dnsdist-tcp.cc	7	74.82%
pdns/recursordist/lwres.cc	6	67.69%
pdns/remote_logger.cc	6	60.96%
pdns/signingpipe.cc	6	84.46%
pdns/dnsdistdist/dnsdist-concurrent-connections.cc	4	90.65%
pdns/recursordist/rec-taskqueue.cc	4	40.34%
pdns/iputils.cc	3	60.33%
pdns/misc.cc	3	61.78%

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Coverage Stats

Relevant Lines:	171270
Covered Lines:	133425
Line Coverage:	77.9%
Relevant Branches:	81856
Covered Branches:	46500
Branch Coverage:	56.81%
Branches in Coverage %:	Yes
Coverage Strength:	5925491.93 hits per line

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💛 - Coveralls