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fix: suppress CIS noise #9061

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fix: suppress CIS noise #9061

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a3b8f1f
fix: suppress CIS noise
zachary-bailey Jul 28, 2026
7ecc68d
fix: rename function
zachary-bailey Jul 28, 2026
345f697
Merge branch 'main' into zb/CISSuppression
zachary-bailey Jul 29, 2026
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31 changes: 29 additions & 2 deletions vhdbuilder/packer/cis-report.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -56,8 +56,32 @@ pushd "$(dirname "$CISASSESSOR_TARBALL_PATH")" || exit 1

# Disable GuestConfig agent to avoid interference with CIS checks
systemctl disable --now gcd.service || true
# Fix permissions of log files
find /var/log -type f -exec chmod 640 {} \;

# Reset /var/log permissions to satisfy the CIS logfile-access control
# (6.1.3.1 / 6.1.4.1), which requires generic /var/log files to be 0640 or
# more restrictive.
reset_log_perms() {
find /var/log -type f -exec chmod 640 {} \;

@cameronmeissner cameronmeissner Jul 30, 2026

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should we explicitly use chmod 0640?

}

# A background writer (e.g. the GuestConfiguration extension writing
# CommandExecution.log, or periodic telemetry timers creating new event files)
# can reset a /var/log file to 0644 mid-scan, which intermittently flakes the
# logfile-access control. A single up-front chmod is not enough because the
# offending write can land during the ~13s assessor pass. Hold the permissions
# at 0640 for the entire assessment phase by resetting them in the background,
# then stop the guard before reading/uploading the reports.
reset_log_perms
( while :; do reset_log_perms; sleep 2; done ) &
PERMS_GUARD_PID=$!
stop_perms_guard() {
[ -n "${PERMS_GUARD_PID:-}" ] || return 0
kill "$PERMS_GUARD_PID" 2>/dev/null || true
wait "$PERMS_GUARD_PID" 2>/dev/null || true
PERMS_GUARD_PID=""
}
# Ensure the guard is reaped even if the assessor exits non-zero under set -e.
trap stop_perms_guard EXIT

tar xzf "$CISASSESSOR_TARBALL_PATH"

Expand Down Expand Up @@ -87,6 +111,9 @@ if [ -z "$L2_HTML_REPORT" ] || [ ! -f "$L2_HTML_REPORT" ]; then
exit 1
fi

# Assessment is complete; stop holding /var/log permissions before uploads.
stop_perms_guard

# Upload reports to storage account
az storage blob upload --container-name "$SIG_CONTAINER_NAME" --file "$L1_TXT_REPORT" --name "$CIS_REPORT_L1_TXT_NAME" --account-name "$STORAGE_ACCOUNT_NAME" --auth-mode login
az storage blob upload --container-name "$SIG_CONTAINER_NAME" --file "$L2_TXT_REPORT" --name "$CIS_REPORT_L2_TXT_NAME" --account-name "$STORAGE_ACCOUNT_NAME" --auth-mode login
Expand Down
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