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fix(security): restrict node secret file perms and avoid logging AD realm password - #9776
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Calvin S. (calvin197) wants to merge 1 commit into
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…ealm password Addresses Mythos findings tracked under ADO 37518878: - 37518906/911/915: bootstrap-kubeconfig embeds the TLS bootstrap token but was written world-readable (chmod 0644). Restrict to 0600 so unprivileged local users can't read the token. - 37518920/916: the kubelet client private key (/etc/kubernetes/certs/client.key) was written with no explicit mode (umask-dependent, typically 0644). touch + chmod 0600 before writing so it's never world-readable. - 37518908: setup-custom-search-domains.sh runs under `set -x`, echoing the AD realm join password into provisioning logs. Wrap the realm join in `set +x` / `set -x`. Verified: go test ./pkg/agent/... and aks-node-controller ./parser/... pass; bash -n on all three scripts; no ShellSpec assertions reference the changed lines. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 350c2577-7031-4d0d-adc1-e99d053fc981
Calvin S. (calvin197)
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Windows Unit Test Results 3 files 18 suites 1m 24s ⏱️ Results for commit 5d3b920. |
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🟡 Changes recommended
Restoring tracing masks realm-join failures, and the new security invariants lack required ShellSpec coverage.
3 open findings
What changed in this PR
Hardens Linux node provisioning against secret exposure.
Changes:
- Restricts kubelet private key and bootstrap kubeconfig permissions.
- Suppresses tracing while passing the AD realm password.
| File | Description |
|---|---|
setup-custom-search-domains.sh |
Disables tracing around realm join. |
cse_config.sh |
Sets client key permissions to 0600. |
cse_config_kubelet.sh |
Sets bootstrap kubeconfig permissions to 0600. |
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| # disable command tracing so the realm password isn't written to provisioning logs | ||
| set +x | ||
| echo "${CUSTOM_SEARCH_REALM_PASSWORD}" | realm join -U ${CUSTOM_SEARCH_REALM_USER}@$(echo "${CUSTOM_SEARCH_DOMAIN_NAME}" | tr /a-z/ /A-Z/) $(echo "${CUSTOM_SEARCH_DOMAIN_NAME}" | tr /a-z/ /A-Z/) | ||
| set -x |
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| # client.key is the kubelet client private key; restrict to root before writing | ||
| touch /etc/kubernetes/certs/client.key | ||
| chmod 0600 /etc/kubernetes/certs/client.key |
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| # bootstrap-kubeconfig embeds the TLS bootstrap token; restrict to root only | ||
| chmod 0600 "${BOOTSTRAP_KUBECONFIG_FILE}" |
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| touch "${BOOTSTRAP_KUBECONFIG_FILE}" | ||
| chmod 0644 "${BOOTSTRAP_KUBECONFIG_FILE}" | ||
| # bootstrap-kubeconfig embeds the TLS bootstrap token; restrict to root only | ||
| chmod 0600 "${BOOTSTRAP_KUBECONFIG_FILE}" |
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Calvin S. (@calvin197) you can drop this change, addressing it here: #9797
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What this PR does / why we need it:
Hardens three node-provisioning scripts so secrets aren't exposed via file permissions or provisioning logs. Addresses Mythos security findings (tracked under ADO 37518878):
• bootstrap-kubeconfig (ADO 37518906/911/915) — /var/lib/kubelet/bootstrap-kubeconfig embeds the TLS bootstrap token but was written world-readable ( chmod 0644 ). Tightened to chmod 0600 so unprivileged local users can't read the token.
• kubelet client key (ADO 37518920/916) — /etc/kubernetes/certs/client.key (kubelet client private key) was written with no explicit mode (umask-dependent, typically 0644). Now touch + chmod 0600 before writing, so there's never a world-readable window.
• AD realm password in logs (ADO 37518908) — setup-custom-search-domains.sh runs under set -x , which echoed the AD realm-join password into provisioning logs. Wrapped the realm join in set +x / set -x .
No functional behavior change — only file modes and log-tracing scope. Validated with go test ./pkg/agent/... and aks-node-controller ./parser/... (both pass), bash -n on all three scripts, and confirmed no ShellSpec assertions reference the changed lines.
Which issue(s) this PR fixes:
Fixes #