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alsd4git merged 2 commits into from
Oct 30, 2026
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docs(security): explain certificate lifecycle and trust boundaries #3

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docs(security): 📝 explain certificate lifecycle and trust boundaries
alsd4git Oct 30, 2026
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docs(security): 📝 distinguish local key generation from CA signing
alsd4git Oct 30, 2026
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44 changes: 38 additions & 6 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -35,14 +35,46 @@ unless you explicitly enable `INCLUDE_RAW_KEY_IN_ZIP=true`. Treat both the ZIP
and its password as sensitive.

```mermaid
flowchart LR
A[Local Smallstep CA] -->|issue| B[Client identity]
B --> C[PEM certificate and key]
B --> D[PKCS#12 bundle]
D --> E[Optional ZIP for transfer]
flowchart TD
subgraph Local[Private operator machine]
CA["Smallstep CA: private state in ./step"]
CERT["Public PEM client certificate"]
KEY["Secret client private key: generated locally by step CLI"]
CSV["issued_passwords.csv: plaintext passwords, mode 0600"]
P12["Password-protected PKCS#12: certificate + private key"]
ZIP["ZIP: protected PKCS#12 + public CA/client certificates"]
CA -->|sign or renew certificate| CERT
CERT -->|package| P12
KEY -->|package locally| P12
CSV -->|password for packaging| P12
P12 --> ZIP
end
ZIP -->|optional serve-certs.sh| HTTP["Temporary HTTP download: trusted LAN only"]
HTTP --> CLIENT["Client imports PKCS#12 using its password"]
ZIP -->|operator-managed secure transfer| CLIENT
CLIENT -->|presents client certificate over TLS| SERVICE["Service validates certificate against trusted CA"]
CA -.->|revoke prevents future renewal| REVOKED["Revoked certificate"]
REVOKED -.->|early rejection requires service-side CRL/OCSP checks| SERVICE
```

This diagram shows the local packaging workflow. The default Compose deployment
In text: the `step` CLI generates the client private key on the operator's
machine and requests a signed public certificate from the CA. The CA does not
receive or generate the client private key.
`cert-manager.sh renew CLIENT_NAME` renews the certificate in place and rebuilds
the PKCS#12 and ZIP using the latest password in the local plaintext log.
The ZIP is not itself encrypted: its PKCS#12 is password-protected. Deliver the
bundle and password through trusted channels chosen by the operator; the scripts
do not arrange a separate secure password-delivery channel. Importing the bundle
does not configure a server: the relying service must trust the CA and enforce
client-certificate validation.

The optional HTTP download is temporary but not authenticated or encrypted.
It exposes the selected ZIP to anyone who can reach the listener while it runs.
Do not expose it to the Internet or use it to serve CA state, PEM private keys,
or the password log. See the [security model](#security-model) and the
[Nginx Proxy Manager integration guide](docs/nginx-proxy-manager.md).

Revocation is not an automatic disconnect mechanism. The default Compose deployment
does not configure active revocation checking or a CRL endpoint, and open-source
step-ca does not provide OCSP. Do not assume that revoking a certificate makes
an already issued certificate unusable at relying services before expiry.
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