Mario Fetka
50 lines
2.7 KiB
Markdown
50 lines
2.7 KiB
Markdown
# TLS policy
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Bongo offers TLS 1.3 and TLS 1.2 by default. Older protocol versions are only
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available on listeners whose explicit legacy-TLS option is enabled. Keep those
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listeners restricted to trusted legacy networks; do not expose them directly
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to the Internet.
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The SMTP delivery agent uses opportunistic STARTTLS. When a peer offers
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STARTTLS, `outbound_tls_verify` verifies its certificate chain against the
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system trust store and verifies the connected MX or configured LMTP host name.
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It defaults to `true`. Set it to `false` only for a peer whose certificate
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cannot yet be repaired.
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`outbound_tls_required` defaults to `false`, so delivery remains possible to
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SMTP servers which do not offer STARTTLS. Enabling it defers mail instead of
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sending plaintext. It is a global policy and should only be enabled when every
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configured destination is known to support TLS. A later policy layer may apply
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per-domain DANE or MTA-STS requirements.
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External-account collection and submission use libcurl and independently
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verify certificates and host names by default. See `external-accounts.md` for
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the credential and provider policy.
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Initial setup stores the default certificate and key as
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`/etc/bongo/ssl.d/server.crt` and `/etc/bongo/ssl.d/server.key`. The key is
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root-owned, group-readable by Bongo, and never world-readable. Setup creates a
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3072-bit RSA self-signed certificate only when no pair exists. A complete
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existing pair is parsed and checked for a matching key before reuse; unsafe,
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invalid, or incomplete material fails closed.
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The `bongoworker` ACME job implements RFC 8555 directly. It honors CA
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`Retry-After` limits and renewal information, writes candidate material first,
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validates the complete certificate/key pair, then deploys it atomically and
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signals the manager to reload TLS listeners. HTTP-01 is the default. DNS-01
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publishes `base64url(SHA-256(keyAuthorization))`, waits for the exact TXT value
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through ldns, and removes only the value created for that authorization.
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For DNS-01, `/etc/bongo/acme.d/providers` selects the longest matching zone.
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Use `type: "nsupdate"` for the native RFC 2136 adapter; `rfc2136` is an alias.
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No external `nsupdate` process is used. The adapter supports SOA-primary
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discovery, explicit IPv4/IPv6 or host-name servers, non-default ports, and
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TSIG HMAC algorithms. Delegated CNAME challenges use `match_zone`,
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`challenge_alias`, and the provider's target `zone`. Installed examples are
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in `/usr/share/bongo/examples/acme`.
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`bongo-admin migrate` moves the historical `osslcert.pem` and `osslpriv.pem`
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pair from the state database directory into `ssl.d` only when both files are
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present and the destination is empty. ACME deployments should atomically
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install a complete pair and reload or restart the affected Bongo agents.
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