128 lines
6 KiB
Markdown
128 lines
6 KiB
Markdown
# checker-openpgpkey
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DANE-Email posture checker for happyDomain.
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Runs a comprehensive testsuite on a domain's DNS-published OpenPGP key
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(`OPENPGPKEY`, [RFC 7929][rfc7929]) or S/MIME certificate (`SMIMEA`,
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[RFC 8162][rfc8162]) and renders an actionable HTML report whose top
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block nudges the user toward the fix for the most common failure
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scenarios.
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This checker binds to the happyDomain services:
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- `abstract.OpenPGP`: individual user's PGP key, owner-hashed below
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`._openpgpkey.<zone>`.
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- `abstract.SMimeCert`: user's S/MIME certificate, owner-hashed below
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`._smimecert.<zone>`.
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[rfc7929]: https://www.rfc-editor.org/rfc/rfc7929
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[rfc8162]: https://www.rfc-editor.org/rfc/rfc8162
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## Tests run
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All findings are tagged by severity (`info` / `warn` / `crit`) so the
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rule engine can fold them into a single `CheckState`.
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### DNS (both record types)
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| Code | Severity | What it catches |
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| --- | --- | --- |
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| `dns_query_failed` | crit | The resolver returned an error or did not answer. |
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| `dns_no_record` | crit | The authoritative answer has no record at the expected owner. |
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| `dnssec_not_validated` | crit / warn | The validating resolver did not set `AD`. RFC 7929/8162 mandate DNSSEC; the severity is configurable via `requireDNSSEC`. |
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| `dns_record_mismatch` | warn | The record returned by DNS differs from the one declared in the service (typically a stale zone on the authoritative servers). |
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| `owner_hash_mismatch` | crit | Record owner-name first label is not `sha256(localpart)[:28]`; mail clients will never find it. |
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### OpenPGP-specific (RFC 7929)
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| Code | Severity | What it catches |
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| --- | --- | --- |
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| `pgp_parse_error` | crit | Malformed base64 or OpenPGP packet stream. |
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| `pgp_no_entity` | crit | Record decoded but carries no valid entity. |
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| `pgp_primary_revoked` | crit | Primary key has a revocation signature. |
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| `pgp_primary_expired` | crit | Self-signature expired; clients will refuse to encrypt. |
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| `pgp_primary_expiring_soon` | warn | Expires within the `certExpiryWarnDays` window (default 30). |
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| `pgp_weak_algorithm` | warn | Uses DSA / ElGamal (phase-out). |
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| `pgp_weak_key_size` | crit / warn | RSA below 2048 bits is critical, 2048-3071 is a warn. |
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| `pgp_no_encryption_subkey` | crit | No active key in the entity advertises encryption capability. |
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| `pgp_no_identity` | warn | No self-signed User ID. |
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| `pgp_uid_mismatch` | info | None of the UIDs reference `<username@…>`. |
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| `pgp_multiple_entities` | warn | Record carries more than one entity (RFC 7929 recommends one). |
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| `pgp_record_too_large` | warn | Raw key > 4 KiB; forces UDP→TCP fallback on every lookup. |
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### SMIMEA-specific (RFC 8162)
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| Code | Severity | What it catches |
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| --- | --- | --- |
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| `smimea_bad_usage` / `_selector` / `_match_type` | crit | Field outside the allowed range. |
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| `smimea_cert_parse_error` | crit | Hex-encoded blob is not a valid X.509 certificate / SPKI. |
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| `smimea_cert_expired` / `_not_yet_valid` | crit | `notBefore` / `notAfter` gate the current time out. |
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| `smimea_cert_expiring_soon` | warn | Within the `certExpiryWarnDays` window. |
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| `smimea_no_email_protection_eku` | crit / warn | Missing `emailProtection` EKU (RFC 8550/8551 agents will reject). |
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| `smimea_missing_key_usage` | warn | Neither `digitalSignature` nor `keyEncipherment` key-usage is set. |
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| `smimea_email_mismatch` | info | No email SAN starts with `<username>@`. |
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| `smimea_weak_signature_algorithm` | crit | MD5 / SHA-1 based signature. |
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| `smimea_weak_key_size` | crit / warn | RSA < 2048 / 3072 bits. |
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| `smimea_self_signed` | info | Self-signed certificate paired with PKIX-EE usage. |
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| `smimea_hash_only` | info | Matching-type 1/2 only carries a digest; certificate can't be inspected. |
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## Why a bespoke checker instead of a third-party testsuite?
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There is no canonical "OPENPGPKEY / SMIMEA testsuite" in Go or as a
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self-hostable online service:
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- `ldns-dane` (NLnet Labs) validates DANE-TLSA and handles SMIMEA only
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shallowly (it parses the record without deep certificate checks).
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- `hokey` (Paul Wouters) queries OPENPGPKEY but does not validate the
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key material.
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- Online DANE validators (e.g. `dane.sys4.de`, `has-tls-rpt.com`) focus
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on SMTP DANE-TLSA, not email-identity records.
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The heavy lifting here is standard Go parsing:
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- `github.com/ProtonMail/go-crypto/openpgp` (maintained fork of the
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deprecated `golang.org/x/crypto/openpgp`) for OpenPGP packet parsing,
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UIDs, subkeys, revocations, key-lifetime self-signatures.
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- `crypto/x509` for SMIMEA certificate parsing, validity window, EKU,
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key-usage, signature-algorithm and key-size checks.
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- `github.com/miekg/dns` for the DNS+EDNS0+DO query and the `AD` flag
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read-back used as the DNSSEC-validation signal.
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## Options
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| Id | Type | Default | Description |
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| --- | --- | --- | --- |
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| `resolver` | string | *(system)* | Validating resolver to query; comma-separated list accepted. |
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| `certExpiryWarnDays` | number | 30 | Raise an `expiring_soon` warning within this window. |
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| `requireDNSSEC` | bool | true | When false, missing AD is a warn instead of crit. |
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| `requireEmailProtection` | bool | true | When false, missing `emailProtection` EKU is a warn instead of crit. |
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Auto-filled by the host: `domain_name`, `subdomain`, `service`,
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`service_type`.
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## Running
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```bash
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# Plugin (loaded by happyDomain at startup)
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make plugin
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# Standalone HTTP server
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make && ./checker-openpgpkey -listen :8080
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```
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## HTML report
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The report renders as a self-contained HTML document intended for
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embedding in an `<iframe>` (the same contract as the other happyDomain
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checkers). It is organised as:
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1. **Header**: status badge, queried owner name, resolver used, DNSSEC
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flag.
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2. **Most common issues (fix these first)**: remediation cards shown
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*only* when a matching finding was emitted. Each card carries the
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concrete shell commands / zone-file snippets the user needs.
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3. **OpenPGP key / SMIMEA record**: structured details for the
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parsed material (fingerprint, UIDs, subkeys, cert subject/issuer,
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EKU/KU flags, …).
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4. **Findings**: the full table of per-finding code / severity /
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message / fix hints, sorted by severity.
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