feat: generate additional credential types and X.509 identities

[domenkozar]

Summary

• add passphrase, mnemonic, wireguard_private_key, jwk_private_key, age_identity, and x509_identity generators
• add extract.source so JSON/INI fields and X.509 artifacts can be derived from another declared secret
• expose the new types and X.509 usage options through configuration validation, native bindings, and the Rust spec API
• document every addition as SecretSpec 0.21+

Mnemonics

• type = "mnemonic" defaults to a checksum-valid 24-word English BIP-39 value
• algorithm = "bip39" is an explicit subtype for future extensibility
• valid word counts are strictly limited to 12, 15, 18, 21, or 24
• SecretSpec returns the mnemonic itself and does not derive BIP-32 seeds, wallet keys, or the optional BIP-39 mnemonic passphrase

X.509 identities and extraction

• type = "x509_identity" generates a self-signed P-256 X.509 v3 identity and stores its canonical binary PKCS#12 form through encoding = "base64"
• generation requires explicit DNS/IP SANs, defaults to server_auth and 30 days, and caps validity at the current CA/Browser Forum 200-day subscriber-certificate maximum
• certificates use ECDSA/SHA-256, a positive 128-bit random serial, critical CA-false basic constraints and digital-signature key usage, EKU, SAN, and SKI
• PKCS#12 generation explicitly selects AES-256-CBC protection and HMAC-SHA-256 integrity with 100,000 iterations; its password is intentionally empty because the provider is the protection boundary and the PFX is an interoperable container
• source extraction exports PKCS#8 PEM/DER keys, leaf PEM/DER certificates, leaf-plus-issuer or issuer-only PEM chains, and complete PFX files
• imported/provider-backed PFX input is bounded and checked for a matching key, current certificate validity, coherent signatures, and one unambiguous chain before projection
• binary DER/PFX projections require as_path = true

extract.source is the only new composition-like mechanism: the existing extract.format selects both the component and representation. Named sources reuse the derived-secret dependency graph for order independence, scope closure, unknown-reference checks, and mixed cycle detection.

Other security properties

• generated passphrases use the BIP-39 2048-word list, default to seven words, and enforce a six-word minimum
• mnemonic entropy comes directly from the OS; entropy, internal mnemonic state, and temporary serialization use zeroization support
• WireGuard keys use the upstream X25519 clamping procedure
• Ed25519 JWKs use the fully specified RFC 9864 Ed25519 algorithm identifier; P-256 and RSA signing JWKs are also supported
• age identities are validated by the Rust age parser; hybrid ML-KEM-768+X25519 identities remain externally provisioned until supported by the Rust implementation

Verification

• cargo test --all: passed, including integration, compile/UI, and doctests
• focused X.509 generation/extraction/security tests: passed
• generic JSON extract.source end-to-end test: passed
• full documentation build: 89 pages, zero diagnostics
• repository Clippy and rustfmt pre-commit hooks: passed
• git diff --check: passed

Dependency

Stacked on #414, which adds the OpenPGP and SSH generation infrastructure this change extends.

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	secretspec	723a52f	Commit Preview URL Branch Preview URL	Sep 03 2026, 02:04 PM