LithosAnanake/kernel/include/starkernel/vm_identity.h

/*
  StarForth — Steady-State Virtual Machine Runtime

  Copyright (c) 2023–2025 Robert A. James
  All rights reserved.

  This file is part of the StarForth project.

  Licensed under the StarForth License, Version 1.0 (the "License");
  you may not use this file except in compliance with the License.

  You may obtain a copy of the License at:
      https://github.com/star.4th@proton.me/StarForth/LICENSE.txt

  This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
  express or implied, including but not limited to the warranties of
  merchantability, fitness for a particular purpose, and noninfringement.

  See the License for the specific language governing permissions and
  limitations under the License.
*/

/**
 * vm_identity.h - Per-VM owner identity + ACL capabilities (FABRIC-2.md
 * §F.2/§F.16, decided 2026-08-27/28)
 *
 * Holds only what a VM needs to prove *who owns it* and *what that owner
 * is allowed to do* -- never a private key. A regular VM's lock never
 * signs anything itself, so no seed/private material belongs here at all
 * (unlike Zuse's own zuse_cert_seed/zuse_cert_pubkey pair, which does need
 * one because she actively signs). Deliberately its own header rather
 * than inline fields on struct VM, mirroring VMUuid's own precedent
 * (vm_uuid.h) -- standing instruction: give real-shaped data its own
 * header and integrate as a field, don't grow struct VM ad hoc.
 *
 * acl_caps is a capability bitmask, not an ordered privilege tier
 * (decided 2026-08-28) -- independent bits, not a nested hierarchy. Zuse
 * is not a structurally special VM: her identity just has every bit set.
 * No bit values are assigned yet -- deliberate slack, per this project's
 * "flexibility until we understand the recipe" precedent (see
 * blk_meta_t's own acl_reserved bytes, FABRIC-2.md §F.4) -- real bits get
 * names only once the operation they gate actually gets built (BINDSTEP,
 * MINT, ...), not speculatively here.
 */

#ifndef STARKERNEL_VM_IDENTITY_H
#define STARKERNEL_VM_IDENTITY_H

#ifdef __STARKERNEL__

#include <stdint.h>
#include <stddef.h>

typedef struct {
    uint8_t  owner_pubkey[32]; /**< Ed25519 public key of this VM's owning
                                 *   identity. Meaningless unless installed
                                 *   is set. */
    uint8_t  installed;        /**< 0 = no identity installed yet (e.g.
                                 *   Hera/Hermes/Artemis today, before
                                 *   D.5's per-VM-identity work lands) --
                                 *   BINDSTEP-style checks must treat this
                                 *   as "no lock, allow freely," matching
                                 *   §F.9 decision 2. 1 = owner_pubkey/
                                 *   acl_caps are real. */
    uint32_t acl_caps;         /**< Capability bitmask. All-zero until a
                                 *   real caller defines and checks a bit;
                                 *   VM_IDENTITY_CAP_ALL for Zuse's own
                                 *   identity ("her ACL just grants
                                 *   everything," not a special VM type). */
} VMIdentity;

/** Every capability bit set -- Zuse's own identity uses this, not a
 *  distinct "is this Zuse" flag anywhere else in the system. */
#define VM_IDENTITY_CAP_ALL 0xFFFFFFFFu

/**
 * vm_identity_has_cap - Check whether an installed identity holds a
 * capability. Returns 0 (denied) if identity isn't installed at all --
 * callers that mean "no lock, allow freely" (§F.9 decision 2) must check
 * installed themselves first, not call this and treat 0 as a denial in
 * that case.
 *
 * @param id   Identity to check.
 * @param cap  A single capability bit (or bits) to test for.
 * @return     Non-zero if id is installed and every bit in cap is set.
 */
int vm_identity_has_cap(const VMIdentity *id, uint32_t cap);

/**
 * vm_identity_from_cert - CERTVERIFY (FABRIC-2.md §F.7/§F.17): verify a
 * DER-encoded, Zuse-signed X.509 cert and populate a VMIdentity from it.
 *
 * Three checks, all must pass: the cert's own signature verifies against
 * issuer_pubkey (Zuse's own on-device key -- a separate trust root from
 * the capsule-PKI chain, no chain walk needed); the cert's serialNumber
 * equals drive_uuid byte-for-byte (binds this cert to one physical drive,
 * §F.7 decision 2 -- a copied cert on different media will not verify);
 * the subject's Ed25519 public key extracts cleanly.
 *
 * acl_caps is *not* read from the cert -- nothing in the decided cert
 * fields encodes capabilities (§F.16). It's supplied by the caller, whose
 * job it is to decide what this verified identity is allowed to do (e.g.
 * comparing the extracted pubkey against Zuse's own system-resident
 * pubkey to decide VM_IDENTITY_CAP_ALL vs. a lesser default) -- that
 * policy decision doesn't belong inside a pure verification function.
 *
 * @param out          Populated on success; left untouched on failure.
 * @param der          DER-encoded certificate bytes.
 * @param der_len      Their length.
 * @param issuer_pubkey Zuse's own Ed25519 public key.
 * @param drive_uuid   This physical drive's own 16-byte drive_uuid
 *                      (homeblocks_sig_t), compared against the cert's
 *                      serialNumber.
 * @param acl_caps     Capability bitmask to install, caller-decided.
 * @return 0 on success, -1 if any check fails (malformed DER, wrong
 *         signature algorithm, signature doesn't verify, serial mismatch,
 *         or the extracted key isn't a valid Ed25519 point).
 */
int vm_identity_from_cert(VMIdentity *out, const uint8_t *der, size_t der_len,
                           const uint8_t issuer_pubkey[32],
                           const uint8_t drive_uuid[16], uint32_t acl_caps);

#endif /* __STARKERNEL__ */

#endif /* STARKERNEL_VM_IDENTITY_H */