# FABRIC-3.7.md — Phase 8 PKI: the elevation entrypoint **Status: OPEN — design only, no code written or authorized.** **CORRECTION (2026-09-22, before any code was written against this document): §2's central claim — that the old `SEND-ELEVATE-REQUEST` passed a raw cross-VM address into `ELEVATE-GRANT`'s `waddr` — is wrong.** Found while starting Part A's implementation: reading the actual deleted source (`git show 3e201c8^:capsules/common/messaging.4th`, block 5040) shows `SEND-ELEVATE-REQUEST` copied the target word's **name as literal character bytes** (via `ELEVATE-REQ-APPEND`'s `CMOVE`) into a scratch buffer, building the text `S" " ELEVATE-GRANT`, and sent *that whole string* to Hera. When Hera's own interpreter runs `S" "`, it allocates a fresh string **in Hera's own memory** and pushes Hera's own valid address — no numeric cross-VM address ever appears anywhere in this flow. §2 was written from `ELEVATE-GRANT`'s signature alone, assuming the caller forwarded a raw address, without first reading how the caller actually built its message. It didn't. **What is still real, much narrower than originally claimed:** if a future caller ever spliced *attacker-influenced* text into the name field without checking for an embedded `"` character, that could break out of the `S" ... "` literal early and inject arbitrary FORTH source, executed with Hera's privilege. That's an input-validation discipline question for whoever writes the new caller (validate: no embedded `"`, or just always use a compile-time-fixed literal name, never a runtime-supplied one) — not an architectural cross-VM-memory defect requiring the buffer/message redesign §3 originally called for. **§3's proposed mechanism (Hera-side fixed receive buffer, kernel-constructed integer-literal-only command) is not needed** — the original text-copy design was already safe against the bug as actually diagnosed. Kept below, struck through, for traceability, per this series' own rule against silently rewriting a prior state. Successor to `FABRIC-3.5.md`/`FABRIC-3.6.md` (both CLOSED/ARCHIVAL at `v2.1.0`) for exactly one topic: the Ed25519-challenge-response elevation entrypoint that `.claude/CLAUDE.md`'s ACL section names as Phase 8, the last open item in the word-level ACL system. This is a **new document**, not a reopening of `FABRIC-3.6.md` — that document's own close header says future fleet work gets its own document, and this is that. **Provenance.** Written 2026-09-22, immediately after `FABRIC-3.6.md`'s close, from a design conversation with Captain Bob about a security concern he raised directly: how to rebuild the elevation entrypoint that Phase 4's Category B strip left dangling, without reopening a hole. The design below was proposed, and Captain Bob asked for it in writing here rather than left only in session memory. --- ## 1. What's dangling, and why `FABRIC-3.6.md` Phase 4 (Category B strip, 2026-09-22) deleted `capsules/common/messaging.4th` after every FORTH-owned message type had been cut over to kernel-Hermes. One casualty was collateral, not intended: `SEND-ELEVATE-REQUEST` (`messaging.4th` block 5040) was the only caller of both `KH-ELEVATE-SEND` (`src/starkernel/repl.c`) and, transitively, `ELEVATE-GRANT` (`capsules/zuse-eligibility.4th`, blocks 4021–4022). All three still exist in the tree. `ELEVATE-GRANT` is still loaded at boot (`capsules/init.4th:18`). Nothing can call it any more. Captain Bob's decision at the time (`FABRIC-3.6.md`'s own Phase 4 entry): leave it unreachable, don't patch a caller back in as part of that strip. Phase 8 builds its own entrypoint instead of resuming this one. **This document is that entrypoint's design.**
Original §2/§3 (WRONG — see the correction at the top of this document; kept for traceability, not current design) ### 2. The security hole in the old mechanism — found before any code was written `ELEVATE-GRANT`'s signature, unchanged since it was written: ``` ELEVATE-GRANT ( waddr wu pk0 pk1 pk2 pk3 -- ) ``` `waddr`/`wu` are an address/length pair meant to point at the string naming the word to elevate. `pk0`–`pk3` are the caller's Ed25519 pubkey, packed 8 bytes per cell (`ELEVATE-PUBKEY-UNPACK`, `mama_forth_words.c`). **The old `SEND-ELEVATE-REQUEST` computed `waddr` in the *sending* VM's own address space, but `ELEVATE-GRANT` always executes on Hera** (`ELEVATE-GRANT always runs on Hera` — `repl.c`'s own comment on `KH-ELEVATE-SEND`, still there). A word's name string lives in the sending VM's memory. `ELEVATE-GRANT` dereferences `waddr` in Hera's memory. Those are not the same address space by construction — `vaddr_t` is per-VM. **Consequence:** whoever controls `waddr` controls what bytes `NAME>XT` reads and resolves as a word name, in Hera's dictionary, not the caller's. This is not "the string might be malformed" — it is a primitive for making Hera's own `ELEVATE-GRANT` grant `ACL-ALLOW!`/`ACL-TTL!` on *whatever dictionary entry the attacker's chosen `waddr` happens to land on*, regardless of what word name the caller claims to be requesting elevation for. A caller who can influence `waddr` at all — not forge a signature, not defeat `zuse_eligibility_is_member()`, just choose a number — has a privilege-escalation primitive against the fleet governor. This was never exploited (the entrypoint has had zero live callers since the file that called it was deleted), and is reported here as a design defect found by inspection, not a live incident. ### 3. The fix: never cross an address, only ever cross bytes This project already solved the general version of this problem once, this same session (`FABRIC-3.6.md` tasks 3.8/3.9, the payload-aliasing fix): a kernel-Hermes message's payload must be **copied into the message's own storage**, never a pointer into the sender's memory that might be reused or freed before the receiver drains it. `SkHermesMessage.payload_buf` (`include/starkernel/vm/kernel_hermes.h:160`, `SK_HERMES_CHUNK_MAX_PAYLOAD` = 1024 bytes) is exactly that fix, already built, already proven on all three architectures. **The elevation entrypoint's hole is the same defect one level up: an address crossing a boundary it isn't valid on the other side of.** The fix generalizes directly: 1. **Never send `waddr`/`wu` across the kernel-Hermes boundary.** Send the pubkey (32 bytes, already the right shape for `payload_buf`) and the target word's **name, as literal bytes**, copied inline into the message payload — not an address, the actual characters. This is already how `CONSOLE-CMD-EVENT`'s payload works (a command string's bytes, not a pointer to one), so this isn't a new pattern, it's applying the existing one to the one caller that still passed a raw address. 2. **On receipt, kernel-Hermes's C drain-checkpoint copies those name bytes into a small, fixed, kernel-owned buffer that already lives in Hera's own VM memory** — a receive-side mirror of the existing send-side pattern (`g_kh_elevate_buf`, `repl.c:445`, is the already-built precedent for "a static buffer this mechanism owns"; this needs its Hera-side counterpart). The buffer's address is a compile-time constant, known to the kernel, never computed from anything the caller supplied. 3. **The FORTH command handed to `vm_interpret()` on Hera references only that fixed buffer's address and length as plain integer literals.** Both are always kernel-controlled. Neither is ever derived from caller input. `ELEVATE-GRANT` itself does not change — same signature, same `zuse_eligibility_is_member()` check, same `ACL-ALLOW!`/`ACL-TTL!` grant. Policy logic stays in FORTH, per `ACL.4th`'s own rule (no new C primitive for policy) — this fix is entirely about how bytes get from one VM to another, not about who is allowed to grant what. **Why this closes the hole structurally, not by validation:** there is no string to sanitize and no address to bounds-check, because the interpreted command never contains anything an attacker touched except opaque data bytes that get copied, never dereferenced as a pointer, by the receiving side. The class of bug (cross-address-space pointer confusion) becomes impossible by construction, the same way `payload_buf` made use-after-free impossible by construction rather than by careful lifetime tracking.
## 2 (corrected). What the old mechanism actually did, and the one real gap in it Re-read from the actual deleted source (`git show 3e201c8^:capsules/common/messaging.4th`, blocks 5039–5040): `SEND-ELEVATE-REQUEST ( pk3 pk2 pk1 pk0 waddr wu -- )` used `waddr`/`wu` only to `CMOVE` the target word's **name bytes**, as text, into a scratch buffer (`ELEVATE-REQ-BUF`/`ELEVATE-REQ-APPEND`) it owned — building the literal string `S" " ELEVATE-GRANT` entirely in the *sending* VM's own memory. Only that finished string — not `waddr` itself — went to `KH-ELEVATE-SEND` and across to Hera. When Hera's interpreter runs `S" "`, Hera's own `S"` allocates a fresh string **in Hera's own memory** and pushes Hera's own valid address. `waddr`/`wu` never cross the VM boundary as numbers at any point — only as copied character content. There is no cross-VM pointer dereference anywhere in this flow. **The one real, much narrower gap:** the name text is spliced into `S" ... "` with no check for an embedded `"` character. If a future caller ever passed attacker-influenced text as the name (none ever did — the word had zero live callers), a `"` in the name would close the string literal early and let the rest of the name execute as raw FORTH source, with Hera's privilege. This is a caller-discipline / input-validation question, not an architectural defect: either always use a compile-time-fixed name literal at the call site (no runtime input, no risk at all), or validate for an embedded `"` before building the command if a name ever does need to come from something less trusted than the call site's own source code. **Net effect on Phase 8 v1's scope:** Part A, as originally conceived in §3 above, is not needed. If a `SEND-ELEVATE-REQUEST` replacement is ever built, it can follow the original text-copy design as-is, with the one-line `"`-check added if and only if the name is ever runtime-supplied rather than a fixed literal. No kernel-Hermes/`repl.c` changes required. Part B (`capsules/zuse.4th`, gating `ZUSE-ELIGIBILITY-ADD`) stands on its own, independently verified, unaffected by this correction. ## 4. What Phase 8 actually needs to build Corrected per §2's re-read above. Concretely, when Phase 8 next picks this up: - If a caller into `ELEVATE-GRANT` is ever needed again, rebuild it close to the original `SEND-ELEVATE-REQUEST` shape (`ELEVATE-REQ-BUF`/`ELEVATE-REQ-APPEND`/text-copy into `S" ... "`) — it was already safe. Add the one-line embedded-`"` check only if the name is ever runtime-supplied rather than a call-site literal. No `kernel_hermes.c`/`kernel_hermes.h`/ `repl.c` changes needed for this. - `ELEVATE-GRANT` unchanged either way. - **Part B is done** (`capsules/zuse.4th`, committed and three-arch verified this session, 2026-09-22) — `ZUSE-ELIGIBILITY-ADD` denied by default, granted only inside `ACL-ZUSE-BOOT`'s authenticated branch. This closes the actual "grant yourself eligibility with no real drive at all" path — a real, independently-confirmed gap, unaffected by this correction. - **Defending against a cloned drive — settled, 2026-09-23: not going to happen, by design.** Today, WIREBIND/MINT trust whatever identity is stored on an attached thumbdrive with no challenge at all (confirmed by grep: no `ed25519_sign`/`ed25519_verify` call anywhere in `capsule_wirebind.c` or `capsule_mint.c`), and the private key seed itself is stored in plaintext on the drive, read in the same devblock as the pubkey/cert. **This is accepted, not a gap.** Captain Bob, directly: *"nothing like a pin or a password or secret code or any bullshit... Everybody has secrets. There's only the drive."* Physical possession of the drive is the entire, deliberate credential model — a byte-for-byte clone being equivalent to the real drive is the accepted design, not a defect to close. A PIN/passphrase second factor was built, live-tested on all three architectures, and fully reverted before commit (`/home/rajames/.claude/plans/jiggly-cuddling-stallman.md`, now marked rejected; memory `feedback_no_knowledge_factor_identity`) — **do not revisit a knowledge-factor approach here.** Any future work in this space needs a fundamentally different mechanism (not something typed and known) or stays an accepted limitation. - **Phase 8 v3, 2026-09-23 — done, a distinct and narrower concern from the item above.** The "accepted limitation" above is about a drive image copied *outside* StarshipOS entirely (e.g. imaged on an external computer) — that's still accepted, unchanged by this item. Captain Bob separately asked to close a narrower, different threat: **cloning a device's block content from *within* StarshipOS's own console**, using its own stock, unpinned words (` BLOCK BUFFER 1024 MOVE`/`RELOCATE-BLOCK`). That's now closed — `MOVE`/`CMOVE`/ `CMOVE>`/`RELOCATE-BLOCK` all refuse a same-VM, cross-device copy, verified live on all three architectures. See `/home/rajames/.claude/plans/jiggly-cuddling-stallman.md`'s "Phase 8 v3" section for the full design and verification record. The identity record itself (seed/pubkey/cert) was already unreachable from FORTH before this — this closes the one real gap the research found: ordinary block content, not the identity record. ## 5. What this document is not Not a reopening of `FABRIC-3.6.md`, not a change to anything currently built, not an authorization to write code. Per this series' own convention: design here, execution gets its own document when the work actually starts, the same relationship `FABRIC-3.5.md` had to `FABRIC-3.6.md`.