Robert Allan JamesandClaude Sonnet 5
030a3e6dc0
Before flipping, found CAPSULE_SIG_MISSING (no signature at all) is the normal state everywhere except this machine -- CI and any other checkout have no access to the offline key, by design. Refusing on MISSING the same as INVALID would brick boot everywhere but here. Decided (on request): enforce ONLY on CAPSULE_SIG_INVALID (a signature that IS present but doesn't verify -- unambiguous tampering/corruption evidence). MISSING/NO_ROOT_KEY stay WARN-only permanently. All three capsule_birth.c call sites now return CAPSULE_RUN_ERR_INVALID on CAPSULE_SIG_INVALID, after logging the same WARN as before. Verified on all three architectures, both directions, per the original rollout commitment: positive case (real signed capsules) reboots clean with zero warnings on amd64/aarch64/riscv64. Negative case (same one-byte signature corruption used for the WARN-only proof, on Mama's own init.4th) now genuinely refuses identically on all three: "capsule sig: init.4th: INVALID" then "Init: Mama birth FAILED". The feared "no ok> at all" blast radius didn't materialize -- kernel_main.c already had graceful error handling for a failed Mama birth (log and continue, pre-existing code); the kernel reaches a degraded ok> rather than crashing, on all three architectures. Final acceptance pass (real signed capsules, tampering reverted) clean on all three. Milestone 6 is now fully closed except magic-number content-type detection (shared with Milestone 4, separate scope, not started). Documented in FABRIC-3.md. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01U14ET9CWAtbQMbYqomKgXd
53 lines
2.3 KiB
C
53 lines
2.3 KiB
C
/*
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* capsule_sig.h -- per-capsule Ed25519 signature verification
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* (Milestone 6, Phase 8). Deliberately kept separate from
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* capsule_validate.c: that function is already tested and its
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* signature/behavior stays untouched; this is a new, additive check
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* called alongside it, not folded into it.
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*
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* Enforced ONLY on CAPSULE_SIG_INVALID (2026-08-26, after landing
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* WARN-only and proving correct on all three architectures against both
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* a valid and a deliberately-corrupted capsule -- see FABRIC-3.md's
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* Milestone 6 writeup). CAPSULE_SIG_MISSING and CAPSULE_SIG_NO_ROOT_KEY
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* stay WARN-only, deliberately: MISSING is the normal state on every
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* machine without access to the offline signing key (CI, any other
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* checkout) -- refusing on it would brick boot everywhere but the one
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* machine that minted the key, not catch anything real. Only INVALID
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* (a signature that IS present but does not verify) is unambiguous
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* tampering/corruption evidence, safe to refuse on regardless of who's
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* building.
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*/
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#ifndef STARKERNEL_CAPSULE_SIG_H
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#define STARKERNEL_CAPSULE_SIG_H
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#include "starkernel/capsule.h"
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typedef enum {
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CAPSULE_SIG_OK = 0, /* has_sig=1, and it verifies */
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CAPSULE_SIG_MISSING, /* has_sig=0 -- not signed at all */
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CAPSULE_SIG_INVALID, /* has_sig=1 but verification failed */
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CAPSULE_SIG_NO_ROOT_KEY, /* couldn't find/parse the embedded intermediate cert */
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} CapsuleSigResult;
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/*
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* Verify capsule descs[index]'s Ed25519 signature against the embedded
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* snakeoil intermediate cert's public key (capsule name
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* "pki:snakeoil-intermediate.der", found and parsed once, cached for
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* every later call this boot -- the cert doesn't change mid-boot).
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*
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* descs/names/sigs must be the same three parallel arrays
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* (capsule_get_descriptors()/capsule_get_names()/capsule_get_signatures()),
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* desc_count their shared length, arena_base the payload arena
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* (capsule_get_arena()). index must be < desc_count.
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*/
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CapsuleSigResult capsule_verify_signature(
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const CapsuleDesc *descs, const CapsuleNameEntry *names,
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const CapsuleSigEntry *sigs, const uint8_t *arena_base,
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uint32_t desc_count, int index);
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/* Human-readable string for logging, mirroring
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* capsule_validate_result_str()'s existing shape. */
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const char *capsule_sig_result_str(CapsuleSigResult result);
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#endif /* STARKERNEL_CAPSULE_SIG_H */
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