feat(pal/std): enforce session-scoped key isolation at vault access

[jaygmsft]

A key created with Session availability was resolvable — and thus usable and deletable — from any other session on the same partition, because the std PAL vault resolved key ids without checking the session binding. Only the mock enforced this. This closes that gap so the std PAL / emulator matches the reference firmware behaviour.

Enforcement is added at the vault access chokepoint: a new assert_key_session_access gates vault_key, vault_key_kind, and vault_key_attrs. Session-bound keys are only visible from the session that created them (mapped via the SQE session id → physical session id); from any other session they report KeyNotFound. Partition-scoped App/persistent keys carry no binding and stay accessible everywhere, including internal firmware IOs whose SQE has no session. Because DeleteKey resolves attrs through the guarded path, delete inherits the same isolation.

Adds a cross_session_key_access_smoke suite (9 smoke tests) covering the App-vs-Session semantics across three handler paths — use (vault_key), masked-blob re-import (UnmaskKey), and delete — over AES and ECC keys, plus RSA-unwrapped keys:

• App key usable / unmaskable / deletable from another session
• Session key not usable / not unmaskable / not deletable elsewhere
• ECC App key signable cross-session; Session key only in its session
• Session-key blob never re-importable (MK_SESSION is fresh-random per session, not seed-derived), same or different session seed

The uno PAL vault is a separate crate and does not yet enforce this; tracked as a follow-up for the hardware bring-up.

Test: emu azihsm_ddi_mbor_types full 597/597 passed; emu smoke gate 94/94 passed; mock cross-session suite 9/9 passed.

Copilot-Session: 82c8bd53-6639-46fc-8a79-a7539921e4c1

[Copilot]

Pull request overview

This PR tightens session-scoped key isolation in the std PAL by enforcing session bindings at the vault access chokepoint, making the emulator/std PAL behavior match the reference firmware and the mock backend for session-availability keys.

Changes:

• Added session-binding enforcement in StdHsmPal vault lookups so Session-availability keys are only visible within their creating session.
• Exposed the stored per-key session binding from the std PAL KeyVault driver to support the new enforcement check.
• Added a new cross-session smoke test suite covering use-by-id, unmask/re-import, and delete semantics for App vs Session keys.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
fw/plat/std/pal/src/vault.rs	Adds assert_key_session_access and gates vault read/metadata access based on SQE session → physical session key mapping.
fw/plat/std/pal/src/drivers/vault.rs	Adds key_session_binding accessor to expose per-key session binding (session_key_id).
fw/plat/std/pal/Cargo.toml	Adds azihsm_fw_hsm_io dependency to interpret SQE session flags/IDs (Sqe).
ddi/mbor/types/tests/integration/cross_session_key_access_smoke.rs	Introduces new integration smoke tests validating App vs Session access across sessions for AES/ECC/RSA-unwrapped keys.
ddi/mbor/types/tests/azihsm_ddi_tests.rs	Registers the new cross-session smoke test module.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

ddi/mbor/types/tests/integration/cross_session_key_access_smoke.rs:372

• ecc_sign_with builds a 20-byte digest but passes DdiHashAlgorithm::Sha256. The EccSign handler requires at least the hash algorithm’s native digest length (32 bytes for SHA-256), so this will be rejected with InvalidArg (or could start failing if encoding changes). Use a 32-byte digest (matching other ECC sign tests) to ensure the test is validating session isolation rather than digest-length validation.

        MborByteArray::new([1u8; 96], 20).expect("digest byte array"),

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.