Here’s a tight idea I think you’ll like: **make every VEX “non‑affected” verdict explain itself with provable, symbol‑level evidence**—not just “package X isn’t reachable,” but “function `Foo::bar()` (the vulnerable sink) is never called in any admissible execution of image Y,” backed by cryptographic provenance.

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# Why this matters (quickly)

* **Trust**: Auditors and customers can verify why you suppressed a CVE.
* **Quiet scanner**: Fewer false alarms because decisions cite concrete call‑paths (or their absence).
* **Moat**: Competitors stop at file/package reachability; you show **function‑level** proof tied to in‑toto attestations.

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# Core concept (plain)

Blend two things:

1. **Deterministic symbol reachability** (per language): build minimal call graphs and mark whether the vulnerable symbol is callable from your app’s entrypoints.
2. **in‑toto‑anchored provenance**: sign the *inputs and reasoning* (rules, SBOM slice, call‑graph hash, evidence artifacts), so the verdict can be independently re‑verified.

Result: each VEX decision is a **verifiable mini‑proof**.

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# What the evidence looks like (per CVE/component)

* **Symbol set**: canonical IDs of vulnerable functions (e.g., `pkg@ver#Type::Method(sig)`).
* **Call‑graph digest**: hash of pruned call graph from app entrypoints to those symbols.
* **Evidence**:

  * Static: “No path from any entrypoint → {vuln symbols} (k=0).”
  * Optional runtime: sampled traces (EventPipe/JFR/eBPF) show **0 hits** to symbols/guards.
* **Context**: build inputs (SBOM, lockfiles, compile units), framework models used, versions.
* **Attestation**: in‑toto/DSSE signed bundle with reproducible scan manifest.

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# Minimal prototype this week (Scanner reachability scorer)

1. **Symbol mappers (MVP)**

   * .NET: read PDB + IL to enumerate `MethodDef` symbols; map NuGet pkg → assembly → methods.
   * JVM: JAR index + method table (from ASM); map Maven coords → classes → methods.
2. **Entrypoint discovery**

   * Docker CMD/ENTRYPOINT → process launch → managed main(s) (ASP.NET Program.Main, Spring Boot main).
3. **Shallow call‑graph** (no fancy points‑to yet):

   * Direct calls + common framework handoffs (ASP.NET routing → controller; Spring @RequestMapping → handler).
4. **Vuln ↔ symbol alignment**

   * Heuristics: match GHSA/OSV “affected functions” or patch diff to infer symbol names; fallback to package‑scope verdict with a flag “symbol‑inferred: false”.
5. **Decision object**

   * `ReachabilityDecision.json` with: entrypoints, symbol set, path_count, notes, hashes.
6. **Attest**

   * Emit `reachability.intoto.jsonl` (subject = image digest + SBOM component + symbol digest). Cosign with your test key.
7. **VEX output**

   * OpenVEX statement reason: `component_not_present` or `vulnerable_code_not_in_execute_path` with `justification_url` → small HTML report (signed).

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# Data & schemas to add

* `Scanner.Reachability/`

  * `SymbolIndex` (pkg → assemblies/classes/methods)
  * `EntryPoints` (per image, normalized)
  * `CallGraphPruned` (edges + hash)
  * `Decision` (path_count, evidence, versions)
* `Authority`

  * Key management for DSSE; policy to **require** reachability evidence for “non‑affected”.

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# Language roadmap (fast win → harder)

* **Week 1–2:** .NET + JVM shallow graphs + ASP.NET/Spring models.
* **Week 3–4:** Node/TS (TS compiler API), Go (SSA), Python (import graph + common web frameworks).
* **Stretch:** Rust/Swift (MIR/SIL summaries), native (symbols + coarse edges), Shell (exec chain).

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# Where to surface it (UX)

* VEX details panel: “Non‑affected (0 call paths)” → expand → show entrypoints, collapsed edge list, trace hit‑counts, and “Verify attestation” button.
* CLI: `stella scan --explain CVE-XYZ --verify-attestation`.

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# Guardrails

* If symbol mapping is uncertain, **do not** claim “non‑affected”; downgrade to “under review” with rationale.
* Cache symbol indexes per package version; keep the call‑graph pruned to entrypoint cones for speed.
* Everything reproducible: the **scan manifest** (feeds, rule versions, hashes) must recreate the same decision bit‑for‑bit.

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If you want, I can draft the exact C# namespaces, interfaces, and the OpenVEX + in‑toto payloads you can drop into `Scanner.Reachability` and `Authority.Attest`.