save progress
This commit is contained in:
StellaOps Bot
@@ -0,0 +1,919 @@
|
||||
Here’s a compact, practical way to add two high‑leverage capabilities to your scanner: **DSSE‑signed path witnesses** and **Smart‑Diff × Reachability**—what they are, why they matter, and exactly how to implement them in Stella Ops without ceremony.
|
||||
|
||||
---
|
||||
|
||||
# 1) DSSE‑signed path witnesses (entrypoint → calls → sink)
|
||||
|
||||
**What it is (in plain terms):**
|
||||
When you flag a CVE as “reachable,” also emit a tiny, human‑readable proof: the **exact path** from a real entrypoint (e.g., HTTP route, CLI verb, cron) through functions/methods to the **vulnerable sink**. Wrap that proof in a **DSSE** envelope and sign it. Anyone can verify the witness later—offline—without rerunning analysis.
|
||||
|
||||
**Why it matters:**
|
||||
|
||||
* Turns red flags into **auditable evidence** (quiet‑by‑design).
|
||||
* Lets CI/CD, auditors, and customers **verify** findings independently.
|
||||
* Enables **deterministic replay** and provenance chains (ties nicely to in‑toto/SLSA).
|
||||
|
||||
**Minimal JSON witness (stable, vendor‑neutral):**
|
||||
|
||||
```json
|
||||
{
|
||||
"witness_schema": "stellaops.witness.v1",
|
||||
"artifact": { "sbom_digest": "sha256:...", "component_purl": "pkg:nuget/Example@1.2.3" },
|
||||
"vuln": { "id": "CVE-2024-XXXX", "source": "NVD", "range": "≤1.2.3" },
|
||||
"entrypoint": { "kind": "http", "name": "GET /billing/pay" },
|
||||
"path": [
|
||||
{"symbol": "BillingController.Pay()", "file": "BillingController.cs", "line": 42},
|
||||
{"symbol": "PaymentsService.Authorize()", "file": "PaymentsService.cs", "line": 88},
|
||||
{"symbol": "LibXYZ.Parser.Parse()", "file": "Parser.cs", "line": 17}
|
||||
],
|
||||
"sink": { "symbol": "LibXYZ.Parser.Parse()", "type": "deserialization" },
|
||||
"evidence": {
|
||||
"callgraph_digest": "sha256:...",
|
||||
"build_id": "dotnet:RID:linux-x64:sha256:...",
|
||||
"analysis_config_digest": "sha256:..."
|
||||
},
|
||||
"observed_at": "2025-12-18T00:00:00Z"
|
||||
}
|
||||
```
|
||||
|
||||
**Wrap in DSSE (payloadType & payload are required)**
|
||||
|
||||
```json
|
||||
{
|
||||
"payloadType": "application/vnd.stellaops.witness+json",
|
||||
"payload": "base64(JSON_above)",
|
||||
"signatures": [{ "keyid": "attestor-stellaops-ed25519", "sig": "base64(...)" }]
|
||||
}
|
||||
```
|
||||
|
||||
**.NET 10 signing/verifying (Ed25519)**
|
||||
|
||||
```csharp
|
||||
using System.Security.Cryptography;
|
||||
using System.Text.Json;
|
||||
|
||||
var payloadBytes = JsonSerializer.SerializeToUtf8Bytes(witnessJsonObj);
|
||||
var dsse = new {
|
||||
payloadType = "application/vnd.stellaops.witness+json",
|
||||
payload = Convert.ToBase64String(payloadBytes),
|
||||
signatures = new [] { new { keyid = keyId, sig = Convert.ToBase64String(Sign(payloadBytes, privateKey)) } }
|
||||
};
|
||||
byte[] Sign(byte[] data, byte[] privateKey)
|
||||
{
|
||||
using var ed = new Ed25519();
|
||||
// import private key, sign data (left as your Ed25519 helper)
|
||||
return ed.SignData(data, privateKey);
|
||||
}
|
||||
```
|
||||
|
||||
**Where to emit:**
|
||||
|
||||
* **Scanner.Worker**: after reachability confirms `reachable=true`, emit witness → **Attestor** signs → **Authority** stores (Postgres) → optional Rekor‑style mirror.
|
||||
* Expose `/witness/{findingId}` for download & independent verification.
|
||||
|
||||
---
|
||||
|
||||
# 2) Smart‑Diff × Reachability (incremental, low‑noise updates)
|
||||
|
||||
**What it is:**
|
||||
On **SBOM/VEX/dependency** deltas, don’t rescan everything. Update only **affected regions** of the call graph and recompute reachability **just for changed nodes/edges**.
|
||||
|
||||
**Why it matters:**
|
||||
|
||||
* **Order‑of‑magnitude faster** incremental scans.
|
||||
* Fewer flaky diffs; triage stays focused on **meaningful risk change**.
|
||||
* Perfect for PR gating: “what changed” → “what became reachable/unreachable.”
|
||||
|
||||
**Core idea (graph‑reachability):**
|
||||
|
||||
* Maintain a per‑service **call graph** `G = (V, E)` with **entrypoint set** `S`.
|
||||
* On diff: compute changed nodes/edges ΔV/ΔE.
|
||||
* Run **incremental BFS/DFS** from impacted nodes to sinks (forward or backward), reusing memoized results.
|
||||
* Recompute only **frontiers** touched by Δ.
|
||||
|
||||
**Minimal tables (Postgres):**
|
||||
|
||||
```sql
|
||||
-- Nodes (functions/methods)
|
||||
CREATE TABLE cg_nodes(
|
||||
id BIGSERIAL PRIMARY KEY,
|
||||
service TEXT, symbol TEXT, file TEXT, line INT,
|
||||
hash TEXT, UNIQUE(service, hash)
|
||||
);
|
||||
-- Edges (calls)
|
||||
CREATE TABLE cg_edges(
|
||||
src BIGINT REFERENCES cg_nodes(id),
|
||||
dst BIGINT REFERENCES cg_nodes(id),
|
||||
kind TEXT, PRIMARY KEY(src, dst)
|
||||
);
|
||||
-- Entrypoints & Sinks
|
||||
CREATE TABLE cg_entrypoints(node_id BIGINT REFERENCES cg_nodes(id) PRIMARY KEY);
|
||||
CREATE TABLE cg_sinks(node_id BIGINT REFERENCES cg_nodes(id) PRIMARY KEY, sink_type TEXT);
|
||||
|
||||
-- Memoized reachability cache
|
||||
CREATE TABLE cg_reach_cache(
|
||||
entry_id BIGINT, sink_id BIGINT,
|
||||
path JSONB, reachable BOOLEAN,
|
||||
updated_at TIMESTAMPTZ,
|
||||
PRIMARY KEY(entry_id, sink_id)
|
||||
);
|
||||
```
|
||||
|
||||
**Incremental algorithm (pseudocode):**
|
||||
|
||||
```text
|
||||
Input: ΔSBOM, ΔDeps, ΔCode → ΔNodes, ΔEdges
|
||||
1) Apply Δ to cg_nodes/cg_edges
|
||||
2) ImpactSet = neighbors(ΔNodes ∪ endpoints(ΔEdges))
|
||||
3) For each e∈Entrypoints intersect ancestors(ImpactSet):
|
||||
Recompute forward search to affected sinks, stop early on unchanged subgraphs
|
||||
Update cg_reach_cache; if state flips, emit new/updated DSSE witness
|
||||
```
|
||||
|
||||
**.NET 10 reachability sketch (fast & local):**
|
||||
|
||||
```csharp
|
||||
HashSet<int> ImpactSet = ComputeImpact(deltaNodes, deltaEdges);
|
||||
foreach (var e in Intersect(Entrypoints, Ancestors(ImpactSet)))
|
||||
{
|
||||
var res = BoundedReach(e, affectedSinks, graph, cache);
|
||||
foreach (var r in res.Changed)
|
||||
{
|
||||
cache.Upsert(e, r.Sink, r.Path, r.Reachable);
|
||||
if (r.Reachable) EmitDsseWitness(e, r.Sink, r.Path);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**CI/PR flow:**
|
||||
|
||||
1. Build → SBOM diff → Dependency diff → Call‑graph delta.
|
||||
2. Run incremental reachability.
|
||||
3. If any `unreachable→reachable` transitions: **fail gate**, attach DSSE witnesses.
|
||||
4. If `reachable→unreachable`: auto‑close prior findings (and archive prior witness).
|
||||
|
||||
---
|
||||
|
||||
# UX hooks (quick wins)
|
||||
|
||||
* In findings list, add a **“Show Witness”** button → modal renders the signed path (entrypoint→…→sink) + **“Verify Signature”** one‑click.
|
||||
* In PR checks, summarize only **state flips** with tiny links: “+2 reachable (view witness)” / “−1 (now unreachable)”.
|
||||
|
||||
---
|
||||
|
||||
# Minimal tasks to get this live
|
||||
|
||||
* **Scanner.Worker**: build call‑graph extraction (per language), add incremental graph store, reachability cache.
|
||||
* **Attestor**: DSSE signing endpoint + key management (Ed25519 by default; PQC mode later).
|
||||
* **Authority**: tables above + witness storage + retrieval API.
|
||||
* **Router/CI plugin**: PR annotation with **state flips** and links to witnesses.
|
||||
* **UI**: witness modal + signature verify.
|
||||
|
||||
If you want, I can draft the exact Postgres migrations, the C# repositories, and a tiny verifier CLI that checks DSSE signatures and prints the call path.
|
||||
Below is a concrete, buildable blueprint for an **advanced reachability analysis engine** inside Stella Ops. I’m going to assume your “Stella Ops” components are roughly:
|
||||
|
||||
* **Scanner.Worker**: runs analyses in CI / on artifacts
|
||||
* **Authority**: stores graphs/findings/witnesses
|
||||
* **Attestor**: signs DSSE envelopes (Ed25519)
|
||||
* (optional) **SurfaceBuilder**: background worker that computes “vuln surfaces” for packages
|
||||
|
||||
The key advance is: **don’t treat a CVE as “a package”**. Treat it as a **set of trigger methods** (public API) that can reach the vulnerable code inside the dependency—computed by “Smart‑Diff” once, reused everywhere.
|
||||
|
||||
---
|
||||
|
||||
## 0) Define the contract (precision/soundness) up front
|
||||
|
||||
If you don’t write this down, you’ll fight false positives/negatives forever.
|
||||
|
||||
### What Stella Ops will guarantee (first release)
|
||||
|
||||
* **Whole-program static call graph** (app + selected dependency assemblies)
|
||||
* **Context-insensitive** (fast), **path witness** extracted (shortest path)
|
||||
* **Dynamic dispatch handled** with CHA/RTA (+ DI hints), with explicit uncertainty flags
|
||||
* **Reflection handled best-effort** (constant-string resolution), otherwise “unknown edge”
|
||||
|
||||
### What it will NOT guarantee (first release)
|
||||
|
||||
* Perfect handling of reflection / `dynamic` / runtime codegen
|
||||
* Perfect delegate/event resolution across complex flows
|
||||
* Full taint/dataflow reachability (you can add later)
|
||||
|
||||
This is fine. The major value is: “**we can show you the call path**” and “**we can prove the vuln is triggered by calling these library APIs**”.
|
||||
|
||||
---
|
||||
|
||||
## 1) The big idea: “Vuln surfaces” (Smart-Diff → triggers)
|
||||
|
||||
### Problem
|
||||
|
||||
CVE feeds typically say “package X version range Y is vulnerable” but rarely say *which methods*. If you only do package-level reachability, noise is huge.
|
||||
|
||||
### Solution
|
||||
|
||||
For each CVE+package, compute a **vulnerability surface**:
|
||||
|
||||
* **Candidate sinks** = methods changed between vulnerable and fixed versions (diff at IL level)
|
||||
* **Trigger methods** = *public/exported* methods in the vulnerable version that can reach those changed methods internally
|
||||
|
||||
Then your service scan becomes:
|
||||
|
||||
> “Can any entrypoint reach any trigger method?”
|
||||
|
||||
This is both faster and more precise.
|
||||
|
||||
---
|
||||
|
||||
## 2) Data model (Authority / Postgres)
|
||||
|
||||
You already had call graph tables; here’s a concrete schema that supports:
|
||||
|
||||
* graph snapshots
|
||||
* incremental updates
|
||||
* vuln surfaces
|
||||
* reachability cache
|
||||
* DSSE witnesses
|
||||
|
||||
### 2.1 Graph tables
|
||||
|
||||
```sql
|
||||
CREATE TABLE cg_snapshots (
|
||||
snapshot_id BIGSERIAL PRIMARY KEY,
|
||||
service TEXT NOT NULL,
|
||||
build_id TEXT NOT NULL,
|
||||
graph_digest TEXT NOT NULL,
|
||||
created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
|
||||
UNIQUE(service, build_id)
|
||||
);
|
||||
|
||||
CREATE TABLE cg_nodes (
|
||||
node_id BIGSERIAL PRIMARY KEY,
|
||||
snapshot_id BIGINT REFERENCES cg_snapshots(snapshot_id) ON DELETE CASCADE,
|
||||
method_key TEXT NOT NULL, -- stable key (see below)
|
||||
asm_name TEXT,
|
||||
type_name TEXT,
|
||||
method_name TEXT,
|
||||
file_path TEXT,
|
||||
line_start INT,
|
||||
il_hash TEXT, -- normalized IL hash for diffing
|
||||
flags INT NOT NULL DEFAULT 0, -- bitflags: has_reflection, compiler_generated, etc.
|
||||
UNIQUE(snapshot_id, method_key)
|
||||
);
|
||||
|
||||
CREATE TABLE cg_edges (
|
||||
snapshot_id BIGINT REFERENCES cg_snapshots(snapshot_id) ON DELETE CASCADE,
|
||||
src_node_id BIGINT REFERENCES cg_nodes(node_id) ON DELETE CASCADE,
|
||||
dst_node_id BIGINT REFERENCES cg_nodes(node_id) ON DELETE CASCADE,
|
||||
kind SMALLINT NOT NULL, -- 0=call,1=newobj,2=dispatch,3=delegate,4=reflection_guess,...
|
||||
PRIMARY KEY(snapshot_id, src_node_id, dst_node_id, kind)
|
||||
);
|
||||
|
||||
CREATE TABLE cg_entrypoints (
|
||||
snapshot_id BIGINT REFERENCES cg_snapshots(snapshot_id) ON DELETE CASCADE,
|
||||
node_id BIGINT REFERENCES cg_nodes(node_id) ON DELETE CASCADE,
|
||||
kind TEXT NOT NULL, -- http, grpc, cli, job, etc.
|
||||
name TEXT NOT NULL, -- GET /foo, "Main", etc.
|
||||
PRIMARY KEY(snapshot_id, node_id, kind, name)
|
||||
);
|
||||
```
|
||||
|
||||
### 2.2 Vuln surface tables (Smart‑Diff artifacts)
|
||||
|
||||
```sql
|
||||
CREATE TABLE vuln_surfaces (
|
||||
surface_id BIGSERIAL PRIMARY KEY,
|
||||
ecosystem TEXT NOT NULL, -- nuget
|
||||
package TEXT NOT NULL,
|
||||
cve_id TEXT NOT NULL,
|
||||
vuln_version TEXT NOT NULL, -- a representative vulnerable version
|
||||
fixed_version TEXT NOT NULL,
|
||||
surface_digest TEXT NOT NULL,
|
||||
created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
|
||||
UNIQUE(ecosystem, package, cve_id, vuln_version, fixed_version)
|
||||
);
|
||||
|
||||
CREATE TABLE vuln_surface_sinks (
|
||||
surface_id BIGINT REFERENCES vuln_surfaces(surface_id) ON DELETE CASCADE,
|
||||
sink_method_key TEXT NOT NULL,
|
||||
reason TEXT NOT NULL, -- changed|added|removed|heuristic
|
||||
PRIMARY KEY(surface_id, sink_method_key)
|
||||
);
|
||||
|
||||
CREATE TABLE vuln_surface_triggers (
|
||||
surface_id BIGINT REFERENCES vuln_surfaces(surface_id) ON DELETE CASCADE,
|
||||
trigger_method_key TEXT NOT NULL,
|
||||
sink_method_key TEXT NOT NULL,
|
||||
internal_path JSONB, -- optional: library internal witness path
|
||||
PRIMARY KEY(surface_id, trigger_method_key, sink_method_key)
|
||||
);
|
||||
```
|
||||
|
||||
### 2.3 Reachability cache & witnesses
|
||||
|
||||
```sql
|
||||
CREATE TABLE reach_findings (
|
||||
finding_id BIGSERIAL PRIMARY KEY,
|
||||
snapshot_id BIGINT REFERENCES cg_snapshots(snapshot_id) ON DELETE CASCADE,
|
||||
cve_id TEXT NOT NULL,
|
||||
ecosystem TEXT NOT NULL,
|
||||
package TEXT NOT NULL,
|
||||
package_version TEXT NOT NULL,
|
||||
reachable BOOLEAN NOT NULL,
|
||||
reachable_entrypoints INT NOT NULL DEFAULT 0,
|
||||
updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
|
||||
UNIQUE(snapshot_id, cve_id, package, package_version)
|
||||
);
|
||||
|
||||
CREATE TABLE reach_witnesses (
|
||||
witness_id BIGSERIAL PRIMARY KEY,
|
||||
finding_id BIGINT REFERENCES reach_findings(finding_id) ON DELETE CASCADE,
|
||||
entry_node_id BIGINT REFERENCES cg_nodes(node_id),
|
||||
dsse_envelope JSONB NOT NULL,
|
||||
created_at TIMESTAMPTZ NOT NULL DEFAULT now()
|
||||
);
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## 3) Stable identity: MethodKey + IL hash
|
||||
|
||||
### 3.1 MethodKey (must be stable across builds)
|
||||
|
||||
Use a normalized string like:
|
||||
|
||||
```
|
||||
{AssemblyName}|{DeclaringTypeFullName}|{MethodName}`{GenericArity}({ParamType1},{ParamType2},...)
|
||||
```
|
||||
|
||||
Examples:
|
||||
|
||||
* `MyApp|BillingController|Pay(System.String)`
|
||||
* `LibXYZ|LibXYZ.Parser|Parse(System.ReadOnlySpan<System.Byte>)`
|
||||
|
||||
### 3.2 Normalized IL hash (for smart-diff + incremental graph updates)
|
||||
|
||||
Raw IL bytes aren’t stable (metadata tokens change). Normalize:
|
||||
|
||||
* opcode names
|
||||
* branch targets by *instruction index*, not offset
|
||||
* method operands by **resolved MethodKey**
|
||||
* string operands by literal or hashed literal
|
||||
* type operands by full name
|
||||
|
||||
Then hash `SHA256(normalized_bytes)`.
|
||||
|
||||
---
|
||||
|
||||
## 4) Call graph extraction for .NET (concrete, doable)
|
||||
|
||||
### Tooling choice
|
||||
|
||||
Start with **Mono.Cecil** (MIT license, easy IL traversal). You can later swap to `System.Reflection.Metadata` for speed.
|
||||
|
||||
### 4.1 Build process (Scanner.Worker)
|
||||
|
||||
1. `dotnet restore` (use your locked restore)
|
||||
2. `dotnet build -c Release /p:DebugType=portable /p:DebugSymbols=true`
|
||||
3. Collect:
|
||||
|
||||
* app assemblies: `bin/Release/**/publish/*.dll` or build output
|
||||
* `.pdb` files for sequence points (file/line for witnesses)
|
||||
|
||||
### 4.2 Cecil loader
|
||||
|
||||
```csharp
|
||||
var rp = new ReaderParameters {
|
||||
ReadSymbols = true,
|
||||
SymbolReaderProvider = new PortablePdbReaderProvider()
|
||||
};
|
||||
|
||||
var asm = AssemblyDefinition.ReadAssembly(dllPath, rp);
|
||||
```
|
||||
|
||||
### 4.3 Node extraction (methods)
|
||||
|
||||
Walk all types, including nested:
|
||||
|
||||
```csharp
|
||||
IEnumerable<TypeDefinition> AllTypes(ModuleDefinition m)
|
||||
{
|
||||
var stack = new Stack<TypeDefinition>(m.Types);
|
||||
while (stack.Count > 0)
|
||||
{
|
||||
var t = stack.Pop();
|
||||
yield return t;
|
||||
foreach (var nt in t.NestedTypes) stack.Push(nt);
|
||||
}
|
||||
}
|
||||
|
||||
foreach (var type in AllTypes(asm.MainModule))
|
||||
foreach (var method in type.Methods)
|
||||
{
|
||||
var key = MethodKey.From(method); // your normalizer
|
||||
var (file, line) = PdbFirstSequencePoint(method);
|
||||
var ilHash = method.HasBody ? ILFingerprint(method) : null;
|
||||
|
||||
// store node (method_key, file, line, il_hash, flags...)
|
||||
}
|
||||
```
|
||||
|
||||
### 4.4 Edge extraction (direct calls)
|
||||
|
||||
```csharp
|
||||
foreach (var method in type.Methods.Where(m => m.HasBody))
|
||||
{
|
||||
var srcKey = MethodKey.From(method);
|
||||
foreach (var ins in method.Body.Instructions)
|
||||
{
|
||||
if (ins.Operand is MethodReference mr)
|
||||
{
|
||||
if (ins.OpCode.Code is Code.Call or Code.Callvirt or Code.Newobj)
|
||||
{
|
||||
var dstKey = MethodKey.From(mr); // important: stable even if not resolved
|
||||
edges.Add(new Edge(srcKey, dstKey, kind: CallKind.Direct));
|
||||
}
|
||||
if (ins.OpCode.Code is Code.Ldftn or Code.Ldvirtftn)
|
||||
{
|
||||
// delegate capture (handle later)
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## 5) Advanced precision: dynamic dispatch + DI + async/await
|
||||
|
||||
If you stop at direct edges only, you’ll miss many real paths.
|
||||
|
||||
### 5.1 Async/await mapping (critical for readable witnesses)
|
||||
|
||||
Async methods compile into a state machine `MoveNext()`. You want edges attributed back to the original method.
|
||||
|
||||
In Cecil:
|
||||
|
||||
* Check `AsyncStateMachineAttribute` on a method
|
||||
* It references a state machine type
|
||||
* Find that type’s `MoveNext` method
|
||||
* Map `MoveNextKey -> OriginalMethodKey`
|
||||
|
||||
Then, while extracting edges:
|
||||
|
||||
```csharp
|
||||
srcKey = MoveNextToOriginal.TryGetValue(srcKey, out var original) ? original : srcKey;
|
||||
```
|
||||
|
||||
Do the same for iterator state machines.
|
||||
|
||||
### 5.2 Virtual/interface dispatch (CHA/RTA)
|
||||
|
||||
You need 2 maps:
|
||||
|
||||
1. **type hierarchy / interface impl map**
|
||||
2. **override map** from “declared method” → “implementation method(s)”
|
||||
|
||||
**Build override map**
|
||||
|
||||
```csharp
|
||||
// For each method, Cecil exposes method.Overrides for explicit implementations.
|
||||
overrideMap[MethodKey.From(overrideRef)] = MethodKey.From(methodDef);
|
||||
```
|
||||
|
||||
**CHA**: for callvirt to virtual method `T.M`, add edges to overrides in derived classes
|
||||
**RTA**: restrict to derived classes that are actually instantiated.
|
||||
|
||||
How to get instantiated types:
|
||||
|
||||
* look for `newobj` instructions and add the created type to `InstantiatedTypes`
|
||||
* plus DI registrations (below)
|
||||
|
||||
### 5.3 DI hints (Microsoft.Extensions.DependencyInjection)
|
||||
|
||||
You will see calls like:
|
||||
|
||||
* `ServiceCollectionServiceExtensions.AddTransient<TService, TImpl>(...)`
|
||||
|
||||
In IL these are generic method calls. Detect and record `TService -> TImpl` as “instantiated”. This massively improves RTA for modern .NET apps.
|
||||
|
||||
### 5.4 Delegates/lambdas (good enough approach)
|
||||
|
||||
Implement intraprocedural tracking:
|
||||
|
||||
* when you see `ldftn SomeMethod` then `newobj Action::.ctor` then `stloc.s X`
|
||||
* store `delegateTargets[local X] += SomeMethod`
|
||||
* when you see `ldloc.s X` and later `callvirt Invoke`, add edges to targets
|
||||
|
||||
This makes Minimal API entrypoint discovery work too.
|
||||
|
||||
### 5.5 Reflection (best-effort)
|
||||
|
||||
Implement only high-signal heuristics:
|
||||
|
||||
* `typeof(T).GetMethod("Foo")` with constant "Foo"
|
||||
* `GetType().GetMethod("Foo")` with constant "Foo" (type unknown → mark uncertain)
|
||||
|
||||
If resolved, add edge with `kind=reflection_guess`.
|
||||
If not, set node flag `has_reflection = true` and in results show “may be incomplete”.
|
||||
|
||||
---
|
||||
|
||||
## 6) Entrypoint detection (concrete detectors)
|
||||
|
||||
### 6.1 MVC controllers
|
||||
|
||||
Detect:
|
||||
|
||||
* types deriving from `Microsoft.AspNetCore.Mvc.ControllerBase`
|
||||
* methods:
|
||||
|
||||
* public
|
||||
* not `[NonAction]`
|
||||
* has `[HttpGet]`, `[HttpPost]`, `[Route]` etc.
|
||||
|
||||
Extract route template from attributes’ ctor arguments.
|
||||
|
||||
Store in `cg_entrypoints`:
|
||||
|
||||
* kind = `http`
|
||||
* name = `GET /billing/pay` (compose verb+template)
|
||||
|
||||
### 6.2 Minimal APIs
|
||||
|
||||
Scan `Program.Main` IL:
|
||||
|
||||
* find calls to `MapGet`, `MapPost`, ...
|
||||
* extract route string from preceding `ldstr`
|
||||
* resolve handler method via delegate tracking (ldftn)
|
||||
|
||||
Entry:
|
||||
|
||||
* kind = `http`
|
||||
* name = `GET /foo`
|
||||
|
||||
### 6.3 CLI
|
||||
|
||||
Find assembly entry point method (`asm.EntryPoint`) or `static Main`.
|
||||
Entry:
|
||||
|
||||
* kind = `cli`
|
||||
* name = `Main`
|
||||
|
||||
Start here. Add gRPC/jobs later.
|
||||
|
||||
---
|
||||
|
||||
## 7) Smart-Diff SurfaceBuilder (the “advanced” part)
|
||||
|
||||
This is what makes your reachability actually meaningful for CVEs.
|
||||
|
||||
### 7.1 SurfaceBuilder inputs
|
||||
|
||||
From your vuln ingestion pipeline:
|
||||
|
||||
* ecosystem = nuget
|
||||
* package = `LibXYZ`
|
||||
* affected range = `<= 1.2.3`
|
||||
* fixed version = `1.2.4`
|
||||
* CVE id
|
||||
|
||||
### 7.2 Choose a vulnerable version to diff
|
||||
|
||||
Pick the **highest affected version below fixed**.
|
||||
|
||||
* fixed = 1.2.4
|
||||
* vulnerable representative = 1.2.3
|
||||
|
||||
(If multiple fixed versions exist, build multiple surfaces.)
|
||||
|
||||
### 7.3 Download both packages
|
||||
|
||||
Use NuGet.Protocol to download `.nupkg`, unzip, pick TFMs you care about (often `netstandard2.0` is safest). Compute fingerprints for each assembly.
|
||||
|
||||
### 7.4 Compute method fingerprints
|
||||
|
||||
For each method:
|
||||
|
||||
* MethodKey
|
||||
* Normalized IL hash
|
||||
|
||||
### 7.5 Diff
|
||||
|
||||
```
|
||||
ChangedMethods = { k | hashVuln[k] != hashFixed[k] } ∪ added ∪ removed
|
||||
```
|
||||
|
||||
Store these as `vuln_surface_sinks` with reason.
|
||||
|
||||
### 7.6 Build internal library call graph
|
||||
|
||||
Same Cecil extraction, but only for package assemblies.
|
||||
Now compute triggers:
|
||||
|
||||
**Reverse BFS from sinks**:
|
||||
|
||||
* Start from all sink method keys
|
||||
* Walk predecessors
|
||||
* When you encounter a **public/exported method**, record it as a trigger
|
||||
|
||||
Also store one internal path for each trigger → sink (for witnesses).
|
||||
|
||||
### 7.7 Add interface/base declarations as triggers
|
||||
|
||||
Important: your app might call a library via an interface method signature, not the concrete implementation.
|
||||
|
||||
For each trigger implementation method:
|
||||
|
||||
* for each `method.Overrides` entry, add the overridden method key as an additional trigger
|
||||
|
||||
This reduces dependence on perfect dispatch expansion during app scanning.
|
||||
|
||||
### 7.8 Persist the surface
|
||||
|
||||
Store:
|
||||
|
||||
* sinks set
|
||||
* triggers set
|
||||
* internal witness paths (optional but highly valuable)
|
||||
|
||||
Now you’ve converted a “version range” CVE into “these specific library APIs are dangerous”.
|
||||
|
||||
---
|
||||
|
||||
## 8) Reachability engine (fast, witness-producing)
|
||||
|
||||
### 8.1 In-memory graph format (CSR)
|
||||
|
||||
Don’t BFS off dictionaries; you’ll die on perf.
|
||||
|
||||
Build integer indices:
|
||||
|
||||
* `method_key -> nodeIndex (0..N-1)`
|
||||
* store arrays:
|
||||
|
||||
* `predOffsets[N+1]`
|
||||
* `preds[edgeCount]`
|
||||
|
||||
Construction:
|
||||
|
||||
1. count predecessors per node
|
||||
2. prefix sum to offsets
|
||||
3. fill preds
|
||||
|
||||
### 8.2 Reverse BFS from sinks
|
||||
|
||||
This computes:
|
||||
|
||||
* `visited[node]` = can reach a sink
|
||||
* `parent[node]` = next node toward a sink (for path reconstruction)
|
||||
|
||||
```csharp
|
||||
public sealed class ReachabilityEngine
|
||||
{
|
||||
public ReachabilityResult Compute(
|
||||
Graph g,
|
||||
ReadOnlySpan<int> entrypoints,
|
||||
ReadOnlySpan<int> sinks)
|
||||
{
|
||||
var visitedMark = g.VisitMark; // int[] length N (reused across runs)
|
||||
var parent = g.Parent; // int[] length N (reused)
|
||||
g.RunId++;
|
||||
|
||||
var q = new IntQueue(capacity: g.NodeCount);
|
||||
var sinkSet = new BitSet(g.NodeCount);
|
||||
foreach (var s in sinks)
|
||||
{
|
||||
sinkSet.Set(s);
|
||||
visitedMark[s] = g.RunId;
|
||||
parent[s] = s;
|
||||
q.Enqueue(s);
|
||||
}
|
||||
|
||||
while (q.TryDequeue(out var v))
|
||||
{
|
||||
var start = g.PredOffsets[v];
|
||||
var end = g.PredOffsets[v + 1];
|
||||
for (int i = start; i < end; i++)
|
||||
{
|
||||
var p = g.Preds[i];
|
||||
if (visitedMark[p] == g.RunId) continue;
|
||||
visitedMark[p] = g.RunId;
|
||||
parent[p] = v;
|
||||
q.Enqueue(p);
|
||||
}
|
||||
}
|
||||
|
||||
// Collect reachable entrypoints and paths
|
||||
var results = new List<EntryWitness>();
|
||||
foreach (var e in entrypoints)
|
||||
{
|
||||
if (visitedMark[e] != g.RunId) continue;
|
||||
var path = ReconstructPath(e, parent, sinkSet);
|
||||
results.Add(new EntryWitness(e, path));
|
||||
}
|
||||
|
||||
return new ReachabilityResult(results);
|
||||
}
|
||||
|
||||
private static int[] ReconstructPath(int entry, int[] parent, BitSet sinks)
|
||||
{
|
||||
var path = new List<int>(32);
|
||||
int cur = entry;
|
||||
path.Add(cur);
|
||||
|
||||
// follow parent pointers until a sink
|
||||
for (int guard = 0; guard < 10_000; guard++)
|
||||
{
|
||||
if (sinks.Get(cur)) break;
|
||||
var nxt = parent[cur];
|
||||
if (nxt == cur || nxt < 0) break; // safety
|
||||
cur = nxt;
|
||||
path.Add(cur);
|
||||
}
|
||||
return path.ToArray();
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### 8.3 Producing the witness
|
||||
|
||||
For each node index in the path:
|
||||
|
||||
* method_key
|
||||
* file_path / line_start (if known)
|
||||
* optional flags (reflection_guess edge, dispatch edge)
|
||||
|
||||
Then attach:
|
||||
|
||||
* vuln id, package, version
|
||||
* entrypoint kind/name
|
||||
* graph digest + config digest
|
||||
* surface digest
|
||||
* timestamp
|
||||
|
||||
Send JSON to Attestor for DSSE signing, store envelope in Authority.
|
||||
|
||||
---
|
||||
|
||||
## 9) Scaling: don’t do BFS 500 times if you can avoid it
|
||||
|
||||
### 9.1 First-line scaling (usually enough)
|
||||
|
||||
* Group vulnerabilities by package/version → surfaces reused
|
||||
* Only run reachability for vulns where:
|
||||
|
||||
* dependency present AND
|
||||
* surface exists OR fallback mode
|
||||
* Limit witnesses per vuln (top 3)
|
||||
|
||||
In practice, with N~50k nodes and E~200k edges, a reverse BFS is fast in C# if done with arrays.
|
||||
|
||||
### 9.2 Incremental Smart-Diff × Reachability (your “low noise” killer feature)
|
||||
|
||||
#### Step A: compute graph delta between snapshots
|
||||
|
||||
Use `il_hash` per method to detect changed nodes:
|
||||
|
||||
* added / removed / changed nodes
|
||||
* edges updated only for changed nodes
|
||||
|
||||
#### Step B: decide which vulnerabilities need recompute
|
||||
|
||||
Store a cached reverse-reachable set per vuln surface if you want (bitset), OR just do a cheaper heuristic:
|
||||
|
||||
Recompute for vulnerability if:
|
||||
|
||||
* sink set changed (new surface or version changed), OR
|
||||
* any changed node is on any previously stored witness path, OR
|
||||
* entrypoints changed, OR
|
||||
* impacted nodes touch any trigger node’s predecessors (use a small localized search)
|
||||
|
||||
A practical approach:
|
||||
|
||||
* store all node IDs that appear in any witness path for that vuln
|
||||
* if delta touches any of those nodes/edges, recompute
|
||||
* otherwise reuse cached result
|
||||
|
||||
This yields a massive win on PR scans where most code is unchanged.
|
||||
|
||||
#### Step C: “Impact frontier” recompute (optional)
|
||||
|
||||
If you want more advanced:
|
||||
|
||||
* compute `ImpactSet = ΔNodes ∪ endpoints(ΔEdges)`
|
||||
* run reverse BFS **starting from ImpactSet ∩ ReverseReachSet** and update visited marks
|
||||
This is trickier to implement correctly (dynamic graph), so I’d ship the heuristic first.
|
||||
|
||||
---
|
||||
|
||||
## 10) Practical fallback modes (don’t block shipping)
|
||||
|
||||
You won’t have surfaces for every CVE on day 1. Handle this gracefully:
|
||||
|
||||
### Mode 1: Surface-based reachability (best)
|
||||
|
||||
* sink = trigger methods from surface
|
||||
* result: “reachable” with path
|
||||
|
||||
### Mode 2: Package API usage (good fallback)
|
||||
|
||||
* sink = *any* method in that package that is called by app
|
||||
* result: “package reachable” (lower confidence), still provide path to callsite
|
||||
|
||||
### Mode 3: Dependency present only (SBOM level)
|
||||
|
||||
* no call graph needed
|
||||
* result: “present” only
|
||||
|
||||
Your UI can show confidence tiers:
|
||||
|
||||
* **Confirmed reachable (surface)**
|
||||
* **Likely reachable (package API)**
|
||||
* **Present only (SBOM)**
|
||||
|
||||
---
|
||||
|
||||
## 11) Integration points inside Stella Ops
|
||||
|
||||
### Scanner.Worker (per build)
|
||||
|
||||
1. Build/collect assemblies + pdb
|
||||
2. `CallGraphBuilder` → nodes/edges/entrypoints + graph_digest
|
||||
3. Load SBOM vulnerabilities list
|
||||
4. For each vuln:
|
||||
|
||||
* resolve surface triggers; if missing → enqueue SurfaceBuilder job + fallback mode
|
||||
* run reachability BFS
|
||||
* for each reachable entrypoint: emit DSSE witness
|
||||
5. Persist findings/witnesses
|
||||
|
||||
### SurfaceBuilder (async worker)
|
||||
|
||||
* triggered by “surface missing” events or nightly preload of top packages
|
||||
* computes surface once, stores forever
|
||||
|
||||
### Authority
|
||||
|
||||
* stores graphs, surfaces, findings, witnesses
|
||||
* provides retrieval APIs for UI/CI
|
||||
|
||||
---
|
||||
|
||||
## 12) What to implement first (in the order that produces value fastest)
|
||||
|
||||
### Week 1–2 scope (realistic, shippable)
|
||||
|
||||
1. Cecil call graph extraction (direct calls)
|
||||
2. MVC + Minimal API entrypoints
|
||||
3. Reverse BFS reachability with path witnesses
|
||||
4. DSSE witness signing + storage
|
||||
5. SurfaceBuilder v1:
|
||||
|
||||
* IL hash per method
|
||||
* changed methods as sinks
|
||||
* triggers via internal reverse BFS
|
||||
6. UI: “Show Witness” + “Verify Signature”
|
||||
|
||||
### Next increment (precision upgrades)
|
||||
|
||||
7. async/await mapping to original methods
|
||||
8. RTA + DI registration hints
|
||||
9. delegate tracking for Minimal API handlers (if not already)
|
||||
10. interface override triggers in surface builder
|
||||
|
||||
### Later (if you want “attackability”, not just “reachability”)
|
||||
|
||||
11. taint/dataflow for top sink classes (deserialization, path traversal, SQL, command exec)
|
||||
12. sanitizer modeling & parameter constraints
|
||||
|
||||
---
|
||||
|
||||
## 13) Common failure modes and how to harden
|
||||
|
||||
### MethodKey mismatches (surface vs app call)
|
||||
|
||||
* Ensure both are generated from the same normalization rules
|
||||
* For generic methods, prefer **definition** keys (strip instantiation)
|
||||
* Store both “exact” and “erased generic” variants if needed
|
||||
|
||||
### Multi-target frameworks
|
||||
|
||||
* SurfaceBuilder: compute triggers for each TFM, union them
|
||||
* App scan: choose TFM closest to build RID, but allow fallback to union
|
||||
|
||||
### Huge graphs
|
||||
|
||||
* Drop `System.*` nodes/edges unless:
|
||||
|
||||
* the vuln is in System.* (rare, but handle separately)
|
||||
* Deduplicate nodes by MethodKey across assemblies where safe
|
||||
* Use CSR arrays + pooled queues
|
||||
|
||||
### Reflection heavy projects
|
||||
|
||||
* Mark analysis confidence lower
|
||||
* Include “unknown edges present” in finding metadata
|
||||
* Still produce a witness path up to the reflective callsite
|
||||
|
||||
---
|
||||
|
||||
If you want, I can also paste a **complete Cecil-based CallGraphBuilder class** (nodes+edges+PDB lines), plus the **SurfaceBuilder** that downloads NuGet packages and generates `vuln_surface_triggers` end-to-end.
|
||||
Reference in New Issue
Block a user