test(core,docs): M3.5 — sandbox attack-vector test suite + security-model.md

Closes the "M3.5: 75% — missing attack vectors" gap from the morning report.

  · packages/core/src/sandbox/attacks.test.ts (17 tests)
    - 6 SBPL hostile-input tests: paren/quote/backslash escaping,
      deny-after-allow ordering, no implicit network when allowedDomains=[],
      no implicit writes to /usr|/System|/Library.
    - 3 bwrap arg safety tests: no --share-net, only cwd is bare --bind,
      pid/ipc/uts always unshared.
    - 4 excluded-command spoofing tests: prefix-only doesn't bypass; pipeline
      after-excluded DOES bypass (documented as known M5.2-tracked behavior).
    - 2 sandbox-exec e2e tests on macOS: block /usr/local/bin write; profile
      parses without syntax error (smoke).
    - 2 bwrap e2e tests on Linux: block outside-cwd write; DNS unshared when
      allowedDomains=[].

  · packages/core/src/sandbox/profile.ts hardened so e2e tests pass:
    - Add `(allow file-read* (literal "/"))` and related (literal "/private")
      entries so shell getcwd / parent stat succeed under deny-default.
    - Add `(allow file-read* (subpath "/private/var/folders"))` for dyld
      closure cache (without this, /bin/sh exited with SIGABRT before any
      command could run).
    - Add `(allow process-info*)`.

  · docs/security-model.md (NEW, ~180 lines):
    threat model, defence layers (trust → modes → permissions → sandbox →
    plugin subprocess → credentials), hostile-input handling, attack-vector
    test inventory, explicit list of known gaps (DNS exfil, OS-wrap of plugin
    process, pipeline analysis, domain whitelist) with milestone tracking.

Tests: 308/10 pass/skip in core (was 293), 41 in cli unchanged. Total 349 passing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: oratis

docs/security-model.md

@@ -0,0 +1,180 @@
+# DeepCode Security Model
+
+> Last updated: 2026-05-28 (M3.5 hardening + attack-vector test suite landed)
+
+This document is the **single source of truth** for what DeepCode protects
+against, what it doesn't, and how each layer composes. If you're reviewing a
+PR that touches credentials, sandbox, plugin runtime, or hooks — verify it
+against the threat model here.
+
+## Threat model
+
+DeepCode is an LLM-driven coding assistant. The threats we care about, in
+decreasing order of operator severity:
+
+| # | Threat                                                                   | Severity | Where mitigated         |
+| - | ------------------------------------------------------------------------ | -------- | ----------------------- |
+| 1 | Model exfiltrates DeepSeek API key (or other env secrets) via tool call  | High     | M3.5 sandbox + M5.1 env strip |
+| 2 | Model writes arbitrary files outside the project (`/usr/bin`, `/etc`)    | High     | M3.5 sandbox + permissions |
+| 3 | Plugin (third-party code) does either #1 or #2                           | High     | M5.1 subprocess + (M5.1-ext) OS sandbox |
+| 4 | Hook script (third-party shell snippet) does either #1 or #2             | Medium   | M3.5 sandbox wraps Bash; hooks bypass when invoked via /bin/sh directly |
+| 5 | Hostile `settings.json` field (e.g. allowRead path) injects sandbox rule | Medium   | escapeSbpl()             |
+| 6 | Untrusted project's AGENTS.md drives the agent into harmful action       | Low      | Trust store (`/trust`)   |
+| 7 | DNS exfiltration of secrets from sandboxed Bash                          | Acknowledged limitation | M3.5-ext userspace proxy |
+
+## Defence layers
+
+### Layer 0 — Trust store
+
+First time DeepCode opens a folder, you're asked **"Do you trust this
+directory?"**. If you say no, the agent runs in a heavily restricted mode:
+no exec, no writes outside the project, no `bypassPermissions` mode allowed.
+
+Decisions persist in `~/.deepcode/trust.json`.
+
+### Layer 1 — Mode + Permissions
+
+Every tool call goes through:
+
+```
+  Mode policy → Permission rules → Sandbox wrap → Exec
+```
+
+Modes (`default` | `acceptEdits` | `plan` | `auto` | `dontAsk` | `bypassPermissions`):
+- `plan` blocks all writes and exec (read/grep/glob only).
+- `default` prompts for risky operations.
+- `bypassPermissions` is gated behind the trust store.
+
+Permission rules in `settings.json` are evaluated in order: deny > ask > allow.
+4 glob patterns are supported per rule (read/write/edit/exec). See
+`packages/core/src/config/permissions.ts`.
+
+### Layer 2 — Sandbox (M3.5)
+
+Bash tool invocations are wrapped under platform sandbox when
+`settings.sandbox.enabled` is `true`.
+
+**macOS — `sandbox-exec` + SBPL profile**
+
+Profile is generated dynamically per invocation (`buildMacOsProfile`) and
+written to `$TMPDIR/deepcode-sb-*.sb`. Policy:
+
+- **Default-deny** on file-read, file-write, and most other operations.
+- Allowed reads: `/usr`, `/System`, `/Library`, `/private/etc`,
+  `/private/var/db`, `/private/var/folders` (dyld closure), `/bin`, `/sbin`,
+  `/opt`, `/dev`, `~/.config`, `~/.npm`, `~/.cache`. Plus user-provided
+  `filesystem.allowRead` paths.
+- Path traversal: explicit `(literal "/")` and `(literal "/private")`
+  entries so `getcwd()` and parent stats work.
+- Allowed writes: `/private/tmp`, `/private/var/folders`. Plus user-provided
+  `filesystem.allowWrite` (also implicitly readable).
+- `denyRead` / `denyWrite` rules appended LAST so they override allows on
+  overlap.
+- Network: default-allow unless `network.allowedDomains: []` (empty array)
+  meaning "no network". Domain whitelist needs M3.5-ext (userspace proxy).
+- Unix sockets: blocked unless `network.allowUnixSockets: true`.
+
+**Linux — `bwrap` argv**
+
+Generated by `buildLinuxBwrapArgs`:
+
+- System read-only mounts: `/usr`, `/lib`, `/lib64`, `/bin`, `/sbin`, `/etc`
+  (`--ro-bind-try`).
+- `/proc`, `/dev`, `/tmp` (tmpfs).
+- cwd is the only bare `--bind` (rw).
+- Always `--unshare-pid`, `--unshare-ipc`, `--unshare-uts`.
+- `--unshare-net` when `network.allowedDomains: []`.
+
+**Windows — not supported.** Sandbox is a no-op (see plan §0.2).
+
+**Excluded commands** — `git` is excluded by default. The match is on the
+leading whitespace-bounded token of the user command. Pipelines starting with
+an excluded command DO bypass — this is documented behavior pinned by a test,
+not an oversight. (M5.2 will add per-clause analysis.)
+
+### Layer 3 — Plugin subprocess (M5.1)
+
+Plugins run in their own `node` subprocess with:
+
+- **No host fs/net access** in plugin code — all capabilities (`fs_read`,
+  `fs_write`, `bash`, `fetch`) flow via JSON-RPC over stdio back to the host,
+  which applies its own mode/permission/sandbox stack.
+- **Token-protected RPC** — host generates an unguessable token per plugin
+  spawn; every RPC from the plugin must include it.
+- **Env scrub** — `DEEPSEEK_API_KEY` and `DEEPSEEK_AUTH_TOKEN` are stripped
+  from the child env. Plugins cannot read DeepSeek credentials.
+- **Hash pin** — plugin code is SHA-256 hashed at install time; mismatch on
+  load fails open (drift detection).
+
+**Acknowledged gaps**:
+- The subprocess isn't itself sandbox-wrapped at the OS level yet. A
+  malicious plugin can still exfil via DNS, can read other files the host
+  process can read (e.g. `~/.deepcode/credentials.json`). M5.1-ext closes
+  this by spawning the plugin under `sandbox-exec`/`bwrap` too.
+- A plugin can still `process.exit(N)` to crash the host's plugin pool. Host
+  restarts on next launch.
+
+### Layer 4 — Credentials
+
+- API key stored in `~/.deepcode/credentials.json` with `chmod 600`.
+- `apiKeyHelper` field can point at an OS keychain wrapper; output is cached
+  for 5 min (`ApiKeyHelperRefresher`, configurable via
+  `DEEPCODE_API_KEY_HELPER_TTL_MS`).
+- `/doctor` redacts the loaded key in its output (`sk-…` truncated).
+
+## Hostile-input handling
+
+The SBPL profile builder treats every user-controlled string (allowRead paths
+etc.) as **untrusted**. We:
+
+1. Escape backslash and double-quote before embedding into a quoted SBPL
+   subpath literal (`escapeSbpl`).
+2. Apply `(deny ...)` rules AFTER `(allow ...)` so a deny always wins on
+   overlap.
+3. Test injection attempts in `packages/core/src/sandbox/attacks.test.ts` —
+   try to inject `)\n(allow file-write* (subpath "/"))` etc., verify the
+   resulting profile doesn't standalone-allow root writes.
+
+## Attack-vector test suite
+
+`packages/core/src/sandbox/attacks.test.ts` contains 17 tests:
+
+- **6 unit-level** "hostile input → safe output" tests:
+  - SBPL paren/quote escaping
+  - SBPL backslash escaping
+  - deny-after-allow ordering
+  - no implicit network when allowedDomains is empty
+  - no implicit file-write to /usr, /System, /Library
+- **3 bwrap-arg safety** tests:
+  - no --share-net even with non-empty allowedDomains (until M3.5-ext)
+  - only cwd is bare --bind
+  - always --unshare-{pid,ipc,uts}
+- **4 excluded-command spoofing** tests:
+  - prefix-only match (`gitleaks`) does NOT bypass
+  - exact match bypasses
+  - leading-token match bypasses
+  - pipeline-after-excluded bypasses (documented behavior; M5.2 hardens)
+- **2 sandbox-exec e2e** (macOS, runIf the binary exists):
+  - block write to `/usr/local/bin/*`
+  - profile is syntactically valid (smoke)
+- **2 bwrap e2e** (Linux, runIf the binary exists):
+  - block write outside cwd
+  - DNS unshared when allowedDomains: []
+
+## What we do NOT yet protect against
+
+| Gap                                                | Tracking             |
+| -------------------------------------------------- | -------------------- |
+| DNS exfil from sandboxed Bash                      | M3.5-ext (UDP proxy) |
+| OS sandbox wrapping the plugin subprocess          | M5.1-ext             |
+| Pipeline analysis (`git ... && rm -rf /`)          | M5.2                 |
+| Domain whitelist enforcement (allowedDomains)      | M3.5-ext             |
+| Image input prompt injection (model multimodal)    | v1.1                 |
+| Side-channel timing leaks (e.g. via exec duration) | Out of scope         |
+| Local malicious binaries already on $PATH          | Out of scope (assume host is trusted) |
+
+## How to file a security issue
+
+1. Do NOT open a public GitHub issue.
+2. Email security@<TBD>.dev with reproduction steps + commit SHA.
+3. We aim to triage within 72 hours.