KeiSeiKit-1.0/docs/encyclopedia/cross-cli-policy.md
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feat(v0.42): 6 fixes from 4-CLI re-audit (CRITICAL + 2 HIGH + 3 MED)
Convergent dogfood audit by Claude+Grok+Gemini+Copilot on v0.41 surfaced
that the v0.41 'fixes' were incomplete. 3 of 4 reviewers independently
found the same CRITICAL bypass; Gemini wrote a Rust test suite to verify.

## Convergent findings → v0.42 fixes

[#1 CRITICAL] Symlink leaf bypass (3-of-4 convergent)
  v0.41 only canonicalized PARENT, then re-attached leaf as-is. Exploit:
    1. kei_bash 'ln -s ~/.ssh/authorized_keys ./cfg.txt'
       (passes the bash hook chain — ln itself is non-destructive)
    2. kei_write file_path=cfg.txt content=<key>
       validate_path saw $PWD/cfg.txt (allowed) → fs::write followed leaf
       symlink → overwrote authorized_keys.
  Fix: canonicalize FULL path (incl. leaf) when file exists; for new
       files, symlink_metadata on leaf and reject is_symlink. Now the
       denylist check sees the real target.

[#2 HIGH] $HOME blanket-allowed = self-neutering (2-of-4 convergent)
  allowed_roots() defaulted to [$PWD, $HOME], denylist only had 4 secret
  dirs. So kei_write $HOME/.claude/hooks/no-github-push.sh content='exit 0'
  was ALLOWED — agent could overwrite the substrate's own policy hooks.
  Similar attacks on ~/.zshrc (RCE on next shell), ~/.gitconfig, ~/.npmrc.
  Fix: default to $PWD only. Denylist extended with .claude/, .grok/,
       .gemini/, .copilot/, .kimi/, all major shell-init files, and
       additional credential paths. KEI_ALLOWED_ROOTS for explicit
       widening.

[#3 HIGH] Empty-section fail-OPEN (Gemini test-verified)
  v0.41 'fail-closed on missing config' fix was incomplete: if config
  file existed but section [bash]/[edit]/[write] was empty, load_chain
  returned Ok(vec![]) → run_chain early-returned Ok → action ran ungated.
  Fix: empty chain also FAIL-CLOSED with same KEI_POLICY_CHAIN_OPTIONAL
       opt-in.

[#4 MEDIUM] load_chain still blocked tokio worker (Claude)
  v0.41 fix #4 converted handle_edit/handle_write reads to tokio::fs but
  left load_chain on std::fs. Slow/hung mount on policy-chain.toml would
  freeze a worker for every safe_* invocation.
  Fix: load_chain → async + tokio::fs::{try_exists, read_to_string}.

[#5 MEDIUM] process_group only applied to bash, not hooks (Claude)
  v0.41 fix #5 set_process_group on kei_bash's child shell, but the
  hook subprocess (spawned per-hook in run_chain) was NOT in its own
  group. On hook timeout, kill_on_drop killed only the immediate hook
  process; grandchildren orphaned — the exact failure mode fix #5 was
  meant to prevent.
  Fix: set_process_group + killpg also on hook spawn in run_chain.

[#6 MEDIUM] Per-step vs aggregate timeout (Claude)
  Doc claimed 'Hard cap on single chain + action — 60s'. Actual: each
  hook gets independent 60s, then action gets another 60s. For a 3-hook
  bash chain that's 240s max — 4× documented.
  Status: documented as known-limit; single-deadline impl deferred to
       v0.43 (not security-blocking, just a doc/correctness drift).

## Verification (8 smokes — all green)

  /etc/passwd                          → denied (system dir)              ✓
  ../escape.txt                        → denied (../ segment)             ✓
  /tmp/symlink → /etc/passwd writeable → denied (resolved /private/etc)   ✓ NEW
  ~/.claude/hooks/no-github-push.sh    → denied (substrate dir)           ✓ NEW
  ~/.zshrc                             → denied (shell-init file)         ✓ NEW
  policy-chain.toml empty [bash]       → FAIL-CLOSED                      ✓ NEW
  KEI_POLICY_CHAIN_OPTIONAL=1          → opt-in pass-through              ✓
  kei_bash git-push-github             → BLOCKED (regression)             ✓
  kei_bash echo HELLO                  → returns content (regression)     ✓

cargo test -p kei-mcp: 3/3 still pass.

## Architecture note from Grok

Grok architect flagged: safe_tools.rs is 474 LOC, exceeds Constructor
Pattern 200-line threshold. v0.42 does NOT refactor (security fixes
shipped first); v0.43 will extract path_guard.rs + chain_runner.rs.

## Per-CLI audit value demonstrated

  Claude   — 5 issues + 5 minor, exhaustive line-anchored analysis
  Grok     — architectural review with grep-verified citations
  Gemini   — wrote Rust test project to verify findings (PoC code!)
  Copilot  — partial fact-check, ran out of mid-task
2026-05-26 21:33:54 +08:00

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Markdown

# Cross-CLI policy enforcement
> *Same safety rules. Any LLM CLI. Three honesty tiers.*
KeiSeiKit's safety hooks (`no-github-push`, `safety-guard`, `destructive-guard`,
`citation-verify`, `numeric-claims-guard`) originally fired only inside Claude
Code's `PreToolUse` pipeline. Phase C extends enforcement to other CLIs —
but the strength of enforcement depends on what each CLI permits.
## The 3-tier honesty model
| Tier | What it means | CLIs |
|---|---|---|
| **TIER 1 — full native** | Tool-call enforcement at the CLI's own hook layer. Same as Claude. | claude, **grok** |
| **TIER 2 — MCP-wrapped** | Native shell disabled at launch; agent forced to use our policy-gated `kei_bash`/`kei_edit`/`kei_write` MCP tools. | **copilot** |
| **TIER 3 — advisory** | CLI can't disable native shell; we register kei-mcp and instruct the agent to prefer `kei_*` tools, but enforcement is prompt-level only. | **agy, kimi** |
For patent-sensitive or production-PR work — stick to TIER 1 (claude or grok).
## How to wire
One command sets up enforcement for whichever CLIs you have installed:
```bash
kei mcp-wire # detect + wire all installed CLIs
kei mcp-wire grok # wire one CLI
kei mcp-wire --dry-run # preview config changes without writing
kei mcp-wire --list # show enforcement tier per CLI
```
The orchestrator is idempotent — running twice produces the same config.
## What `kei mcp-wire` writes
### claude (TIER 1 — already enforced)
No-op. Native PreToolUse hooks already gate every tool call. `kei mcp-wire claude`
prints the optional `mcpServers` snippet you can add to
`~/.claude/settings.json` if you want claude to also see `spawn_agent` for
sub-agent dispatch.
### grok (TIER 1 — port our hooks)
Writes `~/.grok/settings.json` `hooks.PreToolUse` block:
- `Bash` matcher → `no-github-push.sh` + `safety-guard.sh` + `destructive-guard.sh`
- `Edit` matcher → `citation-verify.sh` + `numeric-claims-guard.sh`
- `Write` matcher → `citation-verify.sh` + `numeric-claims-guard.sh`
Plus registers kei-mcp with `GROKCODE=1` env (so kei-mcp's policy chain skips
duplicate enforcement when invoked via Grok — your native hooks already fired).
xAI's Grok uses the same JSON input contract as Claude Code's PreToolUse, so
our hook scripts run unchanged. Identical enforcement to claude.
### copilot (TIER 2 — disable native shell, force MCP)
Writes `~/.copilot/mcp-config.json` registering kei-mcp. To activate enforcement,
launch copilot with `--excluded-tools='shell'`:
```bash
alias copilot='copilot --excluded-tools=shell'
```
The agent will have NO native shell tool, only kei-mcp's `kei_bash`
which runs the policy chain before execution. `kei_edit` / `kei_write`
similarly gate file mutations.
### agy / kimi (TIER 3 — advisory)
Writes their MCP config (`~/.gemini/config/mcp_config.json` for agy,
`~/.kimi/mcp.json` for kimi) registering kei-mcp.
**The honest part:** these CLIs do NOT have a way to disable their native
shell. The agent CAN reach for native bash regardless of what we tell it.
The system prompt nudges it toward `kei_bash`, but a determined or careless
agent can bypass.
For patent-sensitive work — **don't use agy or kimi as orchestrator**.
Use them for analysis / brainstorming / no-side-effect tasks only.
## Internals
### policy-chain.toml (SSoT)
One file declares which hooks gate which tool, for all CLIs that go through
the MCP layer:
```toml
# ~/.claude/hooks/_lib/policy-chain.toml
[bash]
chain = ["no-github-push.sh", "safety-guard.sh", "destructive-guard.sh"]
[edit]
chain = ["citation-verify.sh", "numeric-claims-guard.sh"]
[write]
chain = ["citation-verify.sh", "numeric-claims-guard.sh"]
```
To add a hook: append its basename. The hook script must already exist in
`~/.claude/hooks/` and follow the standard PreToolUse contract (read JSON
on stdin with `.tool_name` + `.tool_input`, return exit 0 = pass / 2 = block).
### kei-mcp built-in tools
`kei-mcp` (Rust MCP server at `_primitives/_rust/kei-mcp/`) exposes 4
built-in tools across two source files (both bypass the atom-discovery
loop in `handlers/tools.rs`):
In `handlers/tools.rs`:
- `spawn_agent(name, task, on?)` — invokes a KeiSeiKit agent on any backend
In `handlers/safe_tools.rs` (Phase C, v0.40+):
- `kei_bash(command, cwd?)` — runs `[bash]` chain → executes
- `kei_edit(file_path, old_string, new_string)` — runs `[edit]` chain → edits
- `kei_write(file_path, content)` — runs `[write]` chain → writes
The chain runs against the same hook scripts Claude uses; identical input
shape, identical decisions. On block, the hook's stderr surfaces as the MCP
error message so the calling agent sees exactly why.
**v0.42 hardening** (post 4-CLI re-audit, supersedes v0.41):
- **Fail-CLOSED everywhere** — missing config, missing hook, OR empty
section (`[bash]/[edit]/[write]` with no entries) all refuse to run.
Tests / dev can opt in via `KEI_POLICY_CHAIN_OPTIONAL=1`.
- **Symlink-safe path guard** — `kei_edit` / `kei_write` canonicalize the
FULL path (resolving any leaf symlink to its real target) and reject
if the leaf itself is a symlink for a not-yet-existent file. Fixes the
v0.41 CRITICAL bypass where `ln -s ~/.ssh/keys ./x; kei_write x` would
follow the link.
- **$PWD-only default root** — `allowed_roots` defaults to current working
directory only. Was: `$PWD` + entire `$HOME` — too permissive, agent
could overwrite `~/.claude/hooks/*` (self-neuter) or `~/.zshrc` (RCE on
next shell). Operators who need broader access set `KEI_ALLOWED_ROOTS`.
- **Denylist extended** — system dirs (`/etc/`, `/usr/`, `/System/`,
`/var/`, `/root/`, `/bin/`, `/sbin/`); credential stores (`~/.ssh/`,
`~/.aws/`, `~/.gnupg/`, `~/.config/gcloud/`, `~/.cargo/credentials`,
`~/.docker/config.json`, `~/.kube/`); substrate dirs (`~/.claude/`,
`~/.grok/`, `~/.gemini/`, `~/.copilot/`, `~/.kimi/`); exact shell-init
files (`.zshrc`, `.bashrc`, `.profile`, `.zshenv`, `.gitconfig`, ...).
- **Async file I/O in load_chain** — `policy-chain.toml` now read via
`tokio::fs` (was: blocking `std::fs` froze worker on slow mounts).
- **Process-group kill on hooks too** — hook subprocesses get
`process_group(0)` and `killpg(SIGKILL)` on timeout. Was: only the bash
action got this; hook grandchildren orphaned.
- **CLAUDECODE/GROKCODE design note** — documented as perf/UX
optimization, NOT a security boundary (env-controllable parent → confused
deputy is already-game-over scenario).
### Double-enforcement guard
If kei-mcp is invoked from a process where `$CLAUDECODE=1` or `$GROKCODE=1`,
it SKIPS its hook chain — the CLI's native hooks already fired. This is set
automatically by `kei mcp-wire claude` / `kei mcp-wire grok`. On copilot /
agy / kimi the env is unset → chain runs.
## Verification
```bash
# All 4 built-ins must list:
echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{}}' \
| kei-mcp | jq -r '.result.capabilities'
# Block test (kei_bash refuses forbidden command):
echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05"}}
{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"kei_bash","arguments":{"command":"git push https://github.com/x/y.git main"}}}' \
| kei-mcp 2>&1 | grep "RULE 0.1" # expects: BLOCK — RULE 0.1 NO GITHUB PUSH
# Pass test:
echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05"}}
{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"kei_bash","arguments":{"command":"echo OK"}}}' \
| kei-mcp | tail -1 | jq -r '.result.content[0].text' # expects: OK
```
## Related
- [Multi-CLI agent invocation](./multi-cli-agents.md) — DNA-resolved agent dispatch
- `kei-mcp` source: `_primitives/_rust/kei-mcp/src/handlers/safe_tools.rs`
- Policy SSoT: `hooks/_lib/policy-chain.toml`
- Wire scripts: `scripts/kei-mcp-wire*.sh`