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

7.8 KiB

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:

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':

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:

# ~/.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 guardkei_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 rootallowed_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_chainpolicy-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

# 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
  • Multi-CLI agent invocation — 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