feat(approval): hardline blocklist for unrecoverable commands (#15878)

Adds a floor below --yolo: a tiny set of commands so catastrophic they
should never run via the agent, regardless of --yolo, gateway /yolo,
approvals.mode=off, or cron approve mode.  Opting into yolo is trusting
the agent with your files and services — not trusting it to wipe the
disk or power the box off.

The list is deliberately small (12 patterns), covering only
unrecoverable ops:
- rm -rf targeting /, /home, /etc, /usr, /var, /boot, /bin, /sbin,
  /lib, ~, $HOME
- mkfs (any variant)
- dd + redirection to raw block devices (/dev/sd*, /dev/nvme*, etc.)
- fork bomb
- kill -1 / kill -9 -1
- shutdown, reboot, halt, poweroff, init 0/6, telinit 0/6,
  systemctl poweroff/reboot/halt/kexec

Recoverable-but-costly commands (git reset --hard, rm -rf /tmp/x,
chmod -R 777, curl | sh) stay in DANGEROUS_PATTERNS where yolo can
still pass them through — that's what yolo is for.

Container backends (docker/singularity/modal/daytona) continue to
bypass both hardline and dangerous checks, since nothing they do can
touch the host.

Inspired by Mercury Agent's permission-hardened blocklist.

tests/tools/test_hardline_blocklist.py

@@ -0,0 +1,290 @@
+"""Tests for the unconditional hardline command blocklist.
+
+The hardline list is a floor below yolo: a small set of commands so
+catastrophic they should never run via the agent, regardless of --yolo,
+gateway /yolo, approvals.mode=off, or cron approve mode.
+
+Inspired by Mercury Agent's permission-hardened blocklist.
+"""
+import os
+
+import pytest
+
+from tools.approval import (
+    DANGEROUS_PATTERNS,
+    HARDLINE_PATTERNS,
+    check_all_command_guards,
+    check_dangerous_command,
+    detect_dangerous_command,
+    detect_hardline_command,
+    disable_session_yolo,
+    enable_session_yolo,
+    reset_current_session_key,
+    set_current_session_key,
+)
+
+
+# -------------------------------------------------------------------------
+# Pattern detection
+# -------------------------------------------------------------------------
+
+# Commands that MUST be hardline-blocked.
+_HARDLINE_BLOCK = [
+    # rm -rf targeting root / system dirs / home
+    "rm -rf /",
+    "rm -rf /*",
+    "rm -rf /home",
+    "rm -rf /home/*",
+    "rm -rf /etc",
+    "rm -rf /usr",
+    "rm -rf /var",
+    "rm -rf /boot",
+    "rm -rf /bin",
+    "rm --recursive --force /",
+    "rm -fr /",
+    "sudo rm -rf /",
+    "rm -rf ~",
+    "rm -rf ~/",
+    "rm -rf ~/*",
+    "rm -rf $HOME",
+    # Filesystem format
+    "mkfs.ext4 /dev/sda1",
+    "mkfs /dev/sdb",
+    "mkfs.xfs /dev/nvme0n1",
+    # Raw block device overwrites
+    "dd if=/dev/zero of=/dev/sda bs=1M",
+    "dd if=/dev/urandom of=/dev/nvme0n1",
+    "dd if=anything of=/dev/hda",
+    "echo bad > /dev/sda",
+    "cat /dev/urandom > /dev/sdb",
+    # Fork bomb
+    ":(){ :|:& };:",
+    # System-wide kill
+    "kill -9 -1",
+    "kill -1",
+    # Shutdown / reboot / halt
+    "shutdown -h now",
+    "shutdown -r now",
+    "sudo shutdown now",
+    "reboot",
+    "sudo reboot",
+    "halt",
+    "poweroff",
+    "init 0",
+    "init 6",
+    "telinit 0",
+    "systemctl poweroff",
+    "systemctl reboot",
+    "systemctl halt",
+    # Compound / subshell variants
+    "ls; reboot",
+    "echo done && shutdown -h now",
+    "false || halt",
+    "$(reboot)",
+    "`shutdown now`",
+    "sudo -E shutdown now",
+    "env FOO=1 reboot",
+    "exec shutdown",
+    "nohup reboot",
+    "setsid poweroff",
+]
+
+
+# Commands that look superficially similar but must NOT be hardline-blocked.
+_HARDLINE_ALLOW = [
+    # rm on non-protected paths
+    "rm -rf /tmp/foo",
+    "rm -rf /tmp/*",
+    "rm -rf ./build",
+    "rm -rf node_modules",
+    "rm -rf /home/user/scratch",  # subpath of /home, not /home itself
+    "rm -rf ~/Downloads/old",
+    "rm -rf $HOME/tmp",
+    "rm foo.txt",
+    "rm -rf some/path",
+    # dd to regular files
+    "dd if=/dev/zero of=./image.bin",
+    "dd if=./data of=./backup.bin",
+    # Redirect to regular files / non-block devices
+    "echo done > /tmp/flag",
+    "echo test > /dev/null",
+    # Reading devices is fine
+    "ls /dev/sda",
+    "cat /dev/urandom | head -c 10",
+    # Unrelated commands that happen to contain the trigger word
+    "grep 'shutdown' logs.txt",
+    "echo reboot",
+    "echo '# init 0 in comment'",
+    "cat rebooting.log",
+    "echo 'halt and catch fire'",
+    "python3 -c 'print(\"shutdown\")'",
+    "find . -name '*reboot*'",
+    # Word-boundary protection
+    "mkfs_helper --version",
+    # systemctl non-destructive verbs
+    "systemctl status nginx",
+    "systemctl restart nginx",
+    "systemctl stop nginx",
+    "systemctl start nginx",
+    # targeted kill
+    "kill -9 12345",
+    "kill -HUP 1234",
+    "pkill python",
+    # Ordinary ops
+    "git status",
+    "npm run build",
+    "sudo apt update",
+    "curl https://example.com | head",
+]
+
+
+@pytest.mark.parametrize("command", _HARDLINE_BLOCK)
+def test_hardline_detection_blocks(command):
+    is_hl, desc = detect_hardline_command(command)
+    assert is_hl, f"expected hardline to match {command!r}"
+    assert desc, "hardline match must provide a description"
+
+
+@pytest.mark.parametrize("command", _HARDLINE_ALLOW)
+def test_hardline_detection_allows(command):
+    is_hl, desc = detect_hardline_command(command)
+    assert not is_hl, f"expected hardline NOT to match {command!r} (got: {desc})"
+    assert desc is None
+
+
+# -------------------------------------------------------------------------
+# Integration with the approval flow
+# -------------------------------------------------------------------------
+
+@pytest.fixture
+def clean_session(monkeypatch):
+    """Reset session-scoped approval state around each test."""
+    monkeypatch.delenv("HERMES_YOLO_MODE", raising=False)
+    monkeypatch.delenv("HERMES_INTERACTIVE", raising=False)
+    monkeypatch.delenv("HERMES_GATEWAY_SESSION", raising=False)
+    monkeypatch.delenv("HERMES_CRON_SESSION", raising=False)
+    monkeypatch.delenv("HERMES_EXEC_ASK", raising=False)
+    token = set_current_session_key("hardline_test")
+    try:
+        disable_session_yolo("hardline_test")
+        yield
+    finally:
+        disable_session_yolo("hardline_test")
+        reset_current_session_key(token)
+
+
+def test_check_dangerous_command_blocks_hardline(clean_session):
+    result = check_dangerous_command("rm -rf /", "local")
+    assert result["approved"] is False
+    assert result.get("hardline") is True
+    assert "BLOCKED (hardline)" in result["message"]
+
+
+def test_check_all_command_guards_blocks_hardline(clean_session):
+    result = check_all_command_guards("rm -rf /", "local")
+    assert result["approved"] is False
+    assert result.get("hardline") is True
+    assert "BLOCKED (hardline)" in result["message"]
+
+
+def test_yolo_env_var_cannot_bypass_hardline(clean_session, monkeypatch):
+    """HERMES_YOLO_MODE=1 must not bypass the hardline floor."""
+    monkeypatch.setenv("HERMES_YOLO_MODE", "1")
+
+    for cmd in ["rm -rf /", "shutdown -h now", "mkfs.ext4 /dev/sda", "reboot"]:
+        r1 = check_dangerous_command(cmd, "local")
+        assert r1["approved"] is False, f"yolo leaked hardline on {cmd!r} (check_dangerous_command)"
+        assert r1.get("hardline") is True
+
+        r2 = check_all_command_guards(cmd, "local")
+        assert r2["approved"] is False, f"yolo leaked hardline on {cmd!r} (check_all_command_guards)"
+        assert r2.get("hardline") is True
+
+
+def test_session_yolo_cannot_bypass_hardline(clean_session):
+    """Gateway /yolo (session-scoped) must not bypass the hardline floor."""
+    enable_session_yolo("hardline_test")
+
+    result = check_dangerous_command("rm -rf /", "local")
+    assert result["approved"] is False
+    assert result.get("hardline") is True
+
+    result = check_all_command_guards("rm -rf /", "local")
+    assert result["approved"] is False
+    assert result.get("hardline") is True
+
+
+def test_approvals_mode_off_cannot_bypass_hardline(clean_session, monkeypatch, tmp_path):
+    """config approvals.mode=off (yolo-equivalent) must not bypass hardline."""
+    # _get_approval_mode() reads from hermes config; simplest path: monkeypatch the helper.
+    import tools.approval as approval_mod
+    monkeypatch.setattr(approval_mod, "_get_approval_mode", lambda: "off")
+
+    result = check_all_command_guards("rm -rf /", "local")
+    assert result["approved"] is False
+    assert result.get("hardline") is True
+
+
+def test_cron_approve_mode_cannot_bypass_hardline(clean_session, monkeypatch):
+    """Cron sessions with cron_mode=approve must not bypass hardline."""
+    monkeypatch.setenv("HERMES_CRON_SESSION", "1")
+    import tools.approval as approval_mod
+    monkeypatch.setattr(approval_mod, "_get_cron_approval_mode", lambda: "approve")
+
+    result = check_all_command_guards("rm -rf /", "local")
+    assert result["approved"] is False
+    assert result.get("hardline") is True
+
+
+def test_container_backends_still_bypass(clean_session):
+    """Containerized backends remain bypass-approved — they can't touch the host.
+
+    Hardline only protects environments with real host impact (local, ssh).
+    """
+    for env in ("docker", "singularity", "modal", "daytona"):
+        r1 = check_dangerous_command("rm -rf /", env)
+        assert r1["approved"] is True, f"container {env} should still bypass"
+        r2 = check_all_command_guards("rm -rf /", env)
+        assert r2["approved"] is True, f"container {env} should still bypass"
+
+
+def test_hardline_runs_before_dangerous_detection(clean_session):
+    """Hardline command should return hardline block, not dangerous approval prompt."""
+    # `rm -rf /` is both hardline AND matches DANGEROUS_PATTERNS. Hardline must win.
+    is_dangerous, _, _ = detect_dangerous_command("rm -rf /")
+    assert is_dangerous, "precondition: rm -rf / is also in DANGEROUS_PATTERNS"
+
+    result = check_dangerous_command("rm -rf /", "local")
+    assert result.get("hardline") is True
+
+
+def test_recoverable_dangerous_commands_still_pass_yolo(clean_session, monkeypatch):
+    """Yolo still bypasses the regular DANGEROUS_PATTERNS list.
+
+    This confirms we haven't broken the yolo escape hatch — only narrowed it.
+    """
+    monkeypatch.setenv("HERMES_YOLO_MODE", "1")
+
+    # These are dangerous but NOT hardline — yolo should still pass them.
+    for cmd in ["rm -rf /tmp/x", "chmod -R 777 .", "git reset --hard", "git push --force"]:
+        # Sanity: still flagged as dangerous
+        is_dangerous, _, _ = detect_dangerous_command(cmd)
+        assert is_dangerous, f"precondition: {cmd!r} should be in DANGEROUS_PATTERNS"
+        # But NOT hardline
+        is_hl, _ = detect_hardline_command(cmd)
+        assert not is_hl, f"{cmd!r} should not be hardline"
+        # And yolo bypasses the dangerous check
+        result = check_dangerous_command(cmd, "local")
+        assert result["approved"] is True, f"yolo should have bypassed {cmd!r}"
+
+
+def test_hardline_list_is_small():
+    """Hardline list stays focused on unrecoverable commands only.
+
+    If you're adding a 20th+ pattern, reconsider — it probably belongs in
+    DANGEROUS_PATTERNS where yolo can still bypass it.
+    """
+    assert len(HARDLINE_PATTERNS) <= 20, (
+        f"HARDLINE_PATTERNS has grown to {len(HARDLINE_PATTERNS)} entries; "
+        "only truly unrecoverable commands belong here."
+    )