mirror of
https://github.com/NousResearch/hermes-agent.git
synced 2026-07-23 16:36:23 +00:00
1cb67a5916
_run_helper early-returns on Windows before spawning, so the process- group kill in the timeout path can never execute there.
488 lines
18 KiB
Python
488 lines
18 KiB
Python
"""``command`` secret source — resolve secrets via a user-configured helper.
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Ports the security semantics of the desktop app's TypeScript
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``CommandSecretsProvider`` (hermes-desktop ``src/main/secrets/commandProvider.ts``)
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to the Python agent. The helper command (e.g. ``keepassxc-cli``,
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``secret-tool``, or a script that cats a tmpfs env file) comes from
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``secrets.command`` in ``config.yaml`` — NEVER from ``.env``, which holds
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only secret values.
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Security model (mirrors the TS provider line-for-line where it matters):
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* The command string is the USER'S OWN configuration (same trust level as
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the ``.env`` file they control), so it is run via ``/bin/sh -c <command>``.
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* The requested key is passed to the child ONLY via the ``HERMES_SECRET_KEY``
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environment variable — it is NEVER interpolated into the shell string, so
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a hostile key name (e.g. ``"; rm -rf ~``) is inert data, not code.
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* Hard timeout (default 3s) + output cap (default 1 MiB); any failure
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(non-zero exit, timeout, spawn failure, oversized output) degrades to
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"no value" rather than raising.
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* Failures log ONLY structured fields (exit code / signal / errno) to
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stderr — never the command string, the helper's stderr, or any secret
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value. The helper's stderr is captured via a pipe and DISCARDED so its
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diagnostics (which can carry secret material) never reach our stderr.
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* The startup/apply path runs the helper exactly ONCE (with an empty
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``HERMES_SECRET_KEY``) — it is never called per-key in a loop, so a
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helper that blocks (e.g. on a vault unlock prompt) can't be spawned
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dozens of times.
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* PLATFORM: the provider is POSIX-only (needs ``/bin/sh``). On Windows it
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degrades to an empty result with a warning; Windows users stay on the
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default ``env`` provider.
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"""
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from __future__ import annotations
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import os
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import platform
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import re
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import signal as _signal
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import subprocess
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import sys
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from pathlib import Path
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from typing import Dict, Optional
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# Reuse the exact result shape the bitwarden source returns so
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# hermes_cli.env_loader can consume both providers identically.
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from agent.secret_sources.base import ErrorKind, SecretSource
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from agent.secret_sources.bitwarden import FetchResult
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__all__ = [
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"FetchResult",
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"apply_command_secrets",
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"get_command_secret",
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"list_command_secrets",
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"parse_secret_output",
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"unquote_dotenv_value",
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]
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# Hard cap so a hung helper can never wedge startup. Kept deliberately
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# TIGHT (3s) — a configured helper MUST be fast and NON-INTERACTIVE
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# (e.g. `keepassxc-cli` against an already-unlocked DB, `secret-tool
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# lookup`, or `cat`-ing a tmpfs env file), NOT something that prompts
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# for a touch/PIN.
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_COMMAND_TIMEOUT_SECONDS = 3.0
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# Defensive cap on helper output (1 MiB) — a misbehaving command can't OOM us.
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_MAX_OUTPUT_BYTES = 1024 * 1024
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# A line is treated as a KEY=VALUE pair only when it matches an env-key
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# shape before the '='. Anchored; `.` does not cross newlines, so a
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# multi-line blob never matches as a single "env-shaped" value.
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_ENV_LINE = re.compile(r"^([A-Za-z_][A-Za-z0-9_]*)=(.*)$")
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def _is_windows() -> bool:
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return os.name == "nt" or platform.system() == "Windows"
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def unquote_dotenv_value(raw: str) -> str:
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"""Strip a single layer of matching surrounding quotes from a dotenv value.
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Requires length >= 2 so a lone quote (``"``) is left intact rather than
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collapsing to empty, and ``""``/``''`` correctly yield an empty string.
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Shared by the single-key parser and the list path so both unquote
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identically.
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"""
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t = raw.strip()
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if len(t) >= 2 and (
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(t.startswith('"') and t.endswith('"'))
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or (t.startswith("'") and t.endswith("'"))
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):
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return t[1:-1]
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return t
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def parse_secret_output(stdout: str, wanted_key: str) -> Optional[str]:
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"""Parse a secret-fetch helper's stdout. Supports BOTH shapes:
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* a bare value (single secret): the whole trimmed stdout is the value.
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* a dotenv blob (KEY=VALUE lines): parse them and return the entry for
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``wanted_key``.
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Mirrors the TS ``parseSecretOutput`` exactly, including the cross-key
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misroute guard and the base64-padding disambiguation.
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"""
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text = stdout.replace("\r\n", "\n")
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lines = text.split("\n")
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# 1. Exact dotenv match wins: scan for a `wanted_key=...` line. This
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# is deterministic and never returns another key's value.
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dotenv_lines = [
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line
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for line in (raw.strip() for raw in lines)
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if line and not line.startswith("#") and _ENV_LINE.match(line)
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]
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for line in dotenv_lines:
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m = _ENV_LINE.match(line)
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assert m is not None # filtered above
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if m.group(1) == wanted_key:
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value = unquote_dotenv_value(m.group(2))
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# Whitespace-only (e.g. a quoted `K=" "` placeholder) is "no
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# value": it would otherwise flow into an Authorization header
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# → guaranteed 401.
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return value if value.strip() != "" else None
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# 2. The output is a multi-key dotenv dump that does NOT contain the
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# wanted key → None, rather than mis-returning an unrelated line as
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# a bare value. Only >=2 env-shaped lines count as a dump: a SINGLE
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# non-matching env-shaped line falls through to the bare-value
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# branch, because a bare secret can itself match the KEY=VALUE shape
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# (e.g. base64 with '=' padding, "dGVzdA==") and must not be
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# misclassified as a dump.
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if len(dotenv_lines) > 1:
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return None
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# 3. Otherwise treat the whole output as a single bare value (a per-key
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# helper that printed just the secret). Trim first so whitespace-only
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# output (a ' '/'\t' placeholder entry) resolves to None, never a "key".
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value = text.strip()
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if value == "":
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return None
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# SECURITY (S2): a single env-shaped line for a DIFFERENT key must not
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# be returned as the wanted secret. A sloppy helper (e.g. `head -1
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# env-file`, or a grep that matched the wrong line) emitting
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# `OTHER_KEY=realvalue` would otherwise flow — key name, '=' and the
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# OTHER key's value — into an Authorization header sent to the WANTED
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# key's endpoint: cross-provider credential leakage, not just a 401.
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# Disambiguation from a bare base64 secret: base64 padding only ever
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# produces an env-shaped line whose "value" part is empty or all '='
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# (`dGVzdA==` → key `dGVzdA`, value `=`), so a non-trivial value part
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# after a non-matching key means a misrouted dotenv entry → None.
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env_shaped = _ENV_LINE.match(value)
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if (
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env_shaped
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and env_shaped.group(1) != wanted_key
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and re.fullmatch(r"=*", env_shaped.group(2).strip()) is None
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):
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return None
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return value
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def _run_helper(
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command: str,
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secret_key: str,
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timeout_seconds: float,
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max_output_bytes: int,
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) -> Optional[str]:
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"""Run the helper via ``/bin/sh -c`` and return its stdout, or None.
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The key is passed as DATA via ``HERMES_SECRET_KEY`` — never interpolated
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into the command string. Both stdout and stderr are captured via pipes
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(never inherited); stderr is discarded. Any failure logs structured
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fields only and returns None — never raises.
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"""
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if _is_windows():
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print(
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"[secrets:command] the 'command' provider is POSIX-only "
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"(needs /bin/sh); resolving no value on Windows",
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file=sys.stderr,
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)
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return None
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env = os.environ.copy()
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env["HERMES_SECRET_KEY"] = secret_key
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try:
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proc = subprocess.Popen( # noqa: S602 — command is the user's own config
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["/bin/sh", "-c", command],
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env=env,
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stdin=subprocess.DEVNULL,
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stdout=subprocess.PIPE,
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stderr=subprocess.PIPE, # captured and DISCARDED — never inherited
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start_new_session=True, # so the hard timeout can kill the whole group
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)
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except OSError as exc:
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print(
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f"[secrets:command] helper failed to spawn; resolving no value: "
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f"errno={exc.errno}",
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file=sys.stderr,
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)
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return None
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try:
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stdout_bytes, _stderr_discarded = proc.communicate(timeout=timeout_seconds)
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except subprocess.TimeoutExpired:
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# Hard timeout: kill the whole process group (a helper script may
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# have forked children that would otherwise keep the pipe open).
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# POSIX-only by construction: _run_helper early-returns on Windows
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# before ever spawning, so this line can't execute there.
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try:
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os.killpg(os.getpgid(proc.pid), _signal.SIGKILL) # windows-footgun: ok
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except (ProcessLookupError, PermissionError, OSError):
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proc.kill()
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try:
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proc.communicate(timeout=1.0)
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except (subprocess.TimeoutExpired, ValueError, OSError):
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pass
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print(
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f"[secrets:command] helper timed out after {timeout_seconds:g}s; "
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f"resolving no value",
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file=sys.stderr,
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)
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return None
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if proc.returncode != 0:
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# Structured fields ONLY — never the command string or the helper's
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# stderr (either can carry secret material).
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if proc.returncode < 0:
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try:
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sig = _signal.Signals(-proc.returncode).name
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except ValueError:
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sig = str(-proc.returncode)
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code, signame = "?", sig
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else:
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code, signame = str(proc.returncode), "none"
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print(
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f"[secrets:command] helper failed; resolving no value: "
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f"code={code} signal={signame}",
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file=sys.stderr,
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)
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return None
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if len(stdout_bytes) > max_output_bytes:
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print(
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f"[secrets:command] helper output exceeded the "
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f"{max_output_bytes}-byte cap; resolving no value",
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file=sys.stderr,
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)
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return None
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return stdout_bytes.decode("utf-8", errors="replace")
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def _parse_dotenv_map(stdout: str) -> Dict[str, str]:
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"""Parse a KEY=VALUE blob into a map (the list/enumerate path).
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Mirrors the TS ``list()``: only env-shaped lines contribute; comments
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and non-matching lines are skipped. A bare-value helper yields ``{}``
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— per-key resolution via :func:`get_command_secret` still works.
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"""
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out: Dict[str, str] = {}
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for raw in stdout.replace("\r\n", "\n").split("\n"):
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line = raw.strip()
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if not line or line.startswith("#"):
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continue
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m = _ENV_LINE.match(line)
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if not m:
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continue
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out[m.group(1)] = unquote_dotenv_value(m.group(2))
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return out
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def get_command_secret(
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*,
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command: str,
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key: str,
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timeout_seconds: float = _COMMAND_TIMEOUT_SECONDS,
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max_output_bytes: int = _MAX_OUTPUT_BYTES,
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) -> Optional[str]:
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"""Resolve a single secret by running the helper with the key in
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``HERMES_SECRET_KEY``. Returns None on any failure — never raises."""
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command = (command or "").strip()
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if not command:
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return None
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stdout = _run_helper(command, key, timeout_seconds, max_output_bytes)
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if stdout is None:
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return None
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return parse_secret_output(stdout, key)
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def list_command_secrets(
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*,
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command: str,
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timeout_seconds: float = _COMMAND_TIMEOUT_SECONDS,
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max_output_bytes: int = _MAX_OUTPUT_BYTES,
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) -> Dict[str, str]:
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"""Enumerate secrets by running the helper ONCE with an empty key.
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Returns the dotenv map ONLY when the helper emits a KEY=VALUE blob;
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a bare-value helper returns ``{}``. Never raises.
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"""
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command = (command or "").strip()
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if not command:
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return {}
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stdout = _run_helper(command, "", timeout_seconds, max_output_bytes)
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if stdout is None:
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return {}
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return _parse_dotenv_map(stdout)
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# ---------------------------------------------------------------------------
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# Public entry point — called from hermes_cli.env_loader
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# ---------------------------------------------------------------------------
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def apply_command_secrets(
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*,
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command: str,
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override_existing: bool = False,
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timeout_seconds: float = _COMMAND_TIMEOUT_SECONDS,
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max_output_bytes: int = _MAX_OUTPUT_BYTES,
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home_path: Optional[Path] = None,
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) -> FetchResult:
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"""Run the helper once at startup and set its KEY=VALUE output on
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``os.environ``.
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LEGACY shim retained for API symmetry with ``apply_bitwarden_secrets``;
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the startup path goes through :class:`CommandSource` + the registry
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orchestrator instead (which owns precedence and the environ writes).
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"""
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result = FetchResult()
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command = (command or "").strip()
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if not command:
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result.error = (
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"secrets.command.enabled is true but secrets.command.command is "
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"empty. Set the helper command in config.yaml."
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)
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return result
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if _is_windows():
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result.warnings.append(
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"the 'command' secret source is POSIX-only (needs /bin/sh); "
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"skipping on Windows"
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)
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return result
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# The list/enumerate path: run the helper exactly ONCE with an empty
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# HERMES_SECRET_KEY and parse its stdout as a dotenv blob.
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stdout = _run_helper(command, "", timeout_seconds, max_output_bytes)
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if stdout is None:
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# _run_helper already logged structured fields to stderr.
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result.warnings.append(
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"helper command failed at startup; no secrets applied "
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"(process env / .env values remain in effect)"
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)
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return result
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secrets = _parse_dotenv_map(stdout)
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result.secrets = secrets
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if not secrets:
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result.warnings.append(
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"helper output was not a KEY=VALUE map; nothing applied at "
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"startup (a bare-value helper still resolves single keys on demand)"
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)
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return result
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for key, value in secrets.items():
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if value.strip() == "":
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# Whitespace-only placeholder entries are "no value" — applying
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# them would flow into an Authorization header → guaranteed 401.
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result.skipped.append(key)
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continue
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if not override_existing and os.environ.get(key):
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# Process env / .env win — same precedence as bitwarden.
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result.skipped.append(key)
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continue
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os.environ[key] = value
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result.applied.append(key)
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return result
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# ---------------------------------------------------------------------------
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# SecretSource adapter — the registry-facing wrapper around this module.
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# ---------------------------------------------------------------------------
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class CommandSource(SecretSource):
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"""User-configured helper command as a registered secret source.
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Composes with the other sources (Bitwarden, 1Password, plugins) through
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the ``apply_all()`` orchestrator — enable any combination simultaneously;
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there is deliberately NO single-provider selector. ``fetch()`` only
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fetches: precedence, ``override_existing`` semantics, conflict warnings,
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and the ``os.environ`` writes are the orchestrator's job.
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Bulk shape: the helper enumerates a KEY=VALUE blob in one run. Config::
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secrets:
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command:
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enabled: true
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command: "cat /run/user/1000/hermes-secrets.env"
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# or per-vault CLIs: keepassxc-cli / secret-tool / pass / gpg —
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# anything fast and NON-interactive.
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"""
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name = "command"
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label = "Command helper"
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shape = "bulk"
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def config_schema(self) -> dict:
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return {
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"enabled": {"description": "Master switch", "default": False},
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"command": {
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"description": "Helper run via /bin/sh -c; must print a "
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"KEY=VALUE blob on stdout",
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"default": "",
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},
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"helper_timeout_seconds": {
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"description": "Hard timeout for one helper run",
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"default": _COMMAND_TIMEOUT_SECONDS,
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},
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"override_existing": {
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"description": "Helper values overwrite .env/shell values",
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"default": False,
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},
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}
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def fetch(self, cfg: dict, home_path: Path) -> FetchResult:
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cfg = cfg if isinstance(cfg, dict) else {}
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result = FetchResult()
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command = str(cfg.get("command") or "").strip()
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if not command:
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result.error = (
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"secrets.command.enabled is true but secrets.command.command "
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"is empty. Set the helper command in config.yaml."
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)
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result.error_kind = ErrorKind.NOT_CONFIGURED
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return result
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if _is_windows():
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result.error = (
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"the 'command' secret source is POSIX-only (needs /bin/sh); "
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"skipping on Windows"
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)
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result.error_kind = ErrorKind.NOT_CONFIGURED
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return result
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try:
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timeout = float(cfg.get("helper_timeout_seconds",
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_COMMAND_TIMEOUT_SECONDS))
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except (TypeError, ValueError):
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timeout = _COMMAND_TIMEOUT_SECONDS
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stdout = _run_helper(command, "", timeout, _MAX_OUTPUT_BYTES)
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if stdout is None:
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# _run_helper already logged structured fields to stderr.
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result.error = (
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"helper command failed (see structured fields above); "
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"no secrets applied"
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)
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result.error_kind = ErrorKind.INTERNAL
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return result
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secrets = _parse_dotenv_map(stdout)
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if not secrets:
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result.warnings.append(
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"helper output was not a KEY=VALUE map; nothing to apply"
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)
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return result
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result.secrets = secrets
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return result
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def remediation(self, kind, cfg: dict) -> str:
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if kind == ErrorKind.NOT_CONFIGURED:
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return (
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"Set secrets.command.command in config.yaml to a fast, "
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"non-interactive helper that prints KEY=VALUE lines."
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)
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if kind == ErrorKind.INTERNAL:
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return (
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"Run the helper manually in a shell to see its real error — "
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"Hermes discards helper stderr so diagnostics can't leak "
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"secret material."
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)
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return super().remediation(kind, cfg)
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