hermes-agent/tools/credential_files.py

"""File passthrough registry for remote terminal backends.

Remote backends (Docker, Modal, SSH) create sandboxes with no host files.
This module ensures that credential files, skill directories, and host-side
cache directories (documents, images, audio, screenshots) are mounted or
synced into those sandboxes so the agent can access them.

**Credentials and skills** — session-scoped registry fed by skill declarations
(``required_credential_files``) and user config (``terminal.credential_files``).

**Cache directories** — gateway-cached uploads, browser screenshots, TTS
audio, and processed images.  Mounted read-only so the remote terminal can
reference files the host side created (e.g. ``unzip`` an uploaded archive).

Remote backends call :func:`get_credential_file_mounts`,
:func:`get_skills_directory_mount` / :func:`iter_skills_files`, and
:func:`get_cache_directory_mounts` / :func:`iter_cache_files` at sandbox
creation time and before each command (for resync on Modal).
"""

from __future__ import annotations

import logging
import os
from contextvars import ContextVar
from pathlib import Path
from typing import Dict, List

logger = logging.getLogger(__name__)

# Session-scoped list of credential files to mount.
# Backed by ContextVar to prevent cross-session data bleed in the gateway pipeline.
_registered_files_var: ContextVar[Dict[str, str]] = ContextVar("_registered_files")


def _get_registered() -> Dict[str, str]:
    """Get or create the registered credential files dict for the current context/session."""
    try:
        return _registered_files_var.get()
    except LookupError:
        val: Dict[str, str] = {}
        _registered_files_var.set(val)
        return val


# Cache for config-based file list (loaded once per process).
_config_files: List[Dict[str, str]] | None = None


def _resolve_hermes_home() -> Path:
    from hermes_constants import get_hermes_home
    return get_hermes_home()


def register_credential_file(
    relative_path: str,
    container_base: str = "/root/.hermes",
) -> bool:
    """Register a credential file for mounting into remote sandboxes.

    *relative_path* is relative to ``HERMES_HOME`` (e.g. ``google_token.json``).
    Returns True if the file exists on the host and was registered.

    Security: rejects absolute paths and path traversal sequences (``..``).
    The resolved host path must remain inside HERMES_HOME so that a malicious
    skill cannot declare ``required_credential_files: ['../../.ssh/id_rsa']``
    and exfiltrate sensitive host files into a container sandbox.
    """
    hermes_home = _resolve_hermes_home()

    # Reject absolute paths — they bypass the HERMES_HOME sandbox entirely.
    if os.path.isabs(relative_path):
        logger.warning(
            "credential_files: rejected absolute path %r (must be relative to HERMES_HOME)",
            relative_path,
        )
        return False

    host_path = hermes_home / relative_path

    # Resolve symlinks and normalise ``..`` before the containment check so
    # that traversal like ``../. ssh/id_rsa`` cannot escape HERMES_HOME.
    try:
        resolved = host_path.resolve()
        hermes_home_resolved = hermes_home.resolve()
        resolved.relative_to(hermes_home_resolved)  # raises ValueError if outside
    except ValueError:
        logger.warning(
            "credential_files: rejected path traversal %r "
            "(resolves to %s, outside HERMES_HOME %s)",
            relative_path,
            resolved,
            hermes_home_resolved,
        )
        return False

    if not resolved.is_file():
        logger.debug("credential_files: skipping %s (not found)", resolved)
        return False

    container_path = f"{container_base.rstrip('/')}/{relative_path}"
    _get_registered()[container_path] = str(resolved)
    logger.debug("credential_files: registered %s -> %s", resolved, container_path)
    return True


def register_credential_files(
    entries: list,
    container_base: str = "/root/.hermes",
) -> List[str]:
    """Register multiple credential files from skill frontmatter entries.

    Each entry is either a string (relative path) or a dict with a ``path``
    key.  Returns the list of relative paths that were NOT found on the host
    (i.e. missing files).
    """
    missing = []
    for entry in entries:
        if isinstance(entry, str):
            rel_path = entry.strip()
        elif isinstance(entry, dict):
            rel_path = (entry.get("path") or entry.get("name") or "").strip()
        else:
            continue
        if not rel_path:
            continue
        if not register_credential_file(rel_path, container_base):
            missing.append(rel_path)
    return missing


def _load_config_files() -> List[Dict[str, str]]:
    """Load ``terminal.credential_files`` from config.yaml (cached)."""
    global _config_files
    if _config_files is not None:
        return _config_files

    result: List[Dict[str, str]] = []
    try:
        from hermes_cli.config import read_raw_config
        hermes_home = _resolve_hermes_home()
        cfg = read_raw_config()
        cred_files = cfg.get("terminal", {}).get("credential_files")
        if isinstance(cred_files, list):
            hermes_home_resolved = hermes_home.resolve()
            for item in cred_files:
                if isinstance(item, str) and item.strip():
                    rel = item.strip()
                    if os.path.isabs(rel):
                        logger.warning(
                            "credential_files: rejected absolute config path %r", rel,
                        )
                        continue
                    host_path = (hermes_home / rel).resolve()
                    try:
                        host_path.relative_to(hermes_home_resolved)
                    except ValueError:
                        logger.warning(
                            "credential_files: rejected config path traversal %r "
                            "(resolves to %s, outside HERMES_HOME %s)",
                            rel, host_path, hermes_home_resolved,
                        )
                        continue
                    if host_path.is_file():
                        container_path = f"/root/.hermes/{rel}"
                        result.append({
                            "host_path": str(host_path),
                            "container_path": container_path,
                        })
    except Exception as e:
        logger.warning("Could not read terminal.credential_files from config: %s", e)

    _config_files = result
    return _config_files


def get_credential_file_mounts() -> List[Dict[str, str]]:
    """Return all credential files that should be mounted into remote sandboxes.

    Each item has ``host_path`` and ``container_path`` keys.
    Combines skill-registered files and user config.
    """
    mounts: Dict[str, str] = {}

    # Skill-registered files
    for container_path, host_path in _get_registered().items():
        # Re-check existence (file may have been deleted since registration)
        if Path(host_path).is_file():
            mounts[container_path] = host_path

    # Config-based files
    for entry in _load_config_files():
        cp = entry["container_path"]
        if cp not in mounts and Path(entry["host_path"]).is_file():
            mounts[cp] = entry["host_path"]

    return [
        {"host_path": hp, "container_path": cp}
        for cp, hp in mounts.items()
    ]


def get_skills_directory_mount(
    container_base: str = "/root/.hermes",
) -> list[Dict[str, str]]:
    """Return mount info for all skill directories (local + external).

    Skills may include ``scripts/``, ``templates/``, and ``references/``
    subdirectories that the agent needs to execute inside remote sandboxes.

    **Security:** Bind mounts follow symlinks, so a malicious symlink inside
    the skills tree could expose arbitrary host files to the container.  When
    symlinks are detected, this function creates a sanitized copy (regular
    files only) in a temp directory and returns that path instead.  When no
    symlinks are present (the common case), the original directory is returned
    directly with zero overhead.

    Returns a list of dicts with ``host_path`` and ``container_path`` keys.
    The local skills dir mounts at ``<container_base>/skills``, external dirs
    at ``<container_base>/external_skills/<index>``.
    """
    mounts = []
    hermes_home = _resolve_hermes_home()
    skills_dir = hermes_home / "skills"
    if skills_dir.is_dir():
        host_path = _safe_skills_path(skills_dir)
        mounts.append({
            "host_path": host_path,
            "container_path": f"{container_base.rstrip('/')}/skills",
        })

    # Mount external skill dirs
    try:
        from agent.skill_utils import get_external_skills_dirs
        for idx, ext_dir in enumerate(get_external_skills_dirs()):
            if ext_dir.is_dir():
                host_path = _safe_skills_path(ext_dir)
                mounts.append({
                    "host_path": host_path,
                    "container_path": f"{container_base.rstrip('/')}/external_skills/{idx}",
                })
    except ImportError:
        pass

    return mounts


_safe_skills_tempdir: Path | None = None


def _safe_skills_path(skills_dir: Path) -> str:
    """Return *skills_dir* if symlink-free, else a sanitized temp copy."""
    global _safe_skills_tempdir

    symlinks = [p for p in skills_dir.rglob("*") if p.is_symlink()]
    if not symlinks:
        return str(skills_dir)

    for link in symlinks:
        logger.warning("credential_files: skipping symlink in skills dir: %s -> %s",
                       link, os.readlink(link))

    import atexit
    import shutil
    import tempfile

    # Reuse the same temp dir across calls to avoid accumulation.
    if _safe_skills_tempdir and _safe_skills_tempdir.is_dir():
        shutil.rmtree(_safe_skills_tempdir, ignore_errors=True)

    safe_dir = Path(tempfile.mkdtemp(prefix="hermes-skills-safe-"))
    _safe_skills_tempdir = safe_dir

    for item in skills_dir.rglob("*"):
        if item.is_symlink():
            continue
        rel = item.relative_to(skills_dir)
        target = safe_dir / rel
        if item.is_dir():
            target.mkdir(parents=True, exist_ok=True)
        elif item.is_file():
            target.parent.mkdir(parents=True, exist_ok=True)
            shutil.copy2(str(item), str(target))

    def _cleanup():
        if safe_dir.is_dir():
            shutil.rmtree(safe_dir, ignore_errors=True)

    atexit.register(_cleanup)
    logger.info("credential_files: created symlink-safe skills copy at %s", safe_dir)
    return str(safe_dir)


def iter_skills_files(
    container_base: str = "/root/.hermes",
) -> List[Dict[str, str]]:
    """Yield individual (host_path, container_path) entries for skills files.

    Includes both the local skills dir and any external dirs configured via
    skills.external_dirs.  Skips symlinks entirely.  Preferred for backends
    that upload files individually (Daytona, Modal) rather than mounting a
    directory.
    """
    result: List[Dict[str, str]] = []

    hermes_home = _resolve_hermes_home()
    skills_dir = hermes_home / "skills"
    if skills_dir.is_dir():
        container_root = f"{container_base.rstrip('/')}/skills"
        for item in skills_dir.rglob("*"):
            if item.is_symlink() or not item.is_file():
                continue
            rel = item.relative_to(skills_dir)
            result.append({
                "host_path": str(item),
                "container_path": f"{container_root}/{rel}",
            })

    # Include external skill dirs
    try:
        from agent.skill_utils import get_external_skills_dirs
        for idx, ext_dir in enumerate(get_external_skills_dirs()):
            if not ext_dir.is_dir():
                continue
            container_root = f"{container_base.rstrip('/')}/external_skills/{idx}"
            for item in ext_dir.rglob("*"):
                if item.is_symlink() or not item.is_file():
                    continue
                rel = item.relative_to(ext_dir)
                result.append({
                    "host_path": str(item),
                    "container_path": f"{container_root}/{rel}",
                })
    except ImportError:
        pass

    return result


# ---------------------------------------------------------------------------
# Cache directory mounts (documents, images, audio, screenshots)
# ---------------------------------------------------------------------------

# The four cache subdirectories that should be mirrored into remote backends.
# Each tuple is (new_subpath, old_name) matching hermes_constants.get_hermes_dir().
_CACHE_DIRS: list[tuple[str, str]] = [
    ("cache/documents", "document_cache"),
    ("cache/images", "image_cache"),
    ("cache/audio", "audio_cache"),
    ("cache/screenshots", "browser_screenshots"),
]


def get_cache_directory_mounts(
    container_base: str = "/root/.hermes",
) -> List[Dict[str, str]]:
    """Return mount entries for each cache directory that exists on disk.

    Used by Docker to create bind mounts.  Each entry has ``host_path`` and
    ``container_path`` keys.  The host path is resolved via
    ``get_hermes_dir()`` for backward compatibility with old directory layouts.
    """
    from hermes_constants import get_hermes_dir

    mounts: List[Dict[str, str]] = []
    for new_subpath, old_name in _CACHE_DIRS:
        host_dir = get_hermes_dir(new_subpath, old_name)
        if host_dir.is_dir():
            # Always map to the *new* container layout regardless of host layout.
            container_path = f"{container_base.rstrip('/')}/{new_subpath}"
            mounts.append({
                "host_path": str(host_dir),
                "container_path": container_path,
            })
    return mounts


def iter_cache_files(
    container_base: str = "/root/.hermes",
) -> List[Dict[str, str]]:
    """Return individual (host_path, container_path) entries for cache files.

    Used by Modal to upload files individually and resync before each command.
    Skips symlinks.  The container paths use the new ``cache/<subdir>`` layout.
    """
    from hermes_constants import get_hermes_dir

    result: List[Dict[str, str]] = []
    for new_subpath, old_name in _CACHE_DIRS:
        host_dir = get_hermes_dir(new_subpath, old_name)
        if not host_dir.is_dir():
            continue
        container_root = f"{container_base.rstrip('/')}/{new_subpath}"
        for item in host_dir.rglob("*"):
            if item.is_symlink() or not item.is_file():
                continue
            rel = item.relative_to(host_dir)
            result.append({
                "host_path": str(item),
                "container_path": f"{container_root}/{rel}",
            })
    return result


def clear_credential_files() -> None:
    """Reset the skill-scoped registry (e.g. on session reset)."""
    _get_registered().clear()


def reset_config_cache() -> None:
    """Force re-read of config on next access (for testing)."""
    global _config_files
    _config_files = None