net-kingdom/local-identity/src/local_identity/audit.py

"""
Append-only audit log for local-identity.

All CLI commands and OIDC server events write one entry per operation to
~/.local-identity/audit.log (mode 600).

Format (TSV):  ISO-timestamp  command  username  outcome
Example:
  2026-03-02T00:00:00Z  init        alice   ok
  2026-03-02T00:01:00Z  serve/auth  alice   auth_request
  2026-03-02T00:01:01Z  serve/token alice   token_issued

Failures (e.g. file permission errors) are silently swallowed — the audit
log must never interrupt the primary operation.
"""

import datetime
import os
from pathlib import Path

from .store import _store_dir


def _audit_log_path() -> Path:
    return _store_dir() / "audit.log"


def log_event(command: str, username: str | None, outcome: str) -> None:
    """Append one audit entry. Silent on any I/O failure."""
    timestamp = datetime.datetime.now(datetime.timezone.utc).strftime(
        "%Y-%m-%dT%H:%M:%SZ"
    )
    entry = f"{timestamp}\t{command}\t{username or '-'}\t{outcome}\n"
    path = _audit_log_path()
    try:
        is_new = not path.exists()
        with open(path, "a", encoding="utf-8") as fh:
            fh.write(entry)
        if is_new:
            os.chmod(path, 0o600)
    except OSError:
        pass