mi
317 lines
13 KiB
Python
317 lines
13 KiB
Python
#!/usr/bin/env python3
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"""Fail-closed VM2 adaptation of the reviewed HAN Selectel secrets loader."""
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from __future__ import annotations
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import argparse
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import base64
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import binascii
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import json
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import os
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import random
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import re
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import ssl
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import stat
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import sys
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import tempfile
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import time
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import urllib.error
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import urllib.parse
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import urllib.request
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from pathlib import Path
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from typing import Any, Mapping
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IDENTITY_URL = "https://cloud.api.selcloud.ru/identity/v3/auth/tokens"
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NAME_RE = re.compile(r"^[A-Z][A-Z0-9_]*$")
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CONSUMER_RE = re.compile(r"^[a-zA-Z0-9][a-zA-Z0-9_.-]*$")
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RETRYABLE = {408, 425, 429, 500, 502, 503, 504}
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MAX_CONFIG = 1_048_576
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class LoaderError(Exception):
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"""Expected error whose text contains no provider response or secret value."""
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def fail(message: str) -> None:
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raise LoaderError(message)
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def private_file(path: Path, label: str) -> None:
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try:
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metadata = path.lstat()
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except OSError as exc:
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fail(f"cannot inspect {label}: {exc.__class__.__name__}")
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if stat.S_ISLNK(metadata.st_mode) or not stat.S_ISREG(metadata.st_mode):
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fail(f"{label} must be a regular non-symlink file")
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if os.name != "nt" and stat.S_IMODE(metadata.st_mode) & 0o077:
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fail(f"{label} must not be accessible by group or other users")
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def read_limited(path: Path, limit: int, label: str) -> bytes:
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try:
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with path.open("rb") as stream:
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value = stream.read(limit + 1)
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except OSError as exc:
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fail(f"cannot read {label}: {exc.__class__.__name__}")
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if len(value) > limit:
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fail(f"{label} exceeds configured limit")
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return value
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def object_value(value: Any, label: str) -> dict[str, Any]:
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if not isinstance(value, dict):
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fail(f"{label} must be an object")
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return value
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def load_json(path: Path) -> dict[str, Any]:
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try:
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return object_value(json.loads(read_limited(path, MAX_CONFIG, "configuration")), "configuration")
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except (UnicodeDecodeError, json.JSONDecodeError):
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fail("configuration is not valid UTF-8 JSON")
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def required_string(value: Mapping[str, Any], key: str, label: str) -> str:
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result = value.get(key)
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if not isinstance(result, str) or not result:
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fail(f"{label}.{key} must be a non-empty string")
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return result
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class NoRedirect(urllib.request.HTTPRedirectHandler):
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def redirect_request(self, req: Any, fp: Any, code: int, msg: str, headers: Any, newurl: str) -> None:
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return None
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class Client:
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def __init__(self, timeout: float, retries: int, maximum: int, ca_file: str | None) -> None:
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context = ssl.create_default_context(cafile=ca_file)
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self.opener = urllib.request.build_opener(
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urllib.request.HTTPSHandler(context=context), NoRedirect()
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)
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self.timeout, self.retries, self.maximum = timeout, retries, maximum
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def request(
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self, method: str, url: str, expected: set[int], headers: Mapping[str, str] | None = None, body: bytes | None = None
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) -> tuple[Mapping[str, str], bytes]:
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parsed = urllib.parse.urlsplit(url)
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if parsed.scheme != "https" or not parsed.netloc or parsed.username or parsed.password:
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fail("provider endpoint must be credential-free HTTPS")
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request = urllib.request.Request(url, data=body, headers=dict(headers or {}), method=method)
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for attempt in range(self.retries + 1):
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try:
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with self.opener.open(request, timeout=self.timeout) as response:
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if int(response.headers.get("Content-Length", 0)) > self.maximum:
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fail("provider response exceeds configured limit")
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response_body = response.read(self.maximum + 1)
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if len(response_body) > self.maximum:
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fail("provider response exceeds configured limit")
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if response.status not in expected:
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fail(f"provider request failed with HTTP {response.status}")
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return response.headers, response_body
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except urllib.error.HTTPError as exc:
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if exc.code not in RETRYABLE or attempt == self.retries:
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fail(f"provider request failed with HTTP {exc.code}")
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except (urllib.error.URLError, TimeoutError, OSError):
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if attempt == self.retries:
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fail("provider request failed after retries")
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time.sleep(min(8.0, 0.25 * (2**attempt)) * (0.5 + random.random()))
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fail("provider request failed")
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def credential(selectel: Mapping[str, Any], environ: Mapping[str, str]) -> str:
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configured = Path(required_string(selectel, "password_file", "selectel"))
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if not configured.is_absolute():
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directory = environ.get("CREDENTIALS_DIRECTORY")
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if not directory:
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fail("relative password_file requires CREDENTIALS_DIRECTORY")
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configured = Path(directory) / configured
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private_file(configured, "Selectel credential")
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try:
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value = read_limited(configured, 16_384, "Selectel credential").decode().rstrip("\r\n")
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except UnicodeDecodeError:
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fail("Selectel credential is not UTF-8")
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if not value or "\n" in value or "\r" in value:
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fail("Selectel credential must contain one non-empty line")
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return value
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def decode_document(raw: bytes, label: str) -> dict[str, Any]:
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try:
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return object_value(json.loads(raw.decode()), label)
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except (UnicodeDecodeError, json.JSONDecodeError):
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fail(f"{label} is not valid JSON")
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def fetch_values(config: Mapping[str, Any], specs: Mapping[str, Mapping[str, Any]], environ: Mapping[str, str]) -> dict[str, bytes]:
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selectel = object_value(config.get("selectel"), "selectel")
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http = object_value(config.get("http", {}), "http")
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client = Client(
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float(http.get("timeout_seconds", 10)),
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int(http.get("retries", 3)),
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int(http.get("max_response_bytes", MAX_CONFIG)),
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selectel.get("ca_file"),
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)
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account = required_string(selectel, "account_id", "selectel")
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auth = {
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"auth": {
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"identity": {"methods": ["password"], "password": {"user": {
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"name": required_string(selectel, "username", "selectel"),
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"domain": {"name": account},
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"password": credential(selectel, environ),
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}}},
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"scope": {"project": {
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"name": required_string(selectel, "project_name", "selectel"),
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"domain": {"name": account},
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}},
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}
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}
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headers, body = client.request(
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"POST",
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str(selectel.get("identity_url", IDENTITY_URL)),
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{201},
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{"Content-Type": "application/json", "Accept": "application/json"},
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json.dumps(auth, separators=(",", ":")).encode(),
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)
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token = headers.get("X-Subject-Token")
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identity = decode_document(body, "identity response").get("token")
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if not token or not isinstance(identity, dict) or not isinstance(identity.get("project"), dict):
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fail("identity token is missing or not project-scoped")
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matches: list[str] = []
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for service in identity.get("catalog", []):
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if isinstance(service, dict) and service.get("type") == "secrets-manager":
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for endpoint in service.get("endpoints", []):
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if (
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isinstance(endpoint, dict)
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and endpoint.get("region") == selectel.get("region")
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and endpoint.get("interface") == selectel.get("interface", "public")
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and isinstance(endpoint.get("url"), str)
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):
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matches.append(endpoint["url"].rstrip("/"))
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if len(matches) != 1:
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fail("service catalog has no unique matching Secrets Manager endpoint")
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values: dict[str, bytes] = {}
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for name, spec in specs.items():
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remote = required_string(spec, "remote", f"secrets.{name}")
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_, secret_body = client.request(
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"GET",
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matches[0] + "/v1/" + urllib.parse.quote(remote, safe=""),
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{200},
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{"X-Auth-Token": str(token), "Accept": "application/json"},
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)
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document = decode_document(secret_body, f"secret {name} response")
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payload = document.get("version") if isinstance(document.get("version"), dict) else document
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encoded = payload.get("value")
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try:
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value = base64.b64decode(encoded, validate=True)
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except (TypeError, ValueError, binascii.Error):
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fail(f"secret {name} has invalid encoding")
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maximum = int(spec.get("max_bytes", 65_536))
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if not value or len(value) > maximum or b"\x00" in value:
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fail(f"secret {name} is empty, unsafe, or exceeds its limit")
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values[name] = value
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return values
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def file_values(config: Mapping[str, Any], specs: Mapping[str, Mapping[str, Any]]) -> dict[str, bytes]:
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source = Path(required_string(object_value(config.get("file"), "file"), "path", "file"))
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if not source.is_absolute():
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fail("file.path must be absolute")
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try:
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metadata = source.lstat()
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except OSError as exc:
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fail(f"cannot inspect fallback secret directory: {exc.__class__.__name__}")
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if stat.S_ISLNK(metadata.st_mode) or not stat.S_ISDIR(metadata.st_mode):
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fail("fallback secret directory must be a non-symlink directory")
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if os.name != "nt" and stat.S_IMODE(metadata.st_mode) & 0o077:
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fail("fallback secret directory must be mode 0700 or stricter")
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expected = set(specs)
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actual = {entry.name for entry in source.iterdir()}
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if actual != expected:
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fail("fallback secret directory does not exactly match configured keys")
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values: dict[str, bytes] = {}
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for name, spec in specs.items():
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path = source / name
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private_file(path, f"fallback secret {name}")
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value = read_limited(path, int(spec.get("max_bytes", 65_536)), f"fallback secret {name}")
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if not value or b"\x00" in value:
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fail(f"fallback secret {name} is empty or unsafe")
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values[name] = value
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return values
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def materialize(runtime: Path, specs: Mapping[str, Mapping[str, Any]], values: Mapping[str, bytes]) -> list[str]:
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runtime.mkdir(parents=True, exist_ok=True, mode=0o700)
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if runtime.is_symlink():
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fail("runtime directory must not be a symlink")
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os.chmod(runtime, 0o700)
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paths: dict[str, Path] = {}
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for name, value in values.items():
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descriptor, temporary = tempfile.mkstemp(prefix=f".{name}.", dir=runtime)
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temporary_path = Path(temporary)
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with os.fdopen(descriptor, "wb") as stream:
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stream.write(value)
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stream.flush()
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os.fsync(stream.fileno())
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os.chmod(temporary_path, 0o444)
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destination = runtime / name
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os.replace(temporary_path, destination)
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paths[name] = destination
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consumers = sorted({consumer for spec in specs.values() for consumer in spec["consumers"]})
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for consumer in consumers:
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lines = [
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f'{name}_FILE="{paths[name].resolve()}"\n'
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for name, spec in sorted(specs.items())
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if consumer in spec["consumers"]
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]
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destination = runtime / f"{consumer}.env"
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destination.write_text("".join(lines), encoding="utf-8")
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os.chmod(destination, 0o600)
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manifest = runtime / "manifest"
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manifest.write_text("".join(f"{name}={path.resolve()}\n" for name, path in sorted(paths.items())), encoding="utf-8")
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os.chmod(manifest, 0o600)
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return consumers
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def run(config_path: Path, environ: Mapping[str, str] | None = None) -> list[str]:
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os.umask(0o077)
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config = load_json(config_path)
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if config.get("version") != 1 or config.get("mode") not in {"selectel", "file"}:
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fail("configuration version/mode is invalid")
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runtime = Path(required_string(config, "runtime_dir", "configuration"))
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if not runtime.is_absolute():
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fail("runtime_dir must be absolute")
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raw_specs = object_value(config.get("secrets"), "secrets")
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specs: dict[str, Mapping[str, Any]] = {}
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for name, spec_value in raw_specs.items():
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spec = object_value(spec_value, f"secrets.{name}")
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consumers = spec.get("consumers")
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if (
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not NAME_RE.fullmatch(name)
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or not isinstance(consumers, list)
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or not consumers
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or any(not isinstance(item, str) or not CONSUMER_RE.fullmatch(item) for item in consumers)
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):
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fail("secret name or consumer list is invalid")
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specs[name] = spec
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environment = os.environ if environ is None else environ
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values = fetch_values(config, specs, environment) if config["mode"] == "selectel" else file_values(config, specs)
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return materialize(runtime, specs, values)
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def main() -> int:
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parser = argparse.ArgumentParser()
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parser.add_argument("--config", required=True, type=Path)
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args = parser.parse_args()
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try:
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consumers = run(args.config)
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except (LoaderError, OSError, ValueError) as exc:
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print(f"secrets-loader: {exc}", file=sys.stderr)
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return 1
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print(f"secrets-loader: materialized {len(consumers)} VM2 consumer scopes", file=sys.stderr)
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return 0
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if __name__ == "__main__":
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raise SystemExit(main())
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