Spaces:
Running
Running
File size: 11,105 Bytes
3052732 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 | """Root-owned immutable executable identities for the sealed-exec boundary.
The policy is deliberately small. It is not a general application sandbox:
it answers one question for the native listener, namely whether a newly
requested executable image is the exact root-controlled object that an
operator selected before launch.
"""
from __future__ import annotations
import hashlib
import os
import re
import stat
import time
from pathlib import Path
from typing import Any
from .jsonio import JsonInputError, canonical_bytes, load_regular_json
from .records import write_atomic
SCHEMA = "lumi-eggcracker.exec-policy.v1"
NAME = re.compile(r"[A-Za-z0-9][A-Za-z0-9._-]{0,63}\Z")
HEX = re.compile(r"[0-9a-f]{64}\Z")
POLICY_ID = re.compile(r"[0-9a-f]{24}\Z")
MAX_EXECUTABLES = 32
MAX_EXECUTABLE_BYTES = 512 * 1024 * 1024
STATE_DIR = Path("/var/lib/lumi-eggcracker/exec-policies")
def _root_controlled(path: Path) -> bool:
if not path.is_absolute() or Path(os.path.normpath(str(path))) != path:
return False
for item in (path, *path.parents):
try:
metadata = item.lstat()
except OSError:
return False
if metadata.st_uid != 0:
return False
if not stat.S_ISLNK(metadata.st_mode) and metadata.st_mode & 0o022:
return False
return True
def _hash_descriptor(descriptor: int, metadata: os.stat_result) -> str:
if not stat.S_ISREG(metadata.st_mode) or not 1 <= metadata.st_size <= MAX_EXECUTABLE_BYTES:
raise JsonInputError("execution policy executable is outside the supported size bound")
before = (
metadata.st_dev,
metadata.st_ino,
metadata.st_size,
metadata.st_mtime_ns,
metadata.st_ctime_ns,
)
os.lseek(descriptor, 0, os.SEEK_SET)
digest = hashlib.sha256()
remaining = metadata.st_size
while remaining:
block = os.read(descriptor, min(1024 * 1024, remaining))
if not block:
raise JsonInputError("execution policy executable changed during hashing")
digest.update(block)
remaining -= len(block)
after_metadata = os.fstat(descriptor)
after = (
after_metadata.st_dev,
after_metadata.st_ino,
after_metadata.st_size,
after_metadata.st_mtime_ns,
after_metadata.st_ctime_ns,
)
if after != before:
raise JsonInputError("execution policy executable changed during hashing")
return digest.hexdigest()
def inspect_executable(path_text: str) -> dict[str, Any]:
"""Capture one immutable root-controlled executable identity."""
if not isinstance(path_text, str) or not path_text or len(path_text) > 4096:
raise JsonInputError("execution policy executable path is invalid")
supplied = Path(path_text)
if not _root_controlled(supplied):
raise JsonInputError("execution policy executable path must be root-controlled")
try:
resolved = supplied.resolve(strict=True)
except OSError as error:
raise JsonInputError("execution policy executable cannot be resolved") from error
if not _root_controlled(resolved):
raise JsonInputError("resolved execution policy executable is not root-controlled")
flags = os.O_RDONLY | getattr(os, "O_CLOEXEC", 0) | getattr(os, "O_NOFOLLOW", 0)
try:
descriptor = os.open(resolved, flags)
except OSError as error:
raise JsonInputError("execution policy executable cannot be opened") from error
try:
metadata = os.fstat(descriptor)
if (
not stat.S_ISREG(metadata.st_mode)
or metadata.st_uid != 0
or metadata.st_mode & 0o022
or not (metadata.st_mode & 0o111)
):
raise JsonInputError("execution policy target must be a root-owned executable")
digest = _hash_descriptor(descriptor, metadata)
return {
"device": metadata.st_dev,
"inode": metadata.st_ino,
"mode": stat.S_IMODE(metadata.st_mode),
"path": str(resolved),
"sha256": digest,
"size": metadata.st_size,
"uid": metadata.st_uid,
}
finally:
os.close(descriptor)
def _validate_entry(value: Any) -> dict[str, Any]:
if not isinstance(value, dict) or set(value) != {
"device", "inode", "mode", "path", "sha256", "size", "uid"
}:
raise JsonInputError("execution policy executable identity is invalid")
if (
not isinstance(value["path"], str)
or not value["path"].startswith("/")
or not isinstance(value["sha256"], str)
or HEX.fullmatch(value["sha256"]) is None
):
raise JsonInputError("execution policy executable identity is invalid")
for key in ("device", "inode", "mode", "size", "uid"):
if isinstance(value[key], bool) or not isinstance(value[key], int) or value[key] < 0:
raise JsonInputError("execution policy executable integer is invalid")
if value["uid"] != 0 or value["size"] < 1 or value["size"] > MAX_EXECUTABLE_BYTES:
raise JsonInputError("execution policy executable owner or size is invalid")
return value
def _digest(value: dict[str, Any]) -> str:
body = {key: value[key] for key in value if key != "digest"}
return hashlib.sha256(canonical_bytes(body)).hexdigest()
def validate(value: dict[str, Any]) -> dict[str, Any]:
expected = {
"created_monotonic_ns", "creator_uid", "digest", "executables", "generation",
"name", "policy_id", "revoked", "schema_version",
}
if set(value) != expected or value.get("schema_version") != SCHEMA:
raise JsonInputError("execution policy schema is invalid")
if not isinstance(value["name"], str) or NAME.fullmatch(value["name"]) is None:
raise JsonInputError("execution policy name is invalid")
if not isinstance(value["policy_id"], str) or POLICY_ID.fullmatch(value["policy_id"]) is None:
raise JsonInputError("execution policy identity is invalid")
if not isinstance(value["digest"], str) or HEX.fullmatch(value["digest"]) is None:
raise JsonInputError("execution policy digest is invalid")
for key in ("created_monotonic_ns", "creator_uid", "generation"):
if isinstance(value[key], bool) or not isinstance(value[key], int) or value[key] < 0:
raise JsonInputError("execution policy integer is invalid")
if value["creator_uid"] != 0 or value["generation"] < 1 or not isinstance(value["revoked"], bool):
raise JsonInputError("execution policy authority or state is invalid")
entries = value["executables"]
if not isinstance(entries, list) or not 1 <= len(entries) <= MAX_EXECUTABLES:
raise JsonInputError("execution policy executable count is invalid")
checked = [_validate_entry(entry) for entry in entries]
identities = {(item["device"], item["inode"], item["size"], item["sha256"]) for item in checked}
if len(identities) != len(checked):
raise JsonInputError("execution policy executable identity is duplicated")
if _digest(value) != value["digest"]:
raise JsonInputError("execution policy digest does not match contents")
return value
def _path(root: Path, name: str) -> Path:
if not isinstance(name, str) or NAME.fullmatch(name) is None:
raise JsonInputError("execution policy name is invalid")
return root / f"{name}.json"
def create(root: Path, *, name: str, paths: list[str], creator_uid: int = 0) -> dict[str, Any]:
if creator_uid != 0 or not isinstance(paths, list) or not 1 <= len(paths) <= MAX_EXECUTABLES:
raise JsonInputError("execution policy arguments are invalid")
destination = _path(root, name)
if destination.exists() or destination.is_symlink():
raise JsonInputError("execution policy name is unavailable")
entries = [inspect_executable(item) for item in paths]
value = {
"created_monotonic_ns": time.monotonic_ns(),
"creator_uid": 0,
"digest": "0" * 64,
"executables": entries,
"generation": 1,
"name": name,
"policy_id": os.urandom(12).hex(),
"revoked": False,
"schema_version": SCHEMA,
}
value["digest"] = _digest(value)
value = validate(value)
root.mkdir(mode=0o700, parents=True, exist_ok=True)
os.chown(root, 0, 0)
os.chmod(root, 0o700)
write_atomic(destination, value)
os.chown(destination, 0, 0)
os.chmod(destination, 0o600)
return value
def load_all(root: Path = STATE_DIR) -> list[dict[str, Any]]:
if not root.exists():
return []
if root.is_symlink() or not root.is_dir():
raise JsonInputError("execution policy root is invalid")
values: list[dict[str, Any]] = []
for path in sorted(root.glob("*.json")):
value = validate(load_regular_json(path))
if value["name"] != path.stem:
raise JsonInputError("execution policy name/path mismatch")
values.append(value)
return values
def load(root: Path, policy_id: str) -> dict[str, Any]:
for value in load_all(root):
if value["policy_id"] == policy_id:
if value["revoked"]:
raise JsonInputError("execution policy is revoked")
return value
raise JsonInputError("execution policy is unavailable")
def revoke(root: Path, policy_id: str) -> dict[str, Any]:
values = load_all(root)
for value in values:
if value["policy_id"] == policy_id:
path = _path(root, value["name"])
replacement = dict(value)
replacement["revoked"] = True
replacement["generation"] = value["generation"] + 1
replacement["digest"] = _digest(replacement)
write_atomic(path, validate(replacement))
return {"policy_id": policy_id, "result": "REVOKED"}
raise JsonInputError("execution policy is unavailable")
def public(value: dict[str, Any]) -> dict[str, Any]:
checked = validate(value)
return {
"digest": checked["digest"],
"executable_count": len(checked["executables"]),
"generation": checked["generation"],
"name": checked["name"],
"policy_id": checked["policy_id"],
"revoked": checked["revoked"],
}
def ephemeral(path: str, run_id: str) -> dict[str, Any]:
"""Build a non-persistent policy for the default initial executable."""
entry = inspect_executable(path)
value = {
"created_monotonic_ns": time.monotonic_ns(),
"creator_uid": 0,
"digest": "0" * 64,
"executables": [entry],
"generation": 1,
"name": f"sealed-{run_id}",
"policy_id": run_id,
"revoked": False,
"schema_version": SCHEMA,
}
value["digest"] = _digest(value)
return validate(value)
def match_identity(policy: dict[str, Any], identity: dict[str, Any]) -> bool:
validate(policy)
return any(
all(identity.get(key) == entry.get(key) for key in ("device", "inode", "size", "sha256"))
for entry in policy["executables"]
)
|