260 lines
9.4 KiB
Python
260 lines
9.4 KiB
Python
"""
|
|
xtendr_signing.py
|
|
|
|
Core logic for signing XtendR plugins and maintaining a whitelist.
|
|
Deliberately kept free of any GTK/Adw imports so it can be unit tested
|
|
and reused by both the signer GUI and (later) XtendRSystem's verification
|
|
hook.
|
|
|
|
Design:
|
|
- Ed25519 keypair: private key stays with the signer, public key ships
|
|
inside XtendR / PyPac to verify at attach() time.
|
|
- Each whitelist entry covers the plugin's manifest (<name>.json) and its
|
|
module file (<module>.py), hashed together with SHA-256. The signature
|
|
covers the whole entry (hash + name + module + class), so an attacker
|
|
can't splice a valid hash onto a different plugin identity.
|
|
- The whitelist file itself can optionally be encrypted at rest with a
|
|
passphrase (Fernet / AES-128-CBC+HMAC via PBKDF2-derived key). This is
|
|
for confidentiality only -- the signature is what provides integrity,
|
|
and still verifies correctly whether or not the file on disk is
|
|
encrypted.
|
|
"""
|
|
from __future__ import annotations
|
|
|
|
import base64
|
|
import hashlib
|
|
import json
|
|
import os
|
|
from dataclasses import dataclass, asdict
|
|
from datetime import datetime, timezone
|
|
from pathlib import Path
|
|
from typing import Optional
|
|
|
|
from cryptography.hazmat.primitives.asymmetric.ed25519 import (
|
|
Ed25519PrivateKey,
|
|
Ed25519PublicKey,
|
|
)
|
|
from cryptography.hazmat.primitives import serialization
|
|
from cryptography.exceptions import InvalidSignature
|
|
from cryptography.fernet import Fernet, InvalidToken
|
|
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
|
|
from cryptography.hazmat.primitives import hashes
|
|
|
|
PBKDF2_ITERATIONS = 600_000
|
|
|
|
|
|
# --------------------------------------------------------------------------
|
|
# Key management
|
|
# --------------------------------------------------------------------------
|
|
|
|
def generate_keypair(private_path: Path, public_path: Path) -> None:
|
|
"""Generate a new Ed25519 keypair and write it to disk (unencrypted PEM).
|
|
|
|
Caller is responsible for keeping private_path safe (e.g. 0600 perms,
|
|
offline machine, backups). This is deliberately not done automatically
|
|
since the right answer depends on the user's environment.
|
|
"""
|
|
private_path.parent.mkdir(parents=True, exist_ok=True)
|
|
key = Ed25519PrivateKey.generate()
|
|
|
|
priv_bytes = key.private_bytes(
|
|
encoding=serialization.Encoding.PEM,
|
|
format=serialization.PrivateFormat.PKCS8,
|
|
encryption_algorithm=serialization.NoEncryption(),
|
|
)
|
|
pub_bytes = key.public_key().public_bytes(
|
|
encoding=serialization.Encoding.PEM,
|
|
format=serialization.PublicFormat.SubjectPublicKeyInfo,
|
|
)
|
|
|
|
private_path.write_bytes(priv_bytes)
|
|
try:
|
|
os.chmod(private_path, 0o600)
|
|
except OSError:
|
|
pass
|
|
public_path.write_bytes(pub_bytes)
|
|
|
|
|
|
def load_private_key(path: Path) -> Ed25519PrivateKey:
|
|
key = serialization.load_pem_private_key(path.read_bytes(), password=None)
|
|
if not isinstance(key, Ed25519PrivateKey):
|
|
raise ValueError(f"'{path}' is not an Ed25519 private key.")
|
|
return key
|
|
|
|
|
|
def load_public_key(path: Path) -> Ed25519PublicKey:
|
|
key = serialization.load_pem_public_key(path.read_bytes())
|
|
if not isinstance(key, Ed25519PublicKey):
|
|
raise ValueError(f"'{path}' is not an Ed25519 public key.")
|
|
return key
|
|
|
|
|
|
# --------------------------------------------------------------------------
|
|
# Plugin hashing + entry signing
|
|
# --------------------------------------------------------------------------
|
|
|
|
@dataclass
|
|
class PluginEntry:
|
|
name: str # plugin folder name
|
|
module: str # module name, from the manifest
|
|
cls: str # class name, from the manifest
|
|
sha256: str # hash of manifest + module file contents
|
|
signed_at: str # ISO-8601 UTC timestamp
|
|
signature: str = "" # base64 Ed25519 signature, filled in after signing
|
|
|
|
def canonical_bytes(self) -> bytes:
|
|
"""Bytes that get signed / verified -- everything except the
|
|
signature itself, in a stable, sorted-key JSON encoding."""
|
|
payload = {
|
|
"name": self.name,
|
|
"module": self.module,
|
|
"cls": self.cls,
|
|
"sha256": self.sha256,
|
|
"signed_at": self.signed_at,
|
|
}
|
|
return json.dumps(payload, sort_keys=True, separators=(",", ":")).encode("utf-8")
|
|
|
|
|
|
def hash_plugin_files(plugin_dir: Path, name: str, module: str) -> str:
|
|
"""Hash the manifest + module file together, in a fixed order, so the
|
|
hash changes if either file is tampered with."""
|
|
manifest_path = plugin_dir / f"{name}.json"
|
|
module_path = plugin_dir / f"{module}.py"
|
|
if not manifest_path.is_file():
|
|
raise FileNotFoundError(f"Manifest not found: {manifest_path}")
|
|
if not module_path.is_file():
|
|
raise FileNotFoundError(f"Module file not found: {module_path}")
|
|
|
|
h = hashlib.sha256()
|
|
for p in (manifest_path, module_path):
|
|
h.update(p.name.encode("utf-8"))
|
|
h.update(b"\x00")
|
|
h.update(p.read_bytes())
|
|
h.update(b"\x00")
|
|
return h.hexdigest()
|
|
|
|
|
|
def sign_plugin(private_key: Ed25519PrivateKey, plugin_dir: Path) -> PluginEntry:
|
|
manifest_path_glob = list(plugin_dir.glob("*.json"))
|
|
if len(manifest_path_glob) != 1:
|
|
raise ValueError(
|
|
f"Expected exactly one manifest .json in '{plugin_dir}', found {len(manifest_path_glob)}."
|
|
)
|
|
manifest = json.loads(manifest_path_glob[0].read_text(encoding="utf-8"))
|
|
module = manifest.get("module")
|
|
cls = manifest.get("class")
|
|
if not module or not cls:
|
|
raise ValueError("Manifest is missing 'module' or 'class'.")
|
|
|
|
name = plugin_dir.name
|
|
digest = hash_plugin_files(plugin_dir, name, module)
|
|
entry = PluginEntry(
|
|
name=name,
|
|
module=module,
|
|
cls=cls,
|
|
sha256=digest,
|
|
signed_at=datetime.now(timezone.utc).isoformat(timespec="seconds"),
|
|
)
|
|
signature = private_key.sign(entry.canonical_bytes())
|
|
entry.signature = base64.b64encode(signature).decode("ascii")
|
|
return entry
|
|
|
|
|
|
def verify_entry(public_key: Ed25519PublicKey, entry: PluginEntry) -> bool:
|
|
try:
|
|
public_key.verify(base64.b64decode(entry.signature), entry.canonical_bytes())
|
|
return True
|
|
except (InvalidSignature, ValueError):
|
|
return False
|
|
|
|
|
|
def verify_plugin_on_disk(public_key: Ed25519PublicKey, plugin_dir: Path, entry: PluginEntry) -> bool:
|
|
"""Full verification: signature is valid AND the files on disk still
|
|
match the hash that was signed."""
|
|
if not verify_entry(public_key, entry):
|
|
return False
|
|
try:
|
|
current_hash = hash_plugin_files(plugin_dir, entry.name, entry.module)
|
|
except FileNotFoundError:
|
|
return False
|
|
return current_hash == entry.sha256
|
|
|
|
|
|
# --------------------------------------------------------------------------
|
|
# Whitelist storage (optionally encrypted at rest)
|
|
# --------------------------------------------------------------------------
|
|
|
|
class Whitelist:
|
|
def __init__(self):
|
|
self.entries: dict[str, PluginEntry] = {}
|
|
|
|
def add(self, entry: PluginEntry) -> None:
|
|
self.entries[entry.name] = entry
|
|
|
|
def remove(self, name: str) -> bool:
|
|
return self.entries.pop(name, None) is not None
|
|
|
|
def to_json(self) -> str:
|
|
payload = {name: asdict(e) for name, e in self.entries.items()}
|
|
return json.dumps(payload, indent=2, sort_keys=True)
|
|
|
|
@classmethod
|
|
def from_json(cls, data: str) -> "Whitelist":
|
|
wl = cls()
|
|
raw = json.loads(data)
|
|
for name, fields in raw.items():
|
|
wl.entries[name] = PluginEntry(**fields)
|
|
return wl
|
|
|
|
# -- disk I/O -----------------------------------------------------
|
|
|
|
def save(self, path: Path, passphrase: Optional[str] = None) -> None:
|
|
plaintext = self.to_json().encode("utf-8")
|
|
if passphrase is None:
|
|
path.write_bytes(plaintext)
|
|
return
|
|
|
|
salt = os.urandom(16)
|
|
key = _derive_key(passphrase, salt)
|
|
token = Fernet(key).encrypt(plaintext)
|
|
container = {
|
|
"encrypted": True,
|
|
"kdf": "pbkdf2-sha256",
|
|
"iterations": PBKDF2_ITERATIONS,
|
|
"salt": base64.b64encode(salt).decode("ascii"),
|
|
"data": base64.b64encode(token).decode("ascii"),
|
|
}
|
|
path.write_text(json.dumps(container, indent=2), encoding="utf-8")
|
|
|
|
@classmethod
|
|
def load(cls, path: Path, passphrase: Optional[str] = None) -> "Whitelist":
|
|
raw = path.read_text(encoding="utf-8")
|
|
try:
|
|
container = json.loads(raw)
|
|
except json.JSONDecodeError:
|
|
container = None
|
|
|
|
if isinstance(container, dict) and container.get("encrypted"):
|
|
if passphrase is None:
|
|
raise ValueError("Whitelist is encrypted; a passphrase is required.")
|
|
salt = base64.b64decode(container["salt"])
|
|
key = _derive_key(passphrase, salt, container.get("iterations", PBKDF2_ITERATIONS))
|
|
token = base64.b64decode(container["data"])
|
|
try:
|
|
plaintext = Fernet(key).decrypt(token).decode("utf-8")
|
|
except InvalidToken as e:
|
|
raise ValueError("Wrong passphrase or corrupted whitelist file.") from e
|
|
return cls.from_json(plaintext)
|
|
|
|
return cls.from_json(raw)
|
|
|
|
|
|
def _derive_key(passphrase: str, salt: bytes, iterations: int = PBKDF2_ITERATIONS) -> bytes:
|
|
kdf = PBKDF2HMAC(
|
|
algorithm=hashes.SHA256(),
|
|
length=32,
|
|
salt=salt,
|
|
iterations=iterations,
|
|
)
|
|
return base64.urlsafe_b64encode(kdf.derive(passphrase.encode("utf-8")))
|