Verification configured. /JL

README.md

@@ -1,4 +1,5 @@
 # XtendR
+![Latest Version](https://gitpot.lerk.ing/badges/badge/static?label=Latest+version&message=0.5.1&color=blue)
 
 A very basic Python 3.12 friendly plugin system based on the K.I.S.S principle.
 

requirements.txt

@@ -1 +1,2 @@
 setuptools==68.2.2
+cryptography>=42

setup.py

@@ -6,7 +6,7 @@ if __name__ == "__main__":
 
     setup(
         name="XtendR",
-        version="0.4.0",
+        version="0.5.1",
         packages=find_packages(),
         install_requires=[],
         author="Jan Lerking",

xtendr/signing.py

@@ -0,0 +1,259 @@
+"""
+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")))

xtendr/xtendrsystem.py

@@ -6,9 +6,11 @@ import json
 import stat
 import logging
 import threading
+from pathlib import Path
 from xtendr.xtendrbase import XtendRBase
+from xtendr import signing as xsign
 
-__version__ = "0.4.0"
+__version__ = "0.5.0"
 
 logger = logging.getLogger("xtendr")
 
@@ -18,6 +20,11 @@ logger = logging.getLogger("xtendr")
 _NAME_RE = re.compile(r"^[A-Za-z0-9_-]+$")
 _MODULE_RE = re.compile(r"^[A-Za-z_][A-Za-z0-9_]*$")
 
+# Signature status values stored in plugins[name]["signature"]["status"].
+SIG_VERIFIED = "verified"   # whitelist entry present, signature and hash both check out
+SIG_UNSIGNED = "unsigned"   # no whitelist entry for this plugin at all
+SIG_INVALID = "invalid"     # whitelist entry present but signature/hash mismatch (tampered)
+
 
 class XtendRSystem:
     """Plugin system to manage plugins.
@@ -30,7 +37,7 @@ class XtendRSystem:
     Example:
     >>> system = XtendRSystem()
     >>> system.version()
-    XtendR v0.4.0
+    XtendR v0.5.0
     >>> system.attach("example_plugin", lambda: None)
     >>> system.run("example_plugin")
     ExamplePlugin is running!
@@ -40,20 +47,81 @@ class XtendRSystem:
     Detached plugin 'example_plugin'.
     """
 
-    def __init__(self, pluginpath="plugins"):
+    def __init__(self, pluginpath="plugins", public_key_path=None, whitelist_path=None, whitelist_passphrase=None):
         self.pluginspath = pluginpath
         self.plugins = {}
         self._lock = threading.RLock()
 
+        # -- signature verification setup ---------------------------------
+        # If either the public key or the whitelist can't be loaded, we
+        # fail closed: self._public_key / self._whitelist stay None, and
+        # every plugin will come back as SIG_UNSIGNED (disabled) rather
+        # than silently skipping verification. This is deliberate -- an
+        # admin who wants unsigned plugins to run should not be able to
+        # get there by accident (e.g. a missing/misspelled key path).
+        self._public_key = None
+        self._whitelist = None
+
+        if public_key_path is not None:
+            try:
+                self._public_key = xsign.load_public_key(Path(public_key_path))
+            except (OSError, ValueError) as e:
+                logger.error("Could not load XtendR public key from '%s': %s", public_key_path, e)
+
+        if whitelist_path is not None:
+            try:
+                self._whitelist = xsign.Whitelist.load(Path(whitelist_path), whitelist_passphrase)
+            except (OSError, ValueError) as e:
+                logger.error("Could not load XtendR plugin whitelist from '%s': %s", whitelist_path, e)
+
+        if self._public_key is None or self._whitelist is None:
+            logger.warning(
+                "Signature verification is not fully configured for pluginpath '%s'; "
+                "all plugins will be treated as unsigned and permanently disabled.",
+                pluginpath,
+            )
+
     def version(self) -> str:
         return "XtendR v" + __version__
 
+    @property
+    def verification_configured(self) -> bool:
+        """True if a public key and whitelist both loaded successfully."""
+        return self._public_key is not None and self._whitelist is not None
+
     def _validate_name(self, name: str) -> bool:
         if not isinstance(name, str) or not _NAME_RE.match(name):
             logger.error("Rejected plugin name %r: must match %s", name, _NAME_RE.pattern)
             return False
         return True
 
+    def _verify_signature(self, name: str, plugin_path: str, module_name: str) -> dict:
+        """Check a plugin's signature against the loaded whitelist.
+
+        Returns a dict with at least a "status" key (SIG_VERIFIED /
+        SIG_UNSIGNED / SIG_INVALID) plus whatever whitelist metadata is
+        available, for display in the UI. Never raises.
+        """
+        result = {"status": SIG_UNSIGNED, "sha256": None, "signature": None, "signed_at": None}
+
+        if self._public_key is None or self._whitelist is None:
+            return result
+
+        entry = self._whitelist.entries.get(name)
+        if entry is None:
+            return result
+
+        result.update(sha256=entry.sha256, signature=entry.signature, signed_at=entry.signed_at)
+
+        try:
+            ok = xsign.verify_plugin_on_disk(self._public_key, Path(plugin_path), entry)
+        except Exception:  # noqa: BLE001 - never let a verification bug crash attach()
+            logger.error("Signature verification raised for plugin '%s'.", name, exc_info=True)
+            ok = False
+
+        result["status"] = SIG_VERIFIED if ok else SIG_INVALID
+        return result
+
     def _check_permissions(self, path: str) -> None:
         """Warn (don't block) if a plugin file is group/world-writable."""
         try:
@@ -116,6 +184,33 @@ class XtendRSystem:
 
             self._check_permissions(module_file)
 
+            # Verify the plugin's signature BEFORE we ever execute its code.
+            # Unsigned/tampered plugins still get a listing entry (built
+            # from the manifest alone, which is inert JSON) but their .py
+            # file is never imported, and they can never be run.
+            sig = self._verify_signature(name, plugin_path, module_name)
+            if sig["status"] != SIG_VERIFIED:
+                if sig["status"] == SIG_INVALID:
+                    logger.error(
+                        "Plugin '%s' failed signature verification (tampered or bad "
+                        "signature); attaching as permanently disabled.", name,
+                    )
+                else:
+                    logger.warning(
+                        "Plugin '%s' has no valid whitelist entry; attaching as "
+                        "permanently disabled.", name,
+                    )
+                self.plugins[name] = {
+                    "instance": None,
+                    "running": False,
+                    "info": plugin_info,
+                    "autorun": False,
+                    "module_key": None,
+                    "disabled": True,
+                    "signature": sig,
+                }
+                return
+
             # Load the module directly from its file path instead of
             # mutating sys.path. This prevents a plugin from shadowing
             # stdlib or third-party modules for the rest of the process.
@@ -147,6 +242,8 @@ class XtendRSystem:
                 "info": plugin_info,
                 "autorun": False,
                 "module_key": qualified_name,
+                "disabled": False,
+                "signature": sig,
             }
             logger.info("Attached plugin '%s'.", name)
             logger.info("Running pre-load on '%s'.", name)
@@ -167,6 +264,9 @@ class XtendRSystem:
         if entry is None:
             logger.error("Plugin '%s' not found or has no 'run' method.", name)
             return
+        if entry.get("disabled"):
+            logger.error("Plugin '%s' is disabled (failed signature verification) and cannot run.", name)
+            return
         entry["running"] = True
         try:
             return entry["instance"].run(*args, **kwargs)
@@ -194,5 +294,6 @@ class XtendRSystem:
             if entry is None:
                 logger.info("Plugin '%s' is not attached.", name)
                 return
-            sys.modules.pop(entry["module_key"], None)
+            if entry.get("module_key"):
+                sys.modules.pop(entry["module_key"], None)
             logger.info("Detached plugin '%s'.", name)