feat: add aleph.sdk.security module

Co-authored-by: Laurent Peuch <cortex@worlddomination.be>
Co-authored-by: Hugo Herter <git@hugoherter.com>

src/aleph/sdk/security.py

@@ -0,0 +1,64 @@
+from importlib import import_module
+from typing import Callable, Dict, Optional, Union
+
+from aleph_message.models import AlephMessage, Chain
+
+from aleph.sdk.chains.common import get_verification_buffer
+from aleph.sdk.query.responses import Post
+
+
+def _try_import_verify_signature(
+    chain: str,
+) -> Optional[
+    Callable[[Union[bytes, str], Union[bytes, str], Union[bytes, str]], None]
+]:
+    """Try to import a chain signature validator."""
+    try:
+        return import_module(f"aleph.sdk.chains.{chain}").verify_signature
+    except (ImportError, AttributeError):
+        return None
+
+
+# This is a dict containing all currently available signature validators,
+# indexed by their Chain abbreviation.
+#
+# Ex.: validators["SOL"] -> aleph.sdk.chains.solana.verify_signature()
+VALIDATORS: Dict[
+    Chain,
+    Optional[Callable[[Union[bytes, str], Union[bytes, str], Union[bytes, str]], None]],
+] = {
+    key: _try_import_verify_signature(value)
+    for key, value in {
+        # TODO: Add AVAX
+        Chain.ETH: "ethereum",
+        Chain.SOL: "sol",
+        Chain.CSDK: "cosmos",
+        Chain.DOT: "substrate",
+        Chain.NULS2: "nuls2",
+        Chain.TEZOS: "tezos",
+    }.items()
+}
+
+
+def verify_message_signature(message: Union[AlephMessage, Post]) -> None:
+    """Verify the signature of a message, raise an error if invalid or unsupported.
+    A BadSignatureError is raised when the signature is incorrect.
+    A ValueError is raised when the chain is not supported or required dependencies are  missing.
+    """
+    if message.chain not in VALIDATORS:
+        raise ValueError(f"Chain {message.chain} is not supported.")
+
+    validator = VALIDATORS[message.chain]
+    if validator is None:
+        raise ValueError(
+            f"Chain {message.chain} is not installed. Install it with `aleph-sdk-python[{message.chain}]`."
+        )
+
+    signature = message.signature
+    public_key = message.sender
+    message = get_verification_buffer(message.dict())
+
+    # to please mypy
+    assert isinstance(signature, (str, bytes))
+
+    validator(signature, public_key, message)

tests/unit/test_security.py

@@ -0,0 +1,4 @@
+def test_validators_loaded():
+    import aleph.sdk.security as security
+
+    assert any([validator is not None for validator in security.validators.values()])