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move signature validation logic into signature validator

libp2p/pubsub/validators.py

@@ -1,14 +1,41 @@
-from libp2p.crypto.keys import PublicKey
+import logging
+
+from libp2p.crypto.serialization import deserialize_public_key
+from libp2p.peer.id import ID
+
+from .pb import rpc_pb2
+
+logger = logging.getLogger("libp2p.pubsub")
+
+PUBSUB_SIGNING_PREFIX = "libp2p-pubsub:"
 
 
-def signature_validator(pubkey: PublicKey, payload: bytes, signature: bytes) -> bool:
+def signature_validator(msg: rpc_pb2.Message) -> bool:
     """
     Verify the message against the given public key.
 
     :param pubkey: the public key which signs the message.
     :param msg: the message signed.
     """
+    # Check if signature is attached
+    if msg.signature == b"":
+        logger.debug("Reject because no signature attached for msg: %s", msg)
+        return False
+
+    # Validate if message sender matches message signer,
+    # i.e., check if `msg.key` matches `msg.from_id`
+    msg_pubkey = deserialize_public_key(msg.key)
+    if ID.from_pubkey(msg_pubkey) != msg.from_id:
+        logger.debug(
+            "Reject because signing key does not match sender ID for msg: %s", msg
+        )
+        return False
+    # First, construct the original payload that's signed by 'msg.key'
+    msg_without_key_sig = rpc_pb2.Message(
+        data=msg.data, topicIDs=msg.topicIDs, from_id=msg.from_id, seqno=msg.seqno
+    )
+    payload = PUBSUB_SIGNING_PREFIX.encode() + msg_without_key_sig.SerializeToString()
     try:
-        return pubkey.verify(payload, signature)
+        return msg_pubkey.verify(payload, msg.signature)
     except Exception:
         return False