Bypass ipfs hash validation for large files

Author: njgheorghita

ethpm/backends/ipfs.py

@@ -80,10 +80,13 @@ def __init__(self) -> None:
     def fetch_uri_contents(self, uri: str) -> bytes:
         ipfs_hash = extract_ipfs_path_from_uri(uri)
         contents = self.client.cat(ipfs_hash)
-        validation_hash = generate_file_hash(contents)
-        if validation_hash != ipfs_hash:
-            raise EthPMValidationError(
-                f"Hashed IPFS contents retrieved from uri: {uri} do not match its content hash."
+        # Local validation of hashed contents only works for non-chunked files ~< 256kb
+        # Improved validation WIP @ https://github.com/ethpm/py-ethpm/pull/165
+        if len(contents) <= 262144:
+            validation_hash = generate_file_hash(contents)
+            if validation_hash != ipfs_hash:
+                raise ValidationError(
+                    f"Hashed IPFS contents retrieved from uri: {uri} do not match its content hash."
             )
         return contents