Validate encoding of extrinsics passed to runtime

primitives/api/proc-macro/src/decl_runtime_apis.rs

@@ -191,7 +191,8 @@ fn generate_native_call_generators(decl: &ItemTrait) -> Result<TokenStream> {
 				input: &I, error_desc: &'static str,
 			) -> std::result::Result<R, String>
 		{
-			<R as #crate_::Decode>::decode(
+			<R as #crate_::DecodeLimit>::decode_with_depth_limit(
+				#crate_::MAX_EXTRINSIC_DEPTH,
 				&mut &#crate_::Encode::encode(input)[..],
 			).map_err(|e| format!("{} {}", error_desc, e.what()))
 		}

primitives/api/proc-macro/src/impl_runtime_apis.rs

@@ -83,7 +83,10 @@ fn generate_impl_call(
 	Ok(
 		quote!(
 			#(
-				let #pnames : #ptypes = match #c_iter::Decode::decode(&mut #input) {
+				let #pnames : #ptypes = match #c_iter::DecodeLimit::decode_all_with_depth_limit(
+					#c_iter::MAX_EXTRINSIC_DEPTH,
+					&mut #input
+				) {
 					Ok(input) => input,
 					Err(e) => panic!("Bad input data provided to {}: {}", #fn_name_str, e.what()),
 				};

primitives/api/src/lib.rs

@@ -69,11 +69,14 @@ pub use sp_std::{slice, mem};
 #[cfg(feature = "std")]
 use sp_std::result;
 #[doc(hidden)]
-pub use codec::{Encode, Decode};
+pub use codec::{Encode, Decode, DecodeLimit};
 use sp_core::OpaqueMetadata;
 #[cfg(feature = "std")]
 use std::{panic::UnwindSafe, cell::RefCell};
 
+/// Maximum nesting level for extrinsics.
+pub const MAX_EXTRINSIC_DEPTH: u32 = 256;
+
 /// Declares given traits as runtime apis.
 ///
 /// The macro will create two declarations, one for using on the client side and one for using