[pallet-revive] implement tx origin API (#6105)

Implement a syscall to retreive the transaction origin.

---------

Signed-off-by: Cyrill Leutwiler <[email protected]>
Signed-off-by: xermicus <[email protected]>
Co-authored-by: GitHub Action <[email protected]>
Co-authored-by: command-bot <>
Co-authored-by: Alexander Theißen <[email protected]>

prdoc/pr_6105.prdoc

@@ -0,0 +1,14 @@
+title: '[pallet-revive] implement tx origin API'
+
+doc:
+- audience:
+  - Runtime Dev
+  description: Implement a syscall to retreive the transaction origin.
+
+crates:
+- name: pallet-revive
+  bump: minor
+- name: pallet-revive-uapi
+  bump: minor
+- name: pallet-revive-fixtures
+  bump: patch

substrate/frame/revive/fixtures/contracts/origin.rs

@@ -0,0 +1,62 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Tests that the `origin` syscall works.
+//! The fixture returns the observed origin if the caller is not the origin,
+//! otherwise call itself recursively and assert the returned origin to match.
+
+#![no_std]
+#![no_main]
+
+extern crate common;
+use uapi::{HostFn, HostFnImpl as api};
+
+#[no_mangle]
+#[polkavm_derive::polkavm_export]
+pub extern "C" fn deploy() {}
+
+#[no_mangle]
+#[polkavm_derive::polkavm_export]
+pub extern "C" fn call() {
+	let mut caller = [0; 20];
+	api::caller(&mut caller);
+
+	let mut origin = [0; 20];
+	api::origin(&mut origin);
+
+	if caller != origin {
+		api::return_value(Default::default(), &origin);
+	}
+
+	let mut addr = [0u8; 20];
+	api::address(&mut addr);
+
+	let mut buf = [0u8; 20];
+	api::call(
+		uapi::CallFlags::ALLOW_REENTRY,
+		&addr,
+		0u64,
+		0u64,
+		None,
+		&[0; 32],
+		&[],
+		Some(&mut &mut buf[..]),
+	)
+	.unwrap();
+
+	assert_eq!(buf, origin);
+}

substrate/frame/revive/src/benchmarking/mod.rs

@@ -523,6 +523,24 @@ mod benchmarks {
 		);
 	}
 
+	#[benchmark(pov_mode = Measured)]
+	fn seal_origin() {
+		let len = H160::len_bytes();
+		build_runtime!(runtime, memory: [vec![0u8; len as _], ]);
+
+		let result;
+		#[block]
+		{
+			result = runtime.bench_origin(memory.as_mut_slice(), 0);
+		}
+
+		assert_ok!(result);
+		assert_eq!(
+			<H160 as Decode>::decode(&mut &memory[..]).unwrap(),
+			T::AddressMapper::to_address(&runtime.ext().origin().account_id().unwrap())
+		);
+	}
+
 	#[benchmark(pov_mode = Measured)]
 	fn seal_is_contract() {
 		let Contract { account_id, .. } =

substrate/frame/revive/src/exec.rs

@@ -284,6 +284,9 @@ pub trait Ext: sealing::Sealed {
 	/// Returns the caller.
 	fn caller(&self) -> Origin<Self::T>;
 
+	/// Return the origin of the whole call stack.
+	fn origin(&self) -> &Origin<Self::T>;
+
 	/// Check if a contract lives at the specified `address`.
 	fn is_contract(&self, address: &H160) -> bool;
 
@@ -1547,6 +1550,10 @@ where
 		}
 	}
 
+	fn origin(&self) -> &Origin<T> {
+		&self.origin
+	}
+
 	fn is_contract(&self, address: &H160) -> bool {
 		ContractInfoOf::<T>::contains_key(&address)
 	}
@@ -2381,6 +2388,71 @@ mod tests {
 		assert_eq!(WitnessedCallerCharlie::get(), Some(BOB_ADDR));
 	}
 
+	#[test]
+	fn origin_returns_proper_values() {
+		parameter_types! {
+			static WitnessedCallerBob: Option<H160> = None;
+			static WitnessedCallerCharlie: Option<H160> = None;
+		}
+
+		let bob_ch = MockLoader::insert(Call, |ctx, _| {
+			// Record the origin for bob.
+			WitnessedCallerBob::mutate(|witness| {
+				let origin = ctx.ext.origin();
+				*witness = Some(<Test as Config>::AddressMapper::to_address(
+					&origin.account_id().unwrap(),
+				));
+			});
+
+			// Call into CHARLIE contract.
+			assert_matches!(
+				ctx.ext.call(
+					Weight::zero(),
+					U256::zero(),
+					&CHARLIE_ADDR,
+					U256::zero(),
+					vec![],
+					true,
+					false
+				),
+				Ok(_)
+			);
+			exec_success()
+		});
+		let charlie_ch = MockLoader::insert(Call, |ctx, _| {
+			// Record the origin for charlie.
+			WitnessedCallerCharlie::mutate(|witness| {
+				let origin = ctx.ext.origin();
+				*witness = Some(<Test as Config>::AddressMapper::to_address(
+					&origin.account_id().unwrap(),
+				));
+			});
+			exec_success()
+		});
+
+		ExtBuilder::default().build().execute_with(|| {
+			place_contract(&BOB, bob_ch);
+			place_contract(&CHARLIE, charlie_ch);
+			let origin = Origin::from_account_id(ALICE);
+			let mut storage_meter = storage::meter::Meter::new(&origin, 0, 0).unwrap();
+
+			let result = MockStack::run_call(
+				origin,
+				BOB_ADDR,
+				&mut GasMeter::<Test>::new(GAS_LIMIT),
+				&mut storage_meter,
+				0,
+				vec![],
+				None,
+			);
+
+			assert_matches!(result, Ok(_));
+		});
+
+		assert_eq!(WitnessedCallerBob::get(), Some(ALICE_ADDR));
+		assert_eq!(WitnessedCallerCharlie::get(), Some(ALICE_ADDR));
+	}
+
 	#[test]
 	fn is_contract_returns_proper_values() {
 		let bob_ch = MockLoader::insert(Call, |ctx, _| {

substrate/frame/revive/src/tests.rs

@@ -4476,6 +4476,22 @@ mod run_tests {
 		});
 	}
 
+	#[test]
+	fn origin_api_works() {
+		let (code, _) = compile_module("origin").unwrap();
+
+		ExtBuilder::default().existential_deposit(100).build().execute_with(|| {
+			let _ = <Test as Config>::Currency::set_balance(&ALICE, 1_000_000);
+
+			// Create fixture: Constructor does nothing
+			let Contract { addr, .. } =
+				builder::bare_instantiate(Code::Upload(code)).build_and_unwrap_contract();
+
+			// Call the contract: Asserts the origin API to work as expected
+			assert_ok!(builder::call(addr).build());
+		});
+	}
+
 	#[test]
 	fn code_hash_works() {
 		let (code_hash_code, self_code_hash) = compile_module("code_hash").unwrap();

substrate/frame/revive/src/wasm/runtime.rs

@@ -291,6 +291,8 @@ pub enum RuntimeCosts {
 	CopyToContract(u32),
 	/// Weight of calling `seal_caller`.
 	Caller,
+	/// Weight of calling `seal_origin`.
+	Origin,
 	/// Weight of calling `seal_is_contract`.
 	IsContract,
 	/// Weight of calling `seal_code_hash`.
@@ -448,6 +450,7 @@ impl<T: Config> Token<T> for RuntimeCosts {
 			CopyToContract(len) => T::WeightInfo::seal_input(len),
 			CopyFromContract(len) => T::WeightInfo::seal_return(len),
 			Caller => T::WeightInfo::seal_caller(),
+			Origin => T::WeightInfo::seal_origin(),
 			IsContract => T::WeightInfo::seal_is_contract(),
 			CodeHash => T::WeightInfo::seal_code_hash(),
 			OwnCodeHash => T::WeightInfo::seal_own_code_hash(),
@@ -1388,6 +1391,21 @@ pub mod env {
 		)?)
 	}
 
+	/// Stores the address of the call stack origin into the supplied buffer.
+	/// See [`pallet_revive_uapi::HostFn::origin`].
+	#[api_version(0)]
+	fn origin(&mut self, memory: &mut M, out_ptr: u32) -> Result<(), TrapReason> {
+		self.charge_gas(RuntimeCosts::Origin)?;
+		let origin = <E::T as Config>::AddressMapper::to_address(self.ext.origin().account_id()?);
+		Ok(self.write_fixed_sandbox_output(
+			memory,
+			out_ptr,
+			origin.as_bytes(),
+			false,
+			already_charged,
+		)?)
+	}
+
 	/// Checks whether a specified address belongs to a contract.
 	/// See [`pallet_revive_uapi::HostFn::is_contract`].
 	#[api_version(0)]