contracts: Allow indeterministic instructions off-chain (#12469)

* Allow indetermistic instructions off-chain

* Apply suggestions from code review

Co-authored-by: Sasha Gryaznov <hi@agryaznov.com>

* fmt

Co-authored-by: Sasha Gryaznov <hi@agryaznov.com>

substrate/frame/contracts/src/wasm/mod.rs

@@ -37,6 +37,7 @@ use crate::{
 use codec::{Decode, Encode, MaxEncodedLen};
 use frame_support::dispatch::{DispatchError, DispatchResult};
 use sp_core::crypto::UncheckedFrom;
+use sp_runtime::RuntimeDebug;
 use sp_sandbox::{SandboxEnvironmentBuilder, SandboxInstance, SandboxMemory};
 use sp_std::prelude::*;
 #[cfg(test)]
@@ -66,6 +67,10 @@ pub struct PrefabWasmModule<T: Config> {
 	maximum: u32,
 	/// Code instrumented with the latest schedule.
 	code: RelaxedCodeVec<T>,
+	/// A code that might contain non deterministic features and is therefore never allowed
+	/// to be run on chain. Specifically this code can never be instantiated into a contract
+	/// and can just be used through a delegate call.
+	determinism: Determinism,
 	/// The uninstrumented, pristine version of the code.
 	///
 	/// It is not stored because the pristine code has its own storage item. The value
@@ -102,6 +107,27 @@ pub struct OwnerInfo<T: Config> {
 	refcount: u64,
 }
 
+/// Defines the required determinism level of a wasm blob when either running or uploading code.
+#[derive(
+	Clone, Copy, Encode, Decode, scale_info::TypeInfo, MaxEncodedLen, RuntimeDebug, PartialEq, Eq,
+)]
+pub enum Determinism {
+	/// The execution should be deterministic and hence no indeterministic instructions are
+	/// allowed.
+	///
+	/// Dispatchables always use this mode in order to make on-chain execution deterministic.
+	Deterministic,
+	/// Allow calling or uploading an indeterministic code.
+	///
+	/// This is only possible when calling into `pallet-contracts` directly via
+	/// [`crate::Pallet::bare_call`].
+	///
+	/// # Note
+	///
+	/// **Never** use this mode for on-chain execution.
+	AllowIndeterminism,
+}
+
 impl ExportedFunction {
 	/// The wasm export name for the function.
 	fn identifier(&self) -> &str {
@@ -124,11 +150,13 @@ where
 		original_code: Vec<u8>,
 		schedule: &Schedule<T>,
 		owner: AccountIdOf<T>,
+		determinism: Determinism,
 	) -> Result<Self, (DispatchError, &'static str)> {
 		let module = prepare::prepare_contract(
 			original_code.try_into().map_err(|_| (<Error<T>>::CodeTooLarge.into(), ""))?,
 			schedule,
 			owner,
+			determinism,
 		)?;
 		Ok(module)
 	}
@@ -258,6 +286,10 @@ where
 	fn code_len(&self) -> u32 {
 		self.code.len() as u32
 	}
+
+	fn is_deterministic(&self) -> bool {
+		matches!(self.determinism, Determinism::Deterministic)
+	}
 }
 
 #[cfg(test)]
@@ -551,8 +583,13 @@ mod tests {
 	fn execute<E: BorrowMut<MockExt>>(wat: &str, input_data: Vec<u8>, mut ext: E) -> ExecResult {
 		let wasm = wat::parse_str(wat).unwrap();
 		let schedule = crate::Schedule::default();
-		let executable =
-			PrefabWasmModule::<<MockExt as Ext>::T>::from_code(wasm, &schedule, ALICE).unwrap();
+		let executable = PrefabWasmModule::<<MockExt as Ext>::T>::from_code(
+			wasm,
+			&schedule,
+			ALICE,
+			Determinism::Deterministic,
+		)
+		.unwrap();
 		executable.execute(ext.borrow_mut(), &ExportedFunction::Call, input_data)
 	}