Add environmental variable to track decoded instructions (#1320)

* Add environmental variable to track decoded instructions

* Fix doc tests

* Fix manifest formatting

* ".git/.scripts/commands/fmt/fmt.sh"

* Add one more test

* Add SetAppendix in test

---------

Co-authored-by: command-bot <>

polkadot/xcm/Cargo.toml

@@ -16,6 +16,7 @@ scale-info = { version = "2.5.0", default-features = false, features = ["derive"
 sp-weights = { path = "../../substrate/primitives/weights", default-features = false, features = ["serde"] }
 serde = { version = "1.0.188", default-features = false, features = ["alloc", "derive"] }
 xcm-procedural = { path = "procedural" }
+environmental = { version = "1.1.4", default-features = false }
 
 [dev-dependencies]
 sp-io = { path = "../../substrate/primitives/io" }
@@ -27,6 +28,7 @@ default = [ "std" ]
 wasm-api = []
 std = [
 	"bounded-collections/std",
+	"environmental/std",
 	"parity-scale-codec/std",
 	"scale-info/std",
 	"serde/std",

polkadot/xcm/src/lib.rs

@@ -20,7 +20,8 @@
 // necessarily related to FRAME or even Substrate.
 //
 // Hence, `no_std` rather than sp-runtime.
-#![no_std]
+#![cfg_attr(not(feature = "std"), no_std)]
+
 extern crate alloc;
 
 use derivative::Derivative;

polkadot/xcm/src/v2/multilocation.rs

@@ -238,7 +238,7 @@ impl MultiLocation {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v2::{Junctions::*, Junction::*, MultiLocation};
+	/// # use staging_xcm::v2::{Junctions::*, Junction::*, MultiLocation};
 	/// # fn main() {
 	/// let mut m = MultiLocation::new(1, X2(PalletInstance(3), OnlyChild));
 	/// assert_eq!(
@@ -260,7 +260,7 @@ impl MultiLocation {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v2::{Junctions::*, Junction::*, MultiLocation};
+	/// # use staging_xcm::v2::{Junctions::*, Junction::*, MultiLocation};
 	/// let m = MultiLocation::new(1, X3(PalletInstance(3), OnlyChild, OnlyChild));
 	/// assert!(m.starts_with(&MultiLocation::new(1, X1(PalletInstance(3)))));
 	/// assert!(!m.starts_with(&MultiLocation::new(1, X1(GeneralIndex(99)))));
@@ -279,7 +279,7 @@ impl MultiLocation {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v2::{Junctions::*, Junction::*, MultiLocation};
+	/// # use staging_xcm::v2::{Junctions::*, Junction::*, MultiLocation};
 	/// # fn main() {
 	/// let mut m = MultiLocation::new(1, X1(Parachain(21)));
 	/// assert_eq!(m.append_with(X1(PalletInstance(3))), Ok(()));
@@ -302,7 +302,7 @@ impl MultiLocation {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v2::{Junctions::*, Junction::*, MultiLocation};
+	/// # use staging_xcm::v2::{Junctions::*, Junction::*, MultiLocation};
 	/// # fn main() {
 	/// let mut m = MultiLocation::new(2, X1(PalletInstance(3)));
 	/// assert_eq!(m.prepend_with(MultiLocation::new(1, X2(Parachain(21), OnlyChild))), Ok(()));
@@ -839,7 +839,7 @@ impl Junctions {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v2::{Junctions::*, Junction::*};
+	/// # use staging_xcm::v2::{Junctions::*, Junction::*};
 	/// # fn main() {
 	/// let mut m = X3(Parachain(2), PalletInstance(3), OnlyChild);
 	/// assert_eq!(m.match_and_split(&X2(Parachain(2), PalletInstance(3))), Some(&OnlyChild));
@@ -857,7 +857,7 @@ impl Junctions {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v2::{Junctions::*, Junction::*};
+	/// # use staging_xcm::v2::{Junctions::*, Junction::*};
 	/// let mut j = X3(Parachain(2), PalletInstance(3), OnlyChild);
 	/// assert!(j.starts_with(&X2(Parachain(2), PalletInstance(3))));
 	/// assert!(j.starts_with(&j));

polkadot/xcm/src/v2/traits.rs

@@ -278,7 +278,7 @@ pub type SendResult = result::Result<(), SendError>;
 ///
 /// # Example
 /// ```rust
-/// # use xcm::v2::prelude::*;
+/// # use staging_xcm::v2::prelude::*;
 /// # use parity_scale_codec::Encode;
 ///
 /// /// A sender that only passes the message through and does nothing.

polkadot/xcm/src/v3/junctions.rs

@@ -437,7 +437,7 @@ impl Junctions {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v3::{Junctions::*, Junction::*, MultiLocation};
+	/// # use staging_xcm::v3::{Junctions::*, Junction::*, MultiLocation};
 	/// # fn main() {
 	/// let mut m = X1(Parachain(21));
 	/// assert_eq!(m.append_with(X1(PalletInstance(3))), Ok(()));
@@ -568,7 +568,7 @@ impl Junctions {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v3::{Junctions::*, Junction::*};
+	/// # use staging_xcm::v3::{Junctions::*, Junction::*};
 	/// # fn main() {
 	/// let mut m = X3(Parachain(2), PalletInstance(3), OnlyChild);
 	/// assert_eq!(m.match_and_split(&X2(Parachain(2), PalletInstance(3))), Some(&OnlyChild));

polkadot/xcm/src/v3/mod.rs

@@ -22,15 +22,16 @@ use super::v2::{
 };
 use crate::DoubleEncoded;
 use alloc::{vec, vec::Vec};
-use bounded_collections::{parameter_types, BoundedVec, ConstU32};
+use bounded_collections::{parameter_types, BoundedVec};
 use core::{
 	convert::{TryFrom, TryInto},
 	fmt::Debug,
 	result,
 };
 use derivative::Derivative;
 use parity_scale_codec::{
-	self, Decode, Encode, Error as CodecError, Input as CodecInput, MaxEncodedLen,
+	self, decode_vec_with_len, Compact, Decode, Encode, Error as CodecError, Input as CodecInput,
+	MaxEncodedLen,
 };
 use scale_info::TypeInfo;
 
@@ -69,13 +70,25 @@ pub type QueryId = u64;
 #[scale_info(bounds(), skip_type_params(Call))]
 pub struct Xcm<Call>(pub Vec<Instruction<Call>>);
 
-const MAX_INSTRUCTIONS_TO_DECODE: u32 = 100;
+const MAX_INSTRUCTIONS_TO_DECODE: u8 = 100;
+
+environmental::environmental!(instructions_count: u8);
 
 impl<Call> Decode for Xcm<Call> {
 	fn decode<I: CodecInput>(input: &mut I) -> core::result::Result<Self, CodecError> {
-		let bounded_instructions =
-			BoundedVec::<Instruction<Call>, ConstU32<MAX_INSTRUCTIONS_TO_DECODE>>::decode(input)?;
-		Ok(Self(bounded_instructions.into_inner()))
+		instructions_count::using_once(&mut 0, || {
+			let number_of_instructions: u32 = <Compact<u32>>::decode(input)?.into();
+			instructions_count::with(|count| {
+				*count = count.saturating_add(number_of_instructions as u8);
+				if *count > MAX_INSTRUCTIONS_TO_DECODE {
+					return Err(CodecError::from("Max instructions exceeded"))
+				}
+				Ok(())
+			})
+			.unwrap_or(Ok(()))?;
+			let decoded_instructions = decode_vec_with_len(input, number_of_instructions as usize)?;
+			Ok(Self(decoded_instructions))
+		})
 	}
 }
 
@@ -1441,15 +1454,31 @@ mod tests {
 	}
 
 	#[test]
-	fn decoding_fails_when_too_many_instructions() {
-		let small_xcm = Xcm::<()>(vec![ClearOrigin; 20]);
-		let bytes = small_xcm.encode();
-		let decoded_xcm = Xcm::<()>::decode(&mut &bytes[..]);
-		assert!(matches!(decoded_xcm, Ok(_)));
-
-		let big_xcm = Xcm::<()>(vec![ClearOrigin; 64_000]);
-		let bytes = big_xcm.encode();
-		let decoded_xcm = Xcm::<()>::decode(&mut &bytes[..]);
-		assert!(matches!(decoded_xcm, Err(CodecError { .. })));
+	fn decoding_respects_limit() {
+		let max_xcm = Xcm::<()>(vec![ClearOrigin; MAX_INSTRUCTIONS_TO_DECODE as usize]);
+		let encoded = max_xcm.encode();
+		assert!(Xcm::<()>::decode(&mut &encoded[..]).is_ok());
+
+		let big_xcm = Xcm::<()>(vec![ClearOrigin; MAX_INSTRUCTIONS_TO_DECODE as usize + 1]);
+		let encoded = big_xcm.encode();
+		assert!(Xcm::<()>::decode(&mut &encoded[..]).is_err());
+
+		let nested_xcm = Xcm::<()>(vec![
+			DepositReserveAsset {
+				assets: All.into(),
+				dest: Here.into(),
+				xcm: max_xcm,
+			};
+			(MAX_INSTRUCTIONS_TO_DECODE / 2) as usize
+		]);
+		let encoded = nested_xcm.encode();
+		assert!(Xcm::<()>::decode(&mut &encoded[..]).is_err());
+
+		let even_more_nested_xcm = Xcm::<()>(vec![SetAppendix(nested_xcm); 64]);
+		let encoded = even_more_nested_xcm.encode();
+		assert_eq!(encoded.len(), 342530);
+		// This should not decode since the limit is 100
+		assert_eq!(MAX_INSTRUCTIONS_TO_DECODE, 100, "precondition");
+		assert!(Xcm::<()>::decode(&mut &encoded[..]).is_err());
 	}
 }

polkadot/xcm/src/v3/multilocation.rs

@@ -265,7 +265,7 @@ impl MultiLocation {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v3::{Junctions::*, Junction::*, MultiLocation};
+	/// # use staging_xcm::v3::{Junctions::*, Junction::*, MultiLocation};
 	/// # fn main() {
 	/// let mut m = MultiLocation::new(1, X2(PalletInstance(3), OnlyChild));
 	/// assert_eq!(
@@ -292,7 +292,7 @@ impl MultiLocation {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v3::{Junctions::*, Junction::*, MultiLocation, Parent};
+	/// # use staging_xcm::v3::{Junctions::*, Junction::*, MultiLocation, Parent};
 	/// # fn main() {
 	/// let mut m: MultiLocation = (Parent, Parachain(21), 69u64).into();
 	/// assert_eq!(m.append_with((Parent, PalletInstance(3))), Ok(()));
@@ -313,7 +313,7 @@ impl MultiLocation {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v3::{Junctions::*, Junction::*, MultiLocation, Parent};
+	/// # use staging_xcm::v3::{Junctions::*, Junction::*, MultiLocation, Parent};
 	/// # fn main() {
 	/// let mut m: MultiLocation = (Parent, Parachain(21), 69u64).into();
 	/// let r = m.appended_with((Parent, PalletInstance(3))).unwrap();
@@ -333,7 +333,7 @@ impl MultiLocation {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v3::{Junctions::*, Junction::*, MultiLocation, Parent};
+	/// # use staging_xcm::v3::{Junctions::*, Junction::*, MultiLocation, Parent};
 	/// # fn main() {
 	/// let mut m: MultiLocation = (Parent, Parent, PalletInstance(3)).into();
 	/// assert_eq!(m.prepend_with((Parent, Parachain(21), OnlyChild)), Ok(()));
@@ -382,7 +382,7 @@ impl MultiLocation {
 	///
 	/// # Example
 	/// ```rust
-	/// # use xcm::v3::{Junctions::*, Junction::*, MultiLocation, Parent};
+	/// # use staging_xcm::v3::{Junctions::*, Junction::*, MultiLocation, Parent};
 	/// # fn main() {
 	/// let m: MultiLocation = (Parent, Parent, PalletInstance(3)).into();
 	/// let r = m.prepended_with((Parent, Parachain(21), OnlyChild)).unwrap();

polkadot/xcm/src/v3/traits.rs

@@ -449,8 +449,8 @@ pub type SendResult<T> = result::Result<(T, MultiAssets), SendError>;
 /// # Example
 /// ```rust
 /// # use parity_scale_codec::Encode;
-/// # use xcm::v3::{prelude::*, Weight};
-/// # use xcm::VersionedXcm;
+/// # use staging_xcm::v3::{prelude::*, Weight};
+/// # use staging_xcm::VersionedXcm;
 /// # use std::convert::Infallible;
 ///
 /// /// A sender that only passes the message through and does nothing.

polkadot/xcm/xcm-builder/src/currency_adapter.rs

@@ -53,7 +53,7 @@ impl From<Error> for XcmError {
 /// use frame_support::{parameter_types, PalletId};
 /// use sp_runtime::traits::{AccountIdConversion, TrailingZeroInput};
 /// use xcm::latest::prelude::*;
-/// use xcm_builder::{ParentIsPreset, CurrencyAdapter, IsConcrete};
+/// use staging_xcm_builder::{ParentIsPreset, CurrencyAdapter, IsConcrete};
 ///
 /// /// Our chain's account id.
 /// type AccountId = sp_runtime::AccountId32;

polkadot/xcm/xcm-builder/src/matcher.rs

@@ -50,7 +50,7 @@ impl<'a, Call> CreateMatcher for &'a mut [Instruction<Call>] {
 /// ```rust
 /// use frame_support::traits::ProcessMessageError;
 /// use xcm::latest::Instruction;
-/// use xcm_builder::{CreateMatcher, MatchXcm};
+/// use staging_xcm_builder::{CreateMatcher, MatchXcm};
 ///
 /// let mut msg = [Instruction::<()>::ClearOrigin];
 /// let res = msg

polkadot/xcm/xcm-builder/src/matches_token.rs

@@ -33,7 +33,7 @@ use xcm_executor::traits::{MatchesFungible, MatchesNonFungible};
 ///
 /// ```
 /// use xcm::latest::{MultiLocation, Parent};
-/// use xcm_builder::IsConcrete;
+/// use staging_xcm_builder::IsConcrete;
 /// use xcm_executor::traits::MatchesFungible;
 ///
 /// frame_support::parameter_types! {
@@ -71,7 +71,7 @@ impl<T: Get<MultiLocation>, I: TryFrom<AssetInstance>> MatchesNonFungible<I> for
 ///
 /// ```
 /// use xcm::latest::prelude::*;
-/// use xcm_builder::IsAbstract;
+/// use staging_xcm_builder::IsAbstract;
 /// use xcm_executor::traits::{MatchesFungible, MatchesNonFungible};
 ///
 /// frame_support::parameter_types! {

polkadot/xcm/xcm-executor/src/assets.rs

@@ -446,7 +446,7 @@ impl Assets {
 	/// Example:
 	///
 	/// ```
-	/// use xcm_executor::Assets;
+	/// use staging_xcm_executor::Assets;
 	/// use xcm::latest::prelude::*;
 	/// let assets_i_have: Assets = vec![ (Here, 100).into(), ([0; 32], 100).into() ].into();
 	/// let assets_they_want: MultiAssetFilter = vec![ (Here, 200).into(), ([0; 32], 50).into() ].into();

polkadot/xcm/xcm-executor/src/traits/conversion.rs

@@ -46,7 +46,7 @@ impl<AccountId> ConvertLocation<AccountId> for Tuple {
 ///
 /// ```rust
 /// # use xcm::latest::{MultiLocation, Junctions, Junction, OriginKind};
-/// # use xcm_executor::traits::ConvertOrigin;
+/// # use staging_xcm_executor::traits::ConvertOrigin;
 /// // A convertor that will bump the para id and pass it to the next one.
 /// struct BumpParaId;
 /// impl ConvertOrigin<u32> for BumpParaId {