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pallet-treasury: Ensure we respect max_amount for spend across ba…
…tch calls (paritytech#13468) * `pallet-treasury`: Ensure we respect `max_amount` for spend across batch calls When calling `spend` the origin defines the `max_amount` of tokens it is allowed to spend. The problem is that someone can send a `batch(spend, spend)` to circumvent this restriction as we don't check across different calls that the `max_amount` is respected. This pull request fixes this behavior by introducing a so-called dispatch context. This dispatch context is created once per outer most `dispatch` call. For more information see the docs in this pr. The treasury then uses this dispatch context to attach information about already spent funds per `max_amount` (we assume that each origin has a different `max_amount` configured). So, a `batch(spend, spend)` is now checked to stay inside the allowed spending bounds. Fixes: paritytech#13167 * Import `Box` for wasm * FMT
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| // This file is part of Substrate. | ||
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| // Copyright (C) Parity Technologies (UK) Ltd. | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
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| // 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. | ||
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| //! Provides functions to interact with the dispatch context. | ||
| //! | ||
| //! A Dispatch context is created by calling [`run_in_context`] and then the given closure will be | ||
| //! executed in this dispatch context. Everyting run in this `closure` will have access to the same | ||
| //! dispatch context. This also applies to nested calls of [`run_in_context`]. The dispatch context | ||
| //! can be used to store and retrieve information locally in this context. The dispatch context can | ||
| //! be accessed by using [`with_context`]. This function will execute the given closure and give it | ||
| //! access to the value stored in the dispatch context. | ||
| //! | ||
| //! # FRAME integration | ||
| //! | ||
| //! The FRAME macros implement [`UnfilteredDispatchable`](crate::traits::UnfilteredDispatchable) for | ||
| //! each pallet `Call` enum. Part of this implementation is the call to [`run_in_context`], so that | ||
| //! each call to | ||
| //! [`UnfilteredDispatchable::dispatch_bypass_filter`](crate::traits::UnfilteredDispatchable::dispatch_bypass_filter) | ||
| //! or [`Dispatchable::dispatch`](crate::dispatch::Dispatchable::dispatch) will run in a dispatch | ||
| //! context. | ||
| //! | ||
| //! # Example | ||
| //! | ||
| //! ``` | ||
| //! use frame_support::dispatch_context::{with_context, run_in_context}; | ||
| //! | ||
| //! // Not executed in a dispatch context, so it should return `None`. | ||
| //! assert!(with_context::<(), _>(|_| println!("Hello")).is_none()); | ||
| //! | ||
| //! // Run it in a dispatch context and `with_context` returns `Some(_)`. | ||
| //! run_in_context(|| { | ||
| //! assert!(with_context::<(), _>(|_| println!("Hello")).is_some()); | ||
| //! }); | ||
| //! | ||
| //! #[derive(Default)] | ||
| //! struct CustomContext(i32); | ||
| //! | ||
| //! run_in_context(|| { | ||
| //! with_context::<CustomContext, _>(|v| { | ||
| //! // Intitialize the value to the default value. | ||
| //! assert_eq!(0, v.or_default().0); | ||
| //! v.or_default().0 = 10; | ||
| //! }); | ||
| //! | ||
| //! with_context::<CustomContext, _>(|v| { | ||
| //! // We are still in the same context and can still access the set value. | ||
| //! assert_eq!(10, v.or_default().0); | ||
| //! }); | ||
| //! | ||
| //! run_in_context(|| { | ||
| //! with_context::<CustomContext, _>(|v| { | ||
| //! // A nested call of `run_in_context` stays in the same dispatch context | ||
| //! assert_eq!(10, v.or_default().0); | ||
| //! }) | ||
| //! }) | ||
| //! }); | ||
| //! | ||
| //! run_in_context(|| { | ||
| //! with_context::<CustomContext, _>(|v| { | ||
| //! // We left the other context and created a new one, so we should be back | ||
| //! // to our default value. | ||
| //! assert_eq!(0, v.or_default().0); | ||
| //! }); | ||
| //! }); | ||
| //! ``` | ||
| //! | ||
| //! In your pallet you will only have to use [`with_context`], because as described above | ||
| //! [`run_in_context`] will be handled by FRAME for you. | ||
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| use sp_std::{ | ||
| any::{Any, TypeId}, | ||
| boxed::Box, | ||
| collections::btree_map::{BTreeMap, Entry}, | ||
| }; | ||
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| environmental::environmental!(DISPATCH_CONTEXT: BTreeMap<TypeId, Box<dyn Any>>); | ||
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| /// Abstraction over some optional value `T` that is stored in the dispatch context. | ||
| pub struct Value<'a, T> { | ||
| value: Option<&'a mut T>, | ||
| new_value: Option<T>, | ||
| } | ||
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| impl<T> Value<'_, T> { | ||
| /// Get the value as reference. | ||
| pub fn get(&self) -> Option<&T> { | ||
| self.new_value.as_ref().or_else(|| self.value.as_ref().map(|v| *v as &T)) | ||
| } | ||
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| /// Get the value as mutable reference. | ||
| pub fn get_mut(&mut self) -> Option<&mut T> { | ||
| self.new_value.as_mut().or_else(|| self.value.as_mut().map(|v| *v as &mut T)) | ||
| } | ||
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| /// Set to the given value. | ||
| /// | ||
| /// [`Self::get`] and [`Self::get_mut`] will return `new_value` afterwards. | ||
| pub fn set(&mut self, new_value: T) { | ||
| self.value = None; | ||
| self.new_value = Some(new_value); | ||
| } | ||
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| /// Returns a mutable reference to the value. | ||
| /// | ||
| /// If the internal value isn't initialized, this will set it to [`Default::default()`] before | ||
| /// returning the mutable reference. | ||
| pub fn or_default(&mut self) -> &mut T | ||
| where | ||
| T: Default, | ||
| { | ||
| if let Some(v) = &mut self.value { | ||
| return v | ||
| } | ||
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| self.new_value.get_or_insert_with(|| Default::default()) | ||
| } | ||
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| /// Clear the internal value. | ||
| /// | ||
| /// [`Self::get`] and [`Self::get_mut`] will return `None` afterwards. | ||
| pub fn clear(&mut self) { | ||
| self.new_value = None; | ||
| self.value = None; | ||
| } | ||
| } | ||
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| /// Runs the given `callback` in the dispatch context and gives access to some user defined value. | ||
| /// | ||
| /// Passes the a mutable reference of [`Value`] to the callback. The value will be of type `T` and | ||
| /// is identified using the [`TypeId`] of `T`. This means that `T` should be some unique type to | ||
| /// make the value unique. If no value is set yet [`Value::get()`] and [`Value::get_mut()`] will | ||
| /// return `None`. It is totally valid to have some `T` that is shared between different callers to | ||
| /// have access to the same value. | ||
| /// | ||
| /// Returns `None` if the current context is not a dispatch context. To create a context it is | ||
| /// required to call [`run_in_context`] with the closure to execute in this context. So, for example | ||
| /// in tests it could be that there isn't any dispatch context or when calling a dispatchable like a | ||
| /// normal Rust function from some FRAME hook. | ||
| pub fn with_context<T: 'static, R>(callback: impl FnOnce(&mut Value<T>) -> R) -> Option<R> { | ||
| DISPATCH_CONTEXT::with(|c| match c.entry(TypeId::of::<T>()) { | ||
| Entry::Occupied(mut o) => { | ||
| let value = o.get_mut().downcast_mut::<T>(); | ||
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| if value.is_none() { | ||
| log::error!( | ||
| "Failed to downcast value for type {} in dispatch context!", | ||
| sp_std::any::type_name::<T>(), | ||
| ); | ||
| } | ||
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| let mut value = Value { value, new_value: None }; | ||
| let res = callback(&mut value); | ||
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| if value.value.is_none() && value.new_value.is_none() { | ||
| o.remove(); | ||
| } else if let Some(new_value) = value.new_value { | ||
| o.insert(Box::new(new_value) as Box<_>); | ||
| } | ||
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| res | ||
| }, | ||
| Entry::Vacant(v) => { | ||
| let mut value = Value { value: None, new_value: None }; | ||
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| let res = callback(&mut value); | ||
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| if let Some(new_value) = value.new_value { | ||
| v.insert(Box::new(new_value) as Box<_>); | ||
| } | ||
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| res | ||
| }, | ||
| }) | ||
| } | ||
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| /// Run the given closure `run` in a dispatch context. | ||
| /// | ||
| /// Nested calls to this function will execute `run` in the same dispatch context as the initial | ||
| /// call to this function. In other words, all nested calls of this function will be done in the | ||
| /// same dispatch context. | ||
| pub fn run_in_context<R>(run: impl FnOnce() -> R) -> R { | ||
| DISPATCH_CONTEXT::using_once(&mut Default::default(), run) | ||
| } | ||
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| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
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| #[test] | ||
| fn dispatch_context_works() { | ||
| // No context, so we don't execute | ||
| assert!(with_context::<(), _>(|_| ()).is_none()); | ||
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| let ret = run_in_context(|| with_context::<(), _>(|_| 1).unwrap()); | ||
| assert_eq!(1, ret); | ||
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| #[derive(Default)] | ||
| struct Context(i32); | ||
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| let res = run_in_context(|| { | ||
| with_context::<Context, _>(|v| { | ||
| assert_eq!(0, v.or_default().0); | ||
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| v.or_default().0 = 100; | ||
| }); | ||
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| run_in_context(|| { | ||
| run_in_context(|| { | ||
| run_in_context(|| with_context::<Context, _>(|v| v.or_default().0).unwrap()) | ||
| }) | ||
| }) | ||
| }); | ||
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| // Ensure that the initial value set in the context is also accessible after nesting the | ||
| // `run_in_context` calls. | ||
| assert_eq!(100, res); | ||
| } | ||
| } |
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