Get rid of the unsafe get_mut function in the rust cdk

levi · September 15, 2021, 5:09pm

Roman mentions this in the community-conversation, this is an unsafe api, two get_mut calls within the same public-method can corrupt the memory.

thread_local! With the Cell and RefCell is the way to go.

paulyoung · September 16, 2021, 12:04am

There are several examples that are using the unsafe approach. The cycles wallet too.

paulyoung · September 16, 2021, 12:08am

FYI @roman-kashitsyn

paulyoung · January 17, 2022, 7:12am

I couldn’t find the video but I did find this blog post:

https://mmapped.blog/posts/01-effective-rust-canisters.html

rckprtr · January 18, 2022, 8:06pm

https://www.dfinitycommunity.com/infinityswap-the-is20-token-standard-tested-and-interoperable/#iccdk-storage-bug-fix

IS20 fixes two other vulnerabilities found in prior implementations of token standards. There is a bug in the commonly used ic_cdk storage that can lead to memory corruption through dangling references. Please see the appendix for more details.

Linked bug: Heap corruption in storage · Issue #73 · dfinity/cdk-rs · GitHub

Infinity Swap Impl: canister-sdk/ic-storage/ic-storage-derive/src/lib.rs at main · bitfinity-network/canister-sdk · GitHub

thread_local! {
    static store: Rc<RefCell<#ident>> = Rc::new(RefCell::new(#ident::default()));
}

rckprtr · January 18, 2022, 8:08pm

Example usage in their IS20 token:

github.com

infinity-swap/IS20/blob/main/src/token/src/state.rs

use crate::ledger::Ledger;
use crate::types::{Allowances, AuctionInfo, PendingNotifications, StatsData, Timestamp};
use candid::{CandidType, Deserialize, Nat, Principal};
use ic_storage::IcStorage;
use std::collections::HashMap;

#[derive(Default, CandidType, Deserialize, IcStorage)]
pub struct State {
    stats: StatsData,
    allowances: Allowances,
    ledger: Ledger,
    auction_history: AuctionHistory,
    pub notifications: PendingNotifications,
}

#[derive(Default, IcStorage, CandidType, Deserialize)]
pub struct Balances(pub HashMap<Principal, Nat>);

impl Balances {
    pub fn balance_of(&self, who: &Principal) -> Nat {

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Get rid of the unsafe get_mut function in the rust cdk

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