penumbra_sdk_dex/component/action_handler/position/
withdraw.rs

1use anyhow::Result;
2use ark_ff::Zero;
3use async_trait::async_trait;
4use cnidarium::StateWrite;
5use cnidarium_component::ActionHandler;
6use decaf377::Fr;
7
8use crate::{component::PositionManager, lp::action::PositionWithdraw};
9
10#[async_trait]
11/// Debits a closed position NFT and credits a withdrawn position NFT and the final reserves.
12impl ActionHandler for PositionWithdraw {
13    type CheckStatelessContext = ();
14    async fn check_stateless(&self, _context: ()) -> Result<()> {
15        // Nothing to do: the only validation is of the state change,
16        // and that's done by the value balance mechanism.
17        Ok(())
18    }
19
20    async fn check_and_execute<S: StateWrite>(&self, mut state: S) -> Result<()> {
21        // See comment in check_stateful for why we check the position state here:
22        // we need to ensure that we're checking the reserves at the moment we execute
23        // the withdrawal, to prevent any possibility of TOCTOU attacks.
24
25        // Execute the withdrawal, extracting the reserves from the position.
26        let actual_reserves = state
27            .withdraw_position(self.position_id, self.sequence)
28            .await?;
29
30        // Next, and CRITICALLY, check that the commitment to the amount the user is
31        // withdrawing is correct.
32        //
33        // Unlike other actions, where a balance commitment is used for
34        // shielding a value, this commitment is used for compression, giving a
35        // single commitment rather than a list of token amounts.
36        //
37        // Note: since this is forming a commitment only to the reserves,
38        // we are implicitly setting the reward amount to 0. However, we can
39        // add support for rewards in the future without client changes.
40        let expected_reserves_commitment = actual_reserves.commit(Fr::zero());
41
42        if self.reserves_commitment != expected_reserves_commitment {
43            anyhow::bail!(
44                "reserves commitment {:?} is incorrect, expected {:?}",
45                self.reserves_commitment,
46                expected_reserves_commitment
47            );
48        }
49
50        Ok(())
51    }
52}
penumbra_sdk_dex/component/action_handler/position/withdraw.rs

penumbra_sdk_dex/component/action_handler/position/
withdraw.rs
