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Implement deterministic nonces for Tributary transactions
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use core::marker::PhantomData; | ||
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use serai_db::{Get, DbTxn, Db}; | ||
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use crate::tributary::Transaction; | ||
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/// Decides the nonce which should be used for a transaction on a Tributary. | ||
/// | ||
/// Deterministically builds a list of nonces to use based on the on-chain events and expected | ||
/// transactions in response. Enables rebooting/rebuilding validators with full safety. | ||
pub struct NonceDecider<D: Db>(PhantomData<D>); | ||
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const BATCH_CODE: u8 = 0; | ||
const BATCH_SIGNING_CODE: u8 = 1; | ||
const PLAN_CODE: u8 = 2; | ||
const PLAN_SIGNING_CODE: u8 = 3; | ||
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impl<D: Db> NonceDecider<D> { | ||
fn next_nonce_key(genesis: [u8; 32]) -> Vec<u8> { | ||
D::key(b"coordinator_tributary_nonce", b"next", genesis) | ||
} | ||
fn allocate_nonce(txn: &mut D::Transaction<'_>, genesis: [u8; 32]) -> u32 { | ||
let key = Self::next_nonce_key(genesis); | ||
let next = | ||
txn.get(&key).map(|bytes| u32::from_le_bytes(bytes.try_into().unwrap())).unwrap_or(3); | ||
txn.put(key, (next + 1).to_le_bytes()); | ||
next | ||
} | ||
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fn item_nonce_key(genesis: [u8; 32], code: u8, id: [u8; 32]) -> Vec<u8> { | ||
D::key( | ||
b"coordinator_tributary_nonce", | ||
b"item", | ||
[genesis.as_slice(), [code].as_ref(), id.as_ref()].concat(), | ||
) | ||
} | ||
fn set_nonce( | ||
txn: &mut D::Transaction<'_>, | ||
genesis: [u8; 32], | ||
code: u8, | ||
id: [u8; 32], | ||
nonce: u32, | ||
) { | ||
txn.put(Self::item_nonce_key(genesis, code, id), nonce.to_le_bytes()) | ||
} | ||
fn db_nonce<G: Get>(getter: &G, genesis: [u8; 32], code: u8, id: [u8; 32]) -> Option<u32> { | ||
getter | ||
.get(Self::item_nonce_key(genesis, code, id)) | ||
.map(|bytes| u32::from_le_bytes(bytes.try_into().unwrap())) | ||
} | ||
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pub fn handle_batch(txn: &mut D::Transaction<'_>, genesis: [u8; 32], batch: [u8; 32]) -> u32 { | ||
let nonce_for = Self::allocate_nonce(txn, genesis); | ||
Self::set_nonce(txn, genesis, BATCH_CODE, batch, nonce_for); | ||
nonce_for | ||
} | ||
pub fn selected_for_signing_batch( | ||
txn: &mut D::Transaction<'_>, | ||
genesis: [u8; 32], | ||
batch: [u8; 32], | ||
) { | ||
let nonce_for = Self::allocate_nonce(txn, genesis); | ||
Self::set_nonce(txn, genesis, BATCH_SIGNING_CODE, batch, nonce_for); | ||
} | ||
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pub fn handle_substrate_block( | ||
txn: &mut D::Transaction<'_>, | ||
genesis: [u8; 32], | ||
plans: &[[u8; 32]], | ||
) -> Vec<u32> { | ||
let mut res = Vec::with_capacity(plans.len()); | ||
for plan in plans { | ||
let nonce_for = Self::allocate_nonce(txn, genesis); | ||
Self::set_nonce(txn, genesis, PLAN_CODE, *plan, nonce_for); | ||
res.push(nonce_for); | ||
} | ||
res | ||
} | ||
pub fn selected_for_signing_plan( | ||
txn: &mut D::Transaction<'_>, | ||
genesis: [u8; 32], | ||
plan: [u8; 32], | ||
) { | ||
let nonce_for = Self::allocate_nonce(txn, genesis); | ||
Self::set_nonce(txn, genesis, PLAN_SIGNING_CODE, plan, nonce_for); | ||
} | ||
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pub fn nonce<G: Get>(getter: &G, genesis: [u8; 32], tx: &Transaction) -> Option<Option<u32>> { | ||
match tx { | ||
Transaction::DkgCommitments(attempt, _, _) => { | ||
assert_eq!(*attempt, 0); | ||
Some(Some(0)) | ||
} | ||
Transaction::DkgShares { attempt, .. } => { | ||
assert_eq!(*attempt, 0); | ||
Some(Some(1)) | ||
} | ||
Transaction::DkgConfirmed(attempt, _, _) => { | ||
assert_eq!(*attempt, 0); | ||
Some(Some(2)) | ||
} | ||
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Transaction::Batch(_, _) => None, | ||
Transaction::SubstrateBlock(_) => None, | ||
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Transaction::BatchPreprocess(data) => { | ||
assert_eq!(data.attempt, 0); | ||
Some(Self::db_nonce(getter, genesis, BATCH_CODE, data.plan)) | ||
} | ||
Transaction::BatchShare(data) => { | ||
assert_eq!(data.attempt, 0); | ||
Some(Self::db_nonce(getter, genesis, BATCH_SIGNING_CODE, data.plan)) | ||
} | ||
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Transaction::SignPreprocess(data) => { | ||
assert_eq!(data.attempt, 0); | ||
Some(Self::db_nonce(getter, genesis, PLAN_CODE, data.plan)) | ||
} | ||
Transaction::SignShare(data) => { | ||
assert_eq!(data.attempt, 0); | ||
Some(Self::db_nonce(getter, genesis, PLAN_SIGNING_CODE, data.plan)) | ||
} | ||
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Transaction::SignCompleted { .. } => None, | ||
} | ||
} | ||
} |
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