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Support multiple key shares per validator (#416)

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* Update the coordinator to give key shares based on weight, not based on existence

Participants are now identified by their starting index. While this compiles,
the following is unimplemented:

1) A conversion for DKG `i` values. It assumes the threshold `i` values used
will be identical for the MuSig signature used to confirm the DKG.
2) Expansion from compressed values to full values before forwarding to the
processor.

* Add a fn to the DkgConfirmer to convert `i` values as needed

Also removes TODOs regarding Serai ensuring validator key uniqueness +
validity. The current infra achieves both.

* Have the Tributary DB track participation by shares, not by count

* Prevent a node from obtaining 34% of the maximum amount of key shares

This is actually mainly intended to set a bound on message sizes in the
coordinator. Message sizes are amplified by the amount of key shares held, so
setting an upper bound on said amount lets it determine constants. While that
upper bound could be 150, that'd be unreasonable and increase the potential for
DoS attacks.

* Correct the mechanism to detect if sufficient accumulation has occured

It used to check if the latest accumulation hit the required threshold. Now,
accumulations may jump past the required threshold. The required mechanism is
to check the threshold wasn't prior met and is now met.

* Finish updating the coordinator to handle a multiple key share per validator environment

* Adjust stategy re: preventing noce reuse in DKG Confirmer

* Add TODOs regarding dropped transactions, add possible TODO fix

* Update tests/coordinator

This doesn't add new multi-key-share tests, it solely updates the existing
single key-share tests to compile and run, with the necessary fixes to the
coordinator.

* Update processor key_gen to handle generating multiple key shares at once

* Update SubstrateSigner

* Update signer, clippy

* Update processor tests

* Update processor docker tests
This commit is contained in:
Luke Parker
2023-11-04 19:26:13 -04:00
committed by GitHub
parent 5970a455d0
commit e05b77d830
28 changed files with 866 additions and 437 deletions
Download Patch File Download Diff File Expand all files Collapse all files

111
processor/src/substrate_signer.rs
View File

@@ -8,6 +8,7 @@ use ciphersuite::group::GroupEncoding;
use frost::{
curve::Ristretto,
ThresholdKeys,
algorithm::Algorithm,
sign::{
Writable, PreprocessMachine, SignMachine, SignatureMachine, AlgorithmMachine,
AlgorithmSignMachine, AlgorithmSignatureMachine,
@@ -77,16 +78,25 @@ impl<D: Db> SubstrateSignerDb<D> {
}
}
type Preprocess = <AlgorithmMachine<Ristretto, Schnorrkel> as PreprocessMachine>::Preprocess;
type SignatureShare = <AlgorithmSignMachine<Ristretto, Schnorrkel> as SignMachine<
<Schnorrkel as Algorithm<Ristretto>>::Signature,
>>::SignatureShare;
pub struct SubstrateSigner<D: Db> {
db: PhantomData<D>,
network: NetworkId,
keys: ThresholdKeys<Ristretto>,
keys: Vec<ThresholdKeys<Ristretto>>,
signable: HashMap<[u8; 32], Batch>,
attempt: HashMap<[u8; 32], u32>,
preprocessing: HashMap<[u8; 32], AlgorithmSignMachine<Ristretto, Schnorrkel>>,
signing: HashMap<[u8; 32], AlgorithmSignatureMachine<Ristretto, Schnorrkel>>,
#[allow(clippy::type_complexity)]
preprocessing:
HashMap<[u8; 32], (Vec<AlgorithmSignMachine<Ristretto, Schnorrkel>>, Vec<Preprocess>)>,
#[allow(clippy::type_complexity)]
signing:
HashMap<[u8; 32], (AlgorithmSignatureMachine<Ristretto, Schnorrkel>, Vec<SignatureShare>)>,
pub events: VecDeque<SubstrateSignerEvent>,
}
@@ -102,7 +112,8 @@ impl<D: Db> fmt::Debug for SubstrateSigner<D> {
}
impl<D: Db> SubstrateSigner<D> {
pub fn new(network: NetworkId, keys: ThresholdKeys<Ristretto>) -> SubstrateSigner<D> {
pub fn new(network: NetworkId, keys: Vec<ThresholdKeys<Ristretto>>) -> SubstrateSigner<D> {
assert!(!keys.is_empty());
SubstrateSigner {
db: PhantomData,
@@ -178,7 +189,7 @@ impl<D: Db> SubstrateSigner<D> {
// Update the attempt number
self.attempt.insert(id, attempt);
let id = SignId { key: self.keys.group_key().to_bytes().to_vec(), id, attempt };
let id = SignId { key: self.keys[0].group_key().to_bytes().to_vec(), id, attempt };
info!("signing batch {} #{}", hex::encode(id.id), id.attempt);
// If we reboot mid-sign, the current design has us abort all signs and wait for latter
@@ -204,19 +215,27 @@ impl<D: Db> SubstrateSigner<D> {
SubstrateSignerDb::<D>::attempt(txn, &id);
// b"substrate" is a literal from sp-core
let machine = AlgorithmMachine::new(Schnorrkel::new(b"substrate"), self.keys.clone());
let mut machines = vec![];
let mut preprocesses = vec![];
let mut serialized_preprocesses = vec![];
for keys in &self.keys {
// b"substrate" is a literal from sp-core
let machine = AlgorithmMachine::new(Schnorrkel::new(b"substrate"), keys.clone());
// TODO: Use a seeded RNG here so we don't produce distinct messages with the same intent
// This is also needed so we don't preprocess, send preprocess, reboot before ack'ing the
// message, send distinct preprocess, and then attempt a signing session premised on the former
// with the latter
let (machine, preprocess) = machine.preprocess(&mut OsRng);
self.preprocessing.insert(id.id, machine);
// TODO: Use a seeded RNG here so we don't produce distinct messages with the same intent
// This is also needed so we don't preprocess, send preprocess, reboot before ack'ing the
// message, send distinct preprocess, and then attempt a signing session premised on the
// former with the latter
let (machine, preprocess) = machine.preprocess(&mut OsRng);
machines.push(machine);
serialized_preprocesses.push(preprocess.serialize());
preprocesses.push(preprocess);
}
self.preprocessing.insert(id.id, (machines, preprocesses));
// Broadcast our preprocess
// Broadcast our preprocesses
self.events.push_back(SubstrateSignerEvent::ProcessorMessage(
ProcessorMessage::BatchPreprocess { id, block, preprocess: preprocess.serialize() },
ProcessorMessage::BatchPreprocess { id, block, preprocesses: serialized_preprocesses },
));
}
@@ -240,23 +259,23 @@ impl<D: Db> SubstrateSigner<D> {
return;
}
let machine = match self.preprocessing.remove(&id.id) {
let (machines, our_preprocesses) = match self.preprocessing.remove(&id.id) {
// Either rebooted or RPC error, or some invariant
None => {
warn!(
"not preprocessing for {}. this is an error if we didn't reboot",
hex::encode(id.id)
hex::encode(id.id),
);
return;
}
Some(machine) => machine,
Some(preprocess) => preprocess,
};
let preprocesses = match preprocesses
.drain()
.map(|(l, preprocess)| {
let mut preprocess_ref = preprocess.as_ref();
let res = machine
let res = machines[0]
.read_preprocess::<&[u8]>(&mut preprocess_ref)
.map(|preprocess| (l, preprocess));
if !preprocess_ref.is_empty() {
@@ -264,24 +283,44 @@ impl<D: Db> SubstrateSigner<D> {
}
res
})
.collect::<Result<_, _>>()
.collect::<Result<HashMap<_, _>, _>>()
{
Ok(preprocesses) => preprocesses,
Err(e) => todo!("malicious signer: {:?}", e),
};
let (machine, share) =
match machine.sign(preprocesses, &batch_message(&self.signable[&id.id])) {
Ok(res) => res,
Err(e) => todo!("malicious signer: {:?}", e),
};
self.signing.insert(id.id, machine);
// Only keep a single machine as we only need one to get the signature
let mut signature_machine = None;
let mut shares = vec![];
let mut serialized_shares = vec![];
for (m, machine) in machines.into_iter().enumerate() {
let mut preprocesses = preprocesses.clone();
for (i, our_preprocess) in our_preprocesses.clone().into_iter().enumerate() {
if i != m {
assert!(preprocesses.insert(self.keys[i].params().i(), our_preprocess).is_none());
}
}
// Broadcast our share
let mut share_bytes = [0; 32];
share_bytes.copy_from_slice(&share.serialize());
let (machine, share) =
match machine.sign(preprocesses, &batch_message(&self.signable[&id.id])) {
Ok(res) => res,
Err(e) => todo!("malicious signer: {:?}", e),
};
if m == 0 {
signature_machine = Some(machine);
}
let mut share_bytes = [0; 32];
share_bytes.copy_from_slice(&share.serialize());
serialized_shares.push(share_bytes);
shares.push(share);
}
self.signing.insert(id.id, (signature_machine.unwrap(), shares));
// Broadcast our shares
self.events.push_back(SubstrateSignerEvent::ProcessorMessage(
ProcessorMessage::BatchShare { id, share: share_bytes },
ProcessorMessage::BatchShare { id, shares: serialized_shares },
));
}
@@ -290,7 +329,7 @@ impl<D: Db> SubstrateSigner<D> {
return;
}
let machine = match self.signing.remove(&id.id) {
let (machine, our_shares) = match self.signing.remove(&id.id) {
// Rebooted, RPC error, or some invariant
None => {
// If preprocessing has this ID, it means we were never sent the preprocess by the
@@ -305,10 +344,10 @@ impl<D: Db> SubstrateSigner<D> {
);
return;
}
Some(machine) => machine,
Some(signing) => signing,
};
let shares = match shares
let mut shares = match shares
.drain()
.map(|(l, share)| {
let mut share_ref = share.as_ref();
@@ -318,12 +357,16 @@ impl<D: Db> SubstrateSigner<D> {
}
res
})
.collect::<Result<_, _>>()
.collect::<Result<HashMap<_, _>, _>>()
{
Ok(shares) => shares,
Err(e) => todo!("malicious signer: {:?}", e),
};
for (i, our_share) in our_shares.into_iter().enumerate().skip(1) {
assert!(shares.insert(self.keys[i].params().i(), our_share).is_none());
}
let sig = match machine.complete(shares) {
Ok(res) => res,
Err(e) => todo!("malicious signer: {:?}", e),