Skip to content

Commit

Permalink
fix(abba): fix consensus failure by adding check for justification in…
Browse files Browse the repository at this point in the history 
… pre-vote messages
  • Loading branch information
@b00f
b00f committed Jan 18, 2023
1 parent 561c06c commit de476d3
Show file tree
Hide file tree
Showing 5 changed files with 309 additions and 72 deletions.
6 changes: 3 additions & 3 deletions src/mvba/abba/message.rs
View file
Expand Up @@ -27,12 +27,12 @@ impl MainVoteValue {

#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq)]
pub enum PreVoteJustification {
// Round one, without the justification. The initial value should set to zero
// Round one without the justification. The initial value should set to zero
FirstRoundZero,
// Round one, with the justification. The initial value should set to one
// with the weak validity. The initial value should set to one
// The justification is a `c-final` signature of the VCBC protocol for this tuple:
// `(id, proposer, 0, "c-ready", digest)`
FirstRoundOne(Hash32, Signature),
WithValidity(Hash32, Signature),
// In Round r > 1, justification is either hard,...
Hard(Signature),
// ... or soft (refer to the spec)
Expand Down
55 changes: 43 additions & 12 deletions src/mvba/abba/mod.rs
View file
Expand Up @@ -29,6 +29,7 @@ pub(crate) struct Abba {
j: NodeId, // this is same as $j$ in spec
r: usize, // this is same as $r$ in spec
voted: bool,
weak_validity: Option<(Hash32, Signature)>,
decided_value: Option<DecisionAction>,
pub_key_set: PublicKeySet,
sec_key_share: SecretKeyShare,
Expand All @@ -52,6 +53,7 @@ impl Abba {
j: proposer,
r: 1,
voted: false,
weak_validity: None,
decided_value: None,
pub_key_set,
sec_key_share,
Expand All @@ -69,7 +71,7 @@ impl Abba {

/// pre_vote_one starts the abba by broadcasting a pre-vote message with value 1.
pub fn pre_vote_one(&mut self, digest: Hash32, sig: Signature) -> Result<()> {
let justification = PreVoteJustification::FirstRoundOne(digest, sig);
let justification = PreVoteJustification::WithValidity(digest, sig);
self.pre_vote(Value::One, justification)
}

Expand Down Expand Up @@ -155,6 +157,12 @@ impl Abba {
if main_votes.len() >= self.threshold() {
// If these are all main-votes for b ∈ {0, 1}, then decide the value b for ID
if zero_votes.clone().count() >= self.threshold() {
log::info!(
"decided for zero. id={}, r={}, j={}",
self.id,
self.j,
self.r
);
let sig_share: HashMap<&NodeId, &SignatureShare> =
zero_votes.map(|(n, a)| (n, &a.sig_share)).collect();
let sig = self.pub_key_set.combine_signatures(sig_share)?;
Expand All @@ -169,6 +177,12 @@ impl Abba {
}

if one_votes.clone().count() >= self.threshold() {
log::info!(
"decided for one. id={}, r={}, j={}",
self.id,
self.j,
self.r
);
let sig_share: HashMap<&NodeId, &SignatureShare> =
one_votes.map(|(n, a)| (n, &a.sig_share)).collect();
let sig = self.pub_key_set.combine_signatures(sig_share)?;
Expand All @@ -183,7 +197,16 @@ impl Abba {
}

let (value, justification) =
if let Some((_, zero_vote)) = zero_votes.next() {
if let Some((digest, sig)) = &self.weak_validity {
// if all honest parties start with 0, they may still
// decide on 1 if they obtain the corresponding validating data
// for 1 during the agreement protocol

(
Value::One,
PreVoteJustification::WithValidity(*digest, sig.clone()),
)
} else if let Some((_, zero_vote)) = zero_votes.next() {
// if there is a main-vote for 0,
let sig =
match &zero_vote.justification {
Expand Down Expand Up @@ -242,6 +265,10 @@ impl Abba {
return Ok(());
}

if let PreVoteJustification::WithValidity(digest, sig) = &action.justification {
self.weak_validity = Some((*digest, sig.clone()));
};

// 2. MAIN-VOTE. Collect n − t valid and properly justified round-r pre-vote messages.
let pre_votes = match self.get_pre_votes_by_round(self.r) {
Some(v) => v,
Expand Down Expand Up @@ -358,7 +385,7 @@ impl Abba {
Ok(true)
}

fn check_message(&mut self, initiator: &NodeId, msg: &Message) -> Result<()> {
fn check_message(&self, initiator: &NodeId, msg: &Message) -> Result<()> {
if msg.id != self.id {
return Err(Error::InvalidMessage(format!(
"invalid ID. expected: {}, got {}",
Expand Down Expand Up @@ -400,14 +427,7 @@ impl Abba {
));
}
}
PreVoteJustification::FirstRoundOne(digest, sig) => {
if action.round != 1 {
return Err(Error::InvalidMessage(format!(
"invalid round. expected 1, got {}",
action.round
)));
}

PreVoteJustification::WithValidity(digest, sig) => {
let sign_bytes =
crate::mvba::vcbc::c_ready_bytes_to_sign(&self.id, &self.j, digest)?;

Expand Down Expand Up @@ -486,6 +506,15 @@ impl Abba {
}
match just_0.as_ref() {
PreVoteJustification::FirstRoundZero => {}
PreVoteJustification::Hard(sig) => {
let sign_bytes =
self.pre_vote_bytes_to_sign(action.round - 1, &Value::Zero)?;
if !self.pub_key_set.public_key().verify(sig, sign_bytes) {
return Err(Error::InvalidMessage(
"invalid abstain justification for value zero".to_string(),
));
}
}
_ => {
return Err(Error::InvalidMessage(format!(
"invalid justification for value 0 in round 1: {just_0:?}"
Expand All @@ -494,7 +523,7 @@ impl Abba {
}

match just_1.as_ref() {
PreVoteJustification::FirstRoundOne(digest, sig) => {
PreVoteJustification::WithValidity(digest, sig) => {
let sign_bytes = crate::mvba::vcbc::c_ready_bytes_to_sign(
&self.id, &self.j, digest,
)?;
Expand Down Expand Up @@ -534,6 +563,8 @@ impl Abba {
// broadcast sends the message `msg` to all other peers in the network.
// It adds the message to our messages log.
fn broadcast(&mut self, action: Action) -> Result<()> {
log::debug!("broadcasting {action:?}");

let msg = Message {
id: self.id.clone(),
proposer: self.j,
Expand Down

0 comments on commit de476d3

Please sign in to comment.