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Fixes for misbehavior reporting in AuthorityRound (#8998)
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* aura: only report after checking for repeated skipped primaries

* aura: refactor duplicate code for getting epoch validator set

* aura: verify_external: report on validator set contract instance

* aura: use correct validator set epoch number when reporting

* aura: use epoch set when verifying blocks

* aura: report skipped primaries when generating seal

* aura: handle immediate transitions

* aura: don't report skipped steps from genesis to first block

* aura: fix reporting test

* aura: refactor duplicate code to handle immediate_transitions

* aura: let reporting fail on verify_block_basic

* aura: add comment about possible failure of reporting
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@andresilva @ordian
andresilva authored and ordian committed Jul 7, 2018
1 parent 25b900e commit 1a75813
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Showing 3 changed files with 124 additions and 82 deletions.
198 changes: 117 additions & 81 deletions ethcore/src/engines/authority_round/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -16,20 +16,21 @@

//! A blockchain engine that supports a non-instant BFT proof-of-authority.
use std::collections::{BTreeMap, HashSet};
use std::fmt;
use std::iter::FromIterator;
use std::ops::Deref;
use std::sync::atomic::{AtomicUsize, AtomicBool, Ordering as AtomicOrdering};
use std::sync::{Weak, Arc};
use std::time::{UNIX_EPOCH, SystemTime, Duration};
use std::collections::{BTreeMap, HashSet};
use std::iter::FromIterator;

use account_provider::AccountProvider;
use block::*;
use client::EngineClient;
use engines::{Engine, Seal, EngineError, ConstructedVerifier};
use engines::block_reward;
use engines::block_reward::{BlockRewardContract, RewardKind};
use error::{Error, BlockError};
use error::{Error, ErrorKind, BlockError};
use ethjson;
use machine::{AuxiliaryData, Call, EthereumMachine};
use hash::keccak;
Expand Down Expand Up @@ -575,7 +576,6 @@ fn verify_external(header: &Header, validators: &ValidatorSet, empty_steps_trans

if is_invalid_proposer {
trace!(target: "engine", "verify_block_external: bad proposer for step: {}", header_step);
validators.report_benign(header.author(), header.number(), header.number());
Err(EngineError::NotProposer(Mismatch { expected: correct_proposer, found: header.author().clone() }))?
} else {
Ok(())
Expand Down Expand Up @@ -607,6 +607,23 @@ impl AsMillis for Duration {
}
}

// A type for storing owned or borrowed data that has a common type.
// Useful for returning either a borrow or owned data from a function.
enum CowLike<'a, A: 'a + ?Sized, B> {
Borrowed(&'a A),
Owned(B),
}

impl<'a, A: ?Sized, B> Deref for CowLike<'a, A, B> where B: AsRef<A> {
type Target = A;
fn deref(&self) -> &A {
match self {
CowLike::Borrowed(b) => b,
CowLike::Owned(o) => o.as_ref(),
}
}
}

impl AuthorityRound {
/// Create a new instance of AuthorityRound engine.
pub fn new(our_params: AuthorityRoundParams, machine: EthereumMachine) -> Result<Arc<Self>, Error> {
Expand Down Expand Up @@ -656,6 +673,30 @@ impl AuthorityRound {
Ok(engine)
}

// fetch correct validator set for epoch at header, taking into account
// finality of previous transitions.
fn epoch_set<'a>(&'a self, header: &Header) -> Result<(CowLike<ValidatorSet, SimpleList>, BlockNumber), Error> {
Ok(if self.immediate_transitions {
(CowLike::Borrowed(&*self.validators), header.number())
} else {
let mut epoch_manager = self.epoch_manager.lock();
let client = match self.client.read().as_ref().and_then(|weak| weak.upgrade()) {
Some(client) => client,
None => {
debug!(target: "engine", "Unable to verify sig: missing client ref.");
return Err(EngineError::RequiresClient.into())
}
};

if !epoch_manager.zoom_to(&*client, &self.machine, &*self.validators, header) {
debug!(target: "engine", "Unable to zoom to epoch.");
return Err(EngineError::RequiresClient.into())
}

(CowLike::Owned(epoch_manager.validators().clone()), epoch_manager.epoch_transition_number)
})
}

fn empty_steps(&self, from_step: U256, to_step: U256, parent_hash: H256) -> Vec<EmptyStep> {
self.empty_steps.lock().iter().filter(|e| {
U256::from(e.step) > from_step &&
Expand Down Expand Up @@ -701,6 +742,28 @@ impl AuthorityRound {
}
}
}

fn report_skipped(&self, header: &Header, current_step: usize, parent_step: usize, validators: &ValidatorSet, set_number: u64) {
// we're building on top of the genesis block so don't report any skipped steps
if header.number() == 1 {
return;
}

if let (true, Some(me)) = (current_step > parent_step + 1, self.signer.read().address()) {
debug!(target: "engine", "Author {} built block with step gap. current step: {}, parent step: {}",
header.author(), current_step, parent_step);
let mut reported = HashSet::new();
for step in parent_step + 1..current_step {
let skipped_primary = step_proposer(validators, header.parent_hash(), step);
// Do not report this signer.
if skipped_primary != me {
// Stop reporting once validators start repeating.
if !reported.insert(skipped_primary) { break; }
self.validators.report_benign(&skipped_primary, set_number, header.number());
}
}
}
}
}

fn unix_now() -> Duration {
Expand Down Expand Up @@ -880,32 +943,15 @@ impl Engine<EthereumMachine> for AuthorityRound {
return Seal::None;
}

// fetch correct validator set for current epoch, taking into account
// finality of previous transitions.
let active_set;

let validators = if self.immediate_transitions {
&*self.validators
} else {
let mut epoch_manager = self.epoch_manager.lock();
let client = match self.client.read().as_ref().and_then(|weak| weak.upgrade()) {
Some(client) => client,
None => {
warn!(target: "engine", "Unable to generate seal: missing client ref.");
return Seal::None;
}
};

if !epoch_manager.zoom_to(&*client, &self.machine, &*self.validators, header) {
debug!(target: "engine", "Unable to zoom to epoch.");
let (validators, set_number) = match self.epoch_set(header) {
Err(err) => {
warn!(target: "engine", "Unable to generate seal: {}", err);
return Seal::None;
}

active_set = epoch_manager.validators().clone();
&active_set as &_
},
Ok(ok) => ok,
};

if is_step_proposer(validators, header.parent_hash(), step, header.author()) {
if is_step_proposer(&*validators, header.parent_hash(), step, header.author()) {
// this is guarded against by `can_propose` unless the block was signed
// on the same step (implies same key) and on a different node.
if parent_step == step.into() {
Expand Down Expand Up @@ -936,9 +982,15 @@ impl Engine<EthereumMachine> for AuthorityRound {

// only issue the seal if we were the first to reach the compare_and_swap.
if self.step.can_propose.compare_and_swap(true, false, AtomicOrdering::SeqCst) {

// we can drop all accumulated empty step messages that are
// older than the parent step since we're including them in
// the seal
self.clear_empty_steps(parent_step);

// report any skipped primaries between the parent block and
// the block we're sealing
self.report_skipped(header, step, u64::from(parent_step) as usize, &*validators, set_number);

let mut fields = vec![
encode(&step).into_vec(),
encode(&(&H520::from(signature) as &[u8])).into_vec(),
Expand Down Expand Up @@ -1057,13 +1109,21 @@ impl Engine<EthereumMachine> for AuthorityRound {
)));
}

// TODO [ToDr] Should this go from epoch manager?
// If yes then probably benign reporting needs to be moved further in the verification.
let set_number = header.number();

match verify_timestamp(&self.step.inner, header_step(header, self.empty_steps_transition)?) {
Err(BlockError::InvalidSeal) => {
self.validators.report_benign(header.author(), set_number, header.number());
// This check runs in Phase 1 where there is no guarantee that the parent block is
// already imported, therefore the call to `epoch_set` may fail. In that case we
// won't report the misbehavior but this is not a concern because:
// - Only authorities can report and it's expected that they'll be up-to-date and
// importing, therefore the parent header will most likely be available
// - Even if you are an authority that is syncing the chain, the contract will most
// likely ignore old reports
// - This specific check is only relevant if you're importing (since it checks
// against wall clock)
if let Ok((_, set_number)) = self.epoch_set(header) {
self.validators.report_benign(header.author(), set_number, header.number());
}

Err(BlockError::InvalidSeal.into())
}
Err(e) => Err(e.into()),
Expand All @@ -1075,8 +1135,8 @@ impl Engine<EthereumMachine> for AuthorityRound {
fn verify_block_family(&self, header: &Header, parent: &Header) -> Result<(), Error> {
let step = header_step(header, self.empty_steps_transition)?;
let parent_step = header_step(parent, self.empty_steps_transition)?;
// TODO [ToDr] Should this go from epoch manager?
let set_number = header.number();

let (validators, set_number) = self.epoch_set(header)?;

// Ensure header is from the step after parent.
if step == parent_step
Expand All @@ -1103,7 +1163,7 @@ impl Engine<EthereumMachine> for AuthorityRound {
format!("empty step proof for invalid parent hash: {:?}", empty_step.parent_hash)))?;
}

if !empty_step.verify(&*self.validators).unwrap_or(false) {
if !empty_step.verify(&*validators).unwrap_or(false) {
Err(EngineError::InsufficientProof(
format!("invalid empty step proof: {:?}", empty_step)))?;
}
Expand All @@ -1117,59 +1177,29 @@ impl Engine<EthereumMachine> for AuthorityRound {
}

} else {
// Report skipped primaries.
if let (true, Some(me)) = (step > parent_step + 1, self.signer.read().address()) {
debug!(target: "engine", "Author {} built block with step gap. current step: {}, parent step: {}",
header.author(), step, parent_step);
let mut reported = HashSet::new();
for s in parent_step + 1..step {
let skipped_primary = step_proposer(&*self.validators, &parent.hash(), s);
// Do not report this signer.
if skipped_primary != me {
self.validators.report_benign(&skipped_primary, set_number, header.number());
// Stop reporting once validators start repeating.
if !reported.insert(skipped_primary) { break; }
}
}
}
self.report_skipped(header, step, parent_step, &*validators, set_number);
}

Ok(())
}

// Check the validators.
fn verify_block_external(&self, header: &Header) -> Result<(), Error> {
// fetch correct validator set for current epoch, taking into account
// finality of previous transitions.
let active_set;
let validators = if self.immediate_transitions {
&*self.validators
} else {
// get correct validator set for epoch.
let client = match self.client.read().as_ref().and_then(|weak| weak.upgrade()) {
Some(client) => client,
None => {
debug!(target: "engine", "Unable to verify sig: missing client ref.");
return Err(EngineError::RequiresClient.into())
}
};

let mut epoch_manager = self.epoch_manager.lock();
if !epoch_manager.zoom_to(&*client, &self.machine, &*self.validators, header) {
debug!(target: "engine", "Unable to zoom to epoch.");
return Err(EngineError::RequiresClient.into())
}

active_set = epoch_manager.validators().clone();
&active_set as &_
};
let (validators, set_number) = self.epoch_set(header)?;

// verify signature against fixed list, but reports should go to the
// contract itself.
let res = verify_external(header, validators, self.empty_steps_transition);
if res.is_ok() {
let header_step = header_step(header, self.empty_steps_transition)?;
self.clear_empty_steps(header_step.into());
let res = verify_external(header, &*validators, self.empty_steps_transition);
match res {
Err(Error(ErrorKind::Engine(EngineError::NotProposer(_)), _)) => {
self.validators.report_benign(header.author(), set_number, header.number());
},
Ok(_) => {
// we can drop all accumulated empty step messages that are older than this header's step
let header_step = header_step(header, self.empty_steps_transition)?;
self.clear_empty_steps(header_step.into());
},
_ => {},
}
res
}
Expand Down Expand Up @@ -1574,7 +1604,6 @@ mod tests {
parent_header.set_seal(vec![encode(&1usize).into_vec()]);
parent_header.set_gas_limit("222222".parse::<U256>().unwrap());
let mut header: Header = Header::default();
header.set_number(1);
header.set_gas_limit("222222".parse::<U256>().unwrap());
header.set_seal(vec![encode(&3usize).into_vec()]);

Expand All @@ -1584,8 +1613,15 @@ mod tests {

aura.set_signer(Arc::new(AccountProvider::transient_provider()), Default::default(), Default::default());

// Do not report on steps skipped between genesis and first block.
header.set_number(1);
assert!(aura.verify_block_family(&header, &parent_header).is_ok());
assert_eq!(last_benign.load(AtomicOrdering::SeqCst), 0);

// Report on skipped steps otherwise.
header.set_number(2);
assert!(aura.verify_block_family(&header, &parent_header).is_ok());
assert_eq!(last_benign.load(AtomicOrdering::SeqCst), 1);
assert_eq!(last_benign.load(AtomicOrdering::SeqCst), 2);
}

#[test]
Expand Down
2 changes: 1 addition & 1 deletion ethcore/src/engines/validator_set/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,7 @@ pub fn new_validator_set(spec: ValidatorSpec) -> Box<ValidatorSet> {
}

/// A validator set.
pub trait ValidatorSet: Send + Sync {
pub trait ValidatorSet: Send + Sync + 'static {
/// Get the default "Call" helper, for use in general operation.
// TODO [keorn]: this is a hack intended to migrate off of
// a strict dependency on state always being available.
Expand Down
6 changes: 6 additions & 0 deletions ethcore/src/engines/validator_set/simple_list.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -104,6 +104,12 @@ impl ValidatorSet for SimpleList {
}
}

impl AsRef<ValidatorSet> for SimpleList {
fn as_ref(&self) -> &ValidatorSet {
self
}
}

#[cfg(test)]
mod tests {
use std::str::FromStr;
Expand Down

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