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checking proofs in safe contract

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This commit is contained in:
Robert Habermeier
2017-07-28 19:38:52 +02:00
parent e84f308264
commit 2bd5c3dba7
4 changed files with 124 additions and 75 deletions
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138
ethcore/src/engines/validator_set/safe_contract.rs
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@@ -44,6 +44,29 @@ lazy_static! {
static ref EVENT_NAME_HASH: H256 = EVENT_NAME.sha3();
}
// state-dependent proofs for the safe contract:
// only "first" proofs are such.
struct StateProof {
header: Header,
provider: Provider,
}
impl ::engines::StateDependentProof for StateProof {
fn generate_proof(&self, caller: &Call) -> Result<Vec<u8>, String> {
prove_initial(&self.provider, &self.header, caller)
}
fn check_proof(&self, engine: &Engine, proof: &[u8]) -> Result<(), String> {
let (header, state_items) = decode_first_proof(&UntrustedRlp::new(proof))
.map_err(|e| format!("proof incorrectly encoded: {}", e))?;
if header != self.header {
return Err("wrong header in proof".into());
}
check_first_proof(engine, &self.provider, header, &state_items).map(|_| ())
}
}
/// The validator contract should have the following interface:
pub struct ValidatorSafeContract {
pub address: Address,
@@ -63,6 +86,59 @@ fn encode_first_proof(header: &Header, state_items: &[Vec<u8>]) -> Bytes {
stream.out()
}
// check a first proof: fetch the validator set at the given block.
fn check_first_proof(engine: &Engine, provider: &Provider, old_header: Header, state_items: &[DBValue])
-> Result<Vec<Address>, String>
{
use transaction::{Action, Transaction};
// TODO: match client contract_call_tx more cleanly without duplication.
const PROVIDED_GAS: u64 = 50_000_000;
let env_info = ::evm::env_info::EnvInfo {
number: old_header.number(),
author: *old_header.author(),
difficulty: *old_header.difficulty(),
gas_limit: PROVIDED_GAS.into(),
timestamp: old_header.timestamp(),
last_hashes: {
// this will break if we don't inclue all 256 last hashes.
let mut last_hashes: Vec<_> = (0..256).map(|_| H256::default()).collect();
last_hashes[255] = *old_header.parent_hash();
Arc::new(last_hashes)
},
gas_used: 0.into(),
};
// check state proof using given engine.
let number = old_header.number();
provider.get_validators(move |a, d| {
let from = Address::default();
let tx = Transaction {
nonce: engine.account_start_nonce(number),
action: Action::Call(a),
gas: PROVIDED_GAS.into(),
gas_price: U256::default(),
value: U256::default(),
data: d,
}.fake_sign(from);
let res = ::state::check_proof(
state_items,
*old_header.state_root(),
&tx,
engine,
&env_info,
);
match res {
::state::ProvedExecution::BadProof => Err("Bad proof".into()),
::state::ProvedExecution::Failed(e) => Err(format!("Failed call: {}", e)),
::state::ProvedExecution::Complete(e) => Ok(e.output),
}
}).wait()
}
fn decode_first_proof(rlp: &UntrustedRlp) -> Result<(Header, Vec<DBValue>), ::error::Error> {
let header = rlp.val_at(0)?;
let state_items = rlp.at(1)?.iter().map(|x| {
@@ -100,8 +176,7 @@ fn prove_initial(provider: &Provider, header: &Header, caller: &Call) -> Result<
Ok(result)
};
provider.get_validators(caller)
.wait()
provider.get_validators(caller).wait()
};
res.map(|validators| {
@@ -255,9 +330,11 @@ impl ValidatorSet for ValidatorSafeContract {
// transition to the first block of a contract requires finality but has no log event.
if first {
debug!(target: "engine", "signalling transition to fresh contract.");
let (provider, header) = (self.provider.clone(), header.clone());
let with_caller: Box<Fn(&Call) -> _> = Box::new(move |caller| prove_initial(&provider, &header, caller));
return ::engines::EpochChange::Yes(::engines::Proof::WithState(with_caller))
let state_proof = Box::new(StateProof {
header: header.clone(),
provider: self.provider.clone(),
});
return ::engines::EpochChange::Yes(::engines::Proof::WithState(state_proof as Box<_>));
}
// otherwise, we're checking for logs.
@@ -286,61 +363,16 @@ impl ValidatorSet for ValidatorSafeContract {
fn epoch_set(&self, first: bool, engine: &Engine, _number: ::header::BlockNumber, proof: &[u8])
-> Result<(SimpleList, Option<H256>), ::error::Error>
{
use transaction::{Action, Transaction};
let rlp = UntrustedRlp::new(proof);
if first {
trace!(target: "engine", "Recovering initial epoch set");
// TODO: match client contract_call_tx more cleanly without duplication.
const PROVIDED_GAS: u64 = 50_000_000;
let (old_header, state_items) = decode_first_proof(&rlp)?;
let old_hash = old_header.hash();
let env_info = ::evm::env_info::EnvInfo {
number: old_header.number(),
author: *old_header.author(),
difficulty: *old_header.difficulty(),
gas_limit: PROVIDED_GAS.into(),
timestamp: old_header.timestamp(),
last_hashes: {
// this will break if we don't inclue all 256 last hashes.
let mut last_hashes: Vec<_> = (0..256).map(|_| H256::default()).collect();
last_hashes[255] = *old_header.parent_hash();
Arc::new(last_hashes)
},
gas_used: 0.into(),
};
// check state proof using given engine.
let number = old_header.number();
let addresses = self.provider.get_validators(move |a, d| {
let from = Address::default();
let tx = Transaction {
nonce: engine.account_start_nonce(number),
action: Action::Call(a),
gas: PROVIDED_GAS.into(),
gas_price: U256::default(),
value: U256::default(),
data: d,
}.fake_sign(from);
let res = ::state::check_proof(
&state_items,
*old_header.state_root(),
&tx,
engine,
&env_info,
);
match res {
::state::ProvedExecution::BadProof => Err("Bad proof".into()),
::state::ProvedExecution::Failed(e) => Err(format!("Failed call: {}", e)),
::state::ProvedExecution::Complete(e) => Ok(e.output),
}
}).wait().map_err(::engines::EngineError::InsufficientProof)?;
let old_hash = old_header.hash();
let addresses = check_first_proof(engine, &self.provider, old_header, &state_items)
.map_err(::engines::EngineError::InsufficientProof)?;
trace!(target: "engine", "extracted epoch set at #{}: {} addresses",
number, addresses.len());