add consensus module

This commit is contained in:
Noah Citron 2022-08-19 18:43:58 -04:00
parent c21f431673
commit 2040614e1b
5 changed files with 344 additions and 343 deletions

325
src/consensus.rs Normal file
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@ -0,0 +1,325 @@
use eyre::Result;
use ssz_rs::prelude::*;
use blst::min_pk::{PublicKey, Signature};
use blst::BLST_ERROR;
use super::consensus_rpc::*;
use super::utils::*;
pub struct ConsensusClient {
consensus_rpc: ConsensusRpc,
store: Store,
}
#[derive(Debug)]
struct Store {
header: Header,
current_sync_committee: SyncCommittee,
next_sync_committee: Option<SyncCommittee>,
}
impl ConsensusClient {
pub async fn new(nimbus_rpc: &str, checkpoint_block_root: &str) -> Result<ConsensusClient> {
let consensus_rpc = ConsensusRpc::new(nimbus_rpc);
let mut bootstrap = consensus_rpc.get_bootstrap(checkpoint_block_root).await?;
let committee_valid = is_current_committee_proof_valid(
&bootstrap.header,
&mut bootstrap.current_sync_committee,
&bootstrap.current_sync_committee_branch
);
let header_hash = bootstrap.header.hash_tree_root()?;
let header_valid = header_hash.to_string() == checkpoint_block_root.to_string();
if !(header_valid && committee_valid) {
return Err(eyre::eyre!("Invalid Bootstrap"));
}
let store = Store {
header: bootstrap.header,
current_sync_committee: bootstrap.current_sync_committee,
next_sync_committee: None,
};
Ok(ConsensusClient { consensus_rpc, store })
}
pub async fn get_execution_payload(&mut self) -> Result<ExecutionPayload> {
let slot = self.store.header.slot;
let mut block = self.consensus_rpc.get_block(slot).await?;
let block_hash = block.hash_tree_root()?;
let verified_block_hash = self.store.header.hash_tree_root()?;
if verified_block_hash != block_hash {
Err(eyre::eyre!("Block Root Mismatch"))
} else {
Ok(block.body.execution_payload)
}
}
pub async fn sync(&mut self) -> Result<()> {
let current_period = calc_sync_period(self.store.header.slot);
let updates = self.consensus_rpc.get_updates(current_period).await?;
for mut update in updates {
self.verify_update(&mut update)?;
self.apply_update(&update);
}
let finality_update = self.consensus_rpc.get_finality_update().await?;
let mut finality_update_generic = Update {
attested_header: finality_update.attested_header,
next_sync_committee: None,
next_sync_committee_branch: Vec::new(),
finalized_header: finality_update.finalized_header,
finality_branch: finality_update.finality_branch,
sync_aggregate: finality_update.sync_aggregate,
signature_slot: finality_update.signature_slot,
};
self.verify_update(&mut finality_update_generic)?;
self.apply_update(&finality_update_generic);
println!("synced up to slot: {}", self.store.header.slot);
self.consensus_rpc.get_block(self.store.header.slot).await?;
Ok(())
}
fn verify_update(&mut self, update: &mut Update) -> Result<()> {
let current_slot = self.store.header.slot;
let update_slot = update.finalized_header.slot;
let current_period = calc_sync_period(current_slot);
let update_period = calc_sync_period(update_slot);
if !(update_period == current_period + 1 || update_period == current_period) {
return Err(eyre::eyre!("Invalid Update"));
}
if !(update.signature_slot > update.attested_header.slot && update.attested_header.slot > update.finalized_header.slot) {
return Err(eyre::eyre!("Invalid Update"));
}
let finality_branch_valid = is_finality_proof_valid(
&update.attested_header,
&mut update.finalized_header,
&update.finality_branch
);
if !(finality_branch_valid) {
return Err(eyre::eyre!("Invalid Update"));
}
if update.next_sync_committee.is_some() {
let next_committee_branch_valid = is_next_committee_proof_valid(
&update.attested_header,
&mut update.next_sync_committee.clone().unwrap(),
&update.next_sync_committee_branch
);
if !next_committee_branch_valid {
return Err(eyre::eyre!("Invalid Update"));
}
}
let sync_committee = if current_period == update_period {
&self.store.current_sync_committee
} else {
self.store.next_sync_committee.as_ref().unwrap()
};
let pks = get_participating_keys(sync_committee, &update.sync_aggregate.sync_committee_bits)?;
let pks: Vec<&PublicKey> = pks.iter().map(|pk| pk).collect();
let committee_quorum = pks.len() > 1;
if !committee_quorum {
return Err(eyre::eyre!("Invalid Update"));
}
let header_root = bytes_to_bytes32(update.attested_header.hash_tree_root()?.as_bytes());
let signing_root = compute_committee_sign_root(header_root)?;
let sig = &update.sync_aggregate.sync_committee_signature;
let is_valid_sig = is_aggregate_valid(sig, signing_root.as_bytes(), &pks);
if !is_valid_sig {
return Err(eyre::eyre!("Invalid Update"));
}
Ok(())
}
fn apply_update(&mut self, update: &Update) {
let current_period = calc_sync_period(self.store.header.slot);
let update_period = calc_sync_period(update.finalized_header.slot);
self.store.header = update.finalized_header.clone();
if self.store.next_sync_committee.is_none() {
self.store.next_sync_committee = Some(update.next_sync_committee.as_ref().unwrap().clone());
} else if update_period == current_period + 1 {
self.store.current_sync_committee = self.store.next_sync_committee.as_ref().unwrap().clone();
self.store.next_sync_committee = Some(update.next_sync_committee.as_ref().unwrap().clone());
}
}
}
fn get_participating_keys(committee: &SyncCommittee, bitfield: &Bitvector<512>) -> Result<Vec<PublicKey>> {
let mut pks: Vec<PublicKey> = Vec::new();
bitfield.iter().enumerate().for_each(|(i, bit)| {
if bit == true {
let pk = &committee.pubkeys[i];
let pk = PublicKey::from_bytes(&pk).unwrap();
pks.push(pk);
}
});
Ok(pks)
}
fn is_aggregate_valid(sig_bytes: &SignatureBytes, msg: &[u8], pks: &[&PublicKey]) -> bool {
let dst: &[u8] = b"BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_POP_";
let sig_res = Signature::from_bytes(&sig_bytes);
match sig_res {
Ok(sig) => sig.fast_aggregate_verify(true, msg, dst, &pks) == BLST_ERROR::BLST_SUCCESS,
Err(_) => false,
}
}
fn is_finality_proof_valid(attested_header: &Header, finality_header: &mut Header, finality_branch: &Vec<Bytes32>) -> bool {
let finality_header_hash_res = finality_header.hash_tree_root();
if finality_header_hash_res.is_err() {
return false;
}
let attested_header_state_root_res = bytes32_to_node(&attested_header.state_root);
if attested_header_state_root_res.is_err() {
return false;
}
let finality_branch_res = branch_to_nodes(finality_branch.clone());
if finality_branch_res.is_err() {
return false;
}
is_valid_merkle_branch(
&finality_header_hash_res.unwrap(),
finality_branch_res.unwrap().iter(),
6,
41,
&attested_header_state_root_res.unwrap()
)
}
fn is_next_committee_proof_valid(
attested_header: &Header,
next_committee: &mut SyncCommittee,
next_committee_branch: &Vec<Bytes32>
) -> bool {
let next_committee_hash_res = next_committee.hash_tree_root();
if next_committee_hash_res.is_err() {
return false;
}
let attested_header_state_root_res = bytes32_to_node(&attested_header.state_root);
if attested_header_state_root_res.is_err() {
return false;
}
let next_committee_branch_res = branch_to_nodes(next_committee_branch.clone());
if next_committee_branch_res.is_err() {
return false;
}
is_valid_merkle_branch(
&next_committee_hash_res.unwrap(),
next_committee_branch_res.unwrap().iter(),
5,
23,
&attested_header_state_root_res.unwrap()
)
}
fn is_current_committee_proof_valid(
attested_header: &Header,
current_committee: &mut SyncCommittee,
current_committee_branch: &Vec<Bytes32>
) -> bool {
let next_committee_hash_res = current_committee.hash_tree_root();
if next_committee_hash_res.is_err() {
return false;
}
let attested_header_state_root_res = bytes32_to_node(&attested_header.state_root);
if attested_header_state_root_res.is_err() {
return false;
}
let next_committee_branch_res = branch_to_nodes(current_committee_branch.clone());
if next_committee_branch_res.is_err() {
return false;
}
is_valid_merkle_branch(
&next_committee_hash_res.unwrap(),
next_committee_branch_res.unwrap().iter(),
5,
22,
&attested_header_state_root_res.unwrap()
)
}
fn calc_sync_period(slot: u64) -> u64 {
let epoch = slot / 32;
epoch / 256
}
fn branch_to_nodes(branch: Vec<Bytes32>) -> Result<Vec<Node>> {
branch.iter().map(|elem| bytes32_to_node(elem)).collect::<Result<Vec<Node>>>()
}
fn compute_committee_sign_root(header: Bytes32) -> Result<Node> {
let genesis_root = hex::decode("043db0d9a83813551ee2f33450d23797757d430911a9320530ad8a0eabc43efb")?.to_vec().try_into().unwrap();
let domain_type = &hex::decode("07000000")?[..];
let fork_version = Vector::from_iter(hex::decode("02001020").unwrap());
let domain = compute_domain(domain_type, fork_version, genesis_root)?;
compute_signing_root(header, domain)
}
#[derive(SimpleSerialize, Default, Debug)]
struct SigningData {
object_root: Bytes32,
domain: Bytes32
}
#[derive(SimpleSerialize, Default, Debug)]
struct ForkData {
current_version: Vector<u8, 4>,
genesis_validator_root: Bytes32,
}
fn compute_signing_root(object_root: Bytes32, domain: Bytes32) -> Result<Node> {
let mut data = SigningData { object_root, domain };
Ok(data.hash_tree_root()?)
}
fn compute_domain(domain_type: &[u8], fork_version: Vector<u8, 4>, genesis_root: Bytes32) -> Result<Bytes32> {
let fork_data_root = compute_fork_data_root(fork_version, genesis_root)?;
let start = domain_type;
let end = &fork_data_root.as_bytes()[..28];
let d = [start, end].concat();
Ok(d.to_vec().try_into().unwrap())
}
fn compute_fork_data_root(current_version: Vector<u8, 4>, genesis_validator_root: Bytes32) -> Result<Node> {
let current_version = current_version.try_into()?;
let mut fork_data = ForkData { current_version, genesis_validator_root };
Ok(fork_data.hash_tree_root()?)
}

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@ -3,13 +3,13 @@ use ssz_rs::prelude::*;
use super::utils::*; use super::utils::*;
use serde::de::Error; use serde::de::Error;
pub struct ConsensusClient { pub struct ConsensusRpc {
rpc: String, rpc: String,
} }
impl ConsensusClient { impl ConsensusRpc {
pub fn new(rpc: &str) -> Self { pub fn new(rpc: &str) -> Self {
ConsensusClient { rpc: rpc.to_string() } ConsensusRpc { rpc: rpc.to_string() }
} }
pub async fn get_bootstrap(&self, block_root: &str) -> Result<Bootstrap> { pub async fn get_bootstrap(&self, block_root: &str) -> Result<Bootstrap> {

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@ -1,348 +1,24 @@
use eyre::Result; use eyre::Result;
use ssz_rs::prelude::*;
use blst::{min_pk::*, BLST_ERROR};
use consensus_client::*;
use utils::*;
use proof::*;
pub mod consensus_client; use consensus::*;
pub mod consensus;
pub mod consensus_rpc;
pub mod utils; pub mod utils;
pub mod proof; pub mod proof;
#[tokio::main] #[tokio::main]
async fn main() -> Result<()> { async fn main() -> Result<()> {
// let mut client = LightClient::new( let rpc = "http://testing.prater.beacon-api.nimbus.team";
// "http://testing.prater.beacon-api.nimbus.team", let checkpoint = "0x172128eadf1da46467f4d6a822206698e2d3f957af117dd650954780d680dc99";
// "0x172128eadf1da46467f4d6a822206698e2d3f957af117dd650954780d680dc99" let mut client = ConsensusClient::new(rpc, checkpoint).await?;
// ).await?;
// client.sync().await?;
// client.sync().await?;
// let payload = client.get_execution_payload().await?; let payload = client.get_execution_payload().await?;
// println!("verified execution block hash: {}", hex::encode(payload.block_hash)); println!("verified execution block hash: {}", hex::encode(payload.block_hash));
let proof = get_proof("0x88A83e0F661447576fb1f50e5d90d571E379cd72", 15365981).await?;
let is_valid = verify(&proof);
println!("{:?}", is_valid);
Ok(()) Ok(())
} }
struct LightClient {
consensus_client: ConsensusClient,
store: Store,
}
#[derive(Debug)]
struct Store {
header: Header,
current_sync_committee: SyncCommittee,
next_sync_committee: Option<SyncCommittee>,
}
impl LightClient {
async fn new(nimbus_rpc: &str, checkpoint_block_root: &str) -> Result<LightClient> {
let consensus_client = ConsensusClient::new(nimbus_rpc);
let mut bootstrap = consensus_client.get_bootstrap(checkpoint_block_root).await?;
let committee_valid = is_current_committee_proof_valid(
&bootstrap.header,
&mut bootstrap.current_sync_committee,
&bootstrap.current_sync_committee_branch
);
let header_hash = bootstrap.header.hash_tree_root()?;
let header_valid = header_hash.to_string() == checkpoint_block_root.to_string();
if !(header_valid && committee_valid) {
return Err(eyre::eyre!("Invalid Bootstrap"));
}
let store = Store {
header: bootstrap.header,
current_sync_committee: bootstrap.current_sync_committee,
next_sync_committee: None,
};
Ok(LightClient { consensus_client, store })
}
async fn get_execution_payload(&mut self) -> Result<ExecutionPayload> {
let slot = self.store.header.slot;
let mut block = self.consensus_client.get_block(slot).await?;
let block_hash = block.hash_tree_root()?;
let verified_block_hash = self.store.header.hash_tree_root()?;
if verified_block_hash != block_hash {
Err(eyre::eyre!("Block Root Mismatch"))
} else {
Ok(block.body.execution_payload)
}
}
async fn sync(&mut self) -> Result<()> {
let current_period = calc_sync_period(self.store.header.slot);
let updates = self.consensus_client.get_updates(current_period).await?;
for mut update in updates {
self.verify_update(&mut update)?;
self.apply_update(&update);
}
let finality_update = self.consensus_client.get_finality_update().await?;
let mut finality_update_generic = Update {
attested_header: finality_update.attested_header,
next_sync_committee: None,
next_sync_committee_branch: Vec::new(),
finalized_header: finality_update.finalized_header,
finality_branch: finality_update.finality_branch,
sync_aggregate: finality_update.sync_aggregate,
signature_slot: finality_update.signature_slot,
};
self.verify_update(&mut finality_update_generic)?;
self.apply_update(&finality_update_generic);
println!("synced up to slot: {}", self.store.header.slot);
self.consensus_client.get_block(self.store.header.slot).await?;
Ok(())
}
fn verify_update(&mut self, update: &mut Update) -> Result<()> {
let current_slot = self.store.header.slot;
let update_slot = update.finalized_header.slot;
let current_period = calc_sync_period(current_slot);
let update_period = calc_sync_period(update_slot);
if !(update_period == current_period + 1 || update_period == current_period) {
return Err(eyre::eyre!("Invalid Update"));
}
if !(update.signature_slot > update.attested_header.slot && update.attested_header.slot > update.finalized_header.slot) {
return Err(eyre::eyre!("Invalid Update"));
}
let finality_branch_valid = is_finality_proof_valid(
&update.attested_header,
&mut update.finalized_header,
&update.finality_branch
);
if !(finality_branch_valid) {
return Err(eyre::eyre!("Invalid Update"));
}
if update.next_sync_committee.is_some() {
let next_committee_branch_valid = is_next_committee_proof_valid(
&update.attested_header,
&mut update.next_sync_committee.clone().unwrap(),
&update.next_sync_committee_branch
);
if !next_committee_branch_valid {
return Err(eyre::eyre!("Invalid Update"));
}
}
let sync_committee = if current_period == update_period {
&self.store.current_sync_committee
} else {
self.store.next_sync_committee.as_ref().unwrap()
};
let pks = get_participating_keys(sync_committee, &update.sync_aggregate.sync_committee_bits)?;
let pks: Vec<&PublicKey> = pks.iter().map(|pk| pk).collect();
let committee_quorum = pks.len() > 1;
if !committee_quorum {
return Err(eyre::eyre!("Invalid Update"));
}
let header_root = bytes_to_bytes32(update.attested_header.hash_tree_root()?.as_bytes());
let signing_root = compute_committee_sign_root(header_root)?;
let sig = &update.sync_aggregate.sync_committee_signature;
let is_valid_sig = is_aggregate_valid(sig, signing_root.as_bytes(), &pks);
if !is_valid_sig {
return Err(eyre::eyre!("Invalid Update"));
}
Ok(())
}
fn apply_update(&mut self, update: &Update) {
let current_period = calc_sync_period(self.store.header.slot);
let update_period = calc_sync_period(update.finalized_header.slot);
self.store.header = update.finalized_header.clone();
if self.store.next_sync_committee.is_none() {
self.store.next_sync_committee = Some(update.next_sync_committee.as_ref().unwrap().clone());
} else if update_period == current_period + 1 {
self.store.current_sync_committee = self.store.next_sync_committee.as_ref().unwrap().clone();
self.store.next_sync_committee = Some(update.next_sync_committee.as_ref().unwrap().clone());
}
}
}
fn get_participating_keys(committee: &SyncCommittee, bitfield: &Bitvector<512>) -> Result<Vec<PublicKey>> {
let mut pks: Vec<PublicKey> = Vec::new();
bitfield.iter().enumerate().for_each(|(i, bit)| {
if bit == true {
let pk = &committee.pubkeys[i];
let pk = PublicKey::from_bytes(&pk).unwrap();
pks.push(pk);
}
});
Ok(pks)
}
fn is_aggregate_valid(sig_bytes: &SignatureBytes, msg: &[u8], pks: &[&PublicKey]) -> bool {
let dst: &[u8] = b"BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_POP_";
let sig_res = Signature::from_bytes(&sig_bytes);
match sig_res {
Ok(sig) => sig.fast_aggregate_verify(true, msg, dst, &pks) == BLST_ERROR::BLST_SUCCESS,
Err(_) => false,
}
}
fn is_finality_proof_valid(attested_header: &Header, finality_header: &mut Header, finality_branch: &Vec<Bytes32>) -> bool {
let finality_header_hash_res = finality_header.hash_tree_root();
if finality_header_hash_res.is_err() {
return false;
}
let attested_header_state_root_res = bytes32_to_node(&attested_header.state_root);
if attested_header_state_root_res.is_err() {
return false;
}
let finality_branch_res = branch_to_nodes(finality_branch.clone());
if finality_branch_res.is_err() {
return false;
}
is_valid_merkle_branch(
&finality_header_hash_res.unwrap(),
finality_branch_res.unwrap().iter(),
6,
41,
&attested_header_state_root_res.unwrap()
)
}
fn is_next_committee_proof_valid(
attested_header: &Header,
next_committee: &mut SyncCommittee,
next_committee_branch: &Vec<Bytes32>
) -> bool {
let next_committee_hash_res = next_committee.hash_tree_root();
if next_committee_hash_res.is_err() {
return false;
}
let attested_header_state_root_res = bytes32_to_node(&attested_header.state_root);
if attested_header_state_root_res.is_err() {
return false;
}
let next_committee_branch_res = branch_to_nodes(next_committee_branch.clone());
if next_committee_branch_res.is_err() {
return false;
}
is_valid_merkle_branch(
&next_committee_hash_res.unwrap(),
next_committee_branch_res.unwrap().iter(),
5,
23,
&attested_header_state_root_res.unwrap()
)
}
fn is_current_committee_proof_valid(
attested_header: &Header,
current_committee: &mut SyncCommittee,
current_committee_branch: &Vec<Bytes32>
) -> bool {
let next_committee_hash_res = current_committee.hash_tree_root();
if next_committee_hash_res.is_err() {
return false;
}
let attested_header_state_root_res = bytes32_to_node(&attested_header.state_root);
if attested_header_state_root_res.is_err() {
return false;
}
let next_committee_branch_res = branch_to_nodes(current_committee_branch.clone());
if next_committee_branch_res.is_err() {
return false;
}
is_valid_merkle_branch(
&next_committee_hash_res.unwrap(),
next_committee_branch_res.unwrap().iter(),
5,
22,
&attested_header_state_root_res.unwrap()
)
}
fn calc_sync_period(slot: u64) -> u64 {
let epoch = slot / 32;
epoch / 256
}
fn branch_to_nodes(branch: Vec<Bytes32>) -> Result<Vec<Node>> {
branch.iter().map(|elem| bytes32_to_node(elem)).collect::<Result<Vec<Node>>>()
}
fn compute_committee_sign_root(header: Bytes32) -> Result<Node> {
let genesis_root = hex::decode("043db0d9a83813551ee2f33450d23797757d430911a9320530ad8a0eabc43efb")?.to_vec().try_into().unwrap();
let domain_type = &hex::decode("07000000")?[..];
let fork_version = Vector::from_iter(hex::decode("02001020").unwrap());
let domain = compute_domain(domain_type, fork_version, genesis_root)?;
compute_signing_root(header, domain)
}
#[derive(SimpleSerialize, Default, Debug)]
struct SigningData {
object_root: Bytes32,
domain: Bytes32
}
#[derive(SimpleSerialize, Default, Debug)]
struct ForkData {
current_version: Vector<u8, 4>,
genesis_validator_root: Bytes32,
}
fn compute_signing_root(object_root: Bytes32, domain: Bytes32) -> Result<Node> {
let mut data = SigningData { object_root, domain };
Ok(data.hash_tree_root()?)
}
fn compute_domain(domain_type: &[u8], fork_version: Vector<u8, 4>, genesis_root: Bytes32) -> Result<Bytes32> {
let fork_data_root = compute_fork_data_root(fork_version, genesis_root)?;
let start = domain_type;
let end = &fork_data_root.as_bytes()[..28];
let d = [start, end].concat();
Ok(d.to_vec().try_into().unwrap())
}
fn compute_fork_data_root(current_version: Vector<u8, 4>, genesis_validator_root: Bytes32) -> Result<Node> {
let current_version = current_version.try_into()?;
let mut fork_data = ForkData { current_version, genesis_validator_root };
Ok(fork_data.hash_tree_root()?)
}

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@ -21,11 +21,11 @@ pub fn verify_proof(proof: &Vec<Vec<u8>>, root: &Vec<u8>, path: &Vec<u8>, value:
// let state_root = hex_str_to_bytes("0x1d006918a3fef7ff7c843f20747c757a38a0a13fe7723f53e349f462c2cfdd71").unwrap(); // let state_root = hex_str_to_bytes("0x1d006918a3fef7ff7c843f20747c757a38a0a13fe7723f53e349f462c2cfdd71").unwrap();
// let path = keccak256(proof.address).to_vec(); // let path = keccak256(proof.address).to_vec();
let mut expected_hash = root; let mut expected_hash = root.clone();
let mut path_offset = 0; let mut path_offset = 0;
for (i, node) in proof.iter().enumerate() { for (i, node) in proof.iter().enumerate() {
if expected_hash != &keccak256(node).to_vec() { if expected_hash != keccak256(node).to_vec() {
return false; return false;
} }
@ -34,7 +34,7 @@ pub fn verify_proof(proof: &Vec<Vec<u8>>, root: &Vec<u8>, path: &Vec<u8>, value:
if node_list.len() == 17 { if node_list.len() == 17 {
let nibble = get_nibble(&path, path_offset); let nibble = get_nibble(&path, path_offset);
expected_hash = &node_list[nibble as usize].clone(); expected_hash = node_list[nibble as usize].clone();
path_offset += 1; path_offset += 1;
@ -44,7 +44,7 @@ pub fn verify_proof(proof: &Vec<Vec<u8>>, root: &Vec<u8>, path: &Vec<u8>, value:
return false; return false;
} }
} else { } else {
expected_hash = &node_list[1].clone(); expected_hash = node_list[1].clone();
} }
} else { } else {
return false; return false;

View File

@ -1,6 +1,6 @@
use eyre::Result; use eyre::Result;
use ssz_rs::{Node, Vector}; use ssz_rs::{Node, Vector};
use super::consensus_client::Bytes32; use super::consensus_rpc::Bytes32;
pub fn hex_str_to_bytes(s: &str) -> Result<Vec<u8>> { pub fn hex_str_to_bytes(s: &str) -> Result<Vec<u8>> {
let stripped = s.strip_prefix("0x").unwrap_or(s); let stripped = s.strip_prefix("0x").unwrap_or(s);