openethereum/secret-store/src/key_server_set.rs

// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.

// Parity Ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity Ethereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity Ethereum.  If not, see <http://www.gnu.org/licenses/>.

use bytes::Bytes;
use call_contract::CallContract;
use ethabi::FunctionOutputDecoder;
use ethcore::client::{BlockChainClient, BlockId, ChainNotify, Client, NewBlocks};
use ethereum_types::{Address, H256};
use ethkey::public_to_address;
use parking_lot::Mutex;
use std::{
    collections::{BTreeMap, HashSet},
    net::SocketAddr,
    sync::Arc,
};
use trusted_client::TrustedClient;
use types::{Error, NodeAddress, NodeId, Public};
use ContractAddress;
use NodeKeyPair;

use_contract!(key_server, "res/key_server_set.json");

/// Name of KeyServerSet contract in registry.
const KEY_SERVER_SET_CONTRACT_REGISTRY_NAME: &'static str = "secretstore_server_set";
/// Number of blocks (since latest new_set change) required before actually starting migration.
const MIGRATION_CONFIRMATIONS_REQUIRED: u64 = 5;
/// Number of blocks before the same-migration transaction (be it start or confirmation) will be retried.
const TRANSACTION_RETRY_INTERVAL_BLOCKS: u64 = 30;

#[derive(Default, Debug, Clone, PartialEq)]
/// Key Server Set state.
pub struct KeyServerSetSnapshot {
    /// Current set of key servers.
    pub current_set: BTreeMap<NodeId, SocketAddr>,
    /// New set of key servers.
    pub new_set: BTreeMap<NodeId, SocketAddr>,
    /// Current migration data.
    pub migration: Option<KeyServerSetMigration>,
}

#[derive(Default, Debug, Clone, PartialEq)]
/// Key server set migration.
pub struct KeyServerSetMigration {
    /// Migration id.
    pub id: H256,
    /// Migration set of key servers. It is the new_set at the moment of migration start.
    pub set: BTreeMap<NodeId, SocketAddr>,
    /// Master node of the migration process.
    pub master: NodeId,
    /// Is migration confirmed by this node?
    pub is_confirmed: bool,
}

/// Key Server Set
pub trait KeyServerSet: Send + Sync {
    /// Is this node currently isolated from the set?
    fn is_isolated(&self) -> bool;
    /// Get server set state.
    fn snapshot(&self) -> KeyServerSetSnapshot;
    /// Start migration.
    fn start_migration(&self, migration_id: H256);
    /// Confirm migration.
    fn confirm_migration(&self, migration_id: H256);
}

/// On-chain Key Server set implementation.
pub struct OnChainKeyServerSet {
    /// Cached on-chain contract.
    contract: Mutex<CachedContract>,
}

#[derive(Default, Debug, Clone, PartialEq)]
/// Non-finalized new_set.
struct FutureNewSet {
    /// New servers set.
    pub new_set: BTreeMap<NodeId, SocketAddr>,
    /// Hash of block, when this set has appeared for first time.
    pub block: H256,
}

#[derive(Default, Debug, Clone, PartialEq)]
/// Migration-related transaction information.
struct PreviousMigrationTransaction {
    /// Migration id.
    pub migration_id: H256,
    /// Latest actual block number at the time this transaction has been sent.
    pub block: u64,
}

/// Cached on-chain Key Server set contract.
struct CachedContract {
    /// Blockchain client.
    client: TrustedClient,
    /// Contract address source.
    contract_address_source: Option<ContractAddress>,
    /// Current contract address.
    contract_address: Option<Address>,
    /// Is auto-migrate enabled?
    auto_migrate_enabled: bool,
    /// Current contract state.
    snapshot: KeyServerSetSnapshot,
    /// Scheduled contract state (if any).
    future_new_set: Option<FutureNewSet>,
    /// Previous start migration transaction.
    start_migration_tx: Option<PreviousMigrationTransaction>,
    /// Previous confirm migration transaction.
    confirm_migration_tx: Option<PreviousMigrationTransaction>,
    /// This node key pair.
    self_key_pair: Arc<dyn NodeKeyPair>,
}

impl OnChainKeyServerSet {
    pub fn new(
        trusted_client: TrustedClient,
        contract_address_source: Option<ContractAddress>,
        self_key_pair: Arc<dyn NodeKeyPair>,
        auto_migrate_enabled: bool,
        key_servers: BTreeMap<Public, NodeAddress>,
    ) -> Result<Arc<Self>, Error> {
        let client = trusted_client.get_untrusted();
        let key_server_set = Arc::new(OnChainKeyServerSet {
            contract: Mutex::new(CachedContract::new(
                trusted_client,
                contract_address_source,
                self_key_pair,
                auto_migrate_enabled,
                key_servers,
            )?),
        });
        client
            .ok_or_else(|| {
                Error::Internal("Constructing OnChainKeyServerSet without active Client".into())
            })?
            .add_notify(key_server_set.clone());
        Ok(key_server_set)
    }
}

impl KeyServerSet for OnChainKeyServerSet {
    fn is_isolated(&self) -> bool {
        self.contract.lock().is_isolated()
    }

    fn snapshot(&self) -> KeyServerSetSnapshot {
        self.contract.lock().snapshot()
    }

    fn start_migration(&self, migration_id: H256) {
        self.contract.lock().start_migration(migration_id)
    }

    fn confirm_migration(&self, migration_id: H256) {
        self.contract.lock().confirm_migration(migration_id);
    }
}

impl ChainNotify for OnChainKeyServerSet {
    fn new_blocks(&self, new_blocks: NewBlocks) {
        if new_blocks.has_more_blocks_to_import {
            return;
        }
        let (enacted, retracted) = new_blocks.route.into_enacted_retracted();

        if !enacted.is_empty() || !retracted.is_empty() {
            self.contract.lock().update(enacted, retracted)
        }
    }
}

trait KeyServerSubset<F: Fn(Vec<u8>) -> Result<Vec<u8>, String>> {
    fn read_list(&self, f: &F) -> Result<Vec<Address>, String>;

    fn read_public(&self, address: Address, f: &F) -> Result<Bytes, String>;

    fn read_address(&self, address: Address, f: &F) -> Result<String, String>;
}

struct CurrentKeyServerSubset;

impl<F: Fn(Vec<u8>) -> Result<Vec<u8>, String>> KeyServerSubset<F> for CurrentKeyServerSubset {
    fn read_list(&self, f: &F) -> Result<Vec<Address>, String> {
        let (encoded, decoder) = key_server::functions::get_current_key_servers::call();
        decoder.decode(&f(encoded)?).map_err(|e| e.to_string())
    }

    fn read_public(&self, address: Address, f: &F) -> Result<Bytes, String> {
        let (encoded, decoder) =
            key_server::functions::get_current_key_server_public::call(address);
        decoder.decode(&f(encoded)?).map_err(|e| e.to_string())
    }

    fn read_address(&self, address: Address, f: &F) -> Result<String, String> {
        let (encoded, decoder) =
            key_server::functions::get_current_key_server_address::call(address);
        decoder.decode(&f(encoded)?).map_err(|e| e.to_string())
    }
}

struct MigrationKeyServerSubset;

impl<F: Fn(Vec<u8>) -> Result<Vec<u8>, String>> KeyServerSubset<F> for MigrationKeyServerSubset {
    fn read_list(&self, f: &F) -> Result<Vec<Address>, String> {
        let (encoded, decoder) = key_server::functions::get_migration_key_servers::call();
        decoder.decode(&f(encoded)?).map_err(|e| e.to_string())
    }

    fn read_public(&self, address: Address, f: &F) -> Result<Bytes, String> {
        let (encoded, decoder) =
            key_server::functions::get_migration_key_server_public::call(address);
        decoder.decode(&f(encoded)?).map_err(|e| e.to_string())
    }

    fn read_address(&self, address: Address, f: &F) -> Result<String, String> {
        let (encoded, decoder) =
            key_server::functions::get_migration_key_server_address::call(address);
        decoder.decode(&f(encoded)?).map_err(|e| e.to_string())
    }
}

struct NewKeyServerSubset;

impl<F: Fn(Vec<u8>) -> Result<Vec<u8>, String>> KeyServerSubset<F> for NewKeyServerSubset {
    fn read_list(&self, f: &F) -> Result<Vec<Address>, String> {
        let (encoded, decoder) = key_server::functions::get_new_key_servers::call();
        decoder.decode(&f(encoded)?).map_err(|e| e.to_string())
    }

    fn read_public(&self, address: Address, f: &F) -> Result<Bytes, String> {
        let (encoded, decoder) = key_server::functions::get_new_key_server_public::call(address);
        decoder.decode(&f(encoded)?).map_err(|e| e.to_string())
    }

    fn read_address(&self, address: Address, f: &F) -> Result<String, String> {
        let (encoded, decoder) = key_server::functions::get_new_key_server_address::call(address);
        decoder.decode(&f(encoded)?).map_err(|e| e.to_string())
    }
}

impl CachedContract {
    pub fn new(
        client: TrustedClient,
        contract_address_source: Option<ContractAddress>,
        self_key_pair: Arc<dyn NodeKeyPair>,
        auto_migrate_enabled: bool,
        key_servers: BTreeMap<Public, NodeAddress>,
    ) -> Result<Self, Error> {
        let server_set = match contract_address_source.is_none() {
            true => key_servers
                .into_iter()
                .map(|(p, addr)| {
                    let addr =
                        format!("{}:{}", addr.address, addr.port)
                            .parse()
                            .map_err(|err| {
                                Error::Internal(format!("error parsing node address: {}", err))
                            })?;
                    Ok((p, addr))
                })
                .collect::<Result<BTreeMap<_, _>, Error>>()?,
            false => Default::default(),
        };

        let mut contract = CachedContract {
            client: client,
            contract_address_source: contract_address_source,
            contract_address: None,
            auto_migrate_enabled: auto_migrate_enabled,
            future_new_set: None,
            confirm_migration_tx: None,
            start_migration_tx: None,
            snapshot: KeyServerSetSnapshot {
                current_set: server_set.clone(),
                new_set: server_set,
                ..Default::default()
            },
            self_key_pair: self_key_pair,
        };
        contract.update_contract_address();

        Ok(contract)
    }

    pub fn update_contract_address(&mut self) {
        if let Some(ref contract_address_source) = self.contract_address_source {
            let contract_address = self.client.read_contract_address(
                KEY_SERVER_SET_CONTRACT_REGISTRY_NAME.into(),
                contract_address_source,
            );
            if contract_address != self.contract_address {
                trace!(target: "secretstore", "{}: Configuring for key server set contract from address {:?}",
					self.self_key_pair.public(), contract_address);

                self.contract_address = contract_address;
            }
        }
    }

    pub fn update(&mut self, enacted: Vec<H256>, retracted: Vec<H256>) {
        // no need to update when servers set is hardcoded
        if self.contract_address_source.is_none() {
            return;
        }

        if let Some(client) = self.client.get() {
            // read new snapshot from reqistry (if something has chnaged)
            if !enacted.is_empty() || !retracted.is_empty() {
                self.update_contract_address();
                self.read_from_registry(&*client);
            }

            // update number of confirmations (if there's future new set)
            self.update_number_of_confirmations_if_required(&*client);
        }
    }

    fn is_isolated(&self) -> bool {
        !self
            .snapshot
            .current_set
            .contains_key(self.self_key_pair.public())
    }

    fn snapshot(&self) -> KeyServerSetSnapshot {
        self.snapshot.clone()
    }

    fn start_migration(&mut self, migration_id: H256) {
        // trust is not needed here, because it is the reaction to the read of the trusted client
        if let (Some(client), Some(contract_address)) =
            (self.client.get_untrusted(), self.contract_address.as_ref())
        {
            // check if we need to send start migration transaction
            if !update_last_transaction_block(&*client, &migration_id, &mut self.start_migration_tx)
            {
                return;
            }

            // prepare transaction data
            let transaction_data =
                key_server::functions::start_migration::encode_input(migration_id);

            // send transaction
            match self
                .client
                .transact_contract(*contract_address, transaction_data)
            {
                Ok(_) => {
                    trace!(target: "secretstore_net", "{}: sent auto-migration start transaction",
					self.self_key_pair.public())
                }
                Err(error) => {
                    warn!(target: "secretstore_net", "{}: failed to submit auto-migration start transaction: {}",
					self.self_key_pair.public(), error)
                }
            }
        }
    }

    fn confirm_migration(&mut self, migration_id: H256) {
        // trust is not needed here, because we have already completed the action
        if let (Some(client), Some(contract_address)) = (self.client.get(), self.contract_address) {
            // check if we need to send start migration transaction
            if !update_last_transaction_block(
                &*client,
                &migration_id,
                &mut self.confirm_migration_tx,
            ) {
                return;
            }

            // prepare transaction data
            let transaction_data =
                key_server::functions::confirm_migration::encode_input(migration_id);

            // send transaction
            match self
                .client
                .transact_contract(contract_address, transaction_data)
            {
                Ok(_) => {
                    trace!(target: "secretstore_net", "{}: sent auto-migration confirm transaction",
					self.self_key_pair.public())
                }
                Err(error) => {
                    warn!(target: "secretstore_net", "{}: failed to submit auto-migration confirmation transaction: {}",
					self.self_key_pair.public(), error)
                }
            }
        }
    }

    fn read_from_registry(&mut self, client: &Client) {
        let contract_address = match self.contract_address {
            Some(contract_address) => contract_address,
            None => {
                // no contract installed => empty snapshot
                // WARNING: after restart current_set will be reset to the set from configuration file
                // even though we have reset to empty set here. We are not considering this as an issue
                // because it is actually the issue of administrator.
                self.snapshot = Default::default();
                self.future_new_set = None;
                return;
            }
        };

        let do_call = |data| client.call_contract(BlockId::Latest, contract_address, data);

        let current_set = Self::read_key_server_set(CurrentKeyServerSubset, &do_call);

        // read migration-related data if auto migration is enabled
        let (new_set, migration) = match self.auto_migrate_enabled {
            true => {
                let new_set = Self::read_key_server_set(NewKeyServerSubset, &do_call);
                let migration_set = Self::read_key_server_set(MigrationKeyServerSubset, &do_call);

                let migration_id = match migration_set.is_empty() {
                    false => {
                        let (encoded, decoder) = key_server::functions::get_migration_id::call();
                        do_call(encoded)
							.map_err(|e| e.to_string())
							.and_then(|data| decoder.decode(&data).map_err(|e| e.to_string()))
							.map_err(|err| { trace!(target: "secretstore", "Error {} reading migration id from contract", err); err })
							.ok()
                    }
                    true => None,
                };

                let migration_master = match migration_set.is_empty() {
                    false => {
                        let (encoded, decoder) =
                            key_server::functions::get_migration_master::call();
                        do_call(encoded)
							.map_err(|e| e.to_string())
							.and_then(|data| decoder.decode(&data).map_err(|e| e.to_string()))
							.map_err(|err| { trace!(target: "secretstore", "Error {} reading migration master from contract", err); err })
							.ok()
							.and_then(|address| current_set.keys().chain(migration_set.keys())
								.find(|public| public_to_address(public) == address)
								.cloned())
                    }
                    true => None,
                };

                let is_migration_confirmed = match migration_set.is_empty() {
                    false
                        if current_set.contains_key(self.self_key_pair.public())
                            || migration_set.contains_key(self.self_key_pair.public()) =>
                    {
                        let (encoded, decoder) =
                            key_server::functions::is_migration_confirmed::call(
                                self.self_key_pair.address(),
                            );
                        do_call(encoded)
							.map_err(|e| e.to_string())
							.and_then(|data| decoder.decode(&data).map_err(|e| e.to_string()))
							.map_err(|err| { trace!(target: "secretstore", "Error {} reading migration confirmation from contract", err); err })
							.ok()
                    }
                    _ => None,
                };

                let migration = match (
                    migration_set.is_empty(),
                    migration_id,
                    migration_master,
                    is_migration_confirmed,
                ) {
                    (
                        false,
                        Some(migration_id),
                        Some(migration_master),
                        Some(is_migration_confirmed),
                    ) => Some(KeyServerSetMigration {
                        id: migration_id,
                        master: migration_master,
                        set: migration_set,
                        is_confirmed: is_migration_confirmed,
                    }),
                    _ => None,
                };

                (new_set, migration)
            }
            false => (current_set.clone(), None),
        };

        let mut new_snapshot = KeyServerSetSnapshot {
            current_set: current_set,
            new_set: new_set,
            migration: migration,
        };

        // we might want to adjust new_set if auto migration is enabled
        if self.auto_migrate_enabled {
            let block = client.block_hash(BlockId::Latest).unwrap_or_default();
            update_future_set(&mut self.future_new_set, &mut new_snapshot, block);
        }

        self.snapshot = new_snapshot;
    }

    fn read_key_server_set<T, F>(subset: T, do_call: F) -> BTreeMap<Public, SocketAddr>
    where
        T: KeyServerSubset<F>,
        F: Fn(Vec<u8>) -> Result<Vec<u8>, String>,
    {
        let mut key_servers = BTreeMap::new();
        let mut key_servers_addresses = HashSet::new();
        let key_servers_list = subset.read_list(&do_call)
			.map_err(|err| { warn!(target: "secretstore_net", "error {} reading list of key servers from contract", err); err })
			.unwrap_or_default();
        for key_server in key_servers_list {
            let key_server_public = subset.read_public(key_server, &do_call).and_then(|p| {
                if p.len() == 64 {
                    Ok(Public::from_slice(&p))
                } else {
                    Err(format!("Invalid public length {}", p.len()))
                }
            });
            let key_server_address: Result<SocketAddr, _> = subset
                .read_address(key_server, &do_call)
                .and_then(|a| a.parse().map_err(|e| format!("Invalid ip address: {}", e)));

            // only add successfully parsed nodes
            match (key_server_public, key_server_address) {
                (Ok(key_server_public), Ok(key_server_address)) => {
                    if !key_servers_addresses.insert(key_server_address.clone()) {
                        warn!(target: "secretstore_net", "the same address ({}) specified twice in list of contracts. Ignoring server {}",
							key_server_address, key_server_public);
                        continue;
                    }

                    key_servers.insert(key_server_public, key_server_address);
                }
                (Err(public_err), _) => {
                    warn!(target: "secretstore_net", "received invalid public from key server set contract: {}", public_err)
                }
                (_, Err(ip_err)) => {
                    warn!(target: "secretstore_net", "received invalid IP from key server set contract: {}", ip_err)
                }
            }
        }
        key_servers
    }

    fn update_number_of_confirmations_if_required(&mut self, client: &dyn BlockChainClient) {
        if !self.auto_migrate_enabled {
            return;
        }

        update_number_of_confirmations(
            &|| latest_block_hash(&*client),
            &|block| block_confirmations(&*client, block),
            &mut self.future_new_set,
            &mut self.snapshot,
        );
    }
}

/// Check if two sets are equal (in terms of migration requirements). We do not need migration if only
/// addresses are changed - simply adjusting connections is enough in this case.
pub fn is_migration_required(
    current_set: &BTreeMap<NodeId, SocketAddr>,
    new_set: &BTreeMap<NodeId, SocketAddr>,
) -> bool {
    let no_nodes_removed = current_set.keys().all(|n| new_set.contains_key(n));
    let no_nodes_added = new_set.keys().all(|n| current_set.contains_key(n));
    !no_nodes_removed || !no_nodes_added
}

fn update_future_set(
    future_new_set: &mut Option<FutureNewSet>,
    new_snapshot: &mut KeyServerSetSnapshot,
    block: H256,
) {
    // migration has already started => no need to delay visibility
    if new_snapshot.migration.is_some() {
        *future_new_set = None;
        return;
    }

    // no migration is required => no need to delay visibility
    if !is_migration_required(&new_snapshot.current_set, &new_snapshot.new_set) {
        *future_new_set = None;
        return;
    }

    // when auto-migrate is enabled, we do not want to start migration right after new_set is changed, because of:
    // 1) there could be a fork && we could start migration to forked version (and potentially lose secrets)
    // 2) there must be some period for new_set changes finalization (i.e. adding/removing more servers)
    let mut new_set = new_snapshot.current_set.clone();
    ::std::mem::swap(&mut new_set, &mut new_snapshot.new_set);

    // if nothing has changed in future_new_set, then we want to preserve previous block hash
    let block = match Some(&new_set) == future_new_set.as_ref().map(|f| &f.new_set) {
        true => future_new_set
            .as_ref()
            .map(|f| &f.block)
            .cloned()
            .unwrap_or_else(|| block),
        false => block,
    };

    *future_new_set = Some(FutureNewSet {
        new_set: new_set,
        block: block,
    });
}

fn update_number_of_confirmations<F1: Fn() -> H256, F2: Fn(H256) -> Option<u64>>(
    latest_block: &F1,
    confirmations: &F2,
    future_new_set: &mut Option<FutureNewSet>,
    snapshot: &mut KeyServerSetSnapshot,
) {
    match future_new_set.as_mut() {
        // no future new set is scheduled => do nothing,
        None => return,
        // else we should calculate number of confirmations for future new set
        Some(future_new_set) => match confirmations(future_new_set.block.clone()) {
            // we have enough confirmations => should move new_set from future to snapshot
            Some(confirmations) if confirmations >= MIGRATION_CONFIRMATIONS_REQUIRED => (),
            // not enough confirmations => do nothing
            Some(_) => return,
            // if number of confirmations is None, then reorg has happened && we need to reset block
            // (some more intelligent strategy is possible, but let's stick to simplest one)
            None => {
                future_new_set.block = latest_block();
                return;
            }
        },
    }

    let future_new_set = future_new_set
        .take()
        .expect("we only pass through match above when future_new_set is some; qed");
    snapshot.new_set = future_new_set.new_set;
}

fn update_last_transaction_block(
    client: &Client,
    migration_id: &H256,
    previous_transaction: &mut Option<PreviousMigrationTransaction>,
) -> bool {
    let last_block = client.block_number(BlockId::Latest).unwrap_or_default();
    match previous_transaction.as_ref() {
        // no previous transaction => send immediately
        None => (),
        // previous transaction has been sent for other migration process => send immediately
        Some(tx) if tx.migration_id != *migration_id => (),
        // if we have sent the same type of transaction recently => do nothing (hope it will be mined eventually)
        // if we have sent the same transaction some time ago =>
        //   assume that our tx queue was full
        //   or we didn't have enough eth fot this tx
        //   or the transaction has been removed from the queue (and never reached any miner node)
        // if we have restarted after sending tx => assume we have never sent it
        Some(tx) => {
            if tx.block > last_block || last_block - tx.block < TRANSACTION_RETRY_INTERVAL_BLOCKS {
                return false;
            }
        }
    }

    *previous_transaction = Some(PreviousMigrationTransaction {
        migration_id: migration_id.clone(),
        block: last_block,
    });

    true
}

fn latest_block_hash(client: &dyn BlockChainClient) -> H256 {
    client.block_hash(BlockId::Latest).unwrap_or_default()
}

fn block_confirmations(client: &dyn BlockChainClient, block: H256) -> Option<u64> {
    client
        .block_number(BlockId::Hash(block))
        .and_then(|block| {
            client
                .block_number(BlockId::Latest)
                .map(|last_block| (block, last_block))
        })
        .map(|(block, last_block)| last_block - block)
}

#[cfg(test)]
pub mod tests {
    use super::{
        update_future_set, update_number_of_confirmations, FutureNewSet, KeyServerSet,
        KeyServerSetSnapshot, MIGRATION_CONFIRMATIONS_REQUIRED,
    };
    use ethereum_types::H256;
    use ethkey::Public;
    use std::{collections::BTreeMap, net::SocketAddr};

    #[derive(Default)]
    pub struct MapKeyServerSet {
        is_isolated: bool,
        nodes: BTreeMap<Public, SocketAddr>,
    }

    impl MapKeyServerSet {
        pub fn new(is_isolated: bool, nodes: BTreeMap<Public, SocketAddr>) -> Self {
            MapKeyServerSet {
                is_isolated: is_isolated,
                nodes: nodes,
            }
        }
    }

    impl KeyServerSet for MapKeyServerSet {
        fn is_isolated(&self) -> bool {
            self.is_isolated
        }

        fn snapshot(&self) -> KeyServerSetSnapshot {
            KeyServerSetSnapshot {
                current_set: self.nodes.clone(),
                new_set: self.nodes.clone(),
                ..Default::default()
            }
        }

        fn start_migration(&self, _migration_id: H256) {
            unimplemented!("test-only")
        }

        fn confirm_migration(&self, _migration_id: H256) {
            unimplemented!("test-only")
        }
    }

    #[test]
    fn future_set_is_updated_to_none_when_migration_has_already_started() {
        let mut future_new_set = Some(Default::default());
        let mut new_snapshot = KeyServerSetSnapshot {
            migration: Some(Default::default()),
            ..Default::default()
        };
        let new_snapshot_copy = new_snapshot.clone();
        update_future_set(&mut future_new_set, &mut new_snapshot, Default::default());
        assert_eq!(future_new_set, None);
        assert_eq!(new_snapshot, new_snapshot_copy);
    }

    #[test]
    fn future_set_is_updated_to_none_when_no_migration_is_required() {
        let node_id = Default::default();
        let address1 = "127.0.0.1:12000".parse().unwrap();
        let address2 = "127.0.0.1:12001".parse().unwrap();

        // addresses are different, but node set is the same => no migration is required
        let mut future_new_set = Some(Default::default());
        let mut new_snapshot = KeyServerSetSnapshot {
            current_set: vec![(node_id, address1)].into_iter().collect(),
            new_set: vec![(node_id, address2)].into_iter().collect(),
            ..Default::default()
        };
        let new_snapshot_copy = new_snapshot.clone();
        update_future_set(&mut future_new_set, &mut new_snapshot, Default::default());
        assert_eq!(future_new_set, None);
        assert_eq!(new_snapshot, new_snapshot_copy);

        // everything is the same => no migration is required
        let mut future_new_set = Some(Default::default());
        let mut new_snapshot = KeyServerSetSnapshot {
            current_set: vec![(node_id, address1)].into_iter().collect(),
            new_set: vec![(node_id, address1)].into_iter().collect(),
            ..Default::default()
        };
        let new_snapshot_copy = new_snapshot.clone();
        update_future_set(&mut future_new_set, &mut new_snapshot, Default::default());
        assert_eq!(future_new_set, None);
        assert_eq!(new_snapshot, new_snapshot_copy);
    }

    #[test]
    fn future_set_is_initialized() {
        let address = "127.0.0.1:12000".parse().unwrap();

        let mut future_new_set = None;
        let mut new_snapshot = KeyServerSetSnapshot {
            current_set: vec![(1.into(), address)].into_iter().collect(),
            new_set: vec![(2.into(), address)].into_iter().collect(),
            ..Default::default()
        };
        update_future_set(&mut future_new_set, &mut new_snapshot, Default::default());
        assert_eq!(
            future_new_set,
            Some(FutureNewSet {
                new_set: vec![(2.into(), address)].into_iter().collect(),
                block: Default::default(),
            })
        );
        assert_eq!(
            new_snapshot,
            KeyServerSetSnapshot {
                current_set: vec![(1.into(), address)].into_iter().collect(),
                new_set: vec![(1.into(), address)].into_iter().collect(),
                ..Default::default()
            }
        );
    }

    #[test]
    fn future_set_is_updated_when_set_differs() {
        let address = "127.0.0.1:12000".parse().unwrap();

        let mut future_new_set = Some(FutureNewSet {
            new_set: vec![(2.into(), address)].into_iter().collect(),
            block: Default::default(),
        });
        let mut new_snapshot = KeyServerSetSnapshot {
            current_set: vec![(1.into(), address)].into_iter().collect(),
            new_set: vec![(3.into(), address)].into_iter().collect(),
            ..Default::default()
        };
        update_future_set(&mut future_new_set, &mut new_snapshot, 1.into());
        assert_eq!(
            future_new_set,
            Some(FutureNewSet {
                new_set: vec![(3.into(), address)].into_iter().collect(),
                block: 1.into(),
            })
        );
        assert_eq!(
            new_snapshot,
            KeyServerSetSnapshot {
                current_set: vec![(1.into(), address)].into_iter().collect(),
                new_set: vec![(1.into(), address)].into_iter().collect(),
                ..Default::default()
            }
        );
    }

    #[test]
    fn future_set_is_not_updated_when_set_is_the_same() {
        let address = "127.0.0.1:12000".parse().unwrap();

        let mut future_new_set = Some(FutureNewSet {
            new_set: vec![(2.into(), address)].into_iter().collect(),
            block: Default::default(),
        });
        let mut new_snapshot = KeyServerSetSnapshot {
            current_set: vec![(1.into(), address)].into_iter().collect(),
            new_set: vec![(2.into(), address)].into_iter().collect(),
            ..Default::default()
        };
        update_future_set(&mut future_new_set, &mut new_snapshot, 1.into());
        assert_eq!(
            future_new_set,
            Some(FutureNewSet {
                new_set: vec![(2.into(), address)].into_iter().collect(),
                block: Default::default(),
            })
        );
        assert_eq!(
            new_snapshot,
            KeyServerSetSnapshot {
                current_set: vec![(1.into(), address)].into_iter().collect(),
                new_set: vec![(1.into(), address)].into_iter().collect(),
                ..Default::default()
            }
        );
    }

    #[test]
    fn when_updating_confirmations_nothing_is_changed_if_no_future_set() {
        let address = "127.0.0.1:12000".parse().unwrap();

        let mut future_new_set = None;
        let mut snapshot = KeyServerSetSnapshot {
            current_set: vec![(1.into(), address)].into_iter().collect(),
            new_set: vec![(1.into(), address)].into_iter().collect(),
            ..Default::default()
        };
        let snapshot_copy = snapshot.clone();
        update_number_of_confirmations(
            &|| 1.into(),
            &|_| Some(MIGRATION_CONFIRMATIONS_REQUIRED),
            &mut future_new_set,
            &mut snapshot,
        );
        assert_eq!(future_new_set, None);
        assert_eq!(snapshot, snapshot_copy);
    }

    #[test]
    fn when_updating_confirmations_migration_is_scheduled() {
        let address = "127.0.0.1:12000".parse().unwrap();

        let mut future_new_set = Some(FutureNewSet {
            new_set: vec![(2.into(), address)].into_iter().collect(),
            block: Default::default(),
        });
        let mut snapshot = KeyServerSetSnapshot {
            current_set: vec![(1.into(), address)].into_iter().collect(),
            new_set: vec![(1.into(), address)].into_iter().collect(),
            ..Default::default()
        };
        update_number_of_confirmations(
            &|| 1.into(),
            &|_| Some(MIGRATION_CONFIRMATIONS_REQUIRED),
            &mut future_new_set,
            &mut snapshot,
        );
        assert_eq!(future_new_set, None);
        assert_eq!(
            snapshot,
            KeyServerSetSnapshot {
                current_set: vec![(1.into(), address)].into_iter().collect(),
                new_set: vec![(2.into(), address)].into_iter().collect(),
                ..Default::default()
            }
        );
    }

    #[test]
    fn when_updating_confirmations_migration_is_not_scheduled_when_not_enough_confirmations() {
        let address = "127.0.0.1:12000".parse().unwrap();

        let mut future_new_set = Some(FutureNewSet {
            new_set: vec![(2.into(), address)].into_iter().collect(),
            block: Default::default(),
        });
        let mut snapshot = KeyServerSetSnapshot {
            current_set: vec![(1.into(), address)].into_iter().collect(),
            new_set: vec![(1.into(), address)].into_iter().collect(),
            ..Default::default()
        };
        let future_new_set_copy = future_new_set.clone();
        let snapshot_copy = snapshot.clone();
        update_number_of_confirmations(
            &|| 1.into(),
            &|_| Some(MIGRATION_CONFIRMATIONS_REQUIRED - 1),
            &mut future_new_set,
            &mut snapshot,
        );
        assert_eq!(future_new_set, future_new_set_copy);
        assert_eq!(snapshot, snapshot_copy);
    }

    #[test]
    fn when_updating_confirmations_migration_is_reset_when_reorganized() {
        let address = "127.0.0.1:12000".parse().unwrap();

        let mut future_new_set = Some(FutureNewSet {
            new_set: vec![(2.into(), address)].into_iter().collect(),
            block: 1.into(),
        });
        let mut snapshot = KeyServerSetSnapshot {
            current_set: vec![(1.into(), address)].into_iter().collect(),
            new_set: vec![(1.into(), address)].into_iter().collect(),
            ..Default::default()
        };
        let snapshot_copy = snapshot.clone();
        update_number_of_confirmations(&|| 2.into(), &|_| None, &mut future_new_set, &mut snapshot);
        assert_eq!(
            future_new_set,
            Some(FutureNewSet {
                new_set: vec![(2.into(), address)].into_iter().collect(),
                block: 2.into(),
            })
        );
        assert_eq!(snapshot, snapshot_copy);
    }
}