462 lines
18 KiB
Nim
462 lines
18 KiB
Nim
# beacon_chain
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# Copyright (c) 2018-2019 Status Research & Development GmbH
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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# State transition - block processing, as described in
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# https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#beacon-chain-state-transition-function
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#
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# The purpose of this code right is primarily educational, to help piece
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# together the mechanics of the beacon state and to discover potential problem
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# areas.
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#
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# The entry point is `process_block` which is at the bottom of this file.
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#
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# General notes about the code (TODO):
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# * It's inefficient - we quadratically copy, allocate and iterate when there
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# are faster options
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# * Weird styling - the sections taken from the spec use python styling while
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# the others use NEP-1 - helps grepping identifiers in spec
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# * We mix procedural and functional styles for no good reason, except that the
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# spec does so also.
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# * There are likely lots of bugs.
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# * For indices, we get a mix of uint64, ValidatorIndex and int - this is currently
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# swept under the rug with casts
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# * The spec uses uint64 for data types, but functions in the spec often assume
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# signed bigint semantics - under- and overflows ensue
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# * Sane error handling is missing in most cases (yay, we'll get the chance to
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# debate exceptions again!)
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# When updating the code, add TODO sections to mark where there are clear
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# improvements to be made - other than that, keep things similar to spec for
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# now.
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import # TODO - cleanup imports
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algorithm, collections/sets, chronicles, math, options, sequtils, sets, tables,
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../extras, ../ssz, ../beacon_node_types,
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beaconstate, bitfield, crypto, datatypes, digest, helpers, validator
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# https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#block-header
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proc processBlockHeader(
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state: var BeaconState, blck: BeaconBlock, flags: UpdateFlags,
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stateCache: var StateCache): bool =
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# Verify that the slots match
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if not (blck.slot == state.slot):
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notice "Block header: slot mismatch",
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block_slot = humaneSlotNum(blck.slot),
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state_slot = humaneSlotNum(state.slot)
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return false
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# Verify that the parent matches
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if skipValidation notin flags and not (blck.parent_root ==
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signing_root(state.latest_block_header)):
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notice "Block header: previous block root mismatch",
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latest_block_header = state.latest_block_header,
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blck = shortLog(blck),
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latest_block_header_root = shortLog(signing_root(state.latest_block_header))
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return false
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# Save current block as the new latest block
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state.latest_block_header = BeaconBlockHeader(
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slot: blck.slot,
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parent_root: blck.parent_root,
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body_root: hash_tree_root(blck.body),
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)
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# Verify proposer is not slashed
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let proposer =
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state.validator_registry[get_beacon_proposer_index(state, stateCache)]
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if proposer.slashed:
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notice "Block header: proposer slashed"
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return false
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# Verify proposer signature
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if skipValidation notin flags and not bls_verify(
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proposer.pubkey,
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signing_root(blck).data,
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blck.signature,
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get_domain(state, DOMAIN_BEACON_PROPOSER)):
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notice "Block header: invalid block header",
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proposer_pubkey = proposer.pubkey,
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block_root = shortLog(signing_root(blck)),
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block_signature = blck.signature
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return false
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true
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# https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#randao
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proc processRandao(
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state: var BeaconState, body: BeaconBlockBody, flags: UpdateFlags,
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stateCache: var StateCache): bool =
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let
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proposer_index = get_beacon_proposer_index(state, stateCache)
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proposer = addr state.validator_registry[proposer_index]
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# Verify that the provided randao value is valid
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if skipValidation notin flags:
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if not bls_verify(
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proposer.pubkey,
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hash_tree_root(get_current_epoch(state).uint64).data,
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body.randao_reveal,
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get_domain(state, DOMAIN_RANDAO)):
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notice "Randao mismatch", proposer_pubkey = proposer.pubkey,
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message = get_current_epoch(state),
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signature = body.randao_reveal,
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slot = state.slot
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return false
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# Mix it in
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let
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mix = get_current_epoch(state) mod LATEST_RANDAO_MIXES_LENGTH
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rr = eth2hash(body.randao_reveal.getBytes()).data
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for i, b in state.latest_randao_mixes[mix].data:
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state.latest_randao_mixes[mix].data[i] = b xor rr[i]
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true
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# https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#eth1-data
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func processEth1Data(state: var BeaconState, body: BeaconBlockBody) =
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state.eth1_data_votes.add body.eth1_data
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if state.eth1_data_votes.count(body.eth1_data) * 2 >
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SLOTS_PER_ETH1_VOTING_PERIOD:
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state.latest_eth1_data = body.eth1_data
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# https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#is_slashable_validator
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func is_slashable_validator(validator: Validator, epoch: Epoch): bool =
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# Check if ``validator`` is slashable.
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(not validator.slashed) and
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(validator.activation_epoch <= epoch) and
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(epoch < validator.withdrawable_epoch)
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# https://github.com/ethereum/eth2.0-specs/blob/v0.6.3/specs/core/0_beacon-chain.md#proposer-slashings
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proc processProposerSlashings(
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state: var BeaconState, blck: BeaconBlock, flags: UpdateFlags,
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stateCache: var StateCache): bool =
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if len(blck.body.proposer_slashings) > MAX_PROPOSER_SLASHINGS:
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notice "PropSlash: too many!",
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proposer_slashings = len(blck.body.proposer_slashings)
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return false
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for proposer_slashing in blck.body.proposer_slashings:
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let proposer = state.validator_registry[proposer_slashing.proposer_index.int]
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# Verify that the epoch is the same
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if not (slot_to_epoch(proposer_slashing.header_1.slot) ==
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slot_to_epoch(proposer_slashing.header_2.slot)):
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notice "PropSlash: epoch mismatch"
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return false
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# But the headers are different
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if not (proposer_slashing.header_1 != proposer_slashing.header_2):
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notice "PropSlash: headers not different"
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return false
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# Check proposer is slashable
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if not is_slashable_validator(proposer, get_current_epoch(state)):
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notice "PropSlash: slashed proposer"
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return false
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# Signatures are valid
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if skipValidation notin flags:
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for i, header in @[proposer_slashing.header_1, proposer_slashing.header_2]:
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if not bls_verify(
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proposer.pubkey,
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signing_root(header).data,
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header.signature,
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get_domain(
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state, DOMAIN_BEACON_PROPOSER, slot_to_epoch(header.slot))):
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notice "PropSlash: invalid signature",
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signature_index = i
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return false
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slashValidator(
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state, proposer_slashing.proposer_index.ValidatorIndex, stateCache)
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true
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# https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#is_slashable_attestation_data
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func is_slashable_attestation_data(
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data_1: AttestationData, data_2: AttestationData): bool =
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## Check if ``data_1`` and ``data_2`` are slashable according to Casper FFG
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## rules.
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# Double vote
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(data_1 != data_2 and data_1.target_epoch == data_2.target_epoch) or
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# Surround vote
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(data_1.source_epoch < data_2.source_epoch and
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data_2.target_epoch < data_1.target_epoch)
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# https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#attester-slashings
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proc processAttesterSlashings(state: var BeaconState, blck: BeaconBlock,
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stateCache: var StateCache): bool =
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# Process ``AttesterSlashing`` operation.
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if len(blck.body.attester_slashings) > MAX_ATTESTER_SLASHINGS:
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notice "CaspSlash: too many!"
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return false
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result = true
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for attester_slashing in blck.body.attester_slashings:
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let
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attestation_1 = attester_slashing.attestation_1
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attestation_2 = attester_slashing.attestation_2
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if not is_slashable_attestation_data(
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attestation_1.data, attestation_2.data):
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notice "CaspSlash: surround or double vote check failed"
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return false
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if not validate_indexed_attestation(state, attestation_1):
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notice "CaspSlash: invalid votes 1"
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return false
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if not validate_indexed_attestation(state, attestation_2):
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notice "CaspSlash: invalid votes 2"
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return false
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var slashed_any = false
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## TODO there's a lot of sorting/set construction here and
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## verify_indexed_attestation, but go by spec unless there
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## is compelling perf evidence otherwise.
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let attesting_indices_1 =
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attestation_1.custody_bit_0_indices & attestation_1.custody_bit_1_indices
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let attesting_indices_2 =
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attestation_2.custody_bit_0_indices & attestation_2.custody_bit_1_indices
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for index in sorted(toSeq(intersection(toSet(attesting_indices_1),
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toSet(attesting_indices_2)).items), system.cmp):
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if is_slashable_validator(state.validator_registry[index.int],
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get_current_epoch(state)):
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slash_validator(state, index.ValidatorIndex, stateCache)
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slashed_any = true
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result = result and slashed_any
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# https://github.com/ethereum/eth2.0-specs/blob/v0.6.3/specs/core/0_beacon-chain.md#attestations
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proc processAttestations(
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state: var BeaconState, blck: BeaconBlock, flags: UpdateFlags,
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stateCache: var StateCache): bool =
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## Each block includes a number of attestations that the proposer chose. Each
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## attestation represents an update to a specific shard and is signed by a
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## committee of validators.
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## Here we make sanity checks for each attestation and it to the state - most
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## updates will happen at the epoch boundary where state updates happen in
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## bulk.
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if blck.body.attestations.len > MAX_ATTESTATIONS:
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notice "Attestation: too many!", attestations = blck.body.attestations.len
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return false
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if not blck.body.attestations.allIt(checkAttestation(state, it, flags, stateCache)):
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return false
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# All checks passed - update state
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# Apply the attestations
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var committee_count_cache = initTable[Epoch, uint64]()
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for attestation in blck.body.attestations:
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# Caching
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let
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epoch = attestation.data.target_epoch
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committee_count = if epoch in committee_count_cache:
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committee_count_cache[epoch]
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else:
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get_epoch_committee_count(state, epoch)
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committee_count_cache[epoch] = committee_count
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# Spec content
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let attestation_slot =
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get_attestation_data_slot(state, attestation.data, committee_count)
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let pending_attestation = PendingAttestation(
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data: attestation.data,
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aggregation_bitfield: attestation.aggregation_bitfield,
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inclusion_delay: state.slot - attestation_slot,
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proposer_index: get_beacon_proposer_index(state, stateCache),
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)
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if attestation.data.target_epoch == get_current_epoch(state):
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state.current_epoch_attestations.add(pending_attestation)
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else:
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state.previous_epoch_attestations.add(pending_attestation)
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true
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# https://github.com/ethereum/eth2.0-specs/blob/v0.5.1/specs/core/0_beacon-chain.md#deposits
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proc processDeposits(state: var BeaconState, blck: BeaconBlock): bool =
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if not (len(blck.body.deposits) <= MAX_DEPOSITS):
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notice "processDeposits: too many deposits"
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return false
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for deposit in blck.body.deposits:
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if not process_deposit(state, deposit):
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notice "processDeposits: deposit invalid"
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return false
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true
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# https://github.com/ethereum/eth2.0-specs/blob/v0.6.3/specs/core/0_beacon-chain.md#voluntary-exits
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proc processVoluntaryExits(
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state: var BeaconState, blck: BeaconBlock, flags: UpdateFlags): bool =
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# Process ``VoluntaryExit`` transaction.
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if len(blck.body.voluntary_exits) > MAX_VOLUNTARY_EXITS:
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notice "Exit: too many!"
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return false
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for exit in blck.body.voluntary_exits:
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let validator = state.validator_registry[exit.validator_index.int]
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# Verify the validator is active
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if not is_active_validator(validator, get_current_epoch(state)):
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notice "Exit: validator not active"
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return false
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# Verify the validator has not yet exited
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if not (validator.exit_epoch == FAR_FUTURE_EPOCH):
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notice "Exit: validator has exited"
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return false
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## Exits must specify an epoch when they become valid; they are not valid
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## before then
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if not (get_current_epoch(state) >= exit.epoch):
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notice "Exit: exit epoch not passed"
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return false
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# Verify the validator has been active long enough
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# TODO detect underflow
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if not (get_current_epoch(state) - validator.activation_epoch >=
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PERSISTENT_COMMITTEE_PERIOD):
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notice "Exit: not in validator set long enough"
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return false
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# Verify signature
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if skipValidation notin flags:
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if not bls_verify(
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validator.pubkey, signing_root(exit).data, exit.signature,
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get_domain(state, DOMAIN_VOLUNTARY_EXIT, exit.epoch)):
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notice "Exit: invalid signature"
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return false
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# Initiate exit
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initiate_validator_exit(state, exit.validator_index.ValidatorIndex)
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true
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# https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#transfers
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proc processTransfers(state: var BeaconState, blck: BeaconBlock,
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flags: UpdateFlags, stateCache: var StateCache): bool =
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if not (len(blck.body.transfers) <= MAX_TRANSFERS):
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notice "Transfer: too many transfers"
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return false
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for transfer in blck.body.transfers:
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let sender_balance = state.balances[transfer.sender.int]
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## Verify the amount and fee are not individually too big (for anti-overflow
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## purposes)
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if not (sender_balance >= max(transfer.amount, transfer.fee)):
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notice "Transfer: sender balance too low for transfer amount or fee"
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return false
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# A transfer is valid in only one slot
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if not (state.slot == transfer.slot):
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notice "Transfer: slot mismatch"
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return false
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## Sender must be not yet eligible for activation, withdrawn, or transfer
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## balance over MAX_EFFECTIVE_BALANCE
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if not (
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state.validator_registry[transfer.sender.int].activation_epoch ==
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FAR_FUTURE_EPOCH or
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get_current_epoch(state) >=
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state.validator_registry[
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transfer.sender.int].withdrawable_epoch or
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transfer.amount + transfer.fee + MAX_EFFECTIVE_BALANCE <=
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state.balances[transfer.sender.int]):
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notice "Transfer: only withdrawn or not-activated accounts with sufficient balance can transfer"
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return false
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# Verify that the pubkey is valid
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let wc = state.validator_registry[transfer.sender.int].
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withdrawal_credentials
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if not (wc.data[0] == BLS_WITHDRAWAL_PREFIX and
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wc.data[1..^1] == eth2hash(transfer.pubkey.getBytes).data[1..^1]):
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notice "Transfer: incorrect withdrawal credentials"
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return false
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# Verify that the signature is valid
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if skipValidation notin flags:
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if not bls_verify(
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transfer.pubkey, signing_root(transfer).data, transfer.signature,
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get_domain(state, DOMAIN_TRANSFER)):
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notice "Transfer: incorrect signature"
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return false
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# Process the transfer
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decrease_balance(
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state, transfer.sender.ValidatorIndex, transfer.amount + transfer.fee)
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increase_balance(
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state, transfer.recipient.ValidatorIndex, transfer.amount)
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increase_balance(
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state, get_beacon_proposer_index(state, stateCache), transfer.fee)
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# Verify balances are not dust
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if not (
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0'u64 < state.balances[transfer.sender.int] and
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state.balances[transfer.sender.int] < MIN_DEPOSIT_AMOUNT):
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notice "Transfer: sender balance too low for transfer amount or fee"
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return false
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if not (
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0'u64 < state.balances[transfer.recipient.int] and
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state.balances[transfer.recipient.int] < MIN_DEPOSIT_AMOUNT):
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notice "Transfer: sender balance too low for transfer amount or fee"
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return false
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true
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proc processBlock*(
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state: var BeaconState, blck: BeaconBlock, flags: UpdateFlags,
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stateCache: var StateCache): bool =
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## When there's a new block, we need to verify that the block is sane and
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## update the state accordingly
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# TODO when there's a failure, we should reset the state!
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# TODO probably better to do all verification first, then apply state changes
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if not processBlockHeader(state, blck, flags, stateCache):
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notice "Block header not valid", slot = humaneSlotNum(state.slot)
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return false
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if not processRandao(state, blck.body, flags, stateCache):
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debug "[Block processing] Randao failure", slot = humaneSlotNum(state.slot)
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return false
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processEth1Data(state, blck.body)
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if not processProposerSlashings(state, blck, flags, stateCache):
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debug "[Block processing] Proposer slashing failure", slot = humaneSlotNum(state.slot)
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return false
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if not processAttesterSlashings(state, blck, stateCache):
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debug "[Block processing] Attester slashing failure", slot = humaneSlotNum(state.slot)
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return false
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if not processAttestations(state, blck, flags, stateCache):
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debug "[Block processing] Attestation processing failure", slot = humaneSlotNum(state.slot)
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return false
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if not processDeposits(state, blck):
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debug "[Block processing] Deposit processing failure", slot = humaneSlotNum(state.slot)
|
|
return false
|
|
|
|
if not processVoluntaryExits(state, blck, flags):
|
|
debug "[Block processing] Exit processing failure", slot = humaneSlotNum(state.slot)
|
|
return false
|
|
|
|
if not processTransfers(state, blck, flags, stateCache):
|
|
debug "[Block processing] Transfer processing failure", slot = humaneSlotNum(state.slot)
|
|
return false
|
|
|
|
true
|