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nimbus-eth1/nimbus/transaction/host_services.nim

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# Nimbus - Services available to EVM code that is run for a transaction
#
# Copyright (c) 2019-2021 Status Research & Development GmbH
# Licensed under either of
# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
# * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
# at your option. This file may not be copied, modified, or distributed except according to those terms.
#{.push raises: [Defect].}
import
sets, times, stint, chronicles,
eth/common/eth_types, ../db/accounts_cache, ../forks,
".."/[vm_state, vm_computation, vm_internals, vm_gas_costs],
./host_types, ./host_trace, ./host_call_nested
proc setupTxContext(host: TransactionHost) =
# Conversion issues:
#
# `txContext.tx_gas_price` is 256-bit, but `vmState.txGasPrice` is 64-bit
# signed (`GasInt`), and in reality it tends to be a fairly small integer,
# usually < 16 bits. Our EVM truncates whatever it gets blindly to 64-bit
# anyway. Largest ever so far may be 100,000,000.
# https://medium.com/amberdata/most-expensive-transaction-in-ethereum-blockchain-history-99d9a30d8e02
#
# `txContext.block_number` is 64-bit signed. This is actually too small for
# the Nimbus `BlockNumber` type which is 256-bit (for now), so we truncate
# the other way.
#
# `txContext.chain_id` is 256-bit, but `vmState.chaindb.config.chainId` is
# 64-bit or 32-bit depending on the target CPU architecture (Nim `uint`).
# Our EVM truncates whatever it gets blindly to 64-bit or 32-bit.
#
# No conversion required with the other fields:
#
# `txContext.tx_origin` and `txContext.block_coinbase` are 20-byte Ethereum
# addresses, no issues with these.
#
# `txContext.block_timestamp` is 64-bit signed. `vmState.timestamp.toUnix`
# is from Nim `std/times` and returns `int64` so this matches. (It's
# overkill that we store a full seconds and nanoseconds object in
# `vmState.timestamp` though.)
#
# `txContext.block_gas_limit` is 64-bit signed (EVMC assumes
# [EIP-1985](https://eips.ethereum.org/EIPS/eip-1985) although it's not
# officially accepted), and `vmState.gasLimit` is too (`GasInt`).
#
# `txContext.block_prev_randao` is 256-bit, and this one can genuinely take
# values over much of the 256-bit range.
let vmState = host.vmState
host.txContext.tx_gas_price = vmState.txGasPrice.u256.toEvmc
host.txContext.tx_origin = vmState.txOrigin.toEvmc
# vmState.coinbase now unused
host.txContext.block_coinbase = vmState.minerAddress.toEvmc
# vmState.blockNumber now unused
host.txContext.block_number = (vmState.blockNumber
.truncate(typeof(host.txContext.block_number)))
# vmState.timestamp now unused
host.txContext.block_timestamp = vmState.timestamp.toUnix
# vmState.gasLimit now unused
host.txContext.block_gas_limit = vmState.gasLimit
# vmState.difficulty now unused
host.txContext.chain_id = vmState.chaindb.config.chainId.uint.u256.toEvmc
host.txContext.block_base_fee = vmState.baseFee.toEvmc
# Most host functions do `flip256` in `evmc_host_glue`, but due to this
# result being cached, it's better to do `flip256` when filling the cache.
host.txContext.tx_gas_price = flip256(host.txContext.tx_gas_price)
host.txContext.chain_id = flip256(host.txContext.chain_id)
host.txContext.block_base_fee = flip256(host.txContext.block_base_fee)
# EIP-4399
# Transfer block randomness to difficulty OPCODE
let difficulty = vmState.difficulty.toEvmc
host.txContext.block_prev_randao = flip256(difficulty)
host.cachedTxContext = true
const use_evmc_glue = defined(evmc_enabled)
# When using the EVMC binary interface, each of the functions below is wrapped
# in another function that converts types to be compatible with the binary
# interface, and the functions below are not called directly. The conversions
# mostly just cast between byte-compatible types, so to avoid a redundant call
# layer, make the functions below `{.inline.}` when wrapped in this way.
when use_evmc_glue:
{.push inline.}
proc accountExists(host: TransactionHost, address: HostAddress): bool {.show.} =
if host.vmState.fork >= FkSpurious:
not host.vmState.readOnlyStateDB.isDeadAccount(address)
else:
host.vmState.readOnlyStateDB.accountExists(address)
# TODO: Why is `address` an argument in `getStorage`, `setStorage` and
# `selfDestruct`, if an EVM is only allowed to do these things to its own
# contract account and the host always knows which account?
proc getStorage(host: TransactionHost, address: HostAddress, key: HostKey): HostValue {.show.} =
host.vmState.readOnlyStateDB.getStorage(address, key)
proc setStorageStatus(host: TransactionHost, address: HostAddress,
key: HostKey, newVal: HostValue): EvmcStorageStatus {.show.} =
let
db = host.vmState.readOnlyStateDB
currentVal = db.getStorage(address, key)
if currentVal == newVal:
return EVMC_STORAGE_ASSIGNED
host.vmState.mutateStateDB:
db.setStorage(address, key, newVal)
# https://eips.ethereum.org/EIPS/eip-1283
let originalVal = db.getCommittedStorage(address, key)
if originalVal == currentVal:
if originalVal.isZero:
return EVMC_STORAGE_ADDED
# !is_zero(original_val)
if newVal.isZero:
return EVMC_STORAGE_DELETED
else:
return EVMC_STORAGE_MODIFIED
# originalVal != currentVal
if originalVal.isZero.not:
if currentVal.isZero:
if originalVal == newVal:
return EVMC_STORAGE_DELETED_RESTORED
else:
return EVMC_STORAGE_DELETED_ADDED
# !is_zero(current_val)
if newVal.isZero:
return EVMC_STORAGE_MODIFIED_DELETED
# !is_zero(new_val)
if originalVal == newVal:
return EVMC_STORAGE_MODIFIED_RESTORED
else:
return EVMC_STORAGE_ASSIGNED
# is_zero(original_val)
if originalVal == newVal:
return EVMC_STORAGE_ADDED_DELETED
else:
return EVMC_STORAGE_ASSIGNED
proc setStorage(host: TransactionHost, address: HostAddress,
key: HostKey, newVal: HostValue): EvmcStorageStatus {.show.} =
let
status = setStorageStatus(host, address, key, newVal)
fork = host.vmState.fork
refund = SstoreCost[fork][status].gasRefund
if refund != 0:
# TODO: Refund depends on `Computation` at the moment.
host.computation.gasMeter.refundGas(refund)
status
proc getBalance(host: TransactionHost, address: HostAddress): HostBalance {.show.} =
host.vmState.readOnlyStateDB.getBalance(address)
proc getCodeSize(host: TransactionHost, address: HostAddress): HostSize {.show.} =
# TODO: Check this `HostSize`, it was copied as `uint` from other code.
# Note: Old `evmc_host` uses `getCode(address).len` instead.
host.vmState.readOnlyStateDB.getCodeSize(address).HostSize
proc getCodeHash(host: TransactionHost, address: HostAddress): HostHash {.show.} =
let db = host.vmState.readOnlyStateDB
# TODO: Copied from `Computation`, but check if that code is wrong with
# `FkSpurious`, as it has different calls from `accountExists` above.
if not db.accountExists(address) or db.isEmptyAccount(address):
default(HostHash)
else:
db.getCodeHash(address)
proc copyCode(host: TransactionHost, address: HostAddress,
code_offset: HostSize, buffer_data: ptr byte,
buffer_size: HostSize): HostSize {.show.} =
# We must handle edge cases carefully to prevent overflows. `len` is signed
# type `int`, but `code_offset` and `buffer_size` are _unsigned_, and may
# have large values (deliberately if attacked) that exceed the range of `int`.
#
# Comparing signed and unsigned types is _unsafe_: A type-conversion will
# take place which breaks the comparison for some values. So here we use
# explicit type-conversions, always compare the same types, and always
# convert towards the type that cannot truncate because preceding checks have
# been used to reduce the possible value range.
#
# Note, when there is no code, `getCode` result is empty `seq`. It was `nil`
# when the DB was first implemented, due to Nim language changes since then.
var code: seq[byte] = host.vmState.readOnlyStateDB.getCode(address)
var safe_len: int = code.len # It's safe to assume >= 0.
if code_offset >= safe_len.HostSize:
return 0
let safe_offset = code_offset.int
safe_len = safe_len - safe_offset
if buffer_size < safe_len.HostSize:
safe_len = buffer_size.int
if safe_len > 0:
copyMem(buffer_data, code[safe_offset].addr, safe_len)
return safe_len.HostSize
proc selfDestruct(host: TransactionHost, address, beneficiary: HostAddress) {.show.} =
host.vmState.mutateStateDB:
let closingBalance = db.getBalance(address)
let beneficiaryBalance = db.getBalance(beneficiary)
# Transfer to beneficiary
db.setBalance(beneficiary, beneficiaryBalance + closingBalance)
# Zero balance of account being deleted.
# This must come after sending to the beneficiary in case the
# contract named itself as the beneficiary.
db.setBalance(address, 0.u256)
# TODO: Calling via `computation` is necessary to make some tests pass.
# Here's one that passes only with this:
# tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest487.json
# We can't keep using `computation` though.
host.computation.touchedAccounts.incl(beneficiary)
host.computation.selfDestructs.incl(address)
#host.touchedAccounts.incl(beneficiary)
#host.selfDestructs.incl(address)
template call(host: TransactionHost, msg: EvmcMessage): EvmcResult =
# `call` is special. The C stack usage must be kept small for deeply nested
# EVM calls. To ensure small stack, `{.show.}` must be handled at
# `host_call_nested`, not here, and this function must use `template` to
# inline at Nim level (same for `callEvmcNested`). `{.inline.}` is not good
# enough. Due to object return it ends up using a lot more stack.
host.callEvmcNested(msg)
proc getTxContext(host: TransactionHost): EvmcTxContext {.show.} =
if not host.cachedTxContext:
host.setupTxContext()
return host.txContext
proc getBlockHash(host: TransactionHost, number: HostBlockNumber): HostHash {.show.} =
# TODO: Clean up the different messy block number types.
host.vmState.getAncestorHash(number.toBlockNumber)
proc emitLog(host: TransactionHost, address: HostAddress,
data: ptr byte, data_size: HostSize,
topics: ptr HostTopic, topics_count: HostSize) {.show.} =
var log: Log
# Note, this assumes the EVM ensures `data_size` and `topics_count` cannot be
# unreasonably large values. Largest `topics_count` should be 4 according to
# EVMC documentation, but we won't restrict it here.
if topics_count > 0:
let topicsArray = cast[ptr UncheckedArray[HostTopic]](topics)
let count = topics_count.int
log.topics = newSeq[Topic](count)
for i in 0 ..< count:
log.topics[i] = topicsArray[i]
if (data_size > 0):
log.data = newSeq[byte](data_size.int)
copyMem(log.data[0].addr, data, data_size.int)
log.address = address
# TODO: Calling via `computation` is necessary to makes some tests pass.
# Here's one that passes only with this:
# tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest583.json
# We can't keep using `computation` though.
host.computation.logEntries.add(log)
#host.logEntries.add(log)
proc accessAccount(host: TransactionHost, address: HostAddress): EvmcAccessStatus {.show.} =
host.vmState.mutateStateDB:
if not db.inAccessList(address):
db.accessList(address)
return EVMC_ACCESS_COLD
else:
return EVMC_ACCESS_WARM
proc accessStorage(host: TransactionHost, address: HostAddress,
key: HostKey): EvmcAccessStatus {.show.} =
host.vmState.mutateStateDB:
if not db.inAccessList(address, key):
db.accessList(address, key)
return EVMC_ACCESS_COLD
else:
return EVMC_ACCESS_WARM
when use_evmc_glue:
{.pop: inline.}
const included_from_host_services = true
include ./evmc_host_glue
else:
export
accountExists, getStorage, storage, getBalance, getCodeSize, getCodeHash,
copyCode, selfDestruct, getTxContext, call, getBlockHash, emitLog
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