research/casper4/simple_casper_tester.py

from ethereum import tester as t
from ethereum import utils, state_transition, transactions, abi
from viper import compiler
import serpent
from ethereum.slogging import LogRecorder, configure_logging, set_level
config_string = ':info,eth.vm.log:trace,eth.vm.op:trace,eth.vm.stack:trace,eth.vm.exit:trace,eth.pb.msg:trace,eth.pb.tx:debug'
#configure_logging(config_string=config_string)
import rlp
s = t.state()
t.languages['viper'] = compiler.Compiler()
t.gas_limit = 9999999

EPOCH_LENGTH = 100

def inject_tx(txhex):
    tx = rlp.decode(utils.decode_hex(txhex[2:]), transactions.Transaction)
    s.state.set_balance(tx.sender, tx.startgas * tx.gasprice)
    state_transition.apply_transaction(s.state, tx)
    contract_address = utils.mk_contract_address(tx.sender, 0)
    assert s.state.get_code(contract_address)
    return contract_address

code_template = """
~calldatacopy(0, 0, 128)
~call(3000, 1, 0, 0, 128, 0, 32)
return(~mload(0) == %s)
"""

def mk_validation_code(address):
    return serpent.compile(code_template % (utils.checksum_encode(address)))

# Install RLP decoder library
rlp_decoder_address = inject_tx( '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')

# Install sig hasher

s.state.set_balance('0x6e7406512b244843c1171840dfcd3d7532d979fe', 7291200000000000)

sighasher_address = inject_tx( '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')

# Install purity checker

purity_checker_address = inject_tx( '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')

ct = abi.ContractTranslator([{'name': 'check(address)', 'type': 'function', 'constant': True, 'inputs': [{'name': 'addr', 'type': 'address'}], 'outputs': [{'name': 'out', 'type': 'bool'}]}, {'name': 'submit(address)', 'type': 'function', 'constant': False, 'inputs': [{'name': 'addr', 'type': 'address'}], 'outputs': [{'name': 'out', 'type': 'bool'}]}])
# Check that the RLP decoding library and the sig hashing library are "pure"
assert utils.big_endian_to_int(s.send(t.k0, purity_checker_address, 0, ct.encode('submit', [rlp_decoder_address]))) == 1
assert utils.big_endian_to_int(s.send(t.k0, purity_checker_address, 0, ct.encode('submit', [sighasher_address]))) == 1

k1_valcode_addr = s.send(t.k0, "", 0, mk_validation_code(t.a0))
assert utils.big_endian_to_int(s.send(t.k0, purity_checker_address, 0, ct.encode('submit', [k1_valcode_addr]))) == 1

# Install Casper

casper_code = open('simple_casper.v.py').read().replace('0x1Db3439a222C519ab44bb1144fC28167b4Fa6EE6', utils.checksum_encode(k1_valcode_addr)) \
                                               .replace('0x476c2cA9a7f3B16FeCa86512276271FAf63B6a24', utils.checksum_encode(sighasher_address)) \
                                               .replace('0xD7a3BD6C9eA32efF147d067f907AE6b22d436F91', utils.checksum_encode(purity_checker_address))

print('Casper code length', len(compiler.compile(casper_code)))

casper = s.abi_contract(casper_code, language='viper', startgas=5555555)

print('Gas consumed to launch Casper', s.state.receipts[-1].gas_used - s.state.receipts[-2].gas_used)

# Helper functions for making a prepare, commit, login and logout message

def mk_prepare(validator_index, epoch, hash, ancestry_hash, source_epoch, source_ancestry_hash, key):
    sighash = utils.sha3(rlp.encode([validator_index, epoch, hash, ancestry_hash, source_epoch, source_ancestry_hash]))
    v, r, s = utils.ecdsa_raw_sign(sighash, key)
    sig = utils.encode_int32(v) + utils.encode_int32(r) + utils.encode_int32(s)
    return rlp.encode([validator_index, epoch, hash, ancestry_hash, source_epoch, source_ancestry_hash, sig])

def mk_commit(validator_index, epoch, hash, prev_commit_epoch, key):
    sighash = utils.sha3(rlp.encode([validator_index, epoch, hash, prev_commit_epoch]))
    v, r, s = utils.ecdsa_raw_sign(sighash, key)
    sig = utils.encode_int32(v) + utils.encode_int32(r) + utils.encode_int32(s)
    return rlp.encode([validator_index, epoch, hash, prev_commit_epoch, sig])

def mk_status_flicker(validator_index, epoch, login, key):
    sighash = utils.sha3(rlp.encode([validator_index, epoch, login]))
    v, r, s = utils.ecdsa_raw_sign(sighash, key)
    sig = utils.encode_int32(v) + utils.encode_int32(r) + utils.encode_int32(s)
    return rlp.encode([validator_index, epoch, login, sig])

# Begin the test

print("Starting tests")
casper.initiate()
# Initialize the first epoch
s.state.block_number = EPOCH_LENGTH 
print('foo', casper.initialize_epoch(1))
assert casper.get_nextValidatorIndex() == 1
start = s.snapshot()
print("Epoch initialized")
print("Reward factor: %.8f" % (casper.get_reward_factor() * 2 / 3))
# Send a prepare message
#configure_logging(config_string=config_string)
casper.prepare(mk_prepare(0, 1, '\x35' * 32, '\x00' * 32, 0, '\x00' * 32, t.k0))
print('Gas consumed for a prepare: %d (including %d intrinsic gas)' %
      (s.state.receipts[-1].gas_used - s.state.receipts[-2].gas_used, s.last_tx.intrinsic_gas_used))
epoch_1_anchash = utils.sha3(b'\x35' * 32 + b'\x00' * 32)
assert casper.get_consensus_messages__hash_justified(1, b'\x35' * 32)
assert casper.get_consensus_messages__ancestry_hash_justified(1, epoch_1_anchash)
print("Prepare message processed")
try:
    casper.prepare(mk_prepare(0, 1, '\x35' * 32, '\x00' * 32, 0, '\x00' * 32, t.k0))
    success = True
except:
    success = False
assert not success
print("Prepare message fails the second time")
# Send a commit message
casper.commit(mk_commit(0, 1, '\x35' * 32, 0, t.k0))
print('Gas consumed for a commit: %d (including %d intrinsic gas)' %
      (s.state.receipts[-1].gas_used - s.state.receipts[-2].gas_used, s.last_tx.intrinsic_gas_used))
# Check that we committed
assert casper.get_consensus_messages__committed(1)
print("Commit message processed")
# Initialize the second epoch 
s.state.block_number += EPOCH_LENGTH
casper.initialize_epoch(2)
# Check that the dynasty increased as expected
assert casper.get_dynasty() == 1
assert casper.get_total_deposits(1) == casper.get_total_deposits(0) > 0
print("Second epoch initialized, dynasty increased as expected")
# Send a prepare message
casper.prepare(mk_prepare(0, 2, '\x45' * 32, epoch_1_anchash, 1, epoch_1_anchash, t.k0))
# Send a commit message
epoch_2_commit = mk_commit(0, 2, '\x45' * 32, 1, t.k0)
casper.commit(epoch_2_commit)
epoch_2_anchash = utils.sha3(b'\x45' * 32 + epoch_1_anchash)
assert casper.get_consensus_messages__ancestry_hash_justified(2, epoch_2_anchash)
# Check that we committed
assert casper.get_consensus_messages__committed(2)
# Initialize the third epoch
s.state.block_number += EPOCH_LENGTH
casper.initialize_epoch(3)
print("Second epoch prepared and committed, third epoch initialized")
# Test the NO_DBL_PREPARE slashing condition
p1 = mk_prepare(0, 3, '\x56' * 32, epoch_2_anchash, 2, epoch_2_anchash, t.k0)
p2 = mk_prepare(0, 3, '\x57' * 32, epoch_2_anchash, 2, epoch_2_anchash, t.k0)
snapshot = s.snapshot()
casper.double_prepare_slash(p1, p2)
s.revert(snapshot)
print("NO_DBL_PREPARE slashing condition works")
# Test the PREPARE_COMMIT_CONSISTENCY slashing condition
p3 = mk_prepare(0, 3, '\x58' * 32, epoch_2_anchash, 0, b'\x00' * 32, t.k0)
snapshot = s.snapshot()
casper.prepare_commit_inconsistency_slash(p3, epoch_2_commit)
s.revert(snapshot)
print("PREPARE_COMMIT_CONSISTENCY slashing condition works")
# Finish the third epoch
casper.prepare(p1)
casper.commit(mk_commit(0, 3, '\x56' * 32, 2, t.k0))
epoch_3_anchash = utils.sha3(b'\x56' * 32 + epoch_2_anchash)
assert casper.get_consensus_messages__ancestry_hash_justified(3, epoch_3_anchash)
assert casper.get_consensus_messages__committed(3)
# Initialize the fourth epoch. Not doing prepares or commits during this epoch.
s.state.block_number += EPOCH_LENGTH
casper.initialize_epoch(4)
assert casper.get_dynasty() == 3
epoch_4_anchash = utils.sha3(b'\x67' * 32 + epoch_3_anchash)
# Not publishing this prepare for the time being
p4 = mk_prepare(0, 4, '\x78' * 32, '\x12' * 32, 3, '\x24' * 32, t.k0)
# Initialize the fifth epoch
s.state.block_number += EPOCH_LENGTH
casper.initialize_epoch(5)
print("Epochs up to 5 initialized")
# Dynasty not incremented because no commits were made
assert casper.get_dynasty() == 3
epoch_5_anchash = utils.sha3(b'\x78' * 32 + epoch_4_anchash)
p5 = mk_prepare(0, 5, '\x78' * 32, epoch_4_anchash, 3, epoch_3_anchash, t.k0)
casper.prepare(p5)
# Test the COMMIT_REQ slashing condition
kommit = mk_commit(0, 5, b'\x80' * 32, 3, t.k0)
epoch_inc = 1 + int(86400 / 14 / EPOCH_LENGTH)
s.state.block_number += EPOCH_LENGTH * epoch_inc
print("Speeding up time to test remaining two slashing conditions")
for i in range(6, 6 + epoch_inc):
    casper.initialize_epoch(i)
print("Epochs up to %d initialized" % (6 + epoch_inc))
snapshot = s.snapshot()
casper.commit_non_justification_slash(kommit)
s.revert(snapshot)
try:
    casper.commit_non_justification_slash(0, epoch_2_commit)
    success = True
except:
    success = False
assert not success
print("COMMIT_REQ slashing condition works")
# Test the PREPARE_REQ slashing condition
casper.derive_parenthood(epoch_3_anchash, b'\x67' * 32, epoch_4_anchash)
assert casper.get_ancestry(epoch_3_anchash, epoch_4_anchash) == 1
assert casper.get_ancestry(epoch_4_anchash, epoch_5_anchash) == 1
casper.derive_ancestry(epoch_3_anchash, epoch_4_anchash, epoch_5_anchash)
assert casper.get_ancestry(epoch_3_anchash, epoch_5_anchash) == 2
snapshot = s.snapshot()
casper.prepare_non_justification_slash(p4)
s.revert(snapshot)
try:
    casper.prepare_non_justification_slash(p5)
    success = True
except:
    success = False
assert not success
print("PREPARE_REQ slashing condition works")

print("Restarting the chain for test 2")
# Restart the chain
s.revert(start)
assert casper.get_dynasty() == 0
assert casper.get_current_epoch() == 1
assert casper.get_consensus_messages__ancestry_hash_justified(0, b'\x00' * 32)
print("Epoch 1 initialized")
for k in (t.k1, t.k2, t.k3, t.k4, t.k5, t.k6):
    valcode_addr = s.send(t.k0, '', 0, mk_validation_code(utils.privtoaddr(k)))
    assert utils.big_endian_to_int(s.send(t.k0, purity_checker_address, 0, ct.encode('submit', [valcode_addr]))) == 1
    casper.deposit(valcode_addr, utils.privtoaddr(k), value=3 * 10**18)
print("Processed 6 deposits")
casper.prepare(mk_prepare(0, 1, b'\x10' * 32, b'\x00' * 32, 0, b'\x00' * 32, t.k0))
casper.commit(mk_commit(0, 1, b'\x10' * 32, 0, t.k0))
epoch_1_anchash = utils.sha3(b'\x10' * 32 + b'\x00' * 32)
assert casper.get_consensus_messages__committed(1)
print("Prepared and committed")
s.state.block_number += EPOCH_LENGTH
casper.initialize_epoch(2)
print("Epoch 2 initialized")
assert casper.get_dynasty() == 1
casper.prepare(mk_prepare(0, 2, b'\x20' * 32, epoch_1_anchash, 1, epoch_1_anchash, t.k0))
casper.commit(mk_commit(0, 2, b'\x20' * 32, 1, t.k0))
epoch_2_anchash = utils.sha3(b'\x20' * 32 + epoch_1_anchash)
assert casper.get_consensus_messages__committed(2)
print("Confirmed that one key is still sufficient to prepare and commit")
s.state.block_number += EPOCH_LENGTH
casper.initialize_epoch(3)
print("Epoch 3 initialized")
assert casper.get_dynasty() == 2
assert 3 * 10**18 <= casper.get_total_deposits(0) < 4 * 10**18
assert 3 * 10**18 <= casper.get_total_deposits(1) < 4 * 10**18
assert 21 * 10**18 <= casper.get_total_deposits(2) < 22 * 10**18
print("Confirmed new total_deposits")
try:
    # Try to log out, but sign with the wrong key
    casper.flick_status(mk_status_flicker(0, 3, 0, t.k1))
    success = True
except:
    success = False
assert not success
# Log out
casper.flick_status(mk_status_flicker(4, 3, 0, t.k4))
casper.flick_status(mk_status_flicker(5, 3, 0, t.k5))
casper.flick_status(mk_status_flicker(6, 3, 0, t.k6))
print("Logged out three validators")
# Validators leave the fwd validator set in dynasty 4
assert casper.get_validators__dynasty_end(4) == 4
epoch_3_anchash = utils.sha3(b'\x30' * 32 + epoch_2_anchash)
# Prepare from one validator
casper.prepare(mk_prepare(0, 3, b'\x30' * 32, epoch_2_anchash, 2, epoch_2_anchash, t.k0))
# Not prepared yet
assert not casper.get_consensus_messages__hash_justified(3, b'\x30' * 32)
print("Prepare from one validator no longer sufficient")
# Prepare from 3 more validators
for i, k in ((1, t.k1), (2, t.k2), (3, t.k3)):
    casper.prepare(mk_prepare(i, 3, b'\x30' * 32, epoch_2_anchash, 2, epoch_2_anchash, k))
# Still not prepared
assert not casper.get_consensus_messages__hash_justified(3, b'\x30' * 32)
print("Prepare from four of seven validators still not sufficient")
# Prepare from a fifth validator
casper.prepare(mk_prepare(4, 3, b'\x30' * 32, epoch_2_anchash, 2, epoch_2_anchash, t.k4))
# NOW we're prepared!
assert casper.get_consensus_messages__hash_justified(3, b'\x30' * 32)
print("Prepare from five of seven validators sufficient!")
# Five commits
for i, k in enumerate([t.k0, t.k1, t.k2, t.k3, t.k4]):
    casper.commit(mk_commit(i, 3, b'\x30' * 32, 2 if i == 0 else 0, k))
# And we committed!
assert casper.get_consensus_messages__committed(3)
print("Commit from five of seven validators sufficient")
# Start epoch 4
s.state.block_number += EPOCH_LENGTH
casper.initialize_epoch(4)
assert casper.get_dynasty() == 3
print("Epoch 4 initialized")
# Prepare and commit
epoch_4_anchash = utils.sha3(b'\x40' * 32 + epoch_3_anchash)
for i, k in enumerate([t.k0, t.k1, t.k2, t.k3, t.k4]):
    casper.prepare(mk_prepare(i, 4, b'\x40' * 32, epoch_3_anchash, 3, epoch_3_anchash, k))
for i, k in enumerate([t.k0, t.k1, t.k2, t.k3, t.k4]):
    casper.commit(mk_commit(i, 4, b'\x40' * 32, 3, k))
assert casper.get_consensus_messages__committed(4)
print("Prepared and committed")
# Start epoch 5 / dynasty 4
s.state.block_number += EPOCH_LENGTH
casper.initialize_epoch(5)
print("Epoch 5 initialized")
assert casper.get_dynasty() == 4
assert 21 * 10**18 <= casper.get_total_deposits(3) <= 22 * 10**18
assert 12 * 10**18 <= casper.get_total_deposits(4) <= 13 * 10**18
epoch_5_anchash = utils.sha3(b'\x50' * 32 + epoch_4_anchash)
# Do three prepares
for i, k in enumerate([t.k0, t.k1, t.k2]):
    casper.prepare(mk_prepare(i, 5, b'\x50' * 32, epoch_4_anchash, 4, epoch_4_anchash, k))
# Three prepares are insufficient because there are still five validators in the rear validator set
assert not casper.get_consensus_messages__hash_justified(5, b'\x50' * 32)
print("Three prepares insufficient, as rear validator set still has seven")
# Do two more prepares
for i, k in [(3, t.k3), (4, t.k4)]:
    casper.prepare(mk_prepare(i, 5, b'\x50' * 32, epoch_4_anchash, 4, epoch_4_anchash, k))
# Now we're good!
assert casper.get_consensus_messages__hash_justified(5, b'\x50' * 32)
print("Five prepares sufficient")
for i, k in enumerate([t.k0, t.k1, t.k2, t.k3, t.k4]):
    casper.commit(mk_commit(i, 5, b'\x50' * 32, 4, k))
# Committed!
assert casper.get_consensus_messages__committed(5)
# Start epoch 6 / dynasty 5
s.state.block_number += EPOCH_LENGTH
casper.initialize_epoch(6)
assert casper.get_dynasty() == 5
print("Epoch 6 initialized")
# Log back in
old_deposit_start = casper.get_dynasty_start_epoch(casper.get_validators__dynasty_start(4))
old_deposit_end = casper.get_dynasty_start_epoch(casper.get_validators__dynasty_end(4) + 1)
old_deposit = casper.get_validators__deposit(4)
# Explanation:
# * During dynasty 0, the validator deposited, so he joins the current set in dynasty 2
#   (epoch 3), and the previous set in dynasty 3 (epoch 4)
# * During dynasty 2, the validator logs off, so he leaves the current set in dynasty 4
#   (epoch 5) and the previous set in dynasty 5 (epoch 6)
assert [casper.check_eligible_in_epoch(4, i) for i in range(7)] == [0, 0, 0, 2, 3, 1, 0]
casper.flick_status(mk_status_flicker(4, 6, 1, t.k4))
# Explanation:
# * During dynasty 7, the validator will log on again. Hence, the dynasty mask 
#   should include dynasties 4, 5, 6
assert [casper.check_eligible_in_epoch(4, i) for i in range(7)] == [0, 0, 0, 2, 3, 1, 0]
new_deposit = casper.get_validators__deposit(4)
print("One validator logging back in")
print("Penalty from %d epochs: %.4f" % (old_deposit_end - old_deposit_start, 1 - new_deposit / old_deposit))
assert casper.get_validators__dynasty_start(4) == 7
# Here three prepares and three commits should be sufficient!
epoch_6_anchash = utils.sha3(b'\x60' * 32 + epoch_5_anchash)
for i, k in enumerate([t.k0, t.k1, t.k2]):
    casper.prepare(mk_prepare(i, 6, b'\x60' * 32, epoch_5_anchash, 5, epoch_5_anchash, k))
for i, k in enumerate([t.k0, t.k1, t.k2]):
    casper.commit(mk_commit(i, 6, b'\x60' * 32, 5, k))
assert casper.get_consensus_messages__committed(6)
print("Three of four prepares and commits sufficient")
# Start epoch 7 / dynasty 6
s.state.block_number += EPOCH_LENGTH
casper.initialize_epoch(7)
assert casper.get_dynasty() == 6
print("Epoch 7 initialized")
# Here three prepares and three commits should be sufficient!
epoch_7_anchash = utils.sha3(b'\x70' * 32 + epoch_6_anchash)
for i, k in enumerate([t.k0, t.k1, t.k2]):
    #if i == 1:
    #    configure_logging(config_string=config_string)
    casper.prepare(mk_prepare(i, 7, b'\x70' * 32, epoch_6_anchash, 6, epoch_6_anchash, k))
    #if i == 1:
    #    import sys
    #    sys.exit()
print('Gas consumed for first prepare', s.state.receipts[-1].gas_used - s.state.receipts[-2].gas_used)
print('Gas consumed for second prepare', s.state.receipts[-2].gas_used - s.state.receipts[-3].gas_used)
print('Gas consumed for third prepare', s.state.receipts[-3].gas_used - s.state.receipts[-4].gas_used)
for i, k in enumerate([t.k0, t.k1, t.k2]):
    casper.commit(mk_commit(i, 7, b'\x70' * 32, 6, k))
print('Gas consumed for first commit', s.state.receipts[-1].gas_used - s.state.receipts[-2].gas_used)
print('Gas consumed for second commit', s.state.receipts[-2].gas_used - s.state.receipts[-3].gas_used)
print('Gas consumed for third commit', s.state.receipts[-3].gas_used - s.state.receipts[-4].gas_used)
assert casper.get_consensus_messages__committed(7)
print("Three of four prepares and commits sufficient")
# Start epoch 8 / dynasty 7
s.state.block_number += EPOCH_LENGTH
casper.initialize_epoch(8)
assert casper.get_dynasty() == 7
print("Epoch 8 initialized")
assert 12 * 10**18 <= casper.get_total_deposits(6) <= 13 * 10**18
assert 15 * 10**18 <= casper.get_total_deposits(7) <= 16 * 10**18
epoch_8_anchash = utils.sha3(b'\x80' * 32 + epoch_7_anchash)
# Do three prepares
for i, k in enumerate([t.k0, t.k1, t.k2]):
    casper.prepare(mk_prepare(i, 8, b'\x80' * 32, epoch_7_anchash, 7, epoch_7_anchash, k))
# Three prepares are insufficient because there are still five validators in the rear validator set
assert not casper.get_consensus_messages__hash_justified(8, b'\x80' * 32)
print("Three prepares no longer sufficient, as the forward validator set has five validators")
# Do one more prepare
for i, k in [(3, t.k3)]:
    casper.prepare(mk_prepare(i, 8, b'\x80' * 32, epoch_7_anchash, 7, epoch_7_anchash, k))
# Now we're good!
assert casper.get_consensus_messages__hash_justified(8, b'\x80' * 32)
print("Four of five prepares sufficient")
for i, k in enumerate([t.k0, t.k1, t.k2, t.k3, t.k4]):
    casper.commit(mk_commit(i, 8, b'\x80' * 32, 7 if i < 3 else 5, k))
assert casper.get_consensus_messages__committed(8)
print("Committed")
# Validator rejoins current validator set in epoch 8
assert [casper.check_eligible_in_epoch(4, i) for i in range(9)] == [0, 0, 0, 2, 3, 1, 0, 0, 2]

print("All tests passed")