Manually RLP-encoding an ETH tx gives an incorrect result

Question

I fetched a mempool tx

AttributeDict({'blockHash': HexBytes('0x92911a95b4d4b07bb13552bfb29cc43bf43eb7d63af7c968ddaa3df9a6f22988'), 'blockNumber': 17964189, 'from': '0xfd00479c712370C84B398CB8951aebC8039c3024', 'gas': 64744, 'gasPrice': 74341019612, 'maxFeePerGas': 74341019612, 'maxPriorityFeePerGas': 74341019612, 'hash': HexBytes('0x6292090633c01105ec72f4ec9cceb6d7f96321074b4faca9ad394c3a35add749'), 'input': HexBytes('0xa9059cbb00000000000000000000000061b7b515c1ec603cf21463bcac992b60fd610ca900000000000000000000000000000000000000000000002dbf877cf6ec677800'), 'nonce': 38, 'to': '0xaea46A60368A7bD060eec7DF8CBa43b7EF41Ad85', 'transactionIndex': 0, 'value': 0, 'type': 2, 'accessList': [], 'chainId': 1, 'v': 0, 'r': HexBytes('0x8ee28a85ac42174b9e10c49613c0cddcf5d5a5ecb90bd516f81b45a957a64fe2'), 's': HexBytes('0x05349c1076cc83990f425773d6b5995474782f1fccf1b2e43529ac54ac6ae144'), 'yParity': '0x0'})

Or, for more clarity:

'blockHash': HexBytes('0x92911a95b4d4b07bb13552bfb29cc43bf43eb7d63af7c968ddaa3df9a6f22988')
'blockNumber': 17964189
'from': '0xfd00479c712370C84B398CB8951aebC8039c3024'
'gas': 64744
'gasPrice': 74341019612
'maxFeePerGas': 74341019612
'maxPriorityFeePerGas': 74341019612
'hash': HexBytes('0x6292090633c01105ec72f4ec9cceb6d7f96321074b4faca9ad394c3a35add749')
'input': HexBytes('0xa9059cbb00000000000000000000000061b7b515c1ec603cf21463bcac992b60fd610ca900000000000000000000000000000000000000000000002dbf877cf6ec677800')
'nonce': 38
'to': '0xaea46A60368A7bD060eec7DF8CBa43b7EF41Ad85'
'transactionIndex': 0
'value': 0
'type': 2
'accessList': []
'chainId': 1
'v': 0
'r': HexBytes('0x8ee28a85ac42174b9e10c49613c0cddcf5d5a5ecb90bd516f81b45a957a64fe2')
's': HexBytes('0x05349c1076cc83990f425773d6b5995474782f1fccf1b2e43529ac54ac6ae144')
'yParity': '0x0'

I then got the raw transaction (signed):

>>> w3.eth.get_raw_transaction(mempool_tx.hash.hex())
HexBytes('0x02f8b1012685114f11efdc85114f11efdc82fce894aea46a60368a7bd060eec7df8cba43b7ef41ad8580b844a9059cbb00000000000000000000000061b7b515c1ec603cf21463bcac992b60fd610ca900000000000000000000000000000000000000000000002dbf877cf6ec677800c080a08ee28a85ac42174b9e10c49613c0cddcf5d5a5ecb90bd516f81b45a957a64fe2a005349c1076cc83990f425773d6b5995474782f1fccf1b2e43529ac54ac6ae144')

And then I tried to manually construct the raw RLP transaction in python.

So, the syntax is this:

'0x02' + RLP([chainId, nonce, maxPriorityFeePerGas, maxFeePerGas, gasLimit, to, value, data, accessList, v, r, s])

from rlp import encode
from web3.types import HexBytes
from web3.datastructures import AttributeDict

tx = AttributeDict({'blockHash': HexBytes('0x92911a95b4d4b07bb13552bfb29cc43bf43eb7d63af7c968ddaa3df9a6f22988'), 'blockNumber': 17964189, 'from': '0xfd00479c712370C84B398CB8951aebC8039c3024', 'gas': 64744, 'gasPrice': 74341019612, 'maxFeePerGas': 74341019612, 'maxPriorityFeePerGas': 74341019612, 'hash': HexBytes('0x6292090633c01105ec72f4ec9cceb6d7f96321074b4faca9ad394c3a35add749'), 'input': HexBytes('0xa9059cbb00000000000000000000000061b7b515c1ec603cf21463bcac992b60fd610ca900000000000000000000000000000000000000000000002dbf877cf6ec677800'), 'nonce': 38, 'to': '0xaea46A60368A7bD060eec7DF8CBa43b7EF41Ad85', 'transactionIndex': 0, 'value': 0, 'type': 2, 'accessList': [], 'chainId': 1, 'v': 0, 'r': HexBytes('0x8ee28a85ac42174b9e10c49613c0cddcf5d5a5ecb90bd516f81b45a957a64fe2'), 's': HexBytes('0x05349c1076cc83990f425773d6b5995474782f1fccf1b2e43529ac54ac6ae144'), 'yParity': '0x0'})

encoded_tx = encode([ tx['chainId'], tx['nonce'], tx['maxPriorityFeePerGas'], tx['maxFeePerGas'], tx['gas'], tx['to'], tx['value'], tx['input'], tx['accessList'], tx['yParity'], tx['r'], tx['s'] ])
print('0x02' + encoded_tx.hex())

This is the output: f8ca012685114f11efdc85114f11efdc82fce8aa30786165613436413630333638413762443036306565633744463843426134336237454634314164383580b844a9059cbb00000000000000000000000061b7b515c1ec603cf21463bcac992b60fd610ca900000000000000000000000000000000000000000000002dbf877cf6ec677800c083307830a08ee28a85ac42174b9e10c49613c0cddcf5d5a5ecb90bd516f81b45a957a64fe2a005349c1076cc83990f425773d6b5995474782f1fccf1b2e43529ac54ac6ae144

Why is it incorrect? What did I do wrong? Is there a lib that already does this in python?

Answer 1

You need to convert tx["to"] to bytes before encoding. You also have tx["yParity"] where tx["v"] should be, per your syntax guide.

from rlp import encode
from web3.types import HexBytes
from web3.datastructures import AttributeDict

from eth_utils import to_bytes

tx = AttributeDict({'blockHash': HexBytes('0x92911a95b4d4b07bb13552bfb29cc43bf43eb7d63af7c968ddaa3df9a6f22988'), 'blockNumber': 17964189, 'from': '0xfd00479c712370C84B398CB8951aebC8039c3024', 'gas': 64744, 'gasPrice': 74341019612, 'maxFeePerGas': 74341019612, 'maxPriorityFeePerGas': 74341019612, 'hash': HexBytes('0x6292090633c01105ec72f4ec9cceb6d7f96321074b4faca9ad394c3a35add749'), 'input': HexBytes('0xa9059cbb00000000000000000000000061b7b515c1ec603cf21463bcac992b60fd610ca900000000000000000000000000000000000000000000002dbf877cf6ec677800'), 'nonce': 38, 'to': '0xaea46A60368A7bD060eec7DF8CBa43b7EF41Ad85', 'transactionIndex': 0, 'value': 0, 'type': 2, 'accessList': [], 'chainId': 1, 'v': 0, 'r': HexBytes('0x8ee28a85ac42174b9e10c49613c0cddcf5d5a5ecb90bd516f81b45a957a64fe2'), 's': HexBytes('0x05349c1076cc83990f425773d6b5995474782f1fccf1b2e43529ac54ac6ae144'), 'yParity': '0x0'})

expected = HexBytes('0x02f8b1012685114f11efdc85114f11efdc82fce894aea46a60368a7bd060eec7df8cba43b7ef41ad8580b844a9059cbb00000000000000000000000061b7b515c1ec603cf21463bcac992b60fd610ca900000000000000000000000000000000000000000000002dbf877cf6ec677800c080a08ee28a85ac42174b9e10c49613c0cddcf5d5a5ecb90bd516f81b45a957a64fe2a005349c1076cc83990f425773d6b5995474782f1fccf1b2e43529ac54ac6ae144')

to_as_bytes = to_bytes(hexstr=tx["to"])
encoded_tx = encode([ tx['chainId'], tx['nonce'], tx['maxPriorityFeePerGas'], tx['maxFeePerGas'], tx['gas'], to_as_bytes, tx['value'], tx['input'], tx['accessList'], tx['v'], tx['r'], tx['s'] ])

assert HexBytes("0x02" + encoded_tx.hex()) == expected