NEO Smart Contract: Caller Validation

In many, if not all cases, you will probably be wanting to validate whether the address invoking your contract code is really who they say they are.

Thankfully we are provided with the following validation method:

boa.blockchain.vm.Neo.Runtime.CheckWitness

This method accepts a single parameter which represents the address that you would like to validate against the address used to invoke the contract code.

The provided input value can be in any of the following formats which can be used to identify the caller address:

#\xba\'\x03\xc52c\xe8\xd6\xe5"\xdc2 39\xdc\xd8\xee\xe9

AK2nJJpJr6o664CWJKi1QRXjqeic2zRp8y

031a6c6fbbdf02ca351745fa86b9ba5a9452d785ac4f7fc2b7548ca2a46c4fcf4a

These can all be found in the neo-python cli when running the command:

wallet

In order to test this out, we can use the following sample contract code:

from boa.blockchain.vm.Neo.Runtime import CheckWitness

def Main(caller):

   isCaller = CheckWitness(caller)

   if isCaller:

        return True

   return False

This will simply validate whether the provided input for caller matches the address that was used to invoke the contract.From our neo-python cli, we can use any of the following queries to test this out using our build & test method.Address:

build smartContracts/callerValidation.py test 07 01 False False AK2nJJpJr6o664CWJKi1QRXjqeic2zRp8y

Public key:

build smartContracts/callerValidation.py test 07 01 False False 031a6c6fbbdf02ca351745fa86b9ba5a9452d785ac4f7fc2b7548ca2a46c4fcf4a

Script hash of the address:

build smartContracts/callerValidation.py test 07 01 False False #\xba\'\x03\xc52c\xe8\xd6\xe5"\xdc2 39\xdc\xd8\xee\xe9

Running these should all result in true if you are running on the main wallet provided for the private net. If you are running your own instance or calling from another wallet simply copy the desired value from the result of the wallet command. If you run a test execution with a value that is not your wallet, the execution will return False. For example:

build smartContracts/callerValidation.py test 07 01 False False BF3nJJpJr6o664CWJKi1QRXjqeic2zRaaa

For a more in depth example please refer to the Hasty Ogre Name Service contract code.

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