Syntactically invalid txdata is generated for some solc

Description

Generated txdata cannot be sometimes properly decoded for some solc. In the below example, I obtained a valid input using solc 0.5.12. But I obatined an invalid input not solc 0.4.25, which cannot be properly decoded using off-the-shelf abi decoder.

In the below examples, you can see that, for example, the input fields in the last steps for each output have quite different lengths, though the contract used for testing is the same.

In the output1 (used solc 0.5.12),

0x82668f20000000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000000

this input value can be successfully decoded using the abi decoder in here: https://github.com/miguelmota/ethereum-input-data-decoder

However, in the output2 (used solc 0.4.25),

0x82668f20666666666666666666666666666666666666666666666666666666666666660a

now we have much shorter input value, which cannot be decoded using the abi decoder above. Specifically, it produces a mesage: insufficient data for uint256 type. So I guess Mythril may have generated the syntactically invalid input.

How to Reproduce

Testing program:

contract Test{
  uint n;

  constructor (uint _n) public {
    require (_n==1);
    n = _n;
  }

  function test (uint8 a, uint[] memory b) public {
    require (a==10);
    n--;
  }
}

Command1 (that generates valid txdata):

sudo docker exec CONTAINER_NAME myth analyze /tmp/test.sol --solv 0.5.12 -m integer,exceptions -o json

Output1 for Command1 (simplified):

                             'steps': [{'address': '',
                                        'calldata': '00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000',
                                        'input': '0x608060405234801561001057600080fd5b506040516101b83803806101b88339818101604052602081101561003357600080fd5b81019080805190602001909291905050506001811461005157600080fd5b8060008190555050610150806100686000396000f3fe608060405234801561001057600080fd5b506004361061002b5760003560e01c806382668f2014610030575b600080fd5b6100f36004803603604081101561004657600080fd5b81019080803560ff1690602001909291908035906020019064010000000081111561007057600080fd5b82018360208201111561008257600080fd5b803590602001918460208302840111640100000000831117156100a457600080fd5b919080806020026020016040519081016040528093929190818152602001838360200280828437600081840152601f19601f8201169050808301925050505050505091929192905050506100f5565b005b600a8260ff161461010557600080fd5b600080815480929190600190039190505550505056fea265627a7a72315820bb01cda6ba4124fde44870a05970c0990509bdf9da47ca0bc0a3f8d8be43907c64736f6c634300050c003200000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000',
                                        'name': 'unknown',
                                        'origin': '0xaffeaffeaffeaffeaffeaffeaffeaffeaffeaffe',
                                        'value': '0x0'},
                                       {'address': '0x901d12ebe1b195e5aa8748e62bd7734ae19b51f',
                                        'calldata': '0x82668f20000000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000000',
                                        'input': '0x82668f20000000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000000',
                                        'name': 'test(uint8,uint256[])',
                                        'origin': '0xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa',
                                        'value': '0x0'},
                                       {'address': '0x901d12ebe1b195e5aa8748e62bd7734ae19b51f',
                                        'calldata': '0x82668f20000000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000000',
                                        'input': '0x82668f20000000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000000',
                                        'name': 'test(uint8,uint256[])',
                                        'origin': '0xaffeaffeaffeaffeaffeaffeaffeaffeaffeaffe',
                                        'value': '0x0'}]}}],
 'success': True}

Command2 (that generates invalid txdata):

sudo docker exec CONTAINER_NAME myth analyze /tmp/test.sol --solv 0.4.25 -m integer,exceptions -o json

where the only difference is the provided --solv option.

Output2 for Command2 (simplified):

                             'steps': [{'address': '',
                                        'calldata': '0000000000000000000000000000000000000000000000000000000000000001',
                                        'input': '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',
                                        'name': 'unknown',
                                        'origin': '0xaffeaffeaffeaffeaffeaffeaffeaffeaffeaffe',
                                        'value': '0x0'},
                                       {'address': '0x901d12ebe1b195e5aa8748e62bd7734ae19b51f',
                                        'calldata': '0x82668f20666666666666666666666666666666666666666666666666666666666666660a',
                                        'input': '0x82668f20666666666666666666666666666666666666666666666666666666666666660a',
                                        'name': 'test(uint8,uint256[])',
                                        'origin': '0xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa',
                                        'value': '0x0'},
                                       {'address': '0x901d12ebe1b195e5aa8748e62bd7734ae19b51f',
                                        'calldata': '0x82668f20666666666666666666666666666666666666666666666666666666666666660a',
                                        'input': '0x82668f20666666666666666666666666666666666666666666666666666666666666660a',
                                        'name': 'test(uint8,uint256[])',
                                        'origin': '0xaffeaffeaffeaffeaffeaffeaffeaffeaffeaffe',
                                        'value': '0x0'}]}}],
 'success': True}

Expected behavior

Valid txdata should be generated for any solc.

Environment

• Mythril version: v 0.21.21 (from docker image)
• Solidity compiler and version: 0.5.12
• Python version: 3.6.9 (the one installed in the docker container)
• OS and Version: Ubuntu 18.04 (Host OS)

[norhh]

Oh! sorry about that. Mythril doesn’t 0 pad the end, that might be the problem for the error with the ABI decoder.

[SunBeomSo]

@norhh Thank you very much!