slither-read-storage: add support for `constant|immutable` variables

[backulinivan]

Describe the desired feature

It would be nice if slither-read-storage was able to output values of constant and immutable variables. This would save a lot of time by not having to look up these variables on scanners. Please see minimal code and relevant and desired log outputs.

Version

0.9.1

Minimal code to reproduce the issue

pragma solidity ^0.8.0;

contract TestConstant {
    bytes32 public constant BYTES =
        0x1111111111111111111111111111111111111111111111111111111111111111;
    address public immutable someAddress;

    uint256 public someUint256 = 3;

    constructor() {
        someAddress = 0x2222222222222222222222222222222222222222;
    }
}

then slither-read-storage TestConstant.sol --table

Relevant log output

+-------------+-------------+------+------+--------+-------+
|     name    | type_string | slot | size | offset | value |
+-------------+-------------+------+------+--------+-------+
| someUint256 |   uint256   |  0   | 256  |   0    |  None |
+-------------+-------------+------+------+--------+-------+

Suggestion for desired output

Variables' values are contracted.

+-------------+-------------+--------+------+----------+-------+
|     name    | type_string |  slot  | size |  offset  | value |
+-------------+-------------+--------+------+----------+-------+
| BYTES       |   bytes32   |  n/a   | n/a  |   n/a    |  0x1  |
| someAddress |   address   |  n/a   | n/a  |   n/a    |  0x2  |
| someUint256 |   uint256   |  0     | 256  |   0      |  None |
+-------------+-------------+--------+------+----------+-------+

[0xalpharush]

Currently we're only retrieving variables with storage slots. It would be possible to include immutable/ constants if they're public by calling the getter function. Would you be fine with not being able to retrieve private ones?

[backulinivan]

Yes, just public ones would be great.

Would it be possible for slither-read-storage to indicate that there are private|internal constant|immutable variables in a given contract? This would save so much time in case there are no private constant variables and one does not need to (semi-)manually make sure that there really are no such variables.

[montyly]

This is a great idea @backulinivan

I think we can retrieve the private ones too for immutable. Instead of calling the getter function, we can parse the runtime bytecode, and retrieve the respective values

We might be able to do the same for constant, but its going to be more tricky. Maybe by looking at the source mapping evm<>solidity?

[UVvirus]

i am working on a solution

[dokzai]

Hi @montyly

I am wondering for private immutable variables, what is the best way to parse the immutable value from the runtime bytecode (instead of contract construction)? Is there any opcode pattern that would help to identify when immutable variables get used?

[SheldonHolmgren]

I just want to bump this issue. Extracting private immutable vars from the bytecode would be an incredibly useful feature, since I don't think there is currently any tool doing that, even outside the ToB ecosystem.