Skip to main content

Step 3: Payload Validation

Now, let’s add payload validation logic to functions requiring KYC checks.

1. Add a bytes calldata _purefidata Parameter​

In the function where KYC verification is needed, add a parameter to accept the payload. The payload is encoded and signed data from PureFi, provided by the user when calling the function.

function someRestrictedFunction(address _to, bytes calldata _purefidata) external {
    // Function logic
}

2. Validate the Payload with verifier.validatePayload​

Call the validatePayload method from PureFiVerifier to verify the data. This method either succeeds or reverts if the payload is invalid.

function someRestrictedFunction(address _to, bytes calldata _purefidata) external {
    verifier.validatePayload(_purefidata);
    // Function logic after successful validation
}

The validatePayload method checks:

  • Signature validity.
  • Data freshness (timestamp).
  • Session uniqueness.
  • Issuer authorization.

If validation fails, the transaction reverts with an appropriate error.

3. (Optional) Extract Data from the Payload​

If you need to retrieve data from the payload (e.g., the sender’s address), use PureFiDataLibrary. First, import the library:

import {PureFiDataLibrary} from "./PureFi/libraries/PureFiDataLibrary.sol";

Then extract data after validation:

function someRestrictedFunction(address _to, bytes calldata _purefidata) external {
    bytes memory package = verifier.validatePayload(_purefidata);
    address from = PureFiDataLibrary.getFrom(package);
    require(from == msg.sender, "Caller must match payload sender");
    // Function logic
}

Here, getFrom extracts the sender’s address from the payload, which can be useful for additional checks.