FT4 Library/lib.ft4.core.auth/_auth_handler

_auth_handler

An auth handler defines who can and should call a specific operation. A new auth handler should be defined for each operation in the dapp.

Properties

flags

val flags: list<text>

The flags an auth descriptor should have to be authorized to call this operation. In this way, access levels can be defined, and a function can be setup in a way that calling it requires special permissions.

By default, two flags are defined in FT4 operations:

T - Transfer. Everything that requires transferring assets requires this flag.
A - Account. Everything that modifies the account and its auth descriptors requires this flag

If multiple flags appear here, an auth descriptor is required to have them all to be able to call the operation.

No flags means any auth descriptor can be used.

The resolver field of the auth handler might partially or completely override this field.

message_formatter

val message_formatter: (gtv) -> text? = null

A function that receives the the arguments of the operation and returns a message that should be signed if the signer that is authorizing is an EVM signer.

This text will thus appear on the EVM wallet of the user to approve the operation.

If null, a default message will be created by generate_operation_auth_message. It is suggested to only use the default messages in development environments.

An example function that could be used as a message formatter is:

operation send_chroma_tokens (amount: big_integer, account) { ... }

function message_formatter_for_send_chroma_tokens (gtv) {
    val params = struct<send_chroma_tokens>.from_gtv(gtv);
    return "Do you want to send %s CHR to account %s?".format(
        params.amount,
        params.account
    );
}

The function can be as complex or simple as needed, and it can as well make no use of the gtv parameters by returning a default message in all cases - the message will have a nonce that prevents replay attacks.

resolver

val resolver: (gtv, byte_array, list<byte_array>) -> byte_array?? = null

Either null, or a function that receives:

the arguments of the operation
the account ID
a list of auth descriptor IDs and returns the ID of the auth descriptor that should be used to authorize the operation, or null if none is acceptable.

If this function is defined, it will be called by the client to pick the best auth descriptor to use between the ones that are available.

If flags is not an empty list, it will be used to preselect which auth descriptors to pass to the resolver - otherwise, all auth descriptors can be passed, and the resolver could manually check flags if needed.

This behavior allows the resolver to define cases in which one of the auth descriptors could call a certain operation with some flags, while a different auth descriptor needs a different flag to call the same operation.

_auth_handler

See also

Properties