signature_2.cairo

%lang starknet

from starkware.cairo.common.cairo_builtins import HashBuiltin, SignatureBuiltin
from starkware.starknet.common.syscalls import call_contract, get_tx_info
from starkware.cairo.common.signature import verify_ecdsa_signature
from starkware.cairo.common.alloc import alloc

####################
# STORAGE VARIABLES
####################
@storage_var
func public_key() -> (res : felt):
end

####################
# CONSTRUCTOR
####################
@constructor
func constructor{syscall_ptr : felt*, pedersen_ptr : HashBuiltin*, range_check_ptr}(pub_key : felt):
    public_key.write(pub_key)
    return ()
end

####################
# GETTERS
####################
#
# ACTION ITEM 1: verify the provided signature with std library `verify_ecdsa_signature`
# - reference: https://github.com/starkware-libs/cairo-lang/blob/master/src/starkware/cairo/common/signature.cairo
#
@view
func is_valid_signature{
    syscall_ptr : felt*, pedersen_ptr : HashBuiltin*, range_check_ptr, ecdsa_ptr : SignatureBuiltin*
}(hash : felt, signature_len : felt, signature : felt*) -> ():
    let (_public_key) = public_key.read()

    #
    # <CODE>
    #

    return ()
end

####################
# EXTERNAL FUNCTIONS
####################
@external
func __execute__{syscall_ptr : felt*, pedersen_ptr : HashBuiltin*, range_check_ptr}(
    contract_address : felt, selector : felt, calldata_len : felt, calldata : felt*
) -> (retdata_len : felt, retdata : felt*):
    let (tx_info) = get_tx_info()

    let (vec : felt*) = alloc()
    assert [vec] = calldata[0]
    assert [vec + 1] = tx_info.signature[0]
    assert [vec + 2] = tx_info.signature[1]
    assert [vec + 3] = calldata[2]

    let (retdata_len : felt, retdata : felt*) = call_contract(
        contract_address=contract_address, function_selector=selector, calldata_size=4, calldata=vec
    )

    return (retdata_len=retdata_len, retdata=retdata)
end