declare local var.keySTRING= ...;
declare local var.ivSTRING= ...;
declare local var.ciphertextSTRING= ...;
declare local var.plaintextSTRING;
# ... unrelated calls that may produce errors ...
# Clear fastly.error before an important operation
unsetfastly.error;
set var.plaintext= crypto.decrypt_hex(aes256, cbc, nopad, var.key, var.iv, var.ciphertext);
# If fastly.error is set here, we're certain it's due to the call we're concerned with
if (fastly.error=="EBADDECRYPT") {
error403"Wrong key";
}elseif (fastly.error) {
error503;
}