Do SHA256 with CDT 1.6

Question

I have a problem, when I was in the 1.3 version of eosio.CDT I successfully reproduce the same SHA256 in my contract and with multiple external method.

It work like the dice contract. You generate in private a random key and his hash. You send the hash first and you validate it with the key send later.

In the table, I save the hash like this

capi_checksum256 deliveryverification;

With the update I have to do like this

checksum256 deliveryverification;

And when I'm making the verification I did like this

void rideos::orderdelive(const uint64_t orderKey, const capi_checksum256 &source)
{
auto iteratorOrder = _orders.find(orderKey);
eosio_assert(iteratorOrder != _orders.end(), "Address for order not found");

require_auth(iteratorOrder->deliver);

assert_sha256((char *)&source, sizeof(source), (const capi_checksum256 *)&iteratorOrder->deliveryverification);
}

It worked perfectly and I had the same result of the generated sha256 with bash

keyTester=$(openssl rand -hex 32)
hashTester=$(echo -n $keyTester | xxd -r -p | sha256sum -b | awk '{print $1}')

or with ecc-js

hash: ecc.sha256(new Buffer(this.state.key, 'hex'))

Now, my contract look like this

void rideos::orderdelive(const uint64_t orderKey, const string source)
{
auto iteratorOrder = _orders.find(orderKey);
check(iteratorOrder != _orders.end(), "Address for order not found");

require_auth(iteratorOrder->deliver);

eosio::print("============================\n");
eosio::print(source);
eosio::print("\n");
eosio::print(sha256((char *)source.c_str(), source.size()));
eosio::print("\n");
eosio::print(sha256(const_cast<char *>(source.c_str()), source.size()));
eosio::print("\n");
eosio::print(iteratorOrder->deliveryverification);

assert_sha256((char *)&source, sizeof(source), iteratorOrder->deliveryverification);
}

The output is : Error Details: hash mismatch pending console output: ============================ 9987ed96ebf6f52cab4fcd6f083d45793302b94c82bc359eb060e2a72d71cf61 fa41a6db58731d0d4374becc77a4e5697380027810e4a0479b40f15756d979a3 fa41a6db58731d0d4374becc77a4e5697380027810e4a0479b40f15756d979a3 a2ab06adb6e51204f60b6524b1305d62ad727d0d712b935963eba15e36f058dd

My key send is the first output and the generated sha256 in line 2-3 who should be the same than the hash line 4. In bash and with ecc I generate the same line 4 so what I missed in my contract ?

Thanks !

Answer 1

Originally, capi_checksum256 accepted hex string and converted it to binary. However, in your contract, you have changed capi_checksum256 to std::string, so the passed source argument will have ascii code of string instead of the binary that its hex string represents.

Your updated code needs to be like this:

void rideos::orderdelive(const uint64_t orderKey, const checksum256 &source) {
   auto iteratorOrder = _orders.find(orderKey);
   check(iteratorOrder != _orders.end(), "Address for order not found");

   require_auth(iteratorOrder->deliver);

   auto _source = source.extract_as_byte_array();

   assert_sha256((const char *)_source.data(), _source.size(), iteratorOrder->deliveryverification);
}

Answer 2

The result with the new implementation of sha256 is just simple than before. in ecc-js simply use :

ecc.sha256(this.state.key)

and in shell, just remove the part with xxd

keyTester=$(openssl rand -hex 32)
hashTester=$(echo -n $keyTester | sha256sum -b | awk '{print $1}')