recover_key in contract

Question

Is there a specific sample code of using recover_key()? I got an error with recover_key() in contract.

string msg="charlie";
checksum256 m_hash;
sha256( const_cast<char*>(msg.c_str()), msg.length(), &m_hash );
char* pub;
string sig="SIG_K1_K5cpBg7XHRfgdedEAR9w74bXQZk4TUQk9QDMfzNbttY3eZ5WhmpNuWKiRyidskkdjBH9L9pKKe29RiiELNLCNYzFtFyTqJ";
recover_key(&m_hash,sig.data(),strlen(maker.sig.data()),pub,sizeof(char));

Error Information:

assert_exception: Assert Exception
w < count():
{}
thread-0  static_variant.hpp:339 set_which
Error unpacking field _storage
{"field":"_storage"}
thread-0  raw.hpp:368 operator()
error unpacking fc::crypto::signature
{"type":"fc::crypto::signature"}
thread-0  raw.hpp:616 unpack

Answer 1

Here's one way of doing it:

#include <eosiolib/eosio.hpp>
#include <eosiolib/print.hpp>
#include <eosiolib/crypto.h>
using namespace eosio;

class ec: public eosio::contract {
  public:
      using contract::contract;

  ///@abi action
  void ecverify(std::string data, const signature &sig, const public_key &pk)
  {
    checksum256 digest;
    sha256(&data[0], data.size(), &digest);

    assert_recover_key(&digest, (const char *)&sig, sizeof(sig), (const char *)&pk, sizeof(pk));
    print("VALID");
  }
};

EOSIO_ABI( ec, (ecverify) )

Answer 2

void assert_recover_key2(const checksum256* digest, const signature* sig, const eosio::public_key* pub) {
     public_key pub2;
     pub2.data[0] = char(pub->type.value);
     memcpy(&pub2.data[1], pub->data.data(), 33);
     assert_recover_key(digest, (const char*)sig, sizeof(signature), (const char*)&pub2, sizeof(public_key));

}

that's my code, take care the public_key and eosio::public_key is not same