How to transfer token and do some action inline?Or how to parse string to signature and publickey?

Question

I'm coding a contract, a game. I need players transfer some token(EOS etc.) to contract, and then, the contract will verify the signature(from player side) and insert a record into database. So I have a action to verify signature and insert a record already, I test it from commandline with parameters, like publickey and signature. It passed.

Here's my problem:

1. If player can call my contract action with some token, how should I code? Because I know the eosio.token is a system contract, so I need to set my contract to my own account, but player transfer token must call eosio.token, I don't how can I control the system contract to call my contract action.
2. I found a way by rewriting EOSIO_DISPATCH, in function "apply", I make it to call my action, it works. I write my custom parameters to "memo" in transfer action. But new problem coming, I can't parse the string which in "memo" to signature type or public_key type.

`

#undef EOSIO_DISPATCH
#define EOSIO_DISPATCH(TYPE, MEMBERS)   

                                                \
extern "C"                                                                              \
{                                                                                       \
    void apply(uint64_t receiver, uint64_t code, uint64_t action)                       \
    {                                                                                   \
        print("apply:", code, receiver, action);                                        \
        if (code == receiver)                                                           \
        {                                                                               \
            switch (action)                                                             \
            {                                                                           \
                EOSIO_DISPATCH_HELPER(TYPE, MEMBERS)                                    \
            }                                                                           \
            /* does not allow destructor of thiscontract to run: eosio_exit(0); */      \
        }                                                                               \
        else if (code == "eosio.token"_n.value && action == "transfer"_n.value)         \
        {                                                                               \
            eosio::execute_action(name(receiver), "transfer"_n, &chain_dice::transfer); \
        }                                                                               \
    }                                                                                   \
}

`

Signture(string): SIG_K1_KApZKyLzTbPYiGMPovVvWyVsLTmNJ3ucHRTWubi2DUW39qtRCEVNHDfQVGmpQ2PbAigo65mUE3fajtmp7361tYVEeCAvn8 .
Public Key(string):
EOS62M5kVouCEU31xP736Txb4pe82FoncprqevPuagE6boCLxwsC8

I need to parse to capi_signature and capi_public_key . In EOS source code, I find the parse function from string to the type, but it's in fc lib, I can't use it in contract.

//libraries/fc/include/fc/crypto/signature.hpp
signature::signature(const std::string& base58str)
      :_storage(parse_base58(base58str))
   {}

//libraries/fc/include/fc/crypto/public_key.hpp
explicit public_key(const string& base58str);

Please help me.

Answer 1

One day I was looking for a function sha256_to_hex, but I surprisingly find a utils.hpp in github, this code has the functions I need and more, it has the functions that can parse string signature and string publickey!!

I modified the code that can be compiled by eosio.cdt 1.3+ . Here's the code:

#include <eosiolib/crypto.h>
#include <eosiolib/asset.hpp>
#include <eosiolib/eosio.hpp>
#include <eosiolib/singleton.hpp>
#include <eosiolib/time.hpp>
#include <eosiolib/types.h>

using namespace eosio;
using namespace std;

string uint64_string(uint64_t input) {
    string result;
    uint8_t base = 10;
    do {
        char c = input % base;
        input /= base;
        if (c < 10)
            c += '0';
        else
            c += 'A' - 10;
        result = c + result;
    } while (input);
    return result;
}

uint8_t from_hex(char c) {
    if (c >= '0' && c <= '9') return c - '0';
    if (c >= 'a' && c <= 'f') return c - 'a' + 10;
    if (c >= 'A' && c <= 'F') return c - 'A' + 10;
    eosio_assert(false, "Invalid hex character");
    return 0;
}

size_t from_hex(const string& hex_str, char* out_data, size_t out_data_len) {
    auto i = hex_str.begin();
    uint8_t* out_pos = (uint8_t*)out_data;
    uint8_t* out_end = out_pos + out_data_len;
    while (i != hex_str.end() && out_end != out_pos) {
        *out_pos = from_hex((char)(*i)) << 4;
        ++i;
        if (i != hex_str.end()) {
            *out_pos |= from_hex((char)(*i));
            ++i;
        }
        ++out_pos;
    }
    return out_pos - (uint8_t*)out_data;
}

string to_hex(const char* d, uint32_t s) {
    std::string r;
    const char* to_hex = "0123456789abcdef";
    uint8_t* c = (uint8_t*)d;
    for (uint32_t i = 0; i < s; ++i)
        (r += to_hex[(c[i] >> 4)]) += to_hex[(c[i] & 0x0f)];
    return r;
}

string sha256_to_hex(const capi_checksum256& sha256) {
    return to_hex((char*)sha256.hash, sizeof(sha256.hash));
}

string sha1_to_hex(const capi_checksum160& sha1) {
    return to_hex((char*)sha1.hash, sizeof(sha1.hash));
}

// copied from boost https://www.boost.org/
template <class T>
inline void hash_combine(std::size_t& seed, const T& v) {
    std::hash<T> hasher;
    seed ^= hasher(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
}

uint64_t uint64_hash(const string& hash) {
    return std::hash<string>{}(hash);
}

uint64_t uint64_hash(const capi_checksum256& hash) {
    return uint64_hash(sha256_to_hex(hash));
}

capi_checksum256 hex_to_sha256(const string& hex_str) {
    eosio_assert(hex_str.length() == 64, "invalid sha256");
    capi_checksum256 checksum;
    from_hex(hex_str, (char*)checksum.hash, sizeof(checksum.hash));
    return checksum;
}

capi_checksum160 hex_to_sha1(const string& hex_str) {
    eosio_assert(hex_str.length() == 40, "invalid sha1");
    capi_checksum160 checksum;
    from_hex(hex_str, (char*)checksum.hash, sizeof(checksum.hash));
    return checksum;
}

size_t sub2sep(const string& input,
               string* output,
               const char& separator,
               const size_t& first_pos = 0,
               const bool& required = false) {
    eosio_assert(first_pos != string::npos, "invalid first pos");
    auto pos = input.find(separator, first_pos);
    if (pos == string::npos) {
        eosio_assert(!required, "parse memo error");
        return string::npos;
    }
    *output = input.substr(first_pos, pos - first_pos);
    return pos;
}

// Copied from https://github.com/bitcoin/bitcoin

/** All alphanumeric characters except for "0", "I", "O", and "l" */
static const char* pszBase58 =
    "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
static const int8_t mapBase58[256] = {
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0,  1,  2,  3,  4,  5,  6,  7,
    8,  -1, -1, -1, -1, -1, -1, -1, 9,  10, 11, 12, 13, 14, 15, 16, -1, 17, 18,
    19, 20, 21, -1, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, -1, -1, -1, -1,
    -1, -1, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, -1, 44, 45, 46, 47, 48,
    49, 50, 51, 52, 53, 54, 55, 56, 57, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1,
};

bool DecodeBase58(const char* psz, std::vector<unsigned char>& vch) {
    // Skip leading spaces.
    while (*psz && isspace(*psz)) psz++;
    // Skip and count leading '1's.
    int zeroes = 0;
    int length = 0;
    while (*psz == '1') {
        zeroes++;
        psz++;
    }
    // Allocate enough space in big-endian base256 representation.
    int size = strlen(psz) * 733 / 1000 + 1;  // log(58) / log(256), rounded up.
    std::vector<unsigned char> b256(size);
    // Process the characters.
    static_assert(
        sizeof(mapBase58) / sizeof(mapBase58[0]) == 256,
        "mapBase58.size() should be 256");  // guarantee not out of range
    while (*psz && !isspace(*psz)) {
        // Decode base58 character
        int carry = mapBase58[(uint8_t)*psz];
        if (carry == -1)  // Invalid b58 character
            return false;
        int i = 0;
        for (std::vector<unsigned char>::reverse_iterator it = b256.rbegin();
             (carry != 0 || i < length) && (it != b256.rend());
             ++it, ++i) {
            carry += 58 * (*it);
            *it = carry % 256;
            carry /= 256;
        }
        assert(carry == 0);
        length = i;
        psz++;
    }
    // Skip trailing spaces.
    while (isspace(*psz)) psz++;
    if (*psz != 0) return false;
    // Skip leading zeroes in b256.
    std::vector<unsigned char>::iterator it = b256.begin() + (size - length);
    while (it != b256.end() && *it == 0) it++;
    // Copy result into output vector.
    vch.reserve(zeroes + (b256.end() - it));
    vch.assign(zeroes, 0x00);
    while (it != b256.end()) vch.push_back(*(it++));
    return true;
}

bool decode_base58(const string& str, vector<unsigned char>& vch) {
    return DecodeBase58(str.c_str(), vch);
}

// Copied from https://github.com/bitcoin/bitcoin

capi_signature str_to_sig(const string& sig, const bool& checksumming = true) {
    const auto pivot = sig.find('_');
    eosio_assert(pivot != string::npos, "No delimiter in signature");
    const auto prefix_str = sig.substr(0, pivot);
    eosio_assert(prefix_str == "SIG", "Signature Key has invalid prefix");
    const auto next_pivot = sig.find('_', pivot + 1);
    eosio_assert(next_pivot != string::npos, "No curve in signature");
    const auto curve = sig.substr(pivot + 1, next_pivot - pivot - 1);
    eosio_assert(curve == "K1" || curve == "R1", "Incorrect curve");
    const bool k1 = curve == "K1";
    auto data_str = sig.substr(next_pivot + 1);
    eosio_assert(!data_str.empty(), "Signature has no data");
    vector<unsigned char> vch;

    eosio_assert(decode_base58(data_str, vch), "Decode signature failed");

    eosio_assert(vch.size() == 69, "Invalid signature");

    if (checksumming) {
        array<unsigned char, 67> check_data;
        copy_n(vch.begin(), 65, check_data.begin());
        check_data[65] = k1 ? 'K' : 'R';
        check_data[66] = '1';

        capi_checksum160 check_sig;
        ripemd160(reinterpret_cast<char*>(check_data.data()), 67, &check_sig);

        eosio_assert(memcmp(&check_sig.hash, &vch.end()[-4], 4) == 0, "Signature checksum mismatch");
    }

    capi_signature _sig;
    unsigned int type = k1 ? 0 : 1;
    _sig.data[0] = (uint8_t)type;
    for (int i = 1; i < sizeof(_sig.data); i++) {
        _sig.data[i] = vch[i - 1];
    }
    return _sig;
}

capi_public_key str_to_pub(const string& pubkey, const bool& checksumming = true) {
    string pubkey_prefix("EOS");
    auto base58substr = pubkey.substr(pubkey_prefix.length());
    vector<unsigned char> vch;
    eosio_assert(decode_base58(base58substr, vch), "Decode public key failed");
    eosio_assert(vch.size() == 37, "Invalid public key");
    if (checksumming) {

        array<unsigned char, 33> pubkey_data;
        copy_n(vch.begin(), 33, pubkey_data.begin());

        capi_checksum160 check_pubkey;
        ripemd160(reinterpret_cast<char*>(pubkey_data.data()), 33, &check_pubkey);

        eosio_assert(memcmp(&check_pubkey, &vch.end()[-4], 4) == 0, "Public key checksum mismatch");
    }
    capi_public_key _pub_key;
    unsigned int type = 0;
    _pub_key.data[0] = (char)type;
    for (int i = 1; i < sizeof(_pub_key.data); i++) {
        _pub_key.data[i] = vch[i - 1];
    }
    return _pub_key;
}

In this code file, you can find two functions, str_to_sig and str_to_pub, these are the functions in EOS source code. I can parse string signature and string publickey to capi_signature and capi_public_key, then verify the signature.

ACTION test()
    {
        capi_checksum256 digest = hex_to_sha256("9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08");
        capi_signature sig = str_to_sig("SIG_K1_KkSbKuDSV7x87FeexJ3goinHsd3MhPBCH91MRqhyS3Z7H1v4HtUZoJc6AkgYWW5mEan7UbdmDAzDpCzUwheDPxRxtzuD8s");
        capi_public_key pk = str_to_pub("EOS62M5kVouCEU31xP736Txb4pe82FoncprqevPuagE6boCLxwsC8");

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