// g++ -Wall -Wextra -Wconversion -g3 -std=c++11 openssl-test.cpp -o openssl-test.exe -lssl -lcrypto

#include <iostream>
using std::cout;
using std::cerr;
using std::endl;

#include <string>
using std::string;

#include <memory>
using std::unique_ptr;

#include <openssl/bn.h>
#include <openssl/rsa.h>
#include <openssl/evp.h>
#include <openssl/err.h>

const char nz[] =
    "20446702916744654562596343388758805860065209639960173505037453331270270518732245"
    "08977372301204320323609709562340204469011575537734525469644875960570778896584888"
    "95017468362112062706438336639499925362469853626937363871851454247879222415857219"
    "92924045675229348655595626434390043002821512765630397723028023792577935108185822"
    "75369257422156693093780503115582009714681996492027000881132703628678639279359312"
    "17624250488602118597634417704467037220158572506211078553986931332640811506974231"
    "88751482418465308470313958250757758547155699749157985955379381294962058862159085"
    "915015369381046959790476428631998204940879604226680285601";

const char ez[] = "65537";

const char dz[] =
    "23583109899396195101799862623499368829246520235662137651186064319555667005065389"
    "11356936879137503597382515919515633242482643314423192704128296593672966061810149"
    "31632061789402182278402640746140338406535182197235078430096761014345948432406842"
    "76746396884059179774424728049430754391920261073195321175575450790865379829879825"
    "22396626690057355718157403493216553255260857777965627529169195827622139772389760"
    "13057175483467867984218114225248961766503010944557397801270779301059273764049922"
    "00150833924259148778478404572782464027609558833769999511998277062853834711506435"
    "61410605789710883438795588594095047409018233862167884701";

const char pz[] =
    "15737705590244743839558616502896029191493197327877753279847020015603526753735923"
    "90718294084119093232085749598005372477289597182368848096852332845373492076546615"
    "30801859889389455120932077199406250387226339056140578989122526711937239401762061"
    "949364440402067108084155200696015505170135950332209194782224750221639";

const char qz[] =
    "12992175256740635899099334754006444501823007340248226099417932857332386190837921"
    "12746269565434716649972371852989646481333243433270528522640603220881224011247812"
    "49085873464824282666514908127141915943024862618996371026577302203267804867959037"
    "802770797169483022132210859867700312376409633383772189122488119155159";

const char dmodp1z[] =
    "49227606481837320706006017716613302169096929249354401671859241393391870004972220"
    "28735680413269055839870281941362914961691371628021024152077883230870590287807744"
    "29930898230386473286709428656763070164661176228829801375865815889453805901417866"
    "2376933683632720014228880806671525788467258162275185762295508460173";

const char dmodq1z[] =
    "95501022448116849078110281587424883261489167280943290677534750975651978631525094"
    "58693377793498640446735285662438504904366643141183520919433056069507619439072908"
    "27084374978171871336296929080814602230691019089602999501706662853078906832637851"
    "45958472051553704139602453015343925544671829327400421727981791235189";

const char invqmodpz[] =
    "23545019917990284444784037831882732213707743418529123971725460465297450415859883"
    "70728413617913564636615863358005459444719505281341294577593327462082221309955672"
    "00897700599820911444355459765155081084657241882422419679677095553363318743253968"
    "76783846248039429242763646988988076187339075374375350105207330456437";

using BN_ptr = std::unique_ptr<BIGNUM, decltype(&::BN_free)>;
using RSA_ptr = std::unique_ptr<RSA, decltype(&::RSA_free)>;
using EVP_PKEY_ptr = std::unique_ptr<EVP_PKEY, decltype(&::EVP_PKEY_free)>;
using EVP_MD_CTX_ptr = std::unique_ptr<EVP_MD_CTX, decltype(&::EVP_MD_CTX_destroy)>;

#define UNUSED(x) ((void)x)

int main(int argc, char* argv[])
{
    UNUSED(argc); UNUSED(argv);

    int rc;
    long err;

    RSA_ptr rsa(RSA_new(), ::RSA_free);
    BIGNUM *n = NULL, *e = NULL, *d = NULL, *p = NULL, *q = NULL, *dmodp1 = NULL, *dmodq1 = NULL, *invqmodp = NULL;

    rc = BN_dec2bn(&n, nz);
    if(rc == 0 || n == NULL) {
        cerr << "BN_dec2bn failed for n" << endl;
        exit(1);
    }
    rsa->n = n; n = NULL;

    rc = BN_dec2bn(&e, ez);
    if(rc == 0 || e == NULL) {
        cerr << "BN_dec2bn failed for e" << endl;
        exit(1);
    }
    rsa->e = e; e = NULL;

    rc = BN_dec2bn(&d, dz);
    if(rc == 0 || d == NULL) {
        cerr << "BN_dec2bn failed for d" << endl;
        exit(1);
    }
    rsa->d = d; d = NULL;

    rc = BN_dec2bn(&p, pz);
    if(rc == 0 || p == NULL) {
        cerr << "BN_dec2bn failed for p" << endl;
        exit(1);
    }
    rsa->p = p; p = NULL;

    rc = BN_dec2bn(&q, qz);
    if(rc == 0 || q == NULL) {
        cerr << "BN_dec2bn failed for q" << endl;
        exit(1);
    }
    rsa->q = q; q = NULL;

    rc = BN_dec2bn(&dmodp1, dmodp1z);
    if(rc == 0 || dmodp1 == NULL) {
        cerr << "BN_dec2bn failed for dmodp1" << endl;
        exit(1);
    }
    rsa->dmp1 = dmodp1; dmodp1 = NULL;

    rc = BN_dec2bn(&dmodq1, dmodq1z);
    if(rc == 0 || dmodq1 == NULL) {
        cerr << "BN_dec2bn failed for dmodq1" << endl;
        exit(1);
    }
    rsa->dmq1 = dmodq1; dmodq1 = NULL;

    rc = BN_dec2bn(&invqmodp, invqmodpz);
    if(rc == 0 || invqmodp == NULL) {
        cerr << "BN_dec2bn failed for invpmodq" << endl;
        exit(1);
    }
    rsa->iqmp = invqmodp; invqmodp = NULL;

    rc = RSA_check_key(rsa.get());
    err = ERR_get_error();
    if(rc != 1) {
        cerr << "RSA_check_key failed, error 0x" << std::hex << err << endl;
        exit(1);
    }

    EVP_PKEY_ptr pkey(EVP_PKEY_new(), ::EVP_PKEY_free);

    rc = EVP_PKEY_set1_RSA(pkey.get(), rsa.get());
    err = ERR_get_error();
    if(rc != 1) {
        cerr << "EVP_PKEY_set1_RSA failed, error 0x" << std::hex << err << endl;
        exit(1);
    }

    EVP_MD_CTX_ptr ctx(EVP_MD_CTX_create(), ::EVP_MD_CTX_destroy);
    EVP_MD_CTX_init(ctx.get());

    const EVP_MD* md = EVP_sha256();
    rc = EVP_SignInit(ctx.get(), md);
    err = ERR_get_error();
    if(rc != 1) {
        cerr << "EVP_SignInit_ex failed, error 0x" << std::hex << err << endl;
        exit(1);
    }

    const char message[] = "Now is the time for all good men...";
    rc = EVP_SignUpdate(ctx.get(), message, (unsigned int)sizeof(message));
    err = ERR_get_error();
    if(rc != 1) {
        cerr << "EVP_SignUpdate failed, error 0x" << std::hex << err << endl;
        exit(1);
    }

    const unsigned int req = std::max(EVP_MD_size(md), EVP_PKEY_size(pkey.get()));
    unique_ptr<unsigned char[]> signature(new unsigned char[req]);
    unsigned int size = req;

    rc = EVP_SignFinal(ctx.get(), signature.get(), &size, pkey.get());
    err = ERR_get_error();
    if(rc != 1) {
        cerr << "EVP_SignFinal failed, error 0x" << std::hex << err << endl;
        exit(1);
    }

    size = std::min(size, (unsigned int)EVP_MD_size(md));
    cout << "Signature: ";

    for(unsigned i = 0; i < size; i++)
        cout << std::hex << (signature[i] & 0xFF);
    cout << endl;

    return 0;
}