HTTPS_Client.cpp

#include <stdio.h>
#include <iostream>
#include <unistd.h>
#include <malloc.h>
#include <string.h>
#include <sys/socket.h>
#include <resolv.h>
#include <netdb.h>
#include <openssl/ssl.h>
#include <openssl/err.h>

using namespace std;

char* host;
int port;

SSL_CTX *ctx;
int client;
SSL *ssl;
int MAX_LINE = 1024;
int bytes;

void InitCTX(void) {
    const SSL_METHOD *method;
    OpenSSL_add_all_algorithms();
    SSL_load_error_strings();
    method = SSLv2_client_method();
    ctx = SSL_CTX_new(method);

    if ( ctx == NULL ) {
        ERR_print_errors_fp(stderr);
        abort();
    }
}

void ShowCerts() {
    X509 *cert;
    char *line;

    cert = SSL_get_peer_certificate(ssl);

    if ( cert != NULL ) {
        printf("Server certificates:\n");
        line = X509_NAME_oneline(X509_get_subject_name(cert), 0, 0);
        printf("Subject: %s\n", line);
        free(line);
        line = X509_NAME_oneline(X509_get_issuer_name(cert), 0, 0);
        printf("Issuer: %s\n", line);
        free(line);
        X509_free(cert);
    } else {
        printf("No certificates.\n");
    }
}

void HTTPS_disconnect() {
    close(client);
    SSL_CTX_free(ctx);
}

void HTTPS_connect() {
    InitCTX();

    client = socket(AF_INET, SOCK_STREAM, 0);

    if (static_cast<int>(client) < 0) {
        perror("socket()");
        HTTPS_disconnect();
        exit(1);
    }
    hostent *hp = gethostbyname(host);
    if (!hp) {
        cerr << "gethostbyname()" << endl;
        HTTPS_disconnect();
        exit(1);
    }
    sockaddr_in sin;
    memset((char*)&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    memcpy((char*)&sin.sin_addr, hp->h_addr, hp->h_length);
    sin.sin_port = htons(port);
    memset(&(sin.sin_zero), 0, 8 * sizeof(char));
    if (connect(client, (sockaddr*)&sin, sizeof(sin)) == -1) {
        perror("connect()");
        HTTPS_disconnect();
        exit(1);
    }
    ssl = SSL_new(ctx);
    SSL_set_fd(ssl, client);

    if (SSL_connect(ssl) == -1) {
        ERR_print_errors_fp(stderr);
    } else {
        char buf[MAX_LINE];
        const char *msg = "Hello???";

        printf("Connected with %s encryption\n", SSL_get_cipher(ssl));
        ShowCerts();
        SSL_write(ssl, msg, strlen(msg));
        bytes = SSL_read(ssl, buf, sizeof(buf));
        buf[bytes] = 0;
        printf("Received: \"%s\"\n", buf);
        SSL_free(ssl);
    }

    HTTPS_disconnect();
}

int main() {
    host = "discordapp.com";
    port = 443;

    HTTPS_connect();
}