🔧 C Code Examples

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>
#include <json-c/json.h>

#define API_KEY "your-api-key-here"
#define API_URL "http://your-domain.com/api/license/auth"
#define PRODUCT "MyCApp"
#define VERSION "1.0.0"

struct APIResponse {
    char *data;
    size_t size;
};

static size_t WriteCallback(void *contents, size_t size, size_t nmemb, struct APIResponse *response) {
    size_t realsize = size * nmemb;
    char *ptr = realloc(response->data, response->size + realsize + 1);
    
    if (ptr == NULL) return 0;
    
    response->data = ptr;
    memcpy(&(response->data[response->size]), contents, realsize);
    response->size += realsize;
    response->data[response->size] = 0;
    
    return realsize;
}

// Get hardware ID
void get_hwid(char* hwid, size_t size) {
    FILE *fp = popen("cat /proc/cpuinfo | grep 'serial' | head -n1 | cut -d: -f2 | tr -d ' \t\n'", "r");
    if (fp != NULL) {
        if (fgets(hwid, size, fp) != NULL) {
            hwid[strcspn(hwid, "\n")] = 0;
        }
        pclose(fp);
    }
    if (strlen(hwid) == 0) {
        snprintf(hwid, size, "fallback-hwid-%ld", time(NULL) % 1000000);
    }
}

// Get local IP
void get_local_ip(char* ip, size_t size) {
    FILE *fp = popen("hostname -I | awk '{print $1}'", "r");
    if (fp != NULL) {
        if (fgets(ip, size, fp) != NULL) {
            ip[strcspn(ip, "\n")] = 0;
        }
        pclose(fp);
    }
    if (strlen(ip) == 0) {
        strncpy(ip, "127.0.0.1", size - 1);
    }
}

int authenticate_license(const char* license_key) {
    CURL *curl;
    CURLcode res;
    struct APIResponse response = {0};
    struct curl_slist *headers = NULL;
    char auth_header[512];
    char json_data[1024];
    char hwid[64] = {0};
    char ip[16] = {0};
    int success = 0;
    
    get_hwid(hwid, sizeof(hwid));
    get_local_ip(ip, sizeof(ip));
    
    curl = curl_easy_init();
    if (!curl) return 0;
    
    snprintf(auth_header, sizeof(auth_header), "Authorization: %s", API_KEY);
    headers = curl_slist_append(headers, "Content-Type: application/json");
    headers = curl_slist_append(headers, auth_header);
    
    snprintf(json_data, sizeof(json_data),
        "{\"data\":{\"product\":\"%s\",\"version\":\"%s\",\"licensekey\":\"%s\",\"ip\":\"%s\",\"hwid\":\"%s\"}}",
        PRODUCT, VERSION, license_key, ip, hwid);
    
    curl_easy_setopt(curl, CURLOPT_URL, API_URL);
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, json_data);
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response);
    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 30);
    
    res = curl_easy_perform(curl);
    
    if (res == CURLE_OK) {
        long response_code;
        curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &response_code);
        
        if (response_code == 200) {
            json_object *root = json_tokener_parse(response.data);
            json_object *status_obj;
            
            if (json_object_object_get_ex(root, "status_overview", &status_obj)) {
                const char *status = json_object_get_string(status_obj);
                if (strcmp(status, "success") == 0) {
                    success = 1;
                    printf("License authenticated successfully!\n");
                    
                    json_object *username_obj;
                    if (json_object_object_get_ex(root, "discord_username", &username_obj)) {
                        printf("User: %s\n", json_object_get_string(username_obj));
                    }
                }
            }
            json_object_put(root);
        }
    }
    
    curl_slist_free_all(headers);
    curl_easy_cleanup(curl);
    if (response.data) free(response.data);
    
    return success;
}

int main() {
    char license_key[64];
    
    curl_global_init(CURL_GLOBAL_DEFAULT);
    
    printf("Enter license key: ");
    if (fgets(license_key, sizeof(license_key), stdin)) {
        license_key[strcspn(license_key, "\n")] = 0;
        
        if (authenticate_license(license_key)) {
            printf("Starting application...\n");
            // Your app logic here
        } else {
            printf("Authentication failed!\n");
            return 1;
        }
    }
    
    curl_global_cleanup();
    return 0;
}

Compilation

gcc -o app main.c -lcurl -ljson-c