Authorization and Authentication in C++: Libraries and…

Introduction to Authentication and Authorization in C++

Authentication (verifying user identity) and authorization (checking access rights) are key security components of any modern application. In C++, these tasks are solved using specialized libraries that allow implementing support for JWT tokens, OAuth 2.0, password hashing, and session management. In this article, we will review the main tools, their installation, and usage examples.

Main Libraries for Authentication in C++

1. JWT-CPP — Working with JSON Web Tokens

JWT-CPP is a lightweight library for creating and verifying JWT tokens. It supports HMAC, RSA, and ECDSA algorithms. It is ideal for REST APIs and microservices.

Installation:

git clone https://github.com/Thalhammer/jwt-cppcd jwt-cppmkdir build && cd buildcmake ..make && make install

Example of creating and verifying a token:

#include <jwt-cpp/jwt.h>#include <iostream>

int main() {    // Creating a token with payload    auto token = jwt::create()        .set_issuer("auth.example.com")        .set_type("JWS")        .set_payload_claim("user_id", jwt::claim(std::string("12345")))        .sign(jwt::algorithm::hs256{"secret_key"});

    std::cout << "Token: " << token << std::endl;

    // Verifying the token    auto decoded = jwt::decode(token);    auto verifier = jwt::verify()        .allow_algorithm(jwt::algorithm::hs256{"secret_key"})        .with_issuer("auth.example.com");

    try {        verifier.verify(decoded);        std::cout << "Token valid. User ID: "                   << decoded.get_payload_claim("user_id").as_string()                   << std::endl;    } catch (const std::exception& e) {        std::cerr << "Invalid token: " << e.what() << std::endl;    }    return 0;}

2. bcrypt-cpp — Password Hashing

The bcrypt-cpp library provides secure password hashing using the Blowfish algorithm. It includes automatic salt generation and protection against brute-force attacks.

Usage example:

#include <bcrypt/BCrypt.hpp>#include <iostream>

int main() {    std::string password = "SuperSecret123!";

    // Hashing the password    std::string hash = BCrypt::generateHash(password);    std::cout << "Hash: " << hash << std::endl;

    // Verifying the password    if (BCrypt::validatePassword(password, hash)) {        std::cout << "Password correct!" << std::endl;    } else {        std::cout << "Invalid password." << std::endl;    }    return 0;}

3. OAuth2 Client — Integration with Providers

To implement login via Google, GitHub, or Facebook, use the cpp-httplib library in conjunction with manual handling of OAuth2 flows. An example of obtaining an access token via HTTP requests:

#include <httplib.h>#include <nlohmann/json.hpp>#include <iostream>

int main() {    httplib::Client cli("https://oauth2.googleapis.com");

    // Request parameters (replace with your own)    auto res = cli.Post("/token", {        {"code", "authorization_code"},        {"client_id", "YOUR_CLIENT_ID"},        {"client_secret", "YOUR_CLIENT_SECRET"},        {"redirect_uri", "http://localhost:8080/callback"},        {"grant_type", "authorization_code"}    });

    if (res && res->status == 200) {        auto json = nlohmann::json::parse(res->body);        std::cout << "Access token: "                   << json["access_token"].get<std::string>()                   << std::endl;    } else {        std::cerr << "Failed to get token" << std::endl;    }    return 0;}