Authorization and Authentication in C++: Libraries and Implementation

Authorization and Authentication in C++: Tools Overview and Implementation

In modern C++ development, security issues are paramount. Whether you are building a server application, a desktop client, or an embedded system, authentication (verifying user identity) and authorization (verifying access rights) mechanisms are critically important. In this article, we will review the main libraries and approaches for implementing these mechanisms in C++.

Core Concepts

Before moving to the tools, it is important to distinguish between the two concepts:

• Authentication — the process of verifying that a user is who they claim to be (login + password, biometrics, token).
• Authorization — determining which resources and operations are available to an authenticated user (roles, permissions, ACL).

Libraries for Authentication in C++

1. libbcrypt — Password Hashing

For secure password storage, never use plain text or MD5. libbcrypt is a C++ implementation of the bcrypt algorithm, which is an industry standard for password hashing.

#include <bcrypt/bcrypt.h>#include <iostream>

int main() {    const char* password = "my_secure_pass123";    char salt[BCRYPT_HASHSIZE];    char hash[BCRYPT_HASHSIZE];

    // Generate salt and hash    bcrypt_gensalt(12, salt);  // 12 rounds (cost factor)    bcrypt_hashpw(password, salt, hash);

    std::cout << "Hash: " << hash << std::endl;

    // Verify password    const char* test_pass = "my_secure_pass123";    if (bcrypt_checkpw(test_pass, hash) == 0) {        std::cout << "Password is correct!" << std::endl;    } else {        std::cout << "Invalid password." << std::endl;    }    return 0;}

2. jwt-cpp — Working with JWT Tokens

JSON Web Tokens (JWT) are widely used in REST APIs for transmitting authentication data. The jwt-cpp library provides a convenient interface for creating and verifying tokens.

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

int main() {    // Create token    auto token = jwt::create()        .set_issuer("auth.myapp.com")        .set_type("JWS")        .set_payload_claim("user_id", jwt::claim(std::string("12345")))        .set_payload_claim("role", jwt::claim(std::string("admin")))        .sign(jwt::algorithm::hs256{"secret_key"});

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

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

    try {        verifier.verify(decoded);        auto user_id = decoded.get_payload_claim("user_id").as_string();        std::cout << "User ID: " << user_id << std::endl;    } catch (const std::exception& e) {        std::cerr << "Verification error: " << e.what() << std::endl;    }    return 0;}

3. cpp-httplib + OAuth2 — Authentication via Third-Party Services

To implement OAuth2 (e.g., login via Google or GitHub), a combination of an HTTP client and a JSON library is often used. cpp-httplib is a lightweight library for HTTP requests.

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

using json = nlohmann::json;

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

    // Parameters for obtaining a token (simplified)    auto res = cli.Post("/token", {        {"code", "authorization_code_from_redirect"},        {"client_id", "your_client_id"},        {"client_secret", "your_client_s