Authorization and Authentication in C++: Libraries, Code…

Libraries and Tools for Authorization and Authentication in C++

In modern C++ software development, user data security and access control are critical tasks. In this article, we will review the main libraries and approaches for implementing authorization and authentication in C++, including password hashing, working with JWT tokens, and OAuth2 protocol support.

1. Password Hashing: bcrypt Library (C++ wrapper)

For secure password storage in C++, it is recommended to use an adaptation of the bcrypt algorithm. The most popular implementation is libbcrypt (C++ wrapper) or using OpenSSL with a bcrypt interface. Example of hashing and verifying a password:

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

int main() {    const char* password = "mySecret123";    const char* hash = bcrypt_generate_hash(password, 12); // 12 = cost factor

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

    bool match = bcrypt_check_password(password, hash);    std::cout << "Password match: " << (match ? "true" : "false") << std::endl;

    return 0;}

Important: bcrypt automatically adds a salt and allows you to adjust the computational cost (cost factor). Never store passwords in plain text.

2. Working with JWT (JSON Web Tokens)

To implement token-based authentication in C++, use the jwt-cpp library (or libjwt). It supports HS256, RS256, and other algorithms. Example of creating and verifying a JWT:

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

int main() {    // Creating a token with HS256    auto token = jwt::create()        .set_issuer("auth.pythonlib.ru")        .set_type("JWT")        .set_payload_claim("user_id", jwt::claim(std::string("12345")))        .sign(jwt::algorithm::hs256{"secret_key"});

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

    // Verification    auto decoded = jwt::decode(token);    auto verifier = jwt::verify()        .allow_algorithm(jwt::algorithm::hs256{"secret_key"})        .with_issuer("auth.pythonlib.ru");

    try {        verifier.verify(decoded);        std::cout << "Token is valid!" << std::endl;        std::cout << "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;}

3. Authentication via OAuth2 with liboauth2

For integration with external providers (Google, GitHub, VK), use liboauth2 (C++). The library supports Authorization Code Flow and Client Credentials Flow. Example of obtaining an access token:

#include <oauth2/client>#include <iostream>

int main() {    oauth2::client client(        "your_client_id",        "your_client_secret",        "https://provider.com/oauth2/token",        "https://your-app.com/callback"    );

    // Exchange authorization code for a token    auto token = client.fetch_access_token("authorization_code_here");

    std::cout << "Access Token: " << token.access_token << std::endl;    std::cout << "Expires in: " << token.expires_in << " seconds" << std::endl;

    // Validate the token    if (client.validate_token(token)) {        std::cout << "Token is valid" << std::endl;    }

    return 0;}

4. Cryptographic Support: OpenSSL

OpenSSL is a foundational library for working with hashes (SHA-256, SHA-512), symmetric and asymmetric encryption. Example of hashing a password with a salt: