backend/src/main/java/de/szut/casino/CasinoApplication.java

@@ -8,9 +8,6 @@ import org.springframework.boot.CommandLineRunner;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.context.annotation.Bean;
-import org.springframework.mail.MailException;
-import org.springframework.mail.MailSender;
-import org.springframework.mail.SimpleMailMessage;
 import org.springframework.mail.javamail.JavaMailSenderImpl;
 import org.springframework.web.client.RestTemplate;
 

backend/src/main/java/de/szut/casino/blackjack/BlackJackService.java

@@ -112,7 +112,7 @@ public class BlackJackService {
         dealCardToPlayer(game);
         dealCardToSplitHand(game);
 
-        return blackJackGameRepository.save(game);
+        return processGameBasedOnState(game);
     }
 
     private BlackJackGameEntity processGameBasedOnState(BlackJackGameEntity game) {

backend/src/main/java/de/szut/casino/config/OpenAPIConfiguration.java

@@ -1,7 +1,6 @@
 package de.szut.casino.config;
 
 
-
 import io.swagger.v3.oas.models.Components;
 import io.swagger.v3.oas.models.OpenAPI;
 import io.swagger.v3.oas.models.info.Info;

backend/src/main/java/de/szut/casino/config/WebConfig.java

@@ -18,12 +18,12 @@ public class WebConfig {
             @Override
             public void addCorsMappings(CorsRegistry registry) {
                 registry.addMapping("/**")
-                    .allowedOrigins(frontendHost)
+                        .allowedOrigins(frontendHost)
-                    .allowedMethods("GET", "POST", "PUT", "DELETE", "OPTIONS")
+                        .allowedMethods("GET", "POST", "PUT", "DELETE", "OPTIONS")
-                    .allowedHeaders("*")
+                        .allowedHeaders("*")
-                    .exposedHeaders("*")
+                        .exposedHeaders("*")
-                    .allowCredentials(true)
+                        .allowCredentials(true)
-                    .maxAge(3600);
+                        .maxAge(3600);
             }
         };
     }

backend/src/main/java/de/szut/casino/deposit/DepositController.java

@@ -53,8 +53,8 @@ public class DepositController {
                                 .build())
                         .setQuantity(1L)
                         .build())
-                .setSuccessUrl(frontendHost+"/home?success=true")
+                .setSuccessUrl(frontendHost + "/home?success=true")
-                .setCancelUrl(frontendHost+"/home?success=false")
+                .setCancelUrl(frontendHost + "/home?success=false")
                 .setMode(SessionCreateParams.Mode.PAYMENT)
                 .build();
 

backend/src/main/java/de/szut/casino/exceptionHandling/exceptions/EmailNotVerifiedException.java

@@ -1,7 +1,5 @@
 package de.szut.casino.exceptionHandling.exceptions;
 
-import de.szut.casino.security.service.EmailService;
-
 public class EmailNotVerifiedException extends Exception {
     public EmailNotVerifiedException() {
         super("Email not verified");

backend/src/main/java/de/szut/casino/exceptionHandling/exceptions/OAuth2AuthenticationProcessingException.java

@@ -0,0 +1,9 @@
+package de.szut.casino.exceptionHandling.exceptions;
+
+import org.springframework.security.core.AuthenticationException;
+
+public class OAuth2AuthenticationProcessingException extends AuthenticationException {
+    public OAuth2AuthenticationProcessingException(String msg) {
+        super(msg);
+    }
+}

backend/src/main/java/de/szut/casino/security/AuthController.java

@@ -1,6 +1,5 @@
 package de.szut.casino.security;
 
-import de.szut.casino.exceptionHandling.ErrorDetails;
 import de.szut.casino.exceptionHandling.exceptions.EmailNotVerifiedException;
 import de.szut.casino.security.dto.AuthResponseDto;
 import de.szut.casino.security.dto.LoginRequestDto;
@@ -15,12 +14,12 @@ import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
 
 import java.io.IOException;
-import java.util.Date;
 
 @RestController
 @RequestMapping("/auth")
 public class AuthController {
 
+
     @Autowired
     private AuthService authService;
 
@@ -38,11 +37,11 @@ public class AuthController {
 
     @PostMapping("/verify")
     public ResponseEntity<Void> verifyEmail(@RequestParam("token") String token) throws MessagingException, IOException {
-         if (authService.verifyEmail(token)) {
+        if (authService.verifyEmail(token)) {
-             return ResponseEntity.badRequest().build();
+            return ResponseEntity.badRequest().build();
-         }
+        }
 
-         return ResponseEntity.ok().build();
+        return ResponseEntity.ok().build();
     }
 
     @PostMapping("/recover-password")

backend/src/main/java/de/szut/casino/security/CorsFilter.java

@@ -19,23 +19,22 @@ public class CorsFilter implements Filter {
 
     @Override
     public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
-        
+
         HttpServletResponse response = (HttpServletResponse) res;
         HttpServletRequest request = (HttpServletRequest) req;
-        
+
-        // Allow requests from the frontend
         response.setHeader("Access-Control-Allow-Origin", frontendHost);
         response.setHeader("Access-Control-Allow-Methods", "GET, POST, PUT, PATCH, DELETE, OPTIONS");
         response.setHeader("Access-Control-Allow-Headers", "*");
         response.setHeader("Access-Control-Expose-Headers", "*");
         response.setHeader("Access-Control-Allow-Credentials", "true");
         response.setHeader("Access-Control-Max-Age", "3600");
-        
+
         if ("OPTIONS".equalsIgnoreCase(request.getMethod())) {
             response.setStatus(HttpServletResponse.SC_OK);
             return;
         }
-        
+
         chain.doFilter(req, res);
     }
 }

backend/src/main/java/de/szut/casino/security/CustomJwtAuthenticationConverter.java

@@ -7,7 +7,7 @@ import org.springframework.security.oauth2.server.resource.authentication.JwtAut
 import org.springframework.security.oauth2.server.resource.authentication.JwtGrantedAuthoritiesConverter;
 
 public class CustomJwtAuthenticationConverter implements Converter<Jwt, AbstractAuthenticationToken> {
-    
+
     @Override
     public AbstractAuthenticationToken convert(Jwt source) {
         JwtGrantedAuthoritiesConverter authoritiesConverter = new JwtGrantedAuthoritiesConverter();

backend/src/main/java/de/szut/casino/security/GitHubController.java

@@ -0,0 +1,49 @@
+package de.szut.casino.security;
+
+import de.szut.casino.security.dto.AuthResponseDto;
+import de.szut.casino.security.dto.GithubCallbackDto;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+import org.springframework.web.servlet.view.RedirectView;
+
+@RestController
+@RequestMapping("/oauth2/github")
+public class GitHubController {
+    private static final Logger logger = LoggerFactory.getLogger(GitHubController.class);
+
+    @Value("${spring.security.oauth2.client.registration.github.client-id}")
+    private String clientId;
+
+    @Value("${spring.security.oauth2.client.provider.github.authorization-uri}")
+    private String authorizationUri;
+
+    @Value("${spring.security.oauth2.client.registration.github.redirect-uri}")
+    private String redirectUri;
+
+    @Autowired
+    private GitHubService githubService;
+
+    @GetMapping("/authorize")
+    public RedirectView authorizeGithub() {
+        logger.info("Redirecting to GitHub for authorization");
+
+        String authUrl = authorizationUri +
+                "?client_id=" + clientId +
+                "&redirect_uri=" + redirectUri +
+                "&scope=user:email,read:user";
+
+        return new RedirectView(authUrl);
+    }
+
+
+    @PostMapping("/callback")
+    public ResponseEntity<AuthResponseDto> githubCallback(@RequestBody GithubCallbackDto githubCallbackDto) {
+        String code = githubCallbackDto.getCode();
+        AuthResponseDto response = githubService.processGithubCode(code);
+        return ResponseEntity.ok(response);
+    }
+}

backend/src/main/java/de/szut/casino/security/GitHubService.java

@@ -0,0 +1,165 @@
+package de.szut.casino.security;
+
+import de.szut.casino.security.dto.AuthResponseDto;
+import de.szut.casino.security.jwt.JwtUtils;
+import de.szut.casino.user.AuthProvider;
+import de.szut.casino.user.UserEntity;
+import de.szut.casino.user.UserRepository;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.http.HttpEntity;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.authentication.AuthenticationManager;
+import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
+import org.springframework.security.core.Authentication;
+import org.springframework.security.crypto.password.PasswordEncoder;
+import org.springframework.stereotype.Service;
+import org.springframework.web.client.RestTemplate;
+
+import java.math.BigDecimal;
+import java.util.*;
+
+@Service
+public class GitHubService {
+    @Value("${spring.security.oauth2.client.registration.github.client-id}")
+    private String clientId;
+
+    @Value("${spring.security.oauth2.client.registration.github.client-secret}")
+    private String clientSecret;
+
+    @Autowired
+    private AuthenticationManager authenticationManager;
+
+    @Autowired
+    private UserRepository userRepository;
+
+    @Autowired
+    private JwtUtils jwtUtils;
+
+    @Autowired
+    private PasswordEncoder oauth2PasswordEncoder;
+
+    public AuthResponseDto processGithubCode(String code) {
+        try {
+            RestTemplate restTemplate = new RestTemplate();
+
+            Map<String, String> requestBody = new HashMap<>();
+            requestBody.put("client_id", clientId);
+            requestBody.put("client_secret", clientSecret);
+            requestBody.put("code", code);
+
+            HttpHeaders headers = new HttpHeaders();
+            headers.set("Accept", "application/json");
+
+            HttpEntity<Map<String, String>> requestEntity = new HttpEntity<>(requestBody, headers);
+
+            ResponseEntity<Map> response = restTemplate.exchange(
+                    "https://github.com/login/oauth/access_token",
+                    HttpMethod.POST,
+                    requestEntity,
+                    Map.class
+            );
+
+            Map<String, Object> responseBody = response.getBody();
+
+            if (responseBody.containsKey("error")) {
+                String error = (String) responseBody.get("error");
+                String errorDescription = (String) responseBody.get("error_description");
+
+                throw new RuntimeException("GitHub OAuth error: " + errorDescription);
+            }
+
+            String accessToken = (String) responseBody.get("access_token");
+            if (accessToken == null || accessToken.isEmpty()) {
+
+                throw new RuntimeException("Failed to receive access token from GitHub");
+            }
+
+            HttpHeaders userInfoHeaders = new HttpHeaders();
+            userInfoHeaders.set("Authorization", "Bearer " + accessToken);
+
+            HttpEntity<String> userInfoRequestEntity = new HttpEntity<>(null, userInfoHeaders);
+
+            ResponseEntity<Map> userResponse = restTemplate.exchange(
+                    "https://api.github.com/user",
+                    HttpMethod.GET,
+                    userInfoRequestEntity,
+                    Map.class
+            );
+
+            Map<String, Object> userAttributes = userResponse.getBody();
+
+            HttpHeaders emailsHeaders = new HttpHeaders();
+            emailsHeaders.set("Authorization", "Bearer " + accessToken);
+
+            HttpEntity<String> emailsRequestEntity = new HttpEntity<>(null, emailsHeaders);
+
+            ResponseEntity<List> emailsResponse = restTemplate.exchange(
+                    "https://api.github.com/user/emails",
+                    HttpMethod.GET,
+                    emailsRequestEntity,
+                    List.class
+            );
+
+            List<Map<String, Object>> emails = emailsResponse.getBody();
+            String email = null;
+
+            for (Map<String, Object> emailInfo : emails) {
+                Boolean primary = (Boolean) emailInfo.get("primary");
+                if (primary != null && primary) {
+                    email = (String) emailInfo.get("email");
+                    break;
+                }
+            }
+
+            if (email == null && !emails.isEmpty()) {
+                email = (String) emails.get(0).get("email");
+            }
+
+            String githubId = userAttributes.get("id").toString();
+            String username = (String) userAttributes.get("login");
+
+            Optional<UserEntity> userOptional = userRepository.findByProviderId(githubId);
+            UserEntity user;
+
+            if (userOptional.isPresent()) {
+                user = userOptional.get();
+            } else {
+                userOptional = userRepository.findByEmail(email);
+
+                if (userOptional.isPresent()) {
+                    user = userOptional.get();
+                    user.setProvider(AuthProvider.GITHUB);
+                    user.setProviderId(githubId);
+                } else {
+                    user = new UserEntity();
+                    user.setEmail(email);
+                    user.setUsername(username);
+                    user.setProvider(AuthProvider.GITHUB);
+                    user.setProviderId(githubId);
+                    user.setEmailVerified(true);
+
+                    user.setBalance(new BigDecimal("1000.00"));
+                }
+            }
+
+            String randomPassword = UUID.randomUUID().toString();
+            user.setPassword(oauth2PasswordEncoder.encode(randomPassword));
+
+            userRepository.save(user);
+
+            Authentication authentication = this.authenticationManager.authenticate(new UsernamePasswordAuthenticationToken(user.getEmail(), randomPassword));
+
+            String token = jwtUtils.generateToken(authentication);
+
+            return new AuthResponseDto(token);
+
+        } catch (Exception e) {
+            throw new RuntimeException("Failed to process GitHub authentication", e);
+        }
+    }
+}

backend/src/main/java/de/szut/casino/security/SecurityConfig.java

@@ -38,13 +38,14 @@ public class SecurityConfig {
     @Autowired
     private JwtAuthenticationFilter jwtAuthenticationFilter;
 
+
     @Bean
     public DaoAuthenticationProvider authenticationProvider() {
         DaoAuthenticationProvider authProvider = new DaoAuthenticationProvider();
-        
+
         authProvider.setUserDetailsService(userDetailsService);
         authProvider.setPasswordEncoder(passwordEncoder());
-        
+
         return authProvider;
     }
 
@@ -61,16 +62,16 @@ public class SecurityConfig {
     @Bean
     public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
         http
-            .cors(cors -> cors.configurationSource(corsConfigurationSource()))
+                .cors(cors -> cors.configurationSource(corsConfigurationSource()))
-            .csrf(csrf -> csrf.disable())
+                .csrf(csrf -> csrf.disable())
-            .sessionManagement(session -> session.sessionCreationPolicy(SessionCreationPolicy.STATELESS))
+                .sessionManagement(session -> session.sessionCreationPolicy(SessionCreationPolicy.STATELESS))
-            .authorizeHttpRequests(auth -> {
+                .authorizeHttpRequests(auth -> {
-                auth.requestMatchers("/auth/**", "/webhook", "/swagger/**", "/swagger-ui/**", "/health", "/error").permitAll()
+                    auth.requestMatchers("/auth/**", "/webhook", "/swagger/**", "/swagger-ui/**", "/health", "/error", "/oauth2/**").permitAll()
-                    .requestMatchers(org.springframework.http.HttpMethod.OPTIONS, "/**").permitAll()
+                            .requestMatchers(org.springframework.http.HttpMethod.OPTIONS, "/**").permitAll()
-                    .anyRequest().authenticated();
+                            .anyRequest().authenticated();
                 })
-            .authenticationProvider(authenticationProvider())
+                .authenticationProvider(authenticationProvider())
-            .addFilterBefore(jwtAuthenticationFilter, UsernamePasswordAuthenticationFilter.class);
+                .addFilterBefore(jwtAuthenticationFilter, UsernamePasswordAuthenticationFilter.class);
 
         return http.build();
     }

backend/src/main/java/de/szut/casino/security/dto/AuthResponseDto.java

@@ -12,7 +12,7 @@ import lombok.Setter;
 public class AuthResponseDto {
     private String token;
     private String tokenType = "Bearer";
-    
+
     public AuthResponseDto(String token) {
         this.token = token;
     }

backend/src/main/java/de/szut/casino/security/dto/GithubCallbackDto.java

@@ -0,0 +1,8 @@
+package de.szut.casino.security.dto;
+
+import lombok.Data;
+
+@Data
+public class GithubCallbackDto {
+    private String code;
+}

backend/src/main/java/de/szut/casino/security/dto/LoginRequestDto.java

@@ -13,7 +13,7 @@ import lombok.Setter;
 public class LoginRequestDto {
     @NotBlank(message = "Username or email is required")
     private String usernameOrEmail;
-    
+
     @NotBlank(message = "Password is required")
     private String password;
 }

backend/src/main/java/de/szut/casino/security/jwt/JwtAuthenticationFilter.java

@@ -35,11 +35,11 @@ public class JwtAuthenticationFilter extends OncePerRequestFilter {
 
                 if (username != null && SecurityContextHolder.getContext().getAuthentication() == null) {
                     UserDetails userDetails = userDetailsService.loadUserByUsername(username);
-                    
+
                     if (jwtUtils.validateToken(jwt, userDetails)) {
                         UsernamePasswordAuthenticationToken authToken = new UsernamePasswordAuthenticationToken(
                                 userDetails, null, userDetails.getAuthorities());
-                        
+
                         authToken.setDetails(new WebAuthenticationDetailsSource().buildDetails(request));
                         SecurityContextHolder.getContext().setAuthentication(authToken);
                     }

backend/src/main/java/de/szut/casino/security/jwt/JwtUtils.java

@@ -1,12 +1,16 @@
 package de.szut.casino.security.jwt;
 
+import de.szut.casino.security.oauth2.UserPrincipal;
 import io.jsonwebtoken.Claims;
 import io.jsonwebtoken.Jwts;
 import io.jsonwebtoken.SignatureAlgorithm;
 import io.jsonwebtoken.security.Keys;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.security.core.Authentication;
 import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.security.oauth2.core.user.OAuth2User;
 import org.springframework.stereotype.Component;
 
 import java.security.Key;
@@ -17,6 +21,7 @@ import java.util.function.Function;
 
 @Component
 public class JwtUtils {
+    private static final Logger logger = LoggerFactory.getLogger(JwtUtils.class);
 
     @Value("${jwt.secret}")
     private String jwtSecret;
@@ -29,8 +34,26 @@ public class JwtUtils {
     }
 
     public String generateToken(Authentication authentication) {
-        UserDetails userDetails = (UserDetails) authentication.getPrincipal();
+        String subject = null;
-        return generateToken(userDetails.getUsername());
+        Map<String, Object> claims = new HashMap<>();
+
+        if (authentication.getPrincipal() instanceof UserPrincipal) {
+            UserPrincipal userPrincipal = (UserPrincipal) authentication.getPrincipal();
+            subject = userPrincipal.getEmail();
+            claims.put("id", userPrincipal.getId());
+            claims.put("username", userPrincipal.getDisplayUsername());
+            logger.info("Generating token for UserPrincipal: {}", subject);
+        } else if (authentication.getPrincipal() instanceof OAuth2User) {
+            OAuth2User oauth2User = (OAuth2User) authentication.getPrincipal();
+            subject = (String) oauth2User.getAttributes().get("email");
+            logger.info("Generating token for OAuth2User: {}", subject);
+        } else {
+            UserDetails userDetails = (UserDetails) authentication.getPrincipal();
+            subject = userDetails.getUsername();
+            logger.info("Generating token for UserDetails: {}", subject);
+        }
+
+        return createToken(claims, subject);
     }
 
     public String generateToken(String username) {
@@ -40,6 +63,9 @@ public class JwtUtils {
 
     private String createToken(Map<String, Object> claims, String subject) {
         Date now = new Date();
+        logger.info("now: {}", now);
+        logger.info("jwtExpirationMs: {}", jwtExpirationMs);
+        logger.info("expiryDate: {}", new Date(now.getTime() + jwtExpirationMs));
         Date expiryDate = new Date(now.getTime() + jwtExpirationMs);
 
         return Jwts.builder()

backend/src/main/java/de/szut/casino/security/oauth2/CustomOAuth2UserService.java

@@ -0,0 +1,105 @@
+package de.szut.casino.security.oauth2;
+
+import de.szut.casino.exceptionHandling.exceptions.OAuth2AuthenticationProcessingException;
+import de.szut.casino.user.AuthProvider;
+import de.szut.casino.user.UserEntity;
+import de.szut.casino.user.UserRepository;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.security.authentication.InternalAuthenticationServiceException;
+import org.springframework.security.core.AuthenticationException;
+import org.springframework.security.crypto.password.PasswordEncoder;
+import org.springframework.security.oauth2.client.userinfo.DefaultOAuth2UserService;
+import org.springframework.security.oauth2.client.userinfo.OAuth2UserRequest;
+import org.springframework.security.oauth2.core.OAuth2AuthenticationException;
+import org.springframework.security.oauth2.core.user.OAuth2User;
+import org.springframework.stereotype.Service;
+import org.springframework.util.StringUtils;
+
+import java.math.BigDecimal;
+import java.util.Optional;
+import java.util.UUID;
+
+@Service
+public class CustomOAuth2UserService extends DefaultOAuth2UserService {
+
+    @Autowired
+    private UserRepository userRepository;
+
+    @Autowired
+    private PasswordEncoder oauth2PasswordEncoder;
+
+    @Override
+    public OAuth2User loadUser(OAuth2UserRequest oAuth2UserRequest) throws OAuth2AuthenticationException {
+        OAuth2User oAuth2User = super.loadUser(oAuth2UserRequest);
+
+        try {
+            return processOAuth2User(oAuth2UserRequest, oAuth2User);
+        } catch (AuthenticationException ex) {
+            throw ex;
+        } catch (Exception ex) {
+            throw new InternalAuthenticationServiceException(ex.getMessage(), ex.getCause());
+        }
+    }
+
+    private OAuth2User processOAuth2User(OAuth2UserRequest oAuth2UserRequest, OAuth2User oAuth2User) {
+        String registrationId = oAuth2UserRequest.getClientRegistration().getRegistrationId();
+        OAuth2UserInfo oAuth2UserInfo = OAuth2UserInfoFactory.getOAuth2UserInfo(registrationId, oAuth2User.getAttributes());
+
+        String email = oAuth2UserInfo.getEmail();
+        if (StringUtils.isEmpty(email)) {
+            email = oAuth2UserInfo.getName() + "@github.user";
+        }
+
+        Optional<UserEntity> userOptional = userRepository.findByEmail(email);
+        UserEntity user;
+
+        if (userOptional.isPresent()) {
+            user = userOptional.get();
+
+            if (!user.getProvider().equals(AuthProvider.valueOf(registrationId.toUpperCase()))) {
+                throw new OAuth2AuthenticationProcessingException("You're signed up with " +
+                        user.getProvider() + ". Please use your " + user.getProvider() +
+                        " account to login.");
+            }
+
+            user = updateExistingUser(user, oAuth2UserInfo);
+        } else {
+            user = registerNewUser(oAuth2UserRequest, oAuth2UserInfo, email);
+        }
+
+        return UserPrincipal.create(user, oAuth2User.getAttributes());
+    }
+
+    private UserEntity registerNewUser(OAuth2UserRequest oAuth2UserRequest, OAuth2UserInfo oAuth2UserInfo, String email) {
+        UserEntity user = new UserEntity();
+
+        String username = oAuth2UserInfo.getName();
+        if (StringUtils.isEmpty(username)) {
+            username = "github_" + oAuth2UserInfo.getId();
+        }
+
+        if (userRepository.findByUsername(username).isPresent()) {
+            username = username + "_" + UUID.randomUUID().toString().substring(0, 8);
+        }
+
+        user.setProvider(AuthProvider.valueOf(oAuth2UserRequest.getClientRegistration().getRegistrationId().toUpperCase()));
+        user.setProviderId(oAuth2UserInfo.getId());
+        user.setUsername(username);
+        user.setEmail(email);
+        user.setEmailVerified(true);
+
+        String randomPassword = UUID.randomUUID().toString();
+        user.setPassword(oauth2PasswordEncoder.encode(randomPassword));
+
+        user.setBalance(new BigDecimal("100.00")); // Starting balance
+
+        return userRepository.save(user);
+    }
+
+    private UserEntity updateExistingUser(UserEntity existingUser, OAuth2UserInfo oAuth2UserInfo) {
+        if (!StringUtils.isEmpty(oAuth2UserInfo.getName())) {
+            existingUser.setUsername(oAuth2UserInfo.getName());
+        }
+        return userRepository.save(existingUser);
+    }
+}

backend/src/main/java/de/szut/casino/security/oauth2/GitHubOAuth2UserInfo.java

@@ -0,0 +1,25 @@
+package de.szut.casino.security.oauth2;
+
+import java.util.Map;
+
+public class GitHubOAuth2UserInfo extends OAuth2UserInfo {
+
+    public GitHubOAuth2UserInfo(Map<String, Object> attributes) {
+        super(attributes);
+    }
+
+    @Override
+    public String getId() {
+        return ((Integer) attributes.get("id")).toString();
+    }
+
+    @Override
+    public String getName() {
+        return (String) attributes.get("name");
+    }
+
+    @Override
+    public String getEmail() {
+        return (String) attributes.get("email");
+    }
+}

backend/src/main/java/de/szut/casino/security/oauth2/OAuth2AuthenticationSuccessHandler.java

@@ -0,0 +1,55 @@
+package de.szut.casino.security.oauth2;
+
+import de.szut.casino.security.jwt.JwtUtils;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.security.core.Authentication;
+import org.springframework.security.web.authentication.SimpleUrlAuthenticationSuccessHandler;
+import org.springframework.stereotype.Component;
+import org.springframework.web.util.UriComponentsBuilder;
+
+import java.io.IOException;
+
+@Component
+public class OAuth2AuthenticationSuccessHandler extends SimpleUrlAuthenticationSuccessHandler {
+    private static final Logger logger = LoggerFactory.getLogger(OAuth2AuthenticationSuccessHandler.class);
+
+    @Value("${app.oauth2.authorizedRedirectUris}")
+    private String redirectUri;
+
+    @Autowired
+    private JwtUtils jwtUtils;
+
+    @Override
+    public void onAuthenticationSuccess(HttpServletRequest request, HttpServletResponse response, Authentication authentication)
+            throws IOException {
+        String targetUrl = determineTargetUrl(authentication);
+
+        logger.info("OAuth2 Authentication successful, redirecting to: {}", targetUrl);
+
+        if (response.isCommitted()) {
+            logger.debug("Response has already been committed. Unable to redirect to " + targetUrl);
+            return;
+        }
+
+        clearAuthenticationAttributes(request);
+        getRedirectStrategy().sendRedirect(request, response, targetUrl);
+    }
+
+    private String determineTargetUrl(Authentication authentication) {
+        String token = jwtUtils.generateToken(authentication);
+
+        if (authentication.getPrincipal() instanceof UserPrincipal) {
+            UserPrincipal userPrincipal = (UserPrincipal) authentication.getPrincipal();
+            logger.info("User authenticated: ID={}, Email={}", userPrincipal.getId(), userPrincipal.getEmail());
+        }
+
+        return UriComponentsBuilder.fromUriString(redirectUri)
+                .queryParam("token", token)
+                .build().toUriString();
+    }
+}

backend/src/main/java/de/szut/casino/security/oauth2/OAuth2Config.java

@@ -0,0 +1,15 @@
+package de.szut.casino.security.oauth2;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
+
+@Configuration
+public class OAuth2Config {
+
+    @Bean
+    public PasswordEncoder oauth2PasswordEncoder() {
+        return new BCryptPasswordEncoder();
+    }
+}

backend/src/main/java/de/szut/casino/security/oauth2/OAuth2UserInfo.java

@@ -0,0 +1,20 @@
+package de.szut.casino.security.oauth2;
+
+import lombok.Getter;
+
+import java.util.Map;
+
+@Getter
+public abstract class OAuth2UserInfo {
+    protected Map<String, Object> attributes;
+
+    public OAuth2UserInfo(Map<String, Object> attributes) {
+        this.attributes = attributes;
+    }
+
+    public abstract String getId();
+
+    public abstract String getName();
+
+    public abstract String getEmail();
+}

backend/src/main/java/de/szut/casino/security/oauth2/OAuth2UserInfoFactory.java

@@ -0,0 +1,17 @@
+package de.szut.casino.security.oauth2;
+
+import de.szut.casino.exceptionHandling.exceptions.OAuth2AuthenticationProcessingException;
+import de.szut.casino.user.AuthProvider;
+
+import java.util.Map;
+
+public class OAuth2UserInfoFactory {
+
+    public static OAuth2UserInfo getOAuth2UserInfo(String registrationId, Map<String, Object> attributes) {
+        if (registrationId.equalsIgnoreCase(AuthProvider.GITHUB.toString())) {
+            return new GitHubOAuth2UserInfo(attributes);
+        } else {
+            throw new OAuth2AuthenticationProcessingException("Sorry! Login with " + registrationId + " is not supported yet.");
+        }
+    }
+}

backend/src/main/java/de/szut/casino/security/oauth2/UserPrincipal.java

@@ -0,0 +1,102 @@
+package de.szut.casino.security.oauth2;
+
+import de.szut.casino.user.UserEntity;
+import lombok.Getter;
+import lombok.Setter;
+import org.springframework.security.core.GrantedAuthority;
+import org.springframework.security.core.authority.SimpleGrantedAuthority;
+import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.security.oauth2.core.user.OAuth2User;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+
+public class UserPrincipal implements OAuth2User, UserDetails {
+    @Getter
+    private Long id;
+    @Getter
+    private String email;
+    private String username;
+    private String password;
+    private Collection<? extends GrantedAuthority> authorities;
+    @Setter
+    private Map<String, Object> attributes;
+
+    public UserPrincipal(Long id, String email, String username, String password, Collection<? extends GrantedAuthority> authorities) {
+        this.id = id;
+        this.email = email;
+        this.username = username;
+        this.password = password;
+        this.authorities = authorities;
+    }
+
+    public static UserPrincipal create(UserEntity user) {
+        List<GrantedAuthority> authorities = Collections.
+                singletonList(new SimpleGrantedAuthority("ROLE_USER"));
+
+        return new UserPrincipal(
+                user.getId(),
+                user.getEmail(),
+                user.getUsername(),
+                user.getPassword(),
+                authorities
+        );
+    }
+
+    public static UserPrincipal create(UserEntity user, Map<String, Object> attributes) {
+        UserPrincipal userPrincipal = UserPrincipal.create(user);
+        userPrincipal.setAttributes(attributes);
+        return userPrincipal;
+    }
+
+    @Override
+    public String getPassword() {
+        return password;
+    }
+
+    @Override
+    public String getUsername() {
+        return email;
+    }
+
+    public String getDisplayUsername() {
+        return username;
+    }
+
+    @Override
+    public boolean isAccountNonExpired() {
+        return true;
+    }
+
+    @Override
+    public boolean isAccountNonLocked() {
+        return true;
+    }
+
+    @Override
+    public boolean isCredentialsNonExpired() {
+        return true;
+    }
+
+    @Override
+    public boolean isEnabled() {
+        return true;
+    }
+
+    @Override
+    public Collection<? extends GrantedAuthority> getAuthorities() {
+        return authorities;
+    }
+
+    @Override
+    public Map<String, Object> getAttributes() {
+        return attributes;
+    }
+
+    @Override
+    public String getName() {
+        return String.valueOf(id);
+    }
+}

backend/src/main/java/de/szut/casino/security/service/AuthService.java

@@ -19,7 +19,6 @@ import org.springframework.security.core.context.SecurityContextHolder;
 import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.stereotype.Service;
 
-import javax.swing.text.html.Option;
 import java.io.IOException;
 import java.util.Optional;
 

backend/src/main/java/de/szut/casino/security/service/UserDetailsServiceImpl.java

@@ -20,17 +20,17 @@ public class UserDetailsServiceImpl implements UserDetailsService {
     @Override
     public UserDetails loadUserByUsername(String usernameOrEmail) throws UsernameNotFoundException {
         Optional<UserEntity> user = userRepository.findByUsername(usernameOrEmail);
-        
+
         if (user.isEmpty()) {
             user = userRepository.findByEmail(usernameOrEmail);
         }
-        
+
-        UserEntity userEntity = user.orElseThrow(() -> 
+        UserEntity userEntity = user.orElseThrow(() ->
                 new UsernameNotFoundException("User not found with username or email: " + usernameOrEmail));
-        
+
         return new org.springframework.security.core.userdetails.User(
-                userEntity.getUsername(), 
+                userEntity.getUsername(),
-                userEntity.getPassword(), 
+                userEntity.getPassword(),
                 new ArrayList<>());
     }
 }

backend/src/main/java/de/szut/casino/user/AuthProvider.java

@@ -0,0 +1,6 @@
+package de.szut.casino.user;
+
+public enum AuthProvider {
+    LOCAL,
+    GITHUB
+}

backend/src/main/java/de/szut/casino/user/UserEntity.java

@@ -1,9 +1,6 @@
 package de.szut.casino.user;
 
-import jakarta.persistence.Column;
+import jakarta.persistence.*;
-import jakarta.persistence.Entity;
-import jakarta.persistence.GeneratedValue;
-import jakarta.persistence.Id;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 import lombok.Setter;
@@ -18,15 +15,15 @@ public class UserEntity {
     @Id
     @GeneratedValue
     private Long id;
-    
+
     @Column(unique = true)
     private String email;
-    
+
     @Column(unique = true)
     private String username;
-    
+
     private String password;
-    
+
     @Column(precision = 19, scale = 2)
     private BigDecimal balance;
 
@@ -36,12 +33,27 @@ public class UserEntity {
 
     private String passwordResetToken;
 
+    @Enumerated(EnumType.STRING)
+    private AuthProvider provider = AuthProvider.LOCAL;
+
+    private String providerId;
+
     public UserEntity(String email, String username, String password, BigDecimal balance, String verificationToken) {
         this.email = email;
         this.username = username;
         this.password = password;
         this.balance = balance;
         this.verificationToken = verificationToken;
+        this.provider = AuthProvider.LOCAL;
+    }
+
+    public UserEntity(String email, String username, AuthProvider provider, String providerId, BigDecimal balance) {
+        this.email = email;
+        this.username = username;
+        this.provider = provider;
+        this.providerId = providerId;
+        this.balance = balance;
+        this.emailVerified = true; // OAuth providers verify emails
     }
 
     public void addBalance(BigDecimal amountToAdd) {

backend/src/main/java/de/szut/casino/user/UserMappingService.java

@@ -5,7 +5,7 @@ import org.springframework.stereotype.Service;
 
 @Service
 public class UserMappingService {
-    
+
     public GetUserDto mapToGetUserDto(UserEntity user) {
         return new GetUserDto(user.getId(), user.getEmail(), user.getUsername(), user.getBalance());
     }

backend/src/main/java/de/szut/casino/user/UserRepository.java

@@ -9,11 +9,13 @@ import java.util.Optional;
 @Service
 public interface UserRepository extends JpaRepository<UserEntity, Long> {
     Optional<UserEntity> findByUsername(String username);
-    
+
     Optional<UserEntity> findByEmail(String email);
-    
+
+    Optional<UserEntity> findByProviderId(String providerId);
+
     boolean existsByUsername(String username);
-    
+
     boolean existsByEmail(String email);
 
     @Query("SELECT u FROM UserEntity u WHERE u.verificationToken = ?1")

backend/src/main/java/de/szut/casino/user/UserService.java

@@ -27,15 +27,15 @@ public class UserService {
         if (userRepository.existsByEmail(createUserDto.getEmail())) {
             throw new EntityExistsException("Email is already in use");
         }
-        
+
         UserEntity user = new UserEntity(
-            createUserDto.getEmail(),
+                createUserDto.getEmail(),
-            createUserDto.getUsername(),
+                createUserDto.getUsername(),
-            passwordEncoder.encode(createUserDto.getPassword()),
+                passwordEncoder.encode(createUserDto.getPassword()),
-            BigDecimal.valueOf(100),
+                BigDecimal.valueOf(100),
-            RandomStringUtils.randomAlphanumeric(64)
+                RandomStringUtils.randomAlphanumeric(64)
         );
-        
+
         return userRepository.save(user);
     }
 
@@ -50,7 +50,7 @@ public class UserService {
     }
 
     public void saveUser(UserEntity user) {
-            userRepository.save(user);
+        userRepository.save(user);
     }
 
     public boolean isVerified(String usernameOrEmail) {

backend/src/main/java/de/szut/casino/user/dto/CreateUserDto.java

@@ -16,11 +16,11 @@ public class CreateUserDto {
     @NotBlank(message = "Email is required")
     @Email(message = "Email should be valid")
     private String email;
-    
+
     @NotBlank(message = "Username is required")
     @Size(min = 3, max = 20, message = "Username must be between 3 and 20 characters")
     private String username;
-    
+
     @NotBlank(message = "Password is required")
     @Size(min = 6, message = "Password must be at least 6 characters")
     private String password;

backend/src/main/java/de/szut/casino/user/transaction/TransactionController.java

@@ -19,7 +19,7 @@ public class TransactionController {
             @RequestHeader("Authorization") String authToken,
             @RequestParam(value = "limit", required = false) Integer limit,
             @RequestParam(value = "offset", required = false) Integer offset
-            ) {
+    ) {
         UserTransactionsDto transactionEntities = this.transactionService.getUserTransactionsDto(authToken, limit, offset);
 
         return ResponseEntity.ok(transactionEntities);

backend/src/main/resources/application.properties

@@ -28,3 +28,16 @@ logging.level.org.springframework.security=DEBUG
 springdoc.swagger-ui.path=swagger
 springdoc.swagger-ui.try-it-out-enabled=true
 
+# GitHub OAuth2 Configuration
+spring.security.oauth2.client.registration.github.client-id=${GITHUB_CLIENT_ID:Ov23lingzZsPn1wwACoK}
+spring.security.oauth2.client.registration.github.client-secret=${GITHUB_CLIENT_SECRET:4b327fb3b1ab67584a03bcb9d53fa6439fbccad7}
+spring.security.oauth2.client.registration.github.redirect-uri=${app.frontend-host}/oauth2/callback/github
+spring.security.oauth2.client.registration.github.scope=user:email,read:user
+spring.security.oauth2.client.provider.github.authorization-uri=https://github.com/login/oauth/authorize
+spring.security.oauth2.client.provider.github.token-uri=https://github.com/login/oauth/access_token
+spring.security.oauth2.client.provider.github.user-info-uri=https://api.github.com/user
+spring.security.oauth2.client.provider.github.user-name-attribute=login
+
+# OAuth Success and Failure URLs
+app.oauth2.authorizedRedirectUris=${app.frontend-host}/auth/oauth2/callback
+

backend/src/main/resources/templates/email/verify.html

@@ -123,7 +123,7 @@
         <p>Klicken Sie auf den folgenden Button, um Ihre E-Mail-Adresse zu bestätigen:</p>
 
         <div style="text-align: center;">
-            <a href="${feUrl}/verify?token=${token}" class="button">E-Mail bestätigen</a>
+            <a href="${feUrl}/verify?email-token=${token}" class="button">E-Mail bestätigen</a>
         </div>
 
         <div class="info-box">

frontend/src/app/app.routes.ts

@@ -33,6 +33,13 @@ export const routes: Routes = [
         (m) => m.RecoverPasswordComponent
       ),
   },
+  {
+    path: 'oauth2/callback/github',
+    loadComponent: () =>
+      import('./feature/auth/oauth2/oauth2-callback.component').then(
+        (m) => m.OAuth2CallbackComponent
+      ),
+  },
   {
     path: 'game/blackjack',
     loadComponent: () => import('./feature/game/blackjack/blackjack.component'),

frontend/src/app/feature/auth/login/login.component.html

@@ -83,7 +83,32 @@
       </div>
     </form>
 
-    <div class="mt-6 text-center">
+    <div class="my-4 flex items-center">
+      <div class="flex-grow h-px bg-deep-blue-light/30"></div>
+      <span class="px-3 text-xs text-text-secondary">ODER</span>
+      <div class="flex-grow h-px bg-deep-blue-light/30"></div>
+    </div>
+
+    <div class="mb-4">
+      <button
+        (click)="loginWithGithub()"
+        class="w-full py-2.5 px-4 rounded flex items-center justify-center bg-gray-800 hover:bg-gray-700 text-white transition-colors"
+      >
+        <svg
+          class="h-5 w-5 mr-2"
+          xmlns="http://www.w3.org/2000/svg"
+          viewBox="0 0 24 24"
+          fill="currentColor"
+        >
+          <path
+            d="M12 0C5.37 0 0 5.37 0 12c0 5.31 3.435 9.795 8.205 11.385.6.105.825-.255.825-.57 0-.285-.015-1.23-.015-2.235-3.015.555-3.795-.735-4.035-1.41-.135-.345-.72-1.41-1.23-1.695-.42-.225-1.02-.78-.015-.795.945-.015 1.62.87 1.845 1.23 1.08 1.815 2.805 1.305 3.495.99.105-.78.42-1.305.765-1.605-2.67-.3-5.46-1.335-5.46-5.925 0-1.305.465-2.385 1.23-3.225-.12-.3-.54-1.53.12-3.18 0 0 1.005-.315 3.3 1.23.96-.27 1.98-.405 3-.405s2.04.135 3 .405c2.295-1.56 3.3-1.23 3.3-1.23.66 1.65.24 2.88.12 3.18.765.84 1.23 1.905 1.23 3.225 0 4.605-2.805 5.625-5.475 5.925.435.375.81 1.095.81 2.22 0 1.605-.015 2.895-.015 3.3 0 .315.225.69.825.57A12.02 12.02 0 0 0 24 12c0-6.63-5.37-12-12-12z"
+          />
+        </svg>
+        Mit GitHub anmelden
+      </button>
+    </div>
+
+    <div class="text-center">
       <p class="text-sm text-text-secondary">
         Passwort vergessen?
         <button

frontend/src/app/feature/auth/login/login.component.ts

@@ -4,6 +4,7 @@ import { Router } from '@angular/router';
 import { LoginRequest } from '../../../model/auth/LoginRequest';
 import { AuthService } from '@service/auth.service';
 import { CommonModule } from '@angular/common';
+import { environment } from '@environments/environment';
 
 @Component({
   selector: 'app-login',
@@ -65,6 +66,11 @@ export class LoginComponent {
     });
   }
 
+  loginWithGithub(): void {
+    this.isLoading.set(true);
+    window.location.href = `${environment.apiUrl}/oauth2/github/authorize`;
+  }
+
   switchToForgotPassword() {
     this.forgotPassword.emit();
   }

frontend/src/app/feature/auth/oauth2/oauth2-callback.component.ts

@@ -0,0 +1,64 @@
+import { Component, OnInit } from '@angular/core';
+import { CommonModule } from '@angular/common';
+import { ActivatedRoute, Router } from '@angular/router';
+import { AuthService } from '@service/auth.service';
+
+@Component({
+  selector: 'app-oauth2-callback',
+  standalone: true,
+  imports: [CommonModule],
+  template: `
+    <div class="min-h-screen bg-deep-blue flex items-center justify-center">
+      <div class="text-center">
+        <h2 class="text-2xl font-bold text-white mb-4">Finishing authentication...</h2>
+        <div
+          class="animate-spin rounded-full h-12 w-12 border-t-2 border-b-2 border-emerald mx-auto"
+        ></div>
+        <p *ngIf="error" class="mt-4 text-accent-red">{{ error }}</p>
+      </div>
+    </div>
+  `,
+})
+export class OAuth2CallbackComponent implements OnInit {
+  error: string | null = null;
+
+  constructor(
+    private route: ActivatedRoute,
+    private router: Router,
+    private authService: AuthService
+  ) {}
+
+  ngOnInit(): void {
+    // Check for code in URL params
+    this.route.queryParams.subscribe((params) => {
+      const code = params['code'];
+
+      if (code) {
+        // Exchange GitHub code for a JWT token
+        this.authService.githubAuth(code).subscribe({
+          next: () => {
+            // Redirect to home after successful authentication
+            this.router.navigate(['/home']);
+          },
+          error: (err) => {
+            console.error('GitHub authentication error:', err);
+            this.error = err.error?.message || 'Authentication failed. Please try again.';
+            console.log('Error details:', err);
+
+            // Redirect back to landing page after showing error
+            setTimeout(() => {
+              this.router.navigate(['/']);
+            }, 3000);
+          },
+        });
+      } else {
+        this.error = 'Authentication failed. No authorization code received.';
+
+        // Redirect back to landing page after showing error
+        setTimeout(() => {
+          this.router.navigate(['/']);
+        }, 3000);
+      }
+    });
+  }
+}

frontend/src/app/feature/auth/verify-email/verify-email.component.ts

@@ -13,7 +13,7 @@ export class VerifyEmailComponent implements OnInit {
   authService: AuthService = inject(AuthService);
 
   ngOnInit(): void {
-    const token = this.route.snapshot.queryParamMap.get('token');
+    const token = this.route.snapshot.queryParamMap.get('email-token');
 
     if (!token) {
       this.router.navigate(['/']);

frontend/src/app/service/auth.service.ts

@@ -1,7 +1,7 @@
 import { Injectable } from '@angular/core';
 import { HttpClient } from '@angular/common/http';
 import { BehaviorSubject, Observable, tap } from 'rxjs';
-import { Router } from '@angular/router';
+import { Router, ActivatedRoute } from '@angular/router';
 import { LoginRequest } from '../model/auth/LoginRequest';
 import { RegisterRequest } from '../model/auth/RegisterRequest';
 import { AuthResponse } from '../model/auth/AuthResponse';
@@ -17,20 +17,41 @@ const USER_KEY = 'user';
 export class AuthService {
   private authUrl = `${environment.apiUrl}/auth`;
   private userUrl = `${environment.apiUrl}/users`;
+  private oauthUrl = `${environment.apiUrl}/oauth2`;
 
   userSubject: BehaviorSubject<User | null>;
 
   constructor(
     private http: HttpClient,
-    private router: Router
+    private router: Router,
+    private route: ActivatedRoute
   ) {
     this.userSubject = new BehaviorSubject<User | null>(this.getUserFromStorage());
 
+    // Check for token in URL (OAuth callback) on initialization
+    this.route.queryParams.subscribe((params) => {
+      const token = params['token'];
+      if (token) {
+        this.handleOAuthCallback(token);
+      }
+    });
+
     if (this.getToken()) {
       this.loadCurrentUser();
     }
   }
 
+  private handleOAuthCallback(token: string): void {
+    this.setToken(token);
+    this.loadCurrentUser();
+    // Clean up the URL by removing the token
+    this.router.navigate([], {
+      relativeTo: this.route,
+      queryParams: {},
+      replaceUrl: true,
+    });
+  }
+
   public get currentUserValue(): User | null {
     return this.userSubject.value;
   }
@@ -48,6 +69,16 @@ export class AuthService {
     return this.http.post<User>(`${this.authUrl}/register`, registerRequest);
   }
 
+  githubAuth(code: string): Observable<AuthResponse> {
+    return this.http.post<AuthResponse>(`${this.oauthUrl}/github/callback`, { code }).pipe(
+      tap((response) => {
+        console.log(response.token);
+        this.setToken(response.token);
+        this.loadCurrentUser();
+      })
+    );
+  }
+
   logout(): void {
     localStorage.removeItem(TOKEN_KEY);
     localStorage.removeItem(USER_KEY);