[case11]spring security reactive獲取security context

序

本文主要研究下reactive模式下的spring security context的獲取。

ReactiveSecurityContextHolder

springboot2支持了webflux的異步模式，那麼傳統的基於threadlocal的SecurityContextHolder就無論用了。spring security5.x也支持了reactive方式，這裏就須要使用reactive版本的SecurityContextHolder

spring-security-core-5.0.3.RELEASE-sources.jar!/org/springframework/security/core/context/ReactiveSecurityContextHolder.java

public class ReactiveSecurityContextHolder {
    private static final Class<?> SECURITY_CONTEXT_KEY = SecurityContext.class;

    /**
     * Gets the {@code Mono<SecurityContext>} from Reactor {@link Context}
     * @return the {@code Mono<SecurityContext>}
     */
    public static Mono<SecurityContext> getContext() {
        return Mono.subscriberContext()
            .filter( c -> c.hasKey(SECURITY_CONTEXT_KEY))
            .flatMap( c-> c.<Mono<SecurityContext>>get(SECURITY_CONTEXT_KEY));
    }

    /**
     * Clears the {@code Mono<SecurityContext>} from Reactor {@link Context}
     * @return Return a {@code Mono<Void>} which only replays complete and error signals
     * from clearing the context.
     */
    public static Function<Context, Context> clearContext() {
        return context -> context.delete(SECURITY_CONTEXT_KEY);
    }

    /**
     * Creates a Reactor {@link Context} that contains the {@code Mono<SecurityContext>}
     * that can be merged into another {@link Context}
     * @param securityContext the {@code Mono<SecurityContext>} to set in the returned
     * Reactor {@link Context}
     * @return a Reactor {@link Context} that contains the {@code Mono<SecurityContext>}
     */
    public static Context withSecurityContext(Mono<? extends SecurityContext> securityContext) {
        return Context.of(SECURITY_CONTEXT_KEY, securityContext);
    }

    /**
     * A shortcut for {@link #withSecurityContext(Mono)}
     * @param authentication the {@link Authentication} to be used
     * @return a Reactor {@link Context} that contains the {@code Mono<SecurityContext>}
     */
    public static Context withAuthentication(Authentication authentication) {
        return withSecurityContext(Mono.just(new SecurityContextImpl(authentication)));
    }
}

能夠看到，這裏利用了reactor提供的context機制來進行異步線程的變量傳遞。

實例

public Mono<User> getCurrentUser() {
        return ReactiveSecurityContextHolder.getContext()
                .switchIfEmpty(Mono.error(new IllegalStateException("ReactiveSecurityContext is empty")))
                .map(SecurityContext::getAuthentication)
                .map(Authentication::getPrincipal)
                .cast(User.class);
    }

源碼解析

ServerHttpSecurity

spring-security-config-5.0.3.RELEASE-sources.jar!/org/springframework/security/config/web/server/ServerHttpSecurity.java

public SecurityWebFilterChain build() {
        if(this.built != null) {
            throw new IllegalStateException("This has already been built with the following stacktrace. " + buildToString());
        }
        this.built = new RuntimeException("First Build Invocation").fillInStackTrace();
        if(this.headers != null) {
            this.headers.configure(this);
        }
        WebFilter securityContextRepositoryWebFilter = securityContextRepositoryWebFilter();
        if(securityContextRepositoryWebFilter != null) {
            this.webFilters.add(securityContextRepositoryWebFilter);
        }
        if(this.csrf != null) {
            this.csrf.configure(this);
        }
        if(this.httpBasic != null) {
            this.httpBasic.authenticationManager(this.authenticationManager);
            this.httpBasic.configure(this);
        }
        if(this.formLogin != null) {
            this.formLogin.authenticationManager(this.authenticationManager);
            if(this.securityContextRepository != null) {
                this.formLogin.securityContextRepository(this.securityContextRepository);
            }
            if(this.formLogin.authenticationEntryPoint == null) {
                this.webFilters.add(new OrderedWebFilter(new LoginPageGeneratingWebFilter(), SecurityWebFiltersOrder.LOGIN_PAGE_GENERATING.getOrder()));
                this.webFilters.add(new OrderedWebFilter(new LogoutPageGeneratingWebFilter(), SecurityWebFiltersOrder.LOGOUT_PAGE_GENERATING.getOrder()));
            }
            this.formLogin.configure(this);
        }
        if(this.logout != null) {
            this.logout.configure(this);
        }
        this.requestCache.configure(this);
        this.addFilterAt(new SecurityContextServerWebExchangeWebFilter(), SecurityWebFiltersOrder.SECURITY_CONTEXT_SERVER_WEB_EXCHANGE);
        if(this.authorizeExchange != null) {
            ServerAuthenticationEntryPoint authenticationEntryPoint = getAuthenticationEntryPoint();
            ExceptionTranslationWebFilter exceptionTranslationWebFilter = new ExceptionTranslationWebFilter();
            if(authenticationEntryPoint != null) {
                exceptionTranslationWebFilter.setAuthenticationEntryPoint(
                    authenticationEntryPoint);
            }
            this.addFilterAt(exceptionTranslationWebFilter, SecurityWebFiltersOrder.EXCEPTION_TRANSLATION);
            this.authorizeExchange.configure(this);
        }
        AnnotationAwareOrderComparator.sort(this.webFilters);
        List<WebFilter> sortedWebFilters = new ArrayList<>();
        this.webFilters.forEach( f -> {
            if(f instanceof OrderedWebFilter) {
                f = ((OrderedWebFilter) f).webFilter;
            }
            sortedWebFilters.add(f);
        });
        return new MatcherSecurityWebFilterChain(getSecurityMatcher(), sortedWebFilters);
    }

這裏的build方法建立了securityContextRepositoryWebFilter並添加到webFilters裏頭

securityContextRepositoryWebFilter

private WebFilter securityContextRepositoryWebFilter() {
        ServerSecurityContextRepository repository = this.securityContextRepository;
        if(repository == null) {
            return null;
        }
        WebFilter result = new ReactorContextWebFilter(repository);
        return new OrderedWebFilter(result, SecurityWebFiltersOrder.REACTOR_CONTEXT.getOrder());
    }

這裏建立了ReactorContextWebFilter

ReactorContextWebFilter

spring-security-web-5.0.3.RELEASE-sources.jar!/org/springframework/security/web/server/context/ReactorContextWebFilter.java

public class ReactorContextWebFilter implements WebFilter {
    private final ServerSecurityContextRepository repository;

    public ReactorContextWebFilter(ServerSecurityContextRepository repository) {
        Assert.notNull(repository, "repository cannot be null");
        this.repository = repository;
    }

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
        return chain.filter(exchange)
            .subscriberContext(c -> c.hasKey(SecurityContext.class) ? c :
                withSecurityContext(c, exchange)
            );
    }

    private Context withSecurityContext(Context mainContext, ServerWebExchange exchange) {
        return mainContext.putAll(this.repository.load(exchange)
            .as(ReactiveSecurityContextHolder::withSecurityContext));
    }
}

這裏使用reactor的subscriberContext將SecurityContext注入進去。

小結

基於reactor提供的context機制，spring security也相應提供了ReactiveSecurityContextHolder用來獲取當前用戶，很是便利。

doc

• 聊聊reactor異步線程的變量傳遞
• 5.10.3 EnableReactiveMethodSecurity