[[webflux-headers]]
= Security HTTP Response Headers

xref:features/exploits/headers.adoc#headers[Security HTTP Response Headers] can be used to increase the security of web applications.
This section is dedicated to WebFlux based support for Security HTTP Response Headers.

[[webflux-headers-default]]
== Default Security Headers

Spring Security provides a xref:features/exploits/headers.adoc#headers-default[default set of Security HTTP Response Headers] to provide secure defaults.
While each of these headers are considered best practice, it should be noted that not all clients utilize the headers, so additional testing is encouraged.

You can customize specific headers.
For example, assume that you want the defaults except you wish to specify `SAMEORIGIN` for xref:servlet/exploits/headers.adoc#servlet-headers-frame-options[X-Frame-Options].

You can easily do this with the following Configuration:

.Customize Default Security Headers
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		// ...
		.headers(headers -> headers
			.frameOptions(frameOptions -> frameOptions
				.mode(Mode.SAMEORIGIN)
			)
		);
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    return http {
        // ...
        headers {
            frameOptions {
                mode = Mode.SAMEORIGIN
            }
        }
    }
}
----
====

If you do not want the defaults to be added and want explicit control over what should be used, you can disable the defaults.
An example is provided below:

.Disable HTTP Security Response Headers
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		// ...
		.headers(headers -> headers.disable());
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    return http {
        // ...
        headers {
            disable()
        }
    }
}
----
====

[[webflux-headers-cache-control]]
== Cache Control

Spring Security includes xref:features/exploits/headers.adoc#headers-cache-control[Cache Control] headers by default.

However, if you actually want to cache specific responses, your application can selectively add them to the https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/http/server/reactive/ServerHttpResponse.html[ServerHttpResponse] to override the header set by Spring Security.
This is useful to ensure things like CSS, JavaScript, and images are properly cached.

When using Spring WebFlux, this is typically done within your configuration.
Details on how to do this can be found in the https://docs.spring.io/spring/docs/5.0.0.RELEASE/spring-framework-reference/web-reactive.html#webflux-config-static-resources[Static Resources] portion of the Spring Reference documentation

If necessary, you can also disable Spring Security's cache control HTTP response headers.

.Cache Control Disabled
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		// ...
		.headers(headers -> headers
			.cache(cache -> cache.disable())
		);
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    return http {
        // ...
        headers {
            cache {
                disable()
            }
        }
    }
}
----
====


[[webflux-headers-content-type-options]]
== Content Type Options
Spring Security includes xref:features/exploits/headers.adoc#headers-content-type-options[Content-Type] headers by default.
However, you can disable it with:

.Content Type Options Disabled
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		// ...
		.headers(headers -> headers
			.contentTypeOptions(contentTypeOptions -> contentTypeOptions.disable())
		);
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    return http {
        // ...
        headers {
            contentTypeOptions {
                disable()
            }
        }
    }
}
----
====

[[webflux-headers-hsts]]
== HTTP Strict Transport Security (HSTS)
Spring Security provides the xref:features/exploits/headers.adoc#headers-hsts[Strict Transport Security] header by default.
However, you can customize the results explicitly.
For example, the following is an example of explicitly providing HSTS:

.Strict Transport Security
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		// ...
		.headers(headers -> headers
			.hsts(hsts -> hsts
				.includeSubdomains(true)
				.preload(true)
				.maxAge(Duration.ofDays(365))
			)
		);
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    return http {
        // ...
        headers {
            hsts {
                includeSubdomains = true
                preload = true
                maxAge = Duration.ofDays(365)
            }
        }
    }
}
----
====

[[webflux-headers-frame-options]]
== X-Frame-Options
By default, Spring Security disables rendering within an iframe using xref:features/exploits/headers.adoc#headers-frame-options[X-Frame-Options].

You can customize frame options to use the same origin using the following:

.X-Frame-Options: SAMEORIGIN
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		// ...
		.headers(headers -> headers
			.frameOptions(frameOptions -> frameOptions
				.mode(SAMEORIGIN)
			)
		);
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    return http {
        // ...
        headers {
            frameOptions {
                mode = SAMEORIGIN
            }
        }
    }
}
----
====

[[webflux-headers-xss-protection]]
== X-XSS-Protection
By default, Spring Security instructs browsers to block reflected XSS attacks using the <<headers-xss-protection,X-XSS-Protection header>.
You can disable `X-XSS-Protection` with the following Configuration:

.X-XSS-Protection Customization
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		// ...
		.headers(headers -> headers
			.xssProtection(xssProtection -> xssProtection.disable())
		);
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    return http {
        // ...
        headers {
            xssProtection {
                disable()
            }
        }
    }
}
----
====

[[webflux-headers-csp]]
== Content Security Policy (CSP)
Spring Security does not add xref:features/exploits/headers.adoc#headers-csp[Content Security Policy] by default, because a reasonable default is impossible to know without context of the application.
The web application author must declare the security policy(s) to enforce and/or monitor for the protected resources.

For example, given the following security policy:

.Content Security Policy Example
====
[source,http]
----
Content-Security-Policy: script-src 'self' https://trustedscripts.example.com; object-src https://trustedplugins.example.com; report-uri /csp-report-endpoint/
----
====

You can enable the CSP header as shown below:

.Content Security Policy
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		// ...
		.headers(headers -> headers
			.contentSecurityPolicy(policy -> policy
				.policyDirectives("script-src 'self' https://trustedscripts.example.com; object-src https://trustedplugins.example.com; report-uri /csp-report-endpoint/")
			)
		);
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    return http {
        // ...
        headers {
            contentSecurityPolicy {
                policyDirectives = "script-src 'self' https://trustedscripts.example.com; object-src https://trustedplugins.example.com; report-uri /csp-report-endpoint/"
            }
        }
    }
}
----
====

To enable the CSP `report-only` header, provide the following configuration:

.Content Security Policy Report Only
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		// ...
		.headers(headers -> headers
			.contentSecurityPolicy(policy -> policy
				.policyDirectives("script-src 'self' https://trustedscripts.example.com; object-src https://trustedplugins.example.com; report-uri /csp-report-endpoint/")
				.reportOnly()
			)
		);
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    return http {
        // ...
        headers {
            contentSecurityPolicy {
                policyDirectives = "script-src 'self' https://trustedscripts.example.com; object-src https://trustedplugins.example.com; report-uri /csp-report-endpoint/"
                reportOnly = true
            }
        }
    }
}
----
====

[[webflux-headers-referrer]]
== Referrer Policy

Spring Security does not add xref:features/exploits/headers.adoc#headers-referrer[Referrer Policy] headers by default.
You can enable the Referrer Policy header using configuration as shown below:

.Referrer Policy Configuration
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		// ...
		.headers(headers -> headers
			.referrerPolicy(referrer -> referrer
				.policy(ReferrerPolicy.SAME_ORIGIN)
			)
		);
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    return http {
        // ...
        headers {
            referrerPolicy {
                policy = ReferrerPolicy.SAME_ORIGIN
            }
        }
    }
}
----
====


[[webflux-headers-feature]]
== Feature Policy

Spring Security does not add xref:features/exploits/headers.adoc#headers-feature[Feature Policy] headers by default.
The following `Feature-Policy` header:

.Feature-Policy Example
====
[source]
----
Feature-Policy: geolocation 'self'
----
====

You can enable the Feature Policy header as shown below:

.Feature-Policy Configuration
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		// ...
		.headers(headers -> headers
			.featurePolicy("geolocation 'self'")
		);
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    return http {
        // ...
        headers {
            featurePolicy("geolocation 'self'")
        }
    }
}
----
====


[[webflux-headers-permissions]]
== Permissions Policy

Spring Security does not add xref:features/exploits/headers.adoc#headers-permissions[Permissions Policy] headers by default.
The following `Permissions-Policy` header:

.Permissions-Policy Example
====
[source]
----
Permissions-Policy: geolocation=(self)
----
====

You can enable the Permissions Policy header as shown below:

.Permissions-Policy Configuration
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		// ...
		.headers(headers -> headers
			.permissionsPolicy(permissions -> permissions
				.policy("geolocation=(self)")
			)
		);
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    return http {
        // ...
        headers {
            permissionsPolicy {
                policy = "geolocation=(self)"
            }
        }
    }
}
----
====


[[webflux-headers-clear-site-data]]
== Clear Site Data

Spring Security does not add xref:features/exploits/headers.adoc#headers-clear-site-data[Clear-Site-Data] headers by default.
The following Clear-Site-Data header:

.Clear-Site-Data Example
====
----
Clear-Site-Data: "cache", "cookies"
----
====

can be sent on log out with the following configuration:

.Clear-Site-Data Configuration
====
.Java
[source,java,role="primary"]
----
@Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	ServerLogoutHandler securityContext = new SecurityContextServerLogoutHandler();
	ClearSiteDataServerHttpHeadersWriter writer = new ClearSiteDataServerHttpHeadersWriter(CACHE, COOKIES);
	ServerLogoutHandler clearSiteData = new HeaderWriterServerLogoutHandler(writer);
	DelegatingServerLogoutHandler logoutHandler = new DelegatingServerLogoutHandler(securityContext, clearSiteData);

	http
		// ...
		.logout()
			.logoutHandler(logoutHandler);
	return http.build();
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun webFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
    val securityContext: ServerLogoutHandler = SecurityContextServerLogoutHandler()
    val writer = ClearSiteDataServerHttpHeadersWriter(CACHE, COOKIES)
    val clearSiteData: ServerLogoutHandler = HeaderWriterServerLogoutHandler(writer)
    val customLogoutHandler = DelegatingServerLogoutHandler(securityContext, clearSiteData)

    return http {
        // ...
        logout {
            logoutHandler = customLogoutHandler
        }
    }
}
----
====

[[webflux-headers-cross-origin-policies]]
== Cross-Origin Policies

Spring Security provides built-in support for adding some Cross-Origin policies headers, those headers are:

[source]
----
Cross-Origin-Opener-Policy
Cross-Origin-Embedder-Policy
Cross-Origin-Resource-Policy
----

Spring Security does not add <<headers-cross-origin-policies,Cross-Origin Policies>> headers by default.
The headers can be added with the following configuration:

.Cross-Origin Policies
====
.Java
[source,java,role="primary"]
----
@EnableWebFluxSecurity
@EnableWebFlux
public class WebSecurityConfig {

    @Bean
    SecurityWebFilterChain securityFilterChain(ServerHttpSecurity http) {
        http.headers((headers) -> headers
                .crossOriginOpenerPolicy(CrossOriginOpenerPolicy.SAME_ORIGIN)
                .crossOriginEmbedderPolicy(CrossOriginEmbedderPolicy.REQUIRE_CORP)
                .crossOriginResourcePolicy(CrossOriginResourcePolicy.SAME_ORIGIN));
        return http.build();
    }
}
----
.Kotlin
[source,kotlin,role="secondary"]
----
@EnableWebFluxSecurity
@EnableWebFlux
open class CrossOriginPoliciesCustomConfig {
    @Bean
    open fun springWebFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
        return http {
            headers {
                crossOriginOpenerPolicy(CrossOriginOpenerPolicy.SAME_ORIGIN)
                crossOriginEmbedderPolicy(CrossOriginEmbedderPolicy.REQUIRE_CORP)
                crossOriginResourcePolicy(CrossOriginResourcePolicy.SAME_ORIGIN)
            }
        }
    }
}
----
====

This configuration will write the headers with the values provided:
[source]
----
Cross-Origin-Opener-Policy: same-origin
Cross-Origin-Embedder-Policy: require-corp
Cross-Origin-Resource-Policy: same-origin
----
