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

You can use xref:features/exploits/headers.adoc#headers[Security HTTP Response Headers] 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 use the headers, so additional testing is encouraged.

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

You can do so 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:


.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 that such things as CSS, JavaScript, and images are properly cached.

When using Spring WebFlux, you typically do so within your configuration.
You can find details on how to do so 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
By default, Spring Security includes xref:features/exploits/headers.adoc#headers-content-type-options[Content-Type] headers.
However, you can disable it:

.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)
By default, Spring Security provides the xref:features/exploits/headers.adoc#headers-hsts[Strict Transport Security] header.
However, you can customize the results explicitly.
For example, the following example explicitly provides 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 by using xref:features/exploits/headers.adoc#headers-frame-options[`X-Frame-Options`].

You can customize frame options to use the same origin:

.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 by using the <<headers-xss-protection,X-XSS-Protection header>.
You can disable `X-XSS-Protection`:

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

For example, consider 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/
----
====

Given the preceding policy, you can enable the CSP header:

.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

By default, Spring Security does not add xref:features/exploits/headers.adoc#headers-referrer[Referrer Policy] headers.
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

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

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

You can enable the preceding Feature Policy header:

.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

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

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

You can enable the preceding Permissions Policy header:

.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

By default, Spring Security does not add xref:features/exploits/headers.adoc#headers-clear-site-data[Clear-Site-Data] headers.
Consider the following `Clear-Site-Data` header:

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

You can send the `Clear-Site-Data` header on logout:

.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
        }
    }
}
----
====
