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			78 lines
		
	
	
		
			3.2 KiB
		
	
	
	
		
			Plaintext
		
	
	
	
	
	
[[native-image-method-security]]
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= Method Security in GraalVM Native Image
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Although xref:servlet/authorization/method-security.adoc[Method Security] is supported in GraalVM Native Image, there are some use cases that need additional hints provided by the application.
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== Using `@PreAuthorize` and `@PostAuthorize` Annotations
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Using `@PreAuthorize` and `@PostAuthorize` annotations require additional hints if you have a custom implementation of `UserDetails` or `Authentication` classes.
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Let's take an example where you have a custom implementation of `UserDetails` class as follows and that implementation is returned by your `UserDetailsService`:
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.Custom Implementation of UserDetails
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[source,java]
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----
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public class CustomUserDetails implements UserDetails {
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    private final String username;
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    private final String password;
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    private final Collection<? extends GrantedAuthority> authorities;
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    public boolean isAdmin() {
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        return this.authorities.contains(new SimpleGrantedAuthority("ROLE_ADMIN"));
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    }
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    // constructors, getters and setters
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}
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----
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And you want to use the `isAdmin()` method inside a `@PreAuthorize` annotation as follows:
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.Using isAdmin() to secure a method
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[source,java]
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----
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@PreAuthorize("principal?.isAdmin()")
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public String hello() {
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    return "Hello!";
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}
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----
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[NOTE]
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====
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Remember that you need to xref:servlet/authorization/method-security.adoc#jc-enable-method-security[add `@EnableMethodSecurity` annotation] to your configuration class to enable method security annotations.
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====
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If you https://docs.spring.io/spring-boot/docs/current/reference/html/native-image.html#native-image.developing-your-first-application[run the native image] of your application with the above configuration, you will get an error similar to the following when trying to invoke the `hello()` method:
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[source]
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----
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failed: java.lang.IllegalArgumentException: Failed to evaluate expression 'principal?.isAdmin()' with root cause
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org.springframework.expression.spel.SpelEvaluationException: EL1004E: Method call: Method isAdmin() cannot be found on type com.mypackage.CustomUserDetails
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----
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Which means that the `isAdmin()` method cannot be found on the `CustomUserDetails` class.
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This is because Spring Security uses reflection to invoke the `isAdmin()` method and GraalVM Native Image does not support reflection by default.
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To fix this issue, you need to give hints to GraalVM Native Image to allow reflection on the `CustomUserDetails#isAdmin()` method.
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We can do that by providing a https://docs.spring.io/spring-boot/docs/current/reference/html/native-image.html#native-image.advanced.custom-hints[custom hint].
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In this example we are going to use {spring-framework-reference-url}core.html#core.aot.hints.register-reflection-for-binding[the `@RegisterReflectionForBinding` annotation].
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[NOTE]
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====
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You might need to register all your classes that you want to use in your `@PreAuthorize` and `@PostAuthorize` annotations.
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====
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.Using @RegisterReflectionForBinding
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[source,java]
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----
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@Configuration
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@RegisterReflectionForBinding(CustomUserDetails.class)
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public class MyConfiguration {
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    //...
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}
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----
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And that's it, now you can run the native image of your application and it should work as expected.
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