How to get BearerTokenAuthentication from SecurityContext in a GlobalFilter in Spring Cloud Gateway - spring

Question

Spring Cloud Gateway as a OAuth2ResourceServer with following Authorisation Config:
#Bean
SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
http
.authorizeExchange(exchanges ->
exchanges
.anyExchange().authenticated()
)
.oauth2ResourceServer(OAuth2ResourceServerSpec::jwt)
return http.build();
}
I have a global filter in place which is responsible for performing some functions at each valid authenticated request, something like this:
#Service
public class CustomGlobal implements GlobalFilter {
#Autowired
BearerTokenAuthentication authentication;
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
// access request headers, and perform some logic
// extract details from the JWT token, and perform some logic
log.info(authentication.getTokenAttributes.get("sub"));
// ^ in the above line there's a NullPointerException, since instance
// BearerTokenAuthentication is not set, or not visible at a GlobalFilter class
return chain.filter(exchange);
}
}
I am still in a learning phase. Any possible leads would be appreciated.

Answer 1

I did that this way(Note you should change WebFilter to GlobalFilter).
Add into your pom
<dependency>
<groupId>org.springframework.security</groupId>
<artifactId>spring-security-oauth2-jose</artifactId>
<version>5.4.6</version>
</dependency>
Then Filter should be like
package filter;
import lombok.extern.log4j.Log4j2;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.security.oauth2.core.DelegatingOAuth2TokenValidator;
import org.springframework.security.oauth2.jwt.*;
import org.springframework.util.StringUtils;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebFilter;
import org.springframework.web.server.WebFilterChain;
import reactor.core.publisher.Mono;
#Log4j2
public class CustomGlobal implements WebFilter {
public static final String HEADER_PREFIX = "Bearer ";
private final ReactiveJwtDecoder jwtDecoder;
public ReactiveJwtDecoder createDecoder(String issuer, String jwkUrl) {
var jwtDecoder = NimbusReactiveJwtDecoder.withJwkSetUri(jwkUrl).build();
jwtDecoder.setJwtValidator(new DelegatingOAuth2TokenValidator<>(
new JwtIssuerValidator(issuer),
new JwtTimestampValidator()));
return jwtDecoder;
}
protected CustomGlobal(String issuer, String jwkUrl) {
this.jwtDecoder = createDecoder(issuer, jwkUrl);
}
#Override
public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
return Mono
.defer(() -> {
var token = resolveToken(exchange.getRequest());
if (!StringUtils.hasText(token)) {
throw new BadJwtException("Authorisation token is invalid");
}
return jwtDecoder.decode(token);
})
.flatMap(tokenJwt -> {
log.info(tokenJwt.getClaimAsString("sub"));
return chain.filter(exchange);
})
.onErrorResume(err -> handleError(exchange));
}
private Mono<Void> handleError(ServerWebExchange exchange) {
exchange.getResponse().setRawStatusCode(HttpStatus.UNAUTHORIZED.value());
exchange.getResponse().getHeaders().add("Content-Type", "application/json");
return exchange.getResponse().setComplete();
}
private String resolveToken(ServerHttpRequest request) {
String bearerToken = request.getHeaders().getFirst(HttpHeaders.AUTHORIZATION);
if (StringUtils.hasText(bearerToken) && bearerToken.startsWith(HEADER_PREFIX)) {
return bearerToken.substring(7).trim();
}
return "";
}
}
Next step would be to create configuration
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.reactive.ReactorClientHttpConnector;
#Configuration
public class CustomGlobalConfig {
#Value("${jwt.iss}")
private String issuer;
#Value("${jwt.jwk-uri}")
private String jwkUrl;
#Bean
CustomGlobal createFilterBean() {
return new CustomGlobal(this.issuer, this.jwkUrl);
}
}