CVE-2023-36820: micronaut security has invalid IdTokenClaimsValidator logic on aud

Summary

IdTokenClaimsValidator skips aud claim validation if token is issued by same identity issuer/provider.

Details

See https://github.com/micronaut-projects/micronaut-security/blob/master/security-oauth2/src/main/java/io/micronaut/security/oauth2/client/IdTokenClaimsValidator.java#L202

This logic violates point 3 of https://openid.net/specs/openid-connect-core-10.html#IDTokenValidation.

Workaround exists by setting micronaut.security.token.jwt.claims-validators.audience with valid values. micronaut.security.token.jwt.claims-validators.openid-idtoken can be kept as default on.

PoC

Should probably be:

java return issuer.equalsIgnoreCase(iss) && audiences.contains(clientId) && validateAzp(claims, clientId, audiences);

Impact

Any OIDC setup using Micronaut where multiple OIDC applications exists for the same issuer but token auth are not meant to be shared.

Mitigation

Please upgrade to a patched micronaut-security-oauth2 release as soon as possible.

If you cannot upgrade, for example, if you are still using Micronaut Framework 2, you can patch your application by creating a replacement of IdTokenClaimsValidatorReplacement

java package cve;

import io.micronaut.context.annotation.Replaces; import io.micronaut.context.annotation.Requires; import io.micronaut.core.annotation.NonNull; import io.micronaut.core.util.StringUtils; import io.micronaut.security.config.SecurityConfigurationProperties; import io.micronaut.security.oauth2.client.IdTokenClaimsValidator; import io.micronaut.security.oauth2.configuration.OauthClientConfiguration; import io.micronaut.security.oauth2.configuration.OpenIdClientConfiguration; import io.micronaut.security.token.jwt.generator.claims.JwtClaims; import io.micronaut.security.token.jwt.validator.JwtClaimsValidatorConfigurationProperties;

import javax.inject.Singleton; import java.net.URL; import java.util.Collection; import java.util.List; import java.util.Optional;

@Requires(property = SecurityConfigurationProperties.PREFIX + ".authentication", value = "idtoken") @Requires(property = JwtClaimsValidatorConfigurationProperties.PREFIX + ".openid-idtoken", notEquals = StringUtils.FALSE) @Singleton @Replaces(IdTokenClaimsValidator.class) public class IdTokenClaimsValidatorReplacement extends IdTokenClaimsValidator { public IdTokenClaimsValidatorReplacement(Collection<OauthClientConfiguration> oauthClientConfigurations) { super(oauthClientConfigurations); }

@Override protected boolean validateIssuerAudienceAndAzp(@NonNull JwtClaims claims, @NonNull String iss, @NonNull List<String> audiences, @NonNull String clientId, @NonNull OpenIdClientConfiguration openIdClientConfiguration) { if (openIdClientConfiguration.getIssuer().isPresent()) { Optional<URL> issuerOptional = openIdClientConfiguration.getIssuer(); if (issuerOptional.isPresent()) { String issuer = issuerOptional.get().toString(); return issuer.equalsIgnoreCase(iss) && audiences.contains(clientId) && validateAzp(claims, clientId, audiences); } } return false; } }