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Refacoring test case for MisdirectedFilter #51443

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31 changes: 31 additions & 0 deletions quarkus/runtime/src/main/java/org/keycloak/quarkus/runtime/services/MisdirectedFilter.java
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Expand Up @@ -6,6 +6,37 @@
import io.vertx.core.Handler;
import io.vertx.ext.web.RoutingContext;

/**
* Defends against HTTP/2 connection coalescing delivering requests to the wrong backend.
*
* <p>When multiple hostnames share a TLS certificate (e.g. a wildcard cert behind a reverse proxy),
* browsers may reuse a single HTTP/2 connection for requests to different hostnames (RFC 9113 §9.1.1).
* In TLS passthrough mode the proxy routes by SNI, so all requests on a coalesced connection land on
* the backend selected during the original TLS handshake — even if the {@code :authority} names a
* different service. This filter returns HTTP 421 Misdirected Request for such requests, prompting
* the client to open a new connection with the correct SNI.
*
* <p>Only active in TLS passthrough mode (no proxy headers configured). Registered by
* {@link org.keycloak.quarkus.runtime.KeycloakRecorder#misdirectedRequestFilter}.
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*
* <p>Cases that pass through:
* <ul>
* <li>Plain HTTP requests — no TLS, no SNI to check.</li>
* <li>No {@code :authority} header — nothing to compare against.</li>
* <li>No SNI sent ({@code indicatedServerName()} is null) — happens with health checks
* or non-FQDN connections; rejecting these would break monitoring.</li>
* <li>SNI matches authority — the connection was established for this hostname.
* This also allows health checks that connect with an arbitrary hostname
* not configured in Keycloak.</li>
Comment on lines +26 to +30

@shawkins shawkins Aug 5, 2026

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Not sure if you want to mention it, but these account for all "backend" requests made directly to the Keycloak instance, not just monitoring.

* <li>Authority matches a configured Keycloak hostname ({@code hostname} or
* {@code hostname-admin}) — the request is legitimately for this server, even if
* the connection was originally established for a different hostname.</li>
Comment on lines +31 to +33

@shawkins shawkins Aug 5, 2026

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Might be worth mentioning here that we aren't yet trying to account for the realm front-end urls - and that 421s may erroneously occur then.

@ahus1 ahus1 Aug 6, 2026

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What are "realm front-end urls"? It seems that I missed that discussion :D

If I know what they are, I'm happy to add them.

@shawkins shawkins Aug 6, 2026

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Each realm can be configured to have its own frontend url -

keycloak/docs/documentation/server_admin/topics/realms/proc-using-admin-console.adoc

Line 38 in 29556d3

Click a question mark *?* icon to show the definition of a field such as *Frontend URL*.

The hostname provider looks for it here

keycloak/services/src/main/java/org/keycloak/url/HostnameV2Provider.java

Line 130 in 238204c

.map(r -> r.getAttribute("frontendUrl"))

* </ul>
*
* <p>Note: {@code indicatedServerName()} returns the SNI from the initial TLS handshake and is
* a per-connection value, not per-request. All HTTP/2 streams multiplexed on the same connection
* share it.
*/
public class MisdirectedFilter implements Handler<RoutingContext> {

private final Set<String> allowedHosts;
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58 changes: 0 additions & 58 deletions quarkus/tests/integration/src/test/java/org/keycloak/it/cli/dist/HttpDistTest.java
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Expand Up @@ -46,7 +46,6 @@
import io.vertx.core.http.HttpMethod;
import io.vertx.core.http.HttpVersion;
import io.vertx.core.http.RequestOptions;
import io.vertx.core.net.HostAndPort;
import io.vertx.core.net.SocketAddress;
import org.hamcrest.Matchers;
import org.junit.jupiter.api.BeforeEach;
Expand Down Expand Up @@ -102,63 +101,6 @@ public void preventNonNormalizedURLs() {
.when().get("/realms/master;xxx").then().statusCode(400);
}

@Test
@Launch({"start-dev", "--hostname=https://example.com"})
public void misdirectedRequestDetection() throws Exception {
Vertx vertx = Vertx.vertx();
try {
HttpClient client = vertx.createHttpClient(new HttpClientOptions()
.setSsl(true)
.setTrustAll(true)
.setVerifyHost(false)
.setProtocolVersion(HttpVersion.HTTP_2)
.setUseAlpn(true));
try {
assertThat("Matching indicated to authority is allowed",
misdirectedRequest(client, "servicehost.com", "servicehost.com", 8443), Matchers.is(200));

// null sniHostname → defaults to "localhost" (non-FQDN → Java skips SNI → indicatedServerName is null)
assertThat("No indicated name is allowed",
misdirectedRequest(client, null, "example.com", 443), Matchers.is(200));

// connection originated from another backend, but we're reusing it for a request to the keycloak server
assertThat("Matching a known host is allowed",
misdirectedRequest(client, "other-example.com", "example.com", 443), Matchers.is(200));

// connection originated from keycloak, but the browser is mistakenly reusing for another service
assertThat("Expected HTTP 421 Misdirected Request for SNI/authority mismatch",
misdirectedRequest(client, "example.com", "misdirected.com", 443), Matchers.is(421));
} finally {
client.close().toCompletionStage().toCompletableFuture().get(5, TimeUnit.SECONDS);
}
} finally {
vertx.close().toCompletionStage().toCompletableFuture().get(5, TimeUnit.SECONDS);
}
}

private static int misdirectedRequest(HttpClient client, String sniHostname, String authorityHost, int authorityPort) throws Exception {
RequestOptions options = new RequestOptions()
.setServer(SocketAddress.inetSocketAddress(8443, "localhost"))
.setPort(8443)
.setSsl(true)
.setURI("/realms/master")
.setMethod(HttpMethod.GET);

if (sniHostname != null) {
options.setHost(sniHostname);
}

return client.request(options)
.compose(req -> {
req.authority(HostAndPort.create(authorityHost, authorityPort));
return req.send();
})
.map(HttpClientResponse::statusCode)
.toCompletionStage()
.toCompletableFuture()
.get(10, TimeUnit.SECONDS);
}

@Test
@Launch({"start-dev"})
public void largeHeadersTest() throws Exception {
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114 changes: 114 additions & 0 deletions tests/base/src/test/java/org/keycloak/tests/ssl/MisdirectedRequestTest.java
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@@ -0,0 +1,114 @@
package org.keycloak.tests.ssl;

import java.util.concurrent.TimeUnit;

import org.keycloak.testframework.annotations.InjectKeycloakUrls;
import org.keycloak.testframework.annotations.KeycloakIntegrationTest;
import org.keycloak.testframework.https.CertificatesConfig;
import org.keycloak.testframework.https.CertificatesConfigBuilder;
import org.keycloak.testframework.https.InjectCertificates;
import org.keycloak.testframework.https.ManagedCertificates;
import org.keycloak.testframework.server.KeycloakServerConfig;
import org.keycloak.testframework.server.KeycloakServerConfigBuilder;
import org.keycloak.testframework.server.KeycloakUrls;

import io.vertx.core.Vertx;
import io.vertx.core.http.HttpClient;
import io.vertx.core.http.HttpClientOptions;
import io.vertx.core.http.HttpClientResponse;
import io.vertx.core.http.HttpMethod;
import io.vertx.core.http.HttpVersion;
import io.vertx.core.http.RequestOptions;
import io.vertx.core.net.HostAndPort;
import io.vertx.core.net.SocketAddress;
import org.junit.jupiter.api.Test;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.is;

/**
* Tests that the {@link org.keycloak.quarkus.runtime.services.MisdirectedFilter} returns HTTP 421 for misdirected HTTP/2 requests.
*/
@KeycloakIntegrationTest(config = MisdirectedRequestTest.ServerConfig.class)
class MisdirectedRequestTest {

@InjectCertificates(config = TlsEnabledConfig.class)
ManagedCertificates managedCertificates;

@InjectKeycloakUrls
KeycloakUrls keycloakUrls;

@Test
void misdirectedRequestDetection() throws Exception {
Vertx vertx = Vertx.vertx();
try {
HttpClient client = vertx.createHttpClient(new HttpClientOptions()
.setSsl(true)
.setTrustAll(true)
.setVerifyHost(false)
.setProtocolVersion(HttpVersion.HTTP_2)
.setUseAlpn(true));
try {
int port = keycloakUrls.getBaseUrl().getPort();

assertThat("Matching indicated to authority is allowed",
sendRequest(client, port, "servicehost.com", "servicehost.com", 8443), is(200));

// null sniHostname → defaults to "localhost" (non-FQDN → Java skips SNI → indicatedServerName is null)
assertThat("No indicated name is allowed",
sendRequest(client, port, null, "example.com", 443), is(200));

// connection originated from another backend, but we're reusing it for a request to the keycloak server
assertThat("Matching a known host is allowed",
sendRequest(client, port, "other-example.com", "example.com", 443), is(200));

// connection originated from keycloak, but the browser is mistakenly reusing for another service
assertThat("Expected HTTP 421 Misdirected Request for SNI/authority mismatch",
sendRequest(client, port, "example.com", "misdirected.com", 443), is(421));
} finally {
// Timeout set to minutes to allow manual debugging
client.close().toCompletionStage().toCompletableFuture().get(5, TimeUnit.MINUTES);
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}
} finally {
// Timeout set to minutes to allow manual debugging
vertx.close().toCompletionStage().toCompletableFuture().get(5, TimeUnit.MINUTES);
}
}

private int sendRequest(HttpClient client, int serverPort, String sniHostname, String authorityHost, int authorityPort) throws Exception {
RequestOptions options = new RequestOptions()
.setServer(SocketAddress.inetSocketAddress(serverPort, "localhost"))
.setPort(serverPort)
.setSsl(true)
.setURI("/realms/master")
.setMethod(HttpMethod.GET);

if (sniHostname != null) {
options.setHost(sniHostname);
}

return client.request(options)
.compose(req -> {
req.authority(HostAndPort.create(authorityHost, authorityPort));
return req.send();
})
.map(HttpClientResponse::statusCode)
.toCompletionStage()
.toCompletableFuture()
.get(10, TimeUnit.SECONDS);
}

static class ServerConfig implements KeycloakServerConfig {
@Override
public KeycloakServerConfigBuilder configure(KeycloakServerConfigBuilder config) {
return config.option("hostname", "https://example.com");
}
}

static class TlsEnabledConfig implements CertificatesConfig {
@Override
public CertificatesConfigBuilder configure(CertificatesConfigBuilder config) {
return config.tlsEnabled(true);
}
}
}
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