test(ap1): demonstrate token storage tradeoff

README.md

@@ -110,3 +110,20 @@ token은 명시적인 in-memory store에만 보관되므로 새로고침하면
 브라우저에서 `http://localhost:8088`을 열어 로그인한 뒤 보호 API를 호출할 수
 있습니다. SPA는 `http://localhost:8081/api/me`를 직접 호출하며 Spring
 Resource Server가 Bearer JWT를 검증합니다.
+
+Keycloak의 dedicated audience mapper는 `spa-public` access token에
+`keycloak-pattern-api`를 추가합니다. Spring은 signature, `iss`, `exp`뿐
+아니라 이 `aud`도 검사합니다. `verify-pattern1.sh`는 같은 정상 토큰을
+`deliberately-wrong-audience`를 기대하는 진단 인스턴스에도 제출해 `401`을
+확인합니다.
+
+Keycloak은 `KC_HOSTNAME=http://localhost:8080`을 기준으로 token의 `iss`를
+발급합니다. 정상 Resource Server는 이 외부 issuer 문자열을 검증하되 JWKS는
+Docker 내부의 `http://keycloak:8080`에서 가져옵니다. 진단 인스턴스는 일부러
+`http://wrong-issuer.invalid`를 기대하도록 구성되어, 서명과 audience가
+정상이더라도 issuer mismatch로 `401`을 반환합니다.
+
+token 저장 위치와 XSS 범위는
+[`docs/ap1-token-storage.md`](docs/ap1-token-storage.md)에 정리했습니다.
+E2E는 Web Storage token이 0개임과 동시에 실행 중 fetch hook이 Bearer
+header를 관찰할 수 있음을 재현합니다.

backend/src/main/java/com/example/keycloakpattern/AudienceValidator.java

@@ -0,0 +1,29 @@
+package com.example.keycloakpattern;
+
+import org.springframework.security.oauth2.core.OAuth2Error;
+import org.springframework.security.oauth2.core.OAuth2TokenValidator;
+import org.springframework.security.oauth2.core.OAuth2TokenValidatorResult;
+import org.springframework.security.oauth2.jwt.Jwt;
+
+final class AudienceValidator implements OAuth2TokenValidator<Jwt> {
+
+    private static final OAuth2Error MISSING_AUDIENCE = new OAuth2Error(
+        "invalid_token",
+        "The required resource audience is missing",
+        null
+    );
+
+    private final String expectedAudience;
+
+    AudienceValidator(String expectedAudience) {
+        this.expectedAudience = expectedAudience;
+    }
+
+    @Override
+    public OAuth2TokenValidatorResult validate(Jwt jwt) {
+        if (jwt.getAudience().contains(expectedAudience)) {
+            return OAuth2TokenValidatorResult.success();
+        }
+        return OAuth2TokenValidatorResult.failure(MISSING_AUDIENCE);
+    }
+}

backend/src/main/java/com/example/keycloakpattern/JwtDecoderConfig.java

@@ -0,0 +1,31 @@
+package com.example.keycloakpattern;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.oauth2.core.DelegatingOAuth2TokenValidator;
+import org.springframework.security.oauth2.core.OAuth2TokenValidator;
+import org.springframework.security.oauth2.jwt.Jwt;
+import org.springframework.security.oauth2.jwt.JwtDecoder;
+import org.springframework.security.oauth2.jwt.JwtValidators;
+import org.springframework.security.oauth2.jwt.NimbusJwtDecoder;
+
+@Configuration
+public class JwtDecoderConfig {
+
+    @Bean
+    JwtDecoder jwtDecoder(
+        @Value("${spring.security.oauth2.resourceserver.jwt.issuer-uri}") String issuer,
+        @Value("${spring.security.oauth2.resourceserver.jwt.jwk-set-uri}") String jwkSetUri,
+        @Value("${security.expected-audience}") String expectedAudience
+    ) {
+        NimbusJwtDecoder decoder = NimbusJwtDecoder.withJwkSetUri(jwkSetUri).build();
+        OAuth2TokenValidator<Jwt> issuerAndTimestamp =
+            JwtValidators.createDefaultWithIssuer(issuer);
+        OAuth2TokenValidator<Jwt> audience = new AudienceValidator(expectedAudience);
+        decoder.setJwtValidator(
+            new DelegatingOAuth2TokenValidator<>(issuerAndTimestamp, audience)
+        );
+        return decoder;
+    }
+}

backend/src/main/resources/application.yml

@@ -11,6 +11,9 @@ spring:
           issuer-uri: ${SPRING_SECURITY_OAUTH2_RESOURCESERVER_JWT_ISSUER_URI:http://localhost:8080/realms/keycloak-patterns}
           jwk-set-uri: ${SPRING_SECURITY_OAUTH2_RESOURCESERVER_JWT_JWK_SET_URI:http://localhost:8080/realms/keycloak-patterns/protocol/openid-connect/certs}
 
+security:
+  expected-audience: ${SECURITY_EXPECTED_AUDIENCE:keycloak-pattern-api}
+
 management:
   endpoint:
     health:

backend/src/test/java/com/example/keycloakpattern/AudienceValidatorTest.java

@@ -0,0 +1,49 @@
+package com.example.keycloakpattern;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.time.Instant;
+import java.util.List;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.security.oauth2.core.OAuth2TokenValidatorResult;
+import org.springframework.security.oauth2.jwt.Jwt;
+
+class AudienceValidatorTest {
+
+    private final AudienceValidator validator =
+        new AudienceValidator("keycloak-pattern-api");
+
+    @Test
+    void acceptsRequiredAudience() {
+        OAuth2TokenValidatorResult result = validator.validate(jwtWithAudience(
+            List.of("account", "keycloak-pattern-api")
+        ));
+
+        assertThat(result.hasErrors()).isFalse();
+    }
+
+    @Test
+    void rejectsForeignAudience() {
+        OAuth2TokenValidatorResult result = validator.validate(jwtWithAudience(
+            List.of("another-resource")
+        ));
+
+        assertThat(result.hasErrors()).isTrue();
+        assertThat(result.getErrors())
+            .extracting(error -> error.getErrorCode())
+            .containsExactly("invalid_token");
+    }
+
+    private Jwt jwtWithAudience(List<String> audience) {
+        Instant now = Instant.now();
+        return new Jwt(
+            "test-token",
+            now,
+            now.plusSeconds(300),
+            Map.of("alg", "none"),
+            Map.of("sub", "test-subject", "aud", audience)
+        );
+    }
+}

docker-compose.yml

@@ -86,6 +86,58 @@ services:
       - keycloak-net
     restart: unless-stopped
 
+  app-wrong-audience:
+    profiles:
+      - diagnostics
+    build:
+      context: ./backend
+    environment:
+      SERVER_PORT: "8081"
+      SPRING_SECURITY_OAUTH2_RESOURCESERVER_JWT_ISSUER_URI: http://localhost:8080/realms/keycloak-patterns
+      SPRING_SECURITY_OAUTH2_RESOURCESERVER_JWT_JWK_SET_URI: http://keycloak:8080/realms/keycloak-patterns/protocol/openid-connect/certs
+      SECURITY_EXPECTED_AUDIENCE: deliberately-wrong-audience
+    ports:
+      - "127.0.0.1:18081:8081"
+    depends_on:
+      keycloak:
+        condition: service_healthy
+    healthcheck:
+      test:
+        - CMD-SHELL
+        - wget -q -O - http://127.0.0.1:8081/actuator/health | grep -q '"status":"UP"'
+      interval: 10s
+      timeout: 5s
+      retries: 12
+      start_period: 20s
+    networks:
+      - keycloak-net
+
+  app-wrong-issuer:
+    profiles:
+      - diagnostics
+    build:
+      context: ./backend
+    environment:
+      SERVER_PORT: "8081"
+      SPRING_SECURITY_OAUTH2_RESOURCESERVER_JWT_ISSUER_URI: http://wrong-issuer.invalid/realms/keycloak-patterns
+      SPRING_SECURITY_OAUTH2_RESOURCESERVER_JWT_JWK_SET_URI: http://keycloak:8080/realms/keycloak-patterns/protocol/openid-connect/certs
+      SECURITY_EXPECTED_AUDIENCE: keycloak-pattern-api
+    ports:
+      - "127.0.0.1:18082:8081"
+    depends_on:
+      keycloak:
+        condition: service_healthy
+    healthcheck:
+      test:
+        - CMD-SHELL
+        - wget -q -O - http://127.0.0.1:8081/actuator/health | grep -q '"status":"UP"'
+      interval: 10s
+      timeout: 5s
+      retries: 12
+      start_period: 20s
+    networks:
+      - keycloak-net
+
   nginx:
     build:
       context: ./frontend

docs/ap1-token-storage.md

@@ -0,0 +1,29 @@
+# AP1 token storage trade-off
+
+AP1에서는 `access_token`, `refresh_token`, `id_token`을
+`oidc-client-ts`의 명시적인 `InMemoryWebStorage`에만 보관한다.
+`localStorage`와 `sessionStorage`에는 OAuth token을 저장하지 않는다.
+
+full-page authorization redirect를 생존해야 하는 일회성 transaction
+state와 PKCE verifier만 `sessionStorage`를 사용한다. callback 성공 후
+라이브러리가 해당 transaction state를 제거한다.
+
+| 저장 위치 | reload 생존 | JavaScript 접근 | AP1 선택 |
+|---|---:|---:|---:|
+| 메모리 | 아니요 | 실행 중 가능 | 사용 |
+| `sessionStorage` | 같은 탭에서 가능 | 가능 | token 저장 금지 |
+| `localStorage` | 예 | 가능 | token 저장 금지 |
+| HttpOnly cookie | 가능 | raw token 접근 불가 | AP2/AP3의 서버 소유 경계 |
+
+메모리 저장은 XSS를 제거하지 않는다. 악성 스크립트가 실행 중 `fetch`를
+후킹하면 SPA가 붙이는 `Authorization: Bearer ...` 헤더를 관찰할 수 있다.
+다만 persistent storage를 사용하지 않으므로 reload 이후 탈취 가능한 token
+복사본이 남지 않는다.
+
+`e2e/pattern1.mjs`는 다음 두 조건을 동시에 검증한다.
+
+1. access token이 Web Storage 어디에도 존재하지 않는다.
+2. 실행 중 fetch hook은 Bearer token을 관찰할 수 있다.
+
+따라서 결론은 “메모리면 XSS에 안전”이 아니라 “영속 탈취 범위를 줄이지만
+실행 중 XSS에는 여전히 노출”이다.

e2e/pattern1.mjs

@@ -36,8 +36,40 @@ try {
   assert.equal(authorizationUrl?.searchParams.get("code_challenge_method"), "S256");
   assert.ok(authorizationUrl?.searchParams.get("code_challenge"));
 
-  const accessToken = await page.evaluate(() => window.__pattern1.getAccessToken());
-  assert.ok(accessToken, "access token must exist in browser memory");
+  await page.evaluate(() => {
+    const originalFetch = window.fetch.bind(window);
+    window.__xssProbe = { authorization: null };
+    window.fetch = (input, init = {}) => {
+      const headers = new Headers(
+        init.headers ?? (input instanceof Request ? input.headers : undefined),
+      );
+      const authorization = headers.get("Authorization");
+      if (authorization) {
+        window.__xssProbe.authorization = authorization;
+      }
+      return originalFetch(input, init);
+    };
+  });
+
+  await page.locator("#call-api").click();
+  await page.waitForFunction(() => {
+    const text = document.querySelector("#result")?.textContent ?? "";
+    return text.includes('"httpStatus": 200');
+  });
+
+  const capturedAuthorization = await page.evaluate(
+    () => window.__xssProbe.authorization,
+  );
+  assert.match(capturedAuthorization, /^Bearer /u);
+  const accessToken = capturedAuthorization.slice("Bearer ".length);
+  const payload = JSON.parse(
+    Buffer.from(accessToken.split(".")[1], "base64url").toString("utf8"),
+  );
+  const audiences = Array.isArray(payload.aud) ? payload.aud : [payload.aud];
+  assert.ok(
+    audiences.includes("keycloak-pattern-api"),
+    "access token must target keycloak-pattern-api",
+  );
 
   const storageSnapshot = await page.evaluate(() => ({
     localStorage: Object.values(localStorage),
@@ -48,23 +80,49 @@ try {
     false,
     "access token must not be persisted in Web Storage",
   );
+  assert.ok(
+    capturedAuthorization,
+    "runtime XSS-style fetch hooking can still observe a memory-only bearer token",
+  );
 
-  await page.locator("#call-api").click();
-  await page.waitForFunction(() => {
-    const text = document.querySelector("#result")?.textContent ?? "";
-    return text.includes('"httpStatus": 200');
-  });
+  if (process.env.WRONG_AUDIENCE_URL) {
+    const response = await fetch(process.env.WRONG_AUDIENCE_URL, {
+      headers: { Authorization: `Bearer ${accessToken}` },
+    });
+    assert.equal(
+      response.status,
+      401,
+      "the same signed token must fail when the Resource Server expects another audience",
+    );
+  }
+
+  if (process.env.WRONG_ISSUER_URL) {
+    const response = await fetch(process.env.WRONG_ISSUER_URL, {
+      headers: { Authorization: `Bearer ${accessToken}` },
+    });
+    assert.equal(
+      response.status,
+      401,
+      "the same signed token must fail when the Resource Server expects another issuer",
+    );
+  }
 
   await page.reload();
   await page.locator('[data-authenticated="false"]').waitFor();
   assert.equal(
-    await page.evaluate(() => window.__pattern1.getAccessToken()),
-    null,
-    "reload must clear the memory-only token",
+    await page.evaluate(
+      (token) => JSON.stringify({
+        localStorage: Object.values(localStorage),
+        sessionStorage: Object.values(sessionStorage),
+      }).includes(token),
+      accessToken,
+    ),
+    false,
+    "reload must clear the memory-only token without persisting it",
   );
 
   console.log(
-    "pattern1 browser verified: code+PKCE S256, protected API 200, Web Storage token 0, reload clears token",
+    "pattern1 browser verified: PKCE, audience/issuer negatives, persistent token 0, runtime fetch hook observes bearer, reload clears token",
   );
 } finally {
   await browser.close();

frontend/src/app.js

@@ -122,13 +122,6 @@ userManager.events.addUserLoaded(renderSession);
 userManager.events.addUserUnloaded(() => renderSession(null));
 userManager.events.addAccessTokenExpired(() => renderSession(null));
 
-window.__pattern1 = {
-  getAccessToken: () => currentUser?.access_token ?? null,
-  getRefreshToken: () => currentUser?.refresh_token ?? null,
-  getIdToken: () => currentUser?.id_token ?? null,
-  callProtectedApi,
-};
-
 try {
   const callbackUser = await finishSigninCallback();
   renderSession(callbackUser ?? await userManager.getUser());

keycloak/import/keycloak-patterns-realm.json

@@ -51,7 +51,22 @@
       "attributes": {
         "pkce.code.challenge.method": "S256",
         "post.logout.redirect.uris": "http://localhost:8088/*##http://127.0.0.1:8088/*"
-      }
+      },
+      "protocolMappers": [
+        {
+          "name": "keycloak-pattern-api-audience",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-audience-mapper",
+          "consentRequired": false,
+          "config": {
+            "included.custom.audience": "keycloak-pattern-api",
+            "id.token.claim": "false",
+            "access.token.claim": "true",
+            "userinfo.token.claim": "false",
+            "introspection.token.claim": "true"
+          }
+        }
+      ]
     },
     {
       "clientId": "token-mediating-confidential",

scripts/validate-realm.py

@@ -70,6 +70,18 @@ def validate(path: Path, runtime: bool) -> None:
         spa.get("attributes", {}).get("pkce.code.challenge.method") == "S256",
         "spa-public must enforce PKCE S256",
     )
+    audience_mappers = [
+        mapper
+        for mapper in spa.get("protocolMappers", [])
+        if mapper.get("protocolMapper") == "oidc-audience-mapper"
+    ]
+    if not runtime:
+        require(len(audience_mappers) == 1, "spa-public must declare one audience mapper")
+        require(
+            audience_mappers[0].get("config", {}).get("included.custom.audience")
+            == "keycloak-pattern-api",
+            "spa-public access token must target keycloak-pattern-api",
+        )
 
     for client_id, placeholder in CONFIDENTIAL_CLIENTS.items():
         client = clients[client_id]

scripts/verify-pattern1.sh

@@ -12,10 +12,15 @@ set +a
 
 docker compose down --volumes --remove-orphans
 docker compose up --build -d --wait
+docker compose --profile diagnostics up -d --wait \
+  app-wrong-audience \
+  app-wrong-issuer
 
 npm --prefix e2e ci
 E2E_USERNAME=regular-user \
 E2E_PASSWORD="$REGULAR_USER_PASSWORD" \
+WRONG_AUDIENCE_URL=http://localhost:18081/api/me \
+WRONG_ISSUER_URL=http://localhost:18082/api/me \
   npm --prefix e2e run test:pattern1
 
 echo "AP1 verified end to end"