feat: add validated Traefik ForwardAuth alternative

# Conflicts:
#	.env.example

.env.example

@@ -10,6 +10,8 @@ POSTGRES_PASSWORD=change-me-postgres-password
 TOKEN_MEDIATING_CLIENT_SECRET=change-me-token-mediating-client-secret
 BFF_CLIENT_SECRET=change-me-bff-client-secret
 EDGE_PROXY_CLIENT_SECRET=change-me-edge-proxy-client-secret
+OAUTH2_PROXY_COOKIE_SECRET=generate-a-base64-encoded-32-byte-secret
+INTERNAL_AUTH_TOKEN=generate-a-long-random-edge-to-backend-token
 MOCK_GOOGLE_BROKER_CLIENT_SECRET=change-me-mock-google-broker-client-secret
 ADMIN_USER_PASSWORD=change-me-admin-user-password
 REGULAR_USER_PASSWORD=change-me-regular-user-password

.gitignore

@@ -4,6 +4,8 @@
 *.iml
 
 backend/target/
+**/node_modules/
+frontend/dist/
 build/
 e2e/node_modules/
 google-e2e/node_modules/

README.md

@@ -103,3 +103,22 @@ Keycloak을 잠시 중지하고 export한 뒤 자동으로 다시 올립니다.
 
 runtime export에는 실제 client secret과 credential hash가 포함될 수 있어
 gitignored `build/keycloak-export/`에 권한 `0600`으로만 저장됩니다.
+
+## AP4: oauth2-proxy Edge Forward Auth
+
+`develop-keycloak-pattern4`는 oauth2-proxy와 Nginx `auth_request`가
+인증을 edge에서 강제하는 패턴입니다.
+
+```bash
+./scripts/verify-pattern4.sh
+```
+
+첫 feature에서는 oauth2-proxy를 `http://localhost:4180`에 직접 노출해
+OIDC redirect/PKCE/callback과 forwarded-user를 분리 확인합니다. 두 번째
+feature부터 `http://localhost:8088` Nginx가 단일 진입점이며, 내부
+`auth_request`는 브라우저 요청을 login 302로, API 요청을 JSON 401로
+구분합니다. 최종 feature에서는 backend와 oauth2-proxy의 호스트 노출을
+제거하고 Nginx 헤더 덮어쓰기와 내부 토큰 검증으로 spoofing을 막습니다.
+자세한 내용은
+[`docs/ap4-edge-forward-auth.md`](docs/ap4-edge-forward-auth.md)를
+참고하세요.

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

@@ -0,0 +1,59 @@
+package com.example.keycloakpattern;
+
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import jakarta.servlet.http.HttpServletRequest;
+
+import org.springframework.http.ResponseEntity;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class EdgeIdentityController {
+
+    private final byte[] internalAuthToken;
+
+    EdgeIdentityController(@Value("${edge.internal-auth-token}") String internalAuthToken) {
+        if (!hasText(internalAuthToken)) {
+            throw new IllegalStateException("edge.internal-auth-token must be configured");
+        }
+        this.internalAuthToken = internalAuthToken.getBytes(StandardCharsets.UTF_8);
+    }
+
+    @GetMapping("/edge/me")
+    ResponseEntity<Map<String, Object>> currentUser(HttpServletRequest request) {
+        String authRequestUser = request.getHeader("X-Auth-Request-User");
+        if (!hasText(authRequestUser) || !hasValidInternalToken(request)) {
+            return ResponseEntity.status(401).body(Map.of(
+                "error",
+                "trusted edge authentication is required"
+            ));
+        }
+
+        Map<String, Object> response = new LinkedHashMap<>();
+        response.put("pattern", "AP4-edge-forward-auth");
+        response.put("user", authRequestUser);
+        response.put("email", request.getHeader("X-Auth-Request-Email"));
+        response.put("identityHeader", "X-Auth-Request-User");
+        return ResponseEntity.ok(response);
+    }
+
+    private boolean hasValidInternalToken(HttpServletRequest request) {
+        String suppliedToken = request.getHeader("X-Internal-Auth-Token");
+        if (!hasText(suppliedToken)) {
+            return false;
+        }
+        return MessageDigest.isEqual(
+            internalAuthToken,
+            suppliedToken.getBytes(StandardCharsets.UTF_8)
+        );
+    }
+
+    private static boolean hasText(String value) {
+        return value != null && !value.isBlank();
+    }
+}

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

@@ -17,7 +17,12 @@ public class SecurityConfig {
             .sessionManagement(session ->
                 session.sessionCreationPolicy(SessionCreationPolicy.STATELESS))
             .authorizeHttpRequests(authorize -> authorize
-                .requestMatchers("/actuator/health", "/actuator/health/**", "/api/public")
+                .requestMatchers(
+                    "/actuator/health",
+                    "/actuator/health/**",
+                    "/api/public",
+                    "/edge/**"
+                )
                 .permitAll()
                 .anyRequest()
                 .authenticated())

backend/src/main/resources/application.yml

@@ -1,6 +1,9 @@
 server:
   port: ${SERVER_PORT:8081}
 
+edge:
+  internal-auth-token: ${EDGE_INTERNAL_AUTH_TOKEN:}
+
 spring:
   application:
     name: keycloak-pattern-api

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

@@ -11,7 +11,7 @@ import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMock
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.test.web.servlet.MockMvc;
 
-@SpringBootTest
+@SpringBootTest(properties = "edge.internal-auth-token=test-internal-edge-token")
 @AutoConfigureMockMvc
 class ApiSecurityTest {
 
@@ -40,4 +40,36 @@ class ApiSecurityTest {
             .andExpect(jsonPath("$.subject").value("test-subject"))
             .andExpect(jsonPath("$.username").value("regular-user"));
     }
+
+    @Test
+    void edgeEndpointRejectsMissingTrustedHeaders() throws Exception {
+        mockMvc.perform(get("/edge/me"))
+            .andExpect(status().isUnauthorized());
+    }
+
+    @Test
+    void edgeEndpointRejectsForgedIdentityWithoutInternalToken() throws Exception {
+        mockMvc.perform(get("/edge/me")
+                .header("X-Auth-Request-User", "spoofed-admin"))
+            .andExpect(status().isUnauthorized());
+    }
+
+    @Test
+    void edgeEndpointRejectsWrongInternalToken() throws Exception {
+        mockMvc.perform(get("/edge/me")
+                .header("X-Auth-Request-User", "spoofed-admin")
+                .header("X-Internal-Auth-Token", "wrong-token"))
+            .andExpect(status().isUnauthorized());
+    }
+
+    @Test
+    void edgeEndpointAcceptsIdentityFromTrustedEdge() throws Exception {
+        mockMvc.perform(get("/edge/me")
+                .header("X-Auth-Request-User", "regular-user")
+                .header("X-Auth-Request-Email", "regular-user@example.test")
+                .header("X-Internal-Auth-Token", "test-internal-edge-token"))
+            .andExpect(status().isOk())
+            .andExpect(jsonPath("$.user").value("regular-user"))
+            .andExpect(jsonPath("$.identityHeader").value("X-Auth-Request-User"));
+    }
 }

deploy/traefik/dynamic.yml

@@ -0,0 +1,35 @@
+http:
+  routers:
+    oauth:
+      entryPoints:
+        - web
+      rule: PathPrefix(`/oauth2/`)
+      service: oauth2-proxy
+      priority: 100
+    application:
+      entryPoints:
+        - web
+      rule: PathPrefix(`/`)
+      middlewares:
+        - keycloak-forward-auth
+      service: application
+
+  middlewares:
+    keycloak-forward-auth:
+      forwardAuth:
+        address: http://oauth2-proxy:4180/oauth2/auth
+        trustForwardHeader: false
+        authResponseHeaders:
+          - X-Auth-Request-User
+          - X-Auth-Request-Email
+          - Set-Cookie
+
+  services:
+    oauth2-proxy:
+      loadBalancer:
+        servers:
+          - url: http://oauth2-proxy:4180
+    application:
+      loadBalancer:
+        servers:
+          - url: http://app:8081

deploy/traefik/traefik.yml

@@ -0,0 +1,14 @@
+entryPoints:
+  web:
+    address: ":8080"
+
+providers:
+  file:
+    filename: /etc/traefik/dynamic.yml
+    watch: false
+
+api:
+  dashboard: false
+
+log:
+  level: INFO

docker-compose.yml

@@ -71,8 +71,9 @@ services:
       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
-    ports:
-      - "127.0.0.1:8081:8081"
+      EDGE_INTERNAL_AUTH_TOKEN: ${INTERNAL_AUTH_TOKEN:?set INTERNAL_AUTH_TOKEN in .env}
+    expose:
+      - "8081"
     depends_on:
       keycloak:
         condition: service_healthy
@@ -88,13 +89,68 @@ services:
       - keycloak-net
     restart: unless-stopped
 
+  oauth2-proxy:
+    image: quay.io/oauth2-proxy/oauth2-proxy:v7.15.2
+    command:
+      - --http-address=0.0.0.0:4180
+      - --provider=keycloak-oidc
+      - --oidc-issuer-url=http://localhost:8080/realms/keycloak-patterns
+      - --skip-oidc-discovery=true
+      - --login-url=http://localhost:8080/realms/keycloak-patterns/protocol/openid-connect/auth
+      - --redeem-url=http://keycloak:8080/realms/keycloak-patterns/protocol/openid-connect/token
+      - --oidc-jwks-url=http://keycloak:8080/realms/keycloak-patterns/protocol/openid-connect/certs
+      - --profile-url=http://keycloak:8080/realms/keycloak-patterns/protocol/openid-connect/userinfo
+      - --validate-url=http://keycloak:8080/realms/keycloak-patterns/protocol/openid-connect/userinfo
+      - --redirect-url=http://localhost:8088/oauth2/callback
+      - --upstream=http://app:8081
+      - --email-domain=*
+      - --scope=openid profile email
+      - --code-challenge-method=S256
+      - --reverse-proxy=true
+      - --trusted-proxy-ip=172.30.40.10/32
+      - --cookie-name=AP4_SESSION
+      - --cookie-secure=false
+      - --cookie-samesite=lax
+      - --cookie-expire=1h
+      - --session-cookie-minimal=true
+      - --skip-provider-button=true
+      - --set-xauthrequest=true
+      - --pass-user-headers=true
+      - --whitelist-domain=localhost:8088
+      - --whitelist-domain=localhost:8080
+    environment:
+      OAUTH2_PROXY_CLIENT_ID: edge-proxy
+      OAUTH2_PROXY_CLIENT_SECRET: ${EDGE_PROXY_CLIENT_SECRET:?set EDGE_PROXY_CLIENT_SECRET in .env}
+      OAUTH2_PROXY_COOKIE_SECRET: ${OAUTH2_PROXY_COOKIE_SECRET:?set OAUTH2_PROXY_COOKIE_SECRET in .env}
+    expose:
+      - "4180"
+    depends_on:
+      keycloak:
+        condition: service_healthy
+      app:
+        condition: service_healthy
+    healthcheck:
+      test:
+        - CMD
+        - /bin/oauth2-proxy
+        - --version
+      interval: 10s
+      timeout: 5s
+      retries: 3
+      start_period: 5s
+    networks:
+      - keycloak-net
+    restart: unless-stopped
+
   nginx:
     build:
       context: ./frontend
+    environment:
+      INTERNAL_AUTH_TOKEN: ${INTERNAL_AUTH_TOKEN:?set INTERNAL_AUTH_TOKEN in .env}
     ports:
       - "127.0.0.1:${NGINX_PORT:-8088}:80"
     depends_on:
-      app:
+      oauth2-proxy:
         condition: service_healthy
     healthcheck:
       test:
@@ -104,7 +160,8 @@ services:
       timeout: 5s
       retries: 12
     networks:
-      - keycloak-net
+      keycloak-net:
+        ipv4_address: 172.30.40.10
     restart: unless-stopped
 
 volumes:
@@ -114,3 +171,6 @@ volumes:
 networks:
   keycloak-net:
     driver: bridge
+    ipam:
+      config:
+        - subnet: 172.30.40.0/24

docs/ap4-edge-forward-auth.md

@@ -0,0 +1,70 @@
+# AP4 · oauth2-proxy Edge Forward Auth
+
+## 첫 단계: oauth2-proxy 자체 OIDC 흐름
+
+`feature/keycloak-oauth2-proxy-oidc-flow`에서는 oauth2-proxy를
+`http://localhost:4180`에 직접 노출해 구성 요소를 분리해서 확인합니다.
+
+1. `/edge/me` 미인증 요청이 Keycloak로 redirect됩니다.
+2. oauth2-proxy는 confidential `edge-proxy` client와 PKCE S256을 사용합니다.
+3. callback에서 code/token 교환과 ID/access token 검증은 서버끼리
+   수행합니다.
+4. 브라우저에는 HttpOnly `AP4_SESSION` cookie만 남습니다.
+5. oauth2-proxy가 backend 요청에 `X-Forwarded-User`를 붙여 200을 받습니다.
+
+Keycloak이 발급하는 issuer는 브라우저 기준
+`http://localhost:8080/realms/keycloak-patterns`입니다. 컨테이너 내부의
+`localhost`는 oauth2-proxy 자신이므로 discovery endpoint에 도달할 수
+없습니다. 그래서 이 로컬 Compose 구성은 issuer 검증값은 외부 URL로
+유지하되, login URL은 브라우저용 외부 주소, token/JWKS/userinfo는
+`http://keycloak:8080` 내부 주소로 각각 명시합니다.
+
+HTTP 로컬 시연이라 `cookie-secure=false`를 사용합니다. 운영 HTTPS에서는
+반드시 secure cookie로 되돌려야 합니다.
+
+## 다음 단계의 보안 전제
+
+이 첫 feature의 backend는 전달된 사용자 헤더를 신뢰하며 8081도
+loopback에 publish되어 있습니다. 따라서 로컬에서 직접
+`X-Forwarded-User: spoofed-admin`을 보내면 우회가 재현됩니다. 이후
+Nginx `auth_request` 통합을 거쳐 최종 feature에서 backend no-publish와
+내부 shared-secret 검증을 함께 적용합니다.
+
+## 두 번째 단계: Nginx `auth_request`
+
+`feature/keycloak-nginx-auth-request-integration`부터 외부 진입점은
+`http://localhost:8088` Nginx 하나입니다. oauth2-proxy의 4180 포트는
+Compose 네트워크에만 expose됩니다.
+
+- Nginx의 정확 일치 `location = /oauth2/auth`는 `internal`이라 외부에서
+  직접 호출할 수 없습니다.
+- 인증 서브리퀘스트에는 본문을 보내지 않고 `Content-Length`도
+  비웁니다.
+- 일반 브라우저 요청의 401은 `/oauth2/start` 302로 변환합니다.
+- API 요청 `/api/edge`는 redirect하지 않고 JSON 401을 반환합니다.
+- 인증 성공 시 oauth2-proxy의 `X-Auth-Request-User`와 email만 backend로
+  전달합니다.
+
+Nginx 컨테이너 IP를 전용 Compose subnet에서 고정하고 oauth2-proxy의
+trusted proxy를 그 단일 IP로 제한합니다. 다만 이 단계에서는 backend
+8081이 로컬 호스트에 열려 있어 신뢰 헤더를 직접 위조할 수 있습니다.
+그 재현 조건은 마지막 feature에서 제거합니다.
+
+## 마지막 단계: 신뢰 경계와 헤더 스푸핑 방어
+
+`feature/keycloak-header-spoofing-defense`에서는 신뢰 경계를 실제
+네트워크와 application 양쪽에서 강제합니다.
+
+1. backend 8081과 oauth2-proxy 4180은 host에 publish하지 않습니다.
+   브라우저가 접근 가능한 application 포트는 Nginx 8088뿐입니다.
+2. Nginx는 client가 보낸 `X-Auth-Request-User`, email, 내부 토큰을
+   그대로 전달하지 않고 oauth2-proxy 결과와 server-side 토큰으로
+   항상 덮어씁니다.
+3. backend는 `X-Auth-Request-User`와 `X-Internal-Auth-Token`이 모두
+   유효할 때만 edge identity를 받아들이며 token은 constant-time으로
+   비교합니다.
+
+shared token은 방어 심층화 수단입니다. 운영에서는 Secret Manager나
+orchestrator secret으로 주입하고 주기적으로 교체해야 합니다. 서비스
+간 mTLS 또는 service mesh identity를 사용할 수 있다면 단순 shared
+token보다 강한 workload identity로 대체하는 편이 좋습니다.

docs/edge-forwardauth-google-federation.md

@@ -0,0 +1,26 @@
+# AP4 edge forward-auth with Google federation
+
+Google federation은 AP4의 edge contract를 바꾸지 않는다.
+
+```text
+Browser -> nginx -> oauth2-proxy -> Keycloak -> Google
+Browser <- AP4_SESSION <- oauth2-proxy <- Keycloak
+nginx -> trusted identity headers -> upstream app
+```
+
+oauth2-proxy가 신뢰하는 issuer는 Google이 아니라 Keycloak이다. Google ID
+token은 Keycloak broker 경계 안에서 검증되고, oauth2-proxy는 Keycloak
+authorization code/token과 session cookie만 다룬다. upstream 앱도
+broker 여부와 무관하게 동일한 trusted headers를 받는다.
+
+`verify-edge-google-federation.sh`는 mock Google 로그인, confidential
+server-side token 교환(브라우저에 token 요청 없음), 미검증 broker email 거부,
+Keycloak email verification 완료 후 HttpOnly edge cookie와 brokered
+subject/email header를 실제 컨테이너와 브라우저로 검증한다. minimal session의
+`X-Auth-Request-User`는 표시용 username이 아니라 Keycloak의 안정적인 local
+subject UUID이며, 화면 이름이 필요하면 별도 허용 header를 명시한다.
+
+brokered token/claims가 client-side session cookie의 4KB 한계를 넘지 않도록
+oauth2-proxy에는 `session-cookie-minimal=true`를 적용한다. AP4 upstream은
+token forwarding이 아니라 trusted identity headers만 사용하므로 cookie에
+access/refresh/ID token을 보관할 필요가 없다.

docs/edge-forwardauth-no-google.md

@@ -0,0 +1,20 @@
+# AP4 edge forward-auth: local identity profile
+
+nginx의 `auth_request`가 oauth2-proxy `/oauth2/auth`를 호출하고, 미인증
+브라우저만 Keycloak로 redirect한다. oauth2-proxy는 confidential
+`edge-proxy` client로 code를 교환하며 browser에는 HttpOnly session cookie만
+남긴다.
+
+Google이 없어도 이 경계는 완전히 동작한다. 사용자는 Keycloak local
+credential로 로그인하고 upstream 애플리케이션은 OAuth/OIDC를 몰라도 된다.
+
+보안 경계:
+
+- backend와 oauth2-proxy 포트를 host에 publish하지 않는다.
+- 외부에서 받은 identity header를 nginx가 제거·덮어쓴다.
+- backend는 trusted nginx가 주입하는 별도 internal token도 확인한다.
+- 브라우저가 직접 호출한 `/oauth2/auth`는 공개하지 않는다.
+
+`verify-edge-no-google-profile.sh`는 Compose와 nginx 계약을 검사하고,
+`verify-pattern4.sh`는 실제 local-user 브라우저 흐름과 spoofing 방어를
+검증한다.

docs/four-pattern-tradeoff-matrix.md

@@ -0,0 +1,37 @@
+# Four Keycloak integration patterns
+
+| 축 | AP1 SPA direct | AP2 token mediator | AP3 BFF | AP4 edge auth |
+|---|---|---|---|---|
+| OAuth client | public | confidential | confidential | confidential proxy |
+| browser 보유물 | access/refresh token | 짧은 handoff code 또는 app token | HttpOnly session cookie | proxy session cookie |
+| OAuth code 교환 | browser + PKCE | mediator backend | BFF | oauth2-proxy |
+| API bearer 검증 | Spring resource server | mediator/downstream API | BFF 내부 또는 downstream | edge가 인증 후 trusted header |
+| server session | 없음 | handoff 상태만 짧게 | 필수 | proxy cookie/session |
+| XSS token 탈취면 | 가장 큼 | 축소 | browser token 제거 | browser token 제거 |
+| CSRF 주의 | token endpoint/refresh 설계 | app cookie 사용 시 | 필수 방어 | proxy cookie 사용 시 |
+| 수평 확장 상태 | 단순 | handoff store 공유 가능 | session store 필요 | proxy 설정에 따름 |
+| 주 학습 포인트 | PKCE/JWT/RS | token 경계·one-time handoff | oauth2Login/session/CSRF | auth_request/header trust |
+
+## 선택 기준
+
+- 브라우저에서 OAuth와 token 수명주기를 직접 학습하려면 AP1.
+- 브라우저에 upstream token을 주지 않되 API 호출은 bearer 중심으로 유지하려면
+  AP2.
+- token을 browser에서 완전히 제거하고 애플리케이션 단위 인가·세션을
+  중앙화하려면 AP3.
+- 기존 upstream을 수정하기 어렵고 경계에서 일괄 인증하려면 AP4.
+
+Google federation은 다섯 번째 인증 패턴이 아니다. 네 패턴 모두 최종적으로
+Keycloak token/session을 소비하며, Google은 Keycloak 앞의 upstream IdP
+hop으로 추가된다.
+
+## 이 repository의 실행 증거
+
+- AP1: PKCE SPA, issuer/audience, token storage, refresh/logout 검증
+- AP2: confidential client와 one-time access handoff 검증
+- AP3: `oauth2Login` session과 CSRF/SameSite 검증
+- AP4: oauth2-proxy, nginx `auth_request`, spoofed header 제거 검증
+- 공통: local mock Google brokering, First Broker Login, claim/role mapping 검증
+
+각 근거 브랜치와 병합 여부는 `keycloak-branch-manifest.tsv` 및
+`audit-keycloak-branches.sh`로 추적한다.

docs/traefik-forwardauth-alternative.md

@@ -0,0 +1,22 @@
+# Traefik ForwardAuth alternative
+
+Traefik의 `forwardAuth` middleware는 nginx `auth_request`와 같은 정책 지점을
+제공한다. 예제는 `/oauth2/auth`를 oauth2-proxy에 위임하고 성공 응답의
+허용된 identity headers만 application request로 복사한다.
+
+중요한 차이:
+
+- ForwardAuth 자체는 OIDC client나 session manager가 아니다. 이 예제에서도
+  oauth2-proxy가 code 교환과 cookie를 담당한다.
+- `trustForwardHeader=false`로 외부 forwarded header를 신뢰하지 않는다.
+- `/oauth2/` router는 callback/start 경로를 oauth2-proxy에 연결해야 한다.
+- nginx의 `error_page 401 -> /oauth2/start`와 같은 로그인 redirect UX는
+  Traefik errors middleware 또는 oauth2-proxy의 forward-auth redirect
+  profile을 추가로 설계해야 한다.
+- Docker socket label discovery 대신 file provider를 사용해 socket 노출을
+  피했다. Kubernetes에서는 Middleware/IngressRoute CRD라는 vendor-specific
+  운영 객체가 추가된다.
+
+이 repository의 실제 AP4 baseline은 학습 가시성이 높은 nginx 조합을
+유지한다. `verify-traefik-forwardauth-config.sh`는 대안 파일을 Traefik
+binary로 로드하고 즉시 발생하는 provider/config 오류가 없는지 확인한다.

e2e/package-lock.json

@@ -0,0 +1,28 @@
+{
+  "name": "keycloak-pattern-e2e",
+  "version": "1.0.0",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "keycloak-pattern-e2e",
+      "version": "1.0.0",
+      "devDependencies": {
+        "playwright-core": "1.62.0"
+      }
+    },
+    "node_modules/playwright-core": {
+      "version": "1.62.0",
+      "resolved": "https://registry.npmjs.org/playwright-core/-/playwright-core-1.62.0.tgz",
+      "integrity": "sha512-nsNRyq0r2zsG8AcRHWknc9QRA5XCueC7gWMrs+Gx2tlZn9hcl8zudfh00lhJPY1DE7NmZ6bDsT9g2yey8mXljA==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "bin": {
+        "playwright-core": "cli.js"
+      },
+      "engines": {
+        "node": ">=20"
+      }
+    }
+  }
+}

e2e/package.json

@@ -0,0 +1,13 @@
+{
+  "name": "keycloak-pattern-e2e",
+  "private": true,
+  "version": "1.0.0",
+  "type": "module",
+  "scripts": {
+    "test:pattern4": "node pattern4.mjs",
+    "test:pattern4-google": "node pattern4-google.mjs"
+  },
+  "devDependencies": {
+    "playwright-core": "1.62.0"
+  }
+}

e2e/pattern4-google.mjs

@@ -0,0 +1,99 @@
+import assert from "node:assert/strict";
+import { chromium } from "playwright-core";
+
+const password = process.env.MOCK_GOOGLE_USER_PASSWORD;
+const adminUsername = process.env.KC_BOOTSTRAP_ADMIN_USERNAME;
+const adminPassword = process.env.KC_BOOTSTRAP_ADMIN_PASSWORD;
+assert.ok(password && adminUsername && adminPassword);
+
+async function verifyBrokeredEmail() {
+  const tokenResponse = await fetch(
+    "http://localhost:8080/realms/master/protocol/openid-connect/token",
+    {
+      method: "POST",
+      body: new URLSearchParams({
+        client_id: "admin-cli",
+        grant_type: "password",
+        username: adminUsername,
+        password: adminPassword,
+      }),
+    },
+  );
+  assert.equal(tokenResponse.status, 200);
+  const token = (await tokenResponse.json()).access_token;
+  const headers = { Authorization: `Bearer ${token}` };
+  const usersResponse = await fetch(
+    "http://localhost:8080/admin/realms/keycloak-patterns/users"
+      + "?email=broker-new-user%40example.test&exact=true",
+    { headers },
+  );
+  assert.equal(usersResponse.status, 200);
+  const users = await usersResponse.json();
+  assert.equal(users.length, 1);
+  const userResponse = await fetch(
+    `http://localhost:8080/admin/realms/keycloak-patterns/users/${users[0].id}`,
+    { headers },
+  );
+  const user = await userResponse.json();
+  assert.equal(user.emailVerified, false);
+  const updateResponse = await fetch(
+    `http://localhost:8080/admin/realms/keycloak-patterns/users/${user.id}`,
+    {
+      method: "PUT",
+      headers: { ...headers, "Content-Type": "application/json" },
+      body: JSON.stringify({ ...user, emailVerified: true }),
+    },
+  );
+  assert.equal(updateResponse.status, 204);
+}
+
+const browser = await chromium.launch({
+  executablePath: process.env.CHROME_BIN ?? "/usr/bin/google-chrome",
+  headless: true,
+  args: ["--no-sandbox"],
+});
+
+try {
+  const context = await browser.newContext();
+  const page = await context.newPage();
+  const browserRequests = [];
+  page.on("request", (request) => browserRequests.push(request.url()));
+
+  await page.goto("http://localhost:8088/");
+  await page.waitForURL(/localhost:8080/u);
+  await page.locator('a[href*="/broker/mock-google/login"]').click();
+  await page.waitForURL(/\/realms\/mock-google\//u);
+  await page.locator("#username").fill("mock-new-user");
+  await page.locator("#password").fill(password);
+  await page.locator("#kc-login").click();
+  await page.waitForURL(/\/oauth2\/callback/u);
+  assert.match(await page.locator("body").innerText(), /Internal Server Error/u);
+
+  await verifyBrokeredEmail();
+  await page.goto(
+    "http://localhost:8088/oauth2/start"
+      + "?rd=http%3A%2F%2Flocalhost%3A8088%2F",
+  );
+  await page.waitForURL("http://localhost:8088/");
+
+  const identity = JSON.parse(await page.locator("body").innerText());
+  assert.equal(identity.pattern, "AP4-edge-forward-auth");
+  assert.match(identity.user, /^[0-9a-f-]{36}$/u);
+  assert.equal(identity.email, "broker-new-user@example.test");
+  assert.equal(
+    browserRequests.some((url) =>
+      url.includes("/protocol/openid-connect/token"),
+    ),
+    false,
+  );
+
+  const session = (await context.cookies()).find(
+    (cookie) => cookie.name === "AP4_SESSION",
+  );
+  assert.ok(session?.httpOnly);
+  console.log(
+    "AP4 Google federation verified: unverified email rejected, verified identity -> edge session -> trusted headers",
+  );
+} finally {
+  await browser.close();
+}

e2e/pattern4.mjs

@@ -0,0 +1,138 @@
+import assert from "node:assert/strict";
+import { chromium } from "playwright-core";
+
+const password = process.env.E2E_PASSWORD;
+assert.ok(password, "E2E_PASSWORD must be set");
+
+const edgeBaseUrl = "http://localhost:8088";
+const edgeEntryUrl = `${edgeBaseUrl}/`;
+
+async function completeKeycloakLogin(page) {
+  for (let attempt = 1; attempt <= 2; attempt += 1) {
+    await page.locator("#username").fill(
+      process.env.E2E_USERNAME ?? "regular-user",
+    );
+    await page.locator("#password").fill(password);
+    await page.locator("#kc-login").click();
+    await page.waitForLoadState("domcontentloaded");
+
+    if (page.url() === edgeEntryUrl) {
+      return;
+    }
+    if (attempt === 1) {
+      await page.goto(`${edgeBaseUrl}/oauth2/start?rd=${encodeURIComponent(edgeEntryUrl)}`);
+      await page.waitForURL(/localhost:8080/u);
+    }
+  }
+  throw new Error(`Keycloak login did not return to AP4: ${page.url()}`);
+}
+
+const browser = await chromium.launch({
+  executablePath: process.env.CHROME_BIN ?? "/usr/bin/google-chrome",
+  headless: true,
+  args: ["--no-sandbox"],
+});
+
+try {
+  const context = await browser.newContext();
+  const page = await context.newPage();
+  const browserRequests = [];
+  page.on("request", (request) =>
+    browserRequests.push({ method: request.method(), url: request.url() }),
+  );
+
+  const edgeResponsePromise = page.waitForResponse(
+    (response) =>
+      response.url() === edgeEntryUrl &&
+      response.status() === 302,
+  );
+  const authorizationRequestPromise = page.waitForRequest((request) =>
+    request.url().includes(
+      "/protocol/openid-connect/auth?approval_prompt=",
+    ),
+  );
+  await page.goto(edgeEntryUrl);
+  const unauthenticatedEdgeResponse = await edgeResponsePromise;
+  assert.equal(unauthenticatedEdgeResponse.status(), 302);
+
+  const authorizationRequest = await authorizationRequestPromise;
+  const authorizationUrl = new URL(authorizationRequest.url());
+  assert.equal(authorizationUrl.searchParams.get("client_id"), "edge-proxy");
+  assert.equal(authorizationUrl.searchParams.get("code_challenge_method"), "S256");
+  assert.ok(authorizationUrl.searchParams.get("code_challenge"));
+
+  await page.waitForURL(/localhost:8080/u);
+  await completeKeycloakLogin(page);
+  const edgeIdentity = JSON.parse(await page.locator("body").innerText());
+  assert.equal(edgeIdentity.pattern, "AP4-edge-forward-auth");
+  assert.ok(edgeIdentity.user);
+  assert.equal(edgeIdentity.identityHeader, "X-Auth-Request-User");
+
+  const callbackRequest = browserRequests.find(({ url }) =>
+    url.startsWith(`${edgeBaseUrl}/oauth2/callback?`),
+  );
+  assert.ok(callbackRequest);
+  assert.equal(callbackRequest.method, "GET");
+  assert.equal(
+    browserRequests.some(({ url }) =>
+      url.includes("/protocol/openid-connect/token"),
+    ),
+    false,
+    "the confidential token exchange must be server-to-server",
+  );
+
+  const cookies = await context.cookies(edgeEntryUrl);
+  const sessionCookie = cookies.find((cookie) => cookie.name === "AP4_SESSION");
+  assert.ok(sessionCookie);
+  assert.equal(sessionCookie.httpOnly, true);
+  assert.equal(sessionCookie.sameSite, "Lax");
+  assert.equal(sessionCookie.secure, false);
+
+  const storage = await page.evaluate(() => ({
+    localStorage: Object.values(localStorage),
+    sessionStorage: Object.values(sessionStorage),
+    readableCookies: document.cookie,
+  }));
+  assert.deepEqual(storage.localStorage, []);
+  assert.deepEqual(storage.sessionStorage, []);
+  assert.equal(storage.readableCookies.includes("AP4_SESSION"), false);
+
+  const spoofAttempt = await page.evaluate(async () => {
+    const response = await fetch("/", {
+      headers: {
+        "X-Auth-Request-User": "spoofed-admin",
+        "X-Auth-Request-Email": "spoofed-admin@example.test",
+        "X-Internal-Auth-Token": "attacker-controlled-token",
+      },
+    });
+    return { status: response.status, body: await response.json() };
+  });
+  assert.equal(spoofAttempt.status, 200);
+  assert.equal(spoofAttempt.body.user, edgeIdentity.user);
+  assert.notEqual(spoofAttempt.body.user, "spoofed-admin");
+
+  const externalAuthSubrequest = await fetch(`${edgeBaseUrl}/oauth2/auth`);
+  assert.equal(externalAuthSubrequest.status, 404);
+
+  const apiResponse = await fetch(`${edgeBaseUrl}/api/edge`, {
+    redirect: "manual",
+  });
+  assert.equal(apiResponse.status, 401);
+  assert.equal(apiResponse.headers.get("location"), null);
+
+  await assert.rejects(
+    fetch("http://localhost:4180/ping"),
+    "oauth2-proxy must not be published on the host",
+  );
+
+  await assert.rejects(
+    fetch("http://localhost:8081/edge/me"),
+    "backend must not be published on the host",
+  );
+
+  console.log(
+    "pattern4 hardened edge verified: auth_request, no backend publish, spoofed headers overwritten",
+  );
+} finally {
+  await browser.close();
+}

frontend/Dockerfile

@@ -1,4 +1,4 @@
 FROM nginx:1.29-alpine
 
-COPY nginx.conf /etc/nginx/conf.d/default.conf
+COPY default.conf.template /etc/nginx/templates/default.conf.template
 COPY index.html /usr/share/nginx/html/index.html

frontend/default.conf.template

@@ -0,0 +1,75 @@
+server {
+    listen 80;
+    server_name _;
+
+    large_client_header_buffers 4 16k;
+
+    location = /health {
+        access_log off;
+        default_type text/plain;
+        return 200 "ok\n";
+    }
+
+    location = /oauth2/auth {
+        internal;
+        proxy_pass http://oauth2-proxy:4180;
+        proxy_pass_request_body off;
+        proxy_set_header Content-Length "";
+        proxy_set_header X-Original-URL $scheme://$http_host$request_uri;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Host $http_host;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_set_header X-Forwarded-Uri $request_uri;
+    }
+
+    location /oauth2/ {
+        proxy_pass http://oauth2-proxy:4180;
+        proxy_http_version 1.1;
+        proxy_set_header Host $http_host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Host $http_host;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_set_header X-Auth-Request-Redirect $scheme://$http_host$request_uri;
+    }
+
+    location = /api/edge {
+        auth_request /oauth2/auth;
+        error_page 401 = @api_unauthorized;
+
+        auth_request_set $auth_user $upstream_http_x_auth_request_user;
+        auth_request_set $auth_email $upstream_http_x_auth_request_email;
+        auth_request_set $auth_cookie $upstream_http_set_cookie;
+        add_header Set-Cookie $auth_cookie always;
+
+        proxy_pass http://app:8081/edge/me;
+        proxy_set_header X-Auth-Request-User $auth_user;
+        proxy_set_header X-Auth-Request-Email $auth_email;
+        proxy_set_header X-Internal-Auth-Token "${INTERNAL_AUTH_TOKEN}";
+    }
+
+    location / {
+        auth_request /oauth2/auth;
+        error_page 401 = @oauth2_signin;
+
+        auth_request_set $auth_user $upstream_http_x_auth_request_user;
+        auth_request_set $auth_email $upstream_http_x_auth_request_email;
+        auth_request_set $auth_cookie $upstream_http_set_cookie;
+        add_header Set-Cookie $auth_cookie always;
+
+        proxy_pass http://app:8081/edge/me;
+        proxy_set_header X-Auth-Request-User $auth_user;
+        proxy_set_header X-Auth-Request-Email $auth_email;
+        proxy_set_header X-Internal-Auth-Token "${INTERNAL_AUTH_TOKEN}";
+    }
+
+    location @oauth2_signin {
+        return 302 $scheme://$http_host/oauth2/start?rd=$scheme://$http_host$request_uri;
+    }
+
+    location @api_unauthorized {
+        default_type application/json;
+        return 401 '{"error":"authentication required"}';
+    }
+}

frontend/nginx.conf

@@ -1,26 +0,0 @@
-server {
-    listen 80;
-    server_name _;
-
-    root /usr/share/nginx/html;
-    index index.html;
-
-    location = /health {
-        access_log off;
-        default_type text/plain;
-        return 200 "ok\n";
-    }
-
-    location /api/ {
-        proxy_pass http://app:8081;
-        proxy_http_version 1.1;
-        proxy_set_header Host $host;
-        proxy_set_header X-Real-IP $remote_addr;
-        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
-        proxy_set_header X-Forwarded-Proto $scheme;
-    }
-
-    location / {
-        try_files $uri $uri/ /index.html;
-    }
-}

keycloak/import/keycloak-patterns-realm.json

@@ -120,10 +120,11 @@
       "serviceAccountsEnabled": false,
       "frontchannelLogout": true,
       "redirectUris": [
-        "http://localhost:4180/oauth2/callback"
+        "http://localhost:8088/oauth2/callback"
       ],
       "webOrigins": [],
       "attributes": {
+        "pkce.code.challenge.method": "S256",
         "post.logout.redirect.uris": "http://localhost:8088/*"
       }
     }

scripts/verify-edge-google-federation.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env sh
+set -eu
+
+set -a
+. ./.env
+set +a
+
+docker compose down --volumes --remove-orphans
+docker compose up --build -d --wait
+./scripts/set-first-broker-login-mode.sh secure
+npm --prefix e2e ci
+MOCK_GOOGLE_USER_PASSWORD="$MOCK_GOOGLE_USER_PASSWORD" \
+KC_BOOTSTRAP_ADMIN_USERNAME="$KC_BOOTSTRAP_ADMIN_USERNAME" \
+KC_BOOTSTRAP_ADMIN_PASSWORD="$KC_BOOTSTRAP_ADMIN_PASSWORD" \
+  npm --prefix e2e run test:pattern4-google

scripts/verify-edge-no-google-profile.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env sh
+set -eu
+
+rendered="$(docker compose config --format json)"
+printf '%s\n' "$rendered" | jq -e '
+  (.services["oauth2-proxy"].command | index("--provider=keycloak-oidc") != null)
+  and
+  (.services["oauth2-proxy"].command | index("--code-challenge-method=S256") != null)
+  and
+  (.services.app.ports == null)
+  and
+  (.services["oauth2-proxy"].ports == null)
+' >/dev/null
+
+rg -Fq 'auth_request /oauth2/auth;' frontend/default.conf.template
+rg -Fq 'proxy_set_header X-Auth-Request-User $auth_user;' \
+  frontend/default.conf.template
+echo "AP4 local-identity edge profile verified"

scripts/verify-pattern4.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env sh
+set -eu
+
+if [ ! -f .env ]; then
+  echo "missing .env; copy .env.example and set development values" >&2
+  exit 1
+fi
+
+set -a
+. ./.env
+set +a
+
+docker compose down --volumes --remove-orphans
+docker compose up --build -d --wait
+
+docker compose exec -T nginx nginx -V 2>&1 |
+  grep -q -- '--with-http_auth_request_module'
+docker compose exec -T nginx nginx -T 2>&1 |
+  grep -q 'proxy_pass_request_body off'
+
+app_container_id="$(docker compose ps -q app)"
+published_app_port="$(docker inspect "$app_container_id" \
+  --format '{{with (index .NetworkSettings.Ports "8081/tcp")}}{{json .}}{{end}}')"
+if [ -n "$published_app_port" ]; then
+  echo "backend port 8081 must not be published on the host" >&2
+  exit 1
+fi
+
+if docker compose exec -T nginx wget -q -O /dev/null \
+  --header 'X-Auth-Request-User: spoofed-admin' \
+  http://app:8081/edge/me 2>/dev/null; then
+  echo "backend accepted a forged identity without the internal token" >&2
+  exit 1
+fi
+
+npm --prefix e2e ci
+E2E_USERNAME=regular-user \
+E2E_PASSWORD="$REGULAR_USER_PASSWORD" \
+  npm --prefix e2e run test:pattern4
+
+echo "AP4 hardened Nginx auth_request edge flow verified"

scripts/verify-traefik-forwardauth-config.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env sh
+set -eu
+
+config_dir="$PWD/deploy/traefik"
+output_file="$(mktemp)"
+cleanup() {
+  rm -f "$output_file"
+}
+trap cleanup EXIT
+
+status=0
+timeout 4 docker run --rm \
+  -v "$config_dir:/etc/traefik:ro" \
+  traefik:v3.5.3 \
+  --configFile=/etc/traefik/traefik.yml >"$output_file" 2>&1 || status=$?
+
+if [ "$status" -ne 0 ] && [ "$status" -ne 124 ]; then
+  cat "$output_file" >&2
+  exit "$status"
+fi
+if rg -qi 'error|failed' "$output_file"; then
+  cat "$output_file" >&2
+  exit 1
+fi
+
+grep -q 'trustForwardHeader: false' deploy/traefik/dynamic.yml
+grep -q 'X-Auth-Request-User' deploy/traefik/dynamic.yml
+echo "Traefik file provider and ForwardAuth configuration verified"