feat(ap2): add confidential token mediator

.env.example

@@ -10,7 +10,6 @@ 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
 ADMIN_USER_PASSWORD=change-me-admin-user-password
 REGULAR_USER_PASSWORD=change-me-regular-user-password
 

.gitignore

@@ -4,6 +4,7 @@
 *.iml
 
 backend/target/
+token-mediator/target/
 **/node_modules/
 frontend/dist/
 build/

README.md

@@ -97,18 +97,15 @@ 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
+## AP2: Token-Mediating Backend
 
-`develop-keycloak-pattern4`는 oauth2-proxy와 Nginx `auth_request`가
-인증을 edge에서 강제하는 패턴입니다.
+`develop-keycloak-pattern2`의 Spring confidential client는
+`http://localhost:8082`에서 실행됩니다. 브라우저는 로그인 redirect와
+HttpOnly `AP2_SESSION`만 사용하고, authorization code 교환과
+access/refresh token 보관은 backend가 담당합니다.
 
 ```bash
-./scripts/verify-pattern4.sh
+./scripts/verify-pattern2.sh
 ```
 
-첫 feature에서는 oauth2-proxy를 `http://localhost:4180`에 직접 노출해
-OIDC redirect/PKCE/callback과 forwarded-user를 분리 확인합니다. 최종
-구성은 `http://localhost:8088` Nginx를 단일 진입점으로 사용합니다.
-자세한 내용은
-[`docs/ap4-edge-forward-auth.md`](docs/ap4-edge-forward-auth.md)를
-참고하세요.
+`/token/boundary`는 실제 token 값을 반환하지 않고 서버 저장 여부만 보여줍니다.

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

@@ -1,47 +0,0 @@
-package com.example.keycloakpattern;
-
-import java.util.LinkedHashMap;
-import java.util.Map;
-
-import jakarta.servlet.http.HttpServletRequest;
-
-import org.springframework.http.ResponseEntity;
-import org.springframework.web.bind.annotation.GetMapping;
-import org.springframework.web.bind.annotation.RestController;
-
-@RestController
-public class EdgeIdentityController {
-
-    @GetMapping("/edge/me")
-    ResponseEntity<Map<String, Object>> currentUser(HttpServletRequest request) {
-        String authRequestUser = request.getHeader("X-Auth-Request-User");
-        String forwardedUser = request.getHeader("X-Forwarded-User");
-        String user = hasText(authRequestUser) ? authRequestUser : forwardedUser;
-        if (!hasText(user)) {
-            return ResponseEntity.status(401).body(Map.of(
-                "error",
-                "trusted edge identity header is required"
-            ));
-        }
-
-        Map<String, Object> response = new LinkedHashMap<>();
-        response.put("pattern", "AP4-edge-forward-auth");
-        response.put("user", user);
-        response.put("email", firstNonBlank(
-            request.getHeader("X-Auth-Request-Email"),
-            request.getHeader("X-Forwarded-Email")
-        ));
-        response.put("identityHeader", hasText(authRequestUser)
-            ? "X-Auth-Request-User"
-            : "X-Forwarded-User");
-        return ResponseEntity.ok(response);
-    }
-
-    private static String firstNonBlank(String first, String second) {
-        return hasText(first) ? first : second;
-    }
-
-    private static boolean hasText(String value) {
-        return value != null && !value.isBlank();
-    }
-}

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

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

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

@@ -40,20 +40,4 @@ class ApiSecurityTest {
             .andExpect(jsonPath("$.subject").value("test-subject"))
             .andExpect(jsonPath("$.username").value("regular-user"));
     }
-
-    @Test
-    void edgeEndpointRejectsMissingIdentityHeader() throws Exception {
-        mockMvc.perform(get("/edge/me"))
-            .andExpect(status().isUnauthorized());
-    }
-
-    @Test
-    void edgeEndpointCurrentlyTrustsForwardedUserHeader() throws Exception {
-        mockMvc.perform(get("/edge/me")
-                .header("X-Forwarded-User", "regular-user")
-                .header("X-Forwarded-Email", "regular-user@example.test"))
-            .andExpect(status().isOk())
-            .andExpect(jsonPath("$.user").value("regular-user"))
-            .andExpect(jsonPath("$.identityHeader").value("X-Forwarded-User"));
-    }
 }

docker-compose.yml

@@ -86,52 +86,25 @@ 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:4180/oauth2/callback
-      - --upstream=http://app:8081
-      - --email-domain=*
-      - --scope=openid profile email
-      - --code-challenge-method=S256
-      - --cookie-name=AP4_SESSION
-      - --cookie-secure=false
-      - --cookie-samesite=lax
-      - --cookie-expire=1h
-      - --skip-provider-button=true
-      - --set-xauthrequest=true
-      - --pass-user-headers=true
-      - --whitelist-domain=localhost:4180
-      - --whitelist-domain=localhost:8080
+  token-mediator:
+    build:
+      context: ./token-mediator
     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}
+      SERVER_PORT: "8082"
+      KEYCLOAK_CLIENT_SECRET: ${TOKEN_MEDIATING_CLIENT_SECRET:?set TOKEN_MEDIATING_CLIENT_SECRET in .env}
     ports:
-      - "127.0.0.1:4180:4180"
+      - "127.0.0.1:8082:8082"
     depends_on:
       keycloak:
         condition: service_healthy
-      app:
-        condition: service_healthy
     healthcheck:
       test:
-        - CMD
-        - /bin/oauth2-proxy
-        - --version
+        - CMD-SHELL
+        - wget -q -O - http://127.0.0.1:8082/actuator/health | grep -q '"status":"UP"'
       interval: 10s
       timeout: 5s
-      retries: 3
-      start_period: 5s
+      retries: 12
+      start_period: 20s
     networks:
       - keycloak-net
     restart: unless-stopped

docs/ap4-edge-forward-auth.md

@@ -1,31 +0,0 @@
-# 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.

e2e/package.json

@@ -4,7 +4,7 @@
   "version": "1.0.0",
   "type": "module",
   "scripts": {
-    "test:pattern4": "node pattern4.mjs"
+    "test:pattern2": "node pattern2.mjs"
   },
   "devDependencies": {
     "playwright-core": "1.62.0"

e2e/pattern2.mjs

@@ -0,0 +1,57 @@
+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 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();
+
+  await page.goto("http://localhost:8082");
+  await page.locator("#login").click();
+  await page.waitForURL(/localhost:8080/u);
+  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.waitForURL("http://localhost:8082/");
+
+  const boundaryResponsePromise = page.waitForResponse((response) =>
+    response.url().endsWith("/token/boundary"),
+  );
+  await page.locator("#inspect").click();
+  const boundaryResponse = await boundaryResponsePromise;
+  assert.equal(boundaryResponse.status(), 200);
+  const boundary = await boundaryResponse.json();
+
+  assert.equal(boundary.accessTokenStored, true);
+  assert.equal(boundary.refreshTokenStored, true);
+  assert.equal(boundary.browserReceivesRefreshToken, false);
+  assert.equal(JSON.stringify(boundary).includes("refresh_token"), false);
+
+  const cookies = await context.cookies("http://localhost:8082/");
+  const sessionCookie = cookies.find((cookie) => cookie.name === "AP2_SESSION");
+  assert.ok(sessionCookie);
+  assert.equal(sessionCookie.httpOnly, true);
+  assert.equal(sessionCookie.sameSite, "Lax");
+
+  const storage = await page.evaluate(() => ({
+    localStorage: Object.values(localStorage),
+    sessionStorage: Object.values(sessionStorage),
+  }));
+  assert.equal(JSON.stringify(storage).includes("refresh_token"), false);
+
+  console.log(
+    "pattern2 confidential client verified: server code exchange, server access/refresh custody, HttpOnly session",
+  );
+} finally {
+  await browser.close();
+}

e2e/pattern4.mjs

@@ -1,111 +0,0 @@
-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");
-
-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() === "http://localhost:4180/edge/me") {
-      return;
-    }
-    if (attempt === 1) {
-      await page.goto("http://localhost:4180/oauth2/start?rd=%2Fedge%2Fme");
-      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() === "http://localhost:4180/edge/me" &&
-      response.status() === 302,
-  );
-  const authorizationRequestPromise = page.waitForRequest((request) =>
-    request.url().includes(
-      "/protocol/openid-connect/auth?approval_prompt=",
-    ),
-  );
-  await page.goto("http://localhost:4180/edge/me");
-  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-Forwarded-User");
-
-  const callbackRequest = browserRequests.find(({ url }) =>
-    url.startsWith("http://localhost:4180/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("http://localhost:4180/");
-  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 missingHeader = await fetch("http://localhost:8081/edge/me");
-  assert.equal(missingHeader.status, 401);
-  const directSpoof = await fetch("http://localhost:8081/edge/me", {
-    headers: { "X-Forwarded-User": "spoofed-admin" },
-  });
-  assert.equal(directSpoof.status, 200);
-  const spoofedIdentity = await directSpoof.json();
-  assert.equal(spoofedIdentity.user, "spoofed-admin");
-
-  console.log(
-    "pattern4 oauth2-proxy verified: redirect, PKCE login, forwarded-user 200, direct spoof precondition",
-  );
-} finally {
-  await browser.close();
-}

keycloak/import/keycloak-patterns-realm.json

@@ -120,7 +120,6 @@
       ],
       "webOrigins": [],
       "attributes": {
-        "pkce.code.challenge.method": "S256",
         "post.logout.redirect.uris": "http://localhost:8088/*"
       }
     }

scripts/verify-pattern2.sh

@@ -16,6 +16,6 @@ docker compose up --build -d --wait
 npm --prefix e2e ci
 E2E_USERNAME=regular-user \
 E2E_PASSWORD="$REGULAR_USER_PASSWORD" \
-  npm --prefix e2e run test:pattern4
+  npm --prefix e2e run test:pattern2
 
-echo "AP4 oauth2-proxy edge flow verified"
+echo "AP2 confidential client boundary verified"

token-mediator/.dockerignore

@@ -0,0 +1 @@
+target/

token-mediator/Dockerfile

@@ -0,0 +1,17 @@
+FROM maven:3.9.11-eclipse-temurin-21-alpine AS build
+
+WORKDIR /workspace
+COPY pom.xml .
+RUN mvn --batch-mode dependency:go-offline
+COPY src src
+RUN mvn --batch-mode verify
+
+FROM eclipse-temurin:21-jre-alpine
+
+RUN addgroup -S spring && adduser -S spring -G spring
+WORKDIR /app
+COPY --from=build /workspace/target/keycloak-token-mediator.jar app.jar
+USER spring:spring
+
+EXPOSE 8082
+ENTRYPOINT ["java", "-jar", "/app/app.jar"]

token-mediator/pom.xml

@@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>3.5.16</version>
+        <relativePath/>
+    </parent>
+
+    <groupId>com.example</groupId>
+    <artifactId>keycloak-token-mediator</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>keycloak-token-mediator</name>
+
+    <properties>
+        <java.version>21</java.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-actuator</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-oauth2-client</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.security</groupId>
+            <artifactId>spring-security-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>keycloak-token-mediator</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+</project>

token-mediator/src/main/java/com/example/keycloakpattern/mediator/SecurityConfig.java

@@ -0,0 +1,29 @@
+package com.example.keycloakpattern.mediator;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.web.SecurityFilterChain;
+
+@Configuration
+public class SecurityConfig {
+
+    @Bean
+    SecurityFilterChain mediatorSecurity(HttpSecurity http) throws Exception {
+        return http
+            .authorizeHttpRequests(authorize -> authorize
+                .requestMatchers(
+                    "/",
+                    "/index.html",
+                    "/app.js",
+                    "/favicon.ico",
+                    "/actuator/health",
+                    "/actuator/health/**"
+                )
+                .permitAll()
+                .anyRequest()
+                .authenticated())
+            .oauth2Login(oauth2 -> oauth2.defaultSuccessUrl("/", true))
+            .build();
+    }
+}

token-mediator/src/main/java/com/example/keycloakpattern/mediator/TokenBoundaryController.java

@@ -0,0 +1,44 @@
+package com.example.keycloakpattern.mediator;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.springframework.http.CacheControl;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.core.Authentication;
+import org.springframework.security.oauth2.client.OAuth2AuthorizedClient;
+import org.springframework.security.oauth2.client.OAuth2AuthorizedClientService;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class TokenBoundaryController {
+
+    private final OAuth2AuthorizedClientService authorizedClientService;
+
+    public TokenBoundaryController(
+        OAuth2AuthorizedClientService authorizedClientService
+    ) {
+        this.authorizedClientService = authorizedClientService;
+    }
+
+    @GetMapping("/token/boundary")
+    ResponseEntity<Map<String, Object>> tokenBoundary(Authentication authentication) {
+        OAuth2AuthorizedClient client = authorizedClientService.loadAuthorizedClient(
+            "keycloak",
+            authentication.getName()
+        );
+
+        Map<String, Object> response = new LinkedHashMap<>();
+        response.put("pattern", "AP2-token-mediating-backend");
+        response.put("principal", authentication.getName());
+        response.put("accessTokenStored", client != null && client.getAccessToken() != null);
+        response.put("refreshTokenStored", client != null && client.getRefreshToken() != null);
+        response.put("browserReceivesRefreshToken", false);
+
+        return ResponseEntity.ok()
+            .cacheControl(CacheControl.noStore())
+            .header("Pragma", "no-cache")
+            .body(response);
+    }
+}

token-mediator/src/main/java/com/example/keycloakpattern/mediator/TokenMediatorApplication.java

@@ -0,0 +1,12 @@
+package com.example.keycloakpattern.mediator;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class TokenMediatorApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(TokenMediatorApplication.class, args);
+    }
+}

token-mediator/src/main/resources/application.yml

@@ -0,0 +1,44 @@
+server:
+  port: ${SERVER_PORT:8082}
+  servlet:
+    session:
+      cookie:
+        name: AP2_SESSION
+        http-only: true
+        same-site: lax
+
+spring:
+  application:
+    name: keycloak-token-mediator
+  security:
+    oauth2:
+      client:
+        registration:
+          keycloak:
+            provider: keycloak
+            client-id: token-mediating-confidential
+            client-secret: ${KEYCLOAK_CLIENT_SECRET}
+            client-authentication-method: client_secret_basic
+            authorization-grant-type: authorization_code
+            redirect-uri: "{baseUrl}/login/oauth2/code/{registrationId}"
+            scope:
+              - openid
+              - profile
+              - email
+        provider:
+          keycloak:
+            authorization-uri: http://localhost:8080/realms/keycloak-patterns/protocol/openid-connect/auth
+            token-uri: http://keycloak:8080/realms/keycloak-patterns/protocol/openid-connect/token
+            jwk-set-uri: http://keycloak:8080/realms/keycloak-patterns/protocol/openid-connect/certs
+            user-info-uri: http://keycloak:8080/realms/keycloak-patterns/protocol/openid-connect/userinfo
+            user-name-attribute: preferred_username
+
+management:
+  endpoint:
+    health:
+      probes:
+        enabled: true
+  endpoints:
+    web:
+      exposure:
+        include: health,info

token-mediator/src/main/resources/static/app.js

@@ -0,0 +1,20 @@
+const result = document.querySelector("#result");
+
+function render(value) {
+  result.textContent = JSON.stringify(value, null, 2);
+}
+
+document.querySelector("#login").addEventListener("click", () => {
+  window.location.assign("/oauth2/authorization/keycloak");
+});
+
+document.querySelector("#inspect").addEventListener("click", async () => {
+  const response = await fetch("/token/boundary", {
+    headers: { Accept: "application/json" },
+  });
+  if (response.redirected || response.status === 401) {
+    window.location.assign("/oauth2/authorization/keycloak");
+    return;
+  }
+  render(await response.json());
+});

token-mediator/src/main/resources/static/index.html

@@ -0,0 +1,29 @@
+<!doctype html>
+<html lang="ko">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>AP2 · Token-Mediating Backend</title>
+  <style>
+    :root { color-scheme: light dark; font-family: system-ui, sans-serif; }
+    body { max-width: 52rem; margin: 6vh auto; padding: 0 1.5rem; line-height: 1.6; }
+    button { margin-right: 0.5rem; padding: 0.6rem 0.9rem; cursor: pointer; }
+    pre { min-height: 8rem; padding: 1rem; border-radius: 0.4rem;
+      background: color-mix(in srgb, CanvasText 9%, Canvas); white-space: pre-wrap; }
+  </style>
+</head>
+<body>
+  <main>
+    <h1>AP2 · Token-Mediating Backend</h1>
+    <p>
+      confidential backend가 authorization code를 token으로 교환합니다.
+      refresh token은 서버의 <code>OAuth2AuthorizedClientService</code>에만
+      보관됩니다.
+    </p>
+    <button id="login" type="button">Keycloak 로그인</button>
+    <button id="inspect" type="button">서버 token 경계 확인</button>
+    <pre id="result" aria-live="polite"></pre>
+  </main>
+  <script type="module" src="/app.js"></script>
+</body>
+</html>

token-mediator/src/test/java/com/example/keycloakpattern/mediator/TokenBoundaryControllerTest.java

@@ -0,0 +1,50 @@
+package com.example.keycloakpattern.mediator;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+import static org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.oidcLogin;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.header;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.security.oauth2.client.OAuth2AuthorizedClient;
+import org.springframework.security.oauth2.client.OAuth2AuthorizedClientService;
+import org.springframework.security.oauth2.core.OAuth2AccessToken;
+import org.springframework.security.oauth2.core.OAuth2RefreshToken;
+import org.springframework.test.context.bean.override.mockito.MockitoBean;
+import org.springframework.test.web.servlet.MockMvc;
+
+@SpringBootTest(properties = "KEYCLOAK_CLIENT_SECRET=test-only-secret")
+@AutoConfigureMockMvc
+class TokenBoundaryControllerTest {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @MockitoBean
+    private OAuth2AuthorizedClientService authorizedClientService;
+
+    @Test
+    void reportsServerSideTokensWithoutReturningTheirValues() throws Exception {
+        OAuth2AuthorizedClient client = mock(OAuth2AuthorizedClient.class);
+        when(client.getAccessToken()).thenReturn(mock(OAuth2AccessToken.class));
+        when(client.getRefreshToken()).thenReturn(mock(OAuth2RefreshToken.class));
+        when(authorizedClientService.loadAuthorizedClient("keycloak", "test-subject"))
+            .thenReturn(client);
+
+        mockMvc.perform(get("/token/boundary").with(oidcLogin()
+                .idToken(token -> token.subject("test-subject"))))
+            .andExpect(status().isOk())
+            .andExpect(header().string("Cache-Control", "no-store"))
+            .andExpect(jsonPath("$.accessTokenStored").value(true))
+            .andExpect(jsonPath("$.refreshTokenStored").value(true))
+            .andExpect(jsonPath("$.browserReceivesRefreshToken").value(false))
+            .andExpect(jsonPath("$.access_token").doesNotExist())
+            .andExpect(jsonPath("$.refresh_token").doesNotExist());
+    }
+}