Support for OIDC Proof Of Key for Code Exchange (PKCE)

docs/src/main/asciidoc/security-openid-connect-web-authentication.adoc

@@ -592,6 +592,24 @@ public class CustomTokenStateManager implements TokenStateManager {
 }
 ----
 
+=== Proof Of Key for Code Exchange (PKCE)
+
+link:https://datatracker.ietf.org/doc/html/rfc7636[Proof Of Key for Code Exchange] (PKCE) minimizes the risk of the authorization code interception.
+
+While `PKCE` is of primary importance to the public OpenId Connect clients (such as the SPA scripts running in a browser), it can also provide an extra level of protection to Quarkus OIDC `web-app` applications which are confidential OpenId Connect clients capable of securely storing the client secret and using it to exchange the code for the tokens.
+
+If can enable `PKCE` for your OIDC `web-app` endpoint with a `quarkus.oidc.authentication.pkce-required` property and a 32 characters long secret, for example:
+
+[source, properties]
+----
+quarkus.oidc.authentication.pkce-required
+quarkus.oidc.authentication.pkce-secret=eUk1p7UB3nFiXZGUXi0uph1Y9p34YhBU
+----
+
+If you already have a 32 character long client secret then `quarkus.oidc.authentication.pkce-secret` does not have to be set unless you prefer to use a different secret key.
+
+The secret key is required for encrypting a randomly generated `PKCE` `code_verifier` while the user is being redirected with the `code_challenge` query parameter to OpenId Connect Provider to authenticate. The `code_verifier` will be decrypted when the user is redirected back to Quarkus and sent to the token endpoint alongside the `code`, client secret and other parameters to complete the code exchange. The provider will fail the code exchange if a `SHA256` digest of the `code_verifier` does not match the `code_challenge` provided during the authentication request.
+
 === Listening to important authentication events
 
 One can register `@ApplicationScoped` bean which will observe important OIDC authentication events. The listener will be updated when a user has logged in for the first time or re-authenticated, as well as when the session has been refreshed. More events may be reported in the future. For example:

extensions/oidc-common/runtime/src/main/java/io/quarkus/oidc/common/runtime/OidcConstants.java

@@ -49,4 +49,10 @@ public final class OidcConstants {
 
     public static final String EXPIRES_IN = "expires_in";
     public static final String REFRESH_EXPIRES_IN = "refresh_expires_in";
+
+    public static final String PKCE_CODE_VERIFIER = "code_verifier";
+    public static final String PKCE_CODE_CHALLENGE = "code_challenge";
+
+    public static final String PKCE_CODE_CHALLENGE_METHOD = "code_challenge_method";
+    public static final String PKCE_CODE_CHALLENGE_S256 = "S256";
 }

extensions/oidc/runtime/src/main/java/io/quarkus/oidc/OidcTenantConfig.java

@@ -572,6 +572,36 @@ public static class Authentication {
         @ConfigItem(defaultValueDocumentation = "true")
         public Optional<Boolean> idTokenRequired = Optional.empty();
 
+        /**
+         * Requires that a Proof Key for Code Exchange (PKCE) is used.
+         */
+        @ConfigItem(defaultValueDocumentation = "false")
+        public Optional<Boolean> pkceRequired = Optional.empty();
+
+        /**
+         * Secret which will be used to encrypt a Proof Key for Code Exchange (PKCE) code verifier in the code flow state.
+         * This secret must be set if PKCE is required but no client secret is set.
+         * The length of the secret which will be used to encrypt the code verifier must be 32 characters long.
+         */
+        @ConfigItem
+        public Optional<String> pkceSecret = Optional.empty();
+
+        public Optional<Boolean> isPkceRequired() {
+            return pkceRequired;
+        }
+
+        public void setPkceRequired(boolean pkceRequired) {
+            this.pkceRequired = Optional.of(pkceRequired);
+        }
+
+        public Optional<String> getPkceSecret() {
+            return pkceSecret;
+        }
+
+        public void setPkceSecret(String pkceSecret) {
+            this.pkceSecret = Optional.of(pkceSecret);
+        }
+
         public boolean isJavaScriptAutoRedirect() {
             return javaScriptAutoRedirect;
         }

extensions/oidc/runtime/src/main/java/io/quarkus/oidc/runtime/CodeAuthenticationMechanism.java

@@ -4,7 +4,11 @@
 import static io.quarkus.oidc.runtime.OidcIdentityProvider.REFRESH_TOKEN_GRANT_RESPONSE;
 
 import java.net.URI;
+import java.nio.charset.StandardCharsets;
+import java.security.SecureRandom;
 import java.util.ArrayList;
+import java.util.Base64;
+import java.util.Base64.Encoder;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
@@ -33,6 +37,7 @@
 import io.quarkus.security.identity.SecurityIdentity;
 import io.quarkus.vertx.http.runtime.security.ChallengeData;
 import io.smallrye.jwt.build.Jwt;
+import io.smallrye.jwt.build.JwtClaimsBuilder;
 import io.smallrye.jwt.util.KeyUtils;
 import io.smallrye.mutiny.Uni;
 import io.vertx.core.http.Cookie;
@@ -50,6 +55,7 @@ public class CodeAuthenticationMechanism extends AbstractOidcAuthenticationMecha
     static final String COOKIE_DELIM = "|";
     static final Pattern COOKIE_PATTERN = Pattern.compile("\\" + COOKIE_DELIM);
     static final String SESSION_MAX_AGE_PARAM = "session-max-age";
+    static final String STATE_COOKIE_RESTORE_PATH = "restore-path";
     static final Uni<Void> VOID_UNI = Uni.createFrom().voidItem();
     static final Integer MAX_COOKIE_VALUE_LENGTH = 4096;
     static final String NO_OIDC_COOKIES_AVAILABLE = "no_oidc_cookies";
@@ -59,6 +65,7 @@ public class CodeAuthenticationMechanism extends AbstractOidcAuthenticationMecha
 
     private final BlockingTaskRunner<String> createTokenStateRequestContext = new BlockingTaskRunner<String>();
     private final BlockingTaskRunner<AuthorizationCodeTokens> getTokenStateRequestContext = new BlockingTaskRunner<AuthorizationCodeTokens>();
+    private final SecureRandom secureRandom = new SecureRandom();
 
     public Uni<SecurityIdentity> authenticate(RoutingContext context,
             IdentityProviderManager identityProviderManager, OidcTenantConfig oidcTenantConfig) {
@@ -82,8 +89,9 @@ public Uni<SecurityIdentity> apply(TenantConfigContext tenantContext) {
         // if the state cookie is available then try to complete the code flow and start a new session
         if (stateCookie != null) {
             String[] parsedStateCookieValue = COOKIE_PATTERN.split(stateCookie.getValue());
+            OidcUtils.removeCookie(context, oidcTenantConfig, stateCookie.getName());
+
             if (!isStateValid(context, parsedStateCookieValue[0])) {
-                OidcUtils.removeCookie(context, oidcTenantConfig, stateCookie.getName());
                 return Uni.createFrom().failure(new AuthenticationCompletionException());
             }
 
@@ -95,13 +103,12 @@ public Uni<SecurityIdentity> apply(TenantConfigContext tenantContext) {
                         .transformToUni(new Function<TenantConfigContext, Uni<? extends SecurityIdentity>>() {
                             @Override
                             public Uni<SecurityIdentity> apply(TenantConfigContext tenantContext) {
-                                return performCodeFlow(identityProviderManager, context, tenantContext, code, stateCookie,
+                                return performCodeFlow(identityProviderManager, context, tenantContext, code,
                                         parsedStateCookieValue);
                             }
                         });
             } else {
                 LOG.debug("State cookie is present but neither 'code' nor 'error' query parameter is returned");
-                OidcUtils.removeCookie(context, oidcTenantConfig, stateCookie.getName());
                 return Uni.createFrom().failure(new AuthenticationCompletionException());
             }
         }
@@ -275,9 +282,22 @@ && isRedirectFromProvider(context, configContext)) {
                         codeFlowParams.append(AMP).append(OidcConstants.CODE_FLOW_REDIRECT_URI).append(EQ)
                                 .append(OidcCommonUtils.urlEncode(redirectUriParam));
 
+                        // pkce
+                        PkceStateBean pkceStateBean = createPkceStateBean(configContext);
+
                         // state
                         codeFlowParams.append(AMP).append(OidcConstants.CODE_FLOW_STATE).append(EQ)
-                                .append(generateCodeFlowState(context, configContext, redirectPath));
+                                .append(generateCodeFlowState(context, configContext, redirectPath,
+                                        pkceStateBean != null ? pkceStateBean.getCodeVerifier() : null));
+
+                        if (pkceStateBean != null) {
+                            codeFlowParams
+                                    .append(AMP).append(OidcConstants.PKCE_CODE_CHALLENGE).append(EQ)
+                                    .append(pkceStateBean.getCodeChallenge());
+                            codeFlowParams
+                                    .append(AMP).append(OidcConstants.PKCE_CODE_CHALLENGE_METHOD).append(EQ)
+                                    .append(OidcConstants.PKCE_CODE_CHALLENGE_S256);
+                        }
 
                         // extra redirect parameters, see https://openid.net/specs/openid-connect-core-1_0.html#AuthRequests
                         addExtraParamsToUri(codeFlowParams, configContext.oidcConfig.authentication.getExtraParams());
@@ -297,31 +317,58 @@ private boolean isRedirectFromProvider(RoutingContext context, TenantConfigConte
         return referer != null && referer.startsWith(configContext.provider.getMetadata().getAuthorizationUri());
     }
 
+    private PkceStateBean createPkceStateBean(TenantConfigContext configContext) {
+        if (configContext.oidcConfig.authentication.pkceRequired.orElse(false)) {
+            PkceStateBean bean = new PkceStateBean();
+
+            Encoder encoder = Base64.getUrlEncoder().withoutPadding();
+
+            // code verifier
+            byte[] codeVerifierBytes = new byte[32];
+            secureRandom.nextBytes(codeVerifierBytes);
+            String codeVerifier = encoder.encodeToString(codeVerifierBytes);
+            bean.setCodeVerifier(codeVerifier);
+
+            // code challenge
+            try {
+                byte[] codeChallengeBytes = OidcUtils.getSha256Digest(codeVerifier.getBytes(StandardCharsets.US_ASCII));
+                String codeChallenge = encoder.encodeToString(codeChallengeBytes);
+                bean.setCodeChallenge(codeChallenge);
+            } catch (Exception ex) {
+                throw new AuthenticationFailedException(ex);
+            }
+
+            return bean;
+        }
+        return null;
+    }
+
     private Uni<SecurityIdentity> performCodeFlow(IdentityProviderManager identityProviderManager,
-            RoutingContext context, TenantConfigContext configContext, String code, Cookie stateCookie,
-            String[] parsedStateCookieValue) {
+            RoutingContext context, TenantConfigContext configContext, String code, String[] parsedStateCookieValue) {
 
         String userPath = null;
         String userQuery = null;
 
         // This is an original redirect from IDP, check if the original request path and query need to be restored
-        if (parsedStateCookieValue.length == 2) {
-            int userQueryIndex = parsedStateCookieValue[1].indexOf("?");
+        CodeAuthenticationStateBean stateBean = getCodeAuthenticationBean(parsedStateCookieValue, configContext.oidcConfig);
+        if (stateBean != null && stateBean.getRestorePath() != null) {
+            String restorePath = stateBean.getRestorePath();
+            int userQueryIndex = restorePath.indexOf("?");
             if (userQueryIndex >= 0) {
-                userPath = parsedStateCookieValue[1].substring(0, userQueryIndex);
-                if (userQueryIndex + 1 < parsedStateCookieValue[1].length()) {
-                    userQuery = parsedStateCookieValue[1].substring(userQueryIndex + 1);
+                userPath = restorePath.substring(0, userQueryIndex);
+                if (userQueryIndex + 1 < restorePath.length()) {
+                    userQuery = restorePath.substring(userQueryIndex + 1);
                 }
             } else {
-                userPath = parsedStateCookieValue[1];
+                userPath = restorePath;
             }
         }
-        OidcUtils.removeCookie(context, configContext.oidcConfig, stateCookie.getName());
 
         final String finalUserPath = userPath;
         final String finalUserQuery = userQuery;
 
-        Uni<AuthorizationCodeTokens> codeFlowTokensUni = getCodeFlowTokensUni(context, configContext, code);
+        Uni<AuthorizationCodeTokens> codeFlowTokensUni = getCodeFlowTokensUni(context, configContext, code,
+                stateBean != null ? stateBean.getCodeVerifier() : null);
 
         return codeFlowTokensUni
                 .onItemOrFailure()
@@ -402,9 +449,34 @@ public Throwable apply(Throwable tInner) {
 
     }
 
+    private CodeAuthenticationStateBean getCodeAuthenticationBean(String[] parsedStateCookieValue,
+            OidcTenantConfig oidcConfig) {
+        if (parsedStateCookieValue.length == 2) {
+            CodeAuthenticationStateBean bean = new CodeAuthenticationStateBean();
+            if (!oidcConfig.authentication.pkceRequired.orElse(false)) {
+                bean.setRestorePath(parsedStateCookieValue[1]);
+                return bean;
+            }
+
+            String pkceSecret = oidcConfig.authentication.pkceSecret
+                    .orElse(OidcCommonUtils.clientSecret(oidcConfig.credentials));
+            JsonObject json = null;
+            try {
+                json = OidcUtils.decryptJson(parsedStateCookieValue[1], KeyUtils.createSecretKeyFromSecret(pkceSecret));
+            } catch (Exception ex) {
+                LOG.tracef("State cookie value can not be decrypted for the %s tenant", oidcConfig.tenantId.get());
+                throw new AuthenticationFailedException(ex);
+            }
+            bean.setRestorePath(json.getString(STATE_COOKIE_RESTORE_PATH));
+            bean.setCodeVerifier(json.getString(OidcConstants.PKCE_CODE_VERIFIER));
+            return bean;
+        }
+        return null;
+    }
+
     private String generateInternalIdToken(OidcTenantConfig oidcConfig) {
         return Jwt.claims().jws().header(INTERNAL_IDTOKEN_HEADER, true)
-                .sign(KeyUtils.createSecretKeyFromSecret(oidcConfig.credentials.secret.get()));
+                .sign(KeyUtils.createSecretKeyFromSecret(OidcCommonUtils.clientSecret(oidcConfig.credentials)));
     }
 
     private Uni<Void> processSuccessfulAuthentication(RoutingContext context,
@@ -475,28 +547,50 @@ private String getRedirectPath(TenantConfigContext configContext, RoutingContext
     }
 
     private String generateCodeFlowState(RoutingContext context, TenantConfigContext configContext,
-            String redirectPath) {
+            String redirectPath, String pkceCodeVerifier) {
         String uuid = UUID.randomUUID().toString();
         String cookieValue = uuid;
 
         Authentication auth = configContext.oidcConfig.getAuthentication();
         boolean restorePath = auth.isRestorePathAfterRedirect() || !auth.redirectPath.isPresent();
-        if (restorePath) {
-            String requestQuery = context.request().query();
-            String requestPath = !redirectPath.equals(context.request().path()) || requestQuery != null
-                    ? context.request().path()
-                    : "";
-            if (requestQuery != null) {
-                requestPath += ("?" + requestQuery);
+        if (restorePath || pkceCodeVerifier != null) {
+            CodeAuthenticationStateBean extraStateValue = new CodeAuthenticationStateBean();
+            if (restorePath) {
+                String requestQuery = context.request().query();
+                String requestPath = !redirectPath.equals(context.request().path()) || requestQuery != null
+                        ? context.request().path()
+                        : "";
+                if (requestQuery != null) {
+                    requestPath += ("?" + requestQuery);
+                }
+                if (!requestPath.isEmpty()) {
+                    extraStateValue.setRestorePath(requestPath);
+                }
             }
-            if (!requestPath.isEmpty()) {
-                cookieValue += (COOKIE_DELIM + requestPath);
+            extraStateValue.setCodeVerifier(pkceCodeVerifier);
+            if (!extraStateValue.isEmpty()) {
+                cookieValue += (COOKIE_DELIM + encodeExtraStateValue(extraStateValue, configContext.oidcConfig));
             }
         }
         createCookie(context, configContext.oidcConfig, getStateCookieName(configContext.oidcConfig), cookieValue, 60 * 30);
         return uuid;
     }
 
+    private String encodeExtraStateValue(CodeAuthenticationStateBean extraStateValue, OidcTenantConfig oidcConfig) {
+        if (extraStateValue.getCodeVerifier() != null) {
+            String pkceSecret = oidcConfig.authentication.pkceSecret
+                    .orElse(OidcCommonUtils.clientSecret(oidcConfig.credentials));
+            JwtClaimsBuilder claims = Jwt.claim(OidcConstants.PKCE_CODE_VERIFIER, extraStateValue.getCodeVerifier());
+            if (extraStateValue.getRestorePath() != null) {
+                claims.claim(STATE_COOKIE_RESTORE_PATH, extraStateValue.getRestorePath());
+            }
+            return claims.jwe().encrypt(KeyUtils.createSecretKeyFromSecret(pkceSecret));
+        } else {
+            return extraStateValue.getRestorePath();
+        }
+
+    }
+
     private String generatePostLogoutState(RoutingContext context, TenantConfigContext configContext) {
         OidcUtils.removeCookie(context, configContext.oidcConfig, getPostLogoutCookieName(configContext.oidcConfig));
         return createCookie(context, configContext.oidcConfig, getPostLogoutCookieName(configContext.oidcConfig),
@@ -614,14 +708,14 @@ private Uni<AuthorizationCodeTokens> refreshTokensUni(TenantConfigContext config
     }
 
     private Uni<AuthorizationCodeTokens> getCodeFlowTokensUni(RoutingContext context, TenantConfigContext configContext,
-            String code) {
+            String code, String codeVerifier) {
 
         // 'redirect_uri': typically it must match the 'redirect_uri' query parameter which was used during the code request.
         String redirectPath = getRedirectPath(configContext, context);
         String redirectUriParam = buildUri(context, isForceHttps(configContext), redirectPath);
         LOG.debugf("Token request redirect_uri parameter: %s", redirectUriParam);
 
-        return configContext.provider.getCodeFlowTokens(code, redirectUriParam);
+        return configContext.provider.getCodeFlowTokens(code, redirectUriParam, codeVerifier);
     }
 
     private String buildLogoutRedirectUri(TenantConfigContext configContext, String idToken, RoutingContext context) {

extensions/oidc/runtime/src/main/java/io/quarkus/oidc/runtime/CodeAuthenticationStateBean.java

@@ -0,0 +1,29 @@
+package io.quarkus.oidc.runtime;
+
+public class CodeAuthenticationStateBean {
+
+    private String restorePath;
+
+    private String codeVerifier;
+
+    public String getRestorePath() {
+        return restorePath;
+    }
+
+    public void setRestorePath(String restorePath) {
+        this.restorePath = restorePath;
+    }
+
+    public String getCodeVerifier() {
+        return codeVerifier;
+    }
+
+    public void setCodeVerifier(String codeVerifier) {
+        this.codeVerifier = codeVerifier;
+    }
+
+    public boolean isEmpty() {
+        return this.restorePath == null && this.codeVerifier == null;
+    }
+
+}

extensions/oidc/runtime/src/main/java/io/quarkus/oidc/runtime/OidcProvider.java

@@ -197,8 +197,8 @@ public Uni<UserInfo> getUserInfo(String accessToken) {
         return client.getUserInfo(accessToken);
     }
 
-    public Uni<AuthorizationCodeTokens> getCodeFlowTokens(String code, String redirectUri) {
-        return client.getAuthorizationCodeTokens(code, redirectUri);
+    public Uni<AuthorizationCodeTokens> getCodeFlowTokens(String code, String redirectUri, String codeVerifier) {
+        return client.getAuthorizationCodeTokens(code, redirectUri, codeVerifier);
     }
 
     public Uni<AuthorizationCodeTokens> refreshTokens(String refreshToken) {