diff --git a/src/brpc/authenticator.h b/src/brpc/authenticator.h
index 501e427e7f..e08a3f1424 100644
--- a/src/brpc/authenticator.h
+++ b/src/brpc/authenticator.h
@@ -57,7 +57,7 @@ class AuthContext {
 
 class Authenticator {
 public:
-    virtual ~Authenticator() {}
+    virtual ~Authenticator() = default;
 
     // Implement this method to generate credential information
     // into `auth_str' which will be sent to `VerifyCredential'
@@ -74,6 +74,13 @@ class Authenticator {
                                  const butil::EndPoint& client_addr,
                                  AuthContext* out_ctx) const = 0;
 
+    // Implement this method to unauthorized error text which
+    // will be sent as a part of error text in baidu_std/hulu_pbrpc
+    // protocol or body in http protocol.
+    virtual std::string GetUnauthorizedErrorText() const {
+        return "";
+    }
+
 };
 
 inline std::ostream& operator<<(std::ostream& os, const AuthContext& ctx) {
diff --git a/src/brpc/policy/baidu_rpc_protocol.cpp b/src/brpc/policy/baidu_rpc_protocol.cpp
index 0fb439a82d..504895b185 100644
--- a/src/brpc/policy/baidu_rpc_protocol.cpp
+++ b/src/brpc/policy/baidu_rpc_protocol.cpp
@@ -659,8 +659,8 @@ bool VerifyRpcRequest(const InputMessageBase* msg_base) {
     const Server* server = static_cast<const Server*>(msg->arg());
     Socket* socket = msg->socket();
     
-    RpcMeta meta;
-    if (!ParsePbFromIOBuf(&meta, msg->meta)) {
+    RpcMeta request_meta;
+    if (!ParsePbFromIOBuf(&request_meta, msg->meta)) {
         LOG(WARNING) << "Fail to parse RpcRequestMeta";
         return false;
     }
@@ -668,13 +668,32 @@ bool VerifyRpcRequest(const InputMessageBase* msg_base) {
     if (NULL == auth) {
         // Fast pass (no authentication)
         return true;
-    }    
-    if (auth->VerifyCredential(
-                meta.authentication_data(), socket->remote_side(), 
-                socket->mutable_auth_context()) != 0) {
-        return false;
     }
-    return true;
+    if (auth->VerifyCredential(request_meta.authentication_data(),
+                               socket->remote_side(),
+                               socket->mutable_auth_context()) == 0) {
+        return true;
+    }
+
+    // Send `ERPCAUTH' to client.
+    RpcMeta response_meta;
+    response_meta.set_correlation_id(request_meta.correlation_id());
+    response_meta.mutable_response()->set_error_code(ERPCAUTH);
+    response_meta.mutable_response()->set_error_text("Fail to authenticate");
+    std::string user_error_text = auth->GetUnauthorizedErrorText();
+    if (!user_error_text.empty()) {
+        response_meta.mutable_response()->mutable_error_text()->append(": ");
+        response_meta.mutable_response()->mutable_error_text()->append(user_error_text);
+    }
+    butil::IOBuf res_buf;
+    SerializeRpcHeaderAndMeta(&res_buf, response_meta, 0);
+    Socket::WriteOptions opt;
+    opt.ignore_eovercrowded = true;
+    if (socket->Write(&res_buf, &opt) != 0) {
+        PLOG_IF(WARNING, errno != EPIPE) << "Fail to write into " << *socket;
+    }
+
+    return false;
 }
 
 void ProcessRpcResponse(InputMessageBase* msg_base) {
diff --git a/src/brpc/policy/http_rpc_protocol.cpp b/src/brpc/policy/http_rpc_protocol.cpp
index 52fff2c9cf..37ea8002dd 100644
--- a/src/brpc/policy/http_rpc_protocol.cpp
+++ b/src/brpc/policy/http_rpc_protocol.cpp
@@ -1253,6 +1253,26 @@ ParseResult ParseHttpMessage(butil::IOBuf *source, Socket *socket,
     }
 }
 
+static void SendUnauthorizedResponse(const std::string& user_error_text, Socket* socket) {
+    // Send 403(forbidden) to client.
+    HttpHeader header;
+    header.set_status_code(HTTP_STATUS_FORBIDDEN);
+    butil::IOBuf content;
+    content.append(butil::string_printf("[%d]", ERPCAUTH));
+    content.append("Fail to authenticate");
+    if (!user_error_text.empty()) {
+        content.append(": ");
+        content.append(user_error_text);
+    }
+    butil::IOBuf res_buf;
+    MakeRawHttpResponse(&res_buf, &header, &content);
+    Socket::WriteOptions opt;
+    opt.ignore_eovercrowded = true;
+    if (socket->Write(&res_buf, &opt) != 0) {
+        PLOG_IF(WARNING, errno != EPIPE) << "Fail to write into " << *socket;
+    }
+}
+
 bool VerifyHttpRequest(const InputMessageBase* msg) {
     Server* server = (Server*)msg->arg();
     Socket* socket = msg->socket();
@@ -1265,8 +1285,7 @@ bool VerifyHttpRequest(const InputMessageBase* msg) {
     }
     const Server::MethodProperty* mp = FindMethodPropertyByURI(
         http_request->header().uri().path(), server, NULL);
-    if (mp != NULL &&
-        mp->is_builtin_service &&
+    if (mp != NULL && mp->is_builtin_service &&
         mp->service->GetDescriptor() != BadMethodService::descriptor()) {
         // BuiltinService doesn't need authentication
         // TODO: Fix backdoor that sends BuiltinService at first
@@ -1275,16 +1294,22 @@ bool VerifyHttpRequest(const InputMessageBase* msg) {
     }
 
     const std::string *authorization 
-        = http_request->header().GetHeader("Authorization");
+        = http_request->header().GetHeader(common->AUTHORIZATION);
     if (authorization == NULL) {
+        SendUnauthorizedResponse(auth->GetUnauthorizedErrorText(), socket);
         return false;
     }
     butil::EndPoint user_addr;
     if (!GetUserAddressFromHeader(http_request->header(), &user_addr)) {
         user_addr = socket->remote_side();
     }
-    return auth->VerifyCredential(*authorization, user_addr,
-                                  socket->mutable_auth_context()) == 0;
+    if (auth->VerifyCredential(*authorization, user_addr,
+                               socket->mutable_auth_context()) != 0) {
+        SendUnauthorizedResponse(auth->GetUnauthorizedErrorText(), socket);
+        return false;
+    }
+
+    return true;
 }
 
 
diff --git a/src/brpc/policy/hulu_pbrpc_protocol.cpp b/src/brpc/policy/hulu_pbrpc_protocol.cpp
index 2b63189eac..cb10aac35b 100644
--- a/src/brpc/policy/hulu_pbrpc_protocol.cpp
+++ b/src/brpc/policy/hulu_pbrpc_protocol.cpp
@@ -540,8 +540,8 @@ bool VerifyHuluRequest(const InputMessageBase* msg_base) {
     Socket* socket = msg->socket();
     const Server* server = static_cast<const Server*>(msg->arg());
 
-    HuluRpcRequestMeta meta;
-    if (!ParsePbFromIOBuf(&meta, msg->meta)) {
+    HuluRpcRequestMeta request_meta;
+    if (!ParsePbFromIOBuf(&request_meta, msg->meta)) {
         LOG(WARNING) << "Fail to parse HuluRpcRequestMeta";
         return false;
     }
@@ -549,13 +549,32 @@ bool VerifyHuluRequest(const InputMessageBase* msg_base) {
     if (NULL == auth) {
         // Fast pass (no authentication)
         return true;
-    }    
-    if (auth->VerifyCredential(
-                meta.credential_data(), socket->remote_side(), 
-                socket->mutable_auth_context()) != 0) {
-        return false;
     }
-    return true;
+    if (auth->VerifyCredential(request_meta.credential_data(),
+                               socket->remote_side(),
+                               socket->mutable_auth_context()) == 0) {
+        return true;
+    }
+
+    // Send `ERPCAUTH' to client.
+    HuluRpcResponseMeta response_meta;
+    response_meta.set_correlation_id(request_meta.correlation_id());
+    response_meta.set_error_code(ERPCAUTH);
+    std::string user_error_text = auth->GetUnauthorizedErrorText();
+    response_meta.set_error_text("Fail to authenticate");
+    if (!user_error_text.empty()) {
+        response_meta.mutable_error_text()->append(": ");
+        response_meta.mutable_error_text()->append(user_error_text);
+    }
+    butil::IOBuf res_buf;
+    SerializeHuluHeaderAndMeta(&res_buf, request_meta, 0);
+    Socket::WriteOptions opt;
+    opt.ignore_eovercrowded = true;
+    if (socket->Write(&res_buf, &opt) != 0) {
+        PLOG_IF(WARNING, errno != EPIPE) << "Fail to write into " << *socket;
+    }
+
+    return false;
 }
 
 void ProcessHuluResponse(InputMessageBase* msg_base) {
diff --git a/test/brpc_server_unittest.cpp b/test/brpc_server_unittest.cpp
index 5f06887a52..b2e0bbaa48 100644
--- a/test/brpc_server_unittest.cpp
+++ b/test/brpc_server_unittest.cpp
@@ -80,18 +80,25 @@ void* RunClosure(void* arg) {
     return NULL;
 }
 
+bool g_verify_success = true;
+const std::string g_unauthorized_error_text = "unauthorized";
+
 class MyAuthenticator : public brpc::Authenticator {
 public:
-    MyAuthenticator() {}
-    virtual ~MyAuthenticator() {}
-    int GenerateCredential(std::string*) const {
+    MyAuthenticator() = default;
+    ~MyAuthenticator() override = default;
+    int GenerateCredential(std::string*) const override {
         return 0;
     }
 
     int VerifyCredential(const std::string&,
                          const butil::EndPoint&,
-                         brpc::AuthContext*) const {
-        return 0;
+                         brpc::AuthContext*) const override {
+        return g_verify_success ? 0 : -1;
+    }
+
+    std::string GetUnauthorizedErrorText() const override {
+        return g_unauthorized_error_text;
     }
 };
 
@@ -1828,4 +1835,73 @@ TEST_F(ServerTest, rpc_pb_message_factory) {
     ASSERT_EQ(0, server.Join());
 }
 
+void TestBaiduStdAuth(const butil::EndPoint& ep,
+    brpc::Controller& cntl,
+    int error_code, bool failed) {
+    brpc::Channel chan;
+    brpc::ChannelOptions copt;
+    copt.max_retry = 0;
+    copt.protocol = "baidu_std";
+    ASSERT_EQ(0, chan.Init(ep, &copt));
+
+    test::EchoRequest req;
+    test::EchoResponse res;
+    req.set_message(EXP_REQUEST);
+    test::EchoService_Stub stub(&chan);
+    stub.Echo(&cntl, &req, &res, NULL);
+    ASSERT_EQ(cntl.Failed(), failed) << cntl.ErrorText();
+    ASSERT_EQ(cntl.ErrorCode(), error_code);
+}
+
+void TestHttpAuth(const butil::EndPoint& ep,
+                  brpc::Controller& cntl,
+                  int status_code, bool failed) {
+    brpc::Channel chan;
+    brpc::ChannelOptions copt;
+    copt.max_retry = 0;
+    copt.protocol = "http";
+    ASSERT_EQ(0, chan.Init(ep, &copt));
+
+    cntl.http_request().uri() = "/EchoService/Echo";
+    cntl.request_attachment().append(R"({"message": "hello"})");
+    cntl.http_request().set_method(brpc::HTTP_METHOD_POST);
+    test::EchoService_Stub stub(&chan);
+    chan.CallMethod(NULL, &cntl, NULL, NULL, NULL);
+    ASSERT_EQ(cntl.Failed(), failed) << cntl.ErrorText();
+    ASSERT_EQ(cntl.http_response().status_code(), status_code);
+}
+
+TEST_F(ServerTest, auth) {
+    butil::EndPoint ep;
+    ASSERT_EQ(0, str2endpoint("127.0.0.1:8613", &ep));
+    brpc::Server server;
+    EchoServiceImpl service;
+    ASSERT_EQ(0, server.AddService(&service, brpc::SERVER_DOESNT_OWN_SERVICE));
+    MyAuthenticator auth;
+    brpc::ServerOptions opt;
+    opt.auth = &auth;
+    ASSERT_EQ(0, server.Start(ep, &opt));
+
+    brpc::Controller cntl;
+    TestBaiduStdAuth(ep, cntl, 0, false);
+
+    g_verify_success = false;
+    cntl.Reset();
+    TestBaiduStdAuth(ep, cntl, brpc::ERPCAUTH, true);
+    ASSERT_NE(cntl.ErrorText().find(g_unauthorized_error_text), std::string::npos);
+
+    cntl.Reset();
+    TestHttpAuth(ep, cntl, brpc::HTTP_STATUS_FORBIDDEN, true);
+    ASSERT_NE(cntl.response_attachment().to_string().find(g_unauthorized_error_text),
+              std::string::npos);
+
+    g_verify_success = true;
+    cntl.Reset();
+    cntl.http_request().SetHeader("Authorization", "123");
+    TestHttpAuth(ep, cntl, brpc::HTTP_STATUS_OK, false);
+
+    ASSERT_EQ(0, server.Stop(0));
+    ASSERT_EQ(0, server.Join());
+}
+
 } //namespace