security: Do not let grpc reload ssh cert if not changed (#9068) (#9069)

ref #8535

.github/licenserc.yml

@@ -42,5 +42,6 @@ header:
     - '.devcontainer/'
     - '**/OWNERS'
     - 'OWNERS_ALIASES'
+    - 'dbms/src/Common/tests/tls/'
 
   comment: on-failure

dbms/src/Common/TiFlashSecurity.h

@@ -177,11 +177,13 @@ class TiFlashSecurityConfig : public ConfigObject
         return allowed_common_names.count(cert.commonName()) > 0;
     }
 
-    grpc::SslCredentialsOptions readAndCacheSslCredentialOptions()
+    std::optional<grpc::SslCredentialsOptions> readAndCacheSslCredentialOptions()
     {
         std::unique_lock lock(mu);
+        // if ssl_cerd_options_cached = true, it means the same options has already been returned to grpc-core
+        // don't need to return it again if ssl cert is not actually changed
         if (ssl_cerd_options_cached)
-            return options;
+            return {};
         options.pem_root_certs = readFile(ca_path);
         options.pem_cert_chain = readFile(cert_path);
         options.pem_private_key = readFile(key_path);

dbms/src/Common/tests/gtest_tiflash_security.cpp

@@ -13,6 +13,8 @@
 // limitations under the License.
 
 #include <Common/TiFlashSecurity.h>
+#include <Poco/File.h>
+#include <Poco/FileStream.h>
 #include <TestUtils/ConfigTestUtils.h>
 #include <gtest/gtest.h>
 
@@ -188,5 +190,86 @@ redact_info_log=false
     ASSERT_TRUE(tiflash_config_2.allowedCommonNames().empty());
     ASSERT_FALSE(tiflash_config_2.hasTlsConfig());
 }
+
+String createConfigString(String & ca_path, String & cert_path, String & key_path)
+{
+    String ret =
+        R"(
+[security]
+ca_path=")";
+    ret += ca_path;
+    ret += R"("
+cert_path=")";
+    ret += cert_path;
+    ret += R"("
+key_path=")";
+    ret += key_path;
+    ret += R"("
+)";
+    return ret;
+}
+
+TEST(TiFlashSecurityTest, readAndCacheSslCredentialOptions)
+{
+    const auto & test_info = testing::UnitTest::GetInstance()->current_test_info();
+    assert(test_info);
+    String file_name = test_info->file();
+    auto pos = file_name.find_last_of('/');
+    auto file_path = file_name.substr(0, pos);
+    // these certs are copied from https://github.com/grpc/grpc/tree/v1.64.0/src/python/grpcio_tests/tests/unit/credentials
+    auto ca_path = file_path + "/tls/ca.crt";
+    auto cert_path = file_path + "/tls/cert.crt";
+    auto key_path = file_path + "/tls/key.pem";
+    auto test = createConfigString(ca_path, cert_path, key_path);
+    auto config = loadConfigFromString(test);
+    const auto log = Logger::get();
+    TiFlashSecurityConfig tiflash_config(log);
+    tiflash_config.init(*config);
+    // first read will return a valid options
+    auto options = tiflash_config.readAndCacheSslCredentialOptions();
+    ASSERT_TRUE(options.has_value());
+    // not return valid options if cert is not changed
+    auto new_options = tiflash_config.readAndCacheSslCredentialOptions();
+    ASSERT_FALSE(new_options.has_value());
+    ca_path = file_path + "/tls/ca.crt.new";
+    cert_path = file_path + "/tls/cert.crt.new";
+    key_path = file_path + "/tls/key.pem.new";
+    {
+        Poco::FileOutputStream ca_fos(ca_path);
+        ca_fos << options.value().pem_root_certs;
+        Poco::FileOutputStream cert_fos(cert_path);
+        cert_fos << options.value().pem_cert_chain;
+        Poco::FileOutputStream key_fos(key_path);
+        key_fos << options.value().pem_private_key;
+    }
+    test = createConfigString(ca_path, cert_path, key_path);
+    config = loadConfigFromString(test);
+    ASSERT_TRUE(tiflash_config.update(*config));
+    // return a valid options if cert is changed
+    options = tiflash_config.readAndCacheSslCredentialOptions();
+    ASSERT_TRUE(options.has_value());
+    new_options = tiflash_config.readAndCacheSslCredentialOptions();
+    ASSERT_FALSE(new_options.has_value());
+    using namespace std::chrono_literals;
+    std::this_thread::sleep_for(1s);
+    {
+        // change the modified time
+        Poco::FileOutputStream fos(ca_path);
+        fos << options.value().pem_root_certs;
+    }
+    new_options = tiflash_config.readAndCacheSslCredentialOptions();
+    // no aware of the change since `update` is not called
+    ASSERT_FALSE(new_options.has_value());
+    ASSERT_TRUE(tiflash_config.update(*config));
+    // aware of the change and return a new options
+    new_options = tiflash_config.readAndCacheSslCredentialOptions();
+    ASSERT_TRUE(new_options.has_value());
+    Poco::File ca_file(ca_path);
+    ca_file.remove(false);
+    Poco::File cert_file(cert_path);
+    cert_file.remove(false);
+    Poco::File key_file(key_path);
+    key_file.remove(false);
+}
 } // namespace tests
 } // namespace DB

dbms/src/Common/tests/tls/ca.crt

@@ -0,0 +1,20 @@
+-----BEGIN CERTIFICATE-----
+MIIDWjCCAkKgAwIBAgIUWrP0VvHcy+LP6UuYNtiL9gBhD5owDQYJKoZIhvcNAQEL
+BQAwVjELMAkGA1UEBhMCQVUxEzARBgNVBAgMClNvbWUtU3RhdGUxITAfBgNVBAoM
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+eZiLl5FfrWokUNytFElXob0V0a5/kbhiLc3yWmvWqHTpqCALbVyF+rKJo2f5Kw==
+-----END CERTIFICATE-----

dbms/src/Common/tests/tls/cert.crt

@@ -0,0 +1,22 @@
+-----BEGIN CERTIFICATE-----
+MIIDtDCCApygAwIBAgIUbJfTREJ6k6/+oInWhV1O1j3ZT0IwDQYJKoZIhvcNAQEL
+BQAwVjELMAkGA1UEBhMCQVUxEzARBgNVBAgMClNvbWUtU3RhdGUxITAfBgNVBAoM
+GEludGVybmV0IFdpZGdpdHMgUHR5IEx0ZDEPMA0GA1UEAwwGdGVzdGNhMB4XDTIw
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+LCBDby4xGjAYBgNVBAMMESoudGVzdC5nb29nbGUuY29tMIIBIjANBgkqhkiG9w0B
+AQEFAAOCAQ8AMIIBCgKCAQEA5xOONxJJ8b8Qauvob5/7dPYZfIcd+uhAWL2ZlTPz
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+gc9ctPjSMvgSyXEKv6Vwobleeg88V2ZgzenziORoWj4KszG/lbQZvg==
+-----END CERTIFICATE-----

dbms/src/Common/tests/tls/key.pem

@@ -0,0 +1,28 @@
+-----BEGIN PRIVATE KEY-----
+MIIEvwIBADANBgkqhkiG9w0BAQEFAASCBKkwggSlAgEAAoIBAQDnE443EknxvxBq
+6+hvn/t09hl8hx366EBYvZmVM/NC+7igXRAjiJiA/mIaCvL3MS0Iz5hBLxSGICU+
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+uGIYs9Ek7YXlXIRVrzMwcsrt1w==
+-----END PRIVATE KEY-----

dbms/src/Server/FlashGrpcServerHolder.cpp

@@ -98,11 +98,15 @@ sslServerCertificateConfigCallback(
     }
     auto * context = static_cast<Context *>(arg);
     auto options = context->getSecurityConfig()->readAndCacheSslCredentialOptions();
-    grpc_ssl_pem_key_cert_pair pem_key_cert_pair = {options.pem_private_key.c_str(), options.pem_cert_chain.c_str()};
-    *config = grpc_ssl_server_certificate_config_create(options.pem_root_certs.c_str(),
-                                                        &pem_key_cert_pair,
-                                                        1);
-    return GRPC_SSL_CERTIFICATE_CONFIG_RELOAD_NEW;
+    if (options.has_value())
+    {
+        grpc_ssl_pem_key_cert_pair pem_key_cert_pair = {options.value().pem_private_key.c_str(), options.value().pem_cert_chain.c_str()};
+        *config = grpc_ssl_server_certificate_config_create(options.value().pem_root_certs.c_str(),
+                                                            &pem_key_cert_pair,
+                                                            1);
+        return GRPC_SSL_CERTIFICATE_CONFIG_RELOAD_NEW;
+    }
+    return GRPC_SSL_CERTIFICATE_CONFIG_RELOAD_UNCHANGED;
 }
 
 grpc_server_credentials * grpcSslServerCredentialsCreateWithFetcher(