privilege: fix auth_socket bug, should only allow os user name to login (#54032)

pkg/privilege/privileges/privileges.go

@@ -583,6 +583,13 @@ func (p *UserPrivileges) ConnectionVerification(user *auth.UserIdentity, authUse
 			logutil.BgLogger().Warn("verify through LDAP Simple failed", zap.String("username", user.Username), zap.Error(err))
 			return info, ErrAccessDenied.FastGenByArgs(user.Username, user.Hostname, hasPassword)
 		}
+	} else if record.AuthPlugin == mysql.AuthSocket {
+		if string(authentication) != authUser && string(authentication) != pwd {
+			logutil.BgLogger().Error("Failed socket auth", zap.String("authUser", authUser),
+				zap.String("socket_user", string(authentication)),
+				zap.String("authentication_string", pwd))
+			return info, ErrAccessDenied.FastGenByArgs(user.Username, user.Hostname, hasPassword)
+		}
 	} else if len(pwd) > 0 && len(authentication) > 0 {
 		switch record.AuthPlugin {
 		// NOTE: If the checking of the clear-text password fails, please set `info.FailedDueToWrongPassword = true`.
@@ -608,22 +615,13 @@ func (p *UserPrivileges) ConnectionVerification(user *auth.UserIdentity, authUse
 				info.FailedDueToWrongPassword = true
 				return info, ErrAccessDenied.FastGenByArgs(user.Username, user.Hostname, hasPassword)
 			}
-		case mysql.AuthSocket:
-			if string(authentication) != authUser && string(authentication) != pwd {
-				logutil.BgLogger().Error("Failed socket auth", zap.String("authUser", authUser),
-					zap.String("socket_user", string(authentication)),
-					zap.String("authentication_string", pwd))
-				return info, ErrAccessDenied.FastGenByArgs(user.Username, user.Hostname, hasPassword)
-			}
 		default:
 			logutil.BgLogger().Error("unknown authentication plugin", zap.String("authUser", authUser), zap.String("plugin", record.AuthPlugin))
 			return info, ErrAccessDenied.FastGenByArgs(user.Username, user.Hostname, hasPassword)
 		}
 	} else if len(pwd) > 0 || len(authentication) > 0 {
-		if record.AuthPlugin != mysql.AuthSocket {
-			info.FailedDueToWrongPassword = true
-			return info, ErrAccessDenied.FastGenByArgs(user.Username, user.Hostname, hasPassword)
-		}
+		info.FailedDueToWrongPassword = true
+		return info, ErrAccessDenied.FastGenByArgs(user.Username, user.Hostname, hasPassword)
 	}
 
 	// Login a locked account is not allowed.

pkg/server/conn.go

@@ -98,6 +98,7 @@ import (
 	"github.com/pingcap/tidb/pkg/util/dbterror/exeerrors"
 	"github.com/pingcap/tidb/pkg/util/execdetails"
 	"github.com/pingcap/tidb/pkg/util/hack"
+	"github.com/pingcap/tidb/pkg/util/intest"
 	"github.com/pingcap/tidb/pkg/util/logutil"
 	"github.com/pingcap/tidb/pkg/util/memory"
 	"github.com/pingcap/tidb/pkg/util/resourcegrouptag"
@@ -771,6 +772,9 @@ func (cc *clientConn) openSessionAndDoAuth(authData []byte, authPlugin string) e
 	return nil
 }
 
+// mockOSUserForAuthSocketTest should only be used in test
+var mockOSUserForAuthSocketTest atomic.Pointer[string]
+
 // Check if the Authentication Plugin of the server, client and user configuration matches
 func (cc *clientConn) checkAuthPlugin(ctx context.Context, resp *handshake.Response41) ([]byte, error) {
 	// Open a context unless this was done before.
@@ -819,7 +823,15 @@ func (cc *clientConn) checkAuthPlugin(ctx context.Context, resp *handshake.Respo
 		if err != nil {
 			return nil, err
 		}
-		return []byte(user.Username), nil
+		uname := user.Username
+
+		if intest.InTest {
+			if p := mockOSUserForAuthSocketTest.Load(); p != nil {
+				uname = *p
+			}
+		}
+
+		return []byte(uname), nil
 	}
 	if len(userplugin) == 0 {
 		// No user plugin set, assuming MySQL Native Password

pkg/server/mock_conn.go

@@ -140,3 +140,13 @@ func CreateMockConn(t *testing.T, server *Server) MockConn {
 		t:          t,
 	}
 }
+
+// MockOSUserForAuthSocket mocks the OS user for AUTH_SOCKET plugin
+func MockOSUserForAuthSocket(uname string) {
+	mockOSUserForAuthSocketTest.Store(&uname)
+}
+
+// ClearOSUserForAuthSocket clears the mocked OS user for AUTH_SOCKET plugin
+func ClearOSUserForAuthSocket() {
+	mockOSUserForAuthSocketTest.Store(nil)
+}

pkg/server/tests/tidb_test.go

@@ -3144,3 +3144,72 @@ func TestConnectionCount(t *testing.T) {
 	ts := servertestkit.CreateTidbTestSuite(t)
 	ts.RunTestConnectionCount(t)
 }
+
+func TestAuthSocket(t *testing.T) {
+	defer server2.ClearOSUserForAuthSocket()
+
+	cfg := util2.NewTestConfig()
+	cfg.Socket = filepath.Join(t.TempDir(), "authsock.sock")
+	cfg.Port = 0
+	cfg.Status.StatusPort = 0
+	ts := servertestkit.CreateTidbTestSuiteWithCfg(t, cfg)
+	ts.WaitUntilServerCanConnect()
+
+	ts.RunTests(t, nil, func(dbt *testkit.DBTestKit) {
+		dbt.MustExec("CREATE USER 'u1'@'%' IDENTIFIED WITH auth_socket;")
+		dbt.MustExec("CREATE USER 'u2'@'%' IDENTIFIED WITH auth_socket AS 'sockuser'")
+		dbt.MustExec("CREATE USER 'sockuser'@'%' IDENTIFIED WITH auth_socket;")
+	})
+
+	// network login should be denied
+	for _, uname := range []string{"u1", "u2", "u3"} {
+		server2.MockOSUserForAuthSocket(uname)
+		db, err := sql.Open("mysql", ts.GetDSN(func(config *mysql.Config) {
+			config.User = uname
+		}))
+		require.NoError(t, err)
+		_, err = db.Conn(context.TODO())
+		require.EqualError(t,
+			err,
+			fmt.Sprintf("Error 1045 (28000): Access denied for user '%s'@'127.0.0.1' (using password: NO)", uname),
+		)
+		require.NoError(t, db.Close())
+	}
+
+	socketAuthConf := func(user string) func(*mysql.Config) {
+		return func(config *mysql.Config) {
+			config.User = user
+			config.Net = "unix"
+			config.Addr = cfg.Socket
+			config.DBName = ""
+		}
+	}
+
+	server2.MockOSUserForAuthSocket("sockuser")
+
+	// mysql username that is different with the OS user should be rejected.
+	db, err := sql.Open("mysql", ts.GetDSN(socketAuthConf("u1")))
+	require.NoError(t, err)
+	_, err = db.Conn(context.TODO())
+	require.EqualError(t, err, "Error 1045 (28000): Access denied for user 'u1'@'localhost' (using password: YES)")
+	require.NoError(t, db.Close())
+
+	// mysql username that is the same with the OS user should be accepted.
+	ts.RunTests(t, socketAuthConf("sockuser"), func(dbt *testkit.DBTestKit) {
+		rows := dbt.MustQuery("select current_user();")
+		ts.CheckRows(t, rows, "sockuser@%")
+	})
+
+	// When a user is created with `IDENTIFIED WITH auth_socket AS ...`.
+	// It should be accepted when username or as string is the same with OS user.
+	ts.RunTests(t, socketAuthConf("u2"), func(dbt *testkit.DBTestKit) {
+		rows := dbt.MustQuery("select current_user();")
+		ts.CheckRows(t, rows, "u2@%")
+	})
+
+	server2.MockOSUserForAuthSocket("u2")
+	ts.RunTests(t, socketAuthConf("u2"), func(dbt *testkit.DBTestKit) {
+		rows := dbt.MustQuery("select current_user();")
+		ts.CheckRows(t, rows, "u2@%")
+	})
+}