8.1.6 安全性 Considerations for LOAD DATA LOCAL
The LOAD DATA
statement loads a data file into a table. The statement can load a file located on the server host, or, if the LOCAL
keyword is specified, on the client host.
The LOCAL
version of LOAD DATA
has two potential security issues:
-
Because
LOAD DATA LOCAL
is an SQL statement, parsing occurs on the server side, and transfer of the file from the client host to the server host is initiated by the MySQL server, which tells the client the file named in the statement. In theory, a patched server could tell the client program to transfer a file of the server's choosing rather than the file named in the statement. Such a server could access any file on the client host to which the client user has read access. (A patched server could in fact reply with a file-transfer request to any statement, not justLOAD DATA LOCAL
, so a more fundamental issue is that clients should not connect to untrusted servers.) -
In a Web environment where the clients are connecting from a Web server, a user could use
LOAD DATA LOCAL
to read any files that the Web server process has read access to (assuming that a user could run any statement against the SQL server). In this environment, the client with respect to the MySQL server actually is the Web server, not a remote program being run by users who connect to the Web server.
To avoid connecting to untrusted servers, clients can establish a secure connection and verify the server identity by connecting using the --ssl-mode=VERIFY_IDENTITY
option and the appropriate CA certificate. To implement this level of verification, you must first ensure that the CA certificate for the server is reliably available to the replica, otherwise availability issues will result. For more information, see Command Options for Encrypted Connections.
To avoid LOAD DATA
issues, clients should avoid using LOCAL
unless proper client-side precautions have been taken.
For control over local data loading, MySQL permits the capability to be enabled or disabled. MySQL also enables clients to restrict local data loading operations to files located in a designated directory.
Administrators and applications can configure whether to permit local data loading as follows:
-
On the server side:
-
The
local_infile
system variable controls server-sideLOCAL
capability. Depending on thelocal_infile
setting, the server refuses or permits local data loading by clients that request local data loading. -
By default,
local_infile
is disabled. (This is a change from previous versions of MySQL.) To cause the server to refuse or permitLOAD DATA LOCAL
statements explicitly (regardless of how client programs and libraries are configured at build time or runtime), start mysqld withlocal_infile
disabled or enabled.local_infile
can also be set at runtime.
-
-
On the client side:
-
The
ENABLED_LOCAL_INFILE
CMake option controls the compiled-in defaultLOCAL
capability for the MySQL client library (see Section 2.8.7, “MySQL Source-Configuration Options”). Clients that make no explicit arrangements therefore haveLOCAL
capability disabled or enabled according to theENABLED_LOCAL_INFILE
setting specified at MySQL build time. -
By default, the client library in MySQL binary distributions is compiled with
ENABLED_LOCAL_INFILE
disabled. If you compile MySQL from source, configure it withENABLED_LOCAL_INFILE
disabled or enabled based on whether clients that make no explicit arrangements should haveLOCAL
capability disabled or enabled. -
For client programs that use the C API, local data loading capability is determined by the default compiled into the MySQL client library. To enable or disable it explicitly, invoke the
mysql_options()
C API function to disable or enable theMYSQL_OPT_LOCAL_INFILE
option. See mysql_options(). -
For the mysql client, local data loading capability is determined by the default compiled into the MySQL client library. To disable or enable it explicitly, use the
--local-infile=0
or--local-infile[=1]
option. -
For the mysqlimport client, local data loading is not used by default. To disable or enable it explicitly, use the
--local=0
or--local[=1]
option. -
If you use
LOAD DATA LOCAL
in Perl scripts or other programs that read the[client]
group from option files, you can add alocal-infile
option setting to that group. To prevent problems for programs that do not understand this option, specify it using theloose-
prefix:[client] loose-local-infile=0
or:
[client] loose-local-infile=1
-
In all cases, successful use of a
LOCAL
load operation by a client also requires that the server permits local loading.
-
If LOCAL
capability is disabled, on either the server or client side, a client that attempts to issue a LOAD DATA LOCAL
statement receives the following error message:
ERROR 3950 (42000): Loading local data is disabled; this must be
enabled on both the client and server side
The MySQL client library enables client applications to restrict local data loading operations to files located in a designated directory. Certain MySQL client programs take advantage of this capability.
Client programs that use the C API can control which files to permit for load data loading using the MYSQL_OPT_LOCAL_INFILE
and MYSQL_OPT_LOAD_DATA_LOCAL_DIR
options of the mysql_options()
C API function (see mysql_options()).
The effect of MYSQL_OPT_LOAD_DATA_LOCAL_DIR
depends on whether LOCAL
data loading is enabled or disabled:
-
If
LOCAL
data loading is enabled, either by default in the MySQL client library or by explicitly enablingMYSQL_OPT_LOCAL_INFILE
, theMYSQL_OPT_LOAD_DATA_LOCAL_DIR
option has no effect. -
If
LOCAL
data loading is disabled, either by default in the MySQL client library or by explicitly disablingMYSQL_OPT_LOCAL_INFILE
, theMYSQL_OPT_LOAD_DATA_LOCAL_DIR
option can be used to designate a permitted directory for locally loaded files. In this case,LOCAL
data loading is permitted but restricted to files located in the designated directory. Interpretation of theMYSQL_OPT_LOAD_DATA_LOCAL_DIR
value is as follows:-
If the value is the null pointer (the default), it names no directory, with the result that no files are permitted for
LOCAL
data loading. -
If the value is a directory path name,
LOCAL
data loading is permitted but restricted to files located in the named directory. Comparison of the directory path name and the path name of files to be loaded is case-sensitive regardless of the case sensitivity of the underlying file system.
-
MySQL client programs use the preceding mysql_options()
options as follows:
-
The mysql client has a
--load-data-local-dir
option that takes a directory path or an empty string. mysql uses the option value to set theMYSQL_OPT_LOAD_DATA_LOCAL_DIR
option (with an empty string setting the value to the null pointer). The effect of--load-data-local-dir
depends on whetherLOCAL
data loading is enabled:-
If
LOCAL
data loading is enabled, either by default in the MySQL client library or by specifying--local-infile[=1]
, the--load-data-local-dir
option is ignored. -
If
LOCAL
data loading is disabled, either by default in the MySQL client library or by specifying--local-infile=0
, the--load-data-local-dir
option applies.
When
--load-data-local-dir
applies, the option value designates the directory in which local data files must be located. Comparison of the directory path name and the path name of files to be loaded is case-sensitive regardless of the case sensitivity of the underlying file system. If the option value is the empty string, it names no directory, with the result that no files are permitted for local data loading. -
-
mysqlimport sets
MYSQL_OPT_LOAD_DATA_LOCAL_DIR
for each file that it processes so that the directory containing the file is the permitted local loading directory. -
For data loading operations corresponding to
LOAD DATA
statements, mysqlbinlog extracts the files from the binary log events, writes them as temporary files to the local file system, and writesLOAD DATA LOCAL
statements to cause the files to be loaded. By default, mysqlbinlog writes these temporary files to an operating system-specific directory. The--local-load
option can be used to explicitly specify the directory where mysqlbinlog should prepare local temporary files.Because other processes can write files to the default system-specific directory, it is advisable to specify the
--local-load
option to mysqlbinlog to designate a different directory for data files, and then designate that same directory by specifying the--load-data-local-dir
option to mysql when processing the output from mysqlbinlog.
MySQL Shell and Local Data Loading
MySQL Shell provides a number of utilities to dump tables, schemas, or server instances and load them into other instances. When you use these utilities to handle the data, MySQL Shell provides additional functions such as input preprocessing, multithreaded parallel loading, file compression and decompression, and handling access to Oracle Cloud Infrastructure Object Storage buckets. To get the best functionality, always use the most recent version available of MySQL Shell's dump and dump loading utilities.
MySQL Shell's data upload utilities use LOAD DATA LOCAL INFILE
statements to upload data, so the local_infile
system variable must be set to ON
on the target server instance. You can do this before uploading the data, and remove it again afterwards. The utilities handle the file transfer requests safely to deal with the security considerations discussed in this topic.
MySQL Shell includes these dump and dump loading utilities:
-
Table export utility
util.exportTable()
-
Exports a MySQL relational table into a data file, which can be uploaded to a MySQL server instance using MySQL Shell's parallel table import utility, imported to a different application, or used as a logical backup. The utility has preset options and customization options to produce different output formats.
-
Parallel table import utility
util.importTable()
-
Imports a data file to a MySQL relational table. The data file can be the output from MySQL Shell's table export utility or another format supported by the utility's preset and customization options. The utility can carry out input preprocessing before adding the data to the table. It can accept multiple data files to merge into a single relational table, and automatically decompresses compressed files.
-
Instance dump utility
util.dumpInstance()
, schema dump utilityutil.dumpSchemas()
, and table dump utilityutil.dumpTables()
-
Export an instance, schema, or table to a set of dump files, which can then be uploaded to a MySQL instance using MySQL Shell's dump loading utility. The utilities provide Oracle Cloud Infrastructure Object Storage streaming, MySQL HeatWave Service compatibility checks and modifications, and the ability to carry out a dry run to identify issues before proceeding with the dump.
-
Dump loading utility
util.loadDump()
-
Import dump files created using MySQL Shell's instance, schema, or table dump utility into a MySQL HeatWave Service DB System or a MySQL Server instance. The utility manages the upload process and provides data streaming from remote storage, parallel loading of tables or table chunks, progress state tracking, resume and reset capability, and the option of concurrent loading while the dump is still taking place. MySQL Shell’s parallel table import utility can be used in combination with the dump loading utility to modify data before uploading it to the target MySQL instance.
For details of the utilities, see MySQL Shell Utilities.