6.1.6 Security 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 avoid LOAD DATA
issues, clients should avoid using LOCAL
.
Adminstrators 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. To explicitly cause the server to refuse or permitLOAD DATA LOCAL
statements (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 2.9.7, “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
enabled. 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 Section 27.7.6.50, “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 1148: The used command is not allowed with this MySQL version