6.1.6 Security Issues with LOAD DATA LOCAL

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The LOAD DATA statement can load a file located on the server host, or, if the LOCAL keyword is specified, on the client host.

There are two potential security issues with the LOCAL version of LOAD DATA:

The transfer of the file from the client host to the server host is initiated by the MySQL server. In theory, a patched server could be built that would tell the client program to transfer a file of the server's choosing rather than the file named by the client in the LOAD DATA 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 just LOAD 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 LOAD DATA issues, clients should avoid using LOCAL. 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 enable adminstrators and applications to manage the local data loading capability, LOCAL configuration works like this:

On the server side:
- The local_infile system variable controls server-side LOCAL capability. Depending on the local_infile setting, the server refuses or permits local data loading by clients that have LOCAL enabled on the client side. By default, local_infile is disabled.
- To explicitly cause the server to refuse or permit LOAD DATA LOCAL statements (regardless of how client programs and libraries are configured at build time or runtime), start mysqld with local_infile disabled or enabled, respectively. local_infile can also be set at runtime.
On the client side:
- The ENABLED_LOCAL_INFILE CMake option controls the compiled-in default LOCAL capability for the MySQL client library. Clients that make no explicit arrangements therefore have LOCAL capability disabled or enabled according to the ENABLED_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 with ENABLED_LOCAL_INFILE disabled or enabled based on whether clients that make no explicit arrangements should have LOCAL capability disabled or enabled, respectively.
- Client programs that use the C API can control load data loading explicitly by invoking mysql_options() to disable or enable the MYSQL_OPT_LOCAL_INFILE option. See Section 28.7.7.50, “mysql_options()”.
- For the mysql client, local data loading is disabled by default. To disable or enable it explicitly, use the --local-infile=0 or --local-infile[=1] option.
- For the mysqlimport client, local data loading is disabled 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 an local-infile option setting to that group. To prevent problems for programs that do not understand this option, specify it using the loose- 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 it.

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

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Document created the 26/06/2006, last modified the 26/10/2018
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References

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