MySQL takes the following measures to prevent misuse of user-defined functions.
You must have the INSERT
privilege to be able to use CREATE
FUNCTION
and the
DELETE
privilege to be able to
use DROP FUNCTION
. This is
necessary because these statements add and delete rows from
the mysql.func
table.
UDFs should have at least one symbol defined in addition to
the xxx
symbol that corresponds to the main
xxx()
function. These auxiliary symbols
correspond to the xxx_init()
,
xxx_deinit()
,
xxx_reset()
,
xxx_clear()
, and
xxx_add()
functions. As of MySQL 4.0.24 and
4.1.10a, mysqld supports an
--allow-suspicious-udfs
option
that controls whether UDFs that have only an
xxx
symbol can be loaded. By default, the
option is off, to prevent attempts at loading functions from
shared object files other than those containing legitimate
UDFs. If you have older UDFs that contain only the
xxx
symbol and that cannot be recompiled to
include an auxiliary symbol, it may be necessary to specify
the --allow-suspicious-udfs
option. Otherwise, you should avoid enabling this capability.
UDF object files cannot be placed in arbitrary directories.
They must be located in some system directory that the dynamic
linker is configured to search. To enforce this restriction
and prevent attempts at specifying path names outside of
directories searched by the dynamic linker, MySQL checks the
shared object file name specified in
CREATE FUNCTION
statements for
path name delimiter characters. As of MySQL 4.0.24 and
4.1.10a, MySQL also checks for path name delimiters in file
names stored in the mysql.func
table when
it loads functions. This prevents attempts at specifying
illegitimate path names through direct manipulation of the
mysql.func
table. For information about
UDFs and the runtime linker, see
Section 18.2.2.5, “Compiling and Installing User-Defined Functions”.
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