MySQL Server supports a keyring service that enables internal components and plugins to store sensitive information securely for later retrieval.
MySQL Server also includes an SQL interface for keyring key
management, implemented as a set of general-purpose functions
that access the capabilities provided by the internal keyring
service. The keyring functions are contained in a plugin library
file, which also contains a keyring_udf
plugin that must be enabled prior to function invocation. For
these functions to be used, a keyring plugin such as
keyring_file
or
keyring_okv
, or a keyring component such as
component_keyring_file
or
component_keyring_encrypted_file
, must be
enabled.
The functions described here are general-purpose and intended for use with any keyring component or plugin. A given keyring component or plugin may also provide functions of its own that are intended for use only with that component or plugin; see Section 8.4.4.16, “Plugin-Specific Keyring Key-Management Functions”.
The following sections provide installation instructions for the keyring functions and demonstrate how to use them. For information about the keyring service functions invoked by these functions, see Section 7.6.9.2, “The Keyring Service”. For general keyring information, see Section 8.4.4, “The MySQL Keyring”.
This section describes how to install or uninstall the keyring
functions, which are implemented in a plugin library file that
also contains a keyring_udf
plugin. For
general information about installing or uninstalling plugins
and loadable functions, see Section 7.6.1, “Installing and Uninstalling Plugins”,
and Section 7.7.1, “Installing and Uninstalling Loadable Functions”.
The keyring functions enable keyring key management
operations, but the keyring_udf
plugin must
also be installed because the functions do not work correctly
without it. Attempts to use the functions without the
keyring_udf
plugin result in an error.
To be usable by the server, the plugin library file must be
located in the MySQL plugin directory (the directory named by
the plugin_dir
system
variable). If necessary, configure the plugin directory
location by setting the value of
plugin_dir
at server startup.
The plugin library file base name is
keyring_udf
. The file name suffix differs
per platform (for example, .so
for Unix
and Unix-like systems, .dll
for Windows).
To install the keyring_udf
plugin and the
keyring functions, use the INSTALL
PLUGIN
and CREATE
FUNCTION
statements, adjusting the
.so
suffix for your platform as
necessary:
INSTALL PLUGIN keyring_udf SONAME 'keyring_udf.so';
CREATE FUNCTION keyring_key_generate RETURNS INTEGER
SONAME 'keyring_udf.so';
CREATE FUNCTION keyring_key_fetch RETURNS STRING
SONAME 'keyring_udf.so';
CREATE FUNCTION keyring_key_length_fetch RETURNS INTEGER
SONAME 'keyring_udf.so';
CREATE FUNCTION keyring_key_type_fetch RETURNS STRING
SONAME 'keyring_udf.so';
CREATE FUNCTION keyring_key_store RETURNS INTEGER
SONAME 'keyring_udf.so';
CREATE FUNCTION keyring_key_remove RETURNS INTEGER
SONAME 'keyring_udf.so';
If the plugin and functions are used on a source replication server, install them on all replicas as well to avoid replication issues.
Once installed as just described, the plugin and functions
remain installed until uninstalled. To remove them, use the
UNINSTALL PLUGIN
and
DROP FUNCTION
statements:
UNINSTALL PLUGIN keyring_udf;
DROP FUNCTION keyring_key_generate;
DROP FUNCTION keyring_key_fetch;
DROP FUNCTION keyring_key_length_fetch;
DROP FUNCTION keyring_key_type_fetch;
DROP FUNCTION keyring_key_store;
DROP FUNCTION keyring_key_remove;
Before using the keyring general-purpose functions, install them according to the instructions provided in Installing or Uninstalling General-Purpose Keyring Functions.
The keyring functions are subject to these constraints:
To use any keyring function, the
keyring_udf
plugin must be enabled. Otherwise, an error occurs:ERROR 1123 (HY000): Can't initialize function 'keyring_key_generate'; This function requires keyring_udf plugin which is not installed. Please install
To install the
keyring_udf
plugin, see Installing or Uninstalling General-Purpose Keyring Functions.The keyring functions invoke keyring service functions (see Section 7.6.9.2, “The Keyring Service”). The service functions in turn use whatever keyring plugin is installed (for example,
keyring_file
orkeyring_okv
). Therefore, to use any keyring function, some underlying keyring plugin must be enabled. Otherwise, an error occurs:ERROR 3188 (HY000): Function 'keyring_key_generate' failed because underlying keyring service returned an error. Please check if a keyring plugin is installed and that provided arguments are valid for the keyring you are using.
To install a keyring plugin, see Section 8.4.4.3, “Keyring Plugin Installation”.
A user must possess the global
EXECUTE
privilege to use any keyring function. Otherwise, an error occurs:ERROR 1123 (HY000): Can't initialize function 'keyring_key_generate'; The user is not privileged to execute this function. User needs to have EXECUTE
To grant the global
EXECUTE
privilege to a user, use this statement:GRANT EXECUTE ON *.* TO user;
Alternatively, should you prefer to avoid granting the global
EXECUTE
privilege while still permitting users to access specific key-management operations, “wrapper” stored programs can be defined (a technique described later in this section).A key stored in the keyring by a given user can be manipulated later only by the same user. That is, the value of the
CURRENT_USER()
function at the time of key manipulation must have the same value as when the key was stored in the keyring. (This constraint rules out the use of the keyring functions for manipulation of instance-wide keys, such as those created byInnoDB
to support tablespace encryption.)To enable multiple users to perform operations on the same key, “wrapper” stored programs can be defined (a technique described later in this section).
Keyring functions support the key types and lengths supported by the underlying keyring plugin. For information about keys specific to a particular keyring plugin, see Section 8.4.4.13, “Supported Keyring Key Types and Lengths”.
To create a new random key and store it in the keyring, call
keyring_key_generate()
, passing
to it an ID for the key, along with the key type (encryption
method) and its length in bytes. The following call creates a
2,048-bit DSA-encrypted key named MyKey
:
mysql> SELECT keyring_key_generate('MyKey', 'DSA', 256);
+-------------------------------------------+
| keyring_key_generate('MyKey', 'DSA', 256) |
+-------------------------------------------+
| 1 |
+-------------------------------------------+
A return value of 1 indicates success. If the key cannot be
created, the return value is NULL
and an
error occurs. One reason this might be is that the underlying
keyring plugin does not support the specified combination of
key type and key length; see
Section 8.4.4.13, “Supported Keyring Key Types and Lengths”.
To be able to check the return type regardless of whether an
error occurs, use SELECT ... INTO
@
and test the
variable value:
var_name
mysql> SELECT keyring_key_generate('', '', -1) INTO @x;
ERROR 3188 (HY000): Function 'keyring_key_generate' failed because
underlying keyring service returned an error. Please check if a
keyring plugin is installed and that provided arguments are valid
for the keyring you are using.
mysql> SELECT @x;
+------+
| @x |
+------+
| NULL |
+------+
mysql> SELECT keyring_key_generate('x', 'AES', 16) INTO @x;
mysql> SELECT @x;
+------+
| @x |
+------+
| 1 |
+------+
This technique also applies to other keyring functions that for failure return a value and an error.
The ID passed to
keyring_key_generate()
provides
a means by which to refer to the key in subsequent functions
calls. For example, use the key ID to retrieve its type as a
string or its length in bytes as an integer:
mysql> SELECT keyring_key_type_fetch('MyKey');
+---------------------------------+
| keyring_key_type_fetch('MyKey') |
+---------------------------------+
| DSA |
+---------------------------------+
mysql> SELECT keyring_key_length_fetch('MyKey');
+-----------------------------------+
| keyring_key_length_fetch('MyKey') |
+-----------------------------------+
| 256 |
+-----------------------------------+
To retrieve a key value, pass the key ID to
keyring_key_fetch()
. The
following example uses HEX()
to
display the key value because it may contain nonprintable
characters. The example also uses a short key for brevity, but
be aware that longer keys provide better security:
mysql> SELECT keyring_key_generate('MyShortKey', 'DSA', 8);
+----------------------------------------------+
| keyring_key_generate('MyShortKey', 'DSA', 8) |
+----------------------------------------------+
| 1 |
+----------------------------------------------+
mysql> SELECT HEX(keyring_key_fetch('MyShortKey'));
+--------------------------------------+
| HEX(keyring_key_fetch('MyShortKey')) |
+--------------------------------------+
| 1DB3B0FC3328A24C |
+--------------------------------------+
Keyring functions treat key IDs, types, and values as binary
strings, so comparisons are case-sensitive. For example, IDs
of MyKey
and mykey
refer
to different keys.
To remove a key, pass the key ID to
keyring_key_remove()
:
mysql> SELECT keyring_key_remove('MyKey');
+-----------------------------+
| keyring_key_remove('MyKey') |
+-----------------------------+
| 1 |
+-----------------------------+
To obfuscate and store a key that you provide, pass the key
ID, type, and value to
keyring_key_store()
:
mysql> SELECT keyring_key_store('AES_key', 'AES', 'Secret string');
+------------------------------------------------------+
| keyring_key_store('AES_key', 'AES', 'Secret string') |
+------------------------------------------------------+
| 1 |
+------------------------------------------------------+
As indicated previously, a user must have the global
EXECUTE
privilege to call
keyring functions, and the user who stores a key in the
keyring initially must be the same user who performs
subsequent operations on the key later, as determined from the
CURRENT_USER()
value in effect
for each function call. To permit key operations to users who
do not have the global EXECUTE
privilege or who may not be the key “owner,” use
this technique:
Define “wrapper” stored programs that encapsulate the required key operations and have a
DEFINER
value equal to the key owner.Grant the
EXECUTE
privilege for specific stored programs to the individual users who should be able to invoke them.If the operations implemented by the wrapper stored programs do not include key creation, create any necessary keys in advance, using the account named as the
DEFINER
in the stored program definitions.
This technique enables keys to be shared among users and provides to DBAs more fine-grained control over who can do what with keys, without having to grant global privileges.
The following example shows how to set up a shared key named
SharedKey
that is owned by the DBA, and a
get_shared_key()
stored function that
provides access to the current key value. The value can be
retrieved by any user with the
EXECUTE
privilege for that
function, which is created in the
key_schema
schema.
From a MySQL administrative account
('root'@'localhost'
in this example),
create the administrative schema and the stored function to
access the key:
mysql> CREATE SCHEMA key_schema;
mysql> CREATE DEFINER = 'root'@'localhost'
FUNCTION key_schema.get_shared_key()
RETURNS BLOB READS SQL DATA
RETURN keyring_key_fetch('SharedKey');
From the administrative account, ensure that the shared key exists:
mysql> SELECT keyring_key_generate('SharedKey', 'DSA', 8);
+---------------------------------------------+
| keyring_key_generate('SharedKey', 'DSA', 8) |
+---------------------------------------------+
| 1 |
+---------------------------------------------+
From the administrative account, create an ordinary user account to which key access is to be granted:
mysql> CREATE USER 'key_user'@'localhost'
IDENTIFIED BY 'key_user_pwd';
From the key_user
account, verify that,
without the proper EXECUTE
privilege, the new account cannot access the shared key:
mysql> SELECT HEX(key_schema.get_shared_key());
ERROR 1370 (42000): execute command denied to user 'key_user'@'localhost'
for routine 'key_schema.get_shared_key'
From the administrative account, grant
EXECUTE
to
key_user
for the stored function:
mysql> GRANT EXECUTE ON FUNCTION key_schema.get_shared_key
TO 'key_user'@'localhost';
From the key_user
account, verify that the
key is now accessible:
mysql> SELECT HEX(key_schema.get_shared_key());
+----------------------------------+
| HEX(key_schema.get_shared_key()) |
+----------------------------------+
| 9BAFB9E75CEEB013 |
+----------------------------------+
For each general-purpose keyring function, this section describes its purpose, calling sequence, and return value. For information about the conditions under which these functions can be invoked, see Using General-Purpose Keyring Functions.
Given a key ID, deobfuscates and returns the key value.
Arguments:
key_id
: A string that specifies the key ID.
Return value:
Returns the key value as a string for success,
NULL
if the key does not exist, orNULL
and an error for failure.NoteKey values retrieved using
keyring_key_fetch()
are subject to the general keyring function limits described in Section 8.4.4.13, “Supported Keyring Key Types and Lengths”. A key value longer than that length can be stored using a keyring service function (see Section 7.6.9.2, “The Keyring Service”), but if retrieved usingkeyring_key_fetch()
is truncated to the general keyring function limit.Example:
mysql> SELECT keyring_key_generate('RSA_key', 'RSA', 16); +--------------------------------------------+ | keyring_key_generate('RSA_key', 'RSA', 16) | +--------------------------------------------+ | 1 | +--------------------------------------------+ mysql> SELECT HEX(keyring_key_fetch('RSA_key')); +-----------------------------------+ | HEX(keyring_key_fetch('RSA_key')) | +-----------------------------------+ | 91C2253B696064D3556984B6630F891A | +-----------------------------------+ mysql> SELECT keyring_key_type_fetch('RSA_key'); +-----------------------------------+ | keyring_key_type_fetch('RSA_key') | +-----------------------------------+ | RSA | +-----------------------------------+ mysql> SELECT keyring_key_length_fetch('RSA_key'); +-------------------------------------+ | keyring_key_length_fetch('RSA_key') | +-------------------------------------+ | 16 | +-------------------------------------+
The example uses
HEX()
to display the key value because it may contain nonprintable characters. The example also uses a short key for brevity, but be aware that longer keys provide better security.keyring_key_generate(
key_id
,key_type
,key_length
)Generates a new random key with a given ID, type, and length, and stores it in the keyring. The type and length values must be consistent with the values supported by the underlying keyring plugin. See Section 8.4.4.13, “Supported Keyring Key Types and Lengths”.
Arguments:
key_id
: A string that specifies the key ID.key_type
: A string that specifies the key type.key_length
: An integer that specifies the key length in bytes.
Return value:
Returns 1 for success, or
NULL
and an error for failure.Example:
mysql> SELECT keyring_key_generate('RSA_key', 'RSA', 384); +---------------------------------------------+ | keyring_key_generate('RSA_key', 'RSA', 384) | +---------------------------------------------+ | 1 | +---------------------------------------------+
keyring_key_length_fetch(
key_id
)Given a key ID, returns the key length.
Arguments:
key_id
: A string that specifies the key ID.
Return value:
Returns the key length in bytes as an integer for success,
NULL
if the key does not exist, orNULL
and an error for failure.Example:
See the description of
keyring_key_fetch()
.Removes the key with a given ID from the keyring.
Arguments:
key_id
: A string that specifies the key ID.
Return value:
Returns 1 for success, or
NULL
for failure.Example:
mysql> SELECT keyring_key_remove('AES_key'); +-------------------------------+ | keyring_key_remove('AES_key') | +-------------------------------+ | 1 | +-------------------------------+
keyring_key_store(
key_id
,key_type
,key
)Obfuscates and stores a key in the keyring.
Arguments:
key_id
: A string that specifies the key ID.key_type
: A string that specifies the key type.key
: A string that specifies the key value.
Return value:
Returns 1 for success, or
NULL
and an error for failure.Example:
mysql> SELECT keyring_key_store('new key', 'DSA', 'My key value'); +-----------------------------------------------------+ | keyring_key_store('new key', 'DSA', 'My key value') | +-----------------------------------------------------+ | 1 | +-----------------------------------------------------+
keyring_key_type_fetch(
key_id
)Given a key ID, returns the key type.
Arguments:
key_id
: A string that specifies the key ID.
Return value:
Returns the key type as a string for success,
NULL
if the key does not exist, orNULL
and an error for failure.Example:
See the description of
keyring_key_fetch()
.