14.21.4 Security Considerations for the InnoDB memcached Plugin

Caution

Consult this section before deploying the daemon_memcached plugin on a production server, or even on a test server if the MySQL instance contains sensitive data.

Because memcached does not use an authentication mechanism by default, and the optional SASL authentication is not as strong as traditional DBMS security measures, only keep non-sensitive data in the MySQL instance that uses the daemon_memcached plugin, and wall off any servers that use this configuration from potential intruders. Do not allow memcached access to these servers from the Internet; only allow access from within a firewalled intranet, ideally from a subnet whose membership you can restrict.

Password-Protecting memcached Using SASL

SASL support provides the capability to protect your MySQL database from unauthenticated access through memcached clients. This section explains how to enable SASL with the daemon_memcached plugin. The steps are almost identical to those performed to enabled SASL for a traditional memcached server.

SASL stands for “Simple Authentication and Security Layer”, a standard for adding authentication support to connection-based protocols. memcached added SASL support in version 1.4.3.

SASL authentication is only supported with the binary protocol.

memcached clients are only able to access InnoDB tables that are registered in the innodb_memcache.containers table. Even though a DBA can place access restrictions on such tables, access through memcached applications cannot be controlled. For this reason, SASL support is provided to control access to InnoDB tables associated with the daemon_memcached plugin.

The following section shows how to build, enable, and test an SASL-enabled daemon_memcached plugin.

Building and Enabling SASL with the InnoDB memcached Plugin

By default, an SASL-enabled daemon_memcached plugin is not included in MySQL release packages, since an SASL-enabled daemon_memcached plugin requires building memcached with SASL libraries. To enable SASL support, download the MySQL source and rebuild the daemon_memcached plugin after downloading the SASL libraries:

1. Install the SASL development and utility libraries. For example, on Ubuntu, use apt-get to obtain the libraries:

   sudo apt-get -f install libsasl2-2 sasl2-bin libsasl2-2 libsasl2-dev libsasl2-modules

2. Build the daemon_memcached plugin shared libraries with SASL capability by adding ENABLE_MEMCACHED_SASL=1 to your cmake options. memcached also provides simple cleartext password support, which facilitates testing. To enable simple cleartext password support, specify the ENABLE_MEMCACHED_SASL_PWDB=1 cmake option.

   In summary, add following three cmake options:

   cmake ... -DWITH_INNODB_MEMCACHED=1 -DENABLE_MEMCACHED_SASL=1 -DENABLE_MEMCACHED_SASL_PWDB=1

3. Install the daemon_memcached plugin, as described in Section 14.21.3, “Setting Up the InnoDB memcached Plugin”.

4. Configure a user name and password file. (This example uses memcached simple cleartext password support.)

   1. In a file, create a user named testname and define the password as testpasswd:

      echo "testname:testpasswd:::::::" >/home/jy/memcached-sasl-db

   2. Configure the MEMCACHED_SASL_PWDB environment variable to inform memcached of the user name and password file:

      export MEMCACHED_SASL_PWDB=/home/jy/memcached-sasl-db

   3. Inform memcached that a cleartext password is used:

      echo "mech_list: plain" > /home/jy/work2/msasl/clients/memcached.conf
      export SASL_CONF_PATH=/home/jy/work2/msasl/clients

5. Enable SASL by restarting the MySQL server with the memcached -S option encoded in the daemon_memcached_option configuration parameter:

   mysqld ... --daemon_memcached_option="-S"

6. To test the setup, use an SASL-enabled client such as SASL-enabled libmemcached.

   memcp --servers=localhost:11211 --binary  --username=testname
     --password=password myfile.txt
   
   memcat --servers=localhost:11211 --binary --username=testname
     --password=password myfile.txt

   If you specify an incorrect user name or password, the operation is rejected with a memcache error AUTHENTICATION FAILURE message. In this case, examine the cleartext password set in the memcached-sasl-db file to verify that the credentials you supplied are correct.

There are other methods to test SASL authentication with memcached, but the method described above is the most straightforward.