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SASLHowto

dormando edited this page Mar 28, 2018 · 3 revisions

Introduction

If running memcached in a mostly trusted network; such as within a cloud or a corporate internal cloud, you might want to restrict access to the service.

SASL is not implemented as end-to-end encryption. While this can facilitate restricting access to the daemon, it does not hide communications and isn't suitable for using over the internet.

SASL (as described in RFC2222) is a standard for adding authentication mechanisms to protocols in a way that is protocol independent.

Getting Started

In order to deploy memcached with SASL, you'll need two things:

  • A memcached server with SASL support (version 1.4.3 or greater built with --enable-sasl)
  • A client that supports SASL
    • The server side has to support the authentication mechanism the client is using, some clients only support plain while an OS may not provide a library/package that supports plain, at least not by default.

Configuring SASL

For the most part, you just do the normal SASL admin stuff.

# Create a user for memcached.
saslpasswd2 -a memcached -c cacheuser

Running Memcached

In order to enable SASL support in the server you must use the -S flag.

The -S flag does a few things things:

  • Enable all of the SASL commands.
  • Require binary protocol only.
  • Require authentication to have been successful before commands may be issued on a connection.

SASL how to FAQ

Q.) How can I check if the memcached server I have is built with SASL support?

  • A.) You can see if the command line help lists the option:
      -S, --enable-sasl         turn on Sasl authentication
  • A.) You can run the server in verbose mode, for example:
      > memcached -S -vvvv 
      Reading configuration from: <...memcached.conf>
      Initialized SASL.
  • A.) On Linux you can check if it links against a SASL library, for example:
      > ldd `which memcached` | grep -i sasl
      libsasl2.so.3 => /lib64/libsasl2.so.3 

Q.) The configure option --enable-sasl-pwdb is not working

Q.) Plain auth is not working, why not?

  • A.) Does running memcached with the -vvvv option provide any useful messages?
  • A.) Check you have the SASL lib that implements it installed, for example /usr/lib64/sasl2/libplain.so provided by the RPM cyrus-sasl-plain.
  • A.) Check the password file is owned by and only readable by the user running memcached.
  • A.) Check that the username the client is using matches that used in the password file, note that sometimes the client hostname is postfixed to the username with an @, so myname@client_hostname:mypass

Further Info

Read more about memcached's SASL auth protocol. https://github.com/memcached/memcached/wiki/ReleaseNotes145#sasl_pwdb-for-more-simple-auth-deployments

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