Security continues to be a focus for us, and we've made some additional strides in admin security for GlassFish 3.1.2, now available for download. The documentation (especially the security guide) does a very good job explaining this, so I'll just summarize a few things here. (You can read about some significant improvements we made in GlassFish 3.1.1 in this earlier post if you are not familiar with them.)
Sometimes the domain admin server (the DAS) needs to send admin messages to other instances in the domain. Beginning with GlassFish 3.1.2 that traffic is always secured using SSL encryption. Further, the instances authenticate the DAS - they make sure the DAS is who it claims to be - also using the SSL certificate. This is true whether or not you explicitly enable or disable secure admin.
Because DAS-to-instance traffic is always secured in GlassFish 3.1.2, enabling and disabling secure admin will control only whether you allow the DAS to accept remote admin requests.
Note that GlassFish 3.1.2 will not let you enable secure admin if you have any admin accounts with an empty password. So, if you want to enable secure admin for an out-of-the-box installation you'll need to do this first:
and respond to the prompts for the "admin" username.
GlassFish now always uses SSL encryption for the DAS-to-instance traffic simply to be more secure. The DAS does not typically have to send many commands to instances, so any performance penalty from using SSL on those messages is very small. Especially if you have the DAS and instances running on different hosts this more secure approach is much better.
We imposed the additional requirement on enable-secure-admin - requiring all admin users to have non-empty passwords - to help you protect your GlassFish domain. This change prevents anyone from another
system from sending admin requests to your GlassFish domain using the
default, out-of-the-box admin username and password. (And, no, the change-admin-password command will not let you set an empty admin password if secure admin is already enabled!)
As I noted in the earlier 3.1.1 posts about secure admin, there can be a tension between ease-of-use and security. If you are accustomed to installing a new version of GlassFish, enabling secure admin, and then accessing it from other systems - including from an IDE - you might find it annoying to have to change the default admin password to a non-empty value before you can enable secure admin. But the enable-secure-admin command will remind you about the admin password if you haven't already changed it. And once you change the password and enable secure admin you'll be able to sleep better at night. Well, at least you should not be restless because of GlassFish admin security.