Can't access RabbitMQ web management interface after fresh install

I've installed the latest RabbitMQ server (rabbitmq-server-3.3.0-1.noarch.rpm) on a fresh Centos 5.10 VM according to the instructions on the official site.

I've done this many times before during development and never had any issues. However, this time I cannot log into the management web interface using the default guest/guest user.

In the logs, I see the following:

=ERROR REPORT==== 4-Apr-2014::00:55:15 ===
webmachine error: path="api/whoami"
"Unauthorized"

What could be causing this?

It's new features since the version 3.3.0 http://www.rabbitmq.com/release-notes/README-3.3.0.txt

server
------

...
25603 prevent access using the default guest/guest credentials except via
      localhost.

If you want enable the guest user read this or this RabbitMQ 3.3.1 can not login with guest/guest

# remove guest from loopback_users in rabbitmq.config like this
[{rabbit, [{loopback_users, []}]}].
# It is danger for default user and default password for remote access
# better to change password 
rabbitmqctl  change_password guest NEWPASSWORD

If you want create a new user with admin grants:

rabbitmqctl add_user test test
rabbitmqctl set_user_tags test administrator
rabbitmqctl set_permissions -p / test ".*" ".*" ".*"

Now you can access using test test.

If you still can't access the management console after a fresh install, check if the management console was enabled. To enable it:

1. Go to the RabbitMQ command prompt.

2. Type:

   rabbitmq-plugins enable rabbitmq_management
   

Something that just happened to me and caused me some headaches:

I have set up a new Linux RabbitMQ server and used a shell script to set up my own custom users (not guest!).

The script had several of those "code" blocks:

rabbitmqctl add_user test test
rabbitmqctl set_user_tags test administrator
rabbitmqctl set_permissions -p / test ".*" ".*" ".*"

Very similar to the one in Gabriele's answer, so I take his code and don't need to redact passwords.

Still I was not able to log in in the management console. Then I noticed that I had created the setup script in Windows (CR+LF line ending) and converted the file to Linux (LF only), then reran the setup script on my Linux server.

... and was still not able to log in, because it took another 15 minutes until I realized that calling add_user over and over again would not fix the broken passwords (which probably ended with a CR character). I had to call change_password for every user to fix my earlier mistake:

rabbitmqctl change_password test test

(Another solution would have been to delete all users and then call the script again)