1. System Preparation

1.1. Installing the Kerberos GSSAPI client and server utility

1.1.1. RedHat, CentOS or Scientific Linux

On RedHat, CentOS or Scientific Linux, install the Kerberos GSSAPI utilities by running the following command (as root):

$ yum install krb5-devel

1.1.2. Debian or Ubuntu

On Debian or Ubuntu, install the Kerberos GSSAPI utilities by running the following command (as root):

$ apt-get install krb5-gss-samples

2. Troubleshooting

To troubleshoot a GSSAPI connection, you require two separate terminals.

2.1. Terminal 1 - As root

1. In the first terminal, as root, run the following command:

   $ gss-server -verbose host@YOUR_HOST_NAME 

2. You should now have the following output with no prompt:

   starting...

2.2. Terminal 2 - As your test user

2.2.1. In an X environment

When you launch a terminal from X, e.g. a Gnome or KDE desktop session, the behaviour is different to a pure text environment. This is also the case when you use SSH to connect to a remote server and use display forwarding.

1. In a second terminal, as your test user, run the following command:

   $ gss-client -spnego localhost host@YOUR_HOST_NAME foo

2. You should now be prompted to select an identity in the the Moonshot Identity Selector. Choose one that will authenticate locally.

2.2.2. In a non-X environment

In a pure command-line environment with no display forwarding available, the Moonshot Identity Selector is not available. Instead, you use the .gss_eap_id file to test your environment.

1. In the second terminal, as your test user, create the .gss_eap_id file in your home directory with the following content:

   [full NAI of your identity, e.g. steve@YOUR_REALM]
   [password for the identity]

   File naming

   Double-check the file name you use. Incorrect naming of the file is a common mistake. The file name is .gss_eap_id

2. Then run the following command:

   $ gss-client -spnego localhost host@YOUR_HOST_NAME foo

2.3. GSS Output

After selecting your identity, you should now see output in both terminals.

2.3.1. Successful output

1. In Terminal 1, the output should scroll rapidly with a lot of hex text before ending with something similar to the following:

   :
   :
   73 74 80 00 00 0e 00 00 00 0c 4e fd c8 f7 af 37 
   18 bc 23 47 6a 5b 
   context flag: GSS_C_MUTUAL_FLAG
   context flag: GSS_C_REPLAY_FLAG
   context flag: GSS_C_SEQUENCE_FLAG
   context flag: GSS_C_CONF_FLAG 
   context flag: GSS_C_INTEG_FLAG 
   Accepted connection using mechanism OID { 1 3 6 1 5 5 15 1 1 17 }.
   Attribute urn:ietf:params:gss:radius-attribute 79 Authenticated Complete
   03070004
   Attribute urn:ietf:params:gss:radius-attribute 80 Authenticated Complete
   7982a7cd93fbaef973e8d6ccac5e850b
   Accepted connection: ""
   Message token (flags=228):
   05 04 02 ff 00 00 00 00 00 00 00 00 00 00 00 00 
   ef 58 6b 46 bd 60 26 d1 c1 4a 58 b0 88 91 49 34 
   2c 32 fa 93 e7 9d f2 29 e3 f8 09 e6 25 05 12 f2 
   4e c5 31 71 ba 01 94 8a cb d7 cf 73 05 87 3d 
   Received message: "foo"
   NOOP token

2. In Terminal 2, the output looks similar to the below (in this example, the hostname is debian7x64.localdomain):

   Sending init_sec_context token (size=81)...continue needed...
   Sending init_sec_context token (size=64)...continue needed...
   Sending init_sec_context token (size=261)...continue needed...
   Sending init_sec_context token (size=42)...continue needed...
   Sending init_sec_context token (size=42)...continue needed...
   Sending init_sec_context token (size=181)...continue needed...
   Sending init_sec_context token (size=169)...continue needed...
   Sending init_sec_context token (size=185)...continue needed...
   Sending init_sec_context token (size=42)...continue needed...
   Sending init_sec_context token (size=60)...continue needed...
   context flag: GSS_C_MUTUAL_FLAG
   context flag: GSS_C_REPLAY_FLAG
   context flag: GSS_C_SEQUENCE_FLAG
   context flag: GSS_C_CONF_FLAG 
   context flag: GSS_C_INTEG_FLAG 
   "steve@debian7x64.localdomain" to "host/debian7x64.localdomain", lifetime -1, flags 13e, locally initiated, open
   Name type of source name is { 1 2 840 113554 1 2 1 1 }.
   Mechanism { 1 3 6 1 5 5 2 } supports 4 names
     0: { 1 2 840 113554 1 2 1 1 }
     1: { 1 2 840 113554 1 2 1 2 }
     2: { 1 2 840 113554 1 2 1 3 }
     3: { 1 2 840 113554 1 2 1 4 }
   Signature verified.

2.3.2. Failed output

If the GSSAPI connection failed, you may see one or more errors in either window.

1. In Terminal 1, you should see one or more messages similar to the below:

   reading token flags: 0 bytes read
   reading token flags: 0 bytes read

2. In Terminal 2, you should see one or more error messages similar to the below:

   GSS-API error initializing context: Unspecified GSS failure.  Minor code may provide more information
   GSS-API error initializing context: 

Now you will need to diagnose why the error occurred.