This guide contains advanced configuration information for system administrators working with GSI-OpenSSH. It provides references to information on procedures typically performed by system administrators, including installation, configuring, deploying, and testing the installation.
This information is in addition to the basic Globus Toolkit prerequisite, overview, installation, security configuration instructions in Installing GT 5.0.5. Read through this guide before continuing!
This guide is meant solely to cover the GSI aspects of GSI-OpenSSH, and is not meant to be a full manual for OpenSSH itself. Please refer to the OpenSSH Home Page for general documentation for OpenSSH.
Table of Contents
- 1. Building and Installing
- 2. Configuring
- 3. Deploying
- 4. Testing
- 5. Security Considerations
- 6. Debugging
- 7. Troubleshooting
- 8. Usage statistics collection
GSI-OpenSSH is built and installed as part of a default GT 5.0.5 installation. For basic installation instructions, see Installing GT 5.0.5. No extra installation steps are required for this component.
You can optionally pass build-time configure options to the GSI-OpenSSH package using the --with-gsiopensshargs option when running configure for your GT 5.0.5 installation. For example:
./configure --prefix=$HOME/globus --with-gsiopensshargs="--with-pam"
No options are typically needed for client-only installations, but options are often needed for full server functionality. The following table lists suggested options for different platforms.
Table 1.1. GSI-OpenSSH build arguments
|Linux||--with-pam --with-md5-passwords --with-tcp-wrappers|
|Solaris||--with-pam --with-md5-passwords --with-tcp-wrappers|
Note: If you enable PAM support with the --with-pam configuration option, be sure to also set "UsePAM yes" in $GLOBUS_LOCATION/etc/ssh/sshd_config after installation.
If you have an already configured and installed system-wide SSHD and you would like your build of GSI-OpenSSH to behave similarly, investigate the configure options available in GSI-OpenSSH and select those options that would add the functionality that your current SSHD possesses. Be aware that since GSI-OpenSSH is based on OpenSSH, the standard set of functionality is turned on by default.
Please do not attempt to override the following options:
--prefix --sysconfdir --with-globus --with-globus-flavor --with-ssl-dir
If you wish to install GSI-OpenSSH without installing the rest of the Globus Toolkit, follow the instructions in Installing GT 5.0.5 with the following changes. First, you do not need Ant, a JDK, or a JDBC database to build only GSI-OpenSSH. Second, instead of running "make", run:
globus$ make gsi-openssh
This will install the GSI-OpenSSH client and server programs. For client-only installations, simply do not configure or use the installed server.
The GSI-enabled OpenSSH software is installed with a default set of
configuration files, described below.
You may want to modify the
ssh_config file before using the
clients and the
sshd_config file before using the server.
If the GSI-enabled OpenSSH install script finds existing SSH key pairs, it will create symbolic links to them rather than generating new key pairs. The SSH key pairs are not required for GSI authentication. However, if you wish to support other SSH authentication methods, make sure the sshd (running as root) can read the key pair files (i.e., beware of NFS mounts with root_squash). If running multiple sshds on a system, we recommend configuring them so they all use the same key pairs (i.e., use symbolic links) to avoid client-side confusion.
moduli is a crypto parameter for generating keys.
ssh_config contains options that are read by ssh, scp, and sftp at run-time. The installed version is the default provided by OpenSSH, with GSI authentication and X11Forwarding enabled. You may need to customize this file for compatibility with your system SSH installation (i.e., compare it with /etc/ssh/ssh_config).
Your system's RSA public-/private-key pair for SSH protocol 1 communications.
Your system's DSA public-/private-key pair for SSH protocol 2 communications.
Your system's RSA public-/private-key pair for SSH protocol 2 communications.
ssh_prng_cmds contains paths to a number of files that ssh-keygen may need to use if your system does not have a built-in entropy pool (like /dev/random).
sshd_config contains options that are read by sshd when it starts up. The installed version is the default provided by OpenSSH, with X11Forwarding enabled. You may need to customize this file for compatibility with your system SSH installation (i.e., compare it with /etc/ssh/sshd_config). For example, to enable PAM authentication, you may need to set "UsePAM yes" in this file.
To install the GSI-Enabled OpenSSH Server on most systems, you must be a privileged user, such as root.
sh$ /bin/su - root
Note: If your system functions like this and you attempt to run these commands as a user other than root, these commands should fail.
(optional) Start a copy of your system's currently running SSH server on an alternate port by running, eg.
sh# /usr/sbin/sshd -p 2000 &
You may then choose to log in to this server and continue the rest of these steps from that shell. We recommend doing this since some sshd shutdown scripts do particularly nasty things like killing all of the running SSH servers on a system, not just the parent server that may be listening on port 22. Roughly translated, this step is about guaranteeing that an alternate method of access is available should the main SSH server be shutdown and your connection via that server be terminated.
Locate your server's startup/shutdown script directory. On some systems this directory may be located at /etc/rc.d/init.d, but since this location is not constant across operating systems, for the purposes of this document we will refer to this directory as INITDIR. Consult your operating system's documentation for your system's location.
Run the following command.
sh# mv $INITDIR/sshd $INITDIR/sshd.bak
Either copy or link the new sshd script to your system's startup/shutdown script directory.
sh# cp $GLOBUS_LOCATION/sbin/SXXsshd $INITDIR/sshd
Shutdown the currently running main SSH server.
sh# $INITDIR/sshd.bak stop
Provided you still have a connection to the machine, start the new SSH server.
sh# $INITDIR/sshd start
Test the new server by connecting to the standard SSH port (22) and authenticating via multiple methods. Especially test that GSI authentication works correctly.
If you are performing a new install, or if the old server was not configured to be started at run-time and shutdown automatically at system halt or reboot, either use a system utility such as RedHat's chkconfig to configure the system for the correct run-levels, or manually link up the correct run-levels.
sh# /sbin/chkconfig sshd reset
The recommended run-levels are listed in a set of comments within the SXXsshd startup script. For example, on standard Unix systems we recommend running the GSI-Enabled OpenSSH server in run-levels two, three, four, and five.
Finally, if, as a precautionary measure, you started a SSH server on an alternate port in order to complete the install process, you can now safely stop all instances of that server.
Edit the file $GLOBUS_LOCATION/sbin/SXXsshd so that the GSI-Enabled OpenSSH server starts up on an alternate port.
Run the command
sh# $GLOBUS_LOCATION/sbin/SXXsshd start
and verify that the server is running by checking that it both shows up in a process listing and creates a file named $GLOBUS_LOCATION/var/sshd.pid.
From a remote machine attempt to connect to the local server on the modified test port using the standard SSH authentication methods plus authenticating via your GSI credentials. This may require you to authorize these users via an appropriate entry in the grid-mapfile.
Stop the SSH server by running the command
sh# $GLOBUS_LOCATION/sbin/SXXsshd stop
and reverse any changes you made that altered the port on which the server resided upon startup. After this step, running SXXsshd start should start the server on the default port (22).
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The GSI-OpenSSH server logs to the system logger (syslog). Log messages from OpenSSH are unmodified in GSI-OpenSSH. GSI-specific log messages include:
failed to map GSI user DN GSI user DN mapped to target user username GSI user DN is authorized as target user username GSI user DN is not authorized as target user username
In the messages above, DN is replaced with the client certificate subject distinguished name, and username is replaced with the local Unix username.
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