Difference between revisions of "GLExec"

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* [[Service Reference Card for gLExec]]
 
* [[Service Reference Card for gLExec]]
 
* [[Papers about gLExec]]
 
* [[Papers about gLExec]]
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= Deploying gLExec on the worker node =
 
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== Need to Know's ==
 
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The gLExec executable is installable in two ways, with an without the setuid (file system) bit on root. With the setuid-bit enabled on root, this effectively means that gLExec is being executed with root privileges. Without the setuid or setgid bits on root the gLExec executable is like any other regular executable.
 
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The safety features of gLExec are implemented with great care to avoid misuse and exploitation by anybody who executes it. As gLExec is typically installed with a setuid bit on root, this effectively means that anybody on the system is able to execute something with root privileges for a brief moment of time to perform the user switch.
 
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A couple of safety features that are build in the gLExec tool are:
 
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* The LD_LIBRARY_PATH, LD_RUN_PATH and other LD_* environment variables are removed from the process environment by the Operating System before the first line of gLExec code is executed by a Unix and Linux system. Only the /etc/ld.so.conf{.d/}, RPATH settings and other system specific paths are used and resolved. This statement holds for '''any''' setuid or setgid executable.
 
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* The rest of the environment is stripped off by gLExec. There are a couple of environment settings that can easily lead to a root exploit in the standard library of a Unix and Linux system. Only the GLEXEC_* environment variables are kept. There is an option in the glexec.conf file to preserve more variables, but these must be selected with great care and setup by each System Administrator on all their machines.
 
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* If the target user is authorized and when a mapping and Unix process identity switch the HOME and X509_USER_PROXY will be rewritten. Their value will contain the paths that are relevant for the target user account.
 
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* The target user process has the Unix identity as mapped by LCMAPS. This could be from a separate set of pool accounts, or the regular set of pool accounts as given by the same user credentials from an LCG-CE or CREAM-CE. It could be a poolaccount defined locally on the machine. The only assumption that holds is that the target user account has the privileges that are appointed to them by the local site administrator.
 

Revision as of 07:48, 5 February 2010

gLExec is a program that acts as a light-weight 'gatekeeper'. gLExec takes Grid credentials as input. By taking the local site policy into account it authenticates and authorizes the credentials. For extra safety gLExec is capable of creating a new execution sandbox based on the Grid credentials. Besides the yes/no control point functionality in the logging-only mode it can create identity specific sandboxes in the identity-switching mode.

Deployment: Installation and setups

How To's and FAQ

  • To help you master gLExec's security:
    • Need to Know's: Explains about the LD_LIBRARY_PATH in combo with setuid programs and other technical details.
    • GLExec TransientPilotJobs describes how you may go about managing a target workload's transient area in Pilot Job Frameworks.
    • GLExec Environment Wrap and Unwrap scripts describes how you can preserve the environment variables between the calling process of gLExec and the user switched side of gLExec. For example: to preserve the environment variables from a Pilot Job Framework, through gLExec and into Pilot Job Payload.

Online documentation (on other sites)

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