Features/KRB5CacheMove

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<!-- A sentence or two summarizing what this feature is and what it will do.  This information is used for the overall feature summary page for each release. -->
 
<!-- A sentence or two summarizing what this feature is and what it will do.  This information is used for the overall feature summary page for each release. -->
  
This Feature changes the default location of Kerberos credential cache from living in /tmp/krb5cc_UID_XXXXXX to being /run/user/$USERNAME/krb5cc
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This Feature changes the default location of Kerberos credential cache from living in /tmp/krb5cc_UID_XXXXXX to being /run/user/$UID/krb5cc
  
 
== Owner ==
 
== Owner ==
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== Current status ==
 
== Current status ==
 
* Targeted release: Fedora 18
 
* Targeted release: Fedora 18
* Last updated: 2012-02-23
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* Last updated: 2012-06-15
* Percentage of completion: 10%
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* Percentage of completion: 75%
  
 
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opposed to just server that accept kerberos connections), it may be
 
opposed to just server that accept kerberos connections), it may be
 
needed to add a configuration snippet in their configuration file
 
needed to add a configuration snippet in their configuration file
under /etc/tmpfiles.d so that /run/user/<username> is created with the
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under /etc/tmpfiles.d so that /run/user/$UID is created with the
 
correct permissions (700) and user ownership.
 
correct permissions (700) and user ownership.
  
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the /etc/tmpfiles.d/httpd.conf:
 
the /etc/tmpfiles.d/httpd.conf:
  
d /var/run/user/apache   700 apache apache
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d /var/run/user/48   700 apache apache
  
 
If you know your daemon requires a credential cache file and does not
 
If you know your daemon requires a credential cache file and does not
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-->
 
-->
  
1. Verify that when logging in through SSSD or pam_krb5 that the credential cache listed by 'klist' is FILE:/run/user/$USERNAME/krb5cc
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1. Verify that when logging in through SSSD or pam_krb5 that the credential cache listed by 'klist' is FILE:/run/user/$UID/krb5cc
2. Verify that applications such as apache (used with mod-auth_kerb) put their credential caches in /run/user/$SVCUSERNAME as well
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== User Experience ==
 
== User Experience ==
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opposed to just server that accept kerberos connections), it may be
 
opposed to just server that accept kerberos connections), it may be
 
needed to add a configuration snipppet in their configuration file
 
needed to add a configuration snipppet in their configuration file
under /etc/tmpfiles.d so that /run/user/<username> is created with the
+
under /etc/tmpfiles.d so that /run/user/$UID is created with the
 
correct permissions (700) and user ownership.
 
correct permissions (700) and user ownership.
  
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the /etc/tmpfiles.d/httpd.conf:
 
the /etc/tmpfiles.d/httpd.conf:
  
d /var/run/user/apache   700 apache apache
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d /var/run/user/48   700 apache apache
  
  
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<!-- The Fedora Release Notes inform end-users about what is new in the release.  Examples of past release notes are here: http://docs.fedoraproject.org/release-notes/ -->
 
<!-- The release notes also help users know how to deal with platform changes such as ABIs/APIs, configuration or data file formats, or upgrade concerns.  If there are any such changes involved in this feature, indicate them here.  You can also link to upstream documentation if it satisfies this need.  This information forms the basis of the release notes edited by the documentation team and shipped with the release. -->
 
<!-- The release notes also help users know how to deal with platform changes such as ABIs/APIs, configuration or data file formats, or upgrade concerns.  If there are any such changes involved in this feature, indicate them here.  You can also link to upstream documentation if it satisfies this need.  This information forms the basis of the release notes edited by the documentation team and shipped with the release. -->
* Fedora 18 changes the standard location of Kerberos credential caches to /run/user/$USERNAME in order to increase security and simplify locating the caches for NFSv4.
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* Fedora 18 changes the standard location of Kerberos credential caches to /run/user/$UID in order to increase security and simplify locating the caches for NFSv4.
  
 
== Comments and Discussion ==
 
== Comments and Discussion ==

Revision as of 18:26, 15 June 2012


Contents

KRB5 Credential Cache Move

Summary

This Feature changes the default location of Kerberos credential cache from living in /tmp/krb5cc_UID_XXXXXX to being /run/user/$UID/krb5cc

Owner

Current status

  • Targeted release: Fedora 18
  • Last updated: 2012-06-15
  • Percentage of completion: 75%


Detailed Description

Packages that create Kerberos credential caches on behalf of a user (real or system) will need to change where this cache is stored.

Benefit to Fedora

The reason is to make credential saving a bit more predictable while at the same time avoiding races. Along the road we also gain a little bit more security by the fact that /run is a tmpfs and therefore cached credentials are automatically removed if the machine is shut off.


Scope

For daemons that use a keytab to kinit because they act as clients (as opposed to just server that accept kerberos connections), it may be needed to add a configuration snippet in their configuration file under /etc/tmpfiles.d so that /run/user/$UID is created with the correct permissions (700) and user ownership.

For example, httpd would add the following line to the /etc/tmpfiles.d/httpd.conf:

d /var/run/user/48 700 apache apache

If you know your daemon requires a credential cache file and does not specify one on its own but instead relies on the default location, then you should open a ticket in bugzilla and add the necessary configuration to tmpfiles.d

How To Test

1. Verify that when logging in through SSSD or pam_krb5 that the credential cache listed by 'klist' is FILE:/run/user/$UID/krb5cc

User Experience

The end-user experience should be minimally changed. The most noticable effect will be that credential caches will not survive a reboot (this is a security enhancement, preventing a stolen system from being accessed for still-valid credentials).

Dependencies

This list is not (yet) complete:

  • sssd
  • pam_krb5
  • mod_auth_kerb
  • sshd
  • nfs-utls
  • kstart


For daemons that use a keytab to kinit because they act as clients (as opposed to just server that accept kerberos connections), it may be needed to add a configuration snipppet in their configuration file under /etc/tmpfiles.d so that /run/user/$UID is created with the correct permissions (700) and user ownership.

For example, httpd would add the following line to the /etc/tmpfiles.d/httpd.conf:

d /var/run/user/48 700 apache apache


Some other daemons (such as rpc.gssd and sshd) have hard-coded /tmp locations and will require patching to complete this transition.

We are still investigating which packages require changes.

Contingency Plan

Reverting to the original behavior will be possible, though non-trivial. Our current plan is to land this feature very early in the F18 process (some pieces are already landing today on 2012-02-23) so that we have the maximum amount of time to work out any issues.

Documentation

  • No relevant documentation

Release Notes

  • Fedora 18 changes the standard location of Kerberos credential caches to /run/user/$UID in order to increase security and simplify locating the caches for NFSv4.

Comments and Discussion