A Security Vulnerability in Solaris Kerberos Credential Management May Lead to Unauthorized Access of Kerberized NFS Mount Points

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A Security Vulnerability in Solaris Kerberos Credential Management May Lead to Unauthorized Access of Kerberized NFS Mount Points

1. Impact

A security vulnerability in the Solaris Kerberos (see kerberos(5)) credential cache management may allow a local unprivileged user to access Kerberized mount points without authorization.

Sun acknowledges with thanks, Anton Lundin for bringing this issue to our attention.

2. Contributing Factors

This issue can occur in the following releases:

SPARC Platform

• Solaris 8 without patch 140841-01
• Solaris 9 without patch 112908-34
• Solaris 10 without patch 140074-05
• OpenSolaris based upon build snv_01 through snv_116
  

x86 Platform

• Solaris 8 without patch 140842-01
• Solaris 9 without patch 115168-19
• Solaris 10 without patch 140130-06
• OpenSolaris based upon build snv_01 through snv_116

Notes:

1. Solaris 8 entered EOSL Phase 2 on 1 April 2009. Entitlement to patches developed on or after 1 April 2009 requires the purchase of the Solaris 8 Vintage Patch Service. See note in section 5 for more details.

2. OpenSolaris distributions may include additional bug fixes above and beyond the build from which it was derived. The base build can be derived as follows:

$ uname -v
snv_101 

3. This issue could affect all systems utilizing Kerberized NFS mount points as an NFS client.  To determine if a system could be exposed to this issue, the following command can be run:

$ nfsstat -m | grep sec=krb

If any data is returned, the system may be vulnerable to this issue.

3. Symptoms

This issue exists on all systems utilizing Kerberized NFS mount points.  There are no predictable symptoms that would indicate this issue has been exploited to gain unauthorized access to Kerberized NFS shares.

4. Workaround

There is no workaround that would prevent unauthorized access to affected shares. It may be desirable therefore to modify the share and mount options so that they no longer utilize Kerberos. This can be done by editing of the dfstab(4) file on the NFS server and removing the 'sec=' option.

Alternatively, the unshare(1) command can be used to unshare the filesystem, and the share(1) command to share the filesystem, not specifying the 'sec=' option.  The client systems could then umount(1) the filesystem and then mount(1) with no 'sec=' option.  This will allow UNIX system permissions to  safeguard against unauthorized access.

Note: As this workaround disables Kerberos for the affected NFS shares, the security of those shares may be impacted in various ways depending on the configuration. For example, network traffic associated with those shares may no longer be encrypted during transfer, and the access permissions will revert to those supported by the standard UNIX permissions implementation.

5. Resolution

This issue is addressed in the following releases:

SPARC Platform

• Solaris 8 with patch 140841-01 or later
  
• Solaris 9 with patch 112908-34 or later
• Solaris 10 with patch 140074-05 or later
• OpenSolaris based upon build snv_117 or later
  

x86 Platform

• Solaris 8 with patch 140842-01 or later
• Solaris 9 with patch 115168-19 or later
• Solaris 10 with patch 140130-06 or later
• OpenSolaris based upon build snv_117 or later
  

Note 1: During installation of the resolution for Solaris 10 or OpenSolaris, the "inetd_start/privileges" property of the SMF service "svc:/network/rpc/gss" will be modified. If, however, this property has already been customized after the initial installation of the service (for example by using the "svccfg setprop" command), this customized value will be retained and the setting that is included in the resolution will not be applied. This means the resolution for this security issue will not be complete.

If this issue has occurred, messages such as the following will be seen in the patch install log (for example "/var/sadm/patch/140074-05/log") after installation of the patch, or in the manifest import service's log files "/var/svc/log/system-manifest-import:default.log" or "/etc/svc/volatile/system-manifest-import:default.log":


To work around this issue, the customized version of the service can be deleted and replaced with the version from the resolution using commands such as the following:

# svcadm disable svc:/network/rpc/gss:default

# svccfg delete svc:/network/rpc/gss

# svccfg import /var/svc/manifest/network/rpc/gss.xml

# svcadm enable svc:/network/rpc/gss:default

This issue does not apply to the Solaris 8 and 9 resolutions as they do not use SMF.

Note 2: The READMEs of Solaris 8 patches developed on or after 1 April 2009 are available to all customers. However, Solaris 8 entered EOSL Phase 2 on April 1, 2009 and thus entitlement for these patches, including those that fix security vulnerabilities, requires the purchase of the Solaris 8 Vintage Patch Service. More information about the Solaris 8 Vintage Patch Service is available at: 

http://www.sun.com/service/eosl/Solaris8.html

For more information on Security Sun Alerts, see Technical Instruction ID 213557.

This Sun Alert notification is being provided to you on an "AS IS" basis. This Sun Alert notification may contain information provided by third parties. The issues described in this Sun Alert notification may or may not impact your system(s). Sun makes no representations, warranties, or guarantees as to the information contained herein. ANY AND ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT, ARE HEREBY DISCLAIMED. BY ACCESSING THIS DOCUMENT YOU ACKNOWLEDGE THAT SUN SHALL IN NO EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, PUNITIVE, OR CONSEQUENTIAL DAMAGES THAT ARISE OUT OF YOUR USE OR FAILURE TO USE THE INFORMATION CONTAINED HEREIN. This Sun Alert notification contains Sun proprietary and confidential information. It is being provided to you pursuant to the provisions of your agreement to purchase services from Sun, or, if you do not have such an agreement, the Sun.com Terms of Use. This Sun Alert notification may only be used for the purposes contemplated by these agreements.

Copyright 2000-2009 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, CA 95054 U.S.A. All rights reserved.


Modification History

29-Jul-2009: Updated Resolution section

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