Solaris/SEAM Kerberos 5 Vulnerability Due To Buffer Overflows In krb5_aname_to_localname()

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Impact

On Kerberos 5 enabled systems using "auth_to_local" mapping through appropriate entries in the krb5 configuration file krb5.conf(4), an unprivileged local or remote user with kerberos credentials may be able to execute arbitrary code with root privileges due to buffer overflows in "krb5_aname_to_localname()" function.

This issue is described in CERT vulnerability VU#686862 at http://www.kb.cert.org/vuls/id/686862 and MIT krb5 Security Advisory 2004-001 at http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2004-001-an_to_ln.txt.

Contributing Factors

This issue can occur in the following releases:

SPARC Platform

• Solaris 8 without patches 112237-11 and 112390-09
• Solaris 9 without patch 112908-15
• SEAM 1.0 (for Solaris 7) without patch 112536-05

x86 Platform

• Solaris 8 without patches 112240-08 and 112238-10
• Solaris 9 without patch 115168-05
• SEAM 1.0 (for Solaris 7) without patch 112537-05

Notes:

1. Systems running Solaris Enterprise Authentication Mechanism (SEAM) 1.0.1 for Solaris 8 and SEAM 1.0.2 for Solaris 9 are impacted by this issue as SEAM 1.0.1 and 1.0.2 use the affected Kerberos libraries delivered in Solaris.
2. Solaris Enterprise Authentication Mechanism (SEAM) is an unbundled product available for Solaris 7, 8 and 9. For more information on SEAM, please see the SEAM(5) man page.

For Solaris without SEAM, this issue may only occur if the system is configured to be a Kerberos client, verified by running the following command:

    % grep default_realm /etc/krb5/krb5.conf | grep -v __default_realm__
    default_realm = EXAMPLE.COM

If the command returns no output or the krb5.conf(4) file is not found, then the system is not configured for Kerberos.

In addition, systems are only vulnerable to this issue if they have been configured to enable the "explicit" mapping or "rules-based" mapping of the principal mapping functionality. This is not the default configuration. A system which is vulnerable will have one of the following entries in the krb5 configuration file (see krb5.conf(4)):

The explicit mapping form is similar to:

    auth_to_local_names = {
            aname = lname
    }

The rule-based mapping form is similar to:

    auth_to_local = RULE:foo

Symptoms

There are no predictable symptoms that would indicate the described issue has been exploited.

Workaround

To work around the described issue, disable the "auth_to_local" rules by commenting out the code for "auth_to_local" from the "/etc/krb5/krb5.conf" configuration file.

Resolution

This issue is addressed in the following releases:

SPARC Platform

• Solaris 8 with patches 112237-11 or later and 112390-09 or later
• Solaris 9 with patch 112908-16 or later
• SEAM 1.0 (for Solaris 7) with patch 112536-05 or later

x86 Platform

• Solaris 8 with patches 112240-08 or later and 112238-10 or later
• Solaris 9 with patch 115168-05 or later
• SEAM 1.0 (for Solaris 7) with patch 112537-05 or later

Note: For Solaris 8, both patches must be installed to resolve this issue.

Note: Although this issue is shown to be resolved in patch release 112908-15 (see patch README), that patch revision has been obsoleted is no longer available for download. Please use 112908-16 or later.

Modification History


Date: 30-SEP-2004

• Final patches released for Resolution; re-release as Resolved

Date: 28-SEP-2004

• Patch 112908-15 is no longer available

Date: 24-SEP-2004

• Patch 112908-15 placed temporarily on Hold

Date: 22-SEP-2004

• Patches and T-Patches added to "Contributing Factors," "Relief/Workaround," and "Resolution" sections

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