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Remote Root Exploitation of Default Solaris sadmind Setting

09.16.03

BACKGROUND

Solstice AdminSuite is a set of tools packaged by Sun Microsystems Inc. in its Solaris operating system to help administrators manage systems remotely, centralize configuration information and monitor software usage. The sadmind daemon is used by Solstice AdminSuite applications to perform these distributed system administration operations. The sadmind daemon is typically installed and enabled in a default Solaris installation.

DESCRIPTION

An exploit has surfaced that allows remote attackers to execute arbitrary commands with super-user privileges against Solaris hosts running the default RPC authentication scheme in Solstice AdminSuite. This weakness is documented to some extent in Sun documentation, http://docs.sun.com/db/doc/816-0211/6m6nc676b?a=view .

By sending a sequence of specially crafted Remote Procedure Call (RPC) requests to the sadmind daemon, an attacker can exploit this vulnerability to gain unauthorized root access to a vulnerable system. The sadmind daemon defaults to weak authentication (AUTH_SYS), making it possible for a remote attacker to send a sequence of specially crafted RPC packets to forge the client identity.

After the identity has been successfully forged, the attacker can invoke a feature within the daemon itself to execute a shell as root or, depending on the forged credential, any other valid user of the system. The daemon will execute the program of the attacker's choice; for example, spawning a reverse-network shell back to the attacker for input/output control. Under certain circumstances, a reverse-network shell could allow the attacker to bypass firewalls and/or filters.

ANALYSIS

Because the nature of the weakness exists on the application level, successful exploitation does not require the use of machine-specific code, nor does it require any previous knowledge of the target's architecture. Therefore, any local or remote attacker could execute commands as root on a vulnerable system running the sadmind service. By default, sadmind is installed and started at system boot time on most default and fully patched installations of Solaris. While many other vendors rely on SUNRPC related routines from Sun, this design issue is confined to Sun's sadmind authentication implementation in Solaris. The most inherent threat is if this exploit becomes packaged into a cross-platform worm was it to become publicly available.

DETECTION

An exploit has been obtained and demonstrated in real-world conditions on systems running Solaris or Trusted Solaris operating systems running sadmind. Default installations of SunOS 5.3 thru 5.9 (Solaris 2.x, 7, 8, 9) on both the SPARC and _x86 platforms are susceptible. In addition, versions 7 and 8 of Trusted Solaris on both the SPARC and _x86 platforms are susceptible to exploitation. Exploitation occurs through an initial request through UDP or TCP port 111 (sunrpc).

WORKAROUND

S

For Solaris hosts that do not require the Solstice AdminSuite related services, disable the sadmind service by commenting out the appropriate line in /etc/inetd.conf. Make sure to restart inetd after changing this file (e.g. pkill -HUP inetd).
For networks, ensure proper ingress filters are in place on the Internet router and firewall, especially on TCP and UDP port 111.

For Solaris hosts that require the Solstice AdminSuite to be running, the authentication security settings of sadmind should be increased to STRONG (AUTH_DES) — this is not the default setting. This setting also requires the creation of NIS or NIS+ DES keys to have been created for each Solaris user and each host.

In order to upgrade the authentication setting, the sadmind line in /etc/inetd.conf should be changed to look like the following:

100232/10 tli rpc/udp wait root /usr/sbin/sadmind sadmind -S 2

Sun also recommends using the Solaris Security Toolkit (JASS) to harden a Solaris system, http://wwws.sun.com/software/security/jass/.

VENDOR RESPONSE

Sun does not plan to release a patch for this issue. Because a working exploit now exists for this issue, Sun Microsystems Inc. is issuing Alert 56740 to ensure administrators have proactively applied the proper workarounds in the event this exploit or one like it becomes publicly available. Sun's alert is available at http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsalert%2F56740.

CVE INFORMATION

The Mitre Corp.'s Common Vulnerabilities and Exposures (CVE) Project has assigned CAN-2003-0722 to this issue.

CREDIT

Mark Zielinski (markzielinski@mailblocks.com) is credited with this discovery.