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TUCoPS :: Unix :: General :: ciaci088.txt

NFS Clients Rpg Pcnfsd Vulnerabilities


                       The U.S. Department of Energy
                    Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___

                             INFORMATION BULLETIN

                     NFS clients rpc.pcnfsd Vulnerabilities

August 20, 1998 21:00 GMT                                         Number I-088
PROBLEM:       Two vulnerabilities have been identified in pcnfsd, a Remote
               Procedure Call used by NFS clients.
PLATFORM:      Platforms running rpc.pcnfsd:
                 AIX: 4.0, 4.1, 4.2, 4.3
                 HP-UX: 7.x, 8.x, 9.x, 10.x, 11.x
                 SunOS: 4.1.3, 4.1.4
                 Solaris: 2.3, 2.4, 2.5, 2.5.1, 2.6
                 Redhat Linux: 4.0, 4.1, 4.2, 5.0, 5.1
                 Slackware Linux: 3.0, 3.1, 3.2, 3.3, 3.4, 3.5
                 OSF: 3.2
DAMAGE:        If exploited, an attacker could gain root access.
SOLUTION:      Apply patches or workarounds.
VULNERABILITY  If you are using rpc.pcnfsd, you should implement the
ASSESSMENT:    workarounds or patches on all vulnerable systems as soon as

[ Start RSI Advisory ]


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                   Repent Security Incorporated, RSI
                       [ ]

                       *** RSI ALERT ADVISORY ***

- --- [CREDIT] --------------------------------------------------------------

'Bermuda Brian': Research and development
Mark Zielinski : Author of advisory

- --- [SUMMARY] -------------------------------------------------------------

Announced:     July 14, 1998
Report code:   RSI.0008.08-18-98.ALL.RPC_PCNFSD
Report title:  All rpc.pcnfsd
Vulnerability: Please see the details section
Vendor status: IBM contacted on August 3, 1998
               Hewlett Packard contacted on August 3, 1998
               Sun Microsystems contacted on August 3, 1998
               Slackware contacted on August 3, 1998
Patch status:  Linux and AIX patch information is provided below
Platforms:     Vulnerable:

               AIX: 4.0, 4.1, 4.2, 4.3
               HP-UX: 7.x, 8.x, 9.x, 10.x, 11.x
               SunOS: 4.1.3, 4.1.4
               Solaris: 2.3, 2.4, 2.5, 2.5.1, 2.6
               Redhat Linux: 4.0, 4.1, 4.2, 5.0, 5.1
               Slackware Linux: 3.0, 3.1, 3.2, 3.3, 3.4, 3.5
               OSF: 3.2

               Not vulnerable:

               OpenBSD, FreeBSD, NetBSD, BSDI

Impact:        If exploited, an attacker could potentially compromise
               root access both locally and remotely on your server

- --- [DETAILS] -------------------------------------------------------------

Description:   PCNFSD is a Remote Procedure Call used by NFS clients.
               This service provides username and password authentication
               for networked computers which have installed NFS client

Problem:       Two vulnerabilities are covered in this advisory which
               both allow root access to be compromised.

               Vulnerable functions:
               A. pr_init ()    : [CIAC HAS CHOSEN NOT TO INCLUDE FURTHER 
                                   DETAILS RE THIS VULNERABILITY]

               B. run_ps630 ()  : [CIAC HAS CHOSEN NOT TO INCLUDE FURTHER 
                                   DETAILS RE THIS VULNERABILITY]
               * Note           : AIX is not vulnerable to problem A,
                                  and HP is only vulnerable to function
                                  A in HP-UX 9.0, 10.0.

- --- [FIX] -----------------------------------------------------------------

Solution:      Disable rpc.pcnfsd until an appropriate patch is
               released for your operating system.

- --- [AIX PATCH] -----------------------------------------------------------

               AIX users: IBM has provided the following patches in
               reponse to this vulnerability:

               APAR 4.1.x: IX81505
               APAR 4.2.x: IX81506
               APAR 4.3.x: IX81507

               Until the official APARs are available, a temporary
               fix can be downloaded via anonymous ftp from:


- --- [LINUX PATCH] ---------------------------------------------------------

Solution:      Working in conjunction with Patrick Volkerding and the
               Slackware Linux development staff, RSI has produced the
               following patches:


               WARNING! The code quoted below is only fragments of each
               patch! You must download each patch for it to work correctly.

               0008.patch1 replaces the character set that is considered
               suspicious and replaces it with a list of characters that
               are allowed. The following two lines show the change:


- -       if(strpbrk(s, ";|&<>`'#!?*()[]^/") != NULL)


+       if (strspn(s, "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-




               0008.patch2 replaces the vulnerable code by removing the
               chmod call, and utilizing umask. The following code fragments
               have been stripped out of the patch to show the vulnerable
               pieces of code and the relevant fix.


+        oldumask = umask(0);
+        (void)sprintf(pathname,"%s/%s",sp_name, sys);
+        (void)mkdir(sp_name, dir_mode); /* ignore the return code */
+        rc = mkdir(pathname, dir_mode); /* DON'T ignore this return code */
+        umask(oldumask);


- -       (void)chmod(sp_name, dir_mode);
        if((rc < 0 && errno != EEXIST) ||
- -          (chmod(pathname, dir_mode) != 0) ||
           (stat(pathname, &statbuf) != 0) ||
           !(statbuf.st_mode & S_IFDIR)) {

- --- [OTHER PATCHES] -------------------------------------------------------

               SunOS, Solaris, HPUX, and OSF users should wait
               for their respective vendor to provide a patch.

- ---------------------------------------------------------------------------

Repent Security Incorporated (RSI)
13610 N. Scottsdale Rd.
Suite #10-326
Scottsdale, AZ 85254


[End RSI Advisory ]

CIAC wishes to acknowledge the contributions of Repent Security Incorporated
(RSI) for the information contained in this bulletin.

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