__________________________________________________________ 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 possible. ______________________________________________________________________________ [ Start RSI Advisory ] RSI.0008.08-18-98.ALL.RPC_PCNFSD |:::. |::::: |::::. |::::: |::::: |::::. .. :: .. .. :: .. .. .. :: |:::: |:::: |:::: :::::: |::::: |:::: |: |: :: |: |: |:: |: |: :: |: :: |::::: |: |::::: |::::: |::::: Repent Security Incorporated, RSI [ http://www.repsec.com ] *** 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 Reference: http://www.repsec.com/advisories.html 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 software. 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: ftp://aix.software.ibm.com/aix/efixes/security/pcnfsd.tar.Z - --- [LINUX PATCH] --------------------------------------------------------- Solution: Working in conjunction with Patrick Volkerding and the Slackware Linux development staff, RSI has produced the following patches: ftp://ftp.repsec.com/pub/repsec/0008.patch1 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: [snip...] - - if(strpbrk(s, ";|&<>`'#!?*()[]^/") != NULL) [snip...] + if (strspn(s, "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ- _=:+1234567890@%,.") [snip...] --- ftp://ftp.repsec.com/pub/repsec/0008.patch2 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. [snip...] + 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); [snip...] - - (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)) { (void)sprintf(tempstr, - --- [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 E-Mail: advise@repsec.com FTP: ftp://ftp.repsec.com WWW: http://www.repsec.com [End RSI Advisory ] ______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Repent Security Incorporated (RSI) for the information contained in this bulletin. ______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. 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