LinuxSecurity.com
Share your story
The central voice for Linux and Open Source security news
Home News Topics Advisories HOWTOs Features Newsletters About Register

Welcome!
Sign up!
EnGarde Community
Login
Polls
What is the most important Linux security technology?
 
Advisories
Community
Linux Events
Linux User Groups
Link to Us
Security Center
Book Reviews
Security Dictionary
Security Tips
SELinux
White Papers
Featured Blogs
All About Linux
DanWalsh LiveJournal
Securitydistro
Latest Newsletters
Linux Advisory Watch: October 24th, 2014
Linux Security Week: October 20th, 2014
Subscribe
LinuxSecurity Newsletters
E-mail:
Choose Lists:
About our Newsletters
RSS Feeds
Get the LinuxSecurity news you want faster with RSS
Powered By

  
FreeBSD-SA-96:01:sliplogin unauthorized access vulnerability Print E-mail
User Rating:      How can I rate this item?
Posted by LinuxSecurity.com Team   
FreeBSD The sliplogin program is used to allow a remote user to dial into a FreeBSD system and start a SLIP connection. The sliplogin program is typically used as replacement user "shell" in this application. The sliplogin program invokes a child process that may be compromised through the passing of certain environment variables.
-----BEGIN PGP SIGNED MESSAGE-----

=============================================================================
FreeBSD-SA-96:01                                            Security Advisory
Revised: Wed May 22 00:18:51 PDT 1996                           FreeBSD, Inc.

Topic:          sliplogin unauthorized access vulnerability

Category:       core
Module:         sliplogin
Announced:      1996-04-21
Affects:        FreeBSD 2.0.5 and 2.1.0 systems where sliplogin may
                be invoked as a user shell (in /etc/passwd entries).
Corrected:      1996-04-21 -stable and -current sources
Source:         Generic BSD bug
FreeBSD only:   no

Reference:      AUSCERT Advisory correspondence

Patches:        ftp://freebsd.org/pub/CERT/patches/SA-96:01/

=============================================================================

I.   Background    

     A bug was found in the sliplogin program.  The program did
     not properly restrict the environment used when invoking
     child processes.  This problem is present in all source code
     and binary distributions of FreeBSD version 2.0.5 and 2.1
     released before 1996-04-21.


II.  Problem Description

     The sliplogin program is used to allow a remote user to dial
     into a FreeBSD system and start a SLIP connection.  The sliplogin
     program is typically used as replacement user "shell" in this
     application.  The sliplogin program invokes a child process that
     may be compromised through the passing of certain environment
     variables.


III. Impact

     The problem could allow local users to gain unauthorized access
     to a system or provide unauthorized access to remote users.
     This problem is only exploitable on systems where the sliplogin
     program has been configured to be invoked at login time (e.g. as
     a user shell in /etc/passwd entries).

IV. Solution(s)

     The following patch to sliplogin.c eliminates this vulnerability.

    *** sliplogin.c     1996/01/06 07:19:55     1.3.4.1
    --- sliplogin.c     1996/04/24 20:20:00     1.3.4.2
    ***************
    *** 88,93 ****
    --- 88,100 ----
      #include 
      #include "pathnames.h"
      
    + extern char **environ;
    + 
    + static char *restricted_environ[] = {
    +   "PATH=" _PATH_STDPATH,
    +   NULL
    + };
    + 
      int       unit;
      int       slip_mode;
      speed_t speed;
    ***************
    *** 123,128 ****
    --- 130,137 ----
            char user[16];
            char buf[128];
            int i, j, n;
    + 
    +   environ = restricted_environ; /* minimal protection for system() */
      
            (void)strcpy(loginname, name);
            if ((fp = fopen(_PATH_ACCESS, "r")) == NULL) {


V. Workaround

     This vulnerability can quickly and easily be limited by disabling
     any account that has sliplogin as the user shell in /etc/passwd or
     by disabling access to the sliplogin command.

     As root, execute the command:

          # chmod 000 /usr/sbin/mount_union

     then verify that all access permission to the file has been
     disabled.  The permissions array should read "----------" as
     shown here:

           # ls -l /usr/sbin/sliplogin
           ----------  1 root  bin  16384 Apr 26 04:47 /usr/sbin/sliplogin


=============================================================================
FreeBSD, Inc.

Web Site:                       http://www.freebsd.org/
Confidential contacts:          security-officer@freebsd.org
PGP Key:                        ftp://freebsd.org/pub/CERT/public_key.asc
Security notifications:         security-notifications@freebsd.org
Security public discussion:     security@freebsd.org

Notice: Any patches in this document may not apply cleanly due to
        modifications caused by digital signature or mailer software.
        Please reference the URL listed at the top of this document
        for original copies of all patches if necessary.
=============================================================================

-----BEGIN PGP SIGNATURE-----
Version: 2.6.2

iQCVAwUBMaLAiVUuHi5z0oilAQFjMQQAlBJ/nnV0+FpmAdxkn1e3wr97oXPoGLfz
hKbTHbQACcsYAJBZXItC8gGxwbDze0H06PidR81anVOch8pkthRbam6rYNWUsAwZ
2PyWy7Q8pmeBz0vVhUYKQgLFWFzSdibvPJQjNA53uUvKymJHvEUeDj8MigQdxcvh
2MkW1XGtVyQ=
=8oT/
-----END PGP SIGNATURE-----
 
< Prev   Next >
    
Partner

 

Latest Features
Peter Smith Releases Linux Network Security Online
Securing a Linux Web Server
Password guessing with Medusa 2.0
Password guessing as an attack vector
Squid and Digest Authentication
Squid and Basic Authentication
Demystifying the Chinese Hacking Industry: Earning 6 Million a Night
Free Online security course (LearnSIA) - A Call for Help
What You Need to Know About Linux Rootkits
Review: A Practical Guide to Fedora and Red Hat Enterprise Linux - Fifth Edition
Yesterday's Edition
Disaster as CryptoWall encrypts US firm's entire server installation
Now Everyone Wants to Sell You a Magical Anonymity Router. Choose Wisely
Partner Sponsor

Community | HOWTOs | Blogs | Features | Book Reviews | Networking
 Security Projects |  Latest News |  Newsletters |  SELinux |  Privacy |  Home
 Hardening |   About Us |   Advertise |   Legal Notice |   RSS |   Guardian Digital
(c)Copyright 2014 Guardian Digital, Inc. All rights reserved.