FreeBSD-SA-99.05.fts.txt

`----- Forwarded message from FreeBSD Security Officer <[email protected]> -----  
  
Delivered-To: [email protected]  
Date: Wed, 15 Sep 1999 23:25:21 -0600 (MDT)  
From: FreeBSD Security Officer <[email protected]>  
Subject: FreeBSD Security Advisory: FreeBSD-SA-99:05.fts  
Reply-To: [email protected]  
X-Loop: FreeBSD.org  
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-----BEGIN PGP SIGNED MESSAGE-----  
  
=============================================================================  
FreeBSD-SA-99:05 Security Advisory  
FreeBSD, Inc.  
  
Topic: fts library routine vulnerability  
  
Category: core  
Module: kernel  
Announced: 1999-09-15  
Affects: FreeBSD 3.2 (and earlier)  
FreeBSD-current before the correction date.  
FreeBSD 3.2-stable before the correction date.  
Corrected: FreeBSD-3.3 RELEASE  
FreeBSD-current as of 1999/08/26  
FreeBSD-3.2-stable as of 1999/08/26  
The FreeBSD-3.3-RC series of releases are not affected.  
FreeBSD only: NO  
  
Patches: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-99:05/  
  
I. Background  
  
The fts library routines provide a convenient way for a program to  
walk a hierarchy of files.  
  
II. Problem Description  
  
The fts library functions had a buffer overflow in them where which  
would lead to a core dump when periodic ran the security checking  
scripts (or other scripts which traverse trees that can be controlled  
by users). periodic(3) should limit core size to zero to disable core  
dumps while it is executing commands, but does not do so. In  
addition, the kernel should not follow symbolic links.  
  
All three of these problems caused a situation where it was possible  
for an attacker could create or overwrite an arbitrary file on the  
system with a moderate degree of controll of its contents to cause a  
problem.  
  
III. Impact  
  
Local users could gain root access.  
  
IV. Workaround  
  
One can workaround this problem by preventing core dumps for periodic.  
This solution is less than completely satisfying, since it only plugs  
the known exploit hole. None the less, this may provide a short term  
stopgap solution until a new kernel and userland can be installed.  
  
# mv /usr/sbin/periodic /usr/sbin/periodic.bin  
# cat > /usr/sbin/periodic  
#!/bin/sh  
ulimit -c 0  
/usr/sbin/periodic.bin $*  
^D  
# chmod 555 /usr/sbin/periodic  
  
V. Solution  
  
Apply the following patches to libc and do a make world. Please also  
see the companion advisory FreeBSD-SA-99:04.core.asc in the advisories  
directory of our ftp site for details on the kernel portions of this  
fix.  
  
Index: lib/libc/gen/fts.c  
===================================================================  
RCS file: /home/imp/FreeBSD/CVS/src/lib/libc/gen/fts.c,v  
retrieving revision 1.10  
retrieving revision 1.11  
diff -u -r1.10 -r1.11  
--- fts.c 1999/08/15 19:21:29 1.10  
+++ fts.c 1999/09/02 07:45:07 1.11  
@@ -963,6 +963,24 @@  
return (sp->fts_path == NULL);  
}  
  
+static void  
+ADJUST(p, addr)  
+ FTSENT *p;  
+ void *addr;  
+{  
+ if ((p)->fts_accpath >= (p)->fts_path &&   
+ (p)->fts_accpath < (p)->fts_path + (p)->fts_pathlen) {  
+ if (p->fts_accpath != p->fts_path)  
+ errx(1, "fts ADJUST: accpath %p path %p",  
+ p->fts_accpath, p->fts_path);  
+ if (p->fts_level != 0)  
+ errx(1, "fts ADJUST: level %d not 0", p->fts_level);  
+ (p)->fts_accpath =   
+ (char *)addr + ((p)->fts_accpath - (p)->fts_path);   
+ }  
+ (p)->fts_path = addr;   
+}  
+  
/*  
* When the path is realloc'd, have to fix all of the pointers in structures  
* already returned.  
@@ -974,18 +992,18 @@  
{  
FTSENT *p;  
  
-#define ADJUST(p) { \  
- (p)->fts_accpath = \  
- (char *)addr + ((p)->fts_accpath - (p)->fts_path); \  
+#define ADJUST1(p) { \  
+ if ((p)->fts_accpath == (p)->fts_path) \  
+ (p)->fts_accpath = (addr); \  
(p)->fts_path = addr; \  
}  
/* Adjust the current set of children. */  
for (p = sp->fts_child; p; p = p->fts_link)  
- ADJUST(p);  
+ ADJUST(p, addr);  
  
/* Adjust the rest of the tree. */  
for (p = sp->fts_cur; p->fts_level >= FTS_ROOTLEVEL;) {  
- ADJUST(p);  
+ ADJUST(p, addr);  
p = p->fts_link ? p->fts_link : p->fts_parent;  
}  
}  
  
  
=============================================================================  
FreeBSD, Inc.  
  
Web Site: http://www.freebsd.org/  
Confidential contacts: [email protected]  
Security notifications: [email protected]  
Security public discussion: [email protected]  
PGP Key: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/public_key.asc  
  
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.  
=============================================================================  
  
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