Possible race condition in Symantec AntiVirus Scan Engine for Red Hat Linux during LiveUpdate

["Dr. Peter Bieringer" <pbieringer () aerasec de>]

Hi,

during evaluation of Symantec AntiVirus Scan Engine for Red Hat Linux 
(file: Scan_Engine_430-RedHat-1.zip) we found a race condition using 
default configuration.

Like written in "Implementation_Guide.pdf" on page 134 LiveUpdate can be 
triggered by cron via a shell script:

# /opt/SYMCScan/bin/liveupdate.sh -virusdefs
   or
# /bin/sh /opt/SYMCScan/bin/liveupdate.sh -virusdefs

This will create a log file in /tmp with a very predictable name:
"/tmp/LiveUpdate.log" (with permissions of 644)

# ll /tmp/
-rw-r--r--    1 symantec avdefs       4517 Feb 16 15:05 LiveUpdate.log

This is defined in the config file "liveupdate.conf":

# cat /etc/liveupdate.conf
protocol=http
host=liveupdate.symantec.com
workdir=/tmp
logfile=/tmp/LiveUpdate.log  <---!!!!!!

Impact:
Before first run of LiveUpdate (like suggested in doc, user "symantec" does 
this) a possible race condition via a symlink attack by another user will 
result in the creation of a new file (as user "symantec") or appending 
LiveUpdate log to an existent file (owned by user "symantec").

Additional *important* note:
Because the PDF document doesn't match the as-it-is of the installation (an 
user "symantec" can't execute liveupdate.sh" without adjusting the 
permissions of the shell script and the directory "virusdefs") it's very 
possible, that admins configure the crontab entry for "liveupdate.sh" as 
user "root"!

# ll /opt/SYMCScan/bin/liveupdate.sh
-rwxr-x---    1 root     root        14700 Feb 16 16:16 
/opt/SYMCScan/bin/liveupdate.sh

# ll /opt/SYMCScan |grep virusdefs
drwxr-xr-x    2 root     root         4096 Feb 16 16:16 virusdefs


BTW: The installer uses PID for tmp directory naming, another minor issue...

# ll /tmp/
drwxr-xr-x    2 root     root         4096 Feb 16 15:47 symcinst9918
# ps -ax | grep 9918
 9918 pts/0    S      0:02 sh ./ScanEngine.sh

-> fix to a unpredictable name


BTW2: looks like a temp directory during install has always the same name.
# ll /tmp/
drwx------    2 root     root         4096 Feb 16 16:16 savsetmp

-> fix to a unpredictable name


BTW3: temporary directory during LiveUpdate run has permissions 755
# ll /tmp/
drwxr-xr-x    2 root     root         4096 Feb 16 16:37 1076967476267

-> fix permissions to at least 750, perhaps it's also not the best method 
to use Unix time in milliseconds to name this directory.


Suggestions/workarounds:
* for the software vendor:
   use a better default value, e.g.
     logfile=/var/log/LiveUpdate.log
   Fix permissions of log file to at least 640
   Fix PDF document or/and permissions for
     liveupdate.sh and directory virusdefs
     (and on RHL systems: "/usr/bin/sh" doesn't exist, fix to "/bin/sh")
   Fix predictable directory names during installation
   Fix permissions of temp directory during LiveUpdate run to at least 750
   Fix name of temp directory to a more unpredictable one


* for administrators:
   adjust config file before first run of the LiveUpdate process
   adjust permissions of
     liveupdate.sh and directory virusdefs
     and run liveupdate.sh as non-root user


Regards,
        Dr. Peter Bieringer
--
Dr. Peter Bieringer                             Phone: +49-8102-895190
AERAsec Network Services and Security GmbH        Fax: +49-8102-895199
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