Messages in this thread | | | Subject | Re: [Umbrella-devel] Re: Getting full path from dentry in LSM hooks | From | Valdis.Kletnieks@vt ... | Date | Fri, 03 Sep 2004 16:39:01 -0400 |
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On Fri, 03 Sep 2004 22:05:03 +0200, =?UTF-8?B?S3Jpc3RpYW4gU8O4cmVuc2Vu?= said:
> Also simple bufferoverflows in suid-root programs may be avoided. The > simple way would to set the restriction "no fork", and thus if an > attacker tries to fork a (root) shell, this would be denied.
All this does is stop fork(). I'm not sure, but most shellcodes I've seen don't bother forking, they just execve() a shell....
It doesn't stop a buffer overflow that does this:
f1 = open("/bin/bash"); f2 = open("/tmp/bash", O_CREAT); while ((bytes = read(f1,buffer,sizeof(buffer))) > 0) write(f2,buffer,bytes); fchmod(f2,4775); close(f1); close(f2);
Papering over *that* one by restricting fchmod just means the exploit needs to append a line to /etc/passwd, or create a trojan inetd.conf or crontab entry, or any of the other myriad ways a program can leave a backdoor (there's a *reason* SELinux ends up with all those rules - this isn't an easy task)...
Remember - just papering over the fact that most shellcodes just execve() a shell doesn't fix the fundemental problem, which is that the attacker is able to run code of his choosing as root.
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