Protecting System Binaries From Trojan Attack

junyoung writes "Brett Lymn has added verified exec to NetBSD-current, which verifies a cryptographic hash before allowing execution of binaries and scripts. This can be used to prevent a system from running binaries or scripts which have been illegally modified or installed. Verified exec can also be used to limit the use of script interpreters to authorized scripts only and disallow interactive use."

Comments

I guess...

[Hard_Code]

This raises the constant on the level of security, but not the order of magnitude. From what I read, this just makes it more burdensome on the hacker...it's not actually introducing a new level of security. I suppose this would be good for internet 'appliances' where the access is probably limited to any holes or buffer overflows in web scripting languages. But it seems if one has access to the file system (prerequisite for trojaning anyway) this system breaks:

"Even if the file did have the same inode if the contents are modified then the fingerprint will not match anyway."

Huh?? So, the attacker just regens the hash on the trojaned binary and the kernel thinks it is the cached value...am I missing something here? Can one NOT change the cached hash without creating a seperate inode or something?