[PATCH v2 0/4] ubifs: support authentication without hmac

[Richard Weinberger]

----- Ursprüngliche Mail -----
> I didn't dig deep into the code so far, I'm still checking the concept.
> 
> Your approach works only on pristine offline signed images from mkfs.ubifs.
> So, if somebody does this, it won't work:
> 
> $ keyctl padd logon ubifs:authfs @s < secret.key
> $ mount -t ubifs /dev/ubi0_0 /mnt/ -o
> auth_hash_name=sha256,auth_key=ubifs:authfs
> 
> ... change the fs ...
> 
> $ umount /mnt
> $ mount -t ubifs /dev/ubi0_0 /mnt/ -o auth_hash_name=sha256,ro
> 
> The ro mount will fail because UBIFS is no longer able to verify the super block
> using the system key ring. It was overwritten by they ubifs:authfs key.
> 
> A possible solution is keeping a copy of the offline sign key forever in the fs.
> But I'm not sure whether this is wise.

Or we change the feature from "ro mount without hmac" to "keep offline sign key and imply ro mount".
IOW adding a new mount option such as "auth_keep_offlinekey". If mounted with this option
UBIFS will not look for a hmac and enforce read-only mode.

Hmm?

Thanks,
//richard