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

[Torben Hohn]

On Fri, Jun 26, 2020 at 04:36:26PM +0200, Richard Weinberger wrote:
> ----- 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.

Thats just another name for the same feature.
But it indeed seems to make the implications clearer.

And it porbably also makes the code easier to read.

> 
> Hmm?
> 
> Thanks,
> //richard

-- 
Torben Hohn
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