On Tue, 24 Sep 2024, Jarkko Sakkinen wrote:
> On Mon Sep 23, 2024 at 5:04 PM EEST, Mikulas Patocka wrote:
> >
> >
> > On Sun, 22 Sep 2024, luca.bocca...@gmail.com wrote:
> >
> > > From: Luca Boccassi <bl...@debian.org>
> > >
> > > If enabled, we fallback to the platform keyring if the trusted keyring
> > > doesn't have
> > > the key used to sign the roothash. But if pkcs7_verify() rejects the key
> > > for other
> > > reasons, such as usage restrictions, we do not fallback. Do so.
> > >
> > > Follow-up for 6fce1f40e95182ebbfe1ee3096b8fc0b37903269
> > >
> > > Suggested-by: Serge Hallyn <se...@hallyn.com>
> > > Signed-off-by: Luca Boccassi <bl...@debian.org>
> >
> > Hi
> >
> > I'm not an expert in keyrings.
> >
> > I added keyring maintainers to the CC. Please review this patch and
> > Ack/Nack it.
> >
> > Mikulas
> >
> > > ---
> > > drivers/md/dm-verity-verify-sig.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/md/dm-verity-verify-sig.c
> > > b/drivers/md/dm-verity-verify-sig.c
> > > index d351d7d39c60..a9e2c6c0a33c 100644
> > > --- a/drivers/md/dm-verity-verify-sig.c
> > > +++ b/drivers/md/dm-verity-verify-sig.c
> > > @@ -127,7 +127,7 @@ int verity_verify_root_hash(const void *root_hash,
> > > size_t root_hash_len,
> > > #endif
> > > VERIFYING_UNSPECIFIED_SIGNATURE, NULL, NULL);
> > > #ifdef CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG_PLATFORM_KEYRING
> > > - if (ret == -ENOKEY)
> > > + if (ret == -ENOKEY || ret == -EKEYREJECTED)
> > > ret = verify_pkcs7_signature(root_hash, root_hash_len, sig_data,
> > > sig_len,
> > > VERIFY_USE_PLATFORM_KEYRING,
> > > --
> > > 2.39.5
> > >
>
> I know nothing about dm-verity. What does it even do?
>
> BR, Jarkko
dm-verity provides a read-only device with integrity checking. dm-verity
stores hash for every block on the block device and checks the hash when
reading the block. If the hash doesn't match, it can do one of these
actions (depending on configuration):
- return I/O error
- try to correct the data using forward error correction
- log the mismatch and do nothing
- restart the machine
- call panic()
dm-verity is mostly used for the immutable system partition on Android
phones. For more info, see
Documentation/admin-guide/device-mapper/verity.rst
The above patch changes the way that the signature of the root hash is
verified. I have no clue whether the patch can or can't subvert system
security, that's why I'd like to have some more reviews of the patch
before accepting it.
Mikulas
