Re: [PATCH v2] certs: Add EFI_CERT_X509_GUID support for dbx entries

[Jarkko Sakkinen]

On Mon, Sep 14, 2020 at 09:01:34PM +0300, Jarkko Sakkinen wrote:
> On Wed, Sep 09, 2020 at 01:27:36PM -0400, Eric Snowberg wrote:
> > The Secure Boot Forbidden Signature Database, dbx, contains a list of now
> > revoked signatures and keys previously approved to boot with UEFI Secure
> > Boot enabled.  The dbx is capable of containing any number of
> > EFI_CERT_X509_SHA256_GUID, EFI_CERT_SHA256_GUID, and EFI_CERT_X509_GUID
> > entries.
> > 
> > Currently when EFI_CERT_X509_GUID are contained in the dbx, the entries are
> > skipped.
> > 
> > Add support for EFI_CERT_X509_GUID dbx entries. When a EFI_CERT_X509_GUID
> > is found, it is added as an asymmetrical key to the .blacklist keyring.
> > Anytime the .platform keyring is used, the keys in the .blacklist keyring
> > are referenced, if a matching key is found, the key will be rejected.
> > 
> > Signed-off-by: Eric Snowberg <eric.snowberg@xxxxxxxxxx>
> > ---
> > 
> > v2: 
> >  Fixed build issue reported by kernel test robot <lkp@xxxxxxxxx>
> >  Commit message update (suggested by Jarkko Sakkinen)
> > 
> > ---
> >  certs/blacklist.c                             | 36 +++++++++++++++++++
> >  certs/system_keyring.c                        |  6 ++++
> >  include/crypto/pkcs7.h                        |  8 +++++
> >  include/keys/system_keyring.h                 | 11 ++++++
> >  .../platform_certs/keyring_handler.c          | 11 ++++++
> >  5 files changed, 72 insertions(+)
> > 
> > diff --git a/certs/blacklist.c b/certs/blacklist.c
> > index 6514f9ebc943..17ebf50cf0ae 100644
> > --- a/certs/blacklist.c
> > +++ b/certs/blacklist.c
> > @@ -15,6 +15,7 @@
> >  #include <linux/err.h>
> >  #include <linux/seq_file.h>
> >  #include <keys/system_keyring.h>
> > +#include <crypto/pkcs7.h>
> >  #include "blacklist.h"
> >  
> >  static struct key *blacklist_keyring;
> > @@ -100,6 +101,41 @@ int mark_hash_blacklisted(const char *hash)
> >  	return 0;
> >  }
> >  
> > +int mark_key_revocationlisted(const char *data, size_t size)
> > +{
> > +	key_ref_t key;
> > +
> > +	key = key_create_or_update(make_key_ref(blacklist_keyring, true),
> > +				   "asymmetric",
> > +				   NULL,
> > +				   data,
> > +				   size,
> > +				   ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
> > +				    KEY_USR_VIEW),
> > +				   KEY_ALLOC_NOT_IN_QUOTA |
> > +				   KEY_ALLOC_BUILT_IN);
> > +
> > +	if (IS_ERR(key)) {
> > +		pr_err("Problem with revocation key (%ld)\n", PTR_ERR(key));
> > +		return PTR_ERR(key);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +int is_key_revocationlisted(struct pkcs7_message *pkcs7)
> > +{
> > +	int ret;
> > +
> > +	ret = pkcs7_validate_trust(pkcs7, blacklist_keyring);
> > +
> > +	if (ret == 0)
> > +		return -EKEYREJECTED;
> > +
> > +	return -ENOKEY;
> > +}
> > +EXPORT_SYMBOL_GPL(is_key_revocationlisted);
> 
> What required this callable from a module?

Right, nees to be exported for pkcs7.


/Jarkko