Re: [PATCH v3] certs: Add EFI_CERT_X509_GUID support for dbx entries

[Jarkko Sakkinen]

On Tue, Sep 15, 2020 at 09:42:27AM -0600, Eric Snowberg wrote:
> 
> > On Sep 14, 2020, at 12:12 PM, Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote:
> > 
> > On Fri, Sep 11, 2020 at 02:22:30PM -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>
> >> ---
> >> v3:
> >> Fixed an issue when CONFIG_PKCS7_MESSAGE_PARSER is not builtin and defined
> >> as a module instead, pointed out by Randy Dunlap
> >> 
> >> v2: 
> >> Fixed build issue reported by kernel test robot <lkp@xxxxxxxxx>
> >> Commit message update (suggested by Jarkko Sakkinen)
> >> ---
> >> certs/blacklist.c                             | 33 +++++++++++++++++++
> >> certs/blacklist.h                             | 12 +++++++
> >> certs/system_keyring.c                        |  6 ++++
> >> include/keys/system_keyring.h                 | 11 +++++++
> >> .../platform_certs/keyring_handler.c          | 11 +++++++
> >> 5 files changed, 73 insertions(+)
> >> 
> >> diff --git a/certs/blacklist.c b/certs/blacklist.c
> >> index 6514f9ebc943..3d1514ba5d47 100644
> >> --- a/certs/blacklist.c
> >> +++ b/certs/blacklist.c
> >> @@ -100,6 +100,39 @@ 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 = validate_trust(pkcs7, blacklist_keyring);
> >> +
> >> +	if (ret == 0)
> >> +		return -EKEYREJECTED;
> >> +
> >> +	return -ENOKEY;
> >> +}
> >> +EXPORT_SYMBOL_GPL(is_key_revocationlisted);
> > 
> > Hmm... ignore my previous comment about this. Export symbol is called
> > only by system keyring code.
> > 
> > Would be best if the commit message would explicitly reason new exports.
> 
> I don’t see a good reason to keep the export now, I’ll remove it from the
> next version.  Thanks.

OK, great, thanks.

Was somewhat puzzled with this for a while :-)

/Jarkko