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Message-ID: <CACE9dm-bqp-a3yogxEDk3M1c-XByuYki+7jZK3=U=VtqDMkCRQ@mail.gmail.com>
Date: Mon, 2 Jun 2014 14:40:28 +0300
From: Dmitry Kasatkin <dmitry.kasatkin@...il.com>
To: Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc: linux-security-module <linux-security-module@...r.kernel.org>,
Dmitry Kasatkin <d.kasatkin@...sung.com>,
David Howells <dhowells@...hat.com>,
Josh Boyer <jwboyer@...hat.com>,
keyrings <keyrings@...ux-nfs.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v4 4/4] KEYS: define an owner trusted keyring
On 2 June 2014 14:33, Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:
> On Mon, 2014-06-02 at 13:48 +0300, Dmitry Kasatkin wrote:
>> On 1 June 2014 05:14, Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:
>> > On Sat, 2014-05-31 at 01:37 +0300, Dmitry Kasatkin wrote:
>> >> On 28 May 2014 18:09, Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:
>> >> > (UEFI) secure boot provides a signature chain of trust rooted in
>> >> > hardware. The signature chain of trust includes the Machine Owner
>> >> > Keys(MOKs), which cannot be modified without physical presence.
>> >> >
>> >> > Instead of allowing public keys, with certificates signed by any
>> >> > key on the system trusted keyring, to be added to a trusted
>> >> > keyring, this patch further restricts the certificates to those
>> >> > signed by the machine owner's key or chosen key.
>> >> >
>> >> > This patch defines an owner trusted keyring, defines a new boot
>> >> > command line option 'keyring=' to designate the machine owner's
>> >> > chosen key, and renames the function get_system_trusted_keyring()
>> >> > to get_system_or_owner_trusted_keyring().
>> >> >
>> >> > This patch permits the machine owner to safely identify their own
>> >> > or chosen key, without requiring it to be builtin the kernel.
>> >> >
>> >> > Signed-off-by: Mimi Zohar<zohar@...ux.vnet.ibm.com>
>> >> > ---
>> >> > crypto/asymmetric_keys/x509_public_key.c | 3 +-
>> >> > include/keys/system_keyring.h | 15 ++++--
>> >> > include/linux/key.h | 4 ++
>> >> > kernel/system_keyring.c | 85 ++++++++++++++++++++++++++++++++
>> >> > security/keys/key.c | 20 ++++++++
>> >> > 5 files changed, 121 insertions(+), 6 deletions(-)
>> >> >
>> >> > diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
>> >> > index 1af8a30..6d52790 100644
>> >> > --- a/crypto/asymmetric_keys/x509_public_key.c
>> >> > +++ b/crypto/asymmetric_keys/x509_public_key.c
>> >> > @@ -237,7 +237,8 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
>> >> > if (ret < 0)
>> >> > goto error_free_cert;
>> >> > } else {
>> >> > - ret = x509_validate_trust(cert, get_system_trusted_keyring());
>> >> > + ret = x509_validate_trust(cert,
>> >> > + get_system_or_owner_trusted_keyring());
>> >> > if (!ret)
>> >> > prep->trusted = 1;
>> >> > }
>> >> > diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
>> >> > index 72665eb..f665c33 100644
>> >> > --- a/include/keys/system_keyring.h
>> >> > +++ b/include/keys/system_keyring.h
>> >> > @@ -17,15 +17,20 @@
>> >> > #include <linux/key.h>
>> >> >
>> >> > extern struct key *system_trusted_keyring;
>> >> > -static inline struct key *get_system_trusted_keyring(void)
>> >> > -{
>> >> > - return system_trusted_keyring;
>> >> > -}
>> >> > +extern struct key *owner_trusted_keyring;
>> >> > +
>> >> > +extern struct key *get_system_or_owner_trusted_keyring(void);
>> >> > +extern void load_owner_identified_uefi_key(key_ref_t key);
>> >> > +
>> >> > #else
>> >> > -static inline struct key *get_system_trusted_keyring(void)
>> >> > +static inline struct key *get_system_or_owner_trusted_keyring(void)
>> >> > {
>> >> > return NULL;
>> >> > }
>> >> > +
>> >> > +static void load_owner_identified_uefi_key(key_ref_t key)
>> >> > +{
>> >> > +}
>> >> > #endif
>> >> >
>> >> > #endif /* _KEYS_SYSTEM_KEYRING_H */
>> >> > diff --git a/include/linux/key.h b/include/linux/key.h
>> >> > index cd0abb8..861843a 100644
>> >> > --- a/include/linux/key.h
>> >> > +++ b/include/linux/key.h
>> >> > @@ -267,6 +267,10 @@ extern int wait_for_key_construction(struct key *key, bool intr);
>> >> >
>> >> > extern int key_validate(const struct key *key);
>> >> >
>> >> > +extern int key_match(key_ref_t key,
>> >> > + const char *type,
>> >> > + const char *description);
>> >> > +
>> >> > extern key_ref_t key_create_or_update(key_ref_t keyring,
>> >> > const char *type,
>> >> > const char *description,
>> >> > diff --git a/kernel/system_keyring.c b/kernel/system_keyring.c
>> >> > index 52ebc70..e9b14ac 100644
>> >> > --- a/kernel/system_keyring.c
>> >> > +++ b/kernel/system_keyring.c
>> >> > @@ -19,11 +19,75 @@
>> >> > #include "module-internal.h"
>> >> >
>> >> > struct key *system_trusted_keyring;
>> >> > +struct key *owner_trusted_keyring;
>> >> > EXPORT_SYMBOL_GPL(system_trusted_keyring);
>> >> >
>> >> > extern __initconst const u8 system_certificate_list[];
>> >> > extern __initconst const unsigned long system_certificate_list_size;
>> >> >
>> >> > +static int use_owner_trusted_keyring;
>> >> > +
>> >> > +static char *owner_keyid;
>> >> > +static int builtin_keyring;
>> >> > +static int __init default_keyring_set(char *str)
>> >> > +{
>> >> > + if (!str) /* default: builtin */
>> >> > + return 1;
>> >> > +
>> >> > + if (strcmp(str, "system") == 0) /* use system keyring */
>> >> > + ;
>> >> > + else if (strcmp(str, "builtin") == 0) /* only builtin keys */
>> >> > + builtin_keyring = 1;
>> >> > + else
>> >> > + owner_keyid = str; /* owner local key 'id:xxxxxx' */
>> >> > + return 1;
>> >> > +}
>> >> > +__setup("keyring=", default_keyring_set);
>> >> > +
>> >> > +/*
>> >> > + * Load the owner identified key on the 'owner' trusted keyring.
>> >> > + */
>> >> > +void load_owner_identified_uefi_key(key_ref_t key)
>> >> > +{
>> >> > + if (!owner_keyid || use_owner_trusted_keyring)
>> >> > + return;
>> >> > +
>> >> > + if (!key_match(key, "asymmetric", owner_keyid))
>> >> > + return;
>> >> > +
>> >> > + if (key_link(owner_trusted_keyring, key_ref_to_ptr(key)) == 0) {
>> >> > + set_bit(KEY_FLAG_TRUSTED_ONLY, &owner_trusted_keyring->flags);
>> >> > + use_owner_trusted_keyring = 1;
>> >>
>> >> This is a bit strange...
>> >> Linking any key forces to use owner trusted keyring...
>> >
>> > Wouldn't it be stranger to identify a specific key on the system keyring
>> > and add it to the owner keyring, but then not use it? I don't
>> > understand your concern. What is the problem?
>>
>> This patch technically specifies to use all keys from the system
>> keyring or the one specified
>> by the owner_keyid. Why the owner keyring is needed then at all?
>> owner_keyid can identify the key to use from the system keyring....
>
> Currently only the builtin keys are on the system keyring, but once
> David and Josh's UEFI patches are upstreamed, the UEFI keys will also be
> on the system keyring. At that point, we would want to differentiate
> between the builtin keys and the remaining keys on the system keyring.
> Splitting this patch definitely helps clarify what's happening and, more
> importantly, why.
>
> Mimi
>
Ok. May be would should focus on patches for existing functionality.
If something new comes from other side, it can be addressed by new
another set of patches.
- Dmitry
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