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Date: Sat, 31 May 2014 01:37:01 +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 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...
> + pr_notice("Loaded X.509 cert '%s' on .owner_keyring\n",
> + key_ref_to_ptr(key)->description);
> + }
> +}
> +
> +static void load_owner_identified_builtin_key(key_ref_t key)
> +{
> + if (!owner_keyid && !builtin_keyring)
> + return;
> +
It looks like builtin_keyring is useless...
Is it like linking all .system keys to owners keyring???
Why not just to return .system keyring in get_system_or_owner_trusted_keyring()
based on owner_keyid?
> + if (!builtin_keyring && !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;
The same...
Linking any key forces to use owner trusted keyring...
> + pr_notice("Loaded X.509 cert '%s' on .owner_keyring\n",
> + key_ref_to_ptr(key)->description);
> + }
> +}
> +
> +/*
> + * Use the owner_trusted_keyring if available
> + */
> +struct key *get_system_or_owner_trusted_keyring(void)
> +{
> + return use_owner_trusted_keyring ? owner_trusted_keyring :
> + system_trusted_keyring;
> +}
> +
> /*
> * Load the compiled-in keys
> */
> @@ -50,6 +114,25 @@ static __init int system_trusted_keyring_init(void)
> device_initcall(system_trusted_keyring_init);
>
> /*
> + * Load the owner trusted key
> + */
> +static __init int owner_trusted_keyring_init(void)
> +{
> + pr_notice("Initialize the owner trusted keyring\n");
> +
> + owner_trusted_keyring =
> + keyring_alloc(".owner_keyring",
> + KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
> + ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
> + KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
> + KEY_ALLOC_NOT_IN_QUOTA, NULL);
> + if (IS_ERR(owner_trusted_keyring))
> + panic("Can't allocate owner trusted keyring\n");
> + return 0;
> +}
> +device_initcall(owner_trusted_keyring_init);
> +
> +/*
> * Load the compiled-in list of X.509 certificates.
> */
> static __init int load_system_certificate_list(void)
> @@ -91,6 +174,8 @@ static __init int load_system_certificate_list(void)
> } else {
> pr_notice("Loaded X.509 cert '%s'\n",
> key_ref_to_ptr(key)->description);
> +
> + load_owner_identified_builtin_key(key);
> key_ref_put(key);
> }
> p += plen;
> diff --git a/security/keys/key.c b/security/keys/key.c
> index 2048a11..b448ab1 100644
> --- a/security/keys/key.c
> +++ b/security/keys/key.c
> @@ -701,6 +701,26 @@ void key_type_put(struct key_type *ktype)
> up_read(&key_types_sem);
> }
>
> +/*
> + * Use the key type's match function to compare the key's id.
> + */
> +int key_match(key_ref_t key, const char *type, const char *description)
> +{
> + struct keyring_index_key index_key;
> + int ret = 0;
> +
> + index_key.type = key_type_lookup(type);
> + if (IS_ERR(index_key.type))
> + goto out;
> +
> + if (index_key.type->match &&
> + index_key.type->match(key_ref_to_ptr(key), description))
> + ret = 1;
> + key_type_put(index_key.type);
> +out:
> + return ret;
> +}
> +
> /*
> * Attempt to update an existing key.
> *
> --
> 1.8.1.4
>
> --
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--
Thanks,
Dmitry
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