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KEYS: Introduce link restriction for machine keys 

Introduce a new link restriction that includes the trusted builtin,
secondary and machine keys. The restriction is based on the key to be
added being vouched for by a key in any of these three keyrings.

With the introduction of the machine keyring, the end-user may choose to
trust Machine Owner Keys (MOK) within the kernel. If they have chosen to
trust them, the .machine keyring will contain these keys.  If not, the
machine keyring will always be empty.  Update the restriction check to
allow the secondary trusted keyring to also trust machine keys.

Allow the .machine keyring to be linked to the secondary_trusted_keys.
After the link is created, keys contained in the .machine keyring will
automatically be searched when searching secondary_trusted_keys.

Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Tested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
This commit is contained in:
Eric Snowberg 2022-01-25 21:58:31 -05:00 committed by Jarkko Sakkinen
parent 56edb6c25f
commit 087aa4ed37
2 changed files with 40 additions and 1 deletions
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35
certs/system_keyring.c
View File

@ -89,7 +89,10 @@ static __init struct key_restriction *get_builtin_and_secondary_restriction(void
if (!restriction)
panic("Can't allocate secondary trusted keyring restriction\n");
restriction->check = restrict_link_by_builtin_and_secondary_trusted;
if (IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING))
restriction->check = restrict_link_by_builtin_secondary_and_machine;
else
restriction->check = restrict_link_by_builtin_and_secondary_trusted;
return restriction;
}
@ -98,6 +101,36 @@ static __init struct key_restriction *get_builtin_and_secondary_restriction(void
void __init set_machine_trusted_keys(struct key *keyring)
{
machine_trusted_keys = keyring;
if (key_link(secondary_trusted_keys, machine_trusted_keys) < 0)
panic("Can't link (machine) trusted keyrings\n");
}
/**
* restrict_link_by_builtin_secondary_and_machine - Restrict keyring addition.
* @dest_keyring: Keyring being linked to.
* @type: The type of key being added.
* @payload: The payload of the new key.
* @restrict_key: A ring of keys that can be used to vouch for the new cert.
*
* Restrict the addition of keys into a keyring based on the key-to-be-added
* being vouched for by a key in either the built-in, the secondary, or
* the machine keyrings.
*/
int restrict_link_by_builtin_secondary_and_machine(
struct key *dest_keyring,
const struct key_type *type,
const union key_payload *payload,
struct key *restrict_key)
{
if (machine_trusted_keys && type == &key_type_keyring &&
dest_keyring == secondary_trusted_keys &&
payload == &machine_trusted_keys->payload)
/* Allow the machine keyring to be added to the secondary */
return 0;
return restrict_link_by_builtin_and_secondary_trusted(dest_keyring, type,
payload, restrict_key);
}
#endif

6
include/keys/system_keyring.h
View File

@ -39,8 +39,14 @@ extern int restrict_link_by_builtin_and_secondary_trusted(
#endif
#ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
extern int restrict_link_by_builtin_secondary_and_machine(
struct key *dest_keyring,
const struct key_type *type,
const union key_payload *payload,
struct key *restrict_key);
extern void __init set_machine_trusted_keys(struct key *keyring);
#else
#define restrict_link_by_builtin_secondary_and_machine restrict_link_by_builtin_trusted
static inline void __init set_machine_trusted_keys(struct key *keyring)
{
}