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Commit 6563c91f authored by Mat Martineau's avatar Mat Martineau
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KEYS: Add KEYCTL_RESTRICT_KEYRING 



Keyrings recently gained restrict_link capabilities that allow
individual keys to be validated prior to linking.  This functionality
was only available using internal kernel APIs.

With the KEYCTL_RESTRICT_KEYRING command existing keyrings can be
configured to check the content of keys before they are linked, and
then allow or disallow linkage of that key to the keyring.

To restrict a keyring, call:

  keyctl(KEYCTL_RESTRICT_KEYRING, key_serial_t keyring, const char *type,
         const char *restriction)

where 'type' is the name of a registered key type and 'restriction' is a
string describing how key linkage is to be restricted. The restriction
option syntax is specific to each key type.

Signed-off-by: default avatarMat Martineau <mathew.j.martineau@linux.intel.com>
parent 4a420896

Documentation/security/keys.txt

+25 −0
Original line number Diff line number Diff line
@@ -857,6 +857,31 @@ The keyctl syscall functions are: 
     supported, error ENOKEY if the key could not be found, or error

     EACCES if the key is not readable by the caller.



 (*) Restrict keyring linkage



       long keyctl(KEYCTL_RESTRICT_KEYRING, key_serial_t keyring,

		   const char *type, const char *restriction);



     An existing keyring can restrict linkage of additional keys by evaluating

     the contents of the key according to a restriction scheme.



     "keyring" is the key ID for an existing keyring to apply a restriction

     to. It may be empty or may already have keys linked. Existing linked keys

     will remain in the keyring even if the new restriction would reject them.



     "type" is a registered key type.



     "restriction" is a string describing how key linkage is to be restricted.

     The format varies depending on the key type, and the string is passed to

     the lookup_restriction() function for the requested type.  It may specify

     a method and relevant data for the restriction such as signature

     verification or constraints on key payload. If the requested key type is

     later unregistered, no keys may be added to the keyring after the key type

     is removed.



     To apply a keyring restriction the process must have Set Attribute

     permission and the keyring must not be previously restricted.



===============

KERNEL SERVICES

===============

include/linux/key.h

+5 −1
Original line number Diff line number Diff line
@@ -219,7 +219,8 @@ struct key { 
	/* This is set on a keyring to restrict the addition of a link to a key

	 * to it.  If this structure isn't provided then it is assumed that the

	 * keyring is open to any addition.  It is ignored for non-keyring

	 * keys.

	 * keys. Only set this value using keyring_restrict(), keyring_alloc(),

	 * or key_alloc().

	 *

	 * This is intended for use with rings of trusted keys whereby addition

	 * to the keyring needs to be controlled.  KEY_ALLOC_BYPASS_RESTRICTION
@@ -328,6 +329,9 @@ extern key_ref_t keyring_search(key_ref_t keyring, 
extern int keyring_add_key(struct key *keyring,

			   struct key *key);



extern int keyring_restrict(key_ref_t keyring, const char *type,

			    const char *restriction);



extern struct key *key_lookup(key_serial_t id);



static inline key_serial_t key_serial(const struct key *key)

include/uapi/linux/keyctl.h

+1 −0
Original line number Diff line number Diff line
@@ -60,6 +60,7 @@ 
#define KEYCTL_INVALIDATE		21	/* invalidate a key */

#define KEYCTL_GET_PERSISTENT		22	/* get a user's persistent keyring */

#define KEYCTL_DH_COMPUTE		23	/* Compute Diffie-Hellman values */

#define KEYCTL_RESTRICT_KEYRING		29	/* Restrict keys allowed to link to a keyring */



/* keyctl structures */

struct keyctl_dh_params {

security/keys/compat.c

+4 −0
Original line number Diff line number Diff line
@@ -136,6 +136,10 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option, 
		return keyctl_dh_compute(compat_ptr(arg2), compat_ptr(arg3),

					 arg4, compat_ptr(arg5));



	case KEYCTL_RESTRICT_KEYRING:

		return keyctl_restrict_keyring(arg2, compat_ptr(arg3),

					       compat_ptr(arg4));



	default:

		return -EOPNOTSUPP;

	}

security/keys/internal.h

+3 −0
Original line number Diff line number Diff line
@@ -252,6 +252,9 @@ struct iov_iter; 
extern long keyctl_instantiate_key_common(key_serial_t,

					  struct iov_iter *,

					  key_serial_t);

extern long keyctl_restrict_keyring(key_serial_t id,

				    const char __user *_type,

				    const char __user *_restriction);

#ifdef CONFIG_PERSISTENT_KEYRINGS

extern long keyctl_get_persistent(uid_t, key_serial_t);

extern unsigned persistent_keyring_expiry;