Commit d3600bcf authored by Mimi Zohar's avatar Mimi Zohar
Browse files

KEYS: prevent keys from being removed from specified keyrings 



Userspace should not be allowed to remove keys from certain keyrings
(eg. blacklist), though the keys themselves can expire.

This patch defines a new key flag named KEY_FLAG_KEEP to prevent
userspace from being able to unlink, revoke, invalidate or timed
out a key on a keyring.  When this flag is set on the keyring, all
keys subsequently added are flagged.

In addition, when this flag is set, the keyring itself can not be
cleared.

Signed-off-by: default avatarMimi Zohar <zohar@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
parent 80eae209

include/linux/key.h

+1 −0
Original line number Diff line number Diff line
@@ -177,6 +177,7 @@ struct key { 
#define KEY_FLAG_TRUSTED_ONLY	9	/* set if keyring only accepts links to trusted keys */

#define KEY_FLAG_BUILTIN	10	/* set if key is builtin */

#define KEY_FLAG_ROOT_CAN_INVAL	11	/* set if key can be invalidated by root without permission */

#define KEY_FLAG_KEEP		12	/* set if key should not be removed */



	/* the key type and key description string

	 * - the desc is used to match a key against search criteria

security/keys/key.c

+5 −1
Original line number Diff line number Diff line
@@ -429,8 +429,12 @@ static int __key_instantiate_and_link(struct key *key, 
				awaken = 1;



			/* and link it into the destination keyring */

			if (keyring)

			if (keyring) {

				if (test_bit(KEY_FLAG_KEEP, &keyring->flags))

					set_bit(KEY_FLAG_KEEP, &key->flags);



				__key_link(key, _edit);

			}



			/* disable the authorisation key */

			if (authkey)

security/keys/keyctl.c

+46 −10
Original line number Diff line number Diff line
@@ -358,11 +358,14 @@ error: 
 * and any links to the key will be automatically garbage collected after a

 * certain amount of time (/proc/sys/kernel/keys/gc_delay).

 *

 * Keys with KEY_FLAG_KEEP set should not be revoked.

 *

 * If successful, 0 is returned.

 */

long keyctl_revoke_key(key_serial_t id)

{

	key_ref_t key_ref;

	struct key *key;

	long ret;



	key_ref = lookup_user_key(id, 0, KEY_NEED_WRITE);
@@ -377,8 +380,13 @@ long keyctl_revoke_key(key_serial_t id) 
		}

	}



	key_revoke(key_ref_to_ptr(key_ref));

	key = key_ref_to_ptr(key_ref);

	if (test_bit(KEY_FLAG_KEEP, &key->flags))

		return -EPERM;

	else {

		key_revoke(key);

		ret = 0;

	}



	key_ref_put(key_ref);

error:
@@ -392,11 +400,14 @@ error: 
 * The key and any links to the key will be automatically garbage collected

 * immediately.

 *

 * Keys with KEY_FLAG_KEEP set should not be invalidated.

 *

 * If successful, 0 is returned.

 */

long keyctl_invalidate_key(key_serial_t id)

{

	key_ref_t key_ref;

	struct key *key;

	long ret;



	kenter("%d", id);
@@ -420,8 +431,13 @@ long keyctl_invalidate_key(key_serial_t id) 
	}



invalidate:

	key_invalidate(key_ref_to_ptr(key_ref));

	key = key_ref_to_ptr(key_ref);

	if (test_bit(KEY_FLAG_KEEP, &key->flags))

		ret = -EPERM;

	else {

		key_invalidate(key);

		ret = 0;

	}

error_put:

	key_ref_put(key_ref);

error:
@@ -433,12 +449,13 @@ error: 
 * Clear the specified keyring, creating an empty process keyring if one of the

 * special keyring IDs is used.

 *

 * The keyring must grant the caller Write permission for this to work.  If

 * successful, 0 will be returned.

 * The keyring must grant the caller Write permission and not have

 * KEY_FLAG_KEEP set for this to work.  If successful, 0 will be returned.

 */

long keyctl_keyring_clear(key_serial_t ringid)

{

	key_ref_t keyring_ref;

	struct key *keyring;

	long ret;



	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
@@ -460,7 +477,11 @@ long keyctl_keyring_clear(key_serial_t ringid) 
	}



clear:

	ret = keyring_clear(key_ref_to_ptr(keyring_ref));

	keyring = key_ref_to_ptr(keyring_ref);

	if (test_bit(KEY_FLAG_KEEP, &keyring->flags))

		ret = -EPERM;

	else

		ret = keyring_clear(keyring);

error_put:

	key_ref_put(keyring_ref);

error:
@@ -511,11 +532,14 @@ error: 
 * itself need not grant the caller anything.  If the last link to a key is

 * removed then that key will be scheduled for destruction.

 *

 * Keys or keyrings with KEY_FLAG_KEEP set should not be unlinked.

 *

 * If successful, 0 will be returned.

 */

long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)

{

	key_ref_t keyring_ref, key_ref;

	struct key *keyring, *key;

	long ret;



	keyring_ref = lookup_user_key(ringid, 0, KEY_NEED_WRITE);
@@ -530,7 +554,13 @@ long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid) 
		goto error2;

	}



	ret = key_unlink(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));

	keyring = key_ref_to_ptr(keyring_ref);

	key = key_ref_to_ptr(key_ref);

	if (test_bit(KEY_FLAG_KEEP, &keyring->flags) &&

	    test_bit(KEY_FLAG_KEEP, &key->flags))

		ret = -EPERM;

	else

		ret = key_unlink(keyring, key);



	key_ref_put(key_ref);

error2:
@@ -1289,6 +1319,8 @@ error: 
 * the current time.  The key and any links to the key will be automatically

 * garbage collected after the timeout expires.

 *

 * Keys with KEY_FLAG_KEEP set should not be timed out.

 *

 * If successful, 0 is returned.

 */

long keyctl_set_timeout(key_serial_t id, unsigned timeout)
@@ -1320,10 +1352,14 @@ long keyctl_set_timeout(key_serial_t id, unsigned timeout) 


okay:

	key = key_ref_to_ptr(key_ref);

	if (test_bit(KEY_FLAG_KEEP, &key->flags))

		ret = -EPERM;

	else {

		key_set_timeout(key, timeout);

		ret = 0;

	}

	key_put(key);



	ret = 0;

error:

	return ret;

}

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