From: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
This patch has been added to the 3.18 stable tree. If you have any
objections, please let us know.
===============
[ Upstream commit d3600bcf9d64d88dc1d189a754dcfab960ce751f ]
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: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
include/linux/key.h | 1 +
security/keys/key.c | 6 +++++-
security/keys/keyctl.c | 56 +++++++++++++++++++++++++++++++++++++++++---------
3 files changed, 52 insertions(+), 11 deletions(-)
diff --git a/include/linux/key.h b/include/linux/key.h
index e1d4715..2318331 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -172,6 +172,7 @@ 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
diff --git a/security/keys/key.c b/security/keys/key.c
index e17ba6a..0b7aa0c 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -431,8 +431,12 @@ 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)
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index fee27fe..700c204 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -364,11 +364,14 @@ 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);
@@ -383,8 +386,13 @@ long keyctl_revoke_key(key_serial_t id)
}
}
- key_revoke(key_ref_to_ptr(key_ref));
- ret = 0;
+ 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:
@@ -398,11 +406,14 @@ 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);
@@ -426,8 +437,13 @@ long keyctl_invalidate_key(key_serial_t id)
}
invalidate:
- key_invalidate(key_ref_to_ptr(key_ref));
- ret = 0;
+ 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:
@@ -439,12 +455,13 @@ 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);
@@ -466,7 +483,11 @@ 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:
@@ -517,11 +538,14 @@ 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);
@@ -536,7 +560,13 @@ 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:
@@ -1319,6 +1349,8 @@ 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)
@@ -1350,10 +1382,14 @@ long keyctl_set_timeout(key_serial_t id, unsigned timeout)
okay:
key = key_ref_to_ptr(key_ref);
- key_set_timeout(key, timeout);
+ 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;
}
--
2.5.0
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