path: root/security/keys/keyctl.c
diff options
authorDavid Howells <dhowells@redhat.com>2019-06-27 23:03:07 +0100
committerDavid Howells <dhowells@redhat.com>2019-06-27 23:03:07 +0100
commit2e12256b9a76584fa3a6da19210509d4775aee36 (patch)
treed25d8a5868dadab6086230223afeb9d26fac001b /security/keys/keyctl.c
parentkeys: Pass the network namespace into request_key mechanism (diff)
keys: Replace uid/gid/perm permissions checking with an ACL
Replace the uid/gid/perm permissions checking on a key with an ACL to allow the SETATTR and SEARCH permissions to be split. This will also allow a greater range of subjects to represented. ============ WHY DO THIS? ============ The problem is that SETATTR and SEARCH cover a slew of actions, not all of which should be grouped together. For SETATTR, this includes actions that are about controlling access to a key: (1) Changing a key's ownership. (2) Changing a key's security information. (3) Setting a keyring's restriction. And actions that are about managing a key's lifetime: (4) Setting an expiry time. (5) Revoking a key. and (proposed) managing a key as part of a cache: (6) Invalidating a key. Managing a key's lifetime doesn't really have anything to do with controlling access to that key. Expiry time is awkward since it's more about the lifetime of the content and so, in some ways goes better with WRITE permission. It can, however, be set unconditionally by a process with an appropriate authorisation token for instantiating a key, and can also be set by the key type driver when a key is instantiated, so lumping it with the access-controlling actions is probably okay. As for SEARCH permission, that currently covers: (1) Finding keys in a keyring tree during a search. (2) Permitting keyrings to be joined. (3) Invalidation. But these don't really belong together either, since these actions really need to be controlled separately. Finally, there are number of special cases to do with granting the administrator special rights to invalidate or clear keys that I would like to handle with the ACL rather than key flags and special checks. =============== WHAT IS CHANGED =============== The SETATTR permission is split to create two new permissions: (1) SET_SECURITY - which allows the key's owner, group and ACL to be changed and a restriction to be placed on a keyring. (2) REVOKE - which allows a key to be revoked. The SEARCH permission is split to create: (1) SEARCH - which allows a keyring to be search and a key to be found. (2) JOIN - which allows a keyring to be joined as a session keyring. (3) INVAL - which allows a key to be invalidated. The WRITE permission is also split to create: (1) WRITE - which allows a key's content to be altered and links to be added, removed and replaced in a keyring. (2) CLEAR - which allows a keyring to be cleared completely. This is split out to make it possible to give just this to an administrator. (3) REVOKE - see above. Keys acquire ACLs which consist of a series of ACEs, and all that apply are unioned together. An ACE specifies a subject, such as: (*) Possessor - permitted to anyone who 'possesses' a key (*) Owner - permitted to the key owner (*) Group - permitted to the key group (*) Everyone - permitted to everyone Note that 'Other' has been replaced with 'Everyone' on the assumption that you wouldn't grant a permit to 'Other' that you wouldn't also grant to everyone else. Further subjects may be made available by later patches. The ACE also specifies a permissions mask. The set of permissions is now: VIEW Can view the key metadata READ Can read the key content WRITE Can update/modify the key content SEARCH Can find the key by searching/requesting LINK Can make a link to the key SET_SECURITY Can change owner, ACL, expiry INVAL Can invalidate REVOKE Can revoke JOIN Can join this keyring CLEAR Can clear this keyring The KEYCTL_SETPERM function is then deprecated. The KEYCTL_SET_TIMEOUT function then is permitted if SET_SECURITY is set, or if the caller has a valid instantiation auth token. The KEYCTL_INVALIDATE function then requires INVAL. The KEYCTL_REVOKE function then requires REVOKE. The KEYCTL_JOIN_SESSION_KEYRING function then requires JOIN to join an existing keyring. The JOIN permission is enabled by default for session keyrings and manually created keyrings only. ====================== BACKWARD COMPATIBILITY ====================== To maintain backward compatibility, KEYCTL_SETPERM will translate the permissions mask it is given into a new ACL for a key - unless KEYCTL_SET_ACL has been called on that key, in which case an error will be returned. It will convert possessor, owner, group and other permissions into separate ACEs, if each portion of the mask is non-zero. SETATTR permission turns on all of INVAL, REVOKE and SET_SECURITY. WRITE permission turns on WRITE, REVOKE and, if a keyring, CLEAR. JOIN is turned on if a keyring is being altered. The KEYCTL_DESCRIBE function translates the ACL back into a permissions mask to return depending on possessor, owner, group and everyone ACEs. It will make the following mappings: (1) INVAL, JOIN -> SEARCH (2) SET_SECURITY -> SETATTR (3) REVOKE -> WRITE if SETATTR isn't already set (4) CLEAR -> WRITE Note that the value subsequently returned by KEYCTL_DESCRIBE may not match the value set with KEYCTL_SETATTR. ======= TESTING ======= This passes the keyutils testsuite for all but a couple of tests: (1) tests/keyctl/dh_compute/badargs: The first wrong-key-type test now returns EOPNOTSUPP rather than ENOKEY as READ permission isn't removed if the type doesn't have ->read(). You still can't actually read the key. (2) tests/keyctl/permitting/valid: The view-other-permissions test doesn't work as Other has been replaced with Everyone in the ACL. Signed-off-by: David Howells <dhowells@redhat.com>
Diffstat (limited to 'security/keys/keyctl.c')
1 files changed, 65 insertions, 31 deletions
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index d2f8eabcbcf4..c8911b430e59 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -134,8 +134,7 @@ SYSCALL_DEFINE5(add_key, const char __user *, _type,
/* create or update the requested key and add it to the target
* keyring */
key_ref = key_create_or_update(keyring_ref, type, description,
- payload, plen, KEY_PERM_UNDEF,
+ payload, plen, NULL, KEY_ALLOC_IN_QUOTA);
if (!IS_ERR(key_ref)) {
ret = key_ref_to_ptr(key_ref)->serial;
@@ -225,7 +224,8 @@ SYSCALL_DEFINE4(request_key, const char __user *, _type,
/* do the search */
key = request_key_and_link(ktype, description, NULL, callout_info,
- callout_len, NULL, key_ref_to_ptr(dest_ref),
+ callout_len, NULL, NULL,
+ key_ref_to_ptr(dest_ref),
if (IS_ERR(key)) {
ret = PTR_ERR(key);
@@ -387,16 +387,10 @@ long keyctl_revoke_key(key_serial_t id)
struct key *key;
long ret;
- key_ref = lookup_user_key(id, 0, KEY_NEED_WRITE);
+ key_ref = lookup_user_key(id, 0, KEY_NEED_REVOKE);
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
- if (ret != -EACCES)
- goto error;
- key_ref = lookup_user_key(id, 0, KEY_NEED_SETATTR);
- if (IS_ERR(key_ref)) {
- ret = PTR_ERR(key_ref);
- goto error;
- }
+ goto error;
key = key_ref_to_ptr(key_ref);
@@ -430,7 +424,7 @@ long keyctl_invalidate_key(key_serial_t id)
kenter("%d", id);
- key_ref = lookup_user_key(id, 0, KEY_NEED_SEARCH);
+ key_ref = lookup_user_key(id, 0, KEY_NEED_INVAL);
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
@@ -475,7 +469,7 @@ long keyctl_keyring_clear(key_serial_t ringid)
struct key *keyring;
long ret;
- keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
+ keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_CLEAR);
if (IS_ERR(keyring_ref)) {
ret = PTR_ERR(keyring_ref);
@@ -650,6 +644,7 @@ long keyctl_describe_key(key_serial_t keyid,
size_t buflen)
struct key *key, *instkey;
+ unsigned int perm;
key_ref_t key_ref;
char *infobuf;
long ret;
@@ -679,6 +674,10 @@ okay:
key = key_ref_to_ptr(key_ref);
desclen = strlen(key->description);
+ rcu_read_lock();
+ perm = key_acl_to_perm(rcu_dereference(key->acl));
+ rcu_read_unlock();
/* calculate how much information we're going to return */
ret = -ENOMEM;
infobuf = kasprintf(GFP_KERNEL,
@@ -686,7 +685,7 @@ okay:
from_kuid_munged(current_user_ns(), key->uid),
from_kgid_munged(current_user_ns(), key->gid),
- key->perm);
+ perm);
if (!infobuf)
goto error2;
infolen = strlen(infobuf);
@@ -903,7 +902,7 @@ long keyctl_chown_key(key_serial_t id, uid_t user, gid_t group)
goto error;
key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
goto error;
@@ -998,18 +997,25 @@ quota_overrun:
* the key need not be fully instantiated yet. If the caller does not have
* sysadmin capability, it may only change the permission on keys that it owns.
-long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
+long keyctl_setperm_key(key_serial_t id, unsigned int perm)
+ struct key_acl *acl;
struct key *key;
key_ref_t key_ref;
long ret;
+ int nr, i, j;
- ret = -EINVAL;
- goto error;
+ return -EINVAL;
+ nr = 0;
+ if (perm & KEY_POS_ALL) nr++;
+ if (perm & KEY_USR_ALL) nr++;
+ if (perm & KEY_GRP_ALL) nr++;
+ if (perm & KEY_OTH_ALL) nr++;
key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
goto error;
@@ -1017,17 +1023,45 @@ long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
key = key_ref_to_ptr(key_ref);
- /* make the changes with the locks held to prevent chown/chmod races */
- ret = -EACCES;
- down_write(&key->sem);
+ ret = -EOPNOTSUPP;
+ if (test_bit(KEY_FLAG_HAS_ACL, &key->flags))
+ goto error_key;
- /* if we're not the sysadmin, we can only change a key that we own */
- if (capable(CAP_SYS_ADMIN) || uid_eq(key->uid, current_fsuid())) {
- key->perm = perm;
- ret = 0;
+ ret = -ENOMEM;
+ acl = kzalloc(struct_size(acl, aces, nr), GFP_KERNEL);
+ if (!acl)
+ goto error_key;
+ refcount_set(&acl->usage, 1);
+ acl->nr_ace = nr;
+ j = 0;
+ for (i = 0; i < 4; i++) {
+ struct key_ace *ace = &acl->aces[j];
+ unsigned int subset = (perm >> (i * 8)) & KEY_OTH_ALL;
+ if (!subset)
+ continue;
+ ace->type = KEY_ACE_SUBJ_STANDARD;
+ ace->subject_id = KEY_ACE_EVERYONE + i;
+ ace->perm = subset;
+ if (subset & (KEY_OTH_WRITE | KEY_OTH_SETATTR))
+ ace->perm |= KEY_ACE_REVOKE;
+ if (subset & KEY_OTH_SEARCH)
+ ace->perm |= KEY_ACE_INVAL;
+ if (key->type == &key_type_keyring) {
+ if (subset & KEY_OTH_SEARCH)
+ ace->perm |= KEY_ACE_JOIN;
+ if (subset & KEY_OTH_WRITE)
+ ace->perm |= KEY_ACE_CLEAR;
+ }
+ j++;
+ /* make the changes with the locks held to prevent chown/chmod races */
+ down_write(&key->sem);
+ ret = key_set_acl(key, acl);
return ret;
@@ -1392,7 +1426,7 @@ long keyctl_set_timeout(key_serial_t id, unsigned timeout)
long ret;
key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
if (IS_ERR(key_ref)) {
/* setting the timeout on a key under construction is permitted
* if we have the authorisation token handy */
@@ -1543,7 +1577,7 @@ long keyctl_get_security(key_serial_t keyid,
* Attempt to install the calling process's session keyring on the process's
* parent process.
- * The keyring must exist and must grant the caller LINK permission, and the
+ * The keyring must exist and must grant the caller JOIN permission, and the
* parent process must be single-threaded and must have the same effective
* ownership as this process and mustn't be SUID/SGID.
@@ -1560,7 +1594,7 @@ long keyctl_session_to_parent(void)
struct cred *cred;
int ret;
- keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_NEED_LINK);
+ keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_NEED_JOIN);
if (IS_ERR(keyring_r))
return PTR_ERR(keyring_r);
@@ -1662,7 +1696,7 @@ long keyctl_restrict_keyring(key_serial_t id, const char __user *_type,
char *restriction = NULL;
long ret;
- key_ref = lookup_user_key(id, 0, KEY_NEED_SETATTR);
+ key_ref = lookup_user_key(id, 0, KEY_NEED_SETSEC);
if (IS_ERR(key_ref))
return PTR_ERR(key_ref);
@@ -1768,7 +1802,7 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
return keyctl_setperm_key((key_serial_t) arg2,
- (key_perm_t) arg3);
+ (unsigned int)arg3);
return keyctl_instantiate_key((key_serial_t) arg2,