keys: Namespace keyring names

Keyring names are held in a single global list that any process can pick
from by means of keyctl_join_session_keyring (provided the keyring grants
Search permission).  This isn't very container friendly, however.

Make the following changes:

 (1) Make default session, process and thread keyring names begin with a
     '.' instead of '_'.

 (2) Keyrings whose names begin with a '.' aren't added to the list.  Such
     keyrings are system specials.

 (3) Replace the global list with per-user_namespace lists.  A keyring adds
     its name to the list for the user_namespace that it is currently in.

 (4) When a user_namespace is deleted, it just removes itself from the
     keyring name list.

The global keyring_name_lock is retained for accessing the name lists.
This allows (4) to work.

This can be tested by:

	# keyctl newring foo @s
	995906392
	# unshare -U
	$ keyctl show
	...
	 995906392 --alswrv  65534 65534   \_ keyring: foo
	...
	$ keyctl session foo
	Joined session keyring: 935622349

As can be seen, a new session keyring was created.

The capability bit KEYCTL_CAPS1_NS_KEYRING_NAME is set if the kernel is
employing this feature.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Eric W. Biederman <ebiederm@xmission.com>

diff --git a/include/linux/key.h b/include/linux/key.h
index ff10273..ae11773 100644 (file)
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -361,6 +361,7 @@ extern void key_set_timeout(struct key *, unsigned);
 
 extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags,
                                 key_perm_t perm);
+extern void key_free_user_ns(struct user_namespace *);
 
 /*
  * The permissions required on a key that we're looking up.
@@ -434,6 +435,7 @@ extern void key_init(void);
 #define key_fsuid_changed(c)           do { } while(0)
 #define key_fsgid_changed(c)           do { } while(0)
 #define key_init()                     do { } while(0)
+#define key_free_user_ns(ns)           do { } while(0)
 
 #endif /* CONFIG_KEYS */
 #endif /* __KERNEL__ */

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index d6b74b9..9045701 100644 (file)
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -64,6 +64,11 @@ struct user_namespace {
        struct ns_common        ns;
        unsigned long           flags;
 
+#ifdef CONFIG_KEYS
+       /* List of joinable keyrings in this namespace */
+       struct list_head        keyring_name_list;
+#endif
+
        /* Register of per-UID persistent keyrings for this namespace */
 #ifdef CONFIG_PERSISTENT_KEYRINGS
        struct key              *persistent_keyring_register;

diff --git a/include/uapi/linux/keyctl.h b/include/uapi/linux/keyctl.h
index 551b581..35b4050 100644 (file)
--- a/include/uapi/linux/keyctl.h
+++ b/include/uapi/linux/keyctl.h
@@ -128,5 +128,6 @@ struct keyctl_pkey_params {
 #define KEYCTL_CAPS0_INVALIDATE                0x20 /* KEYCTL_INVALIDATE supported */
 #define KEYCTL_CAPS0_RESTRICT_KEYRING  0x40 /* KEYCTL_RESTRICT_KEYRING supported */
 #define KEYCTL_CAPS0_MOVE              0x80 /* KEYCTL_MOVE supported */
+#define KEYCTL_CAPS1_NS_KEYRING_NAME   0x01 /* Keyring names are per-user_namespace */
 
 #endif /*  _LINUX_KEYCTL_H */

diff --git a/kernel/user.c b/kernel/user.c
index 88b834f..50979fd 100644 (file)
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -62,6 +62,9 @@ struct user_namespace init_user_ns = {
        .ns.ops = &userns_operations,
 #endif
        .flags = USERNS_INIT_FLAGS,
+#ifdef CONFIG_KEYS
+       .keyring_name_list = LIST_HEAD_INIT(init_user_ns.keyring_name_list),
+#endif
 #ifdef CONFIG_PERSISTENT_KEYRINGS
        .persistent_keyring_register_sem =
        __RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem),

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 923414a..bda6e89 100644 (file)
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -133,6 +133,9 @@ int create_user_ns(struct cred *new)
        ns->flags = parent_ns->flags;
        mutex_unlock(&userns_state_mutex);
 
+#ifdef CONFIG_KEYS
+       INIT_LIST_HEAD(&ns->keyring_name_list);
+#endif
 #ifdef CONFIG_PERSISTENT_KEYRINGS
        init_rwsem(&ns->persistent_keyring_register_sem);
 #endif
@@ -196,9 +199,7 @@ static void free_user_ns(struct work_struct *work)
                        kfree(ns->projid_map.reverse);
                }
                retire_userns_sysctls(ns);
-#ifdef CONFIG_PERSISTENT_KEYRINGS
-               key_put(ns->persistent_keyring_register);
-#endif
+               key_free_user_ns(ns);
                ns_free_inum(&ns->ns);
                kmem_cache_free(user_ns_cachep, ns);
                dec_user_namespaces(ucounts);

diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 169409b..8a81322 100644 (file)
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -30,7 +30,7 @@
 
 #define KEY_MAX_DESC_SIZE 4096
 
-static const unsigned char keyrings_capabilities[1] = {
+static const unsigned char keyrings_capabilities[2] = {
        [0] = (KEYCTL_CAPS0_CAPABILITIES |
               (IS_ENABLED(CONFIG_PERSISTENT_KEYRINGS)  ? KEYCTL_CAPS0_PERSISTENT_KEYRINGS : 0) |
               (IS_ENABLED(CONFIG_KEY_DH_OPERATIONS)    ? KEYCTL_CAPS0_DIFFIE_HELLMAN : 0) |
@@ -40,6 +40,7 @@ static const unsigned char keyrings_capabilities[1] = {
               KEYCTL_CAPS0_RESTRICT_KEYRING |
               KEYCTL_CAPS0_MOVE
               ),
+       [1] = (KEYCTL_CAPS1_NS_KEYRING_NAME),
 };
 
 static int key_get_type_from_user(char *type,

diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 20891cd..fe85129 100644 (file)
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -16,6 +16,7 @@
 #include <linux/security.h>
 #include <linux/seq_file.h>
 #include <linux/err.h>
+#include <linux/user_namespace.h>
 #include <keys/keyring-type.h>
 #include <keys/user-type.h>
 #include <linux/assoc_array_priv.h>
@@ -29,11 +30,6 @@
 #define KEYRING_SEARCH_MAX_DEPTH 6
 
 /*
- * We keep all named keyrings in a hash to speed looking them up.
- */
-#define KEYRING_NAME_HASH_SIZE (1 << 5)
-
-/*
  * We mark pointers we pass to the associative array with bit 1 set if
  * they're keyrings and clear otherwise.
  */
@@ -55,17 +51,20 @@ static inline void *keyring_key_to_ptr(struct key *key)
        return key;
 }
 
-static struct list_head        keyring_name_hash[KEYRING_NAME_HASH_SIZE];
 static DEFINE_RWLOCK(keyring_name_lock);
 
-static inline unsigned keyring_hash(const char *desc)
+/*
+ * Clean up the bits of user_namespace that belong to us.
+ */
+void key_free_user_ns(struct user_namespace *ns)
 {
-       unsigned bucket = 0;
-
-       for (; *desc; desc++)
-               bucket += (unsigned char)*desc;
+       write_lock(&keyring_name_lock);
+       list_del_init(&ns->keyring_name_list);
+       write_unlock(&keyring_name_lock);
 
-       return bucket & (KEYRING_NAME_HASH_SIZE - 1);
+#ifdef CONFIG_PERSISTENT_KEYRINGS
+       key_put(ns->persistent_keyring_register);
+#endif
 }
 
 /*
@@ -104,23 +103,17 @@ static DEFINE_MUTEX(keyring_serialise_link_lock);
 
 /*
  * Publish the name of a keyring so that it can be found by name (if it has
- * one).
+ * one and it doesn't begin with a dot).
  */
 static void keyring_publish_name(struct key *keyring)
 {
-       int bucket;
-
-       if (keyring->description) {
-               bucket = keyring_hash(keyring->description);
+       struct user_namespace *ns = current_user_ns();
 
+       if (keyring->description &&
+           keyring->description[0] &&
+           keyring->description[0] != '.') {
                write_lock(&keyring_name_lock);
-
-               if (!keyring_name_hash[bucket].next)
-                       INIT_LIST_HEAD(&keyring_name_hash[bucket]);
-
-               list_add_tail(&keyring->name_link,
-                             &keyring_name_hash[bucket]);
-
+               list_add_tail(&keyring->name_link, &ns->keyring_name_list);
                write_unlock(&keyring_name_lock);
        }
 }
@@ -1097,50 +1090,44 @@ found:
  */
 struct key *find_keyring_by_name(const char *name, bool uid_keyring)
 {
+       struct user_namespace *ns = current_user_ns();
        struct key *keyring;
-       int bucket;
 
        if (!name)
                return ERR_PTR(-EINVAL);
 
-       bucket = keyring_hash(name);
-
        read_lock(&keyring_name_lock);
 
-       if (keyring_name_hash[bucket].next) {
-               /* search this hash bucket for a keyring with a matching name
-                * that's readable and that hasn't been revoked */
-               list_for_each_entry(keyring,
-                                   &keyring_name_hash[bucket],
-                                   name_link
-                                   ) {
-                       if (!kuid_has_mapping(current_user_ns(), keyring->user->uid))
-                               continue;
-
-                       if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
-                               continue;
+       /* Search this hash bucket for a keyring with a matching name that
+        * grants Search permission and that hasn't been revoked
+        */
+       list_for_each_entry(keyring, &ns->keyring_name_list, name_link) {
+               if (!kuid_has_mapping(ns, keyring->user->uid))
+                       continue;
 
-                       if (strcmp(keyring->description, name) != 0)
-                               continue;
+               if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
+                       continue;
 
-                       if (uid_keyring) {
-                               if (!test_bit(KEY_FLAG_UID_KEYRING,
-                                             &keyring->flags))
-                                       continue;
-                       } else {
-                               if (key_permission(make_key_ref(keyring, 0),
-                                                  KEY_NEED_SEARCH) < 0)
-                                       continue;
-                       }
+               if (strcmp(keyring->description, name) != 0)
+                       continue;
 
-                       /* we've got a match but we might end up racing with
-                        * key_cleanup() if the keyring is currently 'dead'
-                        * (ie. it has a zero usage count) */
-                       if (!refcount_inc_not_zero(&keyring->usage))
+               if (uid_keyring) {
+                       if (!test_bit(KEY_FLAG_UID_KEYRING,
+                                     &keyring->flags))
+                               continue;
+               } else {
+                       if (key_permission(make_key_ref(keyring, 0),
+                                          KEY_NEED_SEARCH) < 0)
                                continue;
-                       keyring->last_used_at = ktime_get_real_seconds();
-                       goto out;
                }
+
+               /* we've got a match but we might end up racing with
+                * key_cleanup() if the keyring is currently 'dead'
+                * (ie. it has a zero usage count) */
+               if (!refcount_inc_not_zero(&keyring->usage))
+                       continue;
+               keyring->last_used_at = ktime_get_real_seconds();
+               goto out;
        }
 
        keyring = ERR_PTR(-ENOKEY);