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keys: Namespace keyring names

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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>
This commit is contained in:
David Howells 2019-06-26 21:02:32 +01:00
parent dcf49dbc80
commit b206f281d0
7 changed files with 60 additions and 60 deletions
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2
include/linux/key.h
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@ -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__ */