key.h

  1/* SPDX-License-Identifier: GPL-2.0-or-later */
  2/* Authentication token and access key management
  3 *
  4 * Copyright (C) 2004, 2007 Red Hat, Inc. All Rights Reserved.
  5 * Written by David Howells (dhowells@redhat.com)
  6 *
  7 * See Documentation/security/keys/core.rst for information on keys/keyrings.
  8 */
  9
 10#ifndef _LINUX_KEY_H
 11#define _LINUX_KEY_H
 12
 13#include <linux/types.h>
 14#include <linux/list.h>
 15#include <linux/rbtree.h>
 16#include <linux/rcupdate.h>
 17#include <linux/sysctl.h>
 18#include <linux/rwsem.h>
 19#include <linux/atomic.h>
 20#include <linux/assoc_array.h>
 21#include <linux/refcount.h>
 22#include <linux/time64.h>
 23
 24#ifdef __KERNEL__
 25#include <linux/uidgid.h>
 26
 27/* key handle serial number */
 28typedef int32_t key_serial_t;
 29
 30/* key handle permissions mask */
 31typedef uint32_t key_perm_t;
 32
 33struct key;
 34struct net;
 35
 36#ifdef CONFIG_KEYS
 37
 38#undef KEY_DEBUGGING
 39
 40#define KEY_POS_VIEW	0x01000000	/* possessor can view a key's attributes */
 41#define KEY_POS_READ	0x02000000	/* possessor can read key payload / view keyring */
 42#define KEY_POS_WRITE	0x04000000	/* possessor can update key payload / add link to keyring */
 43#define KEY_POS_SEARCH	0x08000000	/* possessor can find a key in search / search a keyring */
 44#define KEY_POS_LINK	0x10000000	/* possessor can create a link to a key/keyring */
 45#define KEY_POS_SETATTR	0x20000000	/* possessor can set key attributes */
 46#define KEY_POS_ALL	0x3f000000
 47
 48#define KEY_USR_VIEW	0x00010000	/* user permissions... */
 49#define KEY_USR_READ	0x00020000
 50#define KEY_USR_WRITE	0x00040000
 51#define KEY_USR_SEARCH	0x00080000
 52#define KEY_USR_LINK	0x00100000
 53#define KEY_USR_SETATTR	0x00200000
 54#define KEY_USR_ALL	0x003f0000
 55
 56#define KEY_GRP_VIEW	0x00000100	/* group permissions... */
 57#define KEY_GRP_READ	0x00000200
 58#define KEY_GRP_WRITE	0x00000400
 59#define KEY_GRP_SEARCH	0x00000800
 60#define KEY_GRP_LINK	0x00001000
 61#define KEY_GRP_SETATTR	0x00002000
 62#define KEY_GRP_ALL	0x00003f00
 63
 64#define KEY_OTH_VIEW	0x00000001	/* third party permissions... */
 65#define KEY_OTH_READ	0x00000002
 66#define KEY_OTH_WRITE	0x00000004
 67#define KEY_OTH_SEARCH	0x00000008
 68#define KEY_OTH_LINK	0x00000010
 69#define KEY_OTH_SETATTR	0x00000020
 70#define KEY_OTH_ALL	0x0000003f
 71
 72#define KEY_PERM_UNDEF	0xffffffff
 73
 74/*
 75 * The permissions required on a key that we're looking up.
 76 */
 77enum key_need_perm {
 78	KEY_NEED_UNSPECIFIED,	/* Needed permission unspecified */
 79	KEY_NEED_VIEW,		/* Require permission to view attributes */
 80	KEY_NEED_READ,		/* Require permission to read content */
 81	KEY_NEED_WRITE,		/* Require permission to update / modify */
 82	KEY_NEED_SEARCH,	/* Require permission to search (keyring) or find (key) */
 83	KEY_NEED_LINK,		/* Require permission to link */
 84	KEY_NEED_SETATTR,	/* Require permission to change attributes */
 85	KEY_NEED_UNLINK,	/* Require permission to unlink key */
 86	KEY_SYSADMIN_OVERRIDE,	/* Special: override by CAP_SYS_ADMIN */
 87	KEY_AUTHTOKEN_OVERRIDE,	/* Special: override by possession of auth token */
 88	KEY_DEFER_PERM_CHECK,	/* Special: permission check is deferred */
 89};
 90
 91enum key_lookup_flag {
 92	KEY_LOOKUP_CREATE = 0x01,
 93	KEY_LOOKUP_PARTIAL = 0x02,
 94	KEY_LOOKUP_ALL = (KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL),
 95};
 96
 97struct seq_file;
 98struct user_struct;
 99struct signal_struct;
100struct cred;
101
102struct key_type;
103struct key_owner;
104struct key_tag;
105struct keyring_list;
106struct keyring_name;
107
108struct key_tag {
109	struct rcu_head		rcu;
110	refcount_t		usage;
111	bool			removed;	/* T when subject removed */
112};
113
114struct keyring_index_key {
115	/* [!] If this structure is altered, the union in struct key must change too! */
116	unsigned long		hash;			/* Hash value */
117	union {
118		struct {
119#ifdef __LITTLE_ENDIAN /* Put desc_len at the LSB of x */
120			u16	desc_len;
121			char	desc[sizeof(long) - 2];	/* First few chars of description */
122#else
123			char	desc[sizeof(long) - 2];	/* First few chars of description */
124			u16	desc_len;
125#endif
126		};
127		unsigned long x;
128	};
129	struct key_type		*type;
130	struct key_tag		*domain_tag;	/* Domain of operation */
131	const char		*description;
132};
133
134union key_payload {
135	void __rcu		*rcu_data0;
136	void			*data[4];
137};
138
139/*****************************************************************************/
140/*
141 * key reference with possession attribute handling
142 *
143 * NOTE! key_ref_t is a typedef'd pointer to a type that is not actually
144 * defined. This is because we abuse the bottom bit of the reference to carry a
145 * flag to indicate whether the calling process possesses that key in one of
146 * its keyrings.
147 *
148 * the key_ref_t has been made a separate type so that the compiler can reject
149 * attempts to dereference it without proper conversion.
150 *
151 * the three functions are used to assemble and disassemble references
152 */
153typedef struct __key_reference_with_attributes *key_ref_t;
154
155static inline key_ref_t make_key_ref(const struct key *key,
156				     bool possession)
157{
158	return (key_ref_t) ((unsigned long) key | possession);
159}
160
161static inline struct key *key_ref_to_ptr(const key_ref_t key_ref)
162{
163	return (struct key *) ((unsigned long) key_ref & ~1UL);
164}
165
166static inline bool is_key_possessed(const key_ref_t key_ref)
167{
168	return (unsigned long) key_ref & 1UL;
169}
170
171typedef int (*key_restrict_link_func_t)(struct key *dest_keyring,
172					const struct key_type *type,
173					const union key_payload *payload,
174					struct key *restriction_key);
175
176struct key_restriction {
177	key_restrict_link_func_t check;
178	struct key *key;
179	struct key_type *keytype;
180};
181
182enum key_state {
183	KEY_IS_UNINSTANTIATED,
184	KEY_IS_POSITIVE,		/* Positively instantiated */
185};
186
187/*****************************************************************************/
188/*
189 * authentication token / access credential / keyring
190 * - types of key include:
191 *   - keyrings
192 *   - disk encryption IDs
193 *   - Kerberos TGTs and tickets
194 */
195struct key {
196	refcount_t		usage;		/* number of references */
197	key_serial_t		serial;		/* key serial number */
198	union {
199		struct list_head graveyard_link;
200		struct rb_node	serial_node;
201	};
202#ifdef CONFIG_KEY_NOTIFICATIONS
203	struct watch_list	*watchers;	/* Entities watching this key for changes */
204#endif
205	struct rw_semaphore	sem;		/* change vs change sem */
206	struct key_user		*user;		/* owner of this key */
207	void			*security;	/* security data for this key */
208	union {
209		time64_t	expiry;		/* time at which key expires (or 0) */
210		time64_t	revoked_at;	/* time at which key was revoked */
211	};
212	time64_t		last_used_at;	/* last time used for LRU keyring discard */
213	kuid_t			uid;
214	kgid_t			gid;
215	key_perm_t		perm;		/* access permissions */
216	unsigned short		quotalen;	/* length added to quota */
217	unsigned short		datalen;	/* payload data length
218						 * - may not match RCU dereferenced payload
219						 * - payload should contain own length
220						 */
221	short			state;		/* Key state (+) or rejection error (-) */
222
223#ifdef KEY_DEBUGGING
224	unsigned		magic;
225#define KEY_DEBUG_MAGIC		0x18273645u
226#endif
227
228	unsigned long		flags;		/* status flags (change with bitops) */
229#define KEY_FLAG_DEAD		0	/* set if key type has been deleted */
230#define KEY_FLAG_REVOKED	1	/* set if key had been revoked */
231#define KEY_FLAG_IN_QUOTA	2	/* set if key consumes quota */
232#define KEY_FLAG_USER_CONSTRUCT	3	/* set if key is being constructed in userspace */
233#define KEY_FLAG_ROOT_CAN_CLEAR	4	/* set if key can be cleared by root without permission */
234#define KEY_FLAG_INVALIDATED	5	/* set if key has been invalidated */
235#define KEY_FLAG_BUILTIN	6	/* set if key is built in to the kernel */
236#define KEY_FLAG_ROOT_CAN_INVAL	7	/* set if key can be invalidated by root without permission */
237#define KEY_FLAG_KEEP		8	/* set if key should not be removed */
238#define KEY_FLAG_UID_KEYRING	9	/* set if key is a user or user session keyring */
239#define KEY_FLAG_USER_ALIVE	10	/* set if final put has not happened on key yet */
240
241	/* the key type and key description string
242	 * - the desc is used to match a key against search criteria
243	 * - it should be a printable string
244	 * - eg: for krb5 AFS, this might be "afs@REDHAT.COM"
245	 */
246	union {
247		struct keyring_index_key index_key;
248		struct {
249			unsigned long	hash;
250			unsigned long	len_desc;
251			struct key_type	*type;		/* type of key */
252			struct key_tag	*domain_tag;	/* Domain of operation */
253			char		*description;
254		};
255	};
256
257	/* key data
258	 * - this is used to hold the data actually used in cryptography or
259	 *   whatever
260	 */
261	union {
262		union key_payload payload;
263		struct {
264			/* Keyring bits */
265			struct list_head name_link;
266			struct assoc_array keys;
267		};
268	};
269
270	/* This is set on a keyring to restrict the addition of a link to a key
271	 * to it.  If this structure isn't provided then it is assumed that the
272	 * keyring is open to any addition.  It is ignored for non-keyring
273	 * keys. Only set this value using keyring_restrict(), keyring_alloc(),
274	 * or key_alloc().
275	 *
276	 * This is intended for use with rings of trusted keys whereby addition
277	 * to the keyring needs to be controlled.  KEY_ALLOC_BYPASS_RESTRICTION
278	 * overrides this, allowing the kernel to add extra keys without
279	 * restriction.
280	 */
281	struct key_restriction *restrict_link;
282};
283
284extern struct key *key_alloc(struct key_type *type,
285			     const char *desc,
286			     kuid_t uid, kgid_t gid,
287			     const struct cred *cred,
288			     key_perm_t perm,
289			     unsigned long flags,
290			     struct key_restriction *restrict_link);
291
292
293#define KEY_ALLOC_IN_QUOTA		0x0000	/* add to quota, reject if would overrun */
294#define KEY_ALLOC_QUOTA_OVERRUN		0x0001	/* add to quota, permit even if overrun */
295#define KEY_ALLOC_NOT_IN_QUOTA		0x0002	/* not in quota */
296#define KEY_ALLOC_BUILT_IN		0x0004	/* Key is built into kernel */
297#define KEY_ALLOC_BYPASS_RESTRICTION	0x0008	/* Override the check on restricted keyrings */
298#define KEY_ALLOC_UID_KEYRING		0x0010	/* allocating a user or user session keyring */
299#define KEY_ALLOC_SET_KEEP		0x0020	/* Set the KEEP flag on the key/keyring */
300
301extern void key_revoke(struct key *key);
302extern void key_invalidate(struct key *key);
303extern void key_put(struct key *key);
304extern bool key_put_tag(struct key_tag *tag);
305extern void key_remove_domain(struct key_tag *domain_tag);
306
307static inline struct key *__key_get(struct key *key)
308{
309	refcount_inc(&key->usage);
310	return key;
311}
312
313static inline struct key *key_get(struct key *key)
314{
315	return key ? __key_get(key) : key;
316}
317
318static inline void key_ref_put(key_ref_t key_ref)
319{
320	key_put(key_ref_to_ptr(key_ref));
321}
322
323extern struct key *request_key_tag(struct key_type *type,
324				   const char *description,
325				   struct key_tag *domain_tag,
326				   const char *callout_info);
327
328extern struct key *request_key_rcu(struct key_type *type,
329				   const char *description,
330				   struct key_tag *domain_tag);
331
332extern struct key *request_key_with_auxdata(struct key_type *type,
333					    const char *description,
334					    struct key_tag *domain_tag,
335					    const void *callout_info,
336					    size_t callout_len,
337					    void *aux);
338
339/**
340 * request_key - Request a key and wait for construction
341 * @type: Type of key.
342 * @description: The searchable description of the key.
343 * @callout_info: The data to pass to the instantiation upcall (or NULL).
344 *
345 * As for request_key_tag(), but with the default global domain tag.
346 */
347static inline struct key *request_key(struct key_type *type,
348				      const char *description,
349				      const char *callout_info)
350{
351	return request_key_tag(type, description, NULL, callout_info);
352}
353
354#ifdef CONFIG_NET
355/**
356 * request_key_net - Request a key for a net namespace and wait for construction
357 * @type: Type of key.
358 * @description: The searchable description of the key.
359 * @net: The network namespace that is the key's domain of operation.
360 * @callout_info: The data to pass to the instantiation upcall (or NULL).
361 *
362 * As for request_key() except that it does not add the returned key to a
363 * keyring if found, new keys are always allocated in the user's quota, the
364 * callout_info must be a NUL-terminated string and no auxiliary data can be
365 * passed.  Only keys that operate the specified network namespace are used.
366 *
367 * Furthermore, it then works as wait_for_key_construction() to wait for the
368 * completion of keys undergoing construction with a non-interruptible wait.
369 */
370#define request_key_net(type, description, net, callout_info) \
371	request_key_tag(type, description, net->key_domain, callout_info)
372
373/**
374 * request_key_net_rcu - Request a key for a net namespace under RCU conditions
375 * @type: Type of key.
376 * @description: The searchable description of the key.
377 * @net: The network namespace that is the key's domain of operation.
378 *
379 * As for request_key_rcu() except that only keys that operate the specified
380 * network namespace are used.
381 */
382#define request_key_net_rcu(type, description, net) \
383	request_key_rcu(type, description, net->key_domain)
384#endif /* CONFIG_NET */
385
386extern int wait_for_key_construction(struct key *key, bool intr);
387
388extern int key_validate(const struct key *key);
389
390extern key_ref_t key_create(key_ref_t keyring,
391			    const char *type,
392			    const char *description,
393			    const void *payload,
394			    size_t plen,
395			    key_perm_t perm,
396			    unsigned long flags);
397
398extern key_ref_t key_create_or_update(key_ref_t keyring,
399				      const char *type,
400				      const char *description,
401				      const void *payload,
402				      size_t plen,
403				      key_perm_t perm,
404				      unsigned long flags);
405
406extern int key_update(key_ref_t key,
407		      const void *payload,
408		      size_t plen);
409
410extern int key_link(struct key *keyring,
411		    struct key *key);
412
413extern int key_move(struct key *key,
414		    struct key *from_keyring,
415		    struct key *to_keyring,
416		    unsigned int flags);
417
418extern int key_unlink(struct key *keyring,
419		      struct key *key);
420
421extern struct key *keyring_alloc(const char *description, kuid_t uid, kgid_t gid,
422				 const struct cred *cred,
423				 key_perm_t perm,
424				 unsigned long flags,
425				 struct key_restriction *restrict_link,
426				 struct key *dest);
427
428extern int restrict_link_reject(struct key *keyring,
429				const struct key_type *type,
430				const union key_payload *payload,
431				struct key *restriction_key);
432
433extern int keyring_clear(struct key *keyring);
434
435extern key_ref_t keyring_search(key_ref_t keyring,
436				struct key_type *type,
437				const char *description,
438				bool recurse);
439
440extern int keyring_restrict(key_ref_t keyring, const char *type,
441			    const char *restriction);
442
443extern struct key *key_lookup(key_serial_t id);
444
445static inline key_serial_t key_serial(const struct key *key)
446{
447	return key ? key->serial : 0;
448}
449
450extern void key_set_timeout(struct key *, unsigned);
451
452extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags,
453				 enum key_need_perm need_perm);
454extern void key_free_user_ns(struct user_namespace *);
455
456static inline short key_read_state(const struct key *key)
457{
458	/* Barrier versus mark_key_instantiated(). */
459	return smp_load_acquire(&key->state);
460}
461
462/**
463 * key_is_positive - Determine if a key has been positively instantiated
464 * @key: The key to check.
465 *
466 * Return true if the specified key has been positively instantiated, false
467 * otherwise.
468 */
469static inline bool key_is_positive(const struct key *key)
470{
471	return key_read_state(key) == KEY_IS_POSITIVE;
472}
473
474static inline bool key_is_negative(const struct key *key)
475{
476	return key_read_state(key) < 0;
477}
478
479#define dereference_key_rcu(KEY)					\
480	(rcu_dereference((KEY)->payload.rcu_data0))
481
482#define dereference_key_locked(KEY)					\
483	(rcu_dereference_protected((KEY)->payload.rcu_data0,		\
484				   rwsem_is_locked(&((struct key *)(KEY))->sem)))
485
486#define rcu_assign_keypointer(KEY, PAYLOAD)				\
487do {									\
488	rcu_assign_pointer((KEY)->payload.rcu_data0, (PAYLOAD));	\
489} while (0)
490
491/*
492 * the userspace interface
493 */
494extern int install_thread_keyring_to_cred(struct cred *cred);
495extern void key_fsuid_changed(struct cred *new_cred);
496extern void key_fsgid_changed(struct cred *new_cred);
497extern void key_init(void);
498
499#else /* CONFIG_KEYS */
500
501#define key_validate(k)			0
502#define key_serial(k)			0
503#define key_get(k) 			({ NULL; })
504#define key_revoke(k)			do { } while(0)
505#define key_invalidate(k)		do { } while(0)
506#define key_put(k)			do { } while(0)
507#define key_ref_put(k)			do { } while(0)
508#define make_key_ref(k, p)		NULL
509#define key_ref_to_ptr(k)		NULL
510#define is_key_possessed(k)		0
511#define key_fsuid_changed(c)		do { } while(0)
512#define key_fsgid_changed(c)		do { } while(0)
513#define key_init()			do { } while(0)
514#define key_free_user_ns(ns)		do { } while(0)
515#define key_remove_domain(d)		do { } while(0)
516#define key_lookup(k)			NULL
517
518#endif /* CONFIG_KEYS */
519#endif /* __KERNEL__ */
520#endif /* _LINUX_KEY_H */