xref: /openbmc/linux/include/linux/key.h (revision 28898e26)
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 */
28 typedef int32_t key_serial_t;
29 
30 /* key handle permissions mask */
31 typedef uint32_t key_perm_t;
32 
33 struct key;
34 struct 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  */
77 enum 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 
91 enum 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 
97 struct seq_file;
98 struct user_struct;
99 struct signal_struct;
100 struct cred;
101 
102 struct key_type;
103 struct key_owner;
104 struct key_tag;
105 struct keyring_list;
106 struct keyring_name;
107 
108 struct key_tag {
109 	struct rcu_head		rcu;
110 	refcount_t		usage;
111 	bool			removed;	/* T when subject removed */
112 };
113 
114 struct 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 
134 union 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  */
153 typedef struct __key_reference_with_attributes *key_ref_t;
154 
make_key_ref(const struct key * key,bool possession)155 static 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 
key_ref_to_ptr(const key_ref_t key_ref)161 static 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 
is_key_possessed(const key_ref_t key_ref)166 static inline bool is_key_possessed(const key_ref_t key_ref)
167 {
168 	return (unsigned long) key_ref & 1UL;
169 }
170 
171 typedef 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 
176 struct key_restriction {
177 	key_restrict_link_func_t check;
178 	struct key *key;
179 	struct key_type *keytype;
180 };
181 
182 enum 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  */
195 struct 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 
240 	/* the key type and key description string
241 	 * - the desc is used to match a key against search criteria
242 	 * - it should be a printable string
243 	 * - eg: for krb5 AFS, this might be "afs@REDHAT.COM"
244 	 */
245 	union {
246 		struct keyring_index_key index_key;
247 		struct {
248 			unsigned long	hash;
249 			unsigned long	len_desc;
250 			struct key_type	*type;		/* type of key */
251 			struct key_tag	*domain_tag;	/* Domain of operation */
252 			char		*description;
253 		};
254 	};
255 
256 	/* key data
257 	 * - this is used to hold the data actually used in cryptography or
258 	 *   whatever
259 	 */
260 	union {
261 		union key_payload payload;
262 		struct {
263 			/* Keyring bits */
264 			struct list_head name_link;
265 			struct assoc_array keys;
266 		};
267 	};
268 
269 	/* This is set on a keyring to restrict the addition of a link to a key
270 	 * to it.  If this structure isn't provided then it is assumed that the
271 	 * keyring is open to any addition.  It is ignored for non-keyring
272 	 * keys. Only set this value using keyring_restrict(), keyring_alloc(),
273 	 * or key_alloc().
274 	 *
275 	 * This is intended for use with rings of trusted keys whereby addition
276 	 * to the keyring needs to be controlled.  KEY_ALLOC_BYPASS_RESTRICTION
277 	 * overrides this, allowing the kernel to add extra keys without
278 	 * restriction.
279 	 */
280 	struct key_restriction *restrict_link;
281 };
282 
283 extern struct key *key_alloc(struct key_type *type,
284 			     const char *desc,
285 			     kuid_t uid, kgid_t gid,
286 			     const struct cred *cred,
287 			     key_perm_t perm,
288 			     unsigned long flags,
289 			     struct key_restriction *restrict_link);
290 
291 
292 #define KEY_ALLOC_IN_QUOTA		0x0000	/* add to quota, reject if would overrun */
293 #define KEY_ALLOC_QUOTA_OVERRUN		0x0001	/* add to quota, permit even if overrun */
294 #define KEY_ALLOC_NOT_IN_QUOTA		0x0002	/* not in quota */
295 #define KEY_ALLOC_BUILT_IN		0x0004	/* Key is built into kernel */
296 #define KEY_ALLOC_BYPASS_RESTRICTION	0x0008	/* Override the check on restricted keyrings */
297 #define KEY_ALLOC_UID_KEYRING		0x0010	/* allocating a user or user session keyring */
298 #define KEY_ALLOC_SET_KEEP		0x0020	/* Set the KEEP flag on the key/keyring */
299 
300 extern void key_revoke(struct key *key);
301 extern void key_invalidate(struct key *key);
302 extern void key_put(struct key *key);
303 extern bool key_put_tag(struct key_tag *tag);
304 extern void key_remove_domain(struct key_tag *domain_tag);
305 
__key_get(struct key * key)306 static inline struct key *__key_get(struct key *key)
307 {
308 	refcount_inc(&key->usage);
309 	return key;
310 }
311 
key_get(struct key * key)312 static inline struct key *key_get(struct key *key)
313 {
314 	return key ? __key_get(key) : key;
315 }
316 
key_ref_put(key_ref_t key_ref)317 static inline void key_ref_put(key_ref_t key_ref)
318 {
319 	key_put(key_ref_to_ptr(key_ref));
320 }
321 
322 extern struct key *request_key_tag(struct key_type *type,
323 				   const char *description,
324 				   struct key_tag *domain_tag,
325 				   const char *callout_info);
326 
327 extern struct key *request_key_rcu(struct key_type *type,
328 				   const char *description,
329 				   struct key_tag *domain_tag);
330 
331 extern struct key *request_key_with_auxdata(struct key_type *type,
332 					    const char *description,
333 					    struct key_tag *domain_tag,
334 					    const void *callout_info,
335 					    size_t callout_len,
336 					    void *aux);
337 
338 /**
339  * request_key - Request a key and wait for construction
340  * @type: Type of key.
341  * @description: The searchable description of the key.
342  * @callout_info: The data to pass to the instantiation upcall (or NULL).
343  *
344  * As for request_key_tag(), but with the default global domain tag.
345  */
request_key(struct key_type * type,const char * description,const char * callout_info)346 static inline struct key *request_key(struct key_type *type,
347 				      const char *description,
348 				      const char *callout_info)
349 {
350 	return request_key_tag(type, description, NULL, callout_info);
351 }
352 
353 #ifdef CONFIG_NET
354 /**
355  * request_key_net - Request a key for a net namespace and wait for construction
356  * @type: Type of key.
357  * @description: The searchable description of the key.
358  * @net: The network namespace that is the key's domain of operation.
359  * @callout_info: The data to pass to the instantiation upcall (or NULL).
360  *
361  * As for request_key() except that it does not add the returned key to a
362  * keyring if found, new keys are always allocated in the user's quota, the
363  * callout_info must be a NUL-terminated string and no auxiliary data can be
364  * passed.  Only keys that operate the specified network namespace are used.
365  *
366  * Furthermore, it then works as wait_for_key_construction() to wait for the
367  * completion of keys undergoing construction with a non-interruptible wait.
368  */
369 #define request_key_net(type, description, net, callout_info) \
370 	request_key_tag(type, description, net->key_domain, callout_info)
371 
372 /**
373  * request_key_net_rcu - Request a key for a net namespace under RCU conditions
374  * @type: Type of key.
375  * @description: The searchable description of the key.
376  * @net: The network namespace that is the key's domain of operation.
377  *
378  * As for request_key_rcu() except that only keys that operate the specified
379  * network namespace are used.
380  */
381 #define request_key_net_rcu(type, description, net) \
382 	request_key_rcu(type, description, net->key_domain)
383 #endif /* CONFIG_NET */
384 
385 extern int wait_for_key_construction(struct key *key, bool intr);
386 
387 extern int key_validate(const struct key *key);
388 
389 extern key_ref_t key_create(key_ref_t keyring,
390 			    const char *type,
391 			    const char *description,
392 			    const void *payload,
393 			    size_t plen,
394 			    key_perm_t perm,
395 			    unsigned long flags);
396 
397 extern key_ref_t key_create_or_update(key_ref_t keyring,
398 				      const char *type,
399 				      const char *description,
400 				      const void *payload,
401 				      size_t plen,
402 				      key_perm_t perm,
403 				      unsigned long flags);
404 
405 extern int key_update(key_ref_t key,
406 		      const void *payload,
407 		      size_t plen);
408 
409 extern int key_link(struct key *keyring,
410 		    struct key *key);
411 
412 extern int key_move(struct key *key,
413 		    struct key *from_keyring,
414 		    struct key *to_keyring,
415 		    unsigned int flags);
416 
417 extern int key_unlink(struct key *keyring,
418 		      struct key *key);
419 
420 extern struct key *keyring_alloc(const char *description, kuid_t uid, kgid_t gid,
421 				 const struct cred *cred,
422 				 key_perm_t perm,
423 				 unsigned long flags,
424 				 struct key_restriction *restrict_link,
425 				 struct key *dest);
426 
427 extern int restrict_link_reject(struct key *keyring,
428 				const struct key_type *type,
429 				const union key_payload *payload,
430 				struct key *restriction_key);
431 
432 extern int keyring_clear(struct key *keyring);
433 
434 extern key_ref_t keyring_search(key_ref_t keyring,
435 				struct key_type *type,
436 				const char *description,
437 				bool recurse);
438 
439 extern int keyring_add_key(struct key *keyring,
440 			   struct key *key);
441 
442 extern int keyring_restrict(key_ref_t keyring, const char *type,
443 			    const char *restriction);
444 
445 extern struct key *key_lookup(key_serial_t id);
446 
key_serial(const struct key * key)447 static inline key_serial_t key_serial(const struct key *key)
448 {
449 	return key ? key->serial : 0;
450 }
451 
452 extern void key_set_timeout(struct key *, unsigned);
453 
454 extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags,
455 				 enum key_need_perm need_perm);
456 extern void key_free_user_ns(struct user_namespace *);
457 
key_read_state(const struct key * key)458 static inline short key_read_state(const struct key *key)
459 {
460 	/* Barrier versus mark_key_instantiated(). */
461 	return smp_load_acquire(&key->state);
462 }
463 
464 /**
465  * key_is_positive - Determine if a key has been positively instantiated
466  * @key: The key to check.
467  *
468  * Return true if the specified key has been positively instantiated, false
469  * otherwise.
470  */
key_is_positive(const struct key * key)471 static inline bool key_is_positive(const struct key *key)
472 {
473 	return key_read_state(key) == KEY_IS_POSITIVE;
474 }
475 
key_is_negative(const struct key * key)476 static inline bool key_is_negative(const struct key *key)
477 {
478 	return key_read_state(key) < 0;
479 }
480 
481 #define dereference_key_rcu(KEY)					\
482 	(rcu_dereference((KEY)->payload.rcu_data0))
483 
484 #define dereference_key_locked(KEY)					\
485 	(rcu_dereference_protected((KEY)->payload.rcu_data0,		\
486 				   rwsem_is_locked(&((struct key *)(KEY))->sem)))
487 
488 #define rcu_assign_keypointer(KEY, PAYLOAD)				\
489 do {									\
490 	rcu_assign_pointer((KEY)->payload.rcu_data0, (PAYLOAD));	\
491 } while (0)
492 
493 /*
494  * the userspace interface
495  */
496 extern int install_thread_keyring_to_cred(struct cred *cred);
497 extern void key_fsuid_changed(struct cred *new_cred);
498 extern void key_fsgid_changed(struct cred *new_cred);
499 extern void key_init(void);
500 
501 #else /* CONFIG_KEYS */
502 
503 #define key_validate(k)			0
504 #define key_serial(k)			0
505 #define key_get(k) 			({ NULL; })
506 #define key_revoke(k)			do { } while(0)
507 #define key_invalidate(k)		do { } while(0)
508 #define key_put(k)			do { } while(0)
509 #define key_ref_put(k)			do { } while(0)
510 #define make_key_ref(k, p)		NULL
511 #define key_ref_to_ptr(k)		NULL
512 #define is_key_possessed(k)		0
513 #define key_fsuid_changed(c)		do { } while(0)
514 #define key_fsgid_changed(c)		do { } while(0)
515 #define key_init()			do { } while(0)
516 #define key_free_user_ns(ns)		do { } while(0)
517 #define key_remove_domain(d)		do { } while(0)
518 
519 #endif /* CONFIG_KEYS */
520 #endif /* __KERNEL__ */
521 #endif /* _LINUX_KEY_H */
522