include/linux/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 */
  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
 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
 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
 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
 306 static inline struct key *__key_get(struct key *key)
 307 {
 308         refcount_inc(&key->usage);
 309         return key;
 310 }
 311
 312 static inline struct key *key_get(struct key *key)
 313 {
 314         return key ? __key_get(key) : key;
 315 }
 316
 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  */
 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_restrict(key_ref_t keyring, const char *type,
 440                             const char *restriction);
 441
 442 extern struct key *key_lookup(key_serial_t id);
 443
 444 static inline key_serial_t key_serial(const struct key *key)
 445 {
 446         return key ? key->serial : 0;
 447 }
 448
 449 extern void key_set_timeout(struct key *, unsigned);
 450
 451 extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags,
 452                                  enum key_need_perm need_perm);
 453 extern void key_free_user_ns(struct user_namespace *);
 454
 455 static inline short key_read_state(const struct key *key)
 456 {
 457         /* Barrier versus mark_key_instantiated(). */
 458         return smp_load_acquire(&key->state);
 459 }
 460
 461 /**
 462  * key_is_positive - Determine if a key has been positively instantiated
 463  * @key: The key to check.
 464  *
 465  * Return true if the specified key has been positively instantiated, false
 466  * otherwise.
 467  */
 468 static inline bool key_is_positive(const struct key *key)
 469 {
 470         return key_read_state(key) == KEY_IS_POSITIVE;
 471 }
 472
 473 static inline bool key_is_negative(const struct key *key)
 474 {
 475         return key_read_state(key) < 0;
 476 }
 477
 478 #define dereference_key_rcu(KEY)                                        \
 479         (rcu_dereference((KEY)->payload.rcu_data0))
 480
 481 #define dereference_key_locked(KEY)                                     \
 482         (rcu_dereference_protected((KEY)->payload.rcu_data0,            \
 483                                    rwsem_is_locked(&((struct key *)(KEY))->sem)))
 484
 485 #define rcu_assign_keypointer(KEY, PAYLOAD)                             \
 486 do {                                                                    \
 487         rcu_assign_pointer((KEY)->payload.rcu_data0, (PAYLOAD));        \
 488 } while (0)
 489
 490 /*
 491  * the userspace interface
 492  */
 493 extern int install_thread_keyring_to_cred(struct cred *cred);
 494 extern void key_fsuid_changed(struct cred *new_cred);
 495 extern void key_fsgid_changed(struct cred *new_cred);
 496 extern void key_init(void);
 497
 498 #else /* CONFIG_KEYS */
 499
 500 #define key_validate(k)                 0
 501 #define key_serial(k)                   0
 502 #define key_get(k)                      ({ NULL; })
 503 #define key_revoke(k)                   do { } while(0)
 504 #define key_invalidate(k)               do { } while(0)
 505 #define key_put(k)                      do { } while(0)
 506 #define key_ref_put(k)                  do { } while(0)
 507 #define make_key_ref(k, p)              NULL
 508 #define key_ref_to_ptr(k)               NULL
 509 #define is_key_possessed(k)             0
 510 #define key_fsuid_changed(c)            do { } while(0)
 511 #define key_fsgid_changed(c)            do { } while(0)
 512 #define key_init()                      do { } while(0)
 513 #define key_free_user_ns(ns)            do { } while(0)
 514 #define key_remove_domain(d)            do { } while(0)
 515 #define key_lookup(k)                   NULL
 516
 517 #endif /* CONFIG_KEYS */
 518 #endif /* __KERNEL__ */
 519 #endif /* _LINUX_KEY_H */