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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Authentication token and access key management
* Copyright (C) 2004, 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (
* See Documentation/security/keys/core.rst for information on keys/keyrings.
#ifndef _LINUX_KEY_H
#define _LINUX_KEY_H
#include <linux/types.h>
#include <linux/list.h>
#include <linux/rbtree.h>
#include <linux/rcupdate.h>
#include <linux/sysctl.h>
#include <linux/rwsem.h>
#include <linux/atomic.h>
#include <linux/assoc_array.h>
#include <linux/refcount.h>
#include <linux/time64.h>
#ifdef __KERNEL__
#include <linux/uidgid.h>
/* key handle serial number */
typedef int32_t key_serial_t;
/* key handle permissions mask */
typedef uint32_t key_perm_t;
struct key;
struct net;
#define KEY_POS_VIEW 0x01000000 /* possessor can view a key's attributes */
#define KEY_POS_READ 0x02000000 /* possessor can read key payload / view keyring */
#define KEY_POS_WRITE 0x04000000 /* possessor can update key payload / add link to keyring */
#define KEY_POS_SEARCH 0x08000000 /* possessor can find a key in search / search a keyring */
#define KEY_POS_LINK 0x10000000 /* possessor can create a link to a key/keyring */
#define KEY_POS_SETATTR 0x20000000 /* possessor can set key attributes */
#define KEY_POS_ALL 0x3f000000
#define KEY_USR_VIEW 0x00010000 /* user permissions... */
#define KEY_USR_READ 0x00020000
#define KEY_USR_WRITE 0x00040000
#define KEY_USR_SEARCH 0x00080000
#define KEY_USR_LINK 0x00100000
#define KEY_USR_SETATTR 0x00200000
#define KEY_USR_ALL 0x003f0000
#define KEY_GRP_VIEW 0x00000100 /* group permissions... */
#define KEY_GRP_READ 0x00000200
#define KEY_GRP_WRITE 0x00000400
#define KEY_GRP_SEARCH 0x00000800
#define KEY_GRP_LINK 0x00001000
#define KEY_GRP_SETATTR 0x00002000
#define KEY_GRP_ALL 0x00003f00
#define KEY_OTH_VIEW 0x00000001 /* third party permissions... */
#define KEY_OTH_READ 0x00000002
#define KEY_OTH_WRITE 0x00000004
#define KEY_OTH_SEARCH 0x00000008
#define KEY_OTH_LINK 0x00000010
#define KEY_OTH_SETATTR 0x00000020
#define KEY_OTH_ALL 0x0000003f
#define KEY_PERM_UNDEF 0xffffffff
* The permissions required on a key that we're looking up.
enum key_need_perm {
KEY_NEED_UNSPECIFIED, /* Needed permission unspecified */
KEY_NEED_VIEW, /* Require permission to view attributes */
KEY_NEED_READ, /* Require permission to read content */
KEY_NEED_WRITE, /* Require permission to update / modify */
KEY_NEED_SEARCH, /* Require permission to search (keyring) or find (key) */
KEY_NEED_LINK, /* Require permission to link */
KEY_NEED_SETATTR, /* Require permission to change attributes */
KEY_NEED_UNLINK, /* Require permission to unlink key */
KEY_SYSADMIN_OVERRIDE, /* Special: override by CAP_SYS_ADMIN */
KEY_AUTHTOKEN_OVERRIDE, /* Special: override by possession of auth token */
KEY_DEFER_PERM_CHECK, /* Special: permission check is deferred */
struct seq_file;
struct user_struct;
struct signal_struct;
struct cred;
struct key_type;
struct key_owner;
struct key_tag;
struct keyring_list;
struct keyring_name;
struct key_tag {
struct rcu_head rcu;
refcount_t usage;
bool removed; /* T when subject removed */
struct keyring_index_key {
/* [!] If this structure is altered, the union in struct key must change too! */
unsigned long hash; /* Hash value */
union {
struct {
#ifdef __LITTLE_ENDIAN /* Put desc_len at the LSB of x */
u16 desc_len;
char desc[sizeof(long) - 2]; /* First few chars of description */
char desc[sizeof(long) - 2]; /* First few chars of description */
u16 desc_len;
unsigned long x;
struct key_type *type;
struct key_tag *domain_tag; /* Domain of operation */
const char *description;
union key_payload {
void __rcu *rcu_data0;
void *data[4];
* key reference with possession attribute handling
* NOTE! key_ref_t is a typedef'd pointer to a type that is not actually
* defined. This is because we abuse the bottom bit of the reference to carry a
* flag to indicate whether the calling process possesses that key in one of
* its keyrings.
* the key_ref_t has been made a separate type so that the compiler can reject
* attempts to dereference it without proper conversion.
* the three functions are used to assemble and disassemble references
typedef struct __key_reference_with_attributes *key_ref_t;
static inline key_ref_t make_key_ref(const struct key *key,
bool possession)
return (key_ref_t) ((unsigned long) key | possession);
static inline struct key *key_ref_to_ptr(const key_ref_t key_ref)
return (struct key *) ((unsigned long) key_ref & ~1UL);
static inline bool is_key_possessed(const key_ref_t key_ref)
return (unsigned long) key_ref & 1UL;
typedef int (*key_restrict_link_func_t)(struct key *dest_keyring,
const struct key_type *type,
const union key_payload *payload,
struct key *restriction_key);
struct key_restriction {
key_restrict_link_func_t check;
struct key *key;
struct key_type *keytype;
enum key_state {
KEY_IS_POSITIVE, /* Positively instantiated */
* authentication token / access credential / keyring
* - types of key include:
* - keyrings
* - disk encryption IDs
* - Kerberos TGTs and tickets
struct key {
refcount_t usage; /* number of references */
key_serial_t serial; /* key serial number */
union {
struct list_head graveyard_link;
struct rb_node serial_node;
struct watch_list *watchers; /* Entities watching this key for changes */
struct rw_semaphore sem; /* change vs change sem */
struct key_user *user; /* owner of this key */
void *security; /* security data for this key */
union {
time64_t expiry; /* time at which key expires (or 0) */
time64_t revoked_at; /* time at which key was revoked */
time64_t last_used_at; /* last time used for LRU keyring discard */
kuid_t uid;
kgid_t gid;
key_perm_t perm; /* access permissions */
unsigned short quotalen; /* length added to quota */
unsigned short datalen; /* payload data length
* - may not match RCU dereferenced payload
* - payload should contain own length
short state; /* Key state (+) or rejection error (-) */
unsigned magic;
#define KEY_DEBUG_MAGIC 0x18273645u
unsigned long flags; /* status flags (change with bitops) */
#define KEY_FLAG_DEAD 0 /* set if key type has been deleted */
#define KEY_FLAG_REVOKED 1 /* set if key had been revoked */
#define KEY_FLAG_IN_QUOTA 2 /* set if key consumes quota */
#define KEY_FLAG_USER_CONSTRUCT 3 /* set if key is being constructed in userspace */
#define KEY_FLAG_ROOT_CAN_CLEAR 4 /* set if key can be cleared by root without permission */
#define KEY_FLAG_INVALIDATED 5 /* set if key has been invalidated */
#define KEY_FLAG_BUILTIN 6 /* set if key is built in to the kernel */
#define KEY_FLAG_ROOT_CAN_INVAL 7 /* set if key can be invalidated by root without permission */
#define KEY_FLAG_KEEP 8 /* set if key should not be removed */
#define KEY_FLAG_UID_KEYRING 9 /* set if key is a user or user session keyring */
/* the key type and key description string
* - the desc is used to match a key against search criteria
* - it should be a printable string
* - eg: for krb5 AFS, this might be "afs@REDHAT.COM"
union {
struct keyring_index_key index_key;
struct {
unsigned long hash;
unsigned long len_desc;
struct key_type *type; /* type of key */
struct key_tag *domain_tag; /* Domain of operation */
char *description;
/* key data
* - this is used to hold the data actually used in cryptography or
* whatever
union {
union key_payload payload;
struct {
/* Keyring bits */
struct list_head name_link;
struct assoc_array keys;
/* This is set on a keyring to restrict the addition of a link to a key
* to it. If this structure isn't provided then it is assumed that the
* keyring is open to any addition. It is ignored for non-keyring
* keys. Only set this value using keyring_restrict(), keyring_alloc(),
* or key_alloc().
* This is intended for use with rings of trusted keys whereby addition
* to the keyring needs to be controlled. KEY_ALLOC_BYPASS_RESTRICTION
* overrides this, allowing the kernel to add extra keys without
* restriction.
struct key_restriction *restrict_link;
extern struct key *key_alloc(struct key_type *type,
const char *desc,
kuid_t uid, kgid_t gid,
const struct cred *cred,
key_perm_t perm,
unsigned long flags,
struct key_restriction *restrict_link);
#define KEY_ALLOC_IN_QUOTA 0x0000 /* add to quota, reject if would overrun */
#define KEY_ALLOC_QUOTA_OVERRUN 0x0001 /* add to quota, permit even if overrun */
#define KEY_ALLOC_NOT_IN_QUOTA 0x0002 /* not in quota */
#define KEY_ALLOC_BUILT_IN 0x0004 /* Key is built into kernel */
#define KEY_ALLOC_BYPASS_RESTRICTION 0x0008 /* Override the check on restricted keyrings */
#define KEY_ALLOC_UID_KEYRING 0x0010 /* allocating a user or user session keyring */
extern void key_revoke(struct key *key);
extern void key_invalidate(struct key *key);
extern void key_put(struct key *key);
extern bool key_put_tag(struct key_tag *tag);
extern void key_remove_domain(struct key_tag *domain_tag);
static inline struct key *__key_get(struct key *key)
return key;
static inline struct key *key_get(struct key *key)
return key ? __key_get(key) : key;
static inline void key_ref_put(key_ref_t key_ref)
extern struct key *request_key_tag(struct key_type *type,
const char *description,
struct key_tag *domain_tag,
const char *callout_info);
extern struct key *request_key_rcu(struct key_type *type,
const char *description,
struct key_tag *domain_tag);
extern struct key *request_key_with_auxdata(struct key_type *type,
const char *description,
struct key_tag *domain_tag,
const void *callout_info,
size_t callout_len,
void *aux);
* request_key - Request a key and wait for construction
* @type: Type of key.
* @description: The searchable description of the key.
* @callout_info: The data to pass to the instantiation upcall (or NULL).
* As for request_key_tag(), but with the default global domain tag.
static inline struct key *request_key(struct key_type *type,
const char *description,
const char *callout_info)
return request_key_tag(type, description, NULL, callout_info);
* request_key_net - Request a key for a net namespace and wait for construction
* @type: Type of key.
* @description: The searchable description of the key.
* @net: The network namespace that is the key's domain of operation.
* @callout_info: The data to pass to the instantiation upcall (or NULL).
* As for request_key() except that it does not add the returned key to a
* keyring if found, new keys are always allocated in the user's quota, the
* callout_info must be a NUL-terminated string and no auxiliary data can be
* passed. Only keys that operate the specified network namespace are used.
* Furthermore, it then works as wait_for_key_construction() to wait for the
* completion of keys undergoing construction with a non-interruptible wait.
#define request_key_net(type, description, net, callout_info) \
request_key_tag(type, description, net->key_domain, callout_info);
* request_key_net_rcu - Request a key for a net namespace under RCU conditions
* @type: Type of key.
* @description: The searchable description of the key.
* @net: The network namespace that is the key's domain of operation.
* As for request_key_rcu() except that only keys that operate the specified
* network namespace are used.
#define request_key_net_rcu(type, description, net) \
request_key_rcu(type, description, net->key_domain);
#endif /* CONFIG_NET */
extern int wait_for_key_construction(struct key *key, bool intr);
extern int key_validate(const struct key *key);
extern key_ref_t key_create_or_update(key_ref_t keyring,
const char *type,
const char *description,
const void *payload,
size_t plen,
key_perm_t perm,
unsigned long flags);
extern int key_update(key_ref_t key,
const void *payload,
size_t plen);
extern int key_link(struct key *keyring,
struct key *key);
extern int key_move(struct key *key,
struct key *from_keyring,
struct key *to_keyring,
unsigned int flags);
extern int key_unlink(struct key *keyring,
struct key *key);
extern struct key *keyring_alloc(const char *description, kuid_t uid, kgid_t gid,
const struct cred *cred,
key_perm_t perm,
unsigned long flags,
struct key_restriction *restrict_link,
struct key *dest);
extern int restrict_link_reject(struct key *keyring,
const struct key_type *type,
const union key_payload *payload,
struct key *restriction_key);
extern int keyring_clear(struct key *keyring);
extern key_ref_t keyring_search(key_ref_t keyring,
struct key_type *type,
const char *description,
bool recurse);
extern int keyring_add_key(struct key *keyring,
struct key *key);
extern int keyring_restrict(key_ref_t keyring, const char *type,
const char *restriction);
extern struct key *key_lookup(key_serial_t id);
static inline key_serial_t key_serial(const struct key *key)
return key ? key->serial : 0;
extern void key_set_timeout(struct key *, unsigned);
extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags,
enum key_need_perm need_perm);
extern void key_free_user_ns(struct user_namespace *);
static inline short key_read_state(const struct key *key)
/* Barrier versus mark_key_instantiated(). */
return smp_load_acquire(&key->state);
* key_is_positive - Determine if a key has been positively instantiated
* @key: The key to check.
* Return true if the specified key has been positively instantiated, false
* otherwise.
static inline bool key_is_positive(const struct key *key)
return key_read_state(key) == KEY_IS_POSITIVE;
static inline bool key_is_negative(const struct key *key)
return key_read_state(key) < 0;
#define dereference_key_rcu(KEY) \
#define dereference_key_locked(KEY) \
(rcu_dereference_protected((KEY)->payload.rcu_data0, \
rwsem_is_locked(&((struct key *)(KEY))->sem)))
#define rcu_assign_keypointer(KEY, PAYLOAD) \
do { \
rcu_assign_pointer((KEY)->payload.rcu_data0, (PAYLOAD)); \
} while (0)
extern struct ctl_table key_sysctls[];
* the userspace interface
extern int install_thread_keyring_to_cred(struct cred *cred);
extern void key_fsuid_changed(struct cred *new_cred);
extern void key_fsgid_changed(struct cred *new_cred);
extern void key_init(void);
#else /* CONFIG_KEYS */
#define key_validate(k) 0
#define key_serial(k) 0
#define key_get(k) ({ NULL; })
#define key_revoke(k) do { } while(0)
#define key_invalidate(k) do { } while(0)
#define key_put(k) do { } while(0)
#define key_ref_put(k) do { } while(0)
#define make_key_ref(k, p) NULL
#define key_ref_to_ptr(k) NULL
#define is_key_possessed(k) 0
#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)
#define key_remove_domain(d) do { } while(0)
#endif /* CONFIG_KEYS */
#endif /* __KERNEL__ */
#endif /* _LINUX_KEY_H */