key.h

Go to the documentation of this file.

/* Authentication token and access key management
 *
 * Copyright (C) 2004, 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 *
 * See Documentation/security/keys.txt 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>

#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;

#ifdef CONFIG_KEYS

#undef KEY_DEBUGGING

#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

struct seq_file;
struct user_struct;
struct signal_struct;
struct cred;

struct key_type;
struct key_owner;
struct keyring_list;
struct keyring_name;

/*****************************************************************************/
/*
 * 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,
                     unsigned long 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 unsigned long is_key_possessed(const key_ref_t key_ref)
{
    return (unsigned long) key_ref & 1UL;
}

/*****************************************************************************/
/*
 * authentication token / access credential / keyring
 * - types of key include:
 *   - keyrings
 *   - disk encryption IDs
 *   - Kerberos TGTs and tickets
 */
struct key {
    atomic_t        usage;      /* number of references */
    key_serial_t        serial;     /* key serial number */
    union {
        struct list_head graveyard_link;
        struct rb_node  serial_node;
    };
    struct key_type     *type;      /* type of key */
    struct rw_semaphore sem;        /* change vs change sem */
    struct key_user     *user;      /* owner of this key */
    void            *security;  /* security data for this key */
    union {
        time_t      expiry;     /* time at which key expires (or 0) */
        time_t      revoked_at; /* time at which key was revoked */
    };
    time_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
                         */

#ifdef KEY_DEBUGGING
    unsigned        magic;
#define KEY_DEBUG_MAGIC     0x18273645u
#define KEY_DEBUG_MAGIC_X   0xf8e9dacbu
#endif

    unsigned long       flags;      /* status flags (change with bitops) */
#define KEY_FLAG_INSTANTIATED   0   /* set if key has been instantiated */
#define KEY_FLAG_DEAD       1   /* set if key type has been deleted */
#define KEY_FLAG_REVOKED    2   /* set if key had been revoked */
#define KEY_FLAG_IN_QUOTA   3   /* set if key consumes quota */
#define KEY_FLAG_USER_CONSTRUCT 4   /* set if key is being constructed in userspace */
#define KEY_FLAG_NEGATIVE   5   /* set if key is negative */
#define KEY_FLAG_ROOT_CAN_CLEAR 6   /* set if key can be cleared by root without permission */
#define KEY_FLAG_INVALIDATED    7   /* set if key has been invalidated */

    /* the description string
     * - this is used to match a key against search criteria
     * - this should be a printable string
     * - eg: for krb5 AFS, this might be "[email protected]"
     */
    char            *description;

    /* type specific data
     * - this is used by the keyring type to index the name
     */
    union {
        struct list_head    link;
        unsigned long       x[2];
        void            *p[2];
        int         reject_error;
    } type_data;

    /* key data
     * - this is used to hold the data actually used in cryptography or
     *   whatever
     */
    union {
        unsigned long       value;
        void __rcu      *rcudata;
        void            *data;
        struct keyring_list __rcu *subscriptions;
    } payload;
};

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);


#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 */

extern void key_revoke(struct key *key);
extern void key_invalidate(struct key *key);
extern void key_put(struct key *key);

static inline struct key *key_get(struct key *key)
{
    if (key)
        atomic_inc(&key->usage);
    return key;
}

static inline void key_ref_put(key_ref_t key_ref)
{
    key_put(key_ref_to_ptr(key_ref));
}

extern struct key *request_key(struct key_type *type,
                   const char *description,
                   const char *callout_info);

extern struct key *request_key_with_auxdata(struct key_type *type,
                        const char *description,
                        const void *callout_info,
                        size_t callout_len,
                        void *aux);

extern struct key *request_key_async(struct key_type *type,
                     const char *description,
                     const void *callout_info,
                     size_t callout_len);

extern struct key *request_key_async_with_auxdata(struct key_type *type,
                          const char *description,
                          const void *callout_info,
                          size_t callout_len,
                          void *aux);

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_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,
                 unsigned long flags,
                 struct key *dest);

extern int keyring_clear(struct key *keyring);

extern key_ref_t keyring_search(key_ref_t keyring,
                struct key_type *type,
                const char *description);

extern int keyring_add_key(struct key *keyring,
               struct key *key);

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);

static inline bool key_is_instantiated(const struct key *key)
{
    return test_bit(KEY_FLAG_INSTANTIATED, &key->flags) &&
        !test_bit(KEY_FLAG_NEGATIVE, &key->flags);
}

#define rcu_dereference_key(KEY)                    \
    (rcu_dereference_protected((KEY)->payload.rcudata,      \
                   rwsem_is_locked(&((struct key *)(KEY))->sem)))

#define rcu_assign_keypointer(KEY, PAYLOAD)             \
do {                                    \
    rcu_assign_pointer((KEY)->payload.rcudata, (PAYLOAD));      \
} while (0)

#ifdef CONFIG_SYSCTL
extern ctl_table key_sysctls[];
#endif
/*
 * the userspace interface
 */
extern int install_thread_keyring_to_cred(struct cred *cred);
extern void key_fsuid_changed(struct task_struct *tsk);
extern void key_fsgid_changed(struct task_struct *tsk);
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(t)        do { } while(0)
#define key_fsgid_changed(t)        do { } while(0)
#define key_init()          do { } while(0)

#endif /* CONFIG_KEYS */
#endif /* __KERNEL__ */
#endif /* _LINUX_KEY_H */