/* Authentication token and access key management
 *
 * Copyright (C) 2004, 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * 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/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;

#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;

struct keyring_index_key {
        struct key_type         *type;
        const char              *description;
        size_t                  desc_len;
};

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_UNINSTANTIATED,
        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 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 (-) */

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

        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 {
                        struct key_type *type;          /* type of key */
                        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);

static inline struct key *__key_get(struct key *key)
{
        refcount_inc(&key->usage);
        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)
{
        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,
                                 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);

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);

/*
 * The permissions required on a key that we're looking up.
 */
#define KEY_NEED_VIEW   0x01    /* Require permission to view attributes */
#define KEY_NEED_READ   0x02    /* Require permission to read content */
#define KEY_NEED_WRITE  0x04    /* Require permission to update / modify */
#define KEY_NEED_SEARCH 0x08    /* Require permission to search (keyring) or find (key) */
#define KEY_NEED_LINK   0x10    /* Require permission to link */
#define KEY_NEED_SETATTR 0x20   /* Require permission to change attributes */
#define KEY_NEED_ALL    0x3f    /* All the above permissions */

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)                                        \
        (rcu_dereference((KEY)->payload.rcu_data0))

#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)

#ifdef CONFIG_SYSCTL
extern struct 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 */