key-type.h

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/* Definitions for key type implementations
 *
 * Copyright (C) 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 Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#ifndef _LINUX_KEY_TYPE_H
#define _LINUX_KEY_TYPE_H

#include <linux/key.h>
#include <linux/errno.h>

#ifdef CONFIG_KEYS

/*
 * key under-construction record
 * - passed to the request_key actor if supplied
 */
struct key_construction {
    struct key  *key;   /* key being constructed */
    struct key  *authkey;/* authorisation for key being constructed */
};

/*
 * Pre-parsed payload, used by key add, update and instantiate.
 *
 * This struct will be cleared and data and datalen will be set with the data
 * and length parameters from the caller and quotalen will be set from
 * def_datalen from the key type.  Then if the preparse() op is provided by the
 * key type, that will be called.  Then the struct will be passed to the
 * instantiate() or the update() op.
 *
 * If the preparse() op is given, the free_preparse() op will be called to
 * clear the contents.
 */
struct key_preparsed_payload {
    char        *description;   /* Proposed key description (or NULL) */
    void        *type_data[2];  /* Private key-type data */
    void        *payload;   /* Proposed payload */
    const void  *data;      /* Raw data */
    size_t      datalen;    /* Raw datalen */
    size_t      quotalen;   /* Quota length for proposed payload */
};

typedef int (*request_key_actor_t)(struct key_construction *key,
                   const char *op, void *aux);

/*
 * kernel managed key type definition
 */
struct key_type {
    /* name of the type */
    const char *name;

    /* default payload length for quota precalculation (optional)
     * - this can be used instead of calling key_payload_reserve(), that
     *   function only needs to be called if the real datalen is different
     */
    size_t def_datalen;

    /* vet a description */
    int (*vet_description)(const char *description);

    /* Preparse the data blob from userspace that is to be the payload,
     * generating a proposed description and payload that will be handed to
     * the instantiate() and update() ops.
     */
    int (*preparse)(struct key_preparsed_payload *prep);

    /* Free a preparse data structure.
     */
    void (*free_preparse)(struct key_preparsed_payload *prep);

    /* instantiate a key of this type
     * - this method should call key_payload_reserve() to determine if the
     *   user's quota will hold the payload
     */
    int (*instantiate)(struct key *key, struct key_preparsed_payload *prep);

    /* update a key of this type (optional)
     * - this method should call key_payload_reserve() to recalculate the
     *   quota consumption
     * - the key must be locked against read when modifying
     */
    int (*update)(struct key *key, struct key_preparsed_payload *prep);

    /* match a key against a description */
    int (*match)(const struct key *key, const void *desc);

    /* clear some of the data from a key on revokation (optional)
     * - the key's semaphore will be write-locked by the caller
     */
    void (*revoke)(struct key *key);

    /* clear the data from a key (optional) */
    void (*destroy)(struct key *key);

    /* describe a key */
    void (*describe)(const struct key *key, struct seq_file *p);

    /* read a key's data (optional)
     * - permission checks will be done by the caller
     * - the key's semaphore will be readlocked by the caller
     * - should return the amount of data that could be read, no matter how
     *   much is copied into the buffer
     * - shouldn't do the copy if the buffer is NULL
     */
    long (*read)(const struct key *key, char __user *buffer, size_t buflen);

    /* handle request_key() for this type instead of invoking
     * /sbin/request-key (optional)
     * - key is the key to instantiate
     * - authkey is the authority to assume when instantiating this key
     * - op is the operation to be done, usually "create"
     * - the call must not return until the instantiation process has run
     *   its course
     */
    request_key_actor_t request_key;

    /* internal fields */
    struct list_head    link;       /* link in types list */
    struct lock_class_key   lock_class; /* key->sem lock class */
};

extern struct key_type key_type_keyring;

extern int register_key_type(struct key_type *ktype);
extern void unregister_key_type(struct key_type *ktype);

extern int key_payload_reserve(struct key *key, size_t datalen);
extern int key_instantiate_and_link(struct key *key,
                    const void *data,
                    size_t datalen,
                    struct key *keyring,
                    struct key *instkey);
extern int key_reject_and_link(struct key *key,
                   unsigned timeout,
                   unsigned error,
                   struct key *keyring,
                   struct key *instkey);
extern void complete_request_key(struct key_construction *cons, int error);

static inline int key_negate_and_link(struct key *key,
                      unsigned timeout,
                      struct key *keyring,
                      struct key *instkey)
{
    return key_reject_and_link(key, timeout, ENOKEY, keyring, instkey);
}

#endif /* CONFIG_KEYS */
#endif /* _LINUX_KEY_TYPE_H */