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76d8aeabfe
The attached patch changes the key implementation in a number of ways: (1) It removes the spinlock from the key structure. (2) The key flags are now accessed using atomic bitops instead of write-locking the key spinlock and using C bitwise operators. The three instantiation flags are dealt with with the construction semaphore held during the request_key/instantiate/negate sequence, thus rendering the spinlock superfluous. The key flags are also now bit numbers not bit masks. (3) The key payload is now accessed using RCU. This permits the recursive keyring search algorithm to be simplified greatly since no locks need be taken other than the usual RCU preemption disablement. Searching now does not require any locks or semaphores to be held; merely that the starting keyring be pinned. (4) The keyring payload now includes an RCU head so that it can be disposed of by call_rcu(). This requires that the payload be copied on unlink to prevent introducing races in copy-down vs search-up. (5) The user key payload is now a structure with the data following it. It includes an RCU head like the keyring payload and for the same reason. It also contains a data length because the data length in the key may be changed on another CPU whilst an RCU protected read is in progress on the payload. This would then see the supposed RCU payload and the on-key data length getting out of sync. I'm tempted to drop the key's datalen entirely, except that it's used in conjunction with quota management and so is a little tricky to get rid of. (6) Update the keys documentation. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
297 lines
9.0 KiB
C
297 lines
9.0 KiB
C
/* key.h: authentication token and access key management
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*
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* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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*
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* See Documentation/keys.txt for information on keys/keyrings.
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*/
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#ifndef _LINUX_KEY_H
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#define _LINUX_KEY_H
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#include <linux/types.h>
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#include <linux/list.h>
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#include <linux/rbtree.h>
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#include <linux/rcupdate.h>
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#include <asm/atomic.h>
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#ifdef __KERNEL__
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/* key handle serial number */
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typedef int32_t key_serial_t;
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/* key handle permissions mask */
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typedef uint32_t key_perm_t;
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struct key;
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#ifdef CONFIG_KEYS
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#undef KEY_DEBUGGING
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#define KEY_USR_VIEW 0x00010000 /* user can view a key's attributes */
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#define KEY_USR_READ 0x00020000 /* user can read key payload / view keyring */
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#define KEY_USR_WRITE 0x00040000 /* user can update key payload / add link to keyring */
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#define KEY_USR_SEARCH 0x00080000 /* user can find a key in search / search a keyring */
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#define KEY_USR_LINK 0x00100000 /* user can create a link to a key/keyring */
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#define KEY_USR_ALL 0x001f0000
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#define KEY_GRP_VIEW 0x00000100 /* group permissions... */
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#define KEY_GRP_READ 0x00000200
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#define KEY_GRP_WRITE 0x00000400
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#define KEY_GRP_SEARCH 0x00000800
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#define KEY_GRP_LINK 0x00001000
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#define KEY_GRP_ALL 0x00001f00
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#define KEY_OTH_VIEW 0x00000001 /* third party permissions... */
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#define KEY_OTH_READ 0x00000002
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#define KEY_OTH_WRITE 0x00000004
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#define KEY_OTH_SEARCH 0x00000008
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#define KEY_OTH_LINK 0x00000010
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#define KEY_OTH_ALL 0x0000001f
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struct seq_file;
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struct user_struct;
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struct signal_struct;
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struct key_type;
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struct key_owner;
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struct keyring_list;
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struct keyring_name;
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/*****************************************************************************/
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/*
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* authentication token / access credential / keyring
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* - types of key include:
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* - keyrings
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* - disk encryption IDs
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* - Kerberos TGTs and tickets
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*/
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struct key {
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atomic_t usage; /* number of references */
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key_serial_t serial; /* key serial number */
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struct rb_node serial_node;
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struct key_type *type; /* type of key */
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struct rw_semaphore sem; /* change vs change sem */
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struct key_user *user; /* owner of this key */
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time_t expiry; /* time at which key expires (or 0) */
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uid_t uid;
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gid_t gid;
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key_perm_t perm; /* access permissions */
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unsigned short quotalen; /* length added to quota */
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unsigned short datalen; /* payload data length
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* - may not match RCU dereferenced payload
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* - payload should contain own length
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*/
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#ifdef KEY_DEBUGGING
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unsigned magic;
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#define KEY_DEBUG_MAGIC 0x18273645u
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#define KEY_DEBUG_MAGIC_X 0xf8e9dacbu
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#endif
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unsigned long flags; /* status flags (change with bitops) */
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#define KEY_FLAG_INSTANTIATED 0 /* set if key has been instantiated */
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#define KEY_FLAG_DEAD 1 /* set if key type has been deleted */
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#define KEY_FLAG_REVOKED 2 /* set if key had been revoked */
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#define KEY_FLAG_IN_QUOTA 3 /* set if key consumes quota */
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#define KEY_FLAG_USER_CONSTRUCT 4 /* set if key is being constructed in userspace */
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#define KEY_FLAG_NEGATIVE 5 /* set if key is negative */
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/* the description string
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* - this is used to match a key against search criteria
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* - this should be a printable string
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* - eg: for krb5 AFS, this might be "afs@REDHAT.COM"
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*/
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char *description;
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/* type specific data
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* - this is used by the keyring type to index the name
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*/
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union {
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struct list_head link;
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} type_data;
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/* key data
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* - this is used to hold the data actually used in cryptography or
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* whatever
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*/
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union {
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unsigned long value;
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void *data;
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struct keyring_list *subscriptions;
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} payload;
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};
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/*****************************************************************************/
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/*
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* kernel managed key type definition
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*/
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struct key_type {
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/* name of the type */
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const char *name;
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/* default payload length for quota precalculation (optional)
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* - this can be used instead of calling key_payload_reserve(), that
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* function only needs to be called if the real datalen is different
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*/
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size_t def_datalen;
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/* instantiate a key of this type
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* - this method should call key_payload_reserve() to determine if the
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* user's quota will hold the payload
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*/
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int (*instantiate)(struct key *key, const void *data, size_t datalen);
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/* duplicate a key of this type (optional)
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* - the source key will be locked against change
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* - the new description will be attached
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* - the quota will have been adjusted automatically from
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* source->quotalen
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*/
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int (*duplicate)(struct key *key, const struct key *source);
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/* update a key of this type (optional)
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* - this method should call key_payload_reserve() to recalculate the
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* quota consumption
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* - the key must be locked against read when modifying
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*/
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int (*update)(struct key *key, const void *data, size_t datalen);
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/* match a key against a description */
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int (*match)(const struct key *key, const void *desc);
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/* clear the data from a key (optional) */
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void (*destroy)(struct key *key);
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/* describe a key */
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void (*describe)(const struct key *key, struct seq_file *p);
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/* read a key's data (optional)
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* - permission checks will be done by the caller
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* - the key's semaphore will be readlocked by the caller
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* - should return the amount of data that could be read, no matter how
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* much is copied into the buffer
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* - shouldn't do the copy if the buffer is NULL
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*/
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long (*read)(const struct key *key, char __user *buffer, size_t buflen);
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/* internal fields */
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struct list_head link; /* link in types list */
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};
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extern struct key_type key_type_keyring;
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extern int register_key_type(struct key_type *ktype);
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extern void unregister_key_type(struct key_type *ktype);
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extern struct key *key_alloc(struct key_type *type,
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const char *desc,
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uid_t uid, gid_t gid, key_perm_t perm,
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int not_in_quota);
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extern int key_payload_reserve(struct key *key, size_t datalen);
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extern int key_instantiate_and_link(struct key *key,
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const void *data,
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size_t datalen,
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struct key *keyring);
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extern int key_negate_and_link(struct key *key,
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unsigned timeout,
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struct key *keyring);
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extern void key_revoke(struct key *key);
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extern void key_put(struct key *key);
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static inline struct key *key_get(struct key *key)
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{
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if (key)
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atomic_inc(&key->usage);
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return key;
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}
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extern struct key *request_key(struct key_type *type,
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const char *description,
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const char *callout_info);
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extern int key_validate(struct key *key);
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extern struct key *key_create_or_update(struct key *keyring,
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const char *type,
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const char *description,
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const void *payload,
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size_t plen,
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int not_in_quota);
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extern int key_update(struct key *key,
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const void *payload,
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size_t plen);
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extern int key_link(struct key *keyring,
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struct key *key);
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extern int key_unlink(struct key *keyring,
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struct key *key);
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extern struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
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int not_in_quota, struct key *dest);
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extern int keyring_clear(struct key *keyring);
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extern struct key *keyring_search(struct key *keyring,
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struct key_type *type,
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const char *description);
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extern struct key *search_process_keyrings(struct key_type *type,
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const char *description);
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extern int keyring_add_key(struct key *keyring,
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struct key *key);
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extern struct key *key_lookup(key_serial_t id);
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extern void keyring_replace_payload(struct key *key, void *replacement);
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#define key_serial(key) ((key) ? (key)->serial : 0)
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/*
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* the userspace interface
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*/
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extern struct key root_user_keyring, root_session_keyring;
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extern int alloc_uid_keyring(struct user_struct *user);
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extern void switch_uid_keyring(struct user_struct *new_user);
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extern int copy_keys(unsigned long clone_flags, struct task_struct *tsk);
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extern int copy_thread_group_keys(struct task_struct *tsk);
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extern void exit_keys(struct task_struct *tsk);
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extern void exit_thread_group_keys(struct signal_struct *tg);
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extern int suid_keys(struct task_struct *tsk);
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extern int exec_keys(struct task_struct *tsk);
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extern void key_fsuid_changed(struct task_struct *tsk);
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extern void key_fsgid_changed(struct task_struct *tsk);
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extern void key_init(void);
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#else /* CONFIG_KEYS */
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#define key_validate(k) 0
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#define key_serial(k) 0
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#define key_get(k) NULL
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#define key_put(k) do { } while(0)
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#define alloc_uid_keyring(u) 0
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#define switch_uid_keyring(u) do { } while(0)
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#define copy_keys(f,t) 0
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#define copy_thread_group_keys(t) 0
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#define exit_keys(t) do { } while(0)
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#define exit_thread_group_keys(tg) do { } while(0)
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#define suid_keys(t) do { } while(0)
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#define exec_keys(t) do { } while(0)
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#define key_fsuid_changed(t) do { } while(0)
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#define key_fsgid_changed(t) do { } while(0)
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#define key_init() do { } while(0)
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#endif /* CONFIG_KEYS */
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#endif /* __KERNEL__ */
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#endif /* _LINUX_KEY_H */
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