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linux-sg2042/security/keys/key.c

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/* key.c: basic authentication token and access key management
*
* Copyright (C) 2004 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.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <linux/err.h>
#include "internal.h"
static kmem_cache_t *key_jar;
static key_serial_t key_serial_next = 3;
struct rb_root key_serial_tree; /* tree of keys indexed by serial */
DEFINE_SPINLOCK(key_serial_lock);
struct rb_root key_user_tree; /* tree of quota records indexed by UID */
DEFINE_SPINLOCK(key_user_lock);
static LIST_HEAD(key_types_list);
static DECLARE_RWSEM(key_types_sem);
static void key_cleanup(void *data);
static DECLARE_WORK(key_cleanup_task, key_cleanup, NULL);
/* we serialise key instantiation and link */
DECLARE_RWSEM(key_construction_sem);
/* any key who's type gets unegistered will be re-typed to this */
struct key_type key_type_dead = {
.name = "dead",
};
#ifdef KEY_DEBUGGING
void __key_check(const struct key *key)
{
printk("__key_check: key %p {%08x} should be {%08x}\n",
key, key->magic, KEY_DEBUG_MAGIC);
BUG();
}
#endif
/*****************************************************************************/
/*
* get the key quota record for a user, allocating a new record if one doesn't
* already exist
*/
struct key_user *key_user_lookup(uid_t uid)
{
struct key_user *candidate = NULL, *user;
struct rb_node *parent = NULL;
struct rb_node **p;
try_again:
p = &key_user_tree.rb_node;
spin_lock(&key_user_lock);
/* search the tree for a user record with a matching UID */
while (*p) {
parent = *p;
user = rb_entry(parent, struct key_user, node);
if (uid < user->uid)
p = &(*p)->rb_left;
else if (uid > user->uid)
p = &(*p)->rb_right;
else
goto found;
}
/* if we get here, we failed to find a match in the tree */
if (!candidate) {
/* allocate a candidate user record if we don't already have
* one */
spin_unlock(&key_user_lock);
user = NULL;
candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
if (unlikely(!candidate))
goto out;
/* the allocation may have scheduled, so we need to repeat the
* search lest someone else added the record whilst we were
* asleep */
goto try_again;
}
/* if we get here, then the user record still hadn't appeared on the
* second pass - so we use the candidate record */
atomic_set(&candidate->usage, 1);
atomic_set(&candidate->nkeys, 0);
atomic_set(&candidate->nikeys, 0);
candidate->uid = uid;
candidate->qnkeys = 0;
candidate->qnbytes = 0;
spin_lock_init(&candidate->lock);
INIT_LIST_HEAD(&candidate->consq);
rb_link_node(&candidate->node, parent, p);
rb_insert_color(&candidate->node, &key_user_tree);
spin_unlock(&key_user_lock);
user = candidate;
goto out;
/* okay - we found a user record for this UID */
found:
atomic_inc(&user->usage);
spin_unlock(&key_user_lock);
if (candidate)
kfree(candidate);
out:
return user;
} /* end key_user_lookup() */
/*****************************************************************************/
/*
* dispose of a user structure
*/
void key_user_put(struct key_user *user)
{
if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
rb_erase(&user->node, &key_user_tree);
spin_unlock(&key_user_lock);
kfree(user);
}
} /* end key_user_put() */
/*****************************************************************************/
/*
* insert a key with a fixed serial number
*/
static void __init __key_insert_serial(struct key *key)
{
struct rb_node *parent, **p;
struct key *xkey;
parent = NULL;
p = &key_serial_tree.rb_node;
while (*p) {
parent = *p;
xkey = rb_entry(parent, struct key, serial_node);
if (key->serial < xkey->serial)
p = &(*p)->rb_left;
else if (key->serial > xkey->serial)
p = &(*p)->rb_right;
else
BUG();
}
/* we've found a suitable hole - arrange for this key to occupy it */
rb_link_node(&key->serial_node, parent, p);
rb_insert_color(&key->serial_node, &key_serial_tree);
} /* end __key_insert_serial() */
/*****************************************************************************/
/*
* assign a key the next unique serial number
* - we work through all the serial numbers between 2 and 2^31-1 in turn and
* then wrap
*/
static inline void key_alloc_serial(struct key *key)
{
struct rb_node *parent, **p;
struct key *xkey;
spin_lock(&key_serial_lock);
/* propose a likely serial number and look for a hole for it in the
* serial number tree */
key->serial = key_serial_next;
if (key->serial < 3)
key->serial = 3;
key_serial_next = key->serial + 1;
parent = NULL;
p = &key_serial_tree.rb_node;
while (*p) {
parent = *p;
xkey = rb_entry(parent, struct key, serial_node);
if (key->serial < xkey->serial)
p = &(*p)->rb_left;
else if (key->serial > xkey->serial)
p = &(*p)->rb_right;
else
goto serial_exists;
}
goto insert_here;
/* we found a key with the proposed serial number - walk the tree from
* that point looking for the next unused serial number */
serial_exists:
for (;;) {
key->serial = key_serial_next;
if (key->serial < 2)
key->serial = 2;
key_serial_next = key->serial + 1;
if (!parent->rb_parent)
p = &key_serial_tree.rb_node;
else if (parent->rb_parent->rb_left == parent)
p = &parent->rb_parent->rb_left;
else
p = &parent->rb_parent->rb_right;
parent = rb_next(parent);
if (!parent)
break;
xkey = rb_entry(parent, struct key, serial_node);
if (key->serial < xkey->serial)
goto insert_here;
}
/* we've found a suitable hole - arrange for this key to occupy it */
insert_here:
rb_link_node(&key->serial_node, parent, p);
rb_insert_color(&key->serial_node, &key_serial_tree);
spin_unlock(&key_serial_lock);
} /* end key_alloc_serial() */
/*****************************************************************************/
/*
* allocate a key of the specified type
* - update the user's quota to reflect the existence of the key
* - called from a key-type operation with key_types_sem read-locked by either
* key_create_or_update() or by key_duplicate(); this prevents unregistration
* of the key type
* - upon return the key is as yet uninstantiated; the caller needs to either
* instantiate the key or discard it before returning
*/
struct key *key_alloc(struct key_type *type, const char *desc,
uid_t uid, gid_t gid, key_perm_t perm,
int not_in_quota)
{
struct key_user *user = NULL;
struct key *key;
size_t desclen, quotalen;
key = ERR_PTR(-EINVAL);
if (!desc || !*desc)
goto error;
desclen = strlen(desc) + 1;
quotalen = desclen + type->def_datalen;
/* get hold of the key tracking for this user */
user = key_user_lookup(uid);
if (!user)
goto no_memory_1;
/* check that the user's quota permits allocation of another key and
* its description */
if (!not_in_quota) {
spin_lock(&user->lock);
if (user->qnkeys + 1 >= KEYQUOTA_MAX_KEYS &&
user->qnbytes + quotalen >= KEYQUOTA_MAX_BYTES
)
goto no_quota;
user->qnkeys++;
user->qnbytes += quotalen;
spin_unlock(&user->lock);
}
/* allocate and initialise the key and its description */
key = kmem_cache_alloc(key_jar, SLAB_KERNEL);
if (!key)
goto no_memory_2;
if (desc) {
key->description = kmalloc(desclen, GFP_KERNEL);
if (!key->description)
goto no_memory_3;
memcpy(key->description, desc, desclen);
}
atomic_set(&key->usage, 1);
rwlock_init(&key->lock);
init_rwsem(&key->sem);
key->type = type;
key->user = user;
key->quotalen = quotalen;
key->datalen = type->def_datalen;
key->uid = uid;
key->gid = gid;
key->perm = perm;
key->flags = 0;
key->expiry = 0;
key->payload.data = NULL;
if (!not_in_quota)
key->flags |= KEY_FLAG_IN_QUOTA;
memset(&key->type_data, 0, sizeof(key->type_data));
#ifdef KEY_DEBUGGING
key->magic = KEY_DEBUG_MAGIC;
#endif
/* publish the key by giving it a serial number */
atomic_inc(&user->nkeys);
key_alloc_serial(key);
error:
return key;
no_memory_3:
kmem_cache_free(key_jar, key);
no_memory_2:
if (!not_in_quota) {
spin_lock(&user->lock);
user->qnkeys--;
user->qnbytes -= quotalen;
spin_unlock(&user->lock);
}
key_user_put(user);
no_memory_1:
key = ERR_PTR(-ENOMEM);
goto error;
no_quota:
spin_unlock(&user->lock);
key_user_put(user);
key = ERR_PTR(-EDQUOT);
goto error;
} /* end key_alloc() */
EXPORT_SYMBOL(key_alloc);
/*****************************************************************************/
/*
* reserve an amount of quota for the key's payload
*/
int key_payload_reserve(struct key *key, size_t datalen)
{
int delta = (int) datalen - key->datalen;
int ret = 0;
key_check(key);
/* contemplate the quota adjustment */
if (delta != 0 && key->flags & KEY_FLAG_IN_QUOTA) {
spin_lock(&key->user->lock);
if (delta > 0 &&
key->user->qnbytes + delta > KEYQUOTA_MAX_BYTES
) {
ret = -EDQUOT;
}
else {
key->user->qnbytes += delta;
key->quotalen += delta;
}
spin_unlock(&key->user->lock);
}
/* change the recorded data length if that didn't generate an error */
if (ret == 0)
key->datalen = datalen;
return ret;
} /* end key_payload_reserve() */
EXPORT_SYMBOL(key_payload_reserve);
/*****************************************************************************/
/*
* instantiate a key and link it into the target keyring atomically
* - called with the target keyring's semaphore writelocked
*/
static int __key_instantiate_and_link(struct key *key,
const void *data,
size_t datalen,
struct key *keyring)
{
int ret, awaken;
key_check(key);
key_check(keyring);
awaken = 0;
ret = -EBUSY;
down_write(&key_construction_sem);
/* can't instantiate twice */
if (!(key->flags & KEY_FLAG_INSTANTIATED)) {
/* instantiate the key */
ret = key->type->instantiate(key, data, datalen);
if (ret == 0) {
/* mark the key as being instantiated */
write_lock(&key->lock);
atomic_inc(&key->user->nikeys);
key->flags |= KEY_FLAG_INSTANTIATED;
if (key->flags & KEY_FLAG_USER_CONSTRUCT) {
key->flags &= ~KEY_FLAG_USER_CONSTRUCT;
awaken = 1;
}
write_unlock(&key->lock);
/* and link it into the destination keyring */
if (keyring)
ret = __key_link(keyring, key);
}
}
up_write(&key_construction_sem);
/* wake up anyone waiting for a key to be constructed */
if (awaken)
wake_up_all(&request_key_conswq);
return ret;
} /* end __key_instantiate_and_link() */
/*****************************************************************************/
/*
* instantiate a key and link it into the target keyring atomically
*/
int key_instantiate_and_link(struct key *key,
const void *data,
size_t datalen,
struct key *keyring)
{
int ret;
if (keyring)
down_write(&keyring->sem);
ret = __key_instantiate_and_link(key, data, datalen, keyring);
if (keyring)
up_write(&keyring->sem);
return ret;
} /* end key_instantiate_and_link() */
EXPORT_SYMBOL(key_instantiate_and_link);
/*****************************************************************************/
/*
* negatively instantiate a key and link it into the target keyring atomically
*/
int key_negate_and_link(struct key *key,
unsigned timeout,
struct key *keyring)
{
struct timespec now;
int ret, awaken;
key_check(key);
key_check(keyring);
awaken = 0;
ret = -EBUSY;
if (keyring)
down_write(&keyring->sem);
down_write(&key_construction_sem);
/* can't instantiate twice */
if (!(key->flags & KEY_FLAG_INSTANTIATED)) {
/* mark the key as being negatively instantiated */
write_lock(&key->lock);
atomic_inc(&key->user->nikeys);
key->flags |= KEY_FLAG_INSTANTIATED | KEY_FLAG_NEGATIVE;
now = current_kernel_time();
key->expiry = now.tv_sec + timeout;
if (key->flags & KEY_FLAG_USER_CONSTRUCT) {
key->flags &= ~KEY_FLAG_USER_CONSTRUCT;
awaken = 1;
}
write_unlock(&key->lock);
ret = 0;
/* and link it into the destination keyring */
if (keyring)
ret = __key_link(keyring, key);
}
up_write(&key_construction_sem);
if (keyring)
up_write(&keyring->sem);
/* wake up anyone waiting for a key to be constructed */
if (awaken)
wake_up_all(&request_key_conswq);
return ret;
} /* end key_negate_and_link() */
EXPORT_SYMBOL(key_negate_and_link);
/*****************************************************************************/
/*
* do cleaning up in process context so that we don't have to disable
* interrupts all over the place
*/
static void key_cleanup(void *data)
{
struct rb_node *_n;
struct key *key;
go_again:
/* look for a dead key in the tree */
spin_lock(&key_serial_lock);
for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
key = rb_entry(_n, struct key, serial_node);
if (atomic_read(&key->usage) == 0)
goto found_dead_key;
}
spin_unlock(&key_serial_lock);
return;
found_dead_key:
/* we found a dead key - once we've removed it from the tree, we can
* drop the lock */
rb_erase(&key->serial_node, &key_serial_tree);
spin_unlock(&key_serial_lock);
/* deal with the user's key tracking and quota */
if (key->flags & KEY_FLAG_IN_QUOTA) {
spin_lock(&key->user->lock);
key->user->qnkeys--;
key->user->qnbytes -= key->quotalen;
spin_unlock(&key->user->lock);
}
atomic_dec(&key->user->nkeys);
if (key->flags & KEY_FLAG_INSTANTIATED)
atomic_dec(&key->user->nikeys);
key_user_put(key->user);
/* now throw away the key memory */
if (key->type->destroy)
key->type->destroy(key);
kfree(key->description);
#ifdef KEY_DEBUGGING
key->magic = KEY_DEBUG_MAGIC_X;
#endif
kmem_cache_free(key_jar, key);
/* there may, of course, be more than one key to destroy */
goto go_again;
} /* end key_cleanup() */
/*****************************************************************************/
/*
* dispose of a reference to a key
* - when all the references are gone, we schedule the cleanup task to come and
* pull it out of the tree in definite process context
*/
void key_put(struct key *key)
{
if (key) {
key_check(key);
if (atomic_dec_and_test(&key->usage))
schedule_work(&key_cleanup_task);
}
} /* end key_put() */
EXPORT_SYMBOL(key_put);
/*****************************************************************************/
/*
* find a key by its serial number
*/
struct key *key_lookup(key_serial_t id)
{
struct rb_node *n;
struct key *key;
spin_lock(&key_serial_lock);
/* search the tree for the specified key */
n = key_serial_tree.rb_node;
while (n) {
key = rb_entry(n, struct key, serial_node);
if (id < key->serial)
n = n->rb_left;
else if (id > key->serial)
n = n->rb_right;
else
goto found;
}
not_found:
key = ERR_PTR(-ENOKEY);
goto error;
found:
/* pretent doesn't exist if it's dead */
if (atomic_read(&key->usage) == 0 ||
(key->flags & KEY_FLAG_DEAD) ||
key->type == &key_type_dead)
goto not_found;
/* this races with key_put(), but that doesn't matter since key_put()
* doesn't actually change the key
*/
atomic_inc(&key->usage);
error:
spin_unlock(&key_serial_lock);
return key;
} /* end key_lookup() */
/*****************************************************************************/
/*
* find and lock the specified key type against removal
* - we return with the sem readlocked
*/
struct key_type *key_type_lookup(const char *type)
{
struct key_type *ktype;
down_read(&key_types_sem);
/* look up the key type to see if it's one of the registered kernel
* types */
list_for_each_entry(ktype, &key_types_list, link) {
if (strcmp(ktype->name, type) == 0)
goto found_kernel_type;
}
up_read(&key_types_sem);
ktype = ERR_PTR(-ENOKEY);
found_kernel_type:
return ktype;
} /* end key_type_lookup() */
/*****************************************************************************/
/*
* unlock a key type
*/
void key_type_put(struct key_type *ktype)
{
up_read(&key_types_sem);
} /* end key_type_put() */
/*****************************************************************************/
/*
* attempt to update an existing key
* - the key has an incremented refcount
* - we need to put the key if we get an error
*/
static inline struct key *__key_update(struct key *key, const void *payload,
size_t plen)
{
int ret;
/* need write permission on the key to update it */
ret = -EACCES;
if (!key_permission(key, KEY_WRITE))
goto error;
ret = -EEXIST;
if (!key->type->update)
goto error;
down_write(&key->sem);
ret = key->type->update(key, payload, plen);
if (ret == 0) {
/* updating a negative key instantiates it */
write_lock(&key->lock);
key->flags &= ~KEY_FLAG_NEGATIVE;
write_unlock(&key->lock);
}
up_write(&key->sem);
if (ret < 0)
goto error;
out:
return key;
error:
key_put(key);
key = ERR_PTR(ret);
goto out;
} /* end __key_update() */
/*****************************************************************************/
/*
* search the specified keyring for a key of the same description; if one is
* found, update it, otherwise add a new one
*/
struct key *key_create_or_update(struct key *keyring,
const char *type,
const char *description,
const void *payload,
size_t plen,
int not_in_quota)
{
struct key_type *ktype;
struct key *key = NULL;
key_perm_t perm;
int ret;
key_check(keyring);
/* look up the key type to see if it's one of the registered kernel
* types */
ktype = key_type_lookup(type);
if (IS_ERR(ktype)) {
key = ERR_PTR(-ENODEV);
goto error;
}
ret = -EINVAL;
if (!ktype->match || !ktype->instantiate)
goto error_2;
/* search for an existing key of the same type and description in the
* destination keyring
*/
down_write(&keyring->sem);
key = __keyring_search_one(keyring, ktype, description, 0);
if (!IS_ERR(key))
goto found_matching_key;
/* if we're going to allocate a new key, we're going to have to modify
* the keyring */
ret = -EACCES;
if (!key_permission(keyring, KEY_WRITE))
goto error_3;
/* decide on the permissions we want */
perm = KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK;
if (ktype->read)
perm |= KEY_USR_READ;
if (ktype == &key_type_keyring || ktype->update)
perm |= KEY_USR_WRITE;
/* allocate a new key */
key = key_alloc(ktype, description, current->fsuid, current->fsgid,
perm, not_in_quota);
if (IS_ERR(key)) {
ret = PTR_ERR(key);
goto error_3;
}
/* instantiate it and link it into the target keyring */
ret = __key_instantiate_and_link(key, payload, plen, keyring);
if (ret < 0) {
key_put(key);
key = ERR_PTR(ret);
}
error_3:
up_write(&keyring->sem);
error_2:
key_type_put(ktype);
error:
return key;
found_matching_key:
/* we found a matching key, so we're going to try to update it
* - we can drop the locks first as we have the key pinned
*/
up_write(&keyring->sem);
key_type_put(ktype);
key = __key_update(key, payload, plen);
goto error;
} /* end key_create_or_update() */
EXPORT_SYMBOL(key_create_or_update);
/*****************************************************************************/
/*
* update a key
*/
int key_update(struct key *key, const void *payload, size_t plen)
{
int ret;
key_check(key);
/* the key must be writable */
ret = -EACCES;
if (!key_permission(key, KEY_WRITE))
goto error;
/* attempt to update it if supported */
ret = -EOPNOTSUPP;
if (key->type->update) {
down_write(&key->sem);
ret = key->type->update(key, payload, plen);
if (ret == 0) {
/* updating a negative key instantiates it */
write_lock(&key->lock);
key->flags &= ~KEY_FLAG_NEGATIVE;
write_unlock(&key->lock);
}
up_write(&key->sem);
}
error:
return ret;
} /* end key_update() */
EXPORT_SYMBOL(key_update);
/*****************************************************************************/
/*
* duplicate a key, potentially with a revised description
* - must be supported by the keytype (keyrings for instance can be duplicated)
*/
struct key *key_duplicate(struct key *source, const char *desc)
{
struct key *key;
int ret;
key_check(source);
if (!desc)
desc = source->description;
down_read(&key_types_sem);
ret = -EINVAL;
if (!source->type->duplicate)
goto error;
/* allocate and instantiate a key */
key = key_alloc(source->type, desc, current->fsuid, current->fsgid,
source->perm, 0);
if (IS_ERR(key))
goto error_k;
down_read(&source->sem);
ret = key->type->duplicate(key, source);
up_read(&source->sem);
if (ret < 0)
goto error2;
atomic_inc(&key->user->nikeys);
write_lock(&key->lock);
key->flags |= KEY_FLAG_INSTANTIATED;
write_unlock(&key->lock);
error_k:
up_read(&key_types_sem);
out:
return key;
error2:
key_put(key);
error:
up_read(&key_types_sem);
key = ERR_PTR(ret);
goto out;
} /* end key_duplicate() */
/*****************************************************************************/
/*
* revoke a key
*/
void key_revoke(struct key *key)
{
key_check(key);
/* make sure no one's trying to change or use the key when we mark
* it */
down_write(&key->sem);
write_lock(&key->lock);
key->flags |= KEY_FLAG_REVOKED;
write_unlock(&key->lock);
up_write(&key->sem);
} /* end key_revoke() */
EXPORT_SYMBOL(key_revoke);
/*****************************************************************************/
/*
* register a type of key
*/
int register_key_type(struct key_type *ktype)
{
struct key_type *p;
int ret;
ret = -EEXIST;
down_write(&key_types_sem);
/* disallow key types with the same name */
list_for_each_entry(p, &key_types_list, link) {
if (strcmp(p->name, ktype->name) == 0)
goto out;
}
/* store the type */
list_add(&ktype->link, &key_types_list);
ret = 0;
out:
up_write(&key_types_sem);
return ret;
} /* end register_key_type() */
EXPORT_SYMBOL(register_key_type);
/*****************************************************************************/
/*
* unregister a type of key
*/
void unregister_key_type(struct key_type *ktype)
{
struct rb_node *_n;
struct key *key;
down_write(&key_types_sem);
/* withdraw the key type */
list_del_init(&ktype->link);
/* need to withdraw all keys of this type */
spin_lock(&key_serial_lock);
for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
key = rb_entry(_n, struct key, serial_node);
if (key->type != ktype)
continue;
write_lock(&key->lock);
key->type = &key_type_dead;
write_unlock(&key->lock);
/* there shouldn't be anyone looking at the description or
* payload now */
if (ktype->destroy)
ktype->destroy(key);
memset(&key->payload, 0xbd, sizeof(key->payload));
}
spin_unlock(&key_serial_lock);
up_write(&key_types_sem);
} /* end unregister_key_type() */
EXPORT_SYMBOL(unregister_key_type);
/*****************************************************************************/
/*
* initialise the key management stuff
*/
void __init key_init(void)
{
/* allocate a slab in which we can store keys */
key_jar = kmem_cache_create("key_jar", sizeof(struct key),
0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
/* add the special key types */
list_add_tail(&key_type_keyring.link, &key_types_list);
list_add_tail(&key_type_dead.link, &key_types_list);
list_add_tail(&key_type_user.link, &key_types_list);
/* record the root user tracking */
rb_link_node(&root_key_user.node,
NULL,
&key_user_tree.rb_node);
rb_insert_color(&root_key_user.node,
&key_user_tree);
/* record root's user standard keyrings */
key_check(&root_user_keyring);
key_check(&root_session_keyring);
__key_insert_serial(&root_user_keyring);
__key_insert_serial(&root_session_keyring);
keyring_publish_name(&root_user_keyring);
keyring_publish_name(&root_session_keyring);
/* link the two root keyrings together */
key_link(&root_session_keyring, &root_user_keyring);
} /* end key_init() */
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