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alistair23-linux/security/keys/key.c
David Howells d84f4f992c CRED: Inaugurate COW credentials 
Inaugurate copy-on-write credentials management.  This uses RCU to manage the
credentials pointer in the task_struct with respect to accesses by other tasks.
A process may only modify its own credentials, and so does not need locking to
access or modify its own credentials.

A mutex (cred_replace_mutex) is added to the task_struct to control the effect
of PTRACE_ATTACHED on credential calculations, particularly with respect to
execve().

With this patch, the contents of an active credentials struct may not be
changed directly; rather a new set of credentials must be prepared, modified
and committed using something like the following sequence of events:

	struct cred *new = prepare_creds();
	int ret = blah(new);
	if (ret < 0) {
		abort_creds(new);
		return ret;
	}
	return commit_creds(new);

There are some exceptions to this rule: the keyrings pointed to by the active
credentials may be instantiated - keyrings violate the COW rule as managing
COW keyrings is tricky, given that it is possible for a task to directly alter
the keys in a keyring in use by another task.

To help enforce this, various pointers to sets of credentials, such as those in
the task_struct, are declared const.  The purpose of this is compile-time
discouragement of altering credentials through those pointers.  Once a set of
credentials has been made public through one of these pointers, it may not be
modified, except under special circumstances:

  (1) Its reference count may incremented and decremented.

  (2) The keyrings to which it points may be modified, but not replaced.

The only safe way to modify anything else is to create a replacement and commit
using the functions described in Documentation/credentials.txt (which will be
added by a later patch).

This patch and the preceding patches have been tested with the LTP SELinux
testsuite.

This patch makes several logical sets of alteration:

 (1) execve().

     This now prepares and commits credentials in various places in the
     security code rather than altering the current creds directly.

 (2) Temporary credential overrides.

     do_coredump() and sys_faccessat() now prepare their own credentials and
     temporarily override the ones currently on the acting thread, whilst
     preventing interference from other threads by holding cred_replace_mutex
     on the thread being dumped.

     This will be replaced in a future patch by something that hands down the
     credentials directly to the functions being called, rather than altering
     the task's objective credentials.

 (3) LSM interface.

     A number of functions have been changed, added or removed:

     (*) security_capset_check(), ->capset_check()
     (*) security_capset_set(), ->capset_set()

     	 Removed in favour of security_capset().

     (*) security_capset(), ->capset()

     	 New.  This is passed a pointer to the new creds, a pointer to the old
     	 creds and the proposed capability sets.  It should fill in the new
     	 creds or return an error.  All pointers, barring the pointer to the
     	 new creds, are now const.

     (*) security_bprm_apply_creds(), ->bprm_apply_creds()

     	 Changed; now returns a value, which will cause the process to be
     	 killed if it's an error.

     (*) security_task_alloc(), ->task_alloc_security()

     	 Removed in favour of security_prepare_creds().

     (*) security_cred_free(), ->cred_free()

     	 New.  Free security data attached to cred->security.

     (*) security_prepare_creds(), ->cred_prepare()

     	 New. Duplicate any security data attached to cred->security.

     (*) security_commit_creds(), ->cred_commit()

     	 New. Apply any security effects for the upcoming installation of new
     	 security by commit_creds().

     (*) security_task_post_setuid(), ->task_post_setuid()

     	 Removed in favour of security_task_fix_setuid().

     (*) security_task_fix_setuid(), ->task_fix_setuid()

     	 Fix up the proposed new credentials for setuid().  This is used by
     	 cap_set_fix_setuid() to implicitly adjust capabilities in line with
     	 setuid() changes.  Changes are made to the new credentials, rather
     	 than the task itself as in security_task_post_setuid().

     (*) security_task_reparent_to_init(), ->task_reparent_to_init()

     	 Removed.  Instead the task being reparented to init is referred
     	 directly to init's credentials.

	 NOTE!  This results in the loss of some state: SELinux's osid no
	 longer records the sid of the thread that forked it.

     (*) security_key_alloc(), ->key_alloc()
     (*) security_key_permission(), ->key_permission()

     	 Changed.  These now take cred pointers rather than task pointers to
     	 refer to the security context.

 (4) sys_capset().

     This has been simplified and uses less locking.  The LSM functions it
     calls have been merged.

 (5) reparent_to_kthreadd().

     This gives the current thread the same credentials as init by simply using
     commit_thread() to point that way.

 (6) __sigqueue_alloc() and switch_uid()

     __sigqueue_alloc() can't stop the target task from changing its creds
     beneath it, so this function gets a reference to the currently applicable
     user_struct which it then passes into the sigqueue struct it returns if
     successful.

     switch_uid() is now called from commit_creds(), and possibly should be
     folded into that.  commit_creds() should take care of protecting
     __sigqueue_alloc().

 (7) [sg]et[ug]id() and co and [sg]et_current_groups.

     The set functions now all use prepare_creds(), commit_creds() and
     abort_creds() to build and check a new set of credentials before applying
     it.

     security_task_set[ug]id() is called inside the prepared section.  This
     guarantees that nothing else will affect the creds until we've finished.

     The calling of set_dumpable() has been moved into commit_creds().

     Much of the functionality of set_user() has been moved into
     commit_creds().

     The get functions all simply access the data directly.

 (8) security_task_prctl() and cap_task_prctl().

     security_task_prctl() has been modified to return -ENOSYS if it doesn't
     want to handle a function, or otherwise return the return value directly
     rather than through an argument.

     Additionally, cap_task_prctl() now prepares a new set of credentials, even
     if it doesn't end up using it.

 (9) Keyrings.

     A number of changes have been made to the keyrings code:

     (a) switch_uid_keyring(), copy_keys(), exit_keys() and suid_keys() have
     	 all been dropped and built in to the credentials functions directly.
     	 They may want separating out again later.

     (b) key_alloc() and search_process_keyrings() now take a cred pointer
     	 rather than a task pointer to specify the security context.

     (c) copy_creds() gives a new thread within the same thread group a new
     	 thread keyring if its parent had one, otherwise it discards the thread
     	 keyring.

     (d) The authorisation key now points directly to the credentials to extend
     	 the search into rather pointing to the task that carries them.

     (e) Installing thread, process or session keyrings causes a new set of
     	 credentials to be created, even though it's not strictly necessary for
     	 process or session keyrings (they're shared).

(10) Usermode helper.

     The usermode helper code now carries a cred struct pointer in its
     subprocess_info struct instead of a new session keyring pointer.  This set
     of credentials is derived from init_cred and installed on the new process
     after it has been cloned.

     call_usermodehelper_setup() allocates the new credentials and
     call_usermodehelper_freeinfo() discards them if they haven't been used.  A
     special cred function (prepare_usermodeinfo_creds()) is provided
     specifically for call_usermodehelper_setup() to call.

     call_usermodehelper_setkeys() adjusts the credentials to sport the
     supplied keyring as the new session keyring.

(11) SELinux.

     SELinux has a number of changes, in addition to those to support the LSM
     interface changes mentioned above:

     (a) selinux_setprocattr() no longer does its check for whether the
     	 current ptracer can access processes with the new SID inside the lock
     	 that covers getting the ptracer's SID.  Whilst this lock ensures that
     	 the check is done with the ptracer pinned, the result is only valid
     	 until the lock is released, so there's no point doing it inside the
     	 lock.

(12) is_single_threaded().

     This function has been extracted from selinux_setprocattr() and put into
     a file of its own in the lib/ directory as join_session_keyring() now
     wants to use it too.

     The code in SELinux just checked to see whether a task shared mm_structs
     with other tasks (CLONE_VM), but that isn't good enough.  We really want
     to know if they're part of the same thread group (CLONE_THREAD).

(13) nfsd.

     The NFS server daemon now has to use the COW credentials to set the
     credentials it is going to use.  It really needs to pass the credentials
     down to the functions it calls, but it can't do that until other patches
     in this series have been applied.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 10:39:23 +11:00

1008 lines
24 KiB
C
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/* Basic authentication token and access key management
*
* Copyright (C) 2004-2008 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/poison.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/workqueue.h>
#include <linux/random.h>
#include <linux/err.h>
#include "internal.h"
static struct kmem_cache *key_jar;
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);
unsigned int key_quota_root_maxkeys = 200; /* root's key count quota */
unsigned int key_quota_root_maxbytes = 20000; /* root's key space quota */
unsigned int key_quota_maxkeys = 200; /* general key count quota */
unsigned int key_quota_maxbytes = 20000; /* general key space quota */
static LIST_HEAD(key_types_list);
static DECLARE_RWSEM(key_types_sem);
static void key_cleanup(struct work_struct *work);
static DECLARE_WORK(key_cleanup_task, key_cleanup);
/* we serialise key instantiation and link */
DEFINE_MUTEX(key_construction_mutex);
/* any key who's type gets unegistered will be re-typed to this */
static 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);
mutex_init(&candidate->cons_lock);
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);
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() */
/*****************************************************************************/
/*
* assign a key the next unique serial number
* - these are assigned randomly to avoid security issues through covert
* channel problems
*/
static inline void key_alloc_serial(struct key *key)
{
struct rb_node *parent, **p;
struct key *xkey;
/* propose a random serial number and look for a hole for it in the
* serial number tree */
do {
get_random_bytes(&key->serial, sizeof(key->serial));
key->serial >>= 1; /* negative numbers are not permitted */
} while (key->serial < 3);
spin_lock(&key_serial_lock);
attempt_insertion:
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;
}
/* 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);
spin_unlock(&key_serial_lock);
return;
/* 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++;
if (key->serial < 3) {
key->serial = 3;
goto attempt_insertion;
}
parent = rb_next(parent);
if (!parent)
goto attempt_insertion;
xkey = rb_entry(parent, struct key, serial_node);
if (key->serial < xkey->serial)
goto attempt_insertion;
}
} /* 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
* key_create_or_update()
* - 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, const struct cred *cred,
key_perm_t perm, unsigned long flags)
{
struct key_user *user = NULL;
struct key *key;
size_t desclen, quotalen;
int ret;
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 (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
unsigned maxkeys = (uid == 0) ?
key_quota_root_maxkeys : key_quota_maxkeys;
unsigned maxbytes = (uid == 0) ?
key_quota_root_maxbytes : key_quota_maxbytes;
spin_lock(&user->lock);
if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
if (user->qnkeys + 1 >= maxkeys ||
user->qnbytes + quotalen >= maxbytes ||
user->qnbytes + quotalen < user->qnbytes)
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, GFP_KERNEL);
if (!key)
goto no_memory_2;
if (desc) {
key->description = kmemdup(desc, desclen, GFP_KERNEL);
if (!key->description)
goto no_memory_3;
}
atomic_set(&key->usage, 1);
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;
key->security = NULL;
if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
key->flags |= 1 << KEY_FLAG_IN_QUOTA;
memset(&key->type_data, 0, sizeof(key->type_data));
#ifdef KEY_DEBUGGING
key->magic = KEY_DEBUG_MAGIC;
#endif
/* let the security module know about the key */
ret = security_key_alloc(key, cred, flags);
if (ret < 0)
goto security_error;
/* publish the key by giving it a serial number */
atomic_inc(&user->nkeys);
key_alloc_serial(key);
error:
return key;
security_error:
kfree(key->description);
kmem_cache_free(key_jar, key);
if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
spin_lock(&user->lock);
user->qnkeys--;
user->qnbytes -= quotalen;
spin_unlock(&user->lock);
}
key_user_put(user);
key = ERR_PTR(ret);
goto error;
no_memory_3:
kmem_cache_free(key_jar, key);
no_memory_2:
if (!(flags & KEY_ALLOC_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 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
unsigned maxbytes = (key->user->uid == 0) ?
key_quota_root_maxbytes : key_quota_maxbytes;
spin_lock(&key->user->lock);
if (delta > 0 &&
(key->user->qnbytes + delta >= maxbytes ||
key->user->qnbytes + delta < key->user->qnbytes)) {
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,
struct key *authkey)
{
int ret, awaken;
key_check(key);
key_check(keyring);
awaken = 0;
ret = -EBUSY;
mutex_lock(&key_construction_mutex);
/* can't instantiate twice */
if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
/* instantiate the key */
ret = key->type->instantiate(key, data, datalen);
if (ret == 0) {
/* mark the key as being instantiated */
atomic_inc(&key->user->nikeys);
set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
awaken = 1;
/* and link it into the destination keyring */
if (keyring)
ret = __key_link(keyring, key);
/* disable the authorisation key */
if (authkey)
key_revoke(authkey);
}
}
mutex_unlock(&key_construction_mutex);
/* wake up anyone waiting for a key to be constructed */
if (awaken)
wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
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,
struct key *authkey)
{
int ret;
if (keyring)
down_write(&keyring->sem);
ret = __key_instantiate_and_link(key, data, datalen, keyring, authkey);
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 key *authkey)
{
struct timespec now;
int ret, awaken;
key_check(key);
key_check(keyring);
awaken = 0;
ret = -EBUSY;
if (keyring)
down_write(&keyring->sem);
mutex_lock(&key_construction_mutex);
/* can't instantiate twice */
if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
/* mark the key as being negatively instantiated */
atomic_inc(&key->user->nikeys);
set_bit(KEY_FLAG_NEGATIVE, &key->flags);
set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
now = current_kernel_time();
key->expiry = now.tv_sec + timeout;
if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
awaken = 1;
ret = 0;
/* and link it into the destination keyring */
if (keyring)
ret = __key_link(keyring, key);
/* disable the authorisation key */
if (authkey)
key_revoke(authkey);
}
mutex_unlock(&key_construction_mutex);
if (keyring)
up_write(&keyring->sem);
/* wake up anyone waiting for a key to be constructed */
if (awaken)
wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
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(struct work_struct *work)
{
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);
key_check(key);
security_key_free(key);
/* deal with the user's key tracking and quota */
if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
spin_lock(&key->user->lock);
key->user->qnkeys--;
key->user->qnbytes -= key->quotalen;
spin_unlock(&key->user->lock);
}
atomic_dec(&key->user->nkeys);
if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
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:
/* pretend it doesn't exist if it's dead */
if (atomic_read(&key->usage) == 0 ||
test_bit(KEY_FLAG_DEAD, &key->flags) ||
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 key_ref_t __key_update(key_ref_t key_ref,
const void *payload, size_t plen)
{
struct key *key = key_ref_to_ptr(key_ref);
int ret;
/* need write permission on the key to update it */
ret = key_permission(key_ref, KEY_WRITE);
if (ret < 0)
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 */
clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
up_write(&key->sem);
if (ret < 0)
goto error;
out:
return key_ref;
error:
key_put(key);
key_ref = 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
*/
key_ref_t key_create_or_update(key_ref_t keyring_ref,
const char *type,
const char *description,
const void *payload,
size_t plen,
key_perm_t perm,
unsigned long flags)
{
const struct cred *cred = current_cred();
struct key_type *ktype;
struct key *keyring, *key = NULL;
key_ref_t key_ref;
int ret;
/* 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_ref = ERR_PTR(-ENODEV);
goto error;
}
key_ref = ERR_PTR(-EINVAL);
if (!ktype->match || !ktype->instantiate)
goto error_2;
keyring = key_ref_to_ptr(keyring_ref);
key_check(keyring);
key_ref = ERR_PTR(-ENOTDIR);
if (keyring->type != &key_type_keyring)
goto error_2;
down_write(&keyring->sem);
/* if we're going to allocate a new key, we're going to have
* to modify the keyring */
ret = key_permission(keyring_ref, KEY_WRITE);
if (ret < 0) {
key_ref = ERR_PTR(ret);
goto error_3;
}
/* if it's possible to update this type of key, search for an existing
* key of the same type and description in the destination keyring and
* update that instead if possible
*/
if (ktype->update) {
key_ref = __keyring_search_one(keyring_ref, ktype, description,
0);
if (!IS_ERR(key_ref))
goto found_matching_key;
}
/* if the client doesn't provide, decide on the permissions we want */
if (perm == KEY_PERM_UNDEF) {
perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
if (ktype->read)
perm |= KEY_POS_READ | KEY_USR_READ;
if (ktype == &key_type_keyring || ktype->update)
perm |= KEY_USR_WRITE;
}
/* allocate a new key */
key = key_alloc(ktype, description, cred->fsuid, cred->fsgid, cred,
perm, flags);
if (IS_ERR(key)) {
key_ref = ERR_CAST(key);
goto error_3;
}
/* instantiate it and link it into the target keyring */
ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
if (ret < 0) {
key_put(key);
key_ref = ERR_PTR(ret);
goto error_3;
}
key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
error_3:
up_write(&keyring->sem);
error_2:
key_type_put(ktype);
error:
return key_ref;
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_ref = __key_update(key_ref, payload, plen);
goto error;
} /* end key_create_or_update() */
EXPORT_SYMBOL(key_create_or_update);
/*****************************************************************************/
/*
* update a key
*/
int key_update(key_ref_t key_ref, const void *payload, size_t plen)
{
struct key *key = key_ref_to_ptr(key_ref);
int ret;
key_check(key);
/* the key must be writable */
ret = key_permission(key_ref, KEY_WRITE);
if (ret < 0)
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 */
clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
up_write(&key->sem);
}
error:
return ret;
} /* end key_update() */
EXPORT_SYMBOL(key_update);
/*****************************************************************************/
/*
* 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
* - we tell lockdep that we might nest because we might be revoking an
* authorisation key whilst holding the sem on a key we've just
* instantiated
*/
down_write_nested(&key->sem, 1);
if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
key->type->revoke)
key->type->revoke(key);
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);
/* mark all the keys of this type dead */
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)
key->type = &key_type_dead;
}
spin_unlock(&key_serial_lock);
/* make sure everyone revalidates their keys */
synchronize_rcu();
/* we should now be able to destroy the payloads of all the keys of
* this type with impunity */
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) {
if (ktype->destroy)
ktype->destroy(key);
memset(&key->payload, KEY_DESTROY, 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);
/* 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);
} /* end key_init() */
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