- 根目录:
- security
- keys
- keyring.c
/* Keyring handling
*
* Copyright (C) 2004-2005, 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/sched.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/seq_file.h>
#include <linux/err.h>
#include <keys/keyring-type.h>
#include <linux/uaccess.h>
#include "internal.h"
#define rcu_dereference_locked_keyring(keyring) \
(rcu_dereference_protected( \
(keyring)->payload.subscriptions, \
rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
#define KEY_LINK_FIXQUOTA 1UL
/*
* When plumbing the depths of the key tree, this sets a hard limit
* set on how deep we're willing to go.
*/
#define KEYRING_SEARCH_MAX_DEPTH 6
/*
* We keep all named keyrings in a hash to speed looking them up.
*/
#define KEYRING_NAME_HASH_SIZE (1 << 5)
static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
static DEFINE_RWLOCK(keyring_name_lock);
static inline unsigned keyring_hash(const char *desc)
{
unsigned bucket = 0;
for (; *desc; desc++)
bucket += (unsigned char)*desc;
return bucket & (KEYRING_NAME_HASH_SIZE - 1);
}
/*
* The keyring key type definition. Keyrings are simply keys of this type and
* can be treated as ordinary keys in addition to having their own special
* operations.
*/
static int keyring_instantiate(struct key *keyring,
const void *data, size_t datalen);
static int keyring_match(const struct key *keyring, const void *criterion);
static void keyring_revoke(struct key *keyring);
static void keyring_destroy(struct key *keyring);
static void keyring_describe(const struct key *keyring, struct seq_file *m);
static long keyring_read(const struct key *keyring,
char __user *buffer, size_t buflen);
struct key_type key_type_keyring = {
.name = "keyring",
.def_datalen = sizeof(struct keyring_list),
.instantiate = keyring_instantiate,
.match = keyring_match,
.revoke = keyring_revoke,
.destroy = keyring_destroy,
.describe = keyring_describe,
.read = keyring_read,
};
EXPORT_SYMBOL(key_type_keyring);
/*
* Semaphore to serialise link/link calls to prevent two link calls in parallel
* introducing a cycle.
*/
static DECLARE_RWSEM(keyring_serialise_link_sem);
/*
* Publish the name of a keyring so that it can be found by name (if it has
* one).
*/
static void keyring_publish_name(struct key *keyring)
{
int bucket;
if (keyring->description) {
bucket = keyring_hash(keyring->description);
write_lock(&keyring_name_lock);
if (!keyring_name_hash[bucket].next)
INIT_LIST_HEAD(&keyring_name_hash[bucket]);
list_add_tail(&keyring->type_data.link,
&keyring_name_hash[bucket]);
write_unlock(&keyring_name_lock);
}
}
/*
* Initialise a keyring.
*
* Returns 0 on success, -EINVAL if given any data.
*/
static int keyring_instantiate(struct key *keyring,
const void *data, size_t datalen)
{
int ret;
ret = -EINVAL;
if (datalen == 0) {
/* make the keyring available by name if it has one */
keyring_publish_name(keyring);
ret = 0;
}
return ret;
}
/*
* Match keyrings on their name
*/
static int keyring_match(const struct key *keyring, const void *description)
{
return keyring->description &&
strcmp(keyring->description, description) == 0;
}
/*
* Clean up a keyring when it is destroyed. Unpublish its name if it had one
* and dispose of its data.
*/
static void keyring_destroy(struct key *keyring)
{
struct keyring_list *klist;
int loop;
if (keyring->description) {
write_lock(&keyring_name_lock);
if (keyring->type_data.link.next != NULL &&
!list_empty(&keyring->type_data.link))
list_del(&keyring->type_data.link);
write_unlock(&keyring_name_lock);
}
klist = rcu_dereference_check(keyring->payload.subscriptions,
atomic_read(&keyring->usage) == 0);
if (klist) {
for (loop = klist->nkeys - 1; loop >= 0; loop--)
key_put(klist->keys[loop]);
kfree(klist);
}
}
/*
* Describe a keyring for /proc.
*/
static void keyring_describe(const struct key *keyring, struct seq_file *m)
{
struct keyring_list *klist;
if (keyring->description)
seq_puts(m, keyring->description);
else
seq_puts(m, "[anon]");
if (key_is_instantiated(keyring)) {
rcu_read_lock();
klist = rcu_dereference(keyring->payload.subscriptions);
if (klist)
seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
else
seq_puts(m, ": empty");
rcu_read_unlock();
}
}
/*
* Read a list of key IDs from the keyring's contents in binary form
*
* The keyring's semaphore is read-locked by the caller.
*/
static long keyring_read(const struct key *keyring,
char __user *buffer, size_t buflen)
{
struct keyring_list *klist;
struct key *key;
size_t qty, tmp;
int loop, ret;
ret = 0;
klist = rcu_dereference_locked_keyring(keyring);
if (klist) {
/* calculate how much data we could return */
qty = klist->nkeys * sizeof(key_serial_t);
if (buffer && buflen > 0) {
if (buflen > qty)
buflen = qty;
/* copy the IDs of the subscribed keys into the
* buffer */
ret = -EFAULT;
for (loop = 0; loop < klist->nkeys; loop++) {
key = klist->keys[loop];
tmp = sizeof(key_serial_t);
if (tmp > buflen)
tmp = buflen;
if (copy_to_user(buffer,
&key->serial,
tmp) != 0)
goto error;
buflen -= tmp;
if (buflen == 0)
break;
buffer += tmp;
}
}
ret = qty;
}
error:
return ret;
}
/*
* Allocate a keyring and link into the destination keyring.
*/
struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
const struct cred *cred, unsigned long flags,
struct key *dest)
{
struct key *keyring;
int ret;
keyring = key_alloc(&key_type_keyring, description,
uid, gid, cred,
(KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
flags);
if (!IS_ERR(keyring)) {
ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
if (ret < 0) {
key_put(keyring);
keyring = ERR_PTR(ret);
}
}
return keyring;
}
/**
* keyring_search_aux - Search a keyring tree for a key matching some criteria
* @keyring_ref: A pointer to the keyring with possession indicator.
* @cred: The credentials to use for permissions checks.
* @type: The type of key to search for.
* @description: Parameter for @match.
* @match: Function to rule on whether or not a key is the one required.
* @no_state_check: Don't check if a matching key is bad
*
* Search the supplied keyring tree for a key that matches the criteria given.
* The root keyring and any linked keyrings must grant Search permission to the
* caller to be searchable and keys can only be found if they too grant Search
* to the caller. The possession flag on the root keyring pointer controls use
* of the possessor bits in permissions checking of the entire tree. In
* addition, the LSM gets to forbid keyring searches and key matches.
*
* The search is performed as a breadth-then-depth search up to the prescribed
* limit (KEYRING_SEARCH_MAX_DEPTH).
*
* Keys are matched to the type provided and are then filtered by the match
* function, which is given the description to use in any way it sees fit. The
* match function may use any attributes of a key that it wishes to to
* determine the match. Normally the match function from the key type would be
* used.
*
* RCU is used to prevent the keyring key lists from disappearing without the
* need to take lots of locks.
*
* Returns a pointer to the found key and increments the key usage count if
* successful; -EAGAIN if no matching keys were found, or if expired or revoked
* keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
* specified keyring wasn't a keyring.
*
* In the case of a successful return, the possession attribute from
* @keyring_ref is propagated to the returned key reference.
*/
key_ref_t keyring_search_aux(key_ref_t keyring_ref,
const struct cred *cred,
struct key_type *type,
const void *description,
key_match_func_t match,
bool no_state_check)
{
struct {
struct keyring_list *keylist;
int kix;
} stack[KEYRING_SEARCH_MAX_DEPTH];
struct keyring_list *keylist;
struct timespec now;
unsigned long possessed, kflags;
struct key *keyring, *key;
key_ref_t key_ref;
long err;
int sp, nkeys, kix;
keyring = key_ref_to_ptr(keyring_ref);
possessed = is_key_possessed(keyring_ref);
key_check(keyring);
/* top keyring must have search permission to begin the search */
err = key_task_permission(keyring_ref, cred, KEY_SEARCH);
if (err < 0) {
key_ref = ERR_PTR(err);
goto error;
}
key_ref = ERR_PTR(-ENOTDIR);
if (keyring->type != &key_type_keyring)
goto error;
rcu_read_lock();
now = current_kernel_time();
err = -EAGAIN;
sp = 0;
/* firstly we should check to see if this top-level keyring is what we
* are looking for */
key_ref = ERR_PTR(-EAGAIN);
kflags = keyring->flags;
if (keyring->type == type && match(keyring, description)) {
key = keyring;
if (no_state_check)
goto found;
/* check it isn't negative and hasn't expired or been
* revoked */
if (kflags & (1 << KEY_FLAG_REVOKED))
goto error_2;
if (key->expiry && now.tv_sec >= key->expiry)
goto error_2;
key_ref = ERR_PTR(key->type_data.reject_error);
if (kflags & (1 << KEY_FLAG_NEGATIVE))
goto error_2;
goto found;
}
/* otherwise, the top keyring must not be revoked, expired, or
* negatively instantiated if we are to search it */
key_ref = ERR_PTR(-EAGAIN);
if (kflags & ((1 << KEY_FLAG_REVOKED) | (1 << KEY_FLAG_NEGATIVE)) ||
(keyring->expiry && now.tv_sec >= keyring->expiry))
goto error_2;
/* start processing a new keyring */
descend:
if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
goto not_this_keyring;
keylist = rcu_dereference(keyring->payload.subscriptions);
if (!keylist)
goto not_this_keyring;
/* iterate through the keys in this keyring first */
nkeys = keylist->nkeys;
smp_rmb();
for (kix = 0; kix < nkeys; kix++) {
key = keylist->keys[kix];
kflags = key->flags;
/* ignore keys not of this type */
if (key->type != type)
continue;
/* skip revoked keys and expired keys */
if (!no_state_check) {
if (kflags & (1 << KEY_FLAG_REVOKED))
continue;
if (key->expiry && now.tv_sec >= key->expiry)
continue;
}
/* keys that don't match */
if (!match(key, description))
continue;
/* key must have search permissions */
if (key_task_permission(make_key_ref(key, possessed),
cred, KEY_SEARCH) < 0)
continue;
if (no_state_check)
goto found;
/* we set a different error code if we pass a negative key */
if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
err = key->type_data.reject_error;
continue;
}
goto found;
}
/* search through the keyrings nested in this one */
kix = 0;
ascend:
nkeys = keylist->nkeys;
smp_rmb();
for (; kix < nkeys; kix++) {
key = keylist->keys[kix];
if (key->type != &key_type_keyring)
continue;
/* recursively search nested keyrings
* - only search keyrings for which we have search permission
*/
if (sp >= KEYRING_SEARCH_MAX_DEPTH)
continue;
if (key_task_permission(make_key_ref(key, possessed),
cred, KEY_SEARCH) < 0)
continue;
/* stack the current position */
stack[sp].keylist = keylist;
stack[sp].kix = kix;
sp++;
/* begin again with the new keyring */
keyring = key;
goto descend;
}
/* the keyring we're looking at was disqualified or didn't contain a
* matching key */
not_this_keyring:
if (sp > 0) {
/* resume the processing of a keyring higher up in the tree */
sp--;
keylist = stack[sp].keylist;
kix = stack[sp].kix + 1;
goto ascend;
}
key_ref = ERR_PTR(err);
goto error_2;
/* we found a viable match */
found:
atomic_inc(&key->usage);
key_check(key);
key_ref = make_key_ref(key, possessed);
error_2:
rcu_read_unlock();
error:
return key_ref;
}
/**
* keyring_search - Search the supplied keyring tree for a matching key
* @keyring: The root of the keyring tree to be searched.
* @type: The type of keyring we want to find.
* @description: The name of the keyring we want to find.
*
* As keyring_search_aux() above, but using the current task's credentials and
* type's default matching function.
*/
key_ref_t keyring_search(key_ref_t keyring,
struct key_type *type,
const char *description)
{
if (!type->match)
return ERR_PTR(-ENOKEY);
return keyring_search_aux(keyring, current->cred,
type, description, type->match, false);
}
EXPORT_SYMBOL(keyring_search);
/*
* Search the given keyring only (no recursion).
*
* The caller must guarantee that the keyring is a keyring and that the
* permission is granted to search the keyring as no check is made here.
*
* RCU is used to make it unnecessary to lock the keyring key list here.
*
* Returns a pointer to the found key with usage count incremented if
* successful and returns -ENOKEY if not found. Revoked keys and keys not
* providing the requested permission are skipped over.
*
* If successful, the possession indicator is propagated from the keyring ref
* to the returned key reference.
*/
key_ref_t __keyring_search_one(key_ref_t keyring_ref,
const struct key_type *ktype,
const char *description,
key_perm_t perm)
{
struct keyring_list *klist;
unsigned long possessed;
struct key *keyring, *key;
int nkeys, loop;
keyring = key_ref_to_ptr(keyring_ref);
possessed = is_key_possessed(keyring_ref);
rcu_read_lock();
klist = rcu_dereference(keyring->payload.subscriptions);
if (klist) {
nkeys = klist->nkeys;
smp_rmb();
for (loop = 0; loop < nkeys ; loop++) {
key = klist->keys[loop];
if (key->type == ktype &&
(!key->type->match ||
key->type->match(key, description)) &&
key_permission(make_key_ref(key, possessed),
perm) == 0 &&
!test_bit(KEY_FLAG_REVOKED, &key->flags)
)
goto found;
}
}
rcu_read_unlock();
return ERR_PTR(-ENOKEY);
found:
atomic_inc(&key->usage);
rcu_read_unlock();
return make_key_ref(key, possessed);
}
/*
* Find a keyring with the specified name.
*
* All named keyrings in the current user namespace are searched, provided they
* grant Search permission directly to the caller (unless this check is
* skipped). Keyrings whose usage points have reached zero or who have been
* revoked are skipped.
*
* Returns a pointer to the keyring with the keyring's refcount having being
* incremented on success. -ENOKEY is returned if a key could not be found.
*/
struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
{
struct key *keyring;
int bucket;
if (!name)
return ERR_PTR(-EINVAL);
bucket = keyring_hash(name);
read_lock(&keyring_name_lock);
if (keyring_name_hash[bucket].next) {
/* search this hash bucket for a keyring with a matching name
* that's readable and that hasn't been revoked */
list_for_each_entry(keyring,
&keyring_name_hash[bucket],
type_data.link
) {
if (keyring->user->user_ns != current_user_ns())
continue;
if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
continue;
if (strcmp(keyring->description, name) != 0)
continue;
if (!skip_perm_check &&
key_permission(make_key_ref(keyring, 0),
KEY_SEARCH) < 0)
continue;
/* we've got a match but we might end up racing with
* key_cleanup() if the keyring is currently 'dead'
* (ie. it has a zero usage count) */
if (!atomic_inc_not_zero(&keyring->usage))
continue;
goto out;
}
}
keyring = ERR_PTR(-ENOKEY);
out:
read_unlock(&keyring_name_lock);
return keyring;
}
/*
* See if a cycle will will be created by inserting acyclic tree B in acyclic
* tree A at the topmost level (ie: as a direct child of A).
*
* Since we are adding B to A at the top level, checking for cycles should just
* be a matter of seeing if node A is somewhere in tree B.
*/
static int keyring_detect_cycle(struct key *A, struct key *B)
{
struct {
struct keyring_list *keylist;
int kix;
} stack[KEYRING_SEARCH_MAX_DEPTH];
struct keyring_list *keylist;
struct key *subtree, *key;
int sp, nkeys, kix, ret;
rcu_read_lock();
ret = -EDEADLK;
if (A == B)
goto cycle_detected;
subtree = B;
sp = 0;
/* start processing a new keyring */
descend:
if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
goto not_this_keyring;
keylist = rcu_dereference(subtree->payload.subscriptions);
if (!keylist)
goto not_this_keyring;
kix = 0;
ascend:
/* iterate through the remaining keys in this keyring */
nkeys = keylist->nkeys;
smp_rmb();
for (; kix < nkeys; kix++) {
key = keylist->keys[kix];
if (key == A)
goto cycle_detected;
/* recursively check nested keyrings */
if (key->type == &key_type_keyring) {
if (sp >= KEYRING_SEARCH_MAX_DEPTH)
goto too_deep;
/* stack the current position */
stack[sp].keylist = keylist;
stack[sp].kix = kix;
sp++;
/* begin again with the new keyring */
subtree = key;
goto descend;
}
}
/* the keyring we're looking at was disqualified or didn't contain a
* matching key */
not_this_keyring:
if (sp > 0) {
/* resume the checking of a keyring higher up in the tree */
sp--;
keylist = stack[sp].keylist;
kix = stack[sp].kix + 1;
goto ascend;
}
ret = 0; /* no cycles detected */
error:
rcu_read_unlock();
return ret;
too_deep:
ret = -ELOOP;
goto error;
cycle_detected:
ret = -EDEADLK;
goto error;
}
/*
* Dispose of a keyring list after the RCU grace period, freeing the unlinked
* key
*/
static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
{
struct keyring_list *klist =
container_of(rcu, struct keyring_list, rcu);
if (klist->delkey != USHRT_MAX)
key_put(klist->keys[klist->delkey]);
kfree(klist);
}
/*
* Preallocate memory so that a key can be linked into to a keyring.
*/
int __key_link_begin(struct key *keyring, const struct key_type *type,
const char *description, unsigned long *_prealloc)
__acquires(&keyring->sem)
{
struct keyring_list *klist, *nklist;
unsigned long prealloc;
unsigned max;
size_t size;
int loop, ret;
kenter("%d,%s,%s,", key_serial(keyring), type->name, description);
if (keyring->type != &key_type_keyring)
return -ENOTDIR;
down_write(&keyring->sem);
ret = -EKEYREVOKED;
if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
goto error_krsem;
/* serialise link/link calls to prevent parallel calls causing a cycle
* when linking two keyring in opposite orders */
if (type == &key_type_keyring)
down_write(&keyring_serialise_link_sem);
klist = rcu_dereference_locked_keyring(keyring);
/* see if there's a matching key we can displace */
if (klist && klist->nkeys > 0) {
for (loop = klist->nkeys - 1; loop >= 0; loop--) {
if (klist->keys[loop]->type == type &&
strcmp(klist->keys[loop]->description,
description) == 0
) {
/* found a match - we'll replace this one with
* the new key */
size = sizeof(struct key *) * klist->maxkeys;
size += sizeof(*klist);
BUG_ON(size > PAGE_SIZE);
ret = -ENOMEM;
nklist = kmemdup(klist, size, GFP_KERNEL);
if (!nklist)
goto error_sem;
/* note replacement slot */
klist->delkey = nklist->delkey = loop;
prealloc = (unsigned long)nklist;
goto done;
}
}
}
/* check that we aren't going to overrun the user's quota */
ret = key_payload_reserve(keyring,
keyring->datalen + KEYQUOTA_LINK_BYTES);
if (ret < 0)
goto error_sem;
if (klist && klist->nkeys < klist->maxkeys) {
/* there's sufficient slack space to append directly */
nklist = NULL;
prealloc = KEY_LINK_FIXQUOTA;
} else {
/* grow the key list */
max = 4;
if (klist)
max += klist->maxkeys;
ret = -ENFILE;
if (max > USHRT_MAX - 1)
goto error_quota;
size = sizeof(*klist) + sizeof(struct key *) * max;
if (size > PAGE_SIZE)
goto error_quota;
ret = -ENOMEM;
nklist = kmalloc(size, GFP_KERNEL);
if (!nklist)
goto error_quota;
nklist->maxkeys = max;
if (klist) {
memcpy(nklist->keys, klist->keys,
sizeof(struct key *) * klist->nkeys);
nklist->delkey = klist->nkeys;
nklist->nkeys = klist->nkeys + 1;
klist->delkey = USHRT_MAX;
} else {
nklist->nkeys = 1;
nklist->delkey = 0;
}
/* add the key into the new space */
nklist->keys[nklist->delkey] = NULL;
}
prealloc = (unsigned long)nklist | KEY_LINK_FIXQUOTA;
done:
*_prealloc = prealloc;
kleave(" = 0");
return 0;
error_quota:
/* undo the quota changes */
key_payload_reserve(keyring,
keyring->datalen - KEYQUOTA_LINK_BYTES);
error_sem:
if (type == &key_type_keyring)
up_write(&keyring_serialise_link_sem);
error_krsem:
up_write(&keyring->sem);
kleave(" = %d", ret);
return ret;
}
/*
* Check already instantiated keys aren't going to be a problem.
*
* The caller must have called __key_link_begin(). Don't need to call this for
* keys that were created since __key_link_begin() was called.
*/
int __key_link_check_live_key(struct key *keyring, struct key *key)
{
if (key->type == &key_type_keyring)
/* check that we aren't going to create a cycle by linking one
* keyring to another */
return keyring_detect_cycle(keyring, key);
return 0;
}
/*
* Link a key into to a keyring.
*
* Must be called with __key_link_begin() having being called. Discards any
* already extant link to matching key if there is one, so that each keyring
* holds at most one link to any given key of a particular type+description
* combination.
*/
void __key_link(struct key *keyring, struct key *key,
unsigned long *_prealloc)
{
struct keyring_list *klist, *nklist;
nklist = (struct keyring_list *)(*_prealloc & ~KEY_LINK_FIXQUOTA);
*_prealloc = 0;
kenter("%d,%d,%p", keyring->serial, key->serial, nklist);
klist = rcu_dereference_locked_keyring(keyring);
atomic_inc(&key->usage);
/* there's a matching key we can displace or an empty slot in a newly
* allocated list we can fill */
if (nklist) {
kdebug("replace %hu/%hu/%hu",
nklist->delkey, nklist->nkeys, nklist->maxkeys);
nklist->keys[nklist->delkey] = key;
rcu_assign_pointer(keyring->payload.subscriptions, nklist);
/* dispose of the old keyring list and, if there was one, the
* displaced key */
if (klist) {
kdebug("dispose %hu/%hu/%hu",
klist->delkey, klist->nkeys, klist->maxkeys);
call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
}
} else {
/* there's sufficient slack space to append directly */
klist->keys[klist->nkeys] = key;
smp_wmb();
klist->nkeys++;
}
}
/*
* Finish linking a key into to a keyring.
*
* Must be called with __key_link_begin() having being called.
*/
void __key_link_end(struct key *keyring, struct key_type *type,
unsigned long prealloc)
__releases(&keyring->sem)
{
BUG_ON(type == NULL);
BUG_ON(type->name == NULL);
kenter("%d,%s,%lx", keyring->serial, type->name, prealloc);
if (type == &key_type_keyring)
up_write(&keyring_serialise_link_sem);
if (prealloc) {
if (prealloc & KEY_LINK_FIXQUOTA)
key_payload_reserve(keyring,
keyring->datalen -
KEYQUOTA_LINK_BYTES);
kfree((struct keyring_list *)(prealloc & ~KEY_LINK_FIXQUOTA));
}
up_write(&keyring->sem);
}
/**
* key_link - Link a key to a keyring
* @keyring: The keyring to make the link in.
* @key: The key to link to.
*
* Make a link in a keyring to a key, such that the keyring holds a reference
* on that key and the key can potentially be found by searching that keyring.
*
* This function will write-lock the keyring's semaphore and will consume some
* of the user's key data quota to hold the link.
*
* Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring,
* -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is
* full, -EDQUOT if there is insufficient key data quota remaining to add
* another link or -ENOMEM if there's insufficient memory.
*
* It is assumed that the caller has checked that it is permitted for a link to
* be made (the keyring should have Write permission and the key Link
* permission).
*/
int key_link(struct key *keyring, struct key *key)
{
unsigned long prealloc;
int ret;
key_check(keyring);
key_check(key);
ret = __key_link_begin(keyring, key->type, key->description, &prealloc);
if (ret == 0) {
ret = __key_link_check_live_key(keyring, key);
if (ret == 0)
__key_link(keyring, key, &prealloc);
__key_link_end(keyring, key->type, prealloc);
}
return ret;
}
EXPORT_SYMBOL(key_link);
/**
* key_unlink - Unlink the first link to a key from a keyring.
* @keyring: The keyring to remove the link from.
* @key: The key the link is to.
*
* Remove a link from a keyring to a key.
*
* This function will write-lock the keyring's semaphore.
*
* Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if
* the key isn't linked to by the keyring or -ENOMEM if there's insufficient
* memory.
*
* It is assumed that the caller has checked that it is permitted for a link to
* be removed (the keyring should have Write permission; no permissions are
* required on the key).
*/
int key_unlink(struct key *keyring, struct key *key)
{
struct keyring_list *klist, *nklist;
int loop, ret;
key_check(keyring);
key_check(key);
ret = -ENOTDIR;
if (keyring->type != &key_type_keyring)
goto error;
down_write(&keyring->sem);
klist = rcu_dereference_locked_keyring(keyring);
if (klist) {
/* search the keyring for the key */
for (loop = 0; loop < klist->nkeys; loop++)
if (klist->keys[loop] == key)
goto key_is_present;
}
up_write(&keyring->sem);
ret = -ENOENT;
goto error;
key_is_present:
/* we need to copy the key list for RCU purposes */
nklist = kmalloc(sizeof(*klist) +
sizeof(struct key *) * klist->maxkeys,
GFP_KERNEL);
if (!nklist)
goto nomem;
nklist->maxkeys = klist->maxkeys;
nklist->nkeys = klist->nkeys - 1;
if (loop > 0)
memcpy(&nklist->keys[0],
&klist->keys[0],
loop * sizeof(struct key *));
if (loop < nklist->nkeys)
memcpy(&nklist->keys[loop],
&klist->keys[loop + 1],
(nklist->nkeys - loop) * sizeof(struct key *));
/* adjust the user's quota */
key_payload_reserve(keyring,
keyring->datalen - KEYQUOTA_LINK_BYTES);
rcu_assign_pointer(keyring->payload.subscriptions, nklist);
up_write(&keyring->sem);
/* schedule for later cleanup */
klist->delkey = loop;
call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
ret = 0;
error:
return ret;
nomem:
ret = -ENOMEM;
up_write(&keyring->sem);
goto error;
}
EXPORT_SYMBOL(key_unlink);
/*
* Dispose of a keyring list after the RCU grace period, releasing the keys it
* links to.
*/
static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
{
struct keyring_list *klist;
int loop;
klist = container_of(rcu, struct keyring_list, rcu);
for (loop = klist->nkeys - 1; loop >= 0; loop--)
key_put(klist->keys[loop]);
kfree(klist);
}
/**
* keyring_clear - Clear a keyring
* @keyring: The keyring to clear.
*
* Clear the contents of the specified keyring.
*
* Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring.
*/
int keyring_clear(struct key *keyring)
{
struct keyring_list *klist;
int ret;
ret = -ENOTDIR;
if (keyring->type == &key_type_keyring) {
/* detach the pointer block with the locks held */
down_write(&keyring->sem);
klist = rcu_dereference_locked_keyring(keyring);
if (klist) {
/* adjust the quota */
key_payload_reserve(keyring,
sizeof(struct keyring_list));
rcu_assign_pointer(keyring->payload.subscriptions,
NULL);
}
up_write(&keyring->sem);
/* free the keys after the locks have been dropped */
if (klist)
call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
ret = 0;
}
return ret;
}
EXPORT_SYMBOL(keyring_clear);
/*
* Dispose of the links from a revoked keyring.
*
* This is called with the key sem write-locked.
*/
static void keyring_revoke(struct key *keyring)
{
struct keyring_list *klist;
klist = rcu_dereference_locked_keyring(keyring);
/* adjust the quota */
key_payload_reserve(keyring, 0);
if (klist) {
rcu_assign_pointer(keyring->payload.subscriptions, NULL);
call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
}
}
/*
* Determine whether a key is dead.
*/
static bool key_is_dead(struct key *key, time_t limit)
{
return test_bit(KEY_FLAG_DEAD, &key->flags) ||
(key->expiry > 0 && key->expiry <= limit);
}
/*
* Collect garbage from the contents of a keyring, replacing the old list with
* a new one with the pointers all shuffled down.
*
* Dead keys are classed as oned that are flagged as being dead or are revoked,
* expired or negative keys that were revoked or expired before the specified
* limit.
*/
void keyring_gc(struct key *keyring, time_t limit)
{
struct keyring_list *klist, *new;
struct key *key;
int loop, keep, max;
kenter("{%x,%s}", key_serial(keyring), keyring->description);
down_write(&keyring->sem);
klist = rcu_dereference_locked_keyring(keyring);
if (!klist)
goto no_klist;
/* work out how many subscriptions we're keeping */
keep = 0;
for (loop = klist->nkeys - 1; loop >= 0; loop--)
if (!key_is_dead(klist->keys[loop], limit))
keep++;
if (keep == klist->nkeys)
goto just_return;
/* allocate a new keyring payload */
max = roundup(keep, 4);
new = kmalloc(sizeof(struct keyring_list) + max * sizeof(struct key *),
GFP_KERNEL);
if (!new)
goto nomem;
new->maxkeys = max;
new->nkeys = 0;
new->delkey = 0;
/* install the live keys
* - must take care as expired keys may be updated back to life
*/
keep = 0;
for (loop = klist->nkeys - 1; loop >= 0; loop--) {
key = klist->keys[loop];
if (!key_is_dead(key, limit)) {
if (keep >= max)
goto discard_new;
new->keys[keep++] = key_get(key);
}
}
new->nkeys = keep;
/* adjust the quota */
key_payload_reserve(keyring,
sizeof(struct keyring_list) +
KEYQUOTA_LINK_BYTES * keep);
if (keep == 0) {
rcu_assign_pointer(keyring->payload.subscriptions, NULL);
kfree(new);
} else {
rcu_assign_pointer(keyring->payload.subscriptions, new);
}
up_write(&keyring->sem);
call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
kleave(" [yes]");
return;
discard_new:
new->nkeys = keep;
keyring_clear_rcu_disposal(&new->rcu);
up_write(&keyring->sem);
kleave(" [discard]");
return;
just_return:
up_write(&keyring->sem);
kleave(" [no dead]");
return;
no_klist:
up_write(&keyring->sem);
kleave(" [no_klist]");
return;
nomem:
up_write(&keyring->sem);
kleave(" [oom]");
}