/* keyring.c: keyring handling
*
* 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/seq_file.h>
#include <linux/err.h>
#include <asm/uaccess.h>
#include "internal.h"
/*
* 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 type definition
*/
static int keyring_instantiate(struct key *keyring,
const void *data, size_t datalen);
static int keyring_duplicate(struct key *keyring, const struct key *source);
static int keyring_match(const struct key *keyring, const void *criterion);
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,
.duplicate = keyring_duplicate,
.match = keyring_match,
.destroy = keyring_destroy,
.describe = keyring_describe,
.read = keyring_read,
};
/*
* semaphore to serialise link/link calls to prevent two link calls in parallel
* introducing a cycle
*/
DECLARE_RWSEM(keyring_serialise_link_sem);
/*****************************************************************************/
/*
* publish the name of a keyring so that it can be found by name (if it has
* one)
*/
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);
}
} /* end keyring_publish_name() */
/*****************************************************************************/
/*
* initialise a keyring
* - we object if we were 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;
} /* end keyring_instantiate() */
/*****************************************************************************/
/*
* duplicate the list of subscribed keys from a source keyring into this one
*/
static int keyring_duplicate(struct key *keyring, const struct key *source)
{
struct keyring_list *sklist, *klist;
unsigned max;
size_t size;
int loop, ret;
const unsigned limit =
(PAGE_SIZE - sizeof(*klist)) / sizeof(struct key);
ret = 0;
sklist = source->payload.subscriptions;
if (sklist && sklist->nkeys > 0) {
max = sklist->nkeys;
BUG_ON(max > limit);
max = (max + 3) & ~3;
if (max > limit)
max = limit;
ret = -ENOMEM;
size = sizeof(*klist) + sizeof(struct key) * max;
klist = kmalloc(size, GFP_KERNEL);
if (!klist)
goto error;
klist->maxkeys = max;
klist->nkeys = sklist->nkeys;
memcpy(klist->keys,
sklist->keys,
sklist->nkeys * sizeof(struct key));
for (loop = klist->nkeys - 1; loop >= 0; loop--)
atomic_inc(&klist->keys[loop]->usage);
keyring->payload.subscriptions = klist;
ret = 0;
}
error:
return ret;
} /* end keyring_duplicate() */
/*****************************************************************************/
/*
* match keyrings on their name
*/
static int keyring_match(const struct key *keyring, const void *description)
{
return keyring->description &&
strcmp(keyring->description, description) == 0;
} /* end keyring_match() */
/*****************************************************************************/
/*
* dispose of the data dangling from the corpse of a keyring
*/
static void keyring_destroy(struct key *keyring)
{
struct keyring_list *klist;
int loop;
if (keyring->description) {
write_lock(&keyring_name_lock);
list_del(&keyring->type_data.link);
write_unlock(&keyring_name_lock);
}
klist = keyring->payload.subscriptions;
if (klist) {
for (loop = klist->nkeys - 1; loop >= 0; loop--)
key_put(klist->keys[loop]);
kfree(klist);
}
} /* end keyring_destroy() */
/*****************************************************************************/
/*
* describe the keyring
*/
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]");
}
klist = keyring->payload.subscriptions;
if (klist)
seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
else
seq_puts(m, ": empty");
} /* end keyring_describe() */
/*****************************************************************************/
/*
* read a list of key IDs from the keyring's contents
*/
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 = keyring->payload.subscriptions;
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;
} /* end keyring_read() */
/*****************************************************************************/
/*
* allocate a keyring and link into the destination keyring
*/
struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
int not_in_quota, struct key *dest)
{
struct key *keyring;
int ret;
keyring = key_alloc(&key_type_keyring, description,
uid, gid, KEY_USR_ALL, not_in_quota);
if (!IS_ERR(keyring)) {
ret = key_instantiate_and_link(keyring, NULL, 0, dest);
if (ret < 0) {
key_put(keyring);
keyring = ERR_PTR(ret);
}
}
return keyring;
} /* end keyring_alloc() */
/*****************************************************************************/
/*
* search the supplied keyring tree for a key that matches the criterion
* - perform a breadth-then-depth search up to the prescribed limit
* - we only find keys on which we have search permission
* - we use the supplied match function to see if the description (or other
* feature of interest) matches
* - we readlock the keyrings as we search down the tree
* - we return -EAGAIN if we didn't find any matching key
* - we return -ENOKEY if we only found negative matching keys
*/
struct key *keyring_search_aux(struct key *keyring,
struct key_type *type,
const void *description,
key_match_func_t match)
{
struct {
struct key *keyring;
int kix;
} stack[KEYRING_SEARCH_MAX_DEPTH];
struct keyring_list *keylist;
struct timespec now;
struct key *key;
long err;
int sp, psp, kix;
key_check(keyring);
/* top keyring must have search permission to begin the search */
key = ERR_PTR(-EACCES);
if (!key_permission(keyring, KEY_SEARCH))
goto error;
key = ERR_PTR(-ENOTDIR);
if (keyring->type != &key_type_keyring)
goto error;
now = current_kernel_time();
err = -EAGAIN;
sp = 0;
/* start processing a new keyring */
descend:
read_lock(&keyring->lock);
if (keyring->flags & KEY_FLAG_REVOKED)
goto not_this_keyring;
keylist = keyring->payload.subscriptions;
if (!keylist)
goto not_this_keyring;
/* iterate through the keys in this keyring first */
for (kix = 0; kix < keylist->nkeys; kix++) {
key = keylist->keys[kix];
/* ignore keys not of this type */
if (key->type != type)
continue;
/* skip revoked keys and expired keys */
if (key->flags & 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_permission(key, KEY_SEARCH))
continue;
/* we set a different error code if we find a negative key */
if (key->flags & KEY_FLAG_NEGATIVE) {
err = -ENOKEY;
continue;
}
goto found;
}
/* search through the keyrings nested in this one */
kix = 0;
ascend:
while (kix < keylist->nkeys) {
key = keylist->keys[kix];
if (key->type != &key_type_keyring)
goto next;
/* recursively search nested keyrings
* - only search keyrings for which we have search permission
*/
if (sp >= KEYRING_SEARCH_MAX_DEPTH)
goto next;
if (!key_permission(key, KEY_SEARCH))
goto next;
/* evade loops in the keyring tree */
for (psp = 0; psp < sp; psp++)
if (stack[psp].keyring == keyring)
goto next;
/* stack the current position */
stack[sp].keyring = keyring;
stack[sp].kix = kix;
sp++;
/* begin again with the new keyring */
keyring = key;
goto descend;
next:
kix++;
}
/* the keyring we're looking at was disqualified or didn't contain a
* matching key */
not_this_keyring:
read_unlock(&keyring->lock);
if (sp > 0) {
/* resume the processing of a keyring higher up in the tree */
sp--;
keyring = stack[sp].keyring;
keylist = keyring->payload.subscriptions;
kix = stack[sp].kix + 1;
goto ascend;
}
key = ERR_PTR(err);
goto error;
/* we found a viable match */
found:
atomic_inc(&key->usage);
read_unlock(&keyring->lock);
/* unwind the keyring stack */
while (sp > 0) {
sp--;
read_unlock(&stack[sp].keyring->lock);
}
key_check(key);
error:
return key;
} /* end keyring_search_aux() */
/*****************************************************************************/
/*
* search the supplied keyring tree for a key that matches the criterion
* - perform a breadth-then-depth search up to the prescribed limit
* - we only find keys on which we have search permission
* - we readlock the keyrings as we search down the tree
* - we return -EAGAIN if we didn't find any matching key
* - we return -ENOKEY if we only found negative matching keys
*/
struct key *keyring_search(struct key *keyring,
struct key_type *type,
const char *description)
{
return keyring_search_aux(keyring, type, description, type->match);
} /* end keyring_search() */
EXPORT_SYMBOL(keyring_search);
/*****************************************************************************/
/*
* search the given keyring only (no recursion)
* - keyring must be locked by caller
*/
struct key *__keyring_search_one(struct key *keyring,
const struct key_type *ktype,
const char *description,
key_perm_t perm)
{
struct keyring_list *klist;
struct key *key;
int loop;
klist = keyring->payload.subscriptions;
if (klist) {
for (loop = 0; loop < klist->nkeys; loop++) {
key = klist->keys[loop];
if (key->type == ktype &&
key->type->match(key, description) &&
key_permission(key, perm) &&
!(key->flags & KEY_FLAG_REVOKED)
)
goto found;
}
}
key = ERR_PTR(-ENOKEY);
goto error;
found:
atomic_inc(&key->usage);
error:
return key;
} /* end __keyring_search_one() */
/*****************************************************************************/
/*
* find a keyring with the specified name
* - all named keyrings are searched
* - only find keyrings with search permission for the process
* - only find keyrings with a serial number greater than the one specified
*/
struct key *find_keyring_by_name(const char *name, key_serial_t bound)
{
struct key *keyring;
int bucket;
keyring = ERR_PTR(-EINVAL);
if (!name)
goto error;
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->flags & KEY_FLAG_REVOKED)
continue;
if (strcmp(keyring->description, name) != 0)
continue;
if (!key_permission(keyring, KEY_SEARCH))
continue;
/* found a potential candidate, but we still need to
* check the serial number */
if (keyring->serial <= bound)
continue;
/* we've got a match */
atomic_inc(&keyring->usage);
read_unlock(&keyring_name_lock);
goto error;
}
}
read_unlock(&keyring_name_lock);
keyring = ERR_PTR(-ENOKEY);
error:
return keyring;
} /* end find_keyring_by_name() */
/*****************************************************************************/
/*
* 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 key *subtree;
int kix;
} stack[KEYRING_SEARCH_MAX_DEPTH];
struct keyring_list *keylist;
struct key *subtree, *key;
int sp, kix, ret;
ret = -EDEADLK;
if (A == B)
goto error;
subtree = B;
sp = 0;
/* start processing a new keyring */
descend:
read_lock(&subtree->lock);
if (subtree->flags & KEY_FLAG_REVOKED)
goto not_this_keyring;
keylist = subtree->payload.subscriptions;
if (!keylist)
goto not_this_keyring;
kix = 0;
ascend:
/* iterate through the remaining keys in this keyring */
for (; kix < keylist->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].subtree = subtree;
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:
read_unlock(&subtree->lock);
if (sp > 0) {
/* resume the checking of a keyring higher up in the tree */
sp--;
subtree = stack[sp].subtree;
keylist = subtree->payload.subscriptions;
kix = stack[sp].kix + 1;
goto ascend;
}
ret = 0; /* no cycles detected */
error:
return ret;
too_deep:
ret = -ELOOP;
goto error_unwind;
cycle_detected:
ret = -EDEADLK;
error_unwind:
read_unlock(&subtree->lock);
/* unwind the keyring stack */
while (sp > 0) {
sp--;
read_unlock(&stack[sp].subtree->lock);
}
goto error;
} /* end keyring_detect_cycle() */
/*****************************************************************************/
/*
* link a key into to a keyring
* - must be called with the keyring's semaphore held
*/
int __key_link(struct key *keyring, struct key *key)
{
struct keyring_list *klist, *nklist;
unsigned max;
size_t size;
int ret;
ret = -EKEYREVOKED;
if (keyring->flags & KEY_FLAG_REVOKED)
goto error;
ret = -ENOTDIR;
if (keyring->type != &key_type_keyring)
goto error;
/* serialise link/link calls to prevent parallel calls causing a
* cycle when applied to two keyring in opposite orders */
down_write(&keyring_serialise_link_sem);
/* check that we aren't going to create a cycle adding one keyring to
* another */
if (key->type == &key_type_keyring) {
ret = keyring_detect_cycle(keyring, key);
if (ret < 0)
goto error2;
}
/* 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 error2;
klist = keyring->payload.subscriptions;
if (klist && klist->nkeys < klist->maxkeys) {
/* there's sufficient slack space to add directly */
atomic_inc(&key->usage);
write_lock(&keyring->lock);
klist->keys[klist->nkeys++] = key;
write_unlock(&keyring->lock);
ret = 0;
}
else {
/* grow the key list */
max = 4;
if (klist)
max += klist->maxkeys;
ret = -ENFILE;
size = sizeof(*klist) + sizeof(*key) * max;
if (size > PAGE_SIZE)
goto error3;
ret = -ENOMEM;
nklist = kmalloc(size, GFP_KERNEL);
if (!nklist)
goto error3;
nklist->maxkeys = max;
nklist->nkeys = 0;
if (klist) {
nklist->nkeys = klist->nkeys;
memcpy(nklist->keys,
klist->keys,
sizeof(struct key *) * klist->nkeys);
}
/* add the key into the new space */
atomic_inc(&key->usage);
write_lock(&keyring->lock);
keyring->payload.subscriptions = nklist;
nklist->keys[nklist->nkeys++] = key;
write_unlock(&keyring->lock);
/* dispose of the old keyring list */
kfree(klist);
ret = 0;
}
error2:
up_write(&keyring_serialise_link_sem);
error:
return ret;
error3:
/* undo the quota changes */
key_payload_reserve(keyring,
keyring->datalen - KEYQUOTA_LINK_BYTES);
goto error2;
} /* end __key_link() */
/*****************************************************************************/
/*
* link a key to a keyring
*/
int key_link(struct key *keyring, struct key *key)
{
int ret;
key_check(keyring);
key_check(key);
down_write(&keyring->sem);
ret = __key_link(keyring, key);
up_write(&keyring->sem);
return ret;
} /* end key_link() */
EXPORT_SYMBOL(key_link);
/*****************************************************************************/
/*
* unlink the first link to a key from a keyring
*/
int key_unlink(struct key *keyring, struct key *key)
{
struct keyring_list *klist;
int loop, ret;
key_check(keyring);
key_check(key);
ret = -ENOTDIR;
if (keyring->type != &key_type_keyring)
goto error;
down_write(&keyring->sem);
klist = keyring->payload.subscriptions;
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:
/* adjust the user's quota */
key_payload_reserve(keyring,
keyring->datalen - KEYQUOTA_LINK_BYTES);
/* shuffle down the key pointers
* - it might be worth shrinking the allocated memory, but that runs
* the risk of ENOMEM as we would have to copy
*/
write_lock(&keyring->lock);
klist->nkeys--;
if (loop < klist->nkeys)
memcpy(&klist->keys[loop],
&klist->keys[loop + 1],
(klist->nkeys - loop) * sizeof(struct key *));
write_unlock(&keyring->lock);
up_write(&keyring->sem);
key_put(key);
ret = 0;
error:
return ret;
} /* end key_unlink() */
EXPORT_SYMBOL(key_unlink);
/*****************************************************************************/
/*
* clear the specified process keyring
* - implements keyctl(KEYCTL_CLEAR)
*/
int keyring_clear(struct key *keyring)
{
struct keyring_list *klist;
int loop, ret;
ret = -ENOTDIR;
if (keyring->type == &key_type_keyring) {
/* detach the pointer block with the locks held */
down_write(&keyring->sem);
klist = keyring->payload.subscriptions;
if (klist) {
/* adjust the quota */
key_payload_reserve(keyring,
sizeof(struct keyring_list));
write_lock(&keyring->lock);
keyring->payload.subscriptions = NULL;
write_unlock(&keyring->lock);
}
up_write(&keyring->sem);
/* free the keys after the locks have been dropped */
if (klist) {
for (loop = klist->nkeys - 1; loop >= 0; loop--)
key_put(klist->keys[loop]);
kfree(klist);
}
ret = 0;
}
return ret;
} /* end keyring_clear() */
EXPORT_SYMBOL(keyring_clear);
