linux/security/keys/keyring.c
David Howells 0b0a84154e KEYS: request_key() should reget expired keys rather than give EKEYEXPIRED
Since the keyring facility can be viewed as a cache (at least in some
applications), the local expiration time on the key should probably be viewed
as a 'needs updating after this time' property rather than an absolute 'anyone
now wanting to use this object is out of luck' property.

Since request_key() is the main interface for the usage of keys, this should
update or replace an expired key rather than issuing EKEYEXPIRED if the local
expiration has been reached (ie. it should refresh the cache).

For absolute conditions where refreshing the cache probably doesn't help, the
key can be negatively instantiated using KEYCTL_REJECT_KEY with EKEYEXPIRED
given as the error to issue.  This will still cause request_key() to return
EKEYEXPIRED as that was explicitly set.

In the future, if the key type has an update op available, we might want to
upcall with the expired key and allow the upcall to update it.  We would pass
a different operation name (the first column in /etc/request-key.conf) to the
request-key program.

request_key() returning EKEYEXPIRED is causing an NFS problem which Chuck
Lever describes thusly:

	After about 10 minutes, my NFSv4 functional tests fail because the
	ownership of the test files goes to "-2". Looking at /proc/keys
	shows that the id_resolv keys that map to my test user ID have
	expired. The ownership problem persists until the expired keys are
	purged from the keyring, and fresh keys are obtained.

	I bisected the problem to 3.13 commit b2a4df200d ("KEYS: Expand
	the capacity of a keyring"). This commit inadvertantly changes the
	API contract of the internal function keyring_search_aux().

	The root cause appears to be that b2a4df200d made "no state check"
	the default behavior. "No state check" means the keyring search
	iterator function skips checking the key's expiry timeout, and
	returns expired keys.  request_key_and_link() depends on getting
	an -EAGAIN result code to know when to perform an upcall to refresh
	an expired key.

This patch can be tested directly by:

	keyctl request2 user debug:fred a @s
	keyctl timeout %user:debug:fred 3
	sleep 4
	keyctl request2 user debug:fred a @s

Without the patch, the last command gives error EKEYEXPIRED, but with the
command it gives a new key.

Reported-by: Carl Hetherington <cth@carlh.net>
Reported-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Chuck Lever <chuck.lever@oracle.com>
2014-12-01 22:52:53 +00:00

1395 lines
37 KiB
C

/* Keyring handling
*
* Copyright (C) 2004-2005, 2008, 2013 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 <keys/user-type.h>
#include <linux/assoc_array_priv.h>
#include <linux/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)
/*
* We mark pointers we pass to the associative array with bit 1 set if
* they're keyrings and clear otherwise.
*/
#define KEYRING_PTR_SUBTYPE 0x2UL
static inline bool keyring_ptr_is_keyring(const struct assoc_array_ptr *x)
{
return (unsigned long)x & KEYRING_PTR_SUBTYPE;
}
static inline struct key *keyring_ptr_to_key(const struct assoc_array_ptr *x)
{
void *object = assoc_array_ptr_to_leaf(x);
return (struct key *)((unsigned long)object & ~KEYRING_PTR_SUBTYPE);
}
static inline void *keyring_key_to_ptr(struct key *key)
{
if (key->type == &key_type_keyring)
return (void *)((unsigned long)key | KEYRING_PTR_SUBTYPE);
return key;
}
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_preparse(struct key_preparsed_payload *prep);
static void keyring_free_preparse(struct key_preparsed_payload *prep);
static int keyring_instantiate(struct key *keyring,
struct key_preparsed_payload *prep);
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 = 0,
.preparse = keyring_preparse,
.free_preparse = keyring_free_preparse,
.instantiate = keyring_instantiate,
.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);
}
}
/*
* Preparse a keyring payload
*/
static int keyring_preparse(struct key_preparsed_payload *prep)
{
return prep->datalen != 0 ? -EINVAL : 0;
}
/*
* Free a preparse of a user defined key payload
*/
static void keyring_free_preparse(struct key_preparsed_payload *prep)
{
}
/*
* Initialise a keyring.
*
* Returns 0 on success, -EINVAL if given any data.
*/
static int keyring_instantiate(struct key *keyring,
struct key_preparsed_payload *prep)
{
assoc_array_init(&keyring->keys);
/* make the keyring available by name if it has one */
keyring_publish_name(keyring);
return 0;
}
/*
* Multiply 64-bits by 32-bits to 96-bits and fold back to 64-bit. Ideally we'd
* fold the carry back too, but that requires inline asm.
*/
static u64 mult_64x32_and_fold(u64 x, u32 y)
{
u64 hi = (u64)(u32)(x >> 32) * y;
u64 lo = (u64)(u32)(x) * y;
return lo + ((u64)(u32)hi << 32) + (u32)(hi >> 32);
}
/*
* Hash a key type and description.
*/
static unsigned long hash_key_type_and_desc(const struct keyring_index_key *index_key)
{
const unsigned level_shift = ASSOC_ARRAY_LEVEL_STEP;
const unsigned long fan_mask = ASSOC_ARRAY_FAN_MASK;
const char *description = index_key->description;
unsigned long hash, type;
u32 piece;
u64 acc;
int n, desc_len = index_key->desc_len;
type = (unsigned long)index_key->type;
acc = mult_64x32_and_fold(type, desc_len + 13);
acc = mult_64x32_and_fold(acc, 9207);
for (;;) {
n = desc_len;
if (n <= 0)
break;
if (n > 4)
n = 4;
piece = 0;
memcpy(&piece, description, n);
description += n;
desc_len -= n;
acc = mult_64x32_and_fold(acc, piece);
acc = mult_64x32_and_fold(acc, 9207);
}
/* Fold the hash down to 32 bits if need be. */
hash = acc;
if (ASSOC_ARRAY_KEY_CHUNK_SIZE == 32)
hash ^= acc >> 32;
/* Squidge all the keyrings into a separate part of the tree to
* ordinary keys by making sure the lowest level segment in the hash is
* zero for keyrings and non-zero otherwise.
*/
if (index_key->type != &key_type_keyring && (hash & fan_mask) == 0)
return hash | (hash >> (ASSOC_ARRAY_KEY_CHUNK_SIZE - level_shift)) | 1;
if (index_key->type == &key_type_keyring && (hash & fan_mask) != 0)
return (hash + (hash << level_shift)) & ~fan_mask;
return hash;
}
/*
* Build the next index key chunk.
*
* On 32-bit systems the index key is laid out as:
*
* 0 4 5 9...
* hash desclen typeptr desc[]
*
* On 64-bit systems:
*
* 0 8 9 17...
* hash desclen typeptr desc[]
*
* We return it one word-sized chunk at a time.
*/
static unsigned long keyring_get_key_chunk(const void *data, int level)
{
const struct keyring_index_key *index_key = data;
unsigned long chunk = 0;
long offset = 0;
int desc_len = index_key->desc_len, n = sizeof(chunk);
level /= ASSOC_ARRAY_KEY_CHUNK_SIZE;
switch (level) {
case 0:
return hash_key_type_and_desc(index_key);
case 1:
return ((unsigned long)index_key->type << 8) | desc_len;
case 2:
if (desc_len == 0)
return (u8)((unsigned long)index_key->type >>
(ASSOC_ARRAY_KEY_CHUNK_SIZE - 8));
n--;
offset = 1;
default:
offset += sizeof(chunk) - 1;
offset += (level - 3) * sizeof(chunk);
if (offset >= desc_len)
return 0;
desc_len -= offset;
if (desc_len > n)
desc_len = n;
offset += desc_len;
do {
chunk <<= 8;
chunk |= ((u8*)index_key->description)[--offset];
} while (--desc_len > 0);
if (level == 2) {
chunk <<= 8;
chunk |= (u8)((unsigned long)index_key->type >>
(ASSOC_ARRAY_KEY_CHUNK_SIZE - 8));
}
return chunk;
}
}
static unsigned long keyring_get_object_key_chunk(const void *object, int level)
{
const struct key *key = keyring_ptr_to_key(object);
return keyring_get_key_chunk(&key->index_key, level);
}
static bool keyring_compare_object(const void *object, const void *data)
{
const struct keyring_index_key *index_key = data;
const struct key *key = keyring_ptr_to_key(object);
return key->index_key.type == index_key->type &&
key->index_key.desc_len == index_key->desc_len &&
memcmp(key->index_key.description, index_key->description,
index_key->desc_len) == 0;
}
/*
* Compare the index keys of a pair of objects and determine the bit position
* at which they differ - if they differ.
*/
static int keyring_diff_objects(const void *object, const void *data)
{
const struct key *key_a = keyring_ptr_to_key(object);
const struct keyring_index_key *a = &key_a->index_key;
const struct keyring_index_key *b = data;
unsigned long seg_a, seg_b;
int level, i;
level = 0;
seg_a = hash_key_type_and_desc(a);
seg_b = hash_key_type_and_desc(b);
if ((seg_a ^ seg_b) != 0)
goto differ;
/* The number of bits contributed by the hash is controlled by a
* constant in the assoc_array headers. Everything else thereafter we
* can deal with as being machine word-size dependent.
*/
level += ASSOC_ARRAY_KEY_CHUNK_SIZE / 8;
seg_a = a->desc_len;
seg_b = b->desc_len;
if ((seg_a ^ seg_b) != 0)
goto differ;
/* The next bit may not work on big endian */
level++;
seg_a = (unsigned long)a->type;
seg_b = (unsigned long)b->type;
if ((seg_a ^ seg_b) != 0)
goto differ;
level += sizeof(unsigned long);
if (a->desc_len == 0)
goto same;
i = 0;
if (((unsigned long)a->description | (unsigned long)b->description) &
(sizeof(unsigned long) - 1)) {
do {
seg_a = *(unsigned long *)(a->description + i);
seg_b = *(unsigned long *)(b->description + i);
if ((seg_a ^ seg_b) != 0)
goto differ_plus_i;
i += sizeof(unsigned long);
} while (i < (a->desc_len & (sizeof(unsigned long) - 1)));
}
for (; i < a->desc_len; i++) {
seg_a = *(unsigned char *)(a->description + i);
seg_b = *(unsigned char *)(b->description + i);
if ((seg_a ^ seg_b) != 0)
goto differ_plus_i;
}
same:
return -1;
differ_plus_i:
level += i;
differ:
i = level * 8 + __ffs(seg_a ^ seg_b);
return i;
}
/*
* Free an object after stripping the keyring flag off of the pointer.
*/
static void keyring_free_object(void *object)
{
key_put(keyring_ptr_to_key(object));
}
/*
* Operations for keyring management by the index-tree routines.
*/
static const struct assoc_array_ops keyring_assoc_array_ops = {
.get_key_chunk = keyring_get_key_chunk,
.get_object_key_chunk = keyring_get_object_key_chunk,
.compare_object = keyring_compare_object,
.diff_objects = keyring_diff_objects,
.free_object = keyring_free_object,
};
/*
* Clean up a keyring when it is destroyed. Unpublish its name if it had one
* and dispose of its data.
*
* The garbage collector detects the final key_put(), removes the keyring from
* the serial number tree and then does RCU synchronisation before coming here,
* so we shouldn't need to worry about code poking around here with the RCU
* readlock held by this time.
*/
static void keyring_destroy(struct key *keyring)
{
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);
}
assoc_array_destroy(&keyring->keys, &keyring_assoc_array_ops);
}
/*
* Describe a keyring for /proc.
*/
static void keyring_describe(const struct key *keyring, struct seq_file *m)
{
if (keyring->description)
seq_puts(m, keyring->description);
else
seq_puts(m, "[anon]");
if (key_is_instantiated(keyring)) {
if (keyring->keys.nr_leaves_on_tree != 0)
seq_printf(m, ": %lu", keyring->keys.nr_leaves_on_tree);
else
seq_puts(m, ": empty");
}
}
struct keyring_read_iterator_context {
size_t qty;
size_t count;
key_serial_t __user *buffer;
};
static int keyring_read_iterator(const void *object, void *data)
{
struct keyring_read_iterator_context *ctx = data;
const struct key *key = keyring_ptr_to_key(object);
int ret;
kenter("{%s,%d},,{%zu/%zu}",
key->type->name, key->serial, ctx->count, ctx->qty);
if (ctx->count >= ctx->qty)
return 1;
ret = put_user(key->serial, ctx->buffer);
if (ret < 0)
return ret;
ctx->buffer++;
ctx->count += sizeof(key->serial);
return 0;
}
/*
* Read a list of key IDs from the keyring's contents in binary form
*
* The keyring's semaphore is read-locked by the caller. This prevents someone
* from modifying it under us - which could cause us to read key IDs multiple
* times.
*/
static long keyring_read(const struct key *keyring,
char __user *buffer, size_t buflen)
{
struct keyring_read_iterator_context ctx;
unsigned long nr_keys;
int ret;
kenter("{%d},,%zu", key_serial(keyring), buflen);
if (buflen & (sizeof(key_serial_t) - 1))
return -EINVAL;
nr_keys = keyring->keys.nr_leaves_on_tree;
if (nr_keys == 0)
return 0;
/* Calculate how much data we could return */
ctx.qty = nr_keys * sizeof(key_serial_t);
if (!buffer || !buflen)
return ctx.qty;
if (buflen > ctx.qty)
ctx.qty = buflen;
/* Copy the IDs of the subscribed keys into the buffer */
ctx.buffer = (key_serial_t __user *)buffer;
ctx.count = 0;
ret = assoc_array_iterate(&keyring->keys, keyring_read_iterator, &ctx);
if (ret < 0) {
kleave(" = %d [iterate]", ret);
return ret;
}
kleave(" = %zu [ok]", ctx.count);
return ctx.count;
}
/*
* Allocate a keyring and link into the destination keyring.
*/
struct key *keyring_alloc(const char *description, kuid_t uid, kgid_t gid,
const struct cred *cred, key_perm_t perm,
unsigned long flags, struct key *dest)
{
struct key *keyring;
int ret;
keyring = key_alloc(&key_type_keyring, description,
uid, gid, cred, perm, 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;
}
EXPORT_SYMBOL(keyring_alloc);
/*
* By default, we keys found by getting an exact match on their descriptions.
*/
bool key_default_cmp(const struct key *key,
const struct key_match_data *match_data)
{
return strcmp(key->description, match_data->raw_data) == 0;
}
/*
* Iteration function to consider each key found.
*/
static int keyring_search_iterator(const void *object, void *iterator_data)
{
struct keyring_search_context *ctx = iterator_data;
const struct key *key = keyring_ptr_to_key(object);
unsigned long kflags = key->flags;
kenter("{%d}", key->serial);
/* ignore keys not of this type */
if (key->type != ctx->index_key.type) {
kleave(" = 0 [!type]");
return 0;
}
/* skip invalidated, revoked and expired keys */
if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
(1 << KEY_FLAG_REVOKED))) {
ctx->result = ERR_PTR(-EKEYREVOKED);
kleave(" = %d [invrev]", ctx->skipped_ret);
goto skipped;
}
if (key->expiry && ctx->now.tv_sec >= key->expiry) {
if (!(ctx->flags & KEYRING_SEARCH_SKIP_EXPIRED))
ctx->result = ERR_PTR(-EKEYEXPIRED);
kleave(" = %d [expire]", ctx->skipped_ret);
goto skipped;
}
}
/* keys that don't match */
if (!ctx->match_data.cmp(key, &ctx->match_data)) {
kleave(" = 0 [!match]");
return 0;
}
/* key must have search permissions */
if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
key_task_permission(make_key_ref(key, ctx->possessed),
ctx->cred, KEY_NEED_SEARCH) < 0) {
ctx->result = ERR_PTR(-EACCES);
kleave(" = %d [!perm]", ctx->skipped_ret);
goto skipped;
}
if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
/* we set a different error code if we pass a negative key */
if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
smp_rmb();
ctx->result = ERR_PTR(key->type_data.reject_error);
kleave(" = %d [neg]", ctx->skipped_ret);
goto skipped;
}
}
/* Found */
ctx->result = make_key_ref(key, ctx->possessed);
kleave(" = 1 [found]");
return 1;
skipped:
return ctx->skipped_ret;
}
/*
* Search inside a keyring for a key. We can search by walking to it
* directly based on its index-key or we can iterate over the entire
* tree looking for it, based on the match function.
*/
static int search_keyring(struct key *keyring, struct keyring_search_context *ctx)
{
if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_DIRECT) {
const void *object;
object = assoc_array_find(&keyring->keys,
&keyring_assoc_array_ops,
&ctx->index_key);
return object ? ctx->iterator(object, ctx) : 0;
}
return assoc_array_iterate(&keyring->keys, ctx->iterator, ctx);
}
/*
* Search a tree of keyrings that point to other keyrings up to the maximum
* depth.
*/
static bool search_nested_keyrings(struct key *keyring,
struct keyring_search_context *ctx)
{
struct {
struct key *keyring;
struct assoc_array_node *node;
int slot;
} stack[KEYRING_SEARCH_MAX_DEPTH];
struct assoc_array_shortcut *shortcut;
struct assoc_array_node *node;
struct assoc_array_ptr *ptr;
struct key *key;
int sp = 0, slot;
kenter("{%d},{%s,%s}",
keyring->serial,
ctx->index_key.type->name,
ctx->index_key.description);
#define STATE_CHECKS (KEYRING_SEARCH_NO_STATE_CHECK | KEYRING_SEARCH_DO_STATE_CHECK)
BUG_ON((ctx->flags & STATE_CHECKS) == 0 ||
(ctx->flags & STATE_CHECKS) == STATE_CHECKS);
if (ctx->index_key.description)
ctx->index_key.desc_len = strlen(ctx->index_key.description);
/* Check to see if this top-level keyring is what we are looking for
* and whether it is valid or not.
*/
if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_ITERATE ||
keyring_compare_object(keyring, &ctx->index_key)) {
ctx->skipped_ret = 2;
switch (ctx->iterator(keyring_key_to_ptr(keyring), ctx)) {
case 1:
goto found;
case 2:
return false;
default:
break;
}
}
ctx->skipped_ret = 0;
/* Start processing a new keyring */
descend_to_keyring:
kdebug("descend to %d", keyring->serial);
if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
(1 << KEY_FLAG_REVOKED)))
goto not_this_keyring;
/* Search through the keys in this keyring before its searching its
* subtrees.
*/
if (search_keyring(keyring, ctx))
goto found;
/* Then manually iterate through the keyrings nested in this one.
*
* Start from the root node of the index tree. Because of the way the
* hash function has been set up, keyrings cluster on the leftmost
* branch of the root node (root slot 0) or in the root node itself.
* Non-keyrings avoid the leftmost branch of the root entirely (root
* slots 1-15).
*/
ptr = ACCESS_ONCE(keyring->keys.root);
if (!ptr)
goto not_this_keyring;
if (assoc_array_ptr_is_shortcut(ptr)) {
/* If the root is a shortcut, either the keyring only contains
* keyring pointers (everything clusters behind root slot 0) or
* doesn't contain any keyring pointers.
*/
shortcut = assoc_array_ptr_to_shortcut(ptr);
smp_read_barrier_depends();
if ((shortcut->index_key[0] & ASSOC_ARRAY_FAN_MASK) != 0)
goto not_this_keyring;
ptr = ACCESS_ONCE(shortcut->next_node);
node = assoc_array_ptr_to_node(ptr);
goto begin_node;
}
node = assoc_array_ptr_to_node(ptr);
smp_read_barrier_depends();
ptr = node->slots[0];
if (!assoc_array_ptr_is_meta(ptr))
goto begin_node;
descend_to_node:
/* Descend to a more distal node in this keyring's content tree and go
* through that.
*/
kdebug("descend");
if (assoc_array_ptr_is_shortcut(ptr)) {
shortcut = assoc_array_ptr_to_shortcut(ptr);
smp_read_barrier_depends();
ptr = ACCESS_ONCE(shortcut->next_node);
BUG_ON(!assoc_array_ptr_is_node(ptr));
}
node = assoc_array_ptr_to_node(ptr);
begin_node:
kdebug("begin_node");
smp_read_barrier_depends();
slot = 0;
ascend_to_node:
/* Go through the slots in a node */
for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
ptr = ACCESS_ONCE(node->slots[slot]);
if (assoc_array_ptr_is_meta(ptr) && node->back_pointer)
goto descend_to_node;
if (!keyring_ptr_is_keyring(ptr))
continue;
key = keyring_ptr_to_key(ptr);
if (sp >= KEYRING_SEARCH_MAX_DEPTH) {
if (ctx->flags & KEYRING_SEARCH_DETECT_TOO_DEEP) {
ctx->result = ERR_PTR(-ELOOP);
return false;
}
goto not_this_keyring;
}
/* Search a nested keyring */
if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
key_task_permission(make_key_ref(key, ctx->possessed),
ctx->cred, KEY_NEED_SEARCH) < 0)
continue;
/* stack the current position */
stack[sp].keyring = keyring;
stack[sp].node = node;
stack[sp].slot = slot;
sp++;
/* begin again with the new keyring */
keyring = key;
goto descend_to_keyring;
}
/* We've dealt with all the slots in the current node, so now we need
* to ascend to the parent and continue processing there.
*/
ptr = ACCESS_ONCE(node->back_pointer);
slot = node->parent_slot;
if (ptr && assoc_array_ptr_is_shortcut(ptr)) {
shortcut = assoc_array_ptr_to_shortcut(ptr);
smp_read_barrier_depends();
ptr = ACCESS_ONCE(shortcut->back_pointer);
slot = shortcut->parent_slot;
}
if (!ptr)
goto not_this_keyring;
node = assoc_array_ptr_to_node(ptr);
smp_read_barrier_depends();
slot++;
/* If we've ascended to the root (zero backpointer), we must have just
* finished processing the leftmost branch rather than the root slots -
* so there can't be any more keyrings for us to find.
*/
if (node->back_pointer) {
kdebug("ascend %d", slot);
goto ascend_to_node;
}
/* The keyring we're looking at was disqualified or didn't contain a
* matching key.
*/
not_this_keyring:
kdebug("not_this_keyring %d", sp);
if (sp <= 0) {
kleave(" = false");
return false;
}
/* Resume the processing of a keyring higher up in the tree */
sp--;
keyring = stack[sp].keyring;
node = stack[sp].node;
slot = stack[sp].slot + 1;
kdebug("ascend to %d [%d]", keyring->serial, slot);
goto ascend_to_node;
/* We found a viable match */
found:
key = key_ref_to_ptr(ctx->result);
key_check(key);
if (!(ctx->flags & KEYRING_SEARCH_NO_UPDATE_TIME)) {
key->last_used_at = ctx->now.tv_sec;
keyring->last_used_at = ctx->now.tv_sec;
while (sp > 0)
stack[--sp].keyring->last_used_at = ctx->now.tv_sec;
}
kleave(" = true");
return true;
}
/**
* keyring_search_aux - Search a keyring tree for a key matching some criteria
* @keyring_ref: A pointer to the keyring with possession indicator.
* @ctx: The keyring search context.
*
* 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 can be 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,
struct keyring_search_context *ctx)
{
struct key *keyring;
long err;
ctx->iterator = keyring_search_iterator;
ctx->possessed = is_key_possessed(keyring_ref);
ctx->result = ERR_PTR(-EAGAIN);
keyring = key_ref_to_ptr(keyring_ref);
key_check(keyring);
if (keyring->type != &key_type_keyring)
return ERR_PTR(-ENOTDIR);
if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM)) {
err = key_task_permission(keyring_ref, ctx->cred, KEY_NEED_SEARCH);
if (err < 0)
return ERR_PTR(err);
}
rcu_read_lock();
ctx->now = current_kernel_time();
if (search_nested_keyrings(keyring, ctx))
__key_get(key_ref_to_ptr(ctx->result));
rcu_read_unlock();
return ctx->result;
}
/**
* 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 and preferred search method.
*/
key_ref_t keyring_search(key_ref_t keyring,
struct key_type *type,
const char *description)
{
struct keyring_search_context ctx = {
.index_key.type = type,
.index_key.description = description,
.cred = current_cred(),
.match_data.cmp = key_default_cmp,
.match_data.raw_data = description,
.match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
.flags = KEYRING_SEARCH_DO_STATE_CHECK,
};
key_ref_t key;
int ret;
if (type->match_preparse) {
ret = type->match_preparse(&ctx.match_data);
if (ret < 0)
return ERR_PTR(ret);
}
key = keyring_search_aux(keyring, &ctx);
if (type->match_free)
type->match_free(&ctx.match_data);
return key;
}
EXPORT_SYMBOL(keyring_search);
/*
* Search the given keyring for a key that might be updated.
*
* The caller must guarantee that the keyring is a keyring and that the
* permission is granted to modify the keyring as no check is made here. The
* caller must also hold a lock on the keyring semaphore.
*
* Returns a pointer to the found key with usage count incremented if
* successful and returns NULL if not found. Revoked and invalidated keys are
* skipped over.
*
* If successful, the possession indicator is propagated from the keyring ref
* to the returned key reference.
*/
key_ref_t find_key_to_update(key_ref_t keyring_ref,
const struct keyring_index_key *index_key)
{
struct key *keyring, *key;
const void *object;
keyring = key_ref_to_ptr(keyring_ref);
kenter("{%d},{%s,%s}",
keyring->serial, index_key->type->name, index_key->description);
object = assoc_array_find(&keyring->keys, &keyring_assoc_array_ops,
index_key);
if (object)
goto found;
kleave(" = NULL");
return NULL;
found:
key = keyring_ptr_to_key(object);
if (key->flags & ((1 << KEY_FLAG_INVALIDATED) |
(1 << KEY_FLAG_REVOKED))) {
kleave(" = NULL [x]");
return NULL;
}
__key_get(key);
kleave(" = {%d}", key->serial);
return make_key_ref(key, is_key_possessed(keyring_ref));
}
/*
* 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 (!kuid_has_mapping(current_user_ns(), keyring->user->uid))
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_NEED_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;
keyring->last_used_at = current_kernel_time().tv_sec;
goto out;
}
}
keyring = ERR_PTR(-ENOKEY);
out:
read_unlock(&keyring_name_lock);
return keyring;
}
static int keyring_detect_cycle_iterator(const void *object,
void *iterator_data)
{
struct keyring_search_context *ctx = iterator_data;
const struct key *key = keyring_ptr_to_key(object);
kenter("{%d}", key->serial);
/* We might get a keyring with matching index-key that is nonetheless a
* different keyring. */
if (key != ctx->match_data.raw_data)
return 0;
ctx->result = ERR_PTR(-EDEADLK);
return 1;
}
/*
* 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 keyring_search_context ctx = {
.index_key = A->index_key,
.match_data.raw_data = A,
.match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
.iterator = keyring_detect_cycle_iterator,
.flags = (KEYRING_SEARCH_NO_STATE_CHECK |
KEYRING_SEARCH_NO_UPDATE_TIME |
KEYRING_SEARCH_NO_CHECK_PERM |
KEYRING_SEARCH_DETECT_TOO_DEEP),
};
rcu_read_lock();
search_nested_keyrings(B, &ctx);
rcu_read_unlock();
return PTR_ERR(ctx.result) == -EAGAIN ? 0 : PTR_ERR(ctx.result);
}
/*
* Preallocate memory so that a key can be linked into to a keyring.
*/
int __key_link_begin(struct key *keyring,
const struct keyring_index_key *index_key,
struct assoc_array_edit **_edit)
__acquires(&keyring->sem)
__acquires(&keyring_serialise_link_sem)
{
struct assoc_array_edit *edit;
int ret;
kenter("%d,%s,%s,",
keyring->serial, index_key->type->name, index_key->description);
BUG_ON(index_key->desc_len == 0);
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 (index_key->type == &key_type_keyring)
down_write(&keyring_serialise_link_sem);
/* Create an edit script that will insert/replace the key in the
* keyring tree.
*/
edit = assoc_array_insert(&keyring->keys,
&keyring_assoc_array_ops,
index_key,
NULL);
if (IS_ERR(edit)) {
ret = PTR_ERR(edit);
goto error_sem;
}
/* If we're not replacing a link in-place then we're going to need some
* extra quota.
*/
if (!edit->dead_leaf) {
ret = key_payload_reserve(keyring,
keyring->datalen + KEYQUOTA_LINK_BYTES);
if (ret < 0)
goto error_cancel;
}
*_edit = edit;
kleave(" = 0");
return 0;
error_cancel:
assoc_array_cancel_edit(edit);
error_sem:
if (index_key->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 *key, struct assoc_array_edit **_edit)
{
__key_get(key);
assoc_array_insert_set_object(*_edit, keyring_key_to_ptr(key));
assoc_array_apply_edit(*_edit);
*_edit = NULL;
}
/*
* 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,
const struct keyring_index_key *index_key,
struct assoc_array_edit *edit)
__releases(&keyring->sem)
__releases(&keyring_serialise_link_sem)
{
BUG_ON(index_key->type == NULL);
kenter("%d,%s,", keyring->serial, index_key->type->name);
if (index_key->type == &key_type_keyring)
up_write(&keyring_serialise_link_sem);
if (edit && !edit->dead_leaf) {
key_payload_reserve(keyring,
keyring->datalen - KEYQUOTA_LINK_BYTES);
assoc_array_cancel_edit(edit);
}
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)
{
struct assoc_array_edit *edit;
int ret;
kenter("{%d,%d}", keyring->serial, atomic_read(&keyring->usage));
key_check(keyring);
key_check(key);
if (test_bit(KEY_FLAG_TRUSTED_ONLY, &keyring->flags) &&
!test_bit(KEY_FLAG_TRUSTED, &key->flags))
return -EPERM;
ret = __key_link_begin(keyring, &key->index_key, &edit);
if (ret == 0) {
kdebug("begun {%d,%d}", keyring->serial, atomic_read(&keyring->usage));
ret = __key_link_check_live_key(keyring, key);
if (ret == 0)
__key_link(key, &edit);
__key_link_end(keyring, &key->index_key, edit);
}
kleave(" = %d {%d,%d}", ret, keyring->serial, atomic_read(&keyring->usage));
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 assoc_array_edit *edit;
int ret;
key_check(keyring);
key_check(key);
if (keyring->type != &key_type_keyring)
return -ENOTDIR;
down_write(&keyring->sem);
edit = assoc_array_delete(&keyring->keys, &keyring_assoc_array_ops,
&key->index_key);
if (IS_ERR(edit)) {
ret = PTR_ERR(edit);
goto error;
}
ret = -ENOENT;
if (edit == NULL)
goto error;
assoc_array_apply_edit(edit);
key_payload_reserve(keyring, keyring->datalen - KEYQUOTA_LINK_BYTES);
ret = 0;
error:
up_write(&keyring->sem);
return ret;
}
EXPORT_SYMBOL(key_unlink);
/**
* 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 assoc_array_edit *edit;
int ret;
if (keyring->type != &key_type_keyring)
return -ENOTDIR;
down_write(&keyring->sem);
edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
if (IS_ERR(edit)) {
ret = PTR_ERR(edit);
} else {
if (edit)
assoc_array_apply_edit(edit);
key_payload_reserve(keyring, 0);
ret = 0;
}
up_write(&keyring->sem);
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 assoc_array_edit *edit;
edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
if (!IS_ERR(edit)) {
if (edit)
assoc_array_apply_edit(edit);
key_payload_reserve(keyring, 0);
}
}
static bool keyring_gc_select_iterator(void *object, void *iterator_data)
{
struct key *key = keyring_ptr_to_key(object);
time_t *limit = iterator_data;
if (key_is_dead(key, *limit))
return false;
key_get(key);
return true;
}
static int keyring_gc_check_iterator(const void *object, void *iterator_data)
{
const struct key *key = keyring_ptr_to_key(object);
time_t *limit = iterator_data;
key_check(key);
return key_is_dead(key, *limit);
}
/*
* Garbage collect pointers from a keyring.
*
* Not called with any locks held. The keyring's key struct will not be
* deallocated under us as only our caller may deallocate it.
*/
void keyring_gc(struct key *keyring, time_t limit)
{
int result;
kenter("%x{%s}", keyring->serial, keyring->description ?: "");
if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
(1 << KEY_FLAG_REVOKED)))
goto dont_gc;
/* scan the keyring looking for dead keys */
rcu_read_lock();
result = assoc_array_iterate(&keyring->keys,
keyring_gc_check_iterator, &limit);
rcu_read_unlock();
if (result == true)
goto do_gc;
dont_gc:
kleave(" [no gc]");
return;
do_gc:
down_write(&keyring->sem);
assoc_array_gc(&keyring->keys, &keyring_assoc_array_ops,
keyring_gc_select_iterator, &limit);
up_write(&keyring->sem);
kleave(" [gc]");
}