Viewing: keyring.c
// SPDX-License-Identifier: GPL-2.0
/*
* Filesystem-level keyring for llcrypt
*
* Copyright 2019 Google LLC
*/
/*
* This file implements management of llcrypt master keys in the
* filesystem-level keyring, including the ioctls:
*
* - LL_IOC_ADD_ENCRYPTION_KEY
* - LL_IOC_REMOVE_ENCRYPTION_KEY
* - LL_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS
* - LL_IOC_GET_ENCRYPTION_KEY_STATUS
*
* See the "User API" section of Documentation/filesystems/llcrypt.rst for more
* information about these ioctls.
*/
/*
* Linux commit 219d54332a09
* tags/v5.4
*/
#include <crypto/skcipher.h>
#include <linux/key-type.h>
#include <linux/seq_file.h>
#include "llcrypt_private.h"
static void wipe_master_key_secret(struct llcrypt_master_key_secret *secret)
{
llcrypt_destroy_hkdf(&secret->hkdf);
memzero_explicit(secret, sizeof(*secret));
}
static void move_master_key_secret(struct llcrypt_master_key_secret *dst,
struct llcrypt_master_key_secret *src)
{
memcpy(dst, src, sizeof(*dst));
memzero_explicit(src, sizeof(*src));
}
static void free_master_key(struct llcrypt_master_key *mk)
{
size_t i;
wipe_master_key_secret(&mk->mk_secret);
for (i = 0; i < ARRAY_SIZE(mk->mk_mode_keys); i++)
crypto_free_skcipher(mk->mk_mode_keys[i]);
key_put(mk->mk_users);
kfree_sensitive(mk);
}
static inline bool valid_key_spec(const struct llcrypt_key_specifier *spec)
{
if (spec->__reserved)
return false;
return master_key_spec_len(spec) != 0;
}
static int llcrypt_key_instantiate(struct key *key,
struct key_preparsed_payload *prep)
{
key->payload.data[0] = (struct llcrypt_master_key *)prep->data;
return 0;
}
static void llcrypt_key_destroy(struct key *key)
{
free_master_key(key->payload.data[0]);
}
static void llcrypt_key_describe(const struct key *key, struct seq_file *m)
{
seq_puts(m, key->description);
if (key_is_positive(key)) {
const struct llcrypt_master_key *mk = key->payload.data[0];
if (!is_master_key_secret_present(&mk->mk_secret))
seq_puts(m, ": secret removed");
}
}
/*
* Type of key in ->lsi_master_keys. Each key of this type represents a master
* key which has been added to the filesystem. Its payload is a
* 'struct llcrypt_master_key'. The "." prefix in the key type name prevents
* users from adding keys of this type via the keyrings syscalls rather than via
* the intended method of LL_IOC_ADD_ENCRYPTION_KEY.
*/
static struct key_type key_type_llcrypt = {
.name = "._llcrypt",
.instantiate = llcrypt_key_instantiate,
.destroy = llcrypt_key_destroy,
.describe = llcrypt_key_describe,
};
static int llcrypt_user_key_instantiate(struct key *key,
struct key_preparsed_payload *prep)
{
/*
* We just charge LLCRYPT_MAX_KEY_SIZE bytes to the user's key quota for
* each key, regardless of the exact key size. The amount of memory
* actually used is greater than the size of the raw key anyway.
*/
return key_payload_reserve(key, LLCRYPT_MAX_KEY_SIZE);
}
static void llcrypt_user_key_describe(const struct key *key, struct seq_file *m)
{
seq_puts(m, key->description);
}
/*
* Type of key in ->mk_users. Each key of this type represents a particular
* user who has added a particular master key.
*
* Note that the name of this key type really should be something like
* ".llcrypt-user" instead of simply ".llcrypt". But the shorter name is chosen
* mainly for simplicity of presentation in /proc/keys when read by a non-root
* user. And it is expected to be rare that a key is actually added by multiple
* users, since users should keep their encryption keys confidential.
*/
static struct key_type key_type_llcrypt_user = {
.name = ".llcrypt",
.instantiate = llcrypt_user_key_instantiate,
.describe = llcrypt_user_key_describe,
};
/* Search ->lsi_master_keys or ->mk_users */
static struct key *search_llcrypt_keyring(struct key *keyring,
struct key_type *type,
const char *description)
{
/*
* We need to mark the keyring reference as "possessed" so that we
* acquire permission to search it, via the KEY_POS_SEARCH permission.
*/
key_ref_t keyref = make_key_ref(keyring, true /* possessed */);
#ifdef HAVE_KEYRING_SEARCH_4ARGS
keyref = keyring_search(keyref, type, description, false);
#else
keyref = keyring_search(keyref, type, description);
#endif
if (IS_ERR(keyref)) {
if (PTR_ERR(keyref) == -EAGAIN || /* not found */
PTR_ERR(keyref) == -EKEYREVOKED) /* recently invalidated */
keyref = ERR_PTR(-ENOKEY);
return ERR_CAST(keyref);
}
return key_ref_to_ptr(keyref);
}
#define LLCRYPT_FS_KEYRING_DESCRIPTION_SIZE \
(CONST_STRLEN("llcrypt-") + sizeof_field(struct super_block, s_id))
#define LLCRYPT_MK_DESCRIPTION_SIZE (2 * LLCRYPT_KEY_IDENTIFIER_SIZE + 1)
#define LLCRYPT_MK_USERS_DESCRIPTION_SIZE \
(CONST_STRLEN("llcrypt-") + 2 * LLCRYPT_KEY_IDENTIFIER_SIZE + \
CONST_STRLEN("-users") + 1)
#define LLCRYPT_MK_USER_DESCRIPTION_SIZE \
(2 * LLCRYPT_KEY_IDENTIFIER_SIZE + CONST_STRLEN(".uid.") + 10 + 1)
static void format_fs_keyring_description(
char description[LLCRYPT_FS_KEYRING_DESCRIPTION_SIZE],
const struct super_block *sb)
{
sprintf(description, "llcrypt-%s", sb->s_id);
}
static void format_mk_description(
char description[LLCRYPT_MK_DESCRIPTION_SIZE],
const struct llcrypt_key_specifier *mk_spec)
{
sprintf(description, "%*phN",
master_key_spec_len(mk_spec), (u8 *)&mk_spec->u);
}
static void format_mk_users_keyring_description(
char description[LLCRYPT_MK_USERS_DESCRIPTION_SIZE],
const u8 mk_identifier[LLCRYPT_KEY_IDENTIFIER_SIZE])
{
sprintf(description, "llcrypt-%*phN-users",
LLCRYPT_KEY_IDENTIFIER_SIZE, mk_identifier);
}
static void format_mk_user_description(
char description[LLCRYPT_MK_USER_DESCRIPTION_SIZE],
const u8 mk_identifier[LLCRYPT_KEY_IDENTIFIER_SIZE])
{
sprintf(description, "%*phN.uid.%u", LLCRYPT_KEY_IDENTIFIER_SIZE,
mk_identifier, __kuid_val(current_fsuid()));
}
/* Create ->lsi_master_keys if needed. Synchronized by llcrypt_add_key_mutex. */
static int allocate_filesystem_keyring(struct super_block *sb)
{
char description[LLCRYPT_FS_KEYRING_DESCRIPTION_SIZE];
struct key *keyring;
struct lustre_sb_info *lsi = s2lsi(sb);
if (!lsi)
return -EINVAL;
if (lsi->lsi_master_keys)
return 0;
format_fs_keyring_description(description, sb);
keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
current_cred(), KEY_POS_SEARCH |
KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW,
KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
if (IS_ERR(keyring))
return PTR_ERR(keyring);
/* Pairs with READ_ONCE() in llcrypt_find_master_key() */
smp_store_release(&lsi->lsi_master_keys, keyring);
return 0;
}
void llcrypt_sb_free(struct lustre_sb_info *lsi)
{
if (lsi != NULL) {
key_put(lsi->lsi_master_keys);
lsi->lsi_master_keys = NULL;
}
}
EXPORT_SYMBOL(llcrypt_sb_free);
/*
* Find the specified master key in ->lsi_master_keys.
* Returns ERR_PTR(-ENOKEY) if not found.
*/
struct key *llcrypt_find_master_key(struct super_block *sb,
const struct llcrypt_key_specifier *mk_spec)
{
struct key *keyring;
char description[LLCRYPT_MK_DESCRIPTION_SIZE];
struct lustre_sb_info *lsi = s2lsi(sb);
if (!lsi)
return ERR_PTR(-EINVAL);
/* pairs with smp_store_release() in allocate_filesystem_keyring() */
keyring = READ_ONCE(lsi->lsi_master_keys);
if (keyring == NULL)
return ERR_PTR(-ENOKEY); /* No keyring yet, so no keys yet. */
format_mk_description(description, mk_spec);
return search_llcrypt_keyring(keyring, &key_type_llcrypt, description);
}
static int allocate_master_key_users_keyring(struct llcrypt_master_key *mk)
{
char description[LLCRYPT_MK_USERS_DESCRIPTION_SIZE];
struct key *keyring;
format_mk_users_keyring_description(description,
mk->mk_spec.u.identifier);
keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
current_cred(), KEY_POS_SEARCH |
KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW,
KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
if (IS_ERR(keyring))
return PTR_ERR(keyring);
mk->mk_users = keyring;
return 0;
}
/*
* Find the current user's "key" in the master key's ->mk_users.
* Returns ERR_PTR(-ENOKEY) if not found.
*/
static struct key *find_master_key_user(struct llcrypt_master_key *mk)
{
char description[LLCRYPT_MK_USER_DESCRIPTION_SIZE];
format_mk_user_description(description, mk->mk_spec.u.identifier);
return search_llcrypt_keyring(mk->mk_users, &key_type_llcrypt_user,
description);
}
/*
* Give the current user a "key" in ->mk_users. This charges the user's quota
* and marks the master key as added by the current user, so that it cannot be
* removed by another user with the key. Either the master key's key->sem must
* be held for write, or the master key must be still undergoing initialization.
*/
static int add_master_key_user(struct llcrypt_master_key *mk)
{
char description[LLCRYPT_MK_USER_DESCRIPTION_SIZE];
struct key *mk_user;
int err;
format_mk_user_description(description, mk->mk_spec.u.identifier);
mk_user = key_alloc(&key_type_llcrypt_user, description,
current_fsuid(), current_gid(), current_cred(),
KEY_POS_SEARCH | KEY_USR_VIEW, 0, NULL);
if (IS_ERR(mk_user))
return PTR_ERR(mk_user);
err = key_instantiate_and_link(mk_user, NULL, 0, mk->mk_users, NULL);
key_put(mk_user);
return err;
}
/*
* Remove the current user's "key" from ->mk_users.
* The master key's key->sem must be held for write.
*
* Returns 0 if removed, -ENOKEY if not found, or another -errno code.
*/
static int remove_master_key_user(struct llcrypt_master_key *mk)
{
struct key *mk_user;
int err;
mk_user = find_master_key_user(mk);
if (IS_ERR(mk_user))
return PTR_ERR(mk_user);
err = key_unlink(mk->mk_users, mk_user);
key_put(mk_user);
return err;
}
/*
* Allocate a new llcrypt_master_key which contains the given secret, set it as
* the payload of a new 'struct key' of type llcrypt, and link the 'struct key'
* into the given keyring. Synchronized by llcrypt_add_key_mutex.
*/
static int add_new_master_key(struct llcrypt_master_key_secret *secret,
const struct llcrypt_key_specifier *mk_spec,
struct key *keyring)
{
struct llcrypt_master_key *mk;
char description[LLCRYPT_MK_DESCRIPTION_SIZE];
struct key *key;
int err;
mk = kzalloc(sizeof(*mk), GFP_KERNEL);
if (!mk)
return -ENOMEM;
mk->mk_spec = *mk_spec;
move_master_key_secret(&mk->mk_secret, secret);
init_rwsem(&mk->mk_secret_sem);
refcount_set(&mk->mk_refcount, 1); /* secret is present */
INIT_LIST_HEAD(&mk->mk_decrypted_inodes);
spin_lock_init(&mk->mk_decrypted_inodes_lock);
if (mk_spec->type == LLCRYPT_KEY_SPEC_TYPE_IDENTIFIER) {
err = allocate_master_key_users_keyring(mk);
if (err)
goto out_free_mk;
err = add_master_key_user(mk);
if (err)
goto out_free_mk;
}
/*
* Note that we don't charge this key to anyone's quota, since when
* ->mk_users is in use those keys are charged instead, and otherwise
* (when ->mk_users isn't in use) only root can add these keys.
*/
format_mk_description(description, mk_spec);
key = key_alloc(&key_type_llcrypt, description,
GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
KEY_POS_SEARCH | KEY_USR_SEARCH | KEY_USR_VIEW,
KEY_ALLOC_NOT_IN_QUOTA, NULL);
if (IS_ERR(key)) {
err = PTR_ERR(key);
goto out_free_mk;
}
err = key_instantiate_and_link(key, mk, sizeof(*mk), keyring, NULL);
key_put(key);
if (err)
goto out_free_mk;
return 0;
out_free_mk:
free_master_key(mk);
return err;
}
#define KEY_DEAD 1
static int add_existing_master_key(struct llcrypt_master_key *mk,
struct llcrypt_master_key_secret *secret)
{
struct key *mk_user;
bool rekey;
int err;
/*
* If the current user is already in ->mk_users, then there's nothing to
* do. (Not applicable for v1 policy keys, which have NULL ->mk_users.)
*/
if (mk->mk_users) {
mk_user = find_master_key_user(mk);
if (mk_user != ERR_PTR(-ENOKEY)) {
if (IS_ERR(mk_user))
return PTR_ERR(mk_user);
key_put(mk_user);
return 0;
}
}
/* If we'll be re-adding ->mk_secret, try to take the reference. */
rekey = !is_master_key_secret_present(&mk->mk_secret);
if (rekey && !refcount_inc_not_zero(&mk->mk_refcount))
return KEY_DEAD;
/* Add the current user to ->mk_users, if applicable. */
if (mk->mk_users) {
err = add_master_key_user(mk);
if (err) {
if (rekey && refcount_dec_and_test(&mk->mk_refcount))
return KEY_DEAD;
return err;
}
}
/* Re-add the secret if needed. */
if (rekey) {
down_write(&mk->mk_secret_sem);
move_master_key_secret(&mk->mk_secret, secret);
up_write(&mk->mk_secret_sem);
}
return 0;
}
static int add_master_key(struct super_block *sb,
struct llcrypt_master_key_secret *secret,
const struct llcrypt_key_specifier *mk_spec)
{
static DEFINE_MUTEX(llcrypt_add_key_mutex);
struct key *key;
struct lustre_sb_info *lsi = s2lsi(sb);
int err;
if (!lsi)
return -EINVAL;
mutex_lock(&llcrypt_add_key_mutex); /* serialize find + link */
retry:
key = llcrypt_find_master_key(sb, mk_spec);
if (IS_ERR(key)) {
err = PTR_ERR(key);
if (err != -ENOKEY)
goto out_unlock;
/* Didn't find the key in ->lsi_master_keys. Add it. */
err = allocate_filesystem_keyring(sb);
if (err)
goto out_unlock;
err = add_new_master_key(secret, mk_spec,
lsi->lsi_master_keys);
} else {
/*
* Found the key in ->lsi_master_keys. Re-add the secret if
* needed, and add the user to ->mk_users if needed.
*/
down_write(&key->sem);
err = add_existing_master_key(key->payload.data[0], secret);
up_write(&key->sem);
if (err == KEY_DEAD) {
/* Key being removed or needs to be removed */
key_invalidate(key);
key_put(key);
goto retry;
}
key_put(key);
}
out_unlock:
mutex_unlock(&llcrypt_add_key_mutex);
return err;
}
/*
* Add a master encryption key to the filesystem, causing all files which were
* encrypted with it to appear "unlocked" (decrypted) when accessed.
*
* When adding a key for use by v1 encryption policies, this ioctl is
* privileged, and userspace must provide the 'key_descriptor'.
*
* When adding a key for use by v2+ encryption policies, this ioctl is
* unprivileged. This is needed, in general, to allow non-root users to use
* encryption without encountering the visibility problems of process-subscribed
* keyrings and the inability to properly remove keys. This works by having
* each key identified by its cryptographically secure hash --- the
* 'key_identifier'. The cryptographic hash ensures that a malicious user
* cannot add the wrong key for a given identifier. Furthermore, each added key
* is charged to the appropriate user's quota for the keyrings service, which
* prevents a malicious user from adding too many keys. Finally, we forbid a
* user from removing a key while other users have added it too, which prevents
* a user who knows another user's key from causing a denial-of-service by
* removing it at an inopportune time. (We tolerate that a user who knows a key
* can prevent other users from removing it.)
*
* For more details, see the "LL_IOC_ADD_ENCRYPTION_KEY" section of
* Documentation/filesystems/llcrypt.rst.
*/
int llcrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
{
struct super_block *sb = file_inode(filp)->i_sb;
struct llcrypt_add_key_arg __user *uarg = _uarg;
struct llcrypt_add_key_arg arg;
struct llcrypt_master_key_secret secret;
int err;
if (copy_from_user(&arg, uarg, sizeof(arg)))
return -EFAULT;
if (!valid_key_spec(&arg.key_spec))
return -EINVAL;
if (arg.raw_size < LLCRYPT_MIN_KEY_SIZE ||
arg.raw_size > LLCRYPT_MAX_KEY_SIZE)
return -EINVAL;
if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
return -EINVAL;
memset(&secret, 0, sizeof(secret));
secret.size = arg.raw_size;
err = -EFAULT;
if (copy_from_user(secret.raw, uarg->raw, secret.size))
goto out_wipe_secret;
switch (arg.key_spec.type) {
case LLCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
/*
* Only root can add keys that are identified by an arbitrary
* descriptor rather than by a cryptographic hash --- since
* otherwise a malicious user could add the wrong key.
*/
err = -EACCES;
if (!capable(CAP_SYS_ADMIN))
goto out_wipe_secret;
break;
case LLCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
err = llcrypt_init_hkdf(&secret.hkdf, secret.raw, secret.size);
if (err)
goto out_wipe_secret;
/*
* Now that the HKDF context is initialized, the raw key is no
* longer needed.
*/
memzero_explicit(secret.raw, secret.size);
/* Calculate the key identifier and return it to userspace. */
err = llcrypt_hkdf_expand(&secret.hkdf,
HKDF_CONTEXT_KEY_IDENTIFIER,
NULL, 0, arg.key_spec.u.identifier,
LLCRYPT_KEY_IDENTIFIER_SIZE);
if (err)
goto out_wipe_secret;
err = -EFAULT;
if (copy_to_user(uarg->key_spec.u.identifier,
arg.key_spec.u.identifier,
LLCRYPT_KEY_IDENTIFIER_SIZE))
goto out_wipe_secret;
break;
default:
WARN_ON(1);
err = -EINVAL;
goto out_wipe_secret;
}
err = add_master_key(sb, &secret, &arg.key_spec);
out_wipe_secret:
wipe_master_key_secret(&secret);
return err;
}
EXPORT_SYMBOL_GPL(llcrypt_ioctl_add_key);
/*
* Verify that the current user has added a master key with the given identifier
* (returns -ENOKEY if not). This is needed to prevent a user from encrypting
* their files using some other user's key which they don't actually know.
* Cryptographically this isn't much of a problem, but the semantics of this
* would be a bit weird, so it's best to just forbid it.
*
* The system administrator (CAP_FOWNER) can override this, which should be
* enough for any use cases where encryption policies are being set using keys
* that were chosen ahead of time but aren't available at the moment.
*
* Note that the key may have already removed by the time this returns, but
* that's okay; we just care whether the key was there at some point.
*
* Return: 0 if the key is added, -ENOKEY if it isn't, or another -errno code
*/
int llcrypt_verify_key_added(struct super_block *sb,
const u8 identifier[LLCRYPT_KEY_IDENTIFIER_SIZE])
{
struct llcrypt_key_specifier mk_spec;
struct key *key, *mk_user;
struct llcrypt_master_key *mk;
int err;
mk_spec.type = LLCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
memcpy(mk_spec.u.identifier, identifier, LLCRYPT_KEY_IDENTIFIER_SIZE);
key = llcrypt_find_master_key(sb, &mk_spec);
if (IS_ERR(key)) {
err = PTR_ERR(key);
goto out;
}
mk = key->payload.data[0];
mk_user = find_master_key_user(mk);
if (IS_ERR(mk_user)) {
err = PTR_ERR(mk_user);
} else {
key_put(mk_user);
err = 0;
}
key_put(key);
out:
if (err == -ENOKEY && capable(CAP_FOWNER))
err = 0;
return err;
}
/*
* Try to evict the inode's dentries from the dentry cache. If the inode is a
* directory, then it can have at most one dentry; however, that dentry may be
* pinned by child dentries, so first try to evict the children too.
*/
static void shrink_dcache_inode(struct inode *inode)
{
struct dentry *dentry;
if (S_ISDIR(inode->i_mode)) {
dentry = d_find_any_alias(inode);
if (dentry) {
shrink_dcache_parent(dentry);
dput(dentry);
}
}
d_prune_aliases(inode);
}
static void evict_dentries_for_decrypted_inodes(struct llcrypt_master_key *mk)
{
struct llcrypt_info *ci;
struct inode *inode;
struct inode *toput_inode = NULL;
spin_lock(&mk->mk_decrypted_inodes_lock);
list_for_each_entry(ci, &mk->mk_decrypted_inodes, ci_master_key_link) {
inode = ci->ci_inode;
if (igrab(inode) == NULL)
continue;
spin_unlock(&mk->mk_decrypted_inodes_lock);
shrink_dcache_inode(inode);
iput(toput_inode);
toput_inode = inode;
spin_lock(&mk->mk_decrypted_inodes_lock);
}
spin_unlock(&mk->mk_decrypted_inodes_lock);
iput(toput_inode);
}
static int check_for_busy_inodes(struct super_block *sb,
struct llcrypt_master_key *mk)
{
struct list_head *pos;
size_t busy_count = 0;
unsigned long ino;
struct dentry *dentry;
char _path[256];
char *path = NULL;
spin_lock(&mk->mk_decrypted_inodes_lock);
list_for_each(pos, &mk->mk_decrypted_inodes)
busy_count++;
if (busy_count == 0) {
spin_unlock(&mk->mk_decrypted_inodes_lock);
return 0;
}
{
/* select an example file to show for debugging purposes */
struct inode *inode =
list_first_entry(&mk->mk_decrypted_inodes,
struct llcrypt_info,
ci_master_key_link)->ci_inode;
ino = inode->i_ino;
dentry = d_find_alias(inode);
}
spin_unlock(&mk->mk_decrypted_inodes_lock);
if (dentry) {
path = dentry_path_raw(dentry, _path, sizeof(_path));
dput(dentry);
}
if (IS_ERR_OR_NULL(path))
path = "(unknown)";
llcrypt_warn(NULL,
"%s: %zu inode(s) still busy after removing key with %s %*phN, including ino %lu (%s)",
sb->s_id, busy_count, master_key_spec_type(&mk->mk_spec),
master_key_spec_len(&mk->mk_spec), (u8 *)&mk->mk_spec.u,
ino, path);
return -EBUSY;
}
static int try_to_lock_encrypted_files(struct super_block *sb,
struct llcrypt_master_key *mk)
{
int err1;
int err2;
/*
* An inode can't be evicted while it is dirty or has dirty pages.
* Thus, we first have to clean the inodes in ->mk_decrypted_inodes.
*
* Just do it the easy way: call sync_filesystem(). It's overkill, but
* it works, and it's more important to minimize the amount of caches we
* drop than the amount of data we sync. Also, unprivileged users can
* already call sync_filesystem() via sys_syncfs() or sys_sync().
*/
down_read(&sb->s_umount);
err1 = sync_filesystem(sb);
up_read(&sb->s_umount);
/* If a sync error occurs, still try to evict as much as possible. */
/*
* Inodes are pinned by their dentries, so we have to evict their
* dentries. shrink_dcache_sb() would suffice, but would be overkill
* and inappropriate for use by unprivileged users. So instead go
* through the inodes' alias lists and try to evict each dentry.
*/
evict_dentries_for_decrypted_inodes(mk);
/*
* evict_dentries_for_decrypted_inodes() already iput() each inode in
* the list; any inodes for which that dropped the last reference will
* have been evicted due to llcrypt_drop_inode() detecting the key
* removal and telling the VFS to evict the inode. So to finish, we
* just need to check whether any inodes couldn't be evicted.
*/
err2 = check_for_busy_inodes(sb, mk);
return err1 ?: err2;
}
/*
* Try to remove an llcrypt master encryption key.
*
* LL_IOC_REMOVE_ENCRYPTION_KEY (all_users=false) removes the current user's
* claim to the key, then removes the key itself if no other users have claims.
* LL_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS (all_users=true) always removes the
* key itself.
*
* To "remove the key itself", first we wipe the actual master key secret, so
* that no more inodes can be unlocked with it. Then we try to evict all cached
* inodes that had been unlocked with the key.
*
* If all inodes were evicted, then we unlink the llcrypt_master_key from the
* keyring. Otherwise it remains in the keyring in the "incompletely removed"
* state (without the actual secret key) where it tracks the list of remaining
* inodes. Userspace can execute the ioctl again later to retry eviction, or
* alternatively can re-add the secret key again.
*
* For more details, see the "Removing keys" section of
* Documentation/filesystems/llcrypt.rst.
*/
static int do_remove_key(struct file *filp, void __user *_uarg, bool all_users)
{
struct super_block *sb = file_inode(filp)->i_sb;
struct llcrypt_remove_key_arg __user *uarg = _uarg;
struct llcrypt_remove_key_arg arg;
struct key *key;
struct llcrypt_master_key *mk;
u32 status_flags = 0;
int err;
bool dead;
if (copy_from_user(&arg, uarg, sizeof(arg)))
return -EFAULT;
if (!valid_key_spec(&arg.key_spec))
return -EINVAL;
if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
return -EINVAL;
/*
* Only root can add and remove keys that are identified by an arbitrary
* descriptor rather than by a cryptographic hash.
*/
if (arg.key_spec.type == LLCRYPT_KEY_SPEC_TYPE_DESCRIPTOR &&
!capable(CAP_SYS_ADMIN))
return -EACCES;
/* Find the key being removed. */
key = llcrypt_find_master_key(sb, &arg.key_spec);
if (IS_ERR(key))
return PTR_ERR(key);
mk = key->payload.data[0];
down_write(&key->sem);
/* If relevant, remove current user's (or all users) claim to the key */
if (mk->mk_users && mk->mk_users->keys.nr_leaves_on_tree != 0) {
if (all_users)
err = keyring_clear(mk->mk_users);
else
err = remove_master_key_user(mk);
if (err) {
up_write(&key->sem);
goto out_put_key;
}
if (mk->mk_users->keys.nr_leaves_on_tree != 0) {
/*
* Other users have still added the key too. We removed
* the current user's claim to the key, but we still
* can't remove the key itself.
*/
status_flags |=
LLCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS;
err = 0;
up_write(&key->sem);
goto out_put_key;
}
}
/* No user claims remaining. Go ahead and wipe the secret. */
dead = false;
if (is_master_key_secret_present(&mk->mk_secret)) {
down_write(&mk->mk_secret_sem);
wipe_master_key_secret(&mk->mk_secret);
dead = refcount_dec_and_test(&mk->mk_refcount);
up_write(&mk->mk_secret_sem);
}
up_write(&key->sem);
if (dead) {
/*
* No inodes reference the key, and we wiped the secret, so the
* key object is free to be removed from the keyring.
*/
key_invalidate(key);
err = 0;
} else {
/* Some inodes still reference this key; try to evict them. */
err = try_to_lock_encrypted_files(sb, mk);
if (err == -EBUSY) {
status_flags |=
LLCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY;
err = 0;
}
}
/*
* We return 0 if we successfully did something: removed a claim to the
* key, wiped the secret, or tried locking the files again. Users need
* to check the informational status flags if they care whether the key
* has been fully removed including all files locked.
*/
out_put_key:
key_put(key);
if (err == 0)
err = put_user(status_flags, &uarg->removal_status_flags);
return err;
}
int llcrypt_ioctl_remove_key(struct file *filp, void __user *uarg)
{
return do_remove_key(filp, uarg, false);
}
EXPORT_SYMBOL_GPL(llcrypt_ioctl_remove_key);
int llcrypt_ioctl_remove_key_all_users(struct file *filp, void __user *uarg)
{
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
return do_remove_key(filp, uarg, true);
}
EXPORT_SYMBOL_GPL(llcrypt_ioctl_remove_key_all_users);
/*
* Retrieve the status of an llcrypt master encryption key.
*
* We set ->status to indicate whether the key is absent, present, or
* incompletely removed. "Incompletely removed" means that the master key
* secret has been removed, but some files which had been unlocked with it are
* still in use. This field allows applications to easily determine the state
* of an encrypted directory without using a hack such as trying to open a
* regular file in it (which can confuse the "incompletely removed" state with
* absent or present).
*
* In addition, for v2 policy keys we allow applications to determine, via
* ->status_flags and ->user_count, whether the key has been added by the
* current user, by other users, or by both. Most applications should not need
* this, since ordinarily only one user should know a given key. However, if a
* secret key is shared by multiple users, applications may wish to add an
* already-present key to prevent other users from removing it. This ioctl can
* be used to check whether that really is the case before the work is done to
* add the key --- which might e.g. require prompting the user for a passphrase.
*
* For more details, see the "LL_IOC_GET_ENCRYPTION_KEY_STATUS" section of
* Documentation/filesystems/llcrypt.rst.
*/
int llcrypt_ioctl_get_key_status(struct file *filp, void __user *uarg)
{
struct super_block *sb = file_inode(filp)->i_sb;
struct llcrypt_get_key_status_arg arg;
struct key *key;
struct llcrypt_master_key *mk;
int err;
if (copy_from_user(&arg, uarg, sizeof(arg)))
return -EFAULT;
if (!valid_key_spec(&arg.key_spec))
return -EINVAL;
if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
return -EINVAL;
arg.status_flags = 0;
arg.user_count = 0;
memset(arg.__out_reserved, 0, sizeof(arg.__out_reserved));
key = llcrypt_find_master_key(sb, &arg.key_spec);
if (IS_ERR(key)) {
if (key != ERR_PTR(-ENOKEY))
return PTR_ERR(key);
arg.status = LLCRYPT_KEY_STATUS_ABSENT;
err = 0;
goto out;
}
mk = key->payload.data[0];
down_read(&key->sem);
if (!is_master_key_secret_present(&mk->mk_secret)) {
arg.status = LLCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED;
err = 0;
goto out_release_key;
}
arg.status = LLCRYPT_KEY_STATUS_PRESENT;
if (mk->mk_users) {
struct key *mk_user;
arg.user_count = mk->mk_users->keys.nr_leaves_on_tree;
mk_user = find_master_key_user(mk);
if (!IS_ERR(mk_user)) {
arg.status_flags |=
LLCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF;
key_put(mk_user);
} else if (mk_user != ERR_PTR(-ENOKEY)) {
err = PTR_ERR(mk_user);
goto out_release_key;
}
}
err = 0;
out_release_key:
up_read(&key->sem);
key_put(key);
out:
if (!err && copy_to_user(uarg, &arg, sizeof(arg)))
err = -EFAULT;
return err;
}
EXPORT_SYMBOL_GPL(llcrypt_ioctl_get_key_status);
int __init llcrypt_init_keyring(void)
{
int err;
err = register_key_type(&key_type_llcrypt);
if (err)
return err;
err = register_key_type(&key_type_llcrypt_user);
if (err)
goto err_unregister_llcrypt;
return 0;
err_unregister_llcrypt:
unregister_key_type(&key_type_llcrypt);
return err;
}
void __exit llcrypt_exit_keyring(void)
{
unregister_key_type(&key_type_llcrypt_user);
unregister_key_type(&key_type_llcrypt);
}
