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![Eric Biggers](/assets/img/avatar_default.png)
By looking up the master keys in a filesystem-level keyring rather than in the calling processes' key hierarchy, it becomes possible for a user to set an encryption policy which refers to some key they don't actually know, then encrypt their files using that key. Cryptographically this isn't much of a problem, but the semantics of this would be a bit weird. Thus, enforce that a v2 encryption policy can only be set if the user has previously added the key, or has capable(CAP_FOWNER). We tolerate that this problem will continue to exist for v1 encryption policies, however; there is no way around that. Reviewed-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Eric Biggers <ebiggers@google.com>
984 lines
29 KiB
C
984 lines
29 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Filesystem-level keyring for fscrypt
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*
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* Copyright 2019 Google LLC
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*/
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/*
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* This file implements management of fscrypt master keys in the
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* filesystem-level keyring, including the ioctls:
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*
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* - FS_IOC_ADD_ENCRYPTION_KEY
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* - FS_IOC_REMOVE_ENCRYPTION_KEY
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* - FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS
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* - FS_IOC_GET_ENCRYPTION_KEY_STATUS
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*
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* See the "User API" section of Documentation/filesystems/fscrypt.rst for more
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* information about these ioctls.
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*/
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#include <crypto/skcipher.h>
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#include <linux/key-type.h>
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#include <linux/seq_file.h>
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#include "fscrypt_private.h"
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static void wipe_master_key_secret(struct fscrypt_master_key_secret *secret)
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{
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fscrypt_destroy_hkdf(&secret->hkdf);
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memzero_explicit(secret, sizeof(*secret));
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}
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static void move_master_key_secret(struct fscrypt_master_key_secret *dst,
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struct fscrypt_master_key_secret *src)
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{
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memcpy(dst, src, sizeof(*dst));
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memzero_explicit(src, sizeof(*src));
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}
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static void free_master_key(struct fscrypt_master_key *mk)
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{
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size_t i;
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wipe_master_key_secret(&mk->mk_secret);
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for (i = 0; i < ARRAY_SIZE(mk->mk_mode_keys); i++)
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crypto_free_skcipher(mk->mk_mode_keys[i]);
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key_put(mk->mk_users);
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kzfree(mk);
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}
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static inline bool valid_key_spec(const struct fscrypt_key_specifier *spec)
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{
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if (spec->__reserved)
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return false;
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return master_key_spec_len(spec) != 0;
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}
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static int fscrypt_key_instantiate(struct key *key,
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struct key_preparsed_payload *prep)
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{
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key->payload.data[0] = (struct fscrypt_master_key *)prep->data;
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return 0;
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}
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static void fscrypt_key_destroy(struct key *key)
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{
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free_master_key(key->payload.data[0]);
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}
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static void fscrypt_key_describe(const struct key *key, struct seq_file *m)
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{
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seq_puts(m, key->description);
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if (key_is_positive(key)) {
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const struct fscrypt_master_key *mk = key->payload.data[0];
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if (!is_master_key_secret_present(&mk->mk_secret))
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seq_puts(m, ": secret removed");
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}
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}
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/*
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* Type of key in ->s_master_keys. Each key of this type represents a master
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* key which has been added to the filesystem. Its payload is a
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* 'struct fscrypt_master_key'. The "." prefix in the key type name prevents
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* users from adding keys of this type via the keyrings syscalls rather than via
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* the intended method of FS_IOC_ADD_ENCRYPTION_KEY.
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*/
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static struct key_type key_type_fscrypt = {
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.name = "._fscrypt",
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.instantiate = fscrypt_key_instantiate,
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.destroy = fscrypt_key_destroy,
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.describe = fscrypt_key_describe,
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};
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static int fscrypt_user_key_instantiate(struct key *key,
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struct key_preparsed_payload *prep)
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{
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/*
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* We just charge FSCRYPT_MAX_KEY_SIZE bytes to the user's key quota for
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* each key, regardless of the exact key size. The amount of memory
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* actually used is greater than the size of the raw key anyway.
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*/
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return key_payload_reserve(key, FSCRYPT_MAX_KEY_SIZE);
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}
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static void fscrypt_user_key_describe(const struct key *key, struct seq_file *m)
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{
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seq_puts(m, key->description);
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}
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/*
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* Type of key in ->mk_users. Each key of this type represents a particular
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* user who has added a particular master key.
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*
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* Note that the name of this key type really should be something like
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* ".fscrypt-user" instead of simply ".fscrypt". But the shorter name is chosen
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* mainly for simplicity of presentation in /proc/keys when read by a non-root
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* user. And it is expected to be rare that a key is actually added by multiple
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* users, since users should keep their encryption keys confidential.
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*/
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static struct key_type key_type_fscrypt_user = {
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.name = ".fscrypt",
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.instantiate = fscrypt_user_key_instantiate,
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.describe = fscrypt_user_key_describe,
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};
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/* Search ->s_master_keys or ->mk_users */
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static struct key *search_fscrypt_keyring(struct key *keyring,
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struct key_type *type,
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const char *description)
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{
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/*
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* We need to mark the keyring reference as "possessed" so that we
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* acquire permission to search it, via the KEY_POS_SEARCH permission.
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*/
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key_ref_t keyref = make_key_ref(keyring, true /* possessed */);
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keyref = keyring_search(keyref, type, description, false);
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if (IS_ERR(keyref)) {
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if (PTR_ERR(keyref) == -EAGAIN || /* not found */
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PTR_ERR(keyref) == -EKEYREVOKED) /* recently invalidated */
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keyref = ERR_PTR(-ENOKEY);
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return ERR_CAST(keyref);
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}
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return key_ref_to_ptr(keyref);
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}
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#define FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE \
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(CONST_STRLEN("fscrypt-") + FIELD_SIZEOF(struct super_block, s_id))
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#define FSCRYPT_MK_DESCRIPTION_SIZE (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + 1)
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#define FSCRYPT_MK_USERS_DESCRIPTION_SIZE \
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(CONST_STRLEN("fscrypt-") + 2 * FSCRYPT_KEY_IDENTIFIER_SIZE + \
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CONST_STRLEN("-users") + 1)
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#define FSCRYPT_MK_USER_DESCRIPTION_SIZE \
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(2 * FSCRYPT_KEY_IDENTIFIER_SIZE + CONST_STRLEN(".uid.") + 10 + 1)
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static void format_fs_keyring_description(
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char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE],
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const struct super_block *sb)
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{
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sprintf(description, "fscrypt-%s", sb->s_id);
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}
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static void format_mk_description(
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char description[FSCRYPT_MK_DESCRIPTION_SIZE],
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const struct fscrypt_key_specifier *mk_spec)
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{
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sprintf(description, "%*phN",
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master_key_spec_len(mk_spec), (u8 *)&mk_spec->u);
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}
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static void format_mk_users_keyring_description(
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char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE],
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const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
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{
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sprintf(description, "fscrypt-%*phN-users",
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FSCRYPT_KEY_IDENTIFIER_SIZE, mk_identifier);
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}
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static void format_mk_user_description(
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char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE],
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const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
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{
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sprintf(description, "%*phN.uid.%u", FSCRYPT_KEY_IDENTIFIER_SIZE,
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mk_identifier, __kuid_val(current_fsuid()));
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}
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/* Create ->s_master_keys if needed. Synchronized by fscrypt_add_key_mutex. */
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static int allocate_filesystem_keyring(struct super_block *sb)
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{
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char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE];
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struct key *keyring;
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if (sb->s_master_keys)
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return 0;
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format_fs_keyring_description(description, sb);
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keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
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current_cred(), KEY_POS_SEARCH |
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KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW,
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KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
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if (IS_ERR(keyring))
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return PTR_ERR(keyring);
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/* Pairs with READ_ONCE() in fscrypt_find_master_key() */
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smp_store_release(&sb->s_master_keys, keyring);
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return 0;
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}
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void fscrypt_sb_free(struct super_block *sb)
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{
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key_put(sb->s_master_keys);
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sb->s_master_keys = NULL;
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}
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/*
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* Find the specified master key in ->s_master_keys.
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* Returns ERR_PTR(-ENOKEY) if not found.
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*/
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struct key *fscrypt_find_master_key(struct super_block *sb,
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const struct fscrypt_key_specifier *mk_spec)
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{
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struct key *keyring;
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char description[FSCRYPT_MK_DESCRIPTION_SIZE];
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/* pairs with smp_store_release() in allocate_filesystem_keyring() */
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keyring = READ_ONCE(sb->s_master_keys);
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if (keyring == NULL)
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return ERR_PTR(-ENOKEY); /* No keyring yet, so no keys yet. */
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format_mk_description(description, mk_spec);
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return search_fscrypt_keyring(keyring, &key_type_fscrypt, description);
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}
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static int allocate_master_key_users_keyring(struct fscrypt_master_key *mk)
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{
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char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE];
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struct key *keyring;
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format_mk_users_keyring_description(description,
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mk->mk_spec.u.identifier);
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keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
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current_cred(), KEY_POS_SEARCH |
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KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW,
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KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
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if (IS_ERR(keyring))
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return PTR_ERR(keyring);
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mk->mk_users = keyring;
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return 0;
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}
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/*
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* Find the current user's "key" in the master key's ->mk_users.
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* Returns ERR_PTR(-ENOKEY) if not found.
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*/
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static struct key *find_master_key_user(struct fscrypt_master_key *mk)
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{
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char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE];
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format_mk_user_description(description, mk->mk_spec.u.identifier);
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return search_fscrypt_keyring(mk->mk_users, &key_type_fscrypt_user,
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description);
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}
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/*
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* Give the current user a "key" in ->mk_users. This charges the user's quota
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* and marks the master key as added by the current user, so that it cannot be
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* removed by another user with the key. Either the master key's key->sem must
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* be held for write, or the master key must be still undergoing initialization.
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*/
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static int add_master_key_user(struct fscrypt_master_key *mk)
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{
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char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE];
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struct key *mk_user;
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int err;
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format_mk_user_description(description, mk->mk_spec.u.identifier);
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mk_user = key_alloc(&key_type_fscrypt_user, description,
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current_fsuid(), current_gid(), current_cred(),
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KEY_POS_SEARCH | KEY_USR_VIEW, 0, NULL);
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if (IS_ERR(mk_user))
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return PTR_ERR(mk_user);
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err = key_instantiate_and_link(mk_user, NULL, 0, mk->mk_users, NULL);
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key_put(mk_user);
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return err;
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}
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/*
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* Remove the current user's "key" from ->mk_users.
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* The master key's key->sem must be held for write.
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*
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* Returns 0 if removed, -ENOKEY if not found, or another -errno code.
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*/
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static int remove_master_key_user(struct fscrypt_master_key *mk)
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{
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struct key *mk_user;
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int err;
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mk_user = find_master_key_user(mk);
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if (IS_ERR(mk_user))
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return PTR_ERR(mk_user);
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err = key_unlink(mk->mk_users, mk_user);
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key_put(mk_user);
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return err;
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}
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/*
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* Allocate a new fscrypt_master_key which contains the given secret, set it as
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* the payload of a new 'struct key' of type fscrypt, and link the 'struct key'
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* into the given keyring. Synchronized by fscrypt_add_key_mutex.
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*/
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static int add_new_master_key(struct fscrypt_master_key_secret *secret,
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const struct fscrypt_key_specifier *mk_spec,
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struct key *keyring)
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{
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struct fscrypt_master_key *mk;
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char description[FSCRYPT_MK_DESCRIPTION_SIZE];
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struct key *key;
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int err;
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mk = kzalloc(sizeof(*mk), GFP_KERNEL);
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if (!mk)
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return -ENOMEM;
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mk->mk_spec = *mk_spec;
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move_master_key_secret(&mk->mk_secret, secret);
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init_rwsem(&mk->mk_secret_sem);
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refcount_set(&mk->mk_refcount, 1); /* secret is present */
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INIT_LIST_HEAD(&mk->mk_decrypted_inodes);
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spin_lock_init(&mk->mk_decrypted_inodes_lock);
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if (mk_spec->type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) {
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err = allocate_master_key_users_keyring(mk);
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if (err)
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goto out_free_mk;
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err = add_master_key_user(mk);
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if (err)
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goto out_free_mk;
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}
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/*
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* Note that we don't charge this key to anyone's quota, since when
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* ->mk_users is in use those keys are charged instead, and otherwise
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* (when ->mk_users isn't in use) only root can add these keys.
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*/
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format_mk_description(description, mk_spec);
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key = key_alloc(&key_type_fscrypt, description,
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GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
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KEY_POS_SEARCH | KEY_USR_SEARCH | KEY_USR_VIEW,
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KEY_ALLOC_NOT_IN_QUOTA, NULL);
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if (IS_ERR(key)) {
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err = PTR_ERR(key);
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goto out_free_mk;
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}
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err = key_instantiate_and_link(key, mk, sizeof(*mk), keyring, NULL);
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key_put(key);
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if (err)
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goto out_free_mk;
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return 0;
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out_free_mk:
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free_master_key(mk);
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return err;
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}
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#define KEY_DEAD 1
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static int add_existing_master_key(struct fscrypt_master_key *mk,
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struct fscrypt_master_key_secret *secret)
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{
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struct key *mk_user;
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bool rekey;
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int err;
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|
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/*
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* If the current user is already in ->mk_users, then there's nothing to
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* do. (Not applicable for v1 policy keys, which have NULL ->mk_users.)
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*/
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if (mk->mk_users) {
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mk_user = find_master_key_user(mk);
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if (mk_user != ERR_PTR(-ENOKEY)) {
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if (IS_ERR(mk_user))
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return PTR_ERR(mk_user);
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key_put(mk_user);
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return 0;
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}
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}
|
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|
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/* If we'll be re-adding ->mk_secret, try to take the reference. */
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rekey = !is_master_key_secret_present(&mk->mk_secret);
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if (rekey && !refcount_inc_not_zero(&mk->mk_refcount))
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return KEY_DEAD;
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|
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/* Add the current user to ->mk_users, if applicable. */
|
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if (mk->mk_users) {
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err = add_master_key_user(mk);
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if (err) {
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if (rekey && refcount_dec_and_test(&mk->mk_refcount))
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return KEY_DEAD;
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return err;
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}
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}
|
|
|
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/* Re-add the secret if needed. */
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if (rekey) {
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down_write(&mk->mk_secret_sem);
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move_master_key_secret(&mk->mk_secret, secret);
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up_write(&mk->mk_secret_sem);
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}
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return 0;
|
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}
|
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|
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static int add_master_key(struct super_block *sb,
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struct fscrypt_master_key_secret *secret,
|
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const struct fscrypt_key_specifier *mk_spec)
|
|
{
|
|
static DEFINE_MUTEX(fscrypt_add_key_mutex);
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|
struct key *key;
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|
int err;
|
|
|
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mutex_lock(&fscrypt_add_key_mutex); /* serialize find + link */
|
|
retry:
|
|
key = fscrypt_find_master_key(sb, mk_spec);
|
|
if (IS_ERR(key)) {
|
|
err = PTR_ERR(key);
|
|
if (err != -ENOKEY)
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|
goto out_unlock;
|
|
/* Didn't find the key in ->s_master_keys. Add it. */
|
|
err = allocate_filesystem_keyring(sb);
|
|
if (err)
|
|
goto out_unlock;
|
|
err = add_new_master_key(secret, mk_spec, sb->s_master_keys);
|
|
} else {
|
|
/*
|
|
* Found the key in ->s_master_keys. Re-add the secret if
|
|
* needed, and add the user to ->mk_users if needed.
|
|
*/
|
|
down_write(&key->sem);
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|
err = add_existing_master_key(key->payload.data[0], secret);
|
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up_write(&key->sem);
|
|
if (err == KEY_DEAD) {
|
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/* Key being removed or needs to be removed */
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|
key_invalidate(key);
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|
key_put(key);
|
|
goto retry;
|
|
}
|
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key_put(key);
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|
}
|
|
out_unlock:
|
|
mutex_unlock(&fscrypt_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 "FS_IOC_ADD_ENCRYPTION_KEY" section of
|
|
* Documentation/filesystems/fscrypt.rst.
|
|
*/
|
|
int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
|
|
{
|
|
struct super_block *sb = file_inode(filp)->i_sb;
|
|
struct fscrypt_add_key_arg __user *uarg = _uarg;
|
|
struct fscrypt_add_key_arg arg;
|
|
struct fscrypt_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 < FSCRYPT_MIN_KEY_SIZE ||
|
|
arg.raw_size > FSCRYPT_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 FSCRYPT_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 FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
|
|
err = fscrypt_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 = fscrypt_hkdf_expand(&secret.hkdf,
|
|
HKDF_CONTEXT_KEY_IDENTIFIER,
|
|
NULL, 0, arg.key_spec.u.identifier,
|
|
FSCRYPT_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,
|
|
FSCRYPT_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(fscrypt_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 fscrypt_verify_key_added(struct super_block *sb,
|
|
const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
|
|
{
|
|
struct fscrypt_key_specifier mk_spec;
|
|
struct key *key, *mk_user;
|
|
struct fscrypt_master_key *mk;
|
|
int err;
|
|
|
|
mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
|
|
memcpy(mk_spec.u.identifier, identifier, FSCRYPT_KEY_IDENTIFIER_SIZE);
|
|
|
|
key = fscrypt_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 fscrypt_master_key *mk)
|
|
{
|
|
struct fscrypt_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;
|
|
spin_lock(&inode->i_lock);
|
|
if (inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW)) {
|
|
spin_unlock(&inode->i_lock);
|
|
continue;
|
|
}
|
|
__iget(inode);
|
|
spin_unlock(&inode->i_lock);
|
|
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 fscrypt_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 fscrypt_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(dentry, _path, sizeof(_path));
|
|
dput(dentry);
|
|
}
|
|
if (IS_ERR_OR_NULL(path))
|
|
path = "(unknown)";
|
|
|
|
fscrypt_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 fscrypt_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 fscrypt_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 fscrypt master encryption key.
|
|
*
|
|
* FS_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.
|
|
* FS_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 fscrypt_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/fscrypt.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 fscrypt_remove_key_arg __user *uarg = _uarg;
|
|
struct fscrypt_remove_key_arg arg;
|
|
struct key *key;
|
|
struct fscrypt_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 == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR &&
|
|
!capable(CAP_SYS_ADMIN))
|
|
return -EACCES;
|
|
|
|
/* Find the key being removed. */
|
|
key = fscrypt_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 |=
|
|
FSCRYPT_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 |=
|
|
FSCRYPT_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 fscrypt_ioctl_remove_key(struct file *filp, void __user *uarg)
|
|
{
|
|
return do_remove_key(filp, uarg, false);
|
|
}
|
|
EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key);
|
|
|
|
int fscrypt_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(fscrypt_ioctl_remove_key_all_users);
|
|
|
|
/*
|
|
* Retrieve the status of an fscrypt 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 "FS_IOC_GET_ENCRYPTION_KEY_STATUS" section of
|
|
* Documentation/filesystems/fscrypt.rst.
|
|
*/
|
|
int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg)
|
|
{
|
|
struct super_block *sb = file_inode(filp)->i_sb;
|
|
struct fscrypt_get_key_status_arg arg;
|
|
struct key *key;
|
|
struct fscrypt_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 = fscrypt_find_master_key(sb, &arg.key_spec);
|
|
if (IS_ERR(key)) {
|
|
if (key != ERR_PTR(-ENOKEY))
|
|
return PTR_ERR(key);
|
|
arg.status = FSCRYPT_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 = FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED;
|
|
err = 0;
|
|
goto out_release_key;
|
|
}
|
|
|
|
arg.status = FSCRYPT_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 |=
|
|
FSCRYPT_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(fscrypt_ioctl_get_key_status);
|
|
|
|
int __init fscrypt_init_keyring(void)
|
|
{
|
|
int err;
|
|
|
|
err = register_key_type(&key_type_fscrypt);
|
|
if (err)
|
|
return err;
|
|
|
|
err = register_key_type(&key_type_fscrypt_user);
|
|
if (err)
|
|
goto err_unregister_fscrypt;
|
|
|
|
return 0;
|
|
|
|
err_unregister_fscrypt:
|
|
unregister_key_type(&key_type_fscrypt);
|
|
return err;
|
|
}
|