forked from Minki/linux
e3b1078bed
The eMMC inline crypto standard will only specify 32 DUN bits (a.k.a. IV bits), unlike UFS's 64. IV_INO_LBLK_64 is therefore not applicable, but an encryption format which uses one key per policy and permits the moving of encrypted file contents (as f2fs's garbage collector requires) is still desirable. To support such hardware, add a new encryption format IV_INO_LBLK_32 that makes the best use of the 32 bits: the IV is set to 'SipHash-2-4(inode_number) + file_logical_block_number mod 2^32', where the SipHash key is derived from the fscrypt master key. We hash only the inode number and not also the block number, because we need to maintain contiguity of DUNs to merge bios. Unlike with IV_INO_LBLK_64, with this format IV reuse is possible; this is unavoidable given the size of the DUN. This means this format should only be used where the requirements of the first paragraph apply. However, the hash spreads out the IVs in the whole usable range, and the use of a keyed hash makes it difficult for an attacker to determine which files use which IVs. Besides the above differences, this flag works like IV_INO_LBLK_64 in that on ext4 it is only allowed if the stable_inodes feature has been enabled to prevent inode numbers and the filesystem UUID from changing. Link: https://lore.kernel.org/r/20200515204141.251098-1-ebiggers@kernel.org Reviewed-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Paul Crowley <paulcrowley@google.com> Signed-off-by: Eric Biggers <ebiggers@google.com>
1124 lines
33 KiB
C
1124 lines
33 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/random.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 <= __FSCRYPT_MODE_MAX; i++) {
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crypto_free_skcipher(mk->mk_direct_keys[i]);
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crypto_free_skcipher(mk->mk_iv_ino_lblk_64_keys[i]);
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crypto_free_skcipher(mk->mk_iv_ino_lblk_32_keys[i]);
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}
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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-") + sizeof_field(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);
|
|
if (err) {
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if (rekey && refcount_dec_and_test(&mk->mk_refcount))
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return KEY_DEAD;
|
|
return err;
|
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}
|
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}
|
|
|
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/* Re-add the secret if needed. */
|
|
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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}
|
|
|
|
static int do_add_master_key(struct super_block *sb,
|
|
struct fscrypt_master_key_secret *secret,
|
|
const struct fscrypt_key_specifier *mk_spec)
|
|
{
|
|
static DEFINE_MUTEX(fscrypt_add_key_mutex);
|
|
struct key *key;
|
|
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)) {
|
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err = PTR_ERR(key);
|
|
if (err != -ENOKEY)
|
|
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);
|
|
err = add_existing_master_key(key->payload.data[0], secret);
|
|
up_write(&key->sem);
|
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if (err == KEY_DEAD) {
|
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/* Key being removed or needs to be removed */
|
|
key_invalidate(key);
|
|
key_put(key);
|
|
goto retry;
|
|
}
|
|
key_put(key);
|
|
}
|
|
out_unlock:
|
|
mutex_unlock(&fscrypt_add_key_mutex);
|
|
return err;
|
|
}
|
|
|
|
static int add_master_key(struct super_block *sb,
|
|
struct fscrypt_master_key_secret *secret,
|
|
struct fscrypt_key_specifier *key_spec)
|
|
{
|
|
int err;
|
|
|
|
if (key_spec->type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) {
|
|
err = fscrypt_init_hkdf(&secret->hkdf, secret->raw,
|
|
secret->size);
|
|
if (err)
|
|
return err;
|
|
|
|
/*
|
|
* Now that the HKDF context is initialized, the raw key is no
|
|
* longer needed.
|
|
*/
|
|
memzero_explicit(secret->raw, secret->size);
|
|
|
|
/* Calculate the key identifier */
|
|
err = fscrypt_hkdf_expand(&secret->hkdf,
|
|
HKDF_CONTEXT_KEY_IDENTIFIER, NULL, 0,
|
|
key_spec->u.identifier,
|
|
FSCRYPT_KEY_IDENTIFIER_SIZE);
|
|
if (err)
|
|
return err;
|
|
}
|
|
return do_add_master_key(sb, secret, key_spec);
|
|
}
|
|
|
|
static int fscrypt_provisioning_key_preparse(struct key_preparsed_payload *prep)
|
|
{
|
|
const struct fscrypt_provisioning_key_payload *payload = prep->data;
|
|
|
|
if (prep->datalen < sizeof(*payload) + FSCRYPT_MIN_KEY_SIZE ||
|
|
prep->datalen > sizeof(*payload) + FSCRYPT_MAX_KEY_SIZE)
|
|
return -EINVAL;
|
|
|
|
if (payload->type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR &&
|
|
payload->type != FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER)
|
|
return -EINVAL;
|
|
|
|
if (payload->__reserved)
|
|
return -EINVAL;
|
|
|
|
prep->payload.data[0] = kmemdup(payload, prep->datalen, GFP_KERNEL);
|
|
if (!prep->payload.data[0])
|
|
return -ENOMEM;
|
|
|
|
prep->quotalen = prep->datalen;
|
|
return 0;
|
|
}
|
|
|
|
static void fscrypt_provisioning_key_free_preparse(
|
|
struct key_preparsed_payload *prep)
|
|
{
|
|
kzfree(prep->payload.data[0]);
|
|
}
|
|
|
|
static void fscrypt_provisioning_key_describe(const struct key *key,
|
|
struct seq_file *m)
|
|
{
|
|
seq_puts(m, key->description);
|
|
if (key_is_positive(key)) {
|
|
const struct fscrypt_provisioning_key_payload *payload =
|
|
key->payload.data[0];
|
|
|
|
seq_printf(m, ": %u [%u]", key->datalen, payload->type);
|
|
}
|
|
}
|
|
|
|
static void fscrypt_provisioning_key_destroy(struct key *key)
|
|
{
|
|
kzfree(key->payload.data[0]);
|
|
}
|
|
|
|
static struct key_type key_type_fscrypt_provisioning = {
|
|
.name = "fscrypt-provisioning",
|
|
.preparse = fscrypt_provisioning_key_preparse,
|
|
.free_preparse = fscrypt_provisioning_key_free_preparse,
|
|
.instantiate = generic_key_instantiate,
|
|
.describe = fscrypt_provisioning_key_describe,
|
|
.destroy = fscrypt_provisioning_key_destroy,
|
|
};
|
|
|
|
/*
|
|
* Retrieve the raw key from the Linux keyring key specified by 'key_id', and
|
|
* store it into 'secret'.
|
|
*
|
|
* The key must be of type "fscrypt-provisioning" and must have the field
|
|
* fscrypt_provisioning_key_payload::type set to 'type', indicating that it's
|
|
* only usable with fscrypt with the particular KDF version identified by
|
|
* 'type'. We don't use the "logon" key type because there's no way to
|
|
* completely restrict the use of such keys; they can be used by any kernel API
|
|
* that accepts "logon" keys and doesn't require a specific service prefix.
|
|
*
|
|
* The ability to specify the key via Linux keyring key is intended for cases
|
|
* where userspace needs to re-add keys after the filesystem is unmounted and
|
|
* re-mounted. Most users should just provide the raw key directly instead.
|
|
*/
|
|
static int get_keyring_key(u32 key_id, u32 type,
|
|
struct fscrypt_master_key_secret *secret)
|
|
{
|
|
key_ref_t ref;
|
|
struct key *key;
|
|
const struct fscrypt_provisioning_key_payload *payload;
|
|
int err;
|
|
|
|
ref = lookup_user_key(key_id, 0, KEY_NEED_SEARCH);
|
|
if (IS_ERR(ref))
|
|
return PTR_ERR(ref);
|
|
key = key_ref_to_ptr(ref);
|
|
|
|
if (key->type != &key_type_fscrypt_provisioning)
|
|
goto bad_key;
|
|
payload = key->payload.data[0];
|
|
|
|
/* Don't allow fscrypt v1 keys to be used as v2 keys and vice versa. */
|
|
if (payload->type != type)
|
|
goto bad_key;
|
|
|
|
secret->size = key->datalen - sizeof(*payload);
|
|
memcpy(secret->raw, payload->raw, secret->size);
|
|
err = 0;
|
|
goto out_put;
|
|
|
|
bad_key:
|
|
err = -EKEYREJECTED;
|
|
out_put:
|
|
key_ref_put(ref);
|
|
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 (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
|
|
return -EINVAL;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR &&
|
|
!capable(CAP_SYS_ADMIN))
|
|
return -EACCES;
|
|
|
|
memset(&secret, 0, sizeof(secret));
|
|
if (arg.key_id) {
|
|
if (arg.raw_size != 0)
|
|
return -EINVAL;
|
|
err = get_keyring_key(arg.key_id, arg.key_spec.type, &secret);
|
|
if (err)
|
|
goto out_wipe_secret;
|
|
} else {
|
|
if (arg.raw_size < FSCRYPT_MIN_KEY_SIZE ||
|
|
arg.raw_size > FSCRYPT_MAX_KEY_SIZE)
|
|
return -EINVAL;
|
|
secret.size = arg.raw_size;
|
|
err = -EFAULT;
|
|
if (copy_from_user(secret.raw, uarg->raw, secret.size))
|
|
goto out_wipe_secret;
|
|
}
|
|
|
|
err = add_master_key(sb, &secret, &arg.key_spec);
|
|
if (err)
|
|
goto out_wipe_secret;
|
|
|
|
/* Return the key identifier to userspace, if applicable */
|
|
err = -EFAULT;
|
|
if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER &&
|
|
copy_to_user(uarg->key_spec.u.identifier, arg.key_spec.u.identifier,
|
|
FSCRYPT_KEY_IDENTIFIER_SIZE))
|
|
goto out_wipe_secret;
|
|
err = 0;
|
|
out_wipe_secret:
|
|
wipe_master_key_secret(&secret);
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key);
|
|
|
|
/*
|
|
* Add the key for '-o test_dummy_encryption' to the filesystem keyring.
|
|
*
|
|
* Use a per-boot random key to prevent people from misusing this option.
|
|
*/
|
|
int fscrypt_add_test_dummy_key(struct super_block *sb,
|
|
struct fscrypt_key_specifier *key_spec)
|
|
{
|
|
static u8 test_key[FSCRYPT_MAX_KEY_SIZE];
|
|
struct fscrypt_master_key_secret secret;
|
|
int err;
|
|
|
|
get_random_once(test_key, FSCRYPT_MAX_KEY_SIZE);
|
|
|
|
memset(&secret, 0, sizeof(secret));
|
|
secret.size = FSCRYPT_MAX_KEY_SIZE;
|
|
memcpy(secret.raw, test_key, FSCRYPT_MAX_KEY_SIZE);
|
|
|
|
err = add_master_key(sb, &secret, key_spec);
|
|
wipe_master_key_secret(&secret);
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
|
|
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;
|
|
}
|
|
spin_unlock(&mk->mk_decrypted_inodes_lock);
|
|
|
|
fscrypt_warn(NULL,
|
|
"%s: %zu inode(s) still busy after removing key with %s %*phN, including ino %lu",
|
|
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);
|
|
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;
|
|
|
|
err = register_key_type(&key_type_fscrypt_provisioning);
|
|
if (err)
|
|
goto err_unregister_fscrypt_user;
|
|
|
|
return 0;
|
|
|
|
err_unregister_fscrypt_user:
|
|
unregister_key_type(&key_type_fscrypt_user);
|
|
err_unregister_fscrypt:
|
|
unregister_key_type(&key_type_fscrypt);
|
|
return err;
|
|
}
|