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1131 lines
33 KiB
1131 lines
33 KiB
// 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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|
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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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|
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#include "fscrypt_private.h" |
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|
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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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fscrypt_destroy_prepared_key(&mk->mk_direct_keys[i]); |
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fscrypt_destroy_prepared_key(&mk->mk_iv_ino_lblk_64_keys[i]); |
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fscrypt_destroy_prepared_key(&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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kfree_sensitive(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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|
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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 |
|
* ".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( |
|
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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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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sprintf(description, "%*phN.uid.%u", FSCRYPT_KEY_IDENTIFIER_SIZE, |
|
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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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 the smp_load_acquire() in fscrypt_find_master_key(). |
|
* I.e., here we publish ->s_master_keys with a RELEASE barrier so that |
|
* concurrent tasks can ACQUIRE it. |
|
*/ |
|
smp_store_release(&sb->s_master_keys, keyring); |
|
return 0; |
|
} |
|
|
|
void fscrypt_sb_free(struct super_block *sb) |
|
{ |
|
key_put(sb->s_master_keys); |
|
sb->s_master_keys = NULL; |
|
} |
|
|
|
/* |
|
* Find the specified master key in ->s_master_keys. |
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* Returns ERR_PTR(-ENOKEY) if not found. |
|
*/ |
|
struct key *fscrypt_find_master_key(struct super_block *sb, |
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const struct fscrypt_key_specifier *mk_spec) |
|
{ |
|
struct key *keyring; |
|
char description[FSCRYPT_MK_DESCRIPTION_SIZE]; |
|
|
|
/* |
|
* Pairs with the smp_store_release() in allocate_filesystem_keyring(). |
|
* I.e., another task can publish ->s_master_keys concurrently, |
|
* executing a RELEASE barrier. We need to use smp_load_acquire() here |
|
* to safely ACQUIRE the memory the other task published. |
|
*/ |
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keyring = smp_load_acquire(&sb->s_master_keys); |
|
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); |
|
} |
|
|
|
static int allocate_master_key_users_keyring(struct fscrypt_master_key *mk) |
|
{ |
|
char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE]; |
|
struct key *keyring; |
|
|
|
format_mk_users_keyring_description(description, |
|
mk->mk_spec.u.identifier); |
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keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, |
|
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); |
|
if (IS_ERR(keyring)) |
|
return PTR_ERR(keyring); |
|
|
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mk->mk_users = keyring; |
|
return 0; |
|
} |
|
|
|
/* |
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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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static struct key *find_master_key_user(struct fscrypt_master_key *mk) |
|
{ |
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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, |
|
description); |
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} |
|
|
|
/* |
|
* Give the current user a "key" in ->mk_users. This charges the user's quota |
|
* and marks the master key as added by the current user, so that it cannot be |
|
* removed by another user with the key. Either the master key's key->sem must |
|
* be held for write, or the master key must be still undergoing initialization. |
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*/ |
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static int add_master_key_user(struct fscrypt_master_key *mk) |
|
{ |
|
char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE]; |
|
struct key *mk_user; |
|
int err; |
|
|
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format_mk_user_description(description, mk->mk_spec.u.identifier); |
|
mk_user = key_alloc(&key_type_fscrypt_user, description, |
|
current_fsuid(), current_gid(), current_cred(), |
|
KEY_POS_SEARCH | KEY_USR_VIEW, 0, NULL); |
|
if (IS_ERR(mk_user)) |
|
return PTR_ERR(mk_user); |
|
|
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err = key_instantiate_and_link(mk_user, NULL, 0, mk->mk_users, NULL); |
|
key_put(mk_user); |
|
return err; |
|
} |
|
|
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/* |
|
* Remove the current user's "key" from ->mk_users. |
|
* The master key's key->sem must be held for write. |
|
* |
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* Returns 0 if removed, -ENOKEY if not found, or another -errno code. |
|
*/ |
|
static int remove_master_key_user(struct fscrypt_master_key *mk) |
|
{ |
|
struct key *mk_user; |
|
int err; |
|
|
|
mk_user = find_master_key_user(mk); |
|
if (IS_ERR(mk_user)) |
|
return PTR_ERR(mk_user); |
|
err = key_unlink(mk->mk_users, mk_user); |
|
key_put(mk_user); |
|
return err; |
|
} |
|
|
|
/* |
|
* Allocate a new fscrypt_master_key which contains the given secret, set it as |
|
* the payload of a new 'struct key' of type fscrypt, and link the 'struct key' |
|
* into the given keyring. Synchronized by fscrypt_add_key_mutex. |
|
*/ |
|
static int add_new_master_key(struct fscrypt_master_key_secret *secret, |
|
const struct fscrypt_key_specifier *mk_spec, |
|
struct key *keyring) |
|
{ |
|
struct fscrypt_master_key *mk; |
|
char description[FSCRYPT_MK_DESCRIPTION_SIZE]; |
|
struct key *key; |
|
int err; |
|
|
|
mk = kzalloc(sizeof(*mk), GFP_KERNEL); |
|
if (!mk) |
|
return -ENOMEM; |
|
|
|
mk->mk_spec = *mk_spec; |
|
|
|
move_master_key_secret(&mk->mk_secret, secret); |
|
|
|
refcount_set(&mk->mk_refcount, 1); /* secret is present */ |
|
INIT_LIST_HEAD(&mk->mk_decrypted_inodes); |
|
spin_lock_init(&mk->mk_decrypted_inodes_lock); |
|
|
|
if (mk_spec->type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) { |
|
err = allocate_master_key_users_keyring(mk); |
|
if (err) |
|
goto out_free_mk; |
|
err = add_master_key_user(mk); |
|
if (err) |
|
goto out_free_mk; |
|
} |
|
|
|
/* |
|
* Note that we don't charge this key to anyone's quota, since when |
|
* ->mk_users is in use those keys are charged instead, and otherwise |
|
* (when ->mk_users isn't in use) only root can add these keys. |
|
*/ |
|
format_mk_description(description, mk_spec); |
|
key = key_alloc(&key_type_fscrypt, description, |
|
GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(), |
|
KEY_POS_SEARCH | KEY_USR_SEARCH | KEY_USR_VIEW, |
|
KEY_ALLOC_NOT_IN_QUOTA, NULL); |
|
if (IS_ERR(key)) { |
|
err = PTR_ERR(key); |
|
goto out_free_mk; |
|
} |
|
err = key_instantiate_and_link(key, mk, sizeof(*mk), keyring, NULL); |
|
key_put(key); |
|
if (err) |
|
goto out_free_mk; |
|
|
|
return 0; |
|
|
|
out_free_mk: |
|
free_master_key(mk); |
|
return err; |
|
} |
|
|
|
#define KEY_DEAD 1 |
|
|
|
static int add_existing_master_key(struct fscrypt_master_key *mk, |
|
struct fscrypt_master_key_secret *secret) |
|
{ |
|
struct key *mk_user; |
|
bool rekey; |
|
int err; |
|
|
|
/* |
|
* If the current user is already in ->mk_users, then there's nothing to |
|
* do. (Not applicable for v1 policy keys, which have NULL ->mk_users.) |
|
*/ |
|
if (mk->mk_users) { |
|
mk_user = find_master_key_user(mk); |
|
if (mk_user != ERR_PTR(-ENOKEY)) { |
|
if (IS_ERR(mk_user)) |
|
return PTR_ERR(mk_user); |
|
key_put(mk_user); |
|
return 0; |
|
} |
|
} |
|
|
|
/* If we'll be re-adding ->mk_secret, try to take the reference. */ |
|
rekey = !is_master_key_secret_present(&mk->mk_secret); |
|
if (rekey && !refcount_inc_not_zero(&mk->mk_refcount)) |
|
return KEY_DEAD; |
|
|
|
/* Add the current user to ->mk_users, if applicable. */ |
|
if (mk->mk_users) { |
|
err = add_master_key_user(mk); |
|
if (err) { |
|
if (rekey && refcount_dec_and_test(&mk->mk_refcount)) |
|
return KEY_DEAD; |
|
return err; |
|
} |
|
} |
|
|
|
/* Re-add the secret if needed. */ |
|
if (rekey) |
|
move_master_key_secret(&mk->mk_secret, secret); |
|
return 0; |
|
} |
|
|
|
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; |
|
|
|
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) |
|
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); |
|
if (err == KEY_DEAD) { |
|
/* Key being removed or needs to be removed */ |
|
key_invalidate(key); |
|
key_put(key); |
|
goto retry; |
|
} |
|
key_put(key); |
|
} |
|
out_unlock: |
|
mutex_unlock(&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) |
|
{ |
|
kfree_sensitive(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) |
|
{ |
|
kfree_sensitive(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; |
|
char ino_str[50] = ""; |
|
|
|
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); |
|
|
|
/* If the inode is currently being created, ino may still be 0. */ |
|
if (ino) |
|
snprintf(ino_str, sizeof(ino_str), ", including ino %lu", ino); |
|
|
|
fscrypt_warn(NULL, |
|
"%s: %zu inode(s) still busy after removing key with %s %*phN%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_str); |
|
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)) { |
|
wipe_master_key_secret(&mk->mk_secret); |
|
dead = refcount_dec_and_test(&mk->mk_refcount); |
|
} |
|
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; |
|
}
|
|
|