| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * Filesystem-level keyring for fscrypt |
| * |
| * Copyright 2019 Google LLC |
| */ |
| |
| /* |
| * This file implements management of fscrypt master keys in the |
| * filesystem-level keyring, including the ioctls: |
| * |
| * - FS_IOC_ADD_ENCRYPTION_KEY |
| * - FS_IOC_REMOVE_ENCRYPTION_KEY |
| * - FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS |
| * - FS_IOC_GET_ENCRYPTION_KEY_STATUS |
| * |
| * See the "User API" section of Documentation/filesystems/fscrypt.rst for more |
| * information about these ioctls. |
| */ |
| |
| #include <asm/unaligned.h> |
| #include <crypto/skcipher.h> |
| #include <linux/key-type.h> |
| #include <linux/random.h> |
| #include <linux/seq_file.h> |
| |
| #include "fscrypt_private.h" |
| |
| /* The master encryption keys for a filesystem (->s_master_keys) */ |
| struct fscrypt_keyring { |
| /* |
| * Lock that protects ->key_hashtable. It does *not* protect the |
| * fscrypt_master_key structs themselves. |
| */ |
| spinlock_t lock; |
| |
| /* Hash table that maps fscrypt_key_specifier to fscrypt_master_key */ |
| struct hlist_head key_hashtable[128]; |
| }; |
| |
| static void wipe_master_key_secret(struct fscrypt_master_key_secret *secret) |
| { |
| fscrypt_destroy_hkdf(&secret->hkdf); |
| memzero_explicit(secret, sizeof(*secret)); |
| } |
| |
| static void move_master_key_secret(struct fscrypt_master_key_secret *dst, |
| struct fscrypt_master_key_secret *src) |
| { |
| memcpy(dst, src, sizeof(*dst)); |
| memzero_explicit(src, sizeof(*src)); |
| } |
| |
| static void fscrypt_free_master_key(struct rcu_head *head) |
| { |
| struct fscrypt_master_key *mk = |
| container_of(head, struct fscrypt_master_key, mk_rcu_head); |
| /* |
| * The master key secret and any embedded subkeys should have already |
| * been wiped when the last active reference to the fscrypt_master_key |
| * struct was dropped; doing it here would be unnecessarily late. |
| * Nevertheless, use kfree_sensitive() in case anything was missed. |
| */ |
| kfree_sensitive(mk); |
| } |
| |
| void fscrypt_put_master_key(struct fscrypt_master_key *mk) |
| { |
| if (!refcount_dec_and_test(&mk->mk_struct_refs)) |
| return; |
| /* |
| * No structural references left, so free ->mk_users, and also free the |
| * fscrypt_master_key struct itself after an RCU grace period ensures |
| * that concurrent keyring lookups can no longer find it. |
| */ |
| WARN_ON(refcount_read(&mk->mk_active_refs) != 0); |
| key_put(mk->mk_users); |
| mk->mk_users = NULL; |
| call_rcu(&mk->mk_rcu_head, fscrypt_free_master_key); |
| } |
| |
| void fscrypt_put_master_key_activeref(struct super_block *sb, |
| struct fscrypt_master_key *mk) |
| { |
| size_t i; |
| |
| if (!refcount_dec_and_test(&mk->mk_active_refs)) |
| return; |
| /* |
| * No active references left, so complete the full removal of this |
| * fscrypt_master_key struct by removing it from the keyring and |
| * destroying any subkeys embedded in it. |
| */ |
| |
| spin_lock(&sb->s_master_keys->lock); |
| hlist_del_rcu(&mk->mk_node); |
| spin_unlock(&sb->s_master_keys->lock); |
| |
| /* |
| * ->mk_active_refs == 0 implies that ->mk_secret is not present and |
| * that ->mk_decrypted_inodes is empty. |
| */ |
| WARN_ON(is_master_key_secret_present(&mk->mk_secret)); |
| WARN_ON(!list_empty(&mk->mk_decrypted_inodes)); |
| |
| for (i = 0; i <= FSCRYPT_MODE_MAX; i++) { |
| fscrypt_destroy_prepared_key( |
| sb, &mk->mk_direct_keys[i]); |
| fscrypt_destroy_prepared_key( |
| sb, &mk->mk_iv_ino_lblk_64_keys[i]); |
| fscrypt_destroy_prepared_key( |
| sb, &mk->mk_iv_ino_lblk_32_keys[i]); |
| } |
| memzero_explicit(&mk->mk_ino_hash_key, |
| sizeof(mk->mk_ino_hash_key)); |
| mk->mk_ino_hash_key_initialized = false; |
| |
| /* Drop the structural ref associated with the active refs. */ |
| fscrypt_put_master_key(mk); |
| } |
| |
| static inline bool valid_key_spec(const struct fscrypt_key_specifier *spec) |
| { |
| if (spec->__reserved) |
| return false; |
| return master_key_spec_len(spec) != 0; |
| } |
| |
| static int fscrypt_user_key_instantiate(struct key *key, |
| struct key_preparsed_payload *prep) |
| { |
| /* |
| * We just charge FSCRYPT_MAX_KEY_SIZE bytes to the user's key quota for |
| * each key, regardless of the exact key size. The amount of memory |
| * actually used is greater than the size of the raw key anyway. |
| */ |
| return key_payload_reserve(key, FSCRYPT_MAX_KEY_SIZE); |
| } |
| |
| static void fscrypt_user_key_describe(const struct key *key, struct seq_file *m) |
| { |
| seq_puts(m, key->description); |
| } |
| |
| /* |
| * Type of key in ->mk_users. Each key of this type represents a particular |
| * user who has added a particular master key. |
| * |
| * Note that the name of this key type really should be something like |
| * ".fscrypt-user" instead of simply ".fscrypt". But the shorter name is chosen |
| * mainly for simplicity of presentation in /proc/keys when read by a non-root |
| * user. And it is expected to be rare that a key is actually added by multiple |
| * users, since users should keep their encryption keys confidential. |
| */ |
| static struct key_type key_type_fscrypt_user = { |
| .name = ".fscrypt", |
| .instantiate = fscrypt_user_key_instantiate, |
| .describe = fscrypt_user_key_describe, |
| }; |
| |
| #define FSCRYPT_MK_USERS_DESCRIPTION_SIZE \ |
| (CONST_STRLEN("fscrypt-") + 2 * FSCRYPT_KEY_IDENTIFIER_SIZE + \ |
| CONST_STRLEN("-users") + 1) |
| |
| #define FSCRYPT_MK_USER_DESCRIPTION_SIZE \ |
| (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + CONST_STRLEN(".uid.") + 10 + 1) |
| |
| static void format_mk_users_keyring_description( |
| char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE], |
| const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) |
| { |
| sprintf(description, "fscrypt-%*phN-users", |
| FSCRYPT_KEY_IDENTIFIER_SIZE, mk_identifier); |
| } |
| |
| static void format_mk_user_description( |
| char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE], |
| const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) |
| { |
| |
| sprintf(description, "%*phN.uid.%u", FSCRYPT_KEY_IDENTIFIER_SIZE, |
| mk_identifier, __kuid_val(current_fsuid())); |
| } |
| |
| /* Create ->s_master_keys if needed. Synchronized by fscrypt_add_key_mutex. */ |
| static int allocate_filesystem_keyring(struct super_block *sb) |
| { |
| struct fscrypt_keyring *keyring; |
| |
| if (sb->s_master_keys) |
| return 0; |
| |
| keyring = kzalloc(sizeof(*keyring), GFP_KERNEL); |
| if (!keyring) |
| return -ENOMEM; |
| spin_lock_init(&keyring->lock); |
| /* |
| * 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; |
| } |
| |
| /* |
| * Release all encryption keys that have been added to the filesystem, along |
| * with the keyring that contains them. |
| * |
| * This is called at unmount time. The filesystem's underlying block device(s) |
| * are still available at this time; this is important because after user file |
| * accesses have been allowed, this function may need to evict keys from the |
| * keyslots of an inline crypto engine, which requires the block device(s). |
| */ |
| void fscrypt_destroy_keyring(struct super_block *sb) |
| { |
| struct fscrypt_keyring *keyring = sb->s_master_keys; |
| size_t i; |
| |
| if (!keyring) |
| return; |
| |
| for (i = 0; i < ARRAY_SIZE(keyring->key_hashtable); i++) { |
| struct hlist_head *bucket = &keyring->key_hashtable[i]; |
| struct fscrypt_master_key *mk; |
| struct hlist_node *tmp; |
| |
| hlist_for_each_entry_safe(mk, tmp, bucket, mk_node) { |
| /* |
| * Since all inodes were already evicted, every key |
| * remaining in the keyring should have an empty inode |
| * list, and should only still be in the keyring due to |
| * the single active ref associated with ->mk_secret. |
| * There should be no structural refs beyond the one |
| * associated with the active ref. |
| */ |
| WARN_ON(refcount_read(&mk->mk_active_refs) != 1); |
| WARN_ON(refcount_read(&mk->mk_struct_refs) != 1); |
| WARN_ON(!is_master_key_secret_present(&mk->mk_secret)); |
| wipe_master_key_secret(&mk->mk_secret); |
| fscrypt_put_master_key_activeref(sb, mk); |
| } |
| } |
| kfree_sensitive(keyring); |
| sb->s_master_keys = NULL; |
| } |
| |
| static struct hlist_head * |
| fscrypt_mk_hash_bucket(struct fscrypt_keyring *keyring, |
| const struct fscrypt_key_specifier *mk_spec) |
| { |
| /* |
| * Since key specifiers should be "random" values, it is sufficient to |
| * use a trivial hash function that just takes the first several bits of |
| * the key specifier. |
| */ |
| unsigned long i = get_unaligned((unsigned long *)&mk_spec->u); |
| |
| return &keyring->key_hashtable[i % ARRAY_SIZE(keyring->key_hashtable)]; |
| } |
| |
| /* |
| * Find the specified master key struct in ->s_master_keys and take a structural |
| * ref to it. The structural ref guarantees that the key struct continues to |
| * exist, but it does *not* guarantee that ->s_master_keys continues to contain |
| * the key struct. The structural ref needs to be dropped by |
| * fscrypt_put_master_key(). Returns NULL if the key struct is not found. |
| */ |
| struct fscrypt_master_key * |
| fscrypt_find_master_key(struct super_block *sb, |
| const struct fscrypt_key_specifier *mk_spec) |
| { |
| struct fscrypt_keyring *keyring; |
| struct hlist_head *bucket; |
| struct fscrypt_master_key *mk; |
| |
| /* |
| * 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. |
| */ |
| keyring = smp_load_acquire(&sb->s_master_keys); |
| if (keyring == NULL) |
| return NULL; /* No keyring yet, so no keys yet. */ |
| |
| bucket = fscrypt_mk_hash_bucket(keyring, mk_spec); |
| rcu_read_lock(); |
| switch (mk_spec->type) { |
| case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR: |
| hlist_for_each_entry_rcu(mk, bucket, mk_node) { |
| if (mk->mk_spec.type == |
| FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR && |
| memcmp(mk->mk_spec.u.descriptor, |
| mk_spec->u.descriptor, |
| FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 && |
| refcount_inc_not_zero(&mk->mk_struct_refs)) |
| goto out; |
| } |
| break; |
| case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER: |
| hlist_for_each_entry_rcu(mk, bucket, mk_node) { |
| if (mk->mk_spec.type == |
| FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER && |
| memcmp(mk->mk_spec.u.identifier, |
| mk_spec->u.identifier, |
| FSCRYPT_KEY_IDENTIFIER_SIZE) == 0 && |
| refcount_inc_not_zero(&mk->mk_struct_refs)) |
| goto out; |
| } |
| break; |
| } |
| mk = NULL; |
| out: |
| rcu_read_unlock(); |
| return mk; |
| } |
| |
| 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); |
| keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, |
| current_cred(), KEY_POS_SEARCH | |
| KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW, |
| KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL); |
| if (IS_ERR(keyring)) |
| return PTR_ERR(keyring); |
| |
| mk->mk_users = keyring; |
| return 0; |
| } |
| |
| /* |
| * Find the current user's "key" in the master key's ->mk_users. |
| * Returns ERR_PTR(-ENOKEY) if not found. |
| */ |
| static struct key *find_master_key_user(struct fscrypt_master_key *mk) |
| { |
| char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE]; |
| key_ref_t keyref; |
| |
| format_mk_user_description(description, mk->mk_spec.u.identifier); |
| |
| /* |
| * We need to mark the keyring reference as "possessed" so that we |
| * acquire permission to search it, via the KEY_POS_SEARCH permission. |
| */ |
| keyref = keyring_search(make_key_ref(mk->mk_users, true /*possessed*/), |
| &key_type_fscrypt_user, description, false); |
| if (IS_ERR(keyref)) { |
| if (PTR_ERR(keyref) == -EAGAIN || /* not found */ |
| PTR_ERR(keyref) == -EKEYREVOKED) /* recently invalidated */ |
| keyref = ERR_PTR(-ENOKEY); |
| return ERR_CAST(keyref); |
| } |
| return key_ref_to_ptr(keyref); |
| } |
| |
| /* |
| * 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 ->mk_sem must be held for |
| * write, or the master key must be still undergoing initialization. |
| */ |
| static int add_master_key_user(struct fscrypt_master_key *mk) |
| { |
| char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE]; |
| struct key *mk_user; |
| int err; |
| |
| format_mk_user_description(description, mk->mk_spec.u.identifier); |
| mk_user = key_alloc(&key_type_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); |
| |
| err = key_instantiate_and_link(mk_user, NULL, 0, mk->mk_users, NULL); |
| key_put(mk_user); |
| return err; |
| } |
| |
| /* |
| * Remove the current user's "key" from ->mk_users. |
| * ->mk_sem must be held for write. |
| * |
| * Returns 0 if removed, -ENOKEY if not found, or another -errno code. |
| */ |
| static int remove_master_key_user(struct 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, transfer the given secret over to it, and |
| * insert it into sb->s_master_keys. |
| */ |
| static int add_new_master_key(struct super_block *sb, |
| struct fscrypt_master_key_secret *secret, |
| const struct fscrypt_key_specifier *mk_spec) |
| { |
| struct fscrypt_keyring *keyring = sb->s_master_keys; |
| struct fscrypt_master_key *mk; |
| int err; |
| |
| mk = kzalloc(sizeof(*mk), GFP_KERNEL); |
| if (!mk) |
| return -ENOMEM; |
| |
| init_rwsem(&mk->mk_sem); |
| refcount_set(&mk->mk_struct_refs, 1); |
| mk->mk_spec = *mk_spec; |
| |
| 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_put; |
| err = add_master_key_user(mk); |
| if (err) |
| goto out_put; |
| } |
| |
| move_master_key_secret(&mk->mk_secret, secret); |
| refcount_set(&mk->mk_active_refs, 1); /* ->mk_secret is present */ |
| |
| spin_lock(&keyring->lock); |
| hlist_add_head_rcu(&mk->mk_node, |
| fscrypt_mk_hash_bucket(keyring, mk_spec)); |
| spin_unlock(&keyring->lock); |
| return 0; |
| |
| out_put: |
| fscrypt_put_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) |
| { |
| int err; |
| |
| /* |
| * If the current user is already in ->mk_users, then there's nothing to |
| * do. Otherwise, we need to add the user to ->mk_users. (Neither is |
| * applicable for v1 policy keys, which have NULL ->mk_users.) |
| */ |
| if (mk->mk_users) { |
| struct key *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; |
| } |
| err = add_master_key_user(mk); |
| if (err) |
| return err; |
| } |
| |
| /* Re-add the secret if needed. */ |
| if (!is_master_key_secret_present(&mk->mk_secret)) { |
| if (!refcount_inc_not_zero(&mk->mk_active_refs)) |
| return KEY_DEAD; |
| 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 fscrypt_master_key *mk; |
| int err; |
| |
| mutex_lock(&fscrypt_add_key_mutex); /* serialize find + link */ |
| |
| mk = fscrypt_find_master_key(sb, mk_spec); |
| if (!mk) { |
| /* Didn't find the key in ->s_master_keys. Add it. */ |
| err = allocate_filesystem_keyring(sb); |
| if (!err) |
| err = add_new_master_key(sb, secret, mk_spec); |
| } 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(&mk->mk_sem); |
| err = add_existing_master_key(mk, secret); |
| up_write(&mk->mk_sem); |
| if (err == KEY_DEAD) { |
| /* |
| * We found a key struct, but it's already been fully |
| * removed. Ignore the old struct and add a new one. |
| * fscrypt_add_key_mutex means we don't need to worry |
| * about concurrent adds. |
| */ |
| err = add_new_master_key(sb, secret, mk_spec); |
| } |
| fscrypt_put_master_key(mk); |
| } |
| 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); |
| |
| static void |
| fscrypt_get_test_dummy_secret(struct fscrypt_master_key_secret *secret) |
| { |
| static u8 test_key[FSCRYPT_MAX_KEY_SIZE]; |
| |
| 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); |
| } |
| |
| int fscrypt_get_test_dummy_key_identifier( |
| u8 key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) |
| { |
| struct fscrypt_master_key_secret secret; |
| int err; |
| |
| fscrypt_get_test_dummy_secret(&secret); |
| |
| err = fscrypt_init_hkdf(&secret.hkdf, secret.raw, secret.size); |
| if (err) |
| goto out; |
| err = fscrypt_hkdf_expand(&secret.hkdf, HKDF_CONTEXT_KEY_IDENTIFIER, |
| NULL, 0, key_identifier, |
| FSCRYPT_KEY_IDENTIFIER_SIZE); |
| out: |
| wipe_master_key_secret(&secret); |
| return err; |
| } |
| |
| /** |
| * fscrypt_add_test_dummy_key() - add the test dummy encryption key |
| * @sb: the filesystem instance to add the key to |
| * @key_spec: the key specifier of the test dummy encryption key |
| * |
| * Add the key for the test_dummy_encryption mount option to the filesystem. To |
| * prevent misuse of this mount option, a per-boot random key is used instead of |
| * a hardcoded one. This makes it so that any encrypted files created using |
| * this option won't be accessible after a reboot. |
| * |
| * Return: 0 on success, -errno on failure |
| */ |
| int fscrypt_add_test_dummy_key(struct super_block *sb, |
| struct fscrypt_key_specifier *key_spec) |
| { |
| struct fscrypt_master_key_secret secret; |
| int err; |
| |
| fscrypt_get_test_dummy_secret(&secret); |
| 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 fscrypt_master_key *mk; |
| struct key *mk_user; |
| int err; |
| |
| mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER; |
| memcpy(mk_spec.u.identifier, identifier, FSCRYPT_KEY_IDENTIFIER_SIZE); |
| |
| mk = fscrypt_find_master_key(sb, &mk_spec); |
| if (!mk) { |
| err = -ENOKEY; |
| goto out; |
| } |
| down_read(&mk->mk_sem); |
| mk_user = find_master_key_user(mk); |
| if (IS_ERR(mk_user)) { |
| err = PTR_ERR(mk_user); |
| } else { |
| key_put(mk_user); |
| err = 0; |
| } |
| up_read(&mk->mk_sem); |
| fscrypt_put_master_key(mk); |
| 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 fscrypt_master_key *mk; |
| u32 status_flags = 0; |
| int err; |
| bool inodes_remain; |
| |
| 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. */ |
| mk = fscrypt_find_master_key(sb, &arg.key_spec); |
| if (!mk) |
| return -ENOKEY; |
| down_write(&mk->mk_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(&mk->mk_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(&mk->mk_sem); |
| goto out_put_key; |
| } |
| } |
| |
| /* No user claims remaining. Go ahead and wipe the secret. */ |
| err = -ENOKEY; |
| if (is_master_key_secret_present(&mk->mk_secret)) { |
| wipe_master_key_secret(&mk->mk_secret); |
| fscrypt_put_master_key_activeref(sb, mk); |
| err = 0; |
| } |
| inodes_remain = refcount_read(&mk->mk_active_refs) > 0; |
| up_write(&mk->mk_sem); |
| |
| if (inodes_remain) { |
| /* 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: |
| fscrypt_put_master_key(mk); |
| 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 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)); |
| |
| mk = fscrypt_find_master_key(sb, &arg.key_spec); |
| if (!mk) { |
| arg.status = FSCRYPT_KEY_STATUS_ABSENT; |
| err = 0; |
| goto out; |
| } |
| down_read(&mk->mk_sem); |
| |
| if (!is_master_key_secret_present(&mk->mk_secret)) { |
| arg.status = refcount_read(&mk->mk_active_refs) > 0 ? |
| FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED : |
| FSCRYPT_KEY_STATUS_ABSENT /* raced with full removal */; |
| 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(&mk->mk_sem); |
| fscrypt_put_master_key(mk); |
| 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_user); |
| if (err) |
| return err; |
| |
| 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); |
| return err; |
| } |