diff options
Diffstat (limited to 'fs/crypto/keyring.c')
| -rw-r--r-- | fs/crypto/keyring.c | 735 |
1 files changed, 437 insertions, 298 deletions
diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c index 0b3ffbb4faf4..5e939ea3ac28 100644 --- a/fs/crypto/keyring.c +++ b/fs/crypto/keyring.c @@ -19,15 +19,29 @@ */ #include <crypto/skcipher.h> +#include <linux/export.h> #include <linux/key-type.h> +#include <linux/once.h> #include <linux/random.h> #include <linux/seq_file.h> +#include <linux/unaligned.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)); } @@ -38,76 +52,108 @@ static void move_master_key_secret(struct fscrypt_master_key_secret *dst, memzero_explicit(src, sizeof(*src)); } -static void free_master_key(struct fscrypt_master_key *mk) +static void fscrypt_free_master_key(struct rcu_head *head) { - size_t i; - - wipe_master_key_secret(&mk->mk_secret); - - for (i = 0; i <= FSCRYPT_MODE_MAX; i++) { - fscrypt_destroy_prepared_key(&mk->mk_direct_keys[i]); - fscrypt_destroy_prepared_key(&mk->mk_iv_ino_lblk_64_keys[i]); - fscrypt_destroy_prepared_key(&mk->mk_iv_ino_lblk_32_keys[i]); - } - - key_put(mk->mk_users); + 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); } -static inline bool valid_key_spec(const struct fscrypt_key_specifier *spec) +void fscrypt_put_master_key(struct fscrypt_master_key *mk) { - if (spec->__reserved) - return false; - return master_key_spec_len(spec) != 0; + 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_ONCE(refcount_read(&mk->mk_active_refs) != 0); + if (mk->mk_users) { + /* Clear the keyring so the quota gets released right away. */ + keyring_clear(mk->mk_users); + key_put(mk->mk_users); + mk->mk_users = NULL; + } + call_rcu(&mk->mk_rcu_head, fscrypt_free_master_key); } -static int fscrypt_key_instantiate(struct key *key, - struct key_preparsed_payload *prep) +void fscrypt_put_master_key_activeref(struct super_block *sb, + struct fscrypt_master_key *mk) { - key->payload.data[0] = (struct fscrypt_master_key *)prep->data; - return 0; -} + size_t i; -static void fscrypt_key_destroy(struct key *key) -{ - free_master_key(key->payload.data[0]); -} + 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. + */ -static void fscrypt_key_describe(const struct key *key, struct seq_file *m) -{ - seq_puts(m, key->description); + if (WARN_ON_ONCE(!sb->s_master_keys)) + return; + spin_lock(&sb->s_master_keys->lock); + hlist_del_rcu(&mk->mk_node); + spin_unlock(&sb->s_master_keys->lock); - if (key_is_positive(key)) { - const struct fscrypt_master_key *mk = key->payload.data[0]; + /* + * ->mk_active_refs == 0 implies that ->mk_present is false and + * ->mk_decrypted_inodes is empty. + */ + WARN_ON_ONCE(mk->mk_present); + WARN_ON_ONCE(!list_empty(&mk->mk_decrypted_inodes)); - if (!is_master_key_secret_present(&mk->mk_secret)) - seq_puts(m, ": secret removed"); + 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); } /* - * Type of key in ->s_master_keys. Each key of this type represents a master - * key which has been added to the filesystem. Its payload is a - * 'struct fscrypt_master_key'. The "." prefix in the key type name prevents - * users from adding keys of this type via the keyrings syscalls rather than via - * the intended method of FS_IOC_ADD_ENCRYPTION_KEY. + * This transitions the key state from present to incompletely removed, and then + * potentially to absent (depending on whether inodes remain). */ -static struct key_type key_type_fscrypt = { - .name = "._fscrypt", - .instantiate = fscrypt_key_instantiate, - .destroy = fscrypt_key_destroy, - .describe = fscrypt_key_describe, -}; +static void fscrypt_initiate_key_removal(struct super_block *sb, + struct fscrypt_master_key *mk) +{ + WRITE_ONCE(mk->mk_present, false); + wipe_master_key_secret(&mk->mk_secret); + fscrypt_put_master_key_activeref(sb, 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 + * We just charge FSCRYPT_MAX_RAW_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); + return key_payload_reserve(key, FSCRYPT_MAX_RAW_KEY_SIZE); } static void fscrypt_user_key_describe(const struct key *key, struct seq_file *m) @@ -131,32 +177,6 @@ static struct key_type key_type_fscrypt_user = { .describe = fscrypt_user_key_describe, }; -/* Search ->s_master_keys or ->mk_users */ -static struct key *search_fscrypt_keyring(struct key *keyring, - struct key_type *type, - const char *description) -{ - /* - * We need to mark the keyring reference as "possessed" so that we - * acquire permission to search it, via the KEY_POS_SEARCH permission. - */ - key_ref_t keyref = make_key_ref(keyring, true /* possessed */); - - keyref = keyring_search(keyref, type, 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); -} - -#define FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE \ - (CONST_STRLEN("fscrypt-") + sizeof_field(struct super_block, s_id)) - -#define FSCRYPT_MK_DESCRIPTION_SIZE (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + 1) - #define FSCRYPT_MK_USERS_DESCRIPTION_SIZE \ (CONST_STRLEN("fscrypt-") + 2 * FSCRYPT_KEY_IDENTIFIER_SIZE + \ CONST_STRLEN("-users") + 1) @@ -164,21 +184,6 @@ static struct key *search_fscrypt_keyring(struct key *keyring, #define FSCRYPT_MK_USER_DESCRIPTION_SIZE \ (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + CONST_STRLEN(".uid.") + 10 + 1) -static void format_fs_keyring_description( - char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE], - const struct super_block *sb) -{ - sprintf(description, "fscrypt-%s", sb->s_id); -} - -static void format_mk_description( - char description[FSCRYPT_MK_DESCRIPTION_SIZE], - const struct fscrypt_key_specifier *mk_spec) -{ - sprintf(description, "%*phN", - master_key_spec_len(mk_spec), (u8 *)&mk_spec->u); -} - static void format_mk_users_keyring_description( char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE], const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) @@ -199,20 +204,15 @@ static void format_mk_user_description( /* Create ->s_master_keys if needed. Synchronized by fscrypt_add_key_mutex. */ static int allocate_filesystem_keyring(struct super_block *sb) { - char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE]; - struct key *keyring; + struct fscrypt_keyring *keyring; if (sb->s_master_keys) return 0; - format_fs_keyring_description(description, sb); - keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, - current_cred(), KEY_POS_SEARCH | - KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW, - KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL); - if (IS_ERR(keyring)) - return PTR_ERR(keyring); - + 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 @@ -222,21 +222,76 @@ static int allocate_filesystem_keyring(struct super_block *sb) return 0; } -void fscrypt_sb_free(struct super_block *sb) +/* + * Release all encryption keys that have been added to the filesystem, along + * with the keyring that contains them. + * + * This is called at unmount time, after all potentially-encrypted inodes have + * been evicted. 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) { - key_put(sb->s_master_keys); + 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 potentially-encrypted 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_present. There should be no structural + * refs beyond the one associated with the active ref. + */ + WARN_ON_ONCE(refcount_read(&mk->mk_active_refs) != 1); + WARN_ON_ONCE(refcount_read(&mk->mk_struct_refs) != 1); + WARN_ON_ONCE(!mk->mk_present); + fscrypt_initiate_key_removal(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 in ->s_master_keys. - * Returns ERR_PTR(-ENOKEY) if not found. + * 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 key *fscrypt_find_master_key(struct super_block *sb, - const struct fscrypt_key_specifier *mk_spec) +struct fscrypt_master_key * +fscrypt_find_master_key(struct super_block *sb, + const struct fscrypt_key_specifier *mk_spec) { - struct key *keyring; - char description[FSCRYPT_MK_DESCRIPTION_SIZE]; + struct fscrypt_keyring *keyring; + struct hlist_head *bucket; + struct fscrypt_master_key *mk; /* * Pairs with the smp_store_release() in allocate_filesystem_keyring(). @@ -246,10 +301,38 @@ struct key *fscrypt_find_master_key(struct super_block *sb, */ keyring = smp_load_acquire(&sb->s_master_keys); if (keyring == NULL) - return ERR_PTR(-ENOKEY); /* No keyring yet, so no keys yet. */ - - format_mk_description(description, mk_spec); - return search_fscrypt_keyring(keyring, &key_type_fscrypt, description); + 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) @@ -277,17 +360,30 @@ static int allocate_master_key_users_keyring(struct fscrypt_master_key *mk) 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); - return search_fscrypt_keyring(mk->mk_users, &key_type_fscrypt_user, - description); + + /* + * 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 the master key's key->sem must - * be held for write, or the master key must be still undergoing initialization. + * 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) { @@ -309,7 +405,7 @@ static int add_master_key_user(struct fscrypt_master_key *mk) /* * Remove the current user's "key" from ->mk_users. - * The master key's key->sem must be held for write. + * ->mk_sem must be held for write. * * Returns 0 if removed, -ENOKEY if not found, or another -errno code. */ @@ -327,63 +423,49 @@ static int remove_master_key_user(struct fscrypt_master_key *mk) } /* - * 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. + * 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 fscrypt_master_key_secret *secret, - const struct fscrypt_key_specifier *mk_spec, - struct key *keyring) +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; - char description[FSCRYPT_MK_DESCRIPTION_SIZE]; - struct key *key; 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; - 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; + goto out_put; err = add_master_key_user(mk); if (err) - goto out_free_mk; + goto out_put; } - /* - * 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; + move_master_key_secret(&mk->mk_secret, secret); + mk->mk_present = true; + refcount_set(&mk->mk_active_refs, 1); /* ->mk_present is true */ + 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_free_mk: - free_master_key(mk); +out_put: + fscrypt_put_master_key(mk); return err; } @@ -392,42 +474,41 @@ out_free_mk: 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.) + * 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) { - mk_user = find_master_key_user(mk); + 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; } - } - - /* 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; + if (err) return err; - } } - /* Re-add the secret if needed. */ - if (rekey) + /* If the key is incompletely removed, make it present again. */ + if (!mk->mk_present) { + if (!refcount_inc_not_zero(&mk->mk_active_refs)) { + /* + * Raced with the last active ref being dropped, so the + * key has become, or is about to become, "absent". + * Therefore, we need to allocate a new key struct. + */ + return KEY_DEAD; + } move_master_key_secret(&mk->mk_secret, secret); + WRITE_ONCE(mk->mk_present, true); + } + return 0; } @@ -436,38 +517,36 @@ static int do_add_master_key(struct super_block *sb, const struct fscrypt_key_specifier *mk_spec) { static DEFINE_MUTEX(fscrypt_add_key_mutex); - struct key *key; + struct fscrypt_master_key *mk; 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; + + 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) - goto out_unlock; - err = add_new_master_key(secret, mk_spec, sb->s_master_keys); + 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. + * Found the key in ->s_master_keys. Add the user to ->mk_users + * if needed, and make the key "present" again if possible. */ - down_write(&key->sem); - err = add_existing_master_key(key->payload.data[0], secret); - up_write(&key->sem); + down_write(&mk->mk_sem); + err = add_existing_master_key(mk, secret); + up_write(&mk->mk_sem); if (err == KEY_DEAD) { - /* Key being removed or needs to be removed */ - key_invalidate(key); - key_put(key); - goto retry; + /* + * 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); } - key_put(key); + fscrypt_put_master_key(mk); } -out_unlock: mutex_unlock(&fscrypt_add_key_mutex); return err; } @@ -479,41 +558,79 @@ static int add_master_key(struct super_block *sb, 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; + u8 sw_secret[BLK_CRYPTO_SW_SECRET_SIZE]; + u8 *kdf_key = secret->bytes; + unsigned int kdf_key_size = secret->size; + u8 keyid_kdf_ctx = HKDF_CONTEXT_KEY_IDENTIFIER_FOR_RAW_KEY; /* - * Now that the HKDF context is initialized, the raw key is no - * longer needed. + * For raw keys, the fscrypt master key is used directly as the + * fscrypt KDF key. For hardware-wrapped keys, we have to pass + * the master key to the hardware to derive the KDF key, which + * is then only used to derive non-file-contents subkeys. */ - memzero_explicit(secret->raw, secret->size); + if (secret->is_hw_wrapped) { + err = fscrypt_derive_sw_secret(sb, secret->bytes, + secret->size, sw_secret); + if (err) + return err; + kdf_key = sw_secret; + kdf_key_size = sizeof(sw_secret); + /* + * To avoid weird behavior if someone manages to + * determine sw_secret and add it as a raw key, ensure + * that hardware-wrapped keys and raw keys will have + * different key identifiers by deriving their key + * identifiers using different KDF contexts. + */ + keyid_kdf_ctx = + HKDF_CONTEXT_KEY_IDENTIFIER_FOR_HW_WRAPPED_KEY; + } + fscrypt_init_hkdf(&secret->hkdf, kdf_key, kdf_key_size); + /* + * Now that the KDF context is initialized, the raw KDF key is + * no longer needed. + */ + memzero_explicit(kdf_key, kdf_key_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; + fscrypt_hkdf_expand(&secret->hkdf, keyid_kdf_ctx, NULL, 0, + key_spec->u.identifier, + FSCRYPT_KEY_IDENTIFIER_SIZE); } return do_add_master_key(sb, secret, key_spec); } +/* + * Validate the size of an fscrypt master key being added. Note that this is + * just an initial check, as we don't know which ciphers will be used yet. + * There is a stricter size check later when the key is actually used by a file. + */ +static inline bool fscrypt_valid_key_size(size_t size, u32 add_key_flags) +{ + u32 max_size = (add_key_flags & FSCRYPT_ADD_KEY_FLAG_HW_WRAPPED) ? + FSCRYPT_MAX_HW_WRAPPED_KEY_SIZE : + FSCRYPT_MAX_RAW_KEY_SIZE; + + return size >= FSCRYPT_MIN_KEY_SIZE && size <= max_size; +} + 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) + if (prep->datalen < sizeof(*payload)) + return -EINVAL; + + if (!fscrypt_valid_key_size(prep->datalen - sizeof(*payload), + payload->flags)) return -EINVAL; if (payload->type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR && payload->type != FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) return -EINVAL; - if (payload->__reserved) + if (payload->flags & ~FSCRYPT_ADD_KEY_FLAG_HW_WRAPPED) return -EINVAL; prep->payload.data[0] = kmemdup(payload, prep->datalen, GFP_KERNEL); @@ -557,21 +674,21 @@ static struct key_type key_type_fscrypt_provisioning = { }; /* - * Retrieve the raw key from the Linux keyring key specified by 'key_id', and - * store it into 'secret'. + * Retrieve the 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 key must be of type "fscrypt-provisioning" and must have the 'type' and + * 'flags' field of the payload set to the given values, indicating that the key + * is intended for use for the specified purpose. 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. + * re-mounted. Most users should just provide the key directly instead. */ -static int get_keyring_key(u32 key_id, u32 type, +static int get_keyring_key(u32 key_id, u32 type, u32 flags, struct fscrypt_master_key_secret *secret) { key_ref_t ref; @@ -588,12 +705,16 @@ static int get_keyring_key(u32 key_id, u32 type, 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) + /* + * Don't allow fscrypt v1 keys to be used as v2 keys and vice versa. + * Similarly, don't allow hardware-wrapped keys to be used as + * non-hardware-wrapped keys and vice versa. + */ + if (payload->type != type || payload->flags != flags) goto bad_key; secret->size = key->datalen - sizeof(*payload); - memcpy(secret->raw, payload->raw, secret->size); + memcpy(secret->bytes, payload->raw, secret->size); err = 0; goto out_put; @@ -655,19 +776,28 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg) return -EACCES; memset(&secret, 0, sizeof(secret)); + + if (arg.flags) { + if (arg.flags & ~FSCRYPT_ADD_KEY_FLAG_HW_WRAPPED) + return -EINVAL; + if (arg.key_spec.type != FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) + return -EINVAL; + secret.is_hw_wrapped = true; + } + if (arg.key_id) { if (arg.raw_size != 0) return -EINVAL; - err = get_keyring_key(arg.key_id, arg.key_spec.type, &secret); + err = get_keyring_key(arg.key_id, arg.key_spec.type, arg.flags, + &secret); if (err) goto out_wipe_secret; } else { - if (arg.raw_size < FSCRYPT_MIN_KEY_SIZE || - arg.raw_size > FSCRYPT_MAX_KEY_SIZE) + if (!fscrypt_valid_key_size(arg.raw_size, arg.flags)) return -EINVAL; secret.size = arg.raw_size; err = -EFAULT; - if (copy_from_user(secret.raw, uarg->raw, secret.size)) + if (copy_from_user(secret.bytes, uarg->raw, secret.size)) goto out_wipe_secret; } @@ -688,24 +818,50 @@ out_wipe_secret: } EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key); -/* - * Add the key for '-o test_dummy_encryption' to the filesystem keyring. +static void +fscrypt_get_test_dummy_secret(struct fscrypt_master_key_secret *secret) +{ + static u8 test_key[FSCRYPT_MAX_RAW_KEY_SIZE]; + + get_random_once(test_key, sizeof(test_key)); + + memset(secret, 0, sizeof(*secret)); + secret->size = sizeof(test_key); + memcpy(secret->bytes, test_key, sizeof(test_key)); +} + +void fscrypt_get_test_dummy_key_identifier( + u8 key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) +{ + struct fscrypt_master_key_secret secret; + + fscrypt_get_test_dummy_secret(&secret); + fscrypt_init_hkdf(&secret.hkdf, secret.bytes, secret.size); + fscrypt_hkdf_expand(&secret.hkdf, + HKDF_CONTEXT_KEY_IDENTIFIER_FOR_RAW_KEY, NULL, 0, + key_identifier, FSCRYPT_KEY_IDENTIFIER_SIZE); + wipe_master_key_secret(&secret); +} + +/** + * 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. * - * Use a per-boot random key to prevent people from misusing this option. + * Return: 0 on success, -errno on failure */ 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); - + fscrypt_get_test_dummy_secret(&secret); err = add_master_key(sb, &secret, key_spec); wipe_master_key_secret(&secret); return err; @@ -731,19 +887,19 @@ 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; + struct key *mk_user; 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); + mk = fscrypt_find_master_key(sb, &mk_spec); + if (!mk) { + err = -ENOKEY; goto out; } - mk = key->payload.data[0]; + down_read(&mk->mk_sem); mk_user = find_master_key_user(mk); if (IS_ERR(mk_user)) { err = PTR_ERR(mk_user); @@ -751,7 +907,8 @@ int fscrypt_verify_key_added(struct super_block *sb, key_put(mk_user); err = 0; } - key_put(key); + up_read(&mk->mk_sem); + fscrypt_put_master_key(mk); out: if (err == -ENOKEY && capable(CAP_FOWNER)) err = 0; @@ -779,7 +936,7 @@ static void shrink_dcache_inode(struct inode *inode) static void evict_dentries_for_decrypted_inodes(struct fscrypt_master_key *mk) { - struct fscrypt_info *ci; + struct fscrypt_inode_info *ci; struct inode *inode; struct inode *toput_inode = NULL; @@ -788,7 +945,7 @@ static void evict_dentries_for_decrypted_inodes(struct fscrypt_master_key *mk) 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)) { + if (inode_state_read(inode) & (I_FREEING | I_WILL_FREE | I_NEW)) { spin_unlock(&inode->i_lock); continue; } @@ -829,7 +986,7 @@ static int check_for_busy_inodes(struct super_block *sb, /* select an example file to show for debugging purposes */ struct inode *inode = list_first_entry(&mk->mk_decrypted_inodes, - struct fscrypt_info, + struct fscrypt_inode_info, ci_master_key_link)->ci_inode; ino = inode->i_ino; } @@ -895,15 +1052,14 @@ static int try_to_lock_encrypted_files(struct super_block *sb, * 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. + * To "remove the key itself", first we transition the key to the "incompletely + * removed" state, 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. + * state where it tracks the list of remaining inodes. Userspace can execute + * the ioctl again later to retry eviction, or alternatively can re-add the key. * * For more details, see the "Removing keys" section of * Documentation/filesystems/fscrypt.rst. @@ -913,11 +1069,10 @@ 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; + bool inodes_remain; if (copy_from_user(&arg, uarg, sizeof(arg))) return -EFAULT; @@ -937,12 +1092,10 @@ static int do_remove_key(struct file *filp, void __user *_uarg, bool all_users) 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); + 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) { @@ -951,7 +1104,7 @@ static int do_remove_key(struct file *filp, void __user *_uarg, bool all_users) else err = remove_master_key_user(mk); if (err) { - up_write(&key->sem); + up_write(&mk->mk_sem); goto out_put_key; } if (mk->mk_users->keys.nr_leaves_on_tree != 0) { @@ -963,26 +1116,21 @@ static int do_remove_key(struct file *filp, void __user *_uarg, bool all_users) status_flags |= FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS; err = 0; - up_write(&key->sem); + up_write(&mk->mk_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); + /* No user claims remaining. Initiate removal of the key. */ + err = -ENOKEY; + if (mk->mk_present) { + fscrypt_initiate_key_removal(sb, mk); err = 0; - } else { + } + 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) { @@ -993,12 +1141,12 @@ static int do_remove_key(struct file *filp, void __user *_uarg, bool all_users) } /* * 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. + * key, initiated removal of the key, 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); + fscrypt_put_master_key(mk); if (err == 0) err = put_user(status_flags, &uarg->removal_status_flags); return err; @@ -1022,12 +1170,11 @@ 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). + * incompletely removed. (For an explanation of what these statuses mean and + * how they are represented internally, see struct fscrypt_master_key.) This + * field allows applications to easily determine the status of an encrypted + * directory without using a hack such as trying to open a regular file in it + * (which can confuse the "incompletely removed" status 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 @@ -1045,7 +1192,6 @@ 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; @@ -1062,19 +1208,18 @@ int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg) 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); + mk = fscrypt_find_master_key(sb, &arg.key_spec); + if (!mk) { arg.status = FSCRYPT_KEY_STATUS_ABSENT; err = 0; goto out; } - mk = key->payload.data[0]; - down_read(&key->sem); + down_read(&mk->mk_sem); - if (!is_master_key_secret_present(&mk->mk_secret)) { - arg.status = FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED; + if (!mk->mk_present) { + 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; } @@ -1096,8 +1241,8 @@ int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg) } err = 0; out_release_key: - up_read(&key->sem); - key_put(key); + up_read(&mk->mk_sem); + fscrypt_put_master_key(mk); out: if (!err && copy_to_user(uarg, &arg, sizeof(arg))) err = -EFAULT; @@ -1109,13 +1254,9 @@ int __init fscrypt_init_keyring(void) { int err; - err = register_key_type(&key_type_fscrypt); - if (err) - return err; - err = register_key_type(&key_type_fscrypt_user); if (err) - goto err_unregister_fscrypt; + return err; err = register_key_type(&key_type_fscrypt_provisioning); if (err) @@ -1125,7 +1266,5 @@ int __init fscrypt_init_keyring(void) err_unregister_fscrypt_user: unregister_key_type(&key_type_fscrypt_user); -err_unregister_fscrypt: - unregister_key_type(&key_type_fscrypt); return err; } |