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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
commit2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch)
tree848558de17fb3008cdf4d861b01ac7781903ce39 /fs/crypto/keyring.c
parentInitial commit. (diff)
downloadlinux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz
linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip
Adding upstream version 6.1.76.upstream/6.1.76
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'fs/crypto/keyring.c')
-rw-r--r--fs/crypto/keyring.c1215
1 files changed, 1215 insertions, 0 deletions
diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
new file mode 100644
index 000000000..2a24b1f0a
--- /dev/null
+++ b/fs/crypto/keyring.c
@@ -0,0 +1,1215 @@
+// 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 fscrypt_master_key *mk)
+{
+ struct super_block *sb = mk->mk_sb;
+ struct fscrypt_keyring *keyring = sb->s_master_keys;
+ 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(&keyring->lock);
+ hlist_del_rcu(&mk->mk_node);
+ spin_unlock(&keyring->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).
+ *
+ * This is also called when the super_block is being freed. This is needed to
+ * avoid a memory leak if mounting fails after the "test_dummy_encryption"
+ * option was processed, as in that case the unmount-time call isn't made.
+ */
+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(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;
+
+ mk->mk_sb = sb;
+ 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
+ * @dummy_policy: the encryption policy for test_dummy_encryption
+ *
+ * If needed, 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,
+ const struct fscrypt_dummy_policy *dummy_policy)
+{
+ const union fscrypt_policy *policy = dummy_policy->policy;
+ struct fscrypt_key_specifier key_spec;
+ struct fscrypt_master_key_secret secret;
+ int err;
+
+ if (!policy)
+ return 0;
+ err = fscrypt_policy_to_key_spec(policy, &key_spec);
+ if (err)
+ return err;
+ fscrypt_get_test_dummy_secret(&secret);
+ err = add_master_key(sb, &secret, &key_spec);
+ wipe_master_key_secret(&secret);
+ return err;
+}
+EXPORT_SYMBOL_GPL(fscrypt_add_test_dummy_key);
+
+/*
+ * Verify that the current user has added a master key with the given identifier
+ * (returns -ENOKEY if not). This is needed to prevent a user from encrypting
+ * their files using some other user's key which they don't actually know.
+ * Cryptographically this isn't much of a problem, but the semantics of this
+ * would be a bit weird, so it's best to just forbid it.
+ *
+ * The system administrator (CAP_FOWNER) can override this, which should be
+ * enough for any use cases where encryption policies are being set using keys
+ * that were chosen ahead of time but aren't available at the moment.
+ *
+ * Note that the key may have already removed by the time this returns, but
+ * that's okay; we just care whether the key was there at some point.
+ *
+ * Return: 0 if the key is added, -ENOKEY if it isn't, or another -errno code
+ */
+int fscrypt_verify_key_added(struct super_block *sb,
+ const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
+{
+ struct fscrypt_key_specifier mk_spec;
+ struct 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(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;
+}