diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst index 895e9711ed88..e0204a23e997 100644 --- a/Documentation/filesystems/fsverity.rst +++ b/Documentation/filesystems/fsverity.rst @@ -27,9 +27,9 @@ automatically verified against the file's Merkle tree. Reads of any corrupted data, including mmap reads, will fail. Userspace can use another ioctl to retrieve the root hash (actually -the "file measurement", which is a hash that includes the root hash) -that fs-verity is enforcing for the file. This ioctl executes in -constant time, regardless of the file size. +the "fs-verity file digest", which is a hash that includes the Merkle +tree root hash) that fs-verity is enforcing for the file. This ioctl +executes in constant time, regardless of the file size. fs-verity is essentially a way to hash a file in constant time, subject to the caveat that reads which would violate the hash will @@ -177,9 +177,10 @@ FS_IOC_ENABLE_VERITY can fail with the following errors: FS_IOC_MEASURE_VERITY --------------------- -The FS_IOC_MEASURE_VERITY ioctl retrieves the measurement of a verity -file. The file measurement is a digest that cryptographically -identifies the file contents that are being enforced on reads. +The FS_IOC_MEASURE_VERITY ioctl retrieves the digest of a verity file. +The fs-verity file digest is a cryptographic digest that identifies +the file contents that are being enforced on reads; it is computed via +a Merkle tree and is different from a traditional full-file digest. This ioctl takes in a pointer to a variable-length structure:: @@ -197,7 +198,7 @@ On success, 0 is returned and the kernel fills in the structure as follows: - ``digest_algorithm`` will be the hash algorithm used for the file - measurement. It will match ``fsverity_enable_arg::hash_algorithm``. + digest. It will match ``fsverity_enable_arg::hash_algorithm``. - ``digest_size`` will be the size of the digest in bytes, e.g. 32 for SHA-256. (This can be redundant with ``digest_algorithm``.) - ``digest`` will be the actual bytes of the digest. @@ -257,25 +258,24 @@ non-verity one, with the following exceptions: with EIO (for read()) or SIGBUS (for mmap() reads). - If the sysctl "fs.verity.require_signatures" is set to 1 and the - file's verity measurement is not signed by a key in the fs-verity - keyring, then opening the file will fail. See `Built-in signature - verification`_. + file is not signed by a key in the fs-verity keyring, then opening + the file will fail. See `Built-in signature verification`_. Direct access to the Merkle tree is not supported. Therefore, if a verity file is copied, or is backed up and restored, then it will lose its "verity"-ness. fs-verity is primarily meant for files like executables that are managed by a package manager. -File measurement computation -============================ +File digest computation +======================= This section describes how fs-verity hashes the file contents using a -Merkle tree to produce the "file measurement" which cryptographically -identifies the file contents. This algorithm is the same for all -filesystems that support fs-verity. +Merkle tree to produce the digest which cryptographically identifies +the file contents. This algorithm is the same for all filesystems +that support fs-verity. Userspace only needs to be aware of this algorithm if it needs to -compute the file measurement itself, e.g. in order to sign the file. +compute fs-verity file digests itself, e.g. in order to sign files. .. _fsverity_merkle_tree: @@ -325,26 +325,22 @@ can't a distinguish a large file from a small second file whose data is exactly the top-level hash block of the first file. Ambiguities also arise from the convention of padding to the next block boundary. -To solve this problem, the verity file measurement is actually -computed as a hash of the following structure, which contains the -Merkle tree root hash as well as other fields such as the file size:: +To solve this problem, the fs-verity file digest is actually computed +as a hash of the following structure, which contains the Merkle tree +root hash as well as other fields such as the file size:: struct fsverity_descriptor { __u8 version; /* must be 1 */ __u8 hash_algorithm; /* Merkle tree hash algorithm */ __u8 log_blocksize; /* log2 of size of data and tree blocks */ __u8 salt_size; /* size of salt in bytes; 0 if none */ - __le32 sig_size; /* must be 0 */ + __le32 __reserved_0x04; /* must be 0 */ __le64 data_size; /* size of file the Merkle tree is built over */ __u8 root_hash[64]; /* Merkle tree root hash */ __u8 salt[32]; /* salt prepended to each hashed block */ __u8 __reserved[144]; /* must be 0's */ }; -Note that the ``sig_size`` field must be set to 0 for the purpose of -computing the file measurement, even if a signature was provided (or -will be provided) to `FS_IOC_ENABLE_VERITY`_. - Built-in signature verification =============================== @@ -359,20 +355,20 @@ kernel. Specifically, it adds support for: certificates from being added. 2. `FS_IOC_ENABLE_VERITY`_ accepts a pointer to a PKCS#7 formatted - detached signature in DER format of the file measurement. On - success, this signature is persisted alongside the Merkle tree. + detached signature in DER format of the file's fs-verity digest. + On success, this signature is persisted alongside the Merkle tree. Then, any time the file is opened, the kernel will verify the - file's actual measurement against this signature, using the - certificates in the ".fs-verity" keyring. + file's actual digest against this signature, using the certificates + in the ".fs-verity" keyring. 3. A new sysctl "fs.verity.require_signatures" is made available. When set to 1, the kernel requires that all verity files have a - correctly signed file measurement as described in (2). + correctly signed digest as described in (2). -File measurements must be signed in the following format, which is -similar to the structure used by `FS_IOC_MEASURE_VERITY`_:: +fs-verity file digests must be signed in the following format, which +is similar to the structure used by `FS_IOC_MEASURE_VERITY`_:: - struct fsverity_signed_digest { + struct fsverity_formatted_digest { char magic[8]; /* must be "FSVerity" */ __le16 digest_algorithm; __le16 digest_size; @@ -421,8 +417,8 @@ can only be set by `FS_IOC_ENABLE_VERITY`_, and it cannot be cleared. ext4 also supports encryption, which can be used simultaneously with fs-verity. In this case, the plaintext data is verified rather than -the ciphertext. This is necessary in order to make the file -measurement meaningful, since every file is encrypted differently. +the ciphertext. This is necessary in order to make the fs-verity file +digest meaningful, since every file is encrypted differently. ext4 stores the verity metadata (Merkle tree and fsverity_descriptor) past the end of the file, starting at the first 64K boundary beyond @@ -592,8 +588,8 @@ weren't already directly answered in other parts of this document. :Q: Isn't fs-verity useless because the attacker can just modify the hashes in the Merkle tree, which is stored on-disk? :A: To verify the authenticity of an fs-verity file you must verify - the authenticity of the "file measurement", which is basically the - root hash of the Merkle tree. See `Use cases`_. + the authenticity of the "fs-verity file digest", which + incorporates the root hash of the Merkle tree. See `Use cases`_. :Q: Isn't fs-verity useless because the attacker can just replace a verity file with a non-verity one? diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c index cb3cfa6329ba..f3cd592f5171 100644 --- a/fs/crypto/fname.c +++ b/fs/crypto/fname.c @@ -404,7 +404,7 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname, fname->disk_name.len = iname->len; return 0; } - ret = fscrypt_get_encryption_info(dir); + ret = fscrypt_get_encryption_info(dir, lookup); if (ret) return ret; @@ -560,7 +560,11 @@ int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags) return -ECHILD; dir = dget_parent(dentry); - err = fscrypt_get_encryption_info(d_inode(dir)); + /* + * Pass allow_unsupported=true, so that files with an unsupported + * encryption policy can be deleted. + */ + err = fscrypt_get_encryption_info(d_inode(dir), true); valid = !fscrypt_has_encryption_key(d_inode(dir)); dput(dir); diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index 6d19b8e4fa6a..a455e29e807e 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -469,16 +469,9 @@ struct fscrypt_master_key { * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again. * - * Locking: protected by key->sem (outer) and mk_secret_sem (inner). - * The reason for two locks is that key->sem also protects modifying - * mk_users, which ranks it above the semaphore for the keyring key - * type, which is in turn above page faults (via keyring_read). But - * sometimes filesystems call fscrypt_get_encryption_info() from within - * a transaction, which ranks it below page faults. So we need a - * separate lock which protects mk_secret but not also mk_users. + * Locking: protected by this master key's key->sem. */ struct fscrypt_master_key_secret mk_secret; - struct rw_semaphore mk_secret_sem; /* * For v1 policy keys: an arbitrary key descriptor which was assigned by @@ -497,8 +490,8 @@ struct fscrypt_master_key { * * This is NULL for v1 policy keys; those can only be added by root. * - * Locking: in addition to this keyrings own semaphore, this is - * protected by the master key's key->sem, so we can do atomic + * Locking: in addition to this keyring's own semaphore, this is + * protected by this master key's key->sem, so we can do atomic * search+insert. It can also be searched without taking any locks, but * in that case the returned key may have already been removed. */ @@ -540,9 +533,9 @@ is_master_key_secret_present(const struct fscrypt_master_key_secret *secret) /* * The READ_ONCE() is only necessary for fscrypt_drop_inode() and * fscrypt_key_describe(). These run in atomic context, so they can't - * take ->mk_secret_sem and thus 'secret' can change concurrently which - * would be a data race. But they only need to know whether the secret - * *was* present at the time of check, so READ_ONCE() suffices. + * take the key semaphore and thus 'secret' can change concurrently + * which would be a data race. But they only need to know whether the + * secret *was* present at the time of check, so READ_ONCE() suffices. */ return READ_ONCE(secret->size) != 0; } @@ -609,6 +602,34 @@ int fscrypt_derive_dirhash_key(struct fscrypt_info *ci, void fscrypt_hash_inode_number(struct fscrypt_info *ci, const struct fscrypt_master_key *mk); +int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported); + +/** + * fscrypt_require_key() - require an inode's encryption key + * @inode: the inode we need the key for + * + * If the inode is encrypted, set up its encryption key if not already done. + * Then require that the key be present and return -ENOKEY otherwise. + * + * No locks are needed, and the key will live as long as the struct inode --- so + * it won't go away from under you. + * + * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code + * if a problem occurred while setting up the encryption key. + */ +static inline int fscrypt_require_key(struct inode *inode) +{ + if (IS_ENCRYPTED(inode)) { + int err = fscrypt_get_encryption_info(inode, false); + + if (err) + return err; + if (!fscrypt_has_encryption_key(inode)) + return -ENOKEY; + } + return 0; +} + /* keysetup_v1.c */ void fscrypt_put_direct_key(struct fscrypt_direct_key *dk); diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c index 63a7c845f74a..a73b0376e6f3 100644 --- a/fs/crypto/hooks.c +++ b/fs/crypto/hooks.c @@ -54,15 +54,12 @@ EXPORT_SYMBOL_GPL(fscrypt_file_open); int __fscrypt_prepare_link(struct inode *inode, struct inode *dir, struct dentry *dentry) { - int err; - - err = fscrypt_require_key(dir); - if (err) - return err; - - /* ... in case we looked up no-key name before key was added */ if (fscrypt_is_nokey_name(dentry)) return -ENOKEY; + /* + * We don't need to separately check that the directory inode's key is + * available, as it's implied by the dentry not being a no-key name. + */ if (!fscrypt_has_permitted_context(dir, inode)) return -EXDEV; @@ -75,20 +72,13 @@ int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry, unsigned int flags) { - int err; - - err = fscrypt_require_key(old_dir); - if (err) - return err; - - err = fscrypt_require_key(new_dir); - if (err) - return err; - - /* ... in case we looked up no-key name(s) before key was added */ if (fscrypt_is_nokey_name(old_dentry) || fscrypt_is_nokey_name(new_dentry)) return -ENOKEY; + /* + * We don't need to separately check that the directory inodes' keys are + * available, as it's implied by the dentries not being no-key names. + */ if (old_dir != new_dir) { if (IS_ENCRYPTED(new_dir) && @@ -123,6 +113,20 @@ int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry, } EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup); +int __fscrypt_prepare_readdir(struct inode *dir) +{ + return fscrypt_get_encryption_info(dir, true); +} +EXPORT_SYMBOL_GPL(__fscrypt_prepare_readdir); + +int __fscrypt_prepare_setattr(struct dentry *dentry, struct iattr *attr) +{ + if (attr->ia_valid & ATTR_SIZE) + return fscrypt_require_key(d_inode(dentry)); + return 0; +} +EXPORT_SYMBOL_GPL(__fscrypt_prepare_setattr); + /** * fscrypt_prepare_setflags() - prepare to change flags with FS_IOC_SETFLAGS * @inode: the inode on which flags are being changed @@ -138,6 +142,7 @@ int fscrypt_prepare_setflags(struct inode *inode, unsigned int oldflags, unsigned int flags) { struct fscrypt_info *ci; + struct key *key; struct fscrypt_master_key *mk; int err; @@ -153,13 +158,14 @@ int fscrypt_prepare_setflags(struct inode *inode, ci = inode->i_crypt_info; if (ci->ci_policy.version != FSCRYPT_POLICY_V2) return -EINVAL; - mk = ci->ci_master_key->payload.data[0]; - down_read(&mk->mk_secret_sem); + key = ci->ci_master_key; + mk = key->payload.data[0]; + down_read(&key->sem); if (is_master_key_secret_present(&mk->mk_secret)) err = fscrypt_derive_dirhash_key(ci, mk); else err = -ENOKEY; - up_read(&mk->mk_secret_sem); + up_read(&key->sem); return err; } return 0; @@ -325,7 +331,7 @@ const char *fscrypt_get_symlink(struct inode *inode, const void *caddr, * Try to set up the symlink's encryption key, but we can continue * regardless of whether the key is available or not. */ - err = fscrypt_get_encryption_info(inode); + err = fscrypt_get_encryption_info(inode, false); if (err) return ERR_PTR(err); has_key = fscrypt_has_encryption_key(inode); diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c index 1f52e841143f..c492deaed9d6 100644 --- a/fs/crypto/keyring.c +++ b/fs/crypto/keyring.c @@ -347,7 +347,6 @@ static int add_new_master_key(struct fscrypt_master_key_secret *secret, mk->mk_spec = *mk_spec; move_master_key_secret(&mk->mk_secret, secret); - init_rwsem(&mk->mk_secret_sem); refcount_set(&mk->mk_refcount, 1); /* secret is present */ INIT_LIST_HEAD(&mk->mk_decrypted_inodes); @@ -427,11 +426,8 @@ static int add_existing_master_key(struct fscrypt_master_key *mk, } /* Re-add the secret if needed. */ - if (rekey) { - down_write(&mk->mk_secret_sem); + if (rekey) move_master_key_secret(&mk->mk_secret, secret); - up_write(&mk->mk_secret_sem); - } return 0; } @@ -1005,10 +1001,8 @@ static int do_remove_key(struct file *filp, void __user *_uarg, bool all_users) /* No user claims remaining. Go ahead and wipe the secret. */ dead = false; if (is_master_key_secret_present(&mk->mk_secret)) { - down_write(&mk->mk_secret_sem); wipe_master_key_secret(&mk->mk_secret); dead = refcount_dec_and_test(&mk->mk_refcount); - up_write(&mk->mk_secret_sem); } up_write(&key->sem); if (dead) { diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c index f46c939f4109..163dba6c0c3f 100644 --- a/fs/crypto/keysetup.c +++ b/fs/crypto/keysetup.c @@ -376,11 +376,11 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci, * Find the master key, then set up the inode's actual encryption key. * * If the master key is found in the filesystem-level keyring, then the - * corresponding 'struct key' is returned in *master_key_ret with - * ->mk_secret_sem read-locked. This is needed to ensure that only one task - * links the fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race - * to create an fscrypt_info for the same inode), and to synchronize the master - * key being removed with a new inode starting to use it. + * corresponding 'struct key' is returned in *master_key_ret with its semaphore + * read-locked. This is needed to ensure that only one task links the + * fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race to create + * an fscrypt_info for the same inode), and to synchronize the master key being + * removed with a new inode starting to use it. */ static int setup_file_encryption_key(struct fscrypt_info *ci, bool need_dirhash_key, @@ -429,7 +429,7 @@ static int setup_file_encryption_key(struct fscrypt_info *ci, } mk = key->payload.data[0]; - down_read(&mk->mk_secret_sem); + down_read(&key->sem); /* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */ if (!is_master_key_secret_present(&mk->mk_secret)) { @@ -476,7 +476,7 @@ static int setup_file_encryption_key(struct fscrypt_info *ci, return 0; out_release_key: - up_read(&mk->mk_secret_sem); + up_read(&key->sem); key_put(key); return err; } @@ -579,9 +579,7 @@ fscrypt_setup_encryption_info(struct inode *inode, res = 0; out: if (master_key) { - struct fscrypt_master_key *mk = master_key->payload.data[0]; - - up_read(&mk->mk_secret_sem); + up_read(&master_key->sem); key_put(master_key); } put_crypt_info(crypt_info); @@ -591,6 +589,11 @@ fscrypt_setup_encryption_info(struct inode *inode, /** * fscrypt_get_encryption_info() - set up an inode's encryption key * @inode: the inode to set up the key for. Must be encrypted. + * @allow_unsupported: if %true, treat an unsupported encryption policy (or + * unrecognized encryption context) the same way as the key + * being unavailable, instead of returning an error. Use + * %false unless the operation being performed is needed in + * order for files (or directories) to be deleted. * * Set up ->i_crypt_info, if it hasn't already been done. * @@ -601,7 +604,7 @@ fscrypt_setup_encryption_info(struct inode *inode, * encryption key is unavailable. (Use fscrypt_has_encryption_key() to * distinguish these cases.) Also can return another -errno code. */ -int fscrypt_get_encryption_info(struct inode *inode) +int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported) { int res; union fscrypt_context ctx; @@ -612,29 +615,38 @@ int fscrypt_get_encryption_info(struct inode *inode) res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); if (res < 0) { + if (res == -ERANGE && allow_unsupported) + return 0; fscrypt_warn(inode, "Error %d getting encryption context", res); return res; } res = fscrypt_policy_from_context(&policy, &ctx, res); if (res) { + if (allow_unsupported) + return 0; fscrypt_warn(inode, "Unrecognized or corrupt encryption context"); return res; } - if (!fscrypt_supported_policy(&policy, inode)) + if (!fscrypt_supported_policy(&policy, inode)) { + if (allow_unsupported) + return 0; return -EINVAL; + } res = fscrypt_setup_encryption_info(inode, &policy, fscrypt_context_nonce(&ctx), IS_CASEFOLDED(inode) && S_ISDIR(inode->i_mode)); + + if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */ + res = 0; if (res == -ENOKEY) res = 0; return res; } -EXPORT_SYMBOL(fscrypt_get_encryption_info); /** * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory @@ -755,7 +767,7 @@ int fscrypt_drop_inode(struct inode *inode) return 0; /* - * Note: since we aren't holding ->mk_secret_sem, the result here can + * Note: since we aren't holding the key semaphore, the result here can * immediately become outdated. But there's no correctness problem with * unnecessarily evicting. Nor is there a correctness problem with not * evicting while iput() is racing with the key being removed, since diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index faa0f21daa68..a51cef6bd27f 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -590,7 +590,7 @@ EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_nonce); int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) { union fscrypt_policy parent_policy, child_policy; - int err; + int err, err1, err2; /* No restrictions on file types which are never encrypted */ if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) && @@ -620,19 +620,25 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) * In any case, if an unexpected error occurs, fall back to "forbidden". */ - err = fscrypt_get_encryption_info(parent); + err = fscrypt_get_encryption_info(parent, true); if (err) return 0; - err = fscrypt_get_encryption_info(child); + err = fscrypt_get_encryption_info(child, true); if (err) return 0; - err = fscrypt_get_policy(parent, &parent_policy); - if (err) - return 0; + err1 = fscrypt_get_policy(parent, &parent_policy); + err2 = fscrypt_get_policy(child, &child_policy); - err = fscrypt_get_policy(child, &child_policy); - if (err) + /* + * Allow the case where the parent and child both have an unrecognized + * encryption policy, so that files with an unrecognized encryption + * policy can be deleted. + */ + if (err1 == -EINVAL && err2 == -EINVAL) + return 1; + + if (err1 || err2) return 0; return fscrypt_policies_equal(&parent_policy, &child_policy); diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c index 430d479c2eab..dafde07c5a7f 100644 --- a/fs/ext4/dir.c +++ b/fs/ext4/dir.c @@ -139,11 +139,9 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx) struct buffer_head *bh = NULL; struct fscrypt_str fstr = FSTR_INIT(NULL, 0); - if (IS_ENCRYPTED(inode)) { - err = fscrypt_get_encryption_info(inode); - if (err) - return err; - } + err = fscrypt_prepare_readdir(inode); + if (err) + return err; if (is_dx_dir(inode)) { err = ext4_dx_readdir(file, ctx); @@ -640,13 +638,6 @@ static int ext4_dx_readdir(struct file *file, struct dir_context *ctx) return 0; } -static int ext4_dir_open(struct inode * inode, struct file * filp) -{ - if (IS_ENCRYPTED(inode)) - return fscrypt_get_encryption_info(inode) ? -EACCES : 0; - return 0; -} - static int ext4_release_dir(struct inode *inode, struct file *filp) { if (filp->private_data) @@ -688,6 +679,5 @@ const struct file_operations ext4_dir_operations = { .compat_ioctl = ext4_compat_ioctl, #endif .fsync = ext4_sync_file, - .open = ext4_dir_open, .release = ext4_release_dir, }; diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index f603fb3efdae..74bb39c93655 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -647,13 +647,7 @@ static struct stats dx_show_leaf(struct inode *dir, name = de->name; len = de->name_len; - if (IS_ENCRYPTED(dir)) - res = fscrypt_get_encryption_info(dir); - if (res) { - printk(KERN_WARNING "Error setting up" - " fname crypto: %d\n", res); - } - if (!fscrypt_has_encryption_key(dir)) { + if (!IS_ENCRYPTED(dir)) { /* Directory is not encrypted */ ext4fs_dirhash(dir, de->name, de->name_len, &h); @@ -1036,7 +1030,7 @@ static int htree_dirblock_to_tree(struct file *dir_file, csum ? NULL : dir)); /* Check if the directory is encrypted */ if (IS_ENCRYPTED(dir)) { - err = fscrypt_get_encryption_info(dir); + err = fscrypt_prepare_readdir(dir); if (err < 0) { brelse(bh); return err; diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index 82b58d1f80eb..e6270a867be1 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -1076,7 +1076,7 @@ static int f2fs_readdir(struct file *file, struct dir_context *ctx) int err = 0; if (IS_ENCRYPTED(inode)) { - err = fscrypt_get_encryption_info(inode); + err = fscrypt_prepare_readdir(inode); if (err) goto out; @@ -1135,19 +1135,11 @@ static int f2fs_readdir(struct file *file, struct dir_context *ctx) return err < 0 ? err : 0; } -static int f2fs_dir_open(struct inode *inode, struct file *filp) -{ - if (IS_ENCRYPTED(inode)) - return fscrypt_get_encryption_info(inode) ? -EACCES : 0; - return 0; -} - const struct file_operations f2fs_dir_operations = { .llseek = generic_file_llseek, .read = generic_read_dir, .iterate_shared = f2fs_readdir, .fsync = f2fs_sync_file, - .open = f2fs_dir_open, .unlocked_ioctl = f2fs_ioctl, #ifdef CONFIG_COMPAT .compat_ioctl = f2fs_compat_ioctl, diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c index 0379a785b7f6..7949d7c9aa8c 100644 --- a/fs/ubifs/dir.c +++ b/fs/ubifs/dir.c @@ -515,7 +515,7 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx) return 0; if (encrypted) { - err = fscrypt_get_encryption_info(dir); + err = fscrypt_prepare_readdir(dir); if (err) return err; @@ -1620,14 +1620,6 @@ int ubifs_getattr(const struct path *path, struct kstat *stat, return 0; } -static int ubifs_dir_open(struct inode *dir, struct file *file) -{ - if (IS_ENCRYPTED(dir)) - return fscrypt_get_encryption_info(dir) ? -EACCES : 0; - - return 0; -} - const struct inode_operations ubifs_dir_inode_operations = { .lookup = ubifs_lookup, .create = ubifs_create, @@ -1654,7 +1646,6 @@ const struct file_operations ubifs_dir_operations = { .iterate_shared = ubifs_readdir, .fsync = ubifs_fsync, .unlocked_ioctl = ubifs_ioctl, - .open = ubifs_dir_open, #ifdef CONFIG_COMPAT .compat_ioctl = ubifs_compat_ioctl, #endif diff --git a/fs/verity/enable.c b/fs/verity/enable.c index 5ab3bbec8108..f7e997a01ad0 100644 --- a/fs/verity/enable.c +++ b/fs/verity/enable.c @@ -1,6 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 /* - * fs/verity/enable.c: ioctl to enable verity on a file + * Ioctl to enable verity on a file * * Copyright 2019 Google LLC */ @@ -398,9 +398,9 @@ int fsverity_ioctl_enable(struct file *filp, const void __user *uarg) * Some pages of the file may have been evicted from pagecache after * being used in the Merkle tree construction, then read into pagecache * again by another process reading from the file concurrently. Since - * these pages didn't undergo verification against the file measurement - * which fs-verity now claims to be enforcing, we have to wipe the - * pagecache to ensure that all future reads are verified. + * these pages didn't undergo verification against the file digest which + * fs-verity now claims to be enforcing, we have to wipe the pagecache + * to ensure that all future reads are verified. */ filemap_write_and_wait(inode->i_mapping); invalidate_inode_pages2(inode->i_mapping); diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h index e96d99d5145e..96f7b332f54f 100644 --- a/fs/verity/fsverity_private.h +++ b/fs/verity/fsverity_private.h @@ -67,52 +67,22 @@ struct merkle_tree_params { * When a verity file is first opened, an instance of this struct is allocated * and stored in ->i_verity_info; it remains until the inode is evicted. It * caches information about the Merkle tree that's needed to efficiently verify - * data read from the file. It also caches the file measurement. The Merkle - * tree pages themselves are not cached here, but the filesystem may cache them. + * data read from the file. It also caches the file digest. The Merkle tree + * pages themselves are not cached here, but the filesystem may cache them. */ struct fsverity_info { struct merkle_tree_params tree_params; u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE]; - u8 measurement[FS_VERITY_MAX_DIGEST_SIZE]; + u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE]; const struct inode *inode; }; -/* - * Merkle tree properties. The file measurement is the hash of this structure - * excluding the signature and with the sig_size field set to 0. - */ -struct fsverity_descriptor { - __u8 version; /* must be 1 */ - __u8 hash_algorithm; /* Merkle tree hash algorithm */ - __u8 log_blocksize; /* log2 of size of data and tree blocks */ - __u8 salt_size; /* size of salt in bytes; 0 if none */ - __le32 sig_size; /* size of signature in bytes; 0 if none */ - __le64 data_size; /* size of file the Merkle tree is built over */ - __u8 root_hash[64]; /* Merkle tree root hash */ - __u8 salt[32]; /* salt prepended to each hashed block */ - __u8 __reserved[144]; /* must be 0's */ - __u8 signature[]; /* optional PKCS#7 signature */ -}; - /* Arbitrary limit to bound the kmalloc() size. Can be changed. */ #define FS_VERITY_MAX_DESCRIPTOR_SIZE 16384 #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ sizeof(struct fsverity_descriptor)) -/* - * Format in which verity file measurements are signed. This is the same as - * 'struct fsverity_digest', except here some magic bytes are prepended to - * provide some context about what is being signed in case the same key is used - * for non-fsverity purposes, and here the fields have fixed endianness. - */ -struct fsverity_signed_digest { - char magic[8]; /* must be "FSVerity" */ - __le16 digest_algorithm; - __le16 digest_size; - __u8 digest[]; -}; - /* hash_algs.c */ extern struct fsverity_hash_alg fsverity_hash_algs[]; diff --git a/fs/verity/hash_algs.c b/fs/verity/hash_algs.c index c37e186ebeb6..71d0fccb6d4c 100644 --- a/fs/verity/hash_algs.c +++ b/fs/verity/hash_algs.c @@ -1,6 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 /* - * fs/verity/hash_algs.c: fs-verity hash algorithms + * fs-verity hash algorithms * * Copyright 2019 Google LLC */ diff --git a/fs/verity/init.c b/fs/verity/init.c index 94c104e00861..c98b7016f446 100644 --- a/fs/verity/init.c +++ b/fs/verity/init.c @@ -1,6 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 /* - * fs/verity/init.c: fs-verity module initialization and logging + * fs-verity module initialization and logging * * Copyright 2019 Google LLC */ diff --git a/fs/verity/measure.c b/fs/verity/measure.c index df409a5682ed..f0d7b30c62db 100644 --- a/fs/verity/measure.c +++ b/fs/verity/measure.c @@ -1,6 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 /* - * fs/verity/measure.c: ioctl to get a verity file's measurement + * Ioctl to get a verity file's digest * * Copyright 2019 Google LLC */ @@ -10,12 +10,12 @@ #include /** - * fsverity_ioctl_measure() - get a verity file's measurement - * @filp: file to get measurement of + * fsverity_ioctl_measure() - get a verity file's digest + * @filp: file to get digest of * @_uarg: user pointer to fsverity_digest * - * Retrieve the file measurement that the kernel is enforcing for reads from a - * verity file. See the "FS_IOC_MEASURE_VERITY" section of + * Retrieve the file digest that the kernel is enforcing for reads from a verity + * file. See the "FS_IOC_MEASURE_VERITY" section of * Documentation/filesystems/fsverity.rst for the documentation. * * Return: 0 on success, -errno on failure @@ -51,7 +51,7 @@ int fsverity_ioctl_measure(struct file *filp, void __user *_uarg) if (copy_to_user(uarg, &arg, sizeof(arg))) return -EFAULT; - if (copy_to_user(uarg->digest, vi->measurement, hash_alg->digest_size)) + if (copy_to_user(uarg->digest, vi->file_digest, hash_alg->digest_size)) return -EFAULT; return 0; diff --git a/fs/verity/open.c b/fs/verity/open.c index bfe0280c14e4..228d0eca3e2e 100644 --- a/fs/verity/open.c +++ b/fs/verity/open.c @@ -1,6 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 /* - * fs/verity/open.c: opening fs-verity files + * Opening fs-verity files * * Copyright 2019 Google LLC */ @@ -124,18 +124,18 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, } /* - * Compute the file measurement by hashing the fsverity_descriptor excluding the + * Compute the file digest by hashing the fsverity_descriptor excluding the * signature and with the sig_size field set to 0. */ -static int compute_file_measurement(struct fsverity_hash_alg *hash_alg, - struct fsverity_descriptor *desc, - u8 *measurement) +static int compute_file_digest(struct fsverity_hash_alg *hash_alg, + struct fsverity_descriptor *desc, + u8 *file_digest) { __le32 sig_size = desc->sig_size; int err; desc->sig_size = 0; - err = fsverity_hash_buffer(hash_alg, desc, sizeof(*desc), measurement); + err = fsverity_hash_buffer(hash_alg, desc, sizeof(*desc), file_digest); desc->sig_size = sig_size; return err; @@ -199,15 +199,15 @@ struct fsverity_info *fsverity_create_info(const struct inode *inode, memcpy(vi->root_hash, desc->root_hash, vi->tree_params.digest_size); - err = compute_file_measurement(vi->tree_params.hash_alg, desc, - vi->measurement); + err = compute_file_digest(vi->tree_params.hash_alg, desc, + vi->file_digest); if (err) { - fsverity_err(inode, "Error %d computing file measurement", err); + fsverity_err(inode, "Error %d computing file digest", err); goto out; } - pr_debug("Computed file measurement: %s:%*phN\n", + pr_debug("Computed file digest: %s:%*phN\n", vi->tree_params.hash_alg->name, - vi->tree_params.digest_size, vi->measurement); + vi->tree_params.digest_size, vi->file_digest); err = fsverity_verify_signature(vi, desc, desc_size); out: @@ -354,7 +354,7 @@ int __init fsverity_init_info_cache(void) { fsverity_info_cachep = KMEM_CACHE_USERCOPY(fsverity_info, SLAB_RECLAIM_ACCOUNT, - measurement); + file_digest); if (!fsverity_info_cachep) return -ENOMEM; return 0; diff --git a/fs/verity/signature.c b/fs/verity/signature.c index b14ed96387ec..012468eda2a7 100644 --- a/fs/verity/signature.c +++ b/fs/verity/signature.c @@ -1,6 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 /* - * fs/verity/signature.c: verification of builtin signatures + * Verification of builtin signatures * * Copyright 2019 Google LLC */ @@ -32,8 +32,8 @@ static struct key *fsverity_keyring; * @desc: the file's fsverity_descriptor * @desc_size: size of @desc * - * If the file's fs-verity descriptor includes a signature of the file - * measurement, verify it against the certificates in the fs-verity keyring. + * If the file's fs-verity descriptor includes a signature of the file digest, + * verify it against the certificates in the fs-verity keyring. * * Return: 0 on success (signature valid or not required); -errno on failure */ @@ -44,7 +44,7 @@ int fsverity_verify_signature(const struct fsverity_info *vi, const struct inode *inode = vi->inode; const struct fsverity_hash_alg *hash_alg = vi->tree_params.hash_alg; const u32 sig_size = le32_to_cpu(desc->sig_size); - struct fsverity_signed_digest *d; + struct fsverity_formatted_digest *d; int err; if (sig_size == 0) { @@ -67,7 +67,7 @@ int fsverity_verify_signature(const struct fsverity_info *vi, memcpy(d->magic, "FSVerity", 8); d->digest_algorithm = cpu_to_le16(hash_alg - fsverity_hash_algs); d->digest_size = cpu_to_le16(hash_alg->digest_size); - memcpy(d->digest, vi->measurement, hash_alg->digest_size); + memcpy(d->digest, vi->file_digest, hash_alg->digest_size); err = verify_pkcs7_signature(d, sizeof(*d) + hash_alg->digest_size, desc->signature, sig_size, @@ -90,8 +90,8 @@ int fsverity_verify_signature(const struct fsverity_info *vi, return err; } - pr_debug("Valid signature for file measurement %s:%*phN\n", - hash_alg->name, hash_alg->digest_size, vi->measurement); + pr_debug("Valid signature for file digest %s:%*phN\n", + hash_alg->name, hash_alg->digest_size, vi->file_digest); return 0; } diff --git a/fs/verity/verify.c b/fs/verity/verify.c index a8b68c6f663d..0adb970f4e73 100644 --- a/fs/verity/verify.c +++ b/fs/verity/verify.c @@ -1,6 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 /* - * fs/verity/verify.c: data verification functions, i.e. hooks for ->readpages() + * Data verification functions, i.e. hooks for ->readpages() * * Copyright 2019 Google LLC */ diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index 9c5d1ff1c1ba..1a5e3d8dc0b5 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -75,7 +75,7 @@ struct fscrypt_operations { static inline struct fscrypt_info *fscrypt_get_info(const struct inode *inode) { /* - * Pairs with the cmpxchg_release() in fscrypt_get_encryption_info(). + * Pairs with the cmpxchg_release() in fscrypt_setup_encryption_info(). * I.e., another task may publish ->i_crypt_info concurrently, executing * a RELEASE barrier. We need to use smp_load_acquire() here to safely * ACQUIRE the memory the other task published. @@ -200,7 +200,6 @@ int fscrypt_ioctl_remove_key_all_users(struct file *filp, void __user *arg); int fscrypt_ioctl_get_key_status(struct file *filp, void __user *arg); /* keysetup.c */ -int fscrypt_get_encryption_info(struct inode *inode); int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode, bool *encrypt_ret); void fscrypt_put_encryption_info(struct inode *inode); @@ -242,6 +241,8 @@ int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry, unsigned int flags); int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry, struct fscrypt_name *fname); +int __fscrypt_prepare_readdir(struct inode *dir); +int __fscrypt_prepare_setattr(struct dentry *dentry, struct iattr *attr); int fscrypt_prepare_setflags(struct inode *inode, unsigned int oldflags, unsigned int flags); int fscrypt_prepare_symlink(struct inode *dir, const char *target, @@ -406,10 +407,6 @@ static inline int fscrypt_ioctl_get_key_status(struct file *filp, } /* keysetup.c */ -static inline int fscrypt_get_encryption_info(struct inode *inode) -{ - return -EOPNOTSUPP; -} static inline int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode, @@ -537,6 +534,17 @@ static inline int __fscrypt_prepare_lookup(struct inode *dir, return -EOPNOTSUPP; } +static inline int __fscrypt_prepare_readdir(struct inode *dir) +{ + return -EOPNOTSUPP; +} + +static inline int __fscrypt_prepare_setattr(struct dentry *dentry, + struct iattr *attr) +{ + return -EOPNOTSUPP; +} + static inline int fscrypt_prepare_setflags(struct inode *inode, unsigned int oldflags, unsigned int flags) @@ -708,32 +716,6 @@ static inline bool fscrypt_has_encryption_key(const struct inode *inode) return fscrypt_get_info(inode) != NULL; } -/** - * fscrypt_require_key() - require an inode's encryption key - * @inode: the inode we need the key for - * - * If the inode is encrypted, set up its encryption key if not already done. - * Then require that the key be present and return -ENOKEY otherwise. - * - * No locks are needed, and the key will live as long as the struct inode --- so - * it won't go away from under you. - * - * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code - * if a problem occurred while setting up the encryption key. - */ -static inline int fscrypt_require_key(struct inode *inode) -{ - if (IS_ENCRYPTED(inode)) { - int err = fscrypt_get_encryption_info(inode); - - if (err) - return err; - if (!fscrypt_has_encryption_key(inode)) - return -ENOKEY; - } - return 0; -} - /** * fscrypt_prepare_link() - prepare to link an inode into a possibly-encrypted * directory @@ -743,8 +725,7 @@ static inline int fscrypt_require_key(struct inode *inode) * * A new link can only be added to an encrypted directory if the directory's * encryption key is available --- since otherwise we'd have no way to encrypt - * the filename. Therefore, we first set up the directory's encryption key (if - * not already done) and return an error if it's unavailable. + * the filename. * * We also verify that the link will not violate the constraint that all files * in an encrypted directory tree use the same encryption policy. @@ -805,8 +786,9 @@ static inline int fscrypt_prepare_rename(struct inode *old_dir, * * Prepare for ->lookup() in a directory which may be encrypted by determining * the name that will actually be used to search the directory on-disk. If the - * directory's encryption key is available, then the lookup is assumed to be by - * plaintext name; otherwise, it is assumed to be by no-key name. + * directory's encryption policy is supported by this kernel and its encryption + * key is available, then the lookup is assumed to be by plaintext name; + * otherwise, it is assumed to be by no-key name. * * This will set DCACHE_NOKEY_NAME on the dentry if the lookup is by no-key * name. In this case the filesystem must assign the dentry a dentry_operations @@ -832,6 +814,26 @@ static inline int fscrypt_prepare_lookup(struct inode *dir, return 0; } +/** + * fscrypt_prepare_readdir() - prepare to read a possibly-encrypted directory + * @dir: the directory inode + * + * If the directory is encrypted and it doesn't already have its encryption key + * set up, try to set it up so that the filenames will be listed in plaintext + * form rather than in no-key form. + * + * Return: 0 on success; -errno on error. Note that the encryption key being + * unavailable is not considered an error. It is also not an error if + * the encryption policy is unsupported by this kernel; that is treated + * like the key being unavailable, so that files can still be deleted. + */ +static inline int fscrypt_prepare_readdir(struct inode *dir) +{ + if (IS_ENCRYPTED(dir)) + return __fscrypt_prepare_readdir(dir); + return 0; +} + /** * fscrypt_prepare_setattr() - prepare to change a possibly-encrypted inode's * attributes @@ -853,8 +855,8 @@ static inline int fscrypt_prepare_lookup(struct inode *dir, static inline int fscrypt_prepare_setattr(struct dentry *dentry, struct iattr *attr) { - if (attr->ia_valid & ATTR_SIZE) - return fscrypt_require_key(d_inode(dentry)); + if (IS_ENCRYPTED(d_inode(dentry))) + return __fscrypt_prepare_setattr(dentry, attr); return 0; } diff --git a/include/uapi/linux/fsverity.h b/include/uapi/linux/fsverity.h index da0daf6c193b..33f44156f8ea 100644 --- a/include/uapi/linux/fsverity.h +++ b/include/uapi/linux/fsverity.h @@ -34,6 +34,55 @@ struct fsverity_digest { __u8 digest[]; }; +/* + * Struct containing a file's Merkle tree properties. The fs-verity file digest + * is the hash of this struct. A userspace program needs this struct only if it + * needs to compute fs-verity file digests itself, e.g. in order to sign files. + * It isn't needed just to enable fs-verity on a file. + * + * Note: when computing the file digest, 'sig_size' and 'signature' must be left + * zero and empty, respectively. These fields are present only because some + * filesystems reuse this struct as part of their on-disk format. + */ +struct fsverity_descriptor { + __u8 version; /* must be 1 */ + __u8 hash_algorithm; /* Merkle tree hash algorithm */ + __u8 log_blocksize; /* log2 of size of data and tree blocks */ + __u8 salt_size; /* size of salt in bytes; 0 if none */ +#ifdef __KERNEL__ + __le32 sig_size; +#else + __le32 __reserved_0x04; /* must be 0 */ +#endif + __le64 data_size; /* size of file the Merkle tree is built over */ + __u8 root_hash[64]; /* Merkle tree root hash */ + __u8 salt[32]; /* salt prepended to each hashed block */ + __u8 __reserved[144]; /* must be 0's */ +#ifdef __KERNEL__ + __u8 signature[]; +#endif +}; + +/* + * Format in which fs-verity file digests are signed in built-in signatures. + * This is the same as 'struct fsverity_digest', except here some magic bytes + * are prepended to provide some context about what is being signed in case the + * same key is used for non-fsverity purposes, and here the fields have fixed + * endianness. + * + * This struct is specific to the built-in signature verification support, which + * is optional. fs-verity users may also verify signatures in userspace, in + * which case userspace is responsible for deciding on what bytes are signed. + * This struct may still be used, but it doesn't have to be. For example, + * userspace could instead use a string like "sha256:$digest_as_hex_string". + */ +struct fsverity_formatted_digest { + char magic[8]; /* must be "FSVerity" */ + __le16 digest_algorithm; + __le16 digest_size; + __u8 digest[]; +}; + #define FS_IOC_ENABLE_VERITY _IOW('f', 133, struct fsverity_enable_arg) #define FS_IOC_MEASURE_VERITY _IOWR('f', 134, struct fsverity_digest)