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2020-09-28fscrypt: export fscrypt_d_revalidate()Eric Biggers
Dentries that represent no-key names must have a dentry_operations that includes fscrypt_d_revalidate(). Currently, this is handled by fscrypt_prepare_lookup() installing fscrypt_d_ops. However, ceph support for encryption (https://lore.kernel.org/r/20200914191707.380444-1-jlayton@kernel.org) can't use fscrypt_d_ops, since ceph already has its own dentry_operations. Similarly, ext4 and f2fs support for directories that are both encrypted and casefolded (https://lore.kernel.org/r/20200923010151.69506-1-drosen@google.com) can't use fscrypt_d_ops either, since casefolding requires some dentry operations too. To satisfy both users, we need to move the responsibility of installing the dentry_operations to filesystems. In preparation for this, export fscrypt_d_revalidate() and give it a !CONFIG_FS_ENCRYPTION stub. Reviewed-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/20200924054721.187797-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-23fscrypt: rename DCACHE_ENCRYPTED_NAME to DCACHE_NOKEY_NAMEEric Biggers
Originally we used the term "encrypted name" or "ciphertext name" to mean the encoded filename that is shown when an encrypted directory is listed without its key. But these terms are ambiguous since they also mean the filename stored on-disk. "Encrypted name" is especially ambiguous since it could also be understood to mean "this filename is encrypted on-disk", similar to "encrypted file". So we've started calling these encoded names "no-key names" instead. Therefore, rename DCACHE_ENCRYPTED_NAME to DCACHE_NOKEY_NAME to avoid confusion about what this flag means. Link: https://lore.kernel.org/r/20200924042624.98439-3-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-23fscrypt: don't call no-key names "ciphertext names"Eric Biggers
Currently we're using the term "ciphertext name" ambiguously because it can mean either the actual ciphertext filename, or the encoded filename that is shown when an encrypted directory is listed without its key. The latter we're now usually calling the "no-key name"; and while it's derived from the ciphertext name, it's not the same thing. To avoid this ambiguity, rename fscrypt_name::is_ciphertext_name to fscrypt_name::is_nokey_name, and update comments that say "ciphertext name" (or "encrypted name") to say "no-key name" instead when warranted. Link: https://lore.kernel.org/r/20200924042624.98439-2-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-22fscrypt: use sha256() instead of open codingEric Biggers
Now that there's a library function that calculates the SHA-256 digest of a buffer in one step, use it instead of sha256_init() + sha256_update() + sha256_final(). Link: https://lore.kernel.org/r/20200917045341.324996-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-22fscrypt: make fscrypt_set_test_dummy_encryption() take a 'const char *'Eric Biggers
fscrypt_set_test_dummy_encryption() requires that the optional argument to the test_dummy_encryption mount option be specified as a substring_t. That doesn't work well with filesystems that use the new mount API, since the new way of parsing mount options doesn't use substring_t. Make it take the argument as a 'const char *' instead. Instead of moving the match_strdup() into the callers in ext4 and f2fs, make them just use arg->from directly. Since the pattern is "test_dummy_encryption=%s", the argument will be null-terminated. Acked-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/20200917041136.178600-14-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-22fscrypt: handle test_dummy_encryption in more logical wayEric Biggers
The behavior of the test_dummy_encryption mount option is that when a new file (or directory or symlink) is created in an unencrypted directory, it's automatically encrypted using a dummy encryption policy. That's it; in particular, the encryption (or lack thereof) of existing files (or directories or symlinks) doesn't change. Unfortunately the implementation of test_dummy_encryption is a bit weird and confusing. When test_dummy_encryption is enabled and a file is being created in an unencrypted directory, we set up an encryption key (->i_crypt_info) for the directory. This isn't actually used to do any encryption, however, since the directory is still unencrypted! Instead, ->i_crypt_info is only used for inheriting the encryption policy. One consequence of this is that the filesystem ends up providing a "dummy context" (policy + nonce) instead of a "dummy policy". In commit ed318a6cc0b6 ("fscrypt: support test_dummy_encryption=v2"), I mistakenly thought this was required. However, actually the nonce only ends up being used to derive a key that is never used. Another consequence of this implementation is that it allows for 'inode->i_crypt_info != NULL && !IS_ENCRYPTED(inode)', which is an edge case that can be forgotten about. For example, currently FS_IOC_GET_ENCRYPTION_POLICY on an unencrypted directory may return the dummy encryption policy when the filesystem is mounted with test_dummy_encryption. That seems like the wrong thing to do, since again, the directory itself is not actually encrypted. Therefore, switch to a more logical and maintainable implementation where the dummy encryption policy inheritance is done without setting up keys for unencrypted directories. This involves: - Adding a function fscrypt_policy_to_inherit() which returns the encryption policy to inherit from a directory. This can be a real policy, a dummy policy, or no policy. - Replacing struct fscrypt_dummy_context, ->get_dummy_context(), etc. with struct fscrypt_dummy_policy, ->get_dummy_policy(), etc. - Making fscrypt_fname_encrypted_size() take an fscrypt_policy instead of an inode. Acked-by: Jaegeuk Kim <jaegeuk@kernel.org> Acked-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/20200917041136.178600-13-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-22fscrypt: move fscrypt_prepare_symlink() out-of-lineEric Biggers
In preparation for moving the logic for "get the encryption policy inherited by new files in this directory" to a single place, make fscrypt_prepare_symlink() a regular function rather than an inline function that wraps __fscrypt_prepare_symlink(). This way, the new function fscrypt_policy_to_inherit() won't need to be exported to filesystems. Acked-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/20200917041136.178600-12-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-22fscrypt: make "#define fscrypt_policy" user-onlyEric Biggers
The fscrypt UAPI header defines fscrypt_policy to fscrypt_policy_v1, for source compatibility with old userspace programs. Internally, the kernel doesn't want that compatibility definition. Instead, fscrypt_private.h #undefs it and re-defines it to a union. That works for now. However, in order to add fscrypt_operations::get_dummy_policy(), we'll need to forward declare 'union fscrypt_policy' in include/linux/fscrypt.h. That would cause build errors because "fscrypt_policy" is used in ioctl numbers. To avoid this, modify the UAPI header to make the fscrypt_policy compatibility definition conditional on !__KERNEL__, and make the ioctls use fscrypt_policy_v1 instead of fscrypt_policy. Note that this doesn't change the actual ioctl numbers. Acked-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/20200917041136.178600-11-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-22fscrypt: stop pretending that key setup is nofs-safeEric Biggers
fscrypt_get_encryption_info() has never actually been safe to call in a context that needs GFP_NOFS, since it calls crypto_alloc_skcipher(). crypto_alloc_skcipher() isn't GFP_NOFS-safe, even if called under memalloc_nofs_save(). This is because it may load kernel modules, and also because it internally takes crypto_alg_sem. Other tasks can do GFP_KERNEL allocations while holding crypto_alg_sem for write. The use of fscrypt_init_mutex isn't GFP_NOFS-safe either. So, stop pretending that fscrypt_get_encryption_info() is nofs-safe. I.e., when it allocates memory, just use GFP_KERNEL instead of GFP_NOFS. Note, another reason to do this is that GFP_NOFS is deprecated in favor of using memalloc_nofs_save() in the proper places. Acked-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/20200917041136.178600-10-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-22fscrypt: require that fscrypt_encrypt_symlink() already has keyEric Biggers
Now that all filesystems have been converted to use fscrypt_prepare_new_inode(), the encryption key for new symlink inodes is now already set up whenever we try to encrypt the symlink target. Enforce this rather than try to set up the key again when it may be too late to do so safely. Acked-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/20200917041136.178600-9-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-22fscrypt: remove fscrypt_inherit_context()Eric Biggers
Now that all filesystems have been converted to use fscrypt_prepare_new_inode() and fscrypt_set_context(), fscrypt_inherit_context() is no longer used. Remove it. Acked-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/20200917041136.178600-8-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-22fscrypt: adjust logging for in-creation inodesEric Biggers
Now that a fscrypt_info may be set up for inodes that are currently being created and haven't yet had an inode number assigned, avoid logging confusing messages about "inode 0". Acked-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/20200917041136.178600-7-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-22fscrypt: add fscrypt_prepare_new_inode() and fscrypt_set_context()Eric Biggers
fscrypt_get_encryption_info() is intended to be GFP_NOFS-safe. But actually it isn't, since it uses functions like crypto_alloc_skcipher() which aren't GFP_NOFS-safe, even when called under memalloc_nofs_save(). Therefore it can deadlock when called from a context that needs GFP_NOFS, e.g. during an ext4 transaction or between f2fs_lock_op() and f2fs_unlock_op(). This happens when creating a new encrypted file. We can't fix this by just not setting up the key for new inodes right away, since new symlinks need their key to encrypt the symlink target. So we need to set up the new inode's key before starting the transaction. But just calling fscrypt_get_encryption_info() earlier doesn't work, since it assumes the encryption context is already set, and the encryption context can't be set until the transaction. The recently proposed fscrypt support for the ceph filesystem (https://lkml.kernel.org/linux-fscrypt/20200821182813.52570-1-jlayton@kernel.org/T/#u) will have this same ordering problem too, since ceph will need to encrypt new symlinks before setting their encryption context. Finally, f2fs can deadlock when the filesystem is mounted with '-o test_dummy_encryption' and a new file is created in an existing unencrypted directory. Similarly, this is caused by holding too many locks when calling fscrypt_get_encryption_info(). To solve all these problems, add new helper functions: - fscrypt_prepare_new_inode() sets up a new inode's encryption key (fscrypt_info), using the parent directory's encryption policy and a new random nonce. It neither reads nor writes the encryption context. - fscrypt_set_context() persists the encryption context of a new inode, using the information from the fscrypt_info already in memory. This replaces fscrypt_inherit_context(). Temporarily keep fscrypt_inherit_context() around until all filesystems have been converted to use fscrypt_set_context(). Acked-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/20200917041136.178600-2-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-07fscrypt: restrict IV_INO_LBLK_32 to ino_bits <= 32Eric Biggers
When an encryption policy has the IV_INO_LBLK_32 flag set, the IV generation method involves hashing the inode number. This is different from fscrypt's other IV generation methods, where the inode number is either not used at all or is included directly in the IVs. Therefore, in principle IV_INO_LBLK_32 can work with any length inode number. However, currently fscrypt gets the inode number from inode::i_ino, which is 'unsigned long'. So currently the implementation limit is actually 32 bits (like IV_INO_LBLK_64), since longer inode numbers will have been truncated by the VFS on 32-bit platforms. Fix fscrypt_supported_v2_policy() to enforce the correct limit. This doesn't actually matter currently, since only ext4 and f2fs support IV_INO_LBLK_32, and they both only support 32-bit inode numbers. But we might as well fix it in case it matters in the future. Ideally inode::i_ino would instead be made 64-bit, but for now it's not needed. (Note, this limit does *not* prevent filesystems with 64-bit inode numbers from adding fscrypt support, since IV_INO_LBLK_* support is optional and is useful only on certain hardware.) Fixes: e3b1078bedd3 ("fscrypt: add support for IV_INO_LBLK_32 policies") Reported-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/20200824203841.1707847-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-09-07fscrypt: drop unused inode argument from fscrypt_fname_alloc_bufferJeff Layton
Signed-off-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/20200810142139.487631-1-jlayton@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-08-07mm, treewide: rename kzfree() to kfree_sensitive()Waiman Long
As said by Linus: A symmetric naming is only helpful if it implies symmetries in use. Otherwise it's actively misleading. In "kzalloc()", the z is meaningful and an important part of what the caller wants. In "kzfree()", the z is actively detrimental, because maybe in the future we really _might_ want to use that "memfill(0xdeadbeef)" or something. The "zero" part of the interface isn't even _relevant_. The main reason that kzfree() exists is to clear sensitive information that should not be leaked to other future users of the same memory objects. Rename kzfree() to kfree_sensitive() to follow the example of the recently added kvfree_sensitive() and make the intention of the API more explicit. In addition, memzero_explicit() is used to clear the memory to make sure that it won't get optimized away by the compiler. The renaming is done by using the command sequence: git grep -w --name-only kzfree |\ xargs sed -i 's/kzfree/kfree_sensitive/' followed by some editing of the kfree_sensitive() kerneldoc and adding a kzfree backward compatibility macro in slab.h. [akpm@linux-foundation.org: fs/crypto/inline_crypt.c needs linux/slab.h] [akpm@linux-foundation.org: fix fs/crypto/inline_crypt.c some more] Suggested-by: Joe Perches <joe@perches.com> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: David Howells <dhowells@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> Cc: James Morris <jmorris@namei.org> Cc: "Serge E. Hallyn" <serge@hallyn.com> Cc: Joe Perches <joe@perches.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: David Rientjes <rientjes@google.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: "Jason A . Donenfeld" <Jason@zx2c4.com> Link: http://lkml.kernel.org/r/20200616154311.12314-3-longman@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-07-30fscrypt: don't load ->i_crypt_info before it's known to be validEric Biggers
In fscrypt_set_bio_crypt_ctx(), ->i_crypt_info isn't known to be non-NULL until we check fscrypt_inode_uses_inline_crypto(). So, load ->i_crypt_info after the check rather than before. This makes no difference currently, but it prevents people from introducing bugs where the pointer is dereferenced when it may be NULL. Suggested-by: Dave Chinner <david@fromorbit.com> Cc: Satya Tangirala <satyat@google.com> Link: https://lore.kernel.org/r/20200727174158.121456-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-07-21fscrypt: use smp_load_acquire() for ->i_crypt_infoEric Biggers
Normally smp_store_release() or cmpxchg_release() is paired with smp_load_acquire(). Sometimes smp_load_acquire() can be replaced with the more lightweight READ_ONCE(). However, for this to be safe, all the published memory must only be accessed in a way that involves the pointer itself. This may not be the case if allocating the object also involves initializing a static or global variable, for example. fscrypt_info includes various sub-objects which are internal to and are allocated by other kernel subsystems such as keyrings and crypto. So by using READ_ONCE() for ->i_crypt_info, we're relying on internal implementation details of these other kernel subsystems. Remove this fragile assumption by using smp_load_acquire() instead. (Note: I haven't seen any real-world problems here. This change is just fixing the code to be guaranteed correct and less fragile.) Fixes: e37a784d8b6a ("fscrypt: use READ_ONCE() to access ->i_crypt_info") Link: https://lore.kernel.org/r/20200721225920.114347-5-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-07-21fscrypt: use smp_load_acquire() for ->s_master_keysEric Biggers
Normally smp_store_release() or cmpxchg_release() is paired with smp_load_acquire(). Sometimes smp_load_acquire() can be replaced with the more lightweight READ_ONCE(). However, for this to be safe, all the published memory must only be accessed in a way that involves the pointer itself. This may not be the case if allocating the object also involves initializing a static or global variable, for example. super_block::s_master_keys is a keyring, which is internal to and is allocated by the keyrings subsystem. By using READ_ONCE() for it, we're relying on internal implementation details of the keyrings subsystem. Remove this fragile assumption by using smp_load_acquire() instead. (Note: I haven't seen any real-world problems here. This change is just fixing the code to be guaranteed correct and less fragile.) Fixes: 22d94f493bfb ("fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl") Link: https://lore.kernel.org/r/20200721225920.114347-4-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-07-21fscrypt: use smp_load_acquire() for fscrypt_prepared_keyEric Biggers
Normally smp_store_release() or cmpxchg_release() is paired with smp_load_acquire(). Sometimes smp_load_acquire() can be replaced with the more lightweight READ_ONCE(). However, for this to be safe, all the published memory must only be accessed in a way that involves the pointer itself. This may not be the case if allocating the object also involves initializing a static or global variable, for example. fscrypt_prepared_key includes a pointer to a crypto_skcipher object, which is internal to and is allocated by the crypto subsystem. By using READ_ONCE() for it, we're relying on internal implementation details of the crypto subsystem. Remove this fragile assumption by using smp_load_acquire() instead. (Note: I haven't seen any real-world problems here. This change is just fixing the code to be guaranteed correct and less fragile.) Fixes: 5fee36095cda ("fscrypt: add inline encryption support") Cc: Satya Tangirala <satyat@google.com> Link: https://lore.kernel.org/r/20200721225920.114347-3-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-07-21fscrypt: switch fscrypt_do_sha256() to use the SHA-256 libraryEric Biggers
fscrypt_do_sha256() is only used for hashing encrypted filenames to create no-key tokens, which isn't performance-critical. Therefore a C implementation of SHA-256 is sufficient. Also, the logic to create no-key tokens is always potentially needed. This differs from fscrypt's other dependencies on crypto API algorithms, which are conditionally needed depending on what encryption policies userspace is using. Therefore, for fscrypt there isn't much benefit to allowing SHA-256 to be a loadable module. So, make fscrypt_do_sha256() use the SHA-256 library instead of the crypto_shash API. This is much simpler, since it avoids having to implement one-time-init (which is hard to do correctly, and in fact was implemented incorrectly) and handle failures to allocate the crypto_shash object. Fixes: edc440e3d27f ("fscrypt: improve format of no-key names") Cc: Daniel Rosenberg <drosen@google.com> Link: https://lore.kernel.org/r/20200721225920.114347-2-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-07-21fscrypt: restrict IV_INO_LBLK_* to AES-256-XTSEric Biggers
IV_INO_LBLK_* exist only because of hardware limitations, and currently the only known use case for them involves AES-256-XTS. Therefore, for now only allow them in combination with AES-256-XTS. This way we don't have to worry about them being combined with other encryption modes. (To be clear, combining IV_INO_LBLK_* with other encryption modes *should* work just fine. It's just not being tested, so we can't be 100% sure it works. So with no known use case, it's best to disallow it for now, just like we don't allow other weird combinations like AES-256-XTS contents encryption with Adiantum filenames encryption.) This can be relaxed later if a use case for other combinations arises. Fixes: b103fb7653ff ("fscrypt: add support for IV_INO_LBLK_64 policies") Fixes: e3b1078bedd3 ("fscrypt: add support for IV_INO_LBLK_32 policies") Link: https://lore.kernel.org/r/20200721181012.39308-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-07-20fscrypt: rename FS_KEY_DERIVATION_NONCE_SIZEEric Biggers
The name "FS_KEY_DERIVATION_NONCE_SIZE" is a bit outdated since due to the addition of FSCRYPT_POLICY_FLAG_DIRECT_KEY, the file nonce may now be used as a tweak instead of for key derivation. Also, we're now prefixing the fscrypt constants with "FSCRYPT_" instead of "FS_". Therefore, rename this constant to FSCRYPT_FILE_NONCE_SIZE. Link: https://lore.kernel.org/r/20200708215722.147154-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-07-20fscrypt: add comments that describe the HKDF info stringsEric Biggers
Each HKDF context byte is associated with a specific format of the remaining part of the application-specific info string. Add comments so that it's easier to keep track of what these all are. Link: https://lore.kernel.org/r/20200708215529.146890-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-07-08fscrypt: add inline encryption supportSatya Tangirala
Add support for inline encryption to fs/crypto/. With "inline encryption", the block layer handles the decryption/encryption as part of the bio, instead of the filesystem doing the crypto itself via Linux's crypto API. This model is needed in order to take advantage of the inline encryption hardware present on most modern mobile SoCs. To use inline encryption, the filesystem needs to be mounted with '-o inlinecrypt'. Blk-crypto will then be used instead of the traditional filesystem-layer crypto whenever possible to encrypt the contents of any encrypted files in that filesystem. Fscrypt still provides the key and IV to use, and the actual ciphertext on-disk is still the same; therefore it's testable using the existing fscrypt ciphertext verification tests. Note that since blk-crypto has a fallback to Linux's crypto API, and also supports all the encryption modes currently supported by fscrypt, this feature is usable and testable even without actual inline encryption hardware. Per-filesystem changes will be needed to set encryption contexts when submitting bios and to implement the 'inlinecrypt' mount option. This patch just adds the common code. Signed-off-by: Satya Tangirala <satyat@google.com> Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org> Reviewed-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Theodore Ts'o <tytso@mit.edu> Link: https://lore.kernel.org/r/20200702015607.1215430-3-satyat@google.com Co-developed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-06-01Merge tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscryptLinus Torvalds
Pull fscrypt updates from Eric Biggers: - Add the IV_INO_LBLK_32 encryption policy flag which modifies the encryption to be optimized for eMMC inline encryption hardware. - Make the test_dummy_encryption mount option for ext4 and f2fs support v2 encryption policies. - Fix kerneldoc warnings and some coding style inconsistencies. * tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt: fscrypt: add support for IV_INO_LBLK_32 policies fscrypt: make test_dummy_encryption use v2 by default fscrypt: support test_dummy_encryption=v2 fscrypt: add fscrypt_add_test_dummy_key() linux/parser.h: add include guards fscrypt: remove unnecessary extern keywords fscrypt: name all function parameters fscrypt: fix all kerneldoc warnings
2020-05-19fscrypt: add support for IV_INO_LBLK_32 policiesEric Biggers
The eMMC inline crypto standard will only specify 32 DUN bits (a.k.a. IV bits), unlike UFS's 64. IV_INO_LBLK_64 is therefore not applicable, but an encryption format which uses one key per policy and permits the moving of encrypted file contents (as f2fs's garbage collector requires) is still desirable. To support such hardware, add a new encryption format IV_INO_LBLK_32 that makes the best use of the 32 bits: the IV is set to 'SipHash-2-4(inode_number) + file_logical_block_number mod 2^32', where the SipHash key is derived from the fscrypt master key. We hash only the inode number and not also the block number, because we need to maintain contiguity of DUNs to merge bios. Unlike with IV_INO_LBLK_64, with this format IV reuse is possible; this is unavoidable given the size of the DUN. This means this format should only be used where the requirements of the first paragraph apply. However, the hash spreads out the IVs in the whole usable range, and the use of a keyed hash makes it difficult for an attacker to determine which files use which IVs. Besides the above differences, this flag works like IV_INO_LBLK_64 in that on ext4 it is only allowed if the stable_inodes feature has been enabled to prevent inode numbers and the filesystem UUID from changing. Link: https://lore.kernel.org/r/20200515204141.251098-1-ebiggers@kernel.org Reviewed-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Paul Crowley <paulcrowley@google.com> Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-05-18fscrypt: make test_dummy_encryption use v2 by defaultEric Biggers
Since v1 encryption policies are deprecated, make test_dummy_encryption test v2 policies by default. Note that this causes ext4/023 and ext4/028 to start failing due to known bugs in those tests (see previous commit). Link: https://lore.kernel.org/r/20200512233251.118314-5-ebiggers@kernel.org Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org> Reviewed-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-05-18fscrypt: support test_dummy_encryption=v2Eric Biggers
v1 encryption policies are deprecated in favor of v2, and some new features (e.g. encryption+casefolding) are only being added for v2. Therefore, the "test_dummy_encryption" mount option (which is used for encryption I/O testing with xfstests) needs to support v2 policies. To do this, extend its syntax to be "test_dummy_encryption=v1" or "test_dummy_encryption=v2". The existing "test_dummy_encryption" (no argument) also continues to be accepted, to specify the default setting -- currently v1, but the next patch changes it to v2. To cleanly support both v1 and v2 while also making it easy to support specifying other encryption settings in the future (say, accepting "$contents_mode:$filenames_mode:v2"), make ext4 and f2fs maintain a pointer to the dummy fscrypt_context rather than using mount flags. To avoid concurrency issues, don't allow test_dummy_encryption to be set or changed during a remount. (The former restriction is new, but xfstests doesn't run into it, so no one should notice.) Tested with 'gce-xfstests -c {ext4,f2fs}/encrypt -g auto'. On ext4, there are two regressions, both of which are test bugs: ext4/023 and ext4/028 fail because they set an xattr and expect it to be stored inline, but the increase in size of the fscrypt_context from 24 to 40 bytes causes this xattr to be spilled into an external block. Link: https://lore.kernel.org/r/20200512233251.118314-4-ebiggers@kernel.org Acked-by: Jaegeuk Kim <jaegeuk@kernel.org> Reviewed-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-05-15fscrypt: add fscrypt_add_test_dummy_key()Eric Biggers
Currently, the test_dummy_encryption mount option (which is used for encryption I/O testing with xfstests) uses v1 encryption policies, and it relies on userspace inserting a test key into the session keyring. We need test_dummy_encryption to support v2 encryption policies too. Requiring userspace to add the test key doesn't work well with v2 policies, since v2 policies only support the filesystem keyring (not the session keyring), and keys in the filesystem keyring are lost when the filesystem is unmounted. Hooking all test code that unmounts and re-mounts the filesystem would be difficult. Instead, let's make the filesystem automatically add the test key to its keyring when test_dummy_encryption is enabled. That puts the responsibility for choosing the test key on the kernel. We could just hard-code a key. But out of paranoia, let's first try using a per-boot random key, to prevent this code from being misused. A per-boot key will work as long as no one expects dummy-encrypted files to remain accessible after a reboot. (gce-xfstests doesn't.) Therefore, this patch adds a function fscrypt_add_test_dummy_key() which implements the above. The next patch will use it. Link: https://lore.kernel.org/r/20200512233251.118314-3-ebiggers@kernel.org Reviewed-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org> Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-05-12fscrypt: remove unnecessary extern keywordsEric Biggers
Remove the unnecessary 'extern' keywords from function declarations. This makes it so that we don't have a mix of both styles, so it won't be ambiguous what to use in new fscrypt patches. This also makes the code shorter and matches the 'checkpatch --strict' expectation. Link: https://lore.kernel.org/r/20200511191358.53096-4-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-05-12fscrypt: fix all kerneldoc warningsEric Biggers
Fix all kerneldoc warnings in fs/crypto/ and include/linux/fscrypt.h. Most of these were due to missing documentation for function parameters. Detected with: scripts/kernel-doc -v -none fs/crypto/*.{c,h} include/linux/fscrypt.h This cleanup makes it possible to check new patches for kerneldoc warnings without having to filter out all the existing ones. For consistency, also adjust some function "brief descriptions" to include the parentheses and to wrap at 80 characters. (The latter matches the checkpatch expectation.) Link: https://lore.kernel.org/r/20200511191358.53096-2-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-05-08fscrypt: use crypto_shash_tfm_digest()Eric Biggers
Instead of manually allocating a 'struct shash_desc' on the stack and calling crypto_shash_digest(), switch to using the new helper function crypto_shash_tfm_digest() which does this for us. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2020-03-31Merge tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscryptLinus Torvalds
Pull fscrypt updates from Eric Biggers: "Add an ioctl FS_IOC_GET_ENCRYPTION_NONCE which retrieves a file's encryption nonce. This makes it easier to write automated tests which verify that fscrypt is doing the encryption correctly" * tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt: ubifs: wire up FS_IOC_GET_ENCRYPTION_NONCE f2fs: wire up FS_IOC_GET_ENCRYPTION_NONCE ext4: wire up FS_IOC_GET_ENCRYPTION_NONCE fscrypt: add FS_IOC_GET_ENCRYPTION_NONCE ioctl
2020-03-19fscrypt: add FS_IOC_GET_ENCRYPTION_NONCE ioctlEric Biggers
Add an ioctl FS_IOC_GET_ENCRYPTION_NONCE which retrieves the nonce from an encrypted file or directory. The nonce is the 16-byte random value stored in the inode's encryption xattr. It is normally used together with the master key to derive the inode's actual encryption key. The nonces are needed by automated tests that verify the correctness of the ciphertext on-disk. Except for the IV_INO_LBLK_64 case, there's no way to replicate a file's ciphertext without knowing that file's nonce. The nonces aren't secret, and the existing ciphertext verification tests in xfstests retrieve them from disk using debugfs or dump.f2fs. But in environments that lack these debugging tools, getting the nonces by manually parsing the filesystem structure would be very hard. To make this important type of testing much easier, let's just add an ioctl that retrieves the nonce. Link: https://lore.kernel.org/r/20200314205052.93294-2-ebiggers@kernel.org Reviewed-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-03-07fscrypt: don't evict dirty inodes after removing keyEric Biggers
After FS_IOC_REMOVE_ENCRYPTION_KEY removes a key, it syncs the filesystem and tries to get and put all inodes that were unlocked by the key so that unused inodes get evicted via fscrypt_drop_inode(). Normally, the inodes are all clean due to the sync. However, after the filesystem is sync'ed, userspace can modify and close one of the files. (Userspace is *supposed* to close the files before removing the key. But it doesn't always happen, and the kernel can't assume it.) This causes the inode to be dirtied and have i_count == 0. Then, fscrypt_drop_inode() failed to consider this case and indicated that the inode can be dropped, causing the write to be lost. On f2fs, other problems such as a filesystem freeze could occur due to the inode being freed while still on f2fs's dirty inode list. Fix this bug by making fscrypt_drop_inode() only drop clean inodes. I've written an xfstest which detects this bug on ext4, f2fs, and ubifs. Fixes: b1c0ec3599f4 ("fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl") Cc: <stable@vger.kernel.org> # v5.4+ Link: https://lore.kernel.org/r/20200305084138.653498-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-01-22fscrypt: improve format of no-key namesDaniel Rosenberg
When an encrypted directory is listed without the key, the filesystem must show "no-key names" that uniquely identify directory entries, are at most 255 (NAME_MAX) bytes long, and don't contain '/' or '\0'. Currently, for short names the no-key name is the base64 encoding of the ciphertext filename, while for long names it's the base64 encoding of the ciphertext filename's dirhash and second-to-last 16-byte block. This format has the following problems: - Since it doesn't always include the dirhash, it's incompatible with directories that will use a secret-keyed dirhash over the plaintext filenames. In this case, the dirhash won't be computable from the ciphertext name without the key, so it instead must be retrieved from the directory entry and always included in the no-key name. Casefolded encrypted directories will use this type of dirhash. - It's ambiguous: it's possible to craft two filenames that map to the same no-key name, since the method used to abbreviate long filenames doesn't use a proper cryptographic hash function. Solve both these problems by switching to a new no-key name format that is the base64 encoding of a variable-length structure that contains the dirhash, up to 149 bytes of the ciphertext filename, and (if any bytes remain) the SHA-256 of the remaining bytes of the ciphertext filename. This ensures that each no-key name contains everything needed to find the directory entry again, contains only legal characters, doesn't exceed NAME_MAX, is unambiguous unless there's a SHA-256 collision, and that we only take the performance hit of SHA-256 on very long filenames. Note: this change does *not* address the existing issue where users can modify the 'dirhash' part of a no-key name and the filesystem may still accept the name. Signed-off-by: Daniel Rosenberg <drosen@google.com> [EB: improved comments and commit message, fixed checking return value of base64_decode(), check for SHA-256 error, continue to set disk_name for short names to keep matching simpler, and many other cleanups] Link: https://lore.kernel.org/r/20200120223201.241390-7-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-01-22fscrypt: clarify what is meant by a per-file keyEric Biggers
Now that there's sometimes a second type of per-file key (the dirhash key), clarify some function names, macros, and documentation that specifically deal with per-file *encryption* keys. Link: https://lore.kernel.org/r/20200120223201.241390-4-ebiggers@kernel.org Reviewed-by: Daniel Rosenberg <drosen@google.com> Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-01-22fscrypt: derive dirhash key for casefolded directoriesDaniel Rosenberg
When we allow indexed directories to use both encryption and casefolding, for the dirhash we can't just hash the ciphertext filenames that are stored on-disk (as is done currently) because the dirhash must be case insensitive, but the stored names are case-preserving. Nor can we hash the plaintext names with an unkeyed hash (or a hash keyed with a value stored on-disk like ext4's s_hash_seed), since that would leak information about the names that encryption is meant to protect. Instead, if we can accept a dirhash that's only computable when the fscrypt key is available, we can hash the plaintext names with a keyed hash using a secret key derived from the directory's fscrypt master key. We'll use SipHash-2-4 for this purpose. Prepare for this by deriving a SipHash key for each casefolded encrypted directory. Make sure to handle deriving the key not only when setting up the directory's fscrypt_info, but also in the case where the casefold flag is enabled after the fscrypt_info was already set up. (We could just always derive the key regardless of casefolding, but that would introduce unnecessary overhead for people not using casefolding.) Signed-off-by: Daniel Rosenberg <drosen@google.com> [EB: improved commit message, updated fscrypt.rst, squashed with change that avoids unnecessarily deriving the key, and many other cleanups] Link: https://lore.kernel.org/r/20200120223201.241390-3-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-01-22fscrypt: don't allow v1 policies with casefoldingDaniel Rosenberg
Casefolded encrypted directories will use a new dirhash method that requires a secret key. If the directory uses a v2 encryption policy, it's easy to derive this key from the master key using HKDF. However, v1 encryption policies don't provide a way to derive additional keys. Therefore, don't allow casefolding on directories that use a v1 policy. Specifically, make it so that trying to enable casefolding on a directory that has a v1 policy fails, trying to set a v1 policy on a casefolded directory fails, and trying to open a casefolded directory that has a v1 policy (if one somehow exists on-disk) fails. Signed-off-by: Daniel Rosenberg <drosen@google.com> [EB: improved commit message, updated fscrypt.rst, and other cleanups] Link: https://lore.kernel.org/r/20200120223201.241390-2-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-01-22fscrypt: add "fscrypt_" prefix to fname_encrypt()Eric Biggers
fname_encrypt() is a global function, due to being used in both fname.c and hooks.c. So it should be prefixed with "fscrypt_", like all the other global functions in fs/crypto/. Link: https://lore.kernel.org/r/20200120071736.45915-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-01-22fscrypt: don't print name of busy file when removing keyEric Biggers
When an encryption key can't be fully removed due to file(s) protected by it still being in-use, we shouldn't really print the path to one of these files to the kernel log, since parts of this path are likely to be encrypted on-disk, and (depending on how the system is set up) the confidentiality of this path might be lost by printing it to the log. This is a trade-off: a single file path often doesn't matter at all, especially if it's a directory; the kernel log might still be protected in some way; and I had originally hoped that any "inode(s) still busy" bugs (which are security weaknesses in their own right) would be quickly fixed and that to do so it would be super helpful to always know the file path and not have to run 'find dir -inum $inum' after the fact. But in practice, these bugs can be hard to fix (e.g. due to asynchronous process killing that is difficult to eliminate, for performance reasons), and also not tied to specific files, so knowing a file path doesn't necessarily help. So to be safe, for now let's just show the inode number, not the path. If someone really wants to know a path they can use 'find -inum'. Fixes: b1c0ec3599f4 ("fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl") Cc: <stable@vger.kernel.org> # v5.4+ Link: https://lore.kernel.org/r/20200120060732.390362-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-01-14fscrypt: document gfp_flags for bounce page allocationEric Biggers
Document that fscrypt_encrypt_pagecache_blocks() allocates the bounce page from a mempool, and document what this means for the @gfp_flags argument. Link: https://lore.kernel.org/r/20191231181026.47400-1-ebiggers@kernel.org Reviewed-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-01-14fscrypt: optimize fscrypt_zeroout_range()Eric Biggers
Currently fscrypt_zeroout_range() issues and waits on a bio for each block it writes, which makes it very slow. Optimize it to write up to 16 pages at a time instead. Also add a function comment, and improve reliability by allowing the allocations of the bio and the first ciphertext page to wait on the corresponding mempools. Link: https://lore.kernel.org/r/20191226160813.53182-1-ebiggers@kernel.org Reviewed-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Eric Biggers <ebiggers@google.com>
2019-12-31fscrypt: remove redundant bi_status checkEric Biggers
submit_bio_wait() already returns bi_status translated to an errno. So the additional check of bi_status is redundant and can be removed. Link: https://lore.kernel.org/r/20191209204509.228942-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2019-12-31fscrypt: Allow modular crypto algorithmsHerbert Xu
The commit 643fa9612bf1 ("fscrypt: remove filesystem specific build config option") removed modular support for fs/crypto. This causes the Crypto API to be built-in whenever fscrypt is enabled. This makes it very difficult for me to test modular builds of the Crypto API without disabling fscrypt which is a pain. As fscrypt is still evolving and it's developing new ties with the fs layer, it's hard to build it as a module for now. However, the actual algorithms are not required until a filesystem is mounted. Therefore we can allow them to be built as modules. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Link: https://lore.kernel.org/r/20191227024700.7vrzuux32uyfdgum@gondor.apana.org.au Signed-off-by: Eric Biggers <ebiggers@google.com>
2019-12-31fscrypt: remove fscrypt_is_direct_key_policy()Eric Biggers
fscrypt_is_direct_key_policy() is no longer used, so remove it. Link: https://lore.kernel.org/r/20191209211829.239800-5-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2019-12-31fscrypt: move fscrypt_valid_enc_modes() to policy.cEric Biggers
fscrypt_valid_enc_modes() is only used by policy.c, so move it to there. Also adjust the order of the checks to be more natural, matching the numerical order of the constants and also keeping AES-256 (the recommended default) first in the list. No change in behavior. Link: https://lore.kernel.org/r/20191209211829.239800-4-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2019-12-31fscrypt: check for appropriate use of DIRECT_KEY flag earlierEric Biggers
FSCRYPT_POLICY_FLAG_DIRECT_KEY is currently only allowed with Adiantum encryption. But FS_IOC_SET_ENCRYPTION_POLICY allowed it in combination with other encryption modes, and an error wasn't reported until later when the encrypted directory was actually used. Fix it to report the error earlier by validating the correct use of the DIRECT_KEY flag in fscrypt_supported_policy(), similar to how we validate the IV_INO_LBLK_64 flag. Link: https://lore.kernel.org/r/20191209211829.239800-3-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2019-12-31fscrypt: split up fscrypt_supported_policy() by policy versionEric Biggers
Make fscrypt_supported_policy() call new functions fscrypt_supported_v1_policy() and fscrypt_supported_v2_policy(), to reduce the indentation level and make the code easier to read. Also adjust the function comment to mention that whether the encryption policy is supported can also depend on the inode. No change in behavior. Link: https://lore.kernel.org/r/20191209211829.239800-2-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>