wireguard-linux/fs/crypto/policy.c, branch jd/unified-crypt-queue

fscrypt: add FS_IOC_GET_ENCRYPTION_NONCE ioctl

2020-03-20T04:56:54Z

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 Signed-off-by: Eric Biggers

fscrypt: don't allow v1 policies with casefolding

2020-01-22T22:47:15Z

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 [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

fscrypt: move fscrypt_valid_enc_modes() to policy.c

2019-12-31T16:33:50Z

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

fscrypt: check for appropriate use of DIRECT_KEY flag earlier

2019-12-31T16:33:50Z

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

fscrypt: split up fscrypt_supported_policy() by policy version

2019-12-31T16:33:50Z

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

fscrypt: add support for IV_INO_LBLK_64 policies

2019-11-06T20:34:36Z

Inline encryption hardware compliant with the UFS v2.1 standard or with the upcoming version of the eMMC standard has the following properties: (1) Per I/O request, the encryption key is specified by a previously loaded keyslot. There might be only a small number of keyslots. (2) Per I/O request, the starting IV is specified by a 64-bit "data unit number" (DUN). IV bits 64-127 are assumed to be 0. The hardware automatically increments the DUN for each "data unit" of configurable size in the request, e.g. for each filesystem block. Property (1) makes it inefficient to use the traditional fscrypt per-file keys. Property (2) precludes the use of the existing DIRECT_KEY fscrypt policy flag, which needs at least 192 IV bits. Therefore, add a new fscrypt policy flag IV_INO_LBLK_64 which causes the encryption to modified as follows: - The encryption keys are derived from the master key, encryption mode number, and filesystem UUID. - The IVs are chosen as (inode_number << 32) | file_logical_block_num. For filenames encryption, file_logical_block_num is 0. Since the file nonces aren't used in the key derivation, many files may share the same encryption key. This is much more efficient on the target hardware. Including the inode number in the IVs and mixing the filesystem UUID into the keys ensures that data in different files is nevertheless still encrypted differently. Additionally, limiting the inode and block numbers to 32 bits and placing the block number in the low bits maintains compatibility with the 64-bit DUN convention (property (2) above). Since this scheme assumes that inode numbers are stable (which may preclude filesystem shrinking) and that inode and file logical block numbers are at most 32-bit, IV_INO_LBLK_64 will only be allowed on filesystems that meet these constraints. These are acceptable limitations for the cases where this format would actually be used. Note that IV_INO_LBLK_64 is an on-disk format, not an implementation. This patch just adds support for it using the existing filesystem layer encryption. A later patch will add support for inline encryption. Reviewed-by: Paul Crowley Co-developed-by: Satya Tangirala Signed-off-by: Satya Tangirala Signed-off-by: Eric Biggers

fscrypt: require that key be added when setting a v2 encryption policy

2019-08-13T02:18:50Z

By looking up the master keys in a filesystem-level keyring rather than in the calling processes' key hierarchy, it becomes possible for a user to set an encryption policy which refers to some key they don't actually know, then encrypt their files using that key. Cryptographically this isn't much of a problem, but the semantics of this would be a bit weird. Thus, enforce that a v2 encryption policy can only be set if the user has previously added the key, or has capable(CAP_FOWNER). We tolerate that this problem will continue to exist for v1 encryption policies, however; there is no way around that. Reviewed-by: Theodore Ts'o Signed-off-by: Eric Biggers

fscrypt: v2 encryption policy support

2019-08-13T02:18:50Z

Add a new fscrypt policy version, "v2". It has the following changes from the original policy version, which we call "v1" (*): - Master keys (the user-provided encryption keys) are only ever used as input to HKDF-SHA512. This is more flexible and less error-prone, and it avoids the quirks and limitations of the AES-128-ECB based KDF. Three classes of cryptographically isolated subkeys are defined: - Per-file keys, like used in v1 policies except for the new KDF. - Per-mode keys. These implement the semantics of the DIRECT_KEY flag, which for v1 policies made the master key be used directly. These are also planned to be used for inline encryption when support for it is added. - Key identifiers (see below). - Each master key is identified by a 16-byte master_key_identifier, which is derived from the key itself using HKDF-SHA512. This prevents users from associating the wrong key with an encrypted file or directory. This was easily possible with v1 policies, which identified the key by an arbitrary 8-byte master_key_descriptor. - The key must be provided in the filesystem-level keyring, not in a process-subscribed keyring. The following UAPI additions are made: - The existing ioctl FS_IOC_SET_ENCRYPTION_POLICY can now be passed a fscrypt_policy_v2 to set a v2 encryption policy. It's disambiguated from fscrypt_policy/fscrypt_policy_v1 by the version code prefix. - A new ioctl FS_IOC_GET_ENCRYPTION_POLICY_EX is added. It allows getting the v1 or v2 encryption policy of an encrypted file or directory. The existing FS_IOC_GET_ENCRYPTION_POLICY ioctl could not be used because it did not have a way for userspace to indicate which policy structure is expected. The new ioctl includes a size field, so it is extensible to future fscrypt policy versions. - The ioctls FS_IOC_ADD_ENCRYPTION_KEY, FS_IOC_REMOVE_ENCRYPTION_KEY, and FS_IOC_GET_ENCRYPTION_KEY_STATUS now support managing keys for v2 encryption policies. Such keys are kept logically separate from keys for v1 encryption policies, and are identified by 'identifier' rather than by 'descriptor'. The 'identifier' need not be provided when adding a key, since the kernel will calculate it anyway. This patch temporarily keeps adding/removing v2 policy keys behind the same permission check done for adding/removing v1 policy keys: capable(CAP_SYS_ADMIN). However, the next patch will carefully take advantage of the cryptographically secure master_key_identifier to allow non-root users to add/remove v2 policy keys, thus providing a full replacement for v1 policies. (*) Actually, in the API fscrypt_policy::version is 0 while on-disk fscrypt_context::format is 1. But I believe it makes the most sense to advance both to '2' to have them be in sync, and to consider the numbering to start at 1 except for the API quirk. Reviewed-by: Paul Crowley Reviewed-by: Theodore Ts'o Signed-off-by: Eric Biggers

fscrypt: use FSCRYPT_* definitions, not FS_*

2019-08-13T02:05:19Z

Update fs/crypto/ to use the new names for the UAPI constants rather than the old names, then make the old definitions conditional on !__KERNEL__. Reviewed-by: Theodore Ts'o Signed-off-by: Eric Biggers

fscrypt: don't set policy for a dead directory

2019-05-28T17:48:23Z

The directory may have been removed when entering fscrypt_ioctl_set_policy(). If so, the empty_dir() check will return error for ext4 file system. ext4_rmdir() sets i_size = 0, then ext4_empty_dir() reports an error because 'inode->i_size < EXT4_DIR_REC_LEN(1) + EXT4_DIR_REC_LEN(2)'. If the fs is mounted with errors=panic, it will trigger a panic issue. Add the check IS_DEADDIR() to fix this problem. Fixes: 9bd8212f981e ("ext4 crypto: add encryption policy and password salt support") Cc: # v4.1+ Signed-off-by: Hongjie Fang Signed-off-by: Eric Biggers