fscrypt: use FSCRYPT_ prefix for uapi constants

Prefix all filesystem encryption UAPI constants except the ioctl numbers
with "FSCRYPT_" rather than with "FS_".  This namespaces the constants
more appropriately and makes it clear that they are related specifically
to the filesystem encryption feature, and to the 'fscrypt_*' structures.
With some of the old names like "FS_POLICY_FLAGS_VALID", it was not
immediately clear that the constant had anything to do with encryption.

This is also useful because we'll be adding more encryption-related
constants, e.g. for the policy version, and we'd otherwise have to
choose whether to use unclear names like FS_POLICY_V1 or inconsistent
names like FS_ENCRYPTION_POLICY_V1.

For source compatibility with existing userspace programs, keep the old
names defined as aliases to the new names.

Finally, as long as new names are being defined anyway, I skipped
defining new names for the fscrypt mode numbers that aren't actually
used: INVALID (0), AES_256_GCM (2), AES_256_CBC (3), SPECK128_256_XTS
(7), and SPECK128_256_CTS (8).

Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers 2019-08-04 19:35:44 -07:00
parent 7af0ab0d3a
commit 2336d0deb2
2 changed files with 62 additions and 43 deletions

View File

@ -225,9 +225,10 @@ a little endian number, except that:
is encrypted with AES-256 where the AES-256 key is the SHA-256 hash
of the file's data encryption key.
- In the "direct key" configuration (FS_POLICY_FLAG_DIRECT_KEY set in
the fscrypt_policy), the file's nonce is also appended to the IV.
Currently this is only allowed with the Adiantum encryption mode.
- In the "direct key" configuration (FSCRYPT_POLICY_FLAG_DIRECT_KEY
set in the fscrypt_policy), the file's nonce is also appended to the
IV. Currently this is only allowed with the Adiantum encryption
mode.
Filenames encryption
--------------------
@ -274,14 +275,14 @@ empty directory or verifies that a directory or regular file already
has the specified encryption policy. It takes in a pointer to a
:c:type:`struct fscrypt_policy`, defined as follows::
#define FS_KEY_DESCRIPTOR_SIZE 8
#define FSCRYPT_KEY_DESCRIPTOR_SIZE 8
struct fscrypt_policy {
__u8 version;
__u8 contents_encryption_mode;
__u8 filenames_encryption_mode;
__u8 flags;
__u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
__u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
};
This structure must be initialized as follows:
@ -289,19 +290,18 @@ This structure must be initialized as follows:
- ``version`` must be 0.
- ``contents_encryption_mode`` and ``filenames_encryption_mode`` must
be set to constants from ``<linux/fs.h>`` which identify the
encryption modes to use. If unsure, use
FS_ENCRYPTION_MODE_AES_256_XTS (1) for ``contents_encryption_mode``
and FS_ENCRYPTION_MODE_AES_256_CTS (4) for
``filenames_encryption_mode``.
be set to constants from ``<linux/fscrypt.h>`` which identify the
encryption modes to use. If unsure, use FSCRYPT_MODE_AES_256_XTS
(1) for ``contents_encryption_mode`` and FSCRYPT_MODE_AES_256_CTS
(4) for ``filenames_encryption_mode``.
- ``flags`` must contain a value from ``<linux/fs.h>`` which
- ``flags`` must contain a value from ``<linux/fscrypt.h>`` which
identifies the amount of NUL-padding to use when encrypting
filenames. If unsure, use FS_POLICY_FLAGS_PAD_32 (0x3).
In addition, if the chosen encryption modes are both
FS_ENCRYPTION_MODE_ADIANTUM, this can contain
FS_POLICY_FLAG_DIRECT_KEY to specify that the master key should be
used directly, without key derivation.
filenames. If unsure, use FSCRYPT_POLICY_FLAGS_PAD_32 (0x3). In
addition, if the chosen encryption modes are both
FSCRYPT_MODE_ADIANTUM, this can contain
FSCRYPT_POLICY_FLAG_DIRECT_KEY to specify that the master key should
be used directly, without key derivation.
- ``master_key_descriptor`` specifies how to find the master key in
the keyring; see `Adding keys`_. It is up to userspace to choose a
@ -401,11 +401,11 @@ followed by the 16-character lower case hex representation of the
``master_key_descriptor`` that was set in the encryption policy. The
key payload must conform to the following structure::
#define FS_MAX_KEY_SIZE 64
#define FSCRYPT_MAX_KEY_SIZE 64
struct fscrypt_key {
u32 mode;
u8 raw[FS_MAX_KEY_SIZE];
u8 raw[FSCRYPT_MAX_KEY_SIZE];
u32 size;
};
@ -574,7 +574,7 @@ much confusion if an encryption policy were to be added to or removed
from anything other than an empty directory.) The struct is defined
as follows::
#define FS_KEY_DESCRIPTOR_SIZE 8
#define FSCRYPT_KEY_DESCRIPTOR_SIZE 8
#define FS_KEY_DERIVATION_NONCE_SIZE 16
struct fscrypt_context {
@ -582,7 +582,7 @@ as follows::
u8 contents_encryption_mode;
u8 filenames_encryption_mode;
u8 flags;
u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
};

View File

@ -10,35 +10,30 @@
#include <linux/types.h>
#define FS_KEY_DESCRIPTOR_SIZE 8
#define FSCRYPT_KEY_DESCRIPTOR_SIZE 8
/* Encryption policy flags */
#define FS_POLICY_FLAGS_PAD_4 0x00
#define FS_POLICY_FLAGS_PAD_8 0x01
#define FS_POLICY_FLAGS_PAD_16 0x02
#define FS_POLICY_FLAGS_PAD_32 0x03
#define FS_POLICY_FLAGS_PAD_MASK 0x03
#define FS_POLICY_FLAG_DIRECT_KEY 0x04 /* use master key directly */
#define FS_POLICY_FLAGS_VALID 0x07
#define FSCRYPT_POLICY_FLAGS_PAD_4 0x00
#define FSCRYPT_POLICY_FLAGS_PAD_8 0x01
#define FSCRYPT_POLICY_FLAGS_PAD_16 0x02
#define FSCRYPT_POLICY_FLAGS_PAD_32 0x03
#define FSCRYPT_POLICY_FLAGS_PAD_MASK 0x03
#define FSCRYPT_POLICY_FLAG_DIRECT_KEY 0x04 /* use master key directly */
#define FSCRYPT_POLICY_FLAGS_VALID 0x07
/* Encryption algorithms */
#define FS_ENCRYPTION_MODE_INVALID 0
#define FS_ENCRYPTION_MODE_AES_256_XTS 1
#define FS_ENCRYPTION_MODE_AES_256_GCM 2
#define FS_ENCRYPTION_MODE_AES_256_CBC 3
#define FS_ENCRYPTION_MODE_AES_256_CTS 4
#define FS_ENCRYPTION_MODE_AES_128_CBC 5
#define FS_ENCRYPTION_MODE_AES_128_CTS 6
#define FS_ENCRYPTION_MODE_SPECK128_256_XTS 7 /* Removed, do not use. */
#define FS_ENCRYPTION_MODE_SPECK128_256_CTS 8 /* Removed, do not use. */
#define FS_ENCRYPTION_MODE_ADIANTUM 9
#define FSCRYPT_MODE_AES_256_XTS 1
#define FSCRYPT_MODE_AES_256_CTS 4
#define FSCRYPT_MODE_AES_128_CBC 5
#define FSCRYPT_MODE_AES_128_CTS 6
#define FSCRYPT_MODE_ADIANTUM 9
struct fscrypt_policy {
__u8 version;
__u8 contents_encryption_mode;
__u8 filenames_encryption_mode;
__u8 flags;
__u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
__u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
};
#define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy)
@ -46,16 +41,40 @@ struct fscrypt_policy {
#define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy)
/* Parameters for passing an encryption key into the kernel keyring */
#define FS_KEY_DESC_PREFIX "fscrypt:"
#define FS_KEY_DESC_PREFIX_SIZE 8
#define FSCRYPT_KEY_DESC_PREFIX "fscrypt:"
#define FSCRYPT_KEY_DESC_PREFIX_SIZE 8
/* Structure that userspace passes to the kernel keyring */
#define FS_MAX_KEY_SIZE 64
#define FSCRYPT_MAX_KEY_SIZE 64
struct fscrypt_key {
__u32 mode;
__u8 raw[FS_MAX_KEY_SIZE];
__u8 raw[FSCRYPT_MAX_KEY_SIZE];
__u32 size;
};
/**********************************************************************/
/* old names; don't add anything new here! */
#define FS_KEY_DESCRIPTOR_SIZE FSCRYPT_KEY_DESCRIPTOR_SIZE
#define FS_POLICY_FLAGS_PAD_4 FSCRYPT_POLICY_FLAGS_PAD_4
#define FS_POLICY_FLAGS_PAD_8 FSCRYPT_POLICY_FLAGS_PAD_8
#define FS_POLICY_FLAGS_PAD_16 FSCRYPT_POLICY_FLAGS_PAD_16
#define FS_POLICY_FLAGS_PAD_32 FSCRYPT_POLICY_FLAGS_PAD_32
#define FS_POLICY_FLAGS_PAD_MASK FSCRYPT_POLICY_FLAGS_PAD_MASK
#define FS_POLICY_FLAG_DIRECT_KEY FSCRYPT_POLICY_FLAG_DIRECT_KEY
#define FS_POLICY_FLAGS_VALID FSCRYPT_POLICY_FLAGS_VALID
#define FS_ENCRYPTION_MODE_INVALID 0 /* never used */
#define FS_ENCRYPTION_MODE_AES_256_XTS FSCRYPT_MODE_AES_256_XTS
#define FS_ENCRYPTION_MODE_AES_256_GCM 2 /* never used */
#define FS_ENCRYPTION_MODE_AES_256_CBC 3 /* never used */
#define FS_ENCRYPTION_MODE_AES_256_CTS FSCRYPT_MODE_AES_256_CTS
#define FS_ENCRYPTION_MODE_AES_128_CBC FSCRYPT_MODE_AES_128_CBC
#define FS_ENCRYPTION_MODE_AES_128_CTS FSCRYPT_MODE_AES_128_CTS
#define FS_ENCRYPTION_MODE_SPECK128_256_XTS 7 /* removed */
#define FS_ENCRYPTION_MODE_SPECK128_256_CTS 8 /* removed */
#define FS_ENCRYPTION_MODE_ADIANTUM FSCRYPT_MODE_ADIANTUM
#define FS_KEY_DESC_PREFIX FSCRYPT_KEY_DESC_PREFIX
#define FS_KEY_DESC_PREFIX_SIZE FSCRYPT_KEY_DESC_PREFIX_SIZE
#define FS_MAX_KEY_SIZE FSCRYPT_MAX_KEY_SIZE
#endif /* _UAPI_LINUX_FSCRYPT_H */