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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>
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Eric Biggers
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@ -225,9 +225,10 @@ a little endian number, except that:
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is encrypted with AES-256 where the AES-256 key is the SHA-256 hash
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of the file's data encryption key.
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- In the "direct key" configuration (FS_POLICY_FLAG_DIRECT_KEY set in
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the fscrypt_policy), the file's nonce is also appended to the IV.
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Currently this is only allowed with the Adiantum encryption mode.
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- In the "direct key" configuration (FSCRYPT_POLICY_FLAG_DIRECT_KEY
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set in the fscrypt_policy), the file's nonce is also appended to the
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IV. Currently this is only allowed with the Adiantum encryption
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mode.
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Filenames encryption
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--------------------
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@ -274,14 +275,14 @@ empty directory or verifies that a directory or regular file already
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has the specified encryption policy. It takes in a pointer to a
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:c:type:`struct fscrypt_policy`, defined as follows::
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#define FS_KEY_DESCRIPTOR_SIZE 8
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#define FSCRYPT_KEY_DESCRIPTOR_SIZE 8
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struct fscrypt_policy {
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__u8 version;
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__u8 contents_encryption_mode;
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__u8 filenames_encryption_mode;
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__u8 flags;
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__u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
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__u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
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};
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This structure must be initialized as follows:
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@ -289,19 +290,18 @@ This structure must be initialized as follows:
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- ``version`` must be 0.
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- ``contents_encryption_mode`` and ``filenames_encryption_mode`` must
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be set to constants from ``<linux/fs.h>`` which identify the
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encryption modes to use. If unsure, use
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FS_ENCRYPTION_MODE_AES_256_XTS (1) for ``contents_encryption_mode``
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and FS_ENCRYPTION_MODE_AES_256_CTS (4) for
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``filenames_encryption_mode``.
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be set to constants from ``<linux/fscrypt.h>`` which identify the
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encryption modes to use. If unsure, use FSCRYPT_MODE_AES_256_XTS
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(1) for ``contents_encryption_mode`` and FSCRYPT_MODE_AES_256_CTS
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(4) for ``filenames_encryption_mode``.
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- ``flags`` must contain a value from ``<linux/fs.h>`` which
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- ``flags`` must contain a value from ``<linux/fscrypt.h>`` which
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identifies the amount of NUL-padding to use when encrypting
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filenames. If unsure, use FS_POLICY_FLAGS_PAD_32 (0x3).
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In addition, if the chosen encryption modes are both
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FS_ENCRYPTION_MODE_ADIANTUM, this can contain
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FS_POLICY_FLAG_DIRECT_KEY to specify that the master key should be
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used directly, without key derivation.
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filenames. If unsure, use FSCRYPT_POLICY_FLAGS_PAD_32 (0x3). In
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addition, if the chosen encryption modes are both
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FSCRYPT_MODE_ADIANTUM, this can contain
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FSCRYPT_POLICY_FLAG_DIRECT_KEY to specify that the master key should
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be used directly, without key derivation.
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- ``master_key_descriptor`` specifies how to find the master key in
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the keyring; see `Adding keys`_. It is up to userspace to choose a
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@ -401,11 +401,11 @@ followed by the 16-character lower case hex representation of the
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``master_key_descriptor`` that was set in the encryption policy. The
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key payload must conform to the following structure::
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#define FS_MAX_KEY_SIZE 64
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#define FSCRYPT_MAX_KEY_SIZE 64
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struct fscrypt_key {
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u32 mode;
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u8 raw[FS_MAX_KEY_SIZE];
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u8 raw[FSCRYPT_MAX_KEY_SIZE];
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u32 size;
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};
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@ -574,7 +574,7 @@ much confusion if an encryption policy were to be added to or removed
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from anything other than an empty directory.) The struct is defined
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as follows::
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#define FS_KEY_DESCRIPTOR_SIZE 8
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#define FSCRYPT_KEY_DESCRIPTOR_SIZE 8
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#define FS_KEY_DERIVATION_NONCE_SIZE 16
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struct fscrypt_context {
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@ -582,7 +582,7 @@ as follows::
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u8 contents_encryption_mode;
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u8 filenames_encryption_mode;
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u8 flags;
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u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
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u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
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u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
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};
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@ -10,35 +10,30 @@
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#include <linux/types.h>
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#define FS_KEY_DESCRIPTOR_SIZE 8
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#define FSCRYPT_KEY_DESCRIPTOR_SIZE 8
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/* Encryption policy flags */
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#define FS_POLICY_FLAGS_PAD_4 0x00
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#define FS_POLICY_FLAGS_PAD_8 0x01
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#define FS_POLICY_FLAGS_PAD_16 0x02
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#define FS_POLICY_FLAGS_PAD_32 0x03
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#define FS_POLICY_FLAGS_PAD_MASK 0x03
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#define FS_POLICY_FLAG_DIRECT_KEY 0x04 /* use master key directly */
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#define FS_POLICY_FLAGS_VALID 0x07
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#define FSCRYPT_POLICY_FLAGS_PAD_4 0x00
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#define FSCRYPT_POLICY_FLAGS_PAD_8 0x01
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#define FSCRYPT_POLICY_FLAGS_PAD_16 0x02
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#define FSCRYPT_POLICY_FLAGS_PAD_32 0x03
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#define FSCRYPT_POLICY_FLAGS_PAD_MASK 0x03
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#define FSCRYPT_POLICY_FLAG_DIRECT_KEY 0x04 /* use master key directly */
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#define FSCRYPT_POLICY_FLAGS_VALID 0x07
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/* Encryption algorithms */
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#define FS_ENCRYPTION_MODE_INVALID 0
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#define FS_ENCRYPTION_MODE_AES_256_XTS 1
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#define FS_ENCRYPTION_MODE_AES_256_GCM 2
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#define FS_ENCRYPTION_MODE_AES_256_CBC 3
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#define FS_ENCRYPTION_MODE_AES_256_CTS 4
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#define FS_ENCRYPTION_MODE_AES_128_CBC 5
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#define FS_ENCRYPTION_MODE_AES_128_CTS 6
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#define FS_ENCRYPTION_MODE_SPECK128_256_XTS 7 /* Removed, do not use. */
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#define FS_ENCRYPTION_MODE_SPECK128_256_CTS 8 /* Removed, do not use. */
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#define FS_ENCRYPTION_MODE_ADIANTUM 9
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#define FSCRYPT_MODE_AES_256_XTS 1
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#define FSCRYPT_MODE_AES_256_CTS 4
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#define FSCRYPT_MODE_AES_128_CBC 5
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#define FSCRYPT_MODE_AES_128_CTS 6
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#define FSCRYPT_MODE_ADIANTUM 9
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struct fscrypt_policy {
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__u8 version;
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__u8 contents_encryption_mode;
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__u8 filenames_encryption_mode;
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__u8 flags;
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__u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
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__u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
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};
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#define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy)
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@ -46,16 +41,40 @@ struct fscrypt_policy {
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#define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy)
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/* Parameters for passing an encryption key into the kernel keyring */
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#define FS_KEY_DESC_PREFIX "fscrypt:"
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#define FS_KEY_DESC_PREFIX_SIZE 8
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#define FSCRYPT_KEY_DESC_PREFIX "fscrypt:"
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#define FSCRYPT_KEY_DESC_PREFIX_SIZE 8
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/* Structure that userspace passes to the kernel keyring */
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#define FS_MAX_KEY_SIZE 64
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#define FSCRYPT_MAX_KEY_SIZE 64
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struct fscrypt_key {
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__u32 mode;
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__u8 raw[FS_MAX_KEY_SIZE];
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__u8 raw[FSCRYPT_MAX_KEY_SIZE];
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__u32 size;
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};
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/**********************************************************************/
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/* old names; don't add anything new here! */
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#define FS_KEY_DESCRIPTOR_SIZE FSCRYPT_KEY_DESCRIPTOR_SIZE
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#define FS_POLICY_FLAGS_PAD_4 FSCRYPT_POLICY_FLAGS_PAD_4
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#define FS_POLICY_FLAGS_PAD_8 FSCRYPT_POLICY_FLAGS_PAD_8
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#define FS_POLICY_FLAGS_PAD_16 FSCRYPT_POLICY_FLAGS_PAD_16
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#define FS_POLICY_FLAGS_PAD_32 FSCRYPT_POLICY_FLAGS_PAD_32
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#define FS_POLICY_FLAGS_PAD_MASK FSCRYPT_POLICY_FLAGS_PAD_MASK
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#define FS_POLICY_FLAG_DIRECT_KEY FSCRYPT_POLICY_FLAG_DIRECT_KEY
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#define FS_POLICY_FLAGS_VALID FSCRYPT_POLICY_FLAGS_VALID
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#define FS_ENCRYPTION_MODE_INVALID 0 /* never used */
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#define FS_ENCRYPTION_MODE_AES_256_XTS FSCRYPT_MODE_AES_256_XTS
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#define FS_ENCRYPTION_MODE_AES_256_GCM 2 /* never used */
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#define FS_ENCRYPTION_MODE_AES_256_CBC 3 /* never used */
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#define FS_ENCRYPTION_MODE_AES_256_CTS FSCRYPT_MODE_AES_256_CTS
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#define FS_ENCRYPTION_MODE_AES_128_CBC FSCRYPT_MODE_AES_128_CBC
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#define FS_ENCRYPTION_MODE_AES_128_CTS FSCRYPT_MODE_AES_128_CTS
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#define FS_ENCRYPTION_MODE_SPECK128_256_XTS 7 /* removed */
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#define FS_ENCRYPTION_MODE_SPECK128_256_CTS 8 /* removed */
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#define FS_ENCRYPTION_MODE_ADIANTUM FSCRYPT_MODE_ADIANTUM
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#define FS_KEY_DESC_PREFIX FSCRYPT_KEY_DESC_PREFIX
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#define FS_KEY_DESC_PREFIX_SIZE FSCRYPT_KEY_DESC_PREFIX_SIZE
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#define FS_MAX_KEY_SIZE FSCRYPT_MAX_KEY_SIZE
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#endif /* _UAPI_LINUX_FSCRYPT_H */
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