Add Adiantum support for fscrypt
-----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEK2m5VNv+CHkogTfJ8vlZVpUNgaMFAlwyBbEACgkQ8vlZVpUN gaNrawgAhYWrPwsEFM17dziRWRm8Ub9QgQUK6JRt+vE5KCRRVdXgJSLVH4esW9rJ X+QQ0diT8ZMKjdbsyz0cVmwP7nqQ5EKzjxts6J8vtbWDB6+nvaDLNdicJgUOprcT jIi8/45XKmyGUVO9Au6Wdda/zZi4dQBkXd+zUFGWYQRYL0LgmboWHKlaWueu7Qha xVtavYPSKUSMH8+r1F+HU6P41+1IBiuK4tCwfKfAqJ367Ushzk9xVKHNGrGDAQNi BTbn4NOOFaYvmVudJbQjD3tHtuQu2JsxlclB5KAtLBm1r3+vb3fMGsNyPBUmNp6Y YE/xKhACP4kYlk9xCG7vWcWGyTu90g== =HR7f -----END PGP SIGNATURE----- Merge tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt Pull fscrypt updates from Ted Ts'o: "Add Adiantum support for fscrypt" * tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt: fscrypt: add Adiantum support
This commit is contained in:
Linus Torvalds
commit
baa6707381
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@ -132,47 +132,28 @@ designed for this purpose be used, such as scrypt, PBKDF2, or Argon2.
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Per-file keys
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-------------
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Master keys are not used to encrypt file contents or names directly.
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Instead, a unique key is derived for each encrypted file, including
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each regular file, directory, and symbolic link. This has several
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advantages:
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Since each master key can protect many files, it is necessary to
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"tweak" the encryption of each file so that the same plaintext in two
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files doesn't map to the same ciphertext, or vice versa. In most
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cases, fscrypt does this by deriving per-file keys. When a new
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encrypted inode (regular file, directory, or symlink) is created,
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fscrypt randomly generates a 16-byte nonce and stores it in the
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inode's encryption xattr. Then, it uses a KDF (Key Derivation
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Function) to derive the file's key from the master key and nonce.
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- In cryptosystems, the same key material should never be used for
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different purposes. Using the master key as both an XTS key for
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contents encryption and as a CTS-CBC key for filenames encryption
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would violate this rule.
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- Per-file keys simplify the choice of IVs (Initialization Vectors)
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for contents encryption. Without per-file keys, to ensure IV
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uniqueness both the inode and logical block number would need to be
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encoded in the IVs. This would make it impossible to renumber
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inodes, which e.g. ``resize2fs`` can do when resizing an ext4
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filesystem. With per-file keys, it is sufficient to encode just the
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logical block number in the IVs.
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- Per-file keys strengthen the encryption of filenames, where IVs are
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reused out of necessity. With a unique key per directory, IV reuse
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is limited to within a single directory.
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- Per-file keys allow individual files to be securely erased simply by
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securely erasing their keys. (Not yet implemented.)
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The Adiantum encryption mode (see `Encryption modes and usage`_) is
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special, since it accepts longer IVs and is suitable for both contents
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and filenames encryption. For it, a "direct key" option is offered
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where the file's nonce is included in the IVs and the master key is
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used for encryption directly. This improves performance; however,
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users must not use the same master key for any other encryption mode.
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A KDF (Key Derivation Function) is used to derive per-file keys from
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the master key. This is done instead of wrapping a randomly-generated
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key for each file because it reduces the size of the encryption xattr,
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which for some filesystems makes the xattr more likely to fit in-line
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in the filesystem's inode table. With a KDF, only a 16-byte nonce is
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required --- long enough to make key reuse extremely unlikely. A
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wrapped key, on the other hand, would need to be up to 64 bytes ---
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the length of an AES-256-XTS key. Furthermore, currently there is no
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requirement to support unlocking a file with multiple alternative
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master keys or to support rotating master keys. Instead, the master
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keys may be wrapped in userspace, e.g. as done by the `fscrypt
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<https://github.com/google/fscrypt>`_ tool.
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Below, the KDF and design considerations are described in more detail.
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The current KDF encrypts the master key using the 16-byte nonce as an
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AES-128-ECB key. The output is used as the derived key. If the
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output is longer than needed, then it is truncated to the needed
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length. Truncation is the norm for directories and symlinks, since
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those use the CTS-CBC encryption mode which requires a key half as
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long as that required by the XTS encryption mode.
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The current KDF works by encrypting the master key with AES-128-ECB,
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using the file's nonce as the AES key. The output is used as the
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derived key. If the output is longer than needed, then it is
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truncated to the needed length.
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Note: this KDF meets the primary security requirement, which is to
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produce unique derived keys that preserve the entropy of the master
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@ -181,6 +162,20 @@ However, it is nonstandard and has some problems such as being
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reversible, so it is generally considered to be a mistake! It may be
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replaced with HKDF or another more standard KDF in the future.
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Key derivation was chosen over key wrapping because wrapped keys would
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require larger xattrs which would be less likely to fit in-line in the
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filesystem's inode table, and there didn't appear to be any
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significant advantages to key wrapping. In particular, currently
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there is no requirement to support unlocking a file with multiple
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alternative master keys or to support rotating master keys. Instead,
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the master keys may be wrapped in userspace, e.g. as is done by the
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`fscrypt <https://github.com/google/fscrypt>`_ tool.
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Including the inode number in the IVs was considered. However, it was
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rejected as it would have prevented ext4 filesystems from being
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resized, and by itself still wouldn't have been sufficient to prevent
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the same key from being directly reused for both XTS and CTS-CBC.
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Encryption modes and usage
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==========================
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@ -191,54 +186,80 @@ Currently, the following pairs of encryption modes are supported:
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- AES-256-XTS for contents and AES-256-CTS-CBC for filenames
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- AES-128-CBC for contents and AES-128-CTS-CBC for filenames
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- Adiantum for both contents and filenames
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If unsure, you should use the (AES-256-XTS, AES-256-CTS-CBC) pair.
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It is strongly recommended to use AES-256-XTS for contents encryption.
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AES-128-CBC was added only for low-powered embedded devices with
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crypto accelerators such as CAAM or CESA that do not support XTS.
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Adiantum is a (primarily) stream cipher-based mode that is fast even
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on CPUs without dedicated crypto instructions. It's also a true
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wide-block mode, unlike XTS. It can also eliminate the need to derive
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per-file keys. However, it depends on the security of two primitives,
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XChaCha12 and AES-256, rather than just one. See the paper
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"Adiantum: length-preserving encryption for entry-level processors"
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(https://eprint.iacr.org/2018/720.pdf) for more details. To use
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Adiantum, CONFIG_CRYPTO_ADIANTUM must be enabled. Also, fast
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implementations of ChaCha and NHPoly1305 should be enabled, e.g.
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CONFIG_CRYPTO_CHACHA20_NEON and CONFIG_CRYPTO_NHPOLY1305_NEON for ARM.
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New encryption modes can be added relatively easily, without changes
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to individual filesystems. However, authenticated encryption (AE)
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modes are not currently supported because of the difficulty of dealing
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with ciphertext expansion.
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Contents encryption
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-------------------
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For file contents, each filesystem block is encrypted independently.
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Currently, only the case where the filesystem block size is equal to
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the system's page size (usually 4096 bytes) is supported. With the
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XTS mode of operation (recommended), the logical block number within
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the file is used as the IV. With the CBC mode of operation (not
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recommended), ESSIV is used; specifically, the IV for CBC is the
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logical block number encrypted with AES-256, where the AES-256 key is
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the SHA-256 hash of the inode's data encryption key.
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the system's page size (usually 4096 bytes) is supported.
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For filenames, the full filename is encrypted at once. Because of the
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requirements to retain support for efficient directory lookups and
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filenames of up to 255 bytes, a constant initialization vector (IV) is
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used. However, each encrypted directory uses a unique key, which
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limits IV reuse to within a single directory. Note that IV reuse in
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the context of CTS-CBC encryption means that when the original
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filenames share a common prefix at least as long as the cipher block
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size (16 bytes for AES), the corresponding encrypted filenames will
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also share a common prefix. This is undesirable; it may be fixed in
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the future by switching to an encryption mode that is a strong
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pseudorandom permutation on arbitrary-length messages, e.g. the HEH
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(Hash-Encrypt-Hash) mode.
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Each block's IV is set to the logical block number within the file as
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a little endian number, except that:
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Since filenames are encrypted with the CTS-CBC mode of operation, the
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plaintext and ciphertext filenames need not be multiples of the AES
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block size, i.e. 16 bytes. However, the minimum size that can be
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encrypted is 16 bytes, so shorter filenames are NUL-padded to 16 bytes
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before being encrypted. In addition, to reduce leakage of filename
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lengths via their ciphertexts, all filenames are NUL-padded to the
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next 4, 8, 16, or 32-byte boundary (configurable). 32 is recommended
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since this provides the best confidentiality, at the cost of making
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directory entries consume slightly more space. Note that since NUL
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(``\0``) is not otherwise a valid character in filenames, the padding
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will never produce duplicate plaintexts.
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- With CBC mode encryption, ESSIV is also used. Specifically, each IV
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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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Filenames encryption
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--------------------
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For filenames, each full filename is encrypted at once. Because of
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the requirements to retain support for efficient directory lookups and
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filenames of up to 255 bytes, the same IV is used for every filename
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in a directory.
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However, each encrypted directory still uses a unique key; or
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alternatively (for the "direct key" configuration) has the file's
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nonce included in the IVs. Thus, IV reuse is limited to within a
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single directory.
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With CTS-CBC, the IV reuse means that when the plaintext filenames
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share a common prefix at least as long as the cipher block size (16
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bytes for AES), the corresponding encrypted filenames will also share
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a common prefix. This is undesirable. Adiantum does not have this
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weakness, as it is a wide-block encryption mode.
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All supported filenames encryption modes accept any plaintext length
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>= 16 bytes; cipher block alignment is not required. However,
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filenames shorter than 16 bytes are NUL-padded to 16 bytes before
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being encrypted. In addition, to reduce leakage of filename lengths
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via their ciphertexts, all filenames are NUL-padded to the next 4, 8,
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16, or 32-byte boundary (configurable). 32 is recommended since this
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provides the best confidentiality, at the cost of making directory
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entries consume slightly more space. Note that since NUL (``\0``) is
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not otherwise a valid character in filenames, the padding will never
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produce duplicate plaintexts.
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Symbolic link targets are considered a type of filename and are
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encrypted in the same way as filenames in directory entries. Each
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symlink also uses a unique key; hence, the hardcoded IV is not a
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problem for symlinks.
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encrypted in the same way as filenames in directory entries, except
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that IV reuse is not a problem as each symlink has its own inode.
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User API
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========
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@ -272,9 +293,13 @@ This structure must be initialized as follows:
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and FS_ENCRYPTION_MODE_AES_256_CTS (4) for
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``filenames_encryption_mode``.
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- ``flags`` must be set to a value from ``<linux/fs.h>`` which
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- ``flags`` must contain a value from ``<linux/fs.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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- ``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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@ -133,15 +133,25 @@ struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *inode, gfp_t gfp_flags)
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}
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EXPORT_SYMBOL(fscrypt_get_ctx);
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void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
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const struct fscrypt_info *ci)
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{
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memset(iv, 0, ci->ci_mode->ivsize);
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iv->lblk_num = cpu_to_le64(lblk_num);
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if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY)
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memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);
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if (ci->ci_essiv_tfm != NULL)
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crypto_cipher_encrypt_one(ci->ci_essiv_tfm, iv->raw, iv->raw);
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}
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int fscrypt_do_page_crypto(const struct inode *inode, fscrypt_direction_t rw,
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u64 lblk_num, struct page *src_page,
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struct page *dest_page, unsigned int len,
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unsigned int offs, gfp_t gfp_flags)
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{
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struct {
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__le64 index;
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u8 padding[FS_IV_SIZE - sizeof(__le64)];
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} iv;
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union fscrypt_iv iv;
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struct skcipher_request *req = NULL;
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DECLARE_CRYPTO_WAIT(wait);
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struct scatterlist dst, src;
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@ -151,15 +161,7 @@ int fscrypt_do_page_crypto(const struct inode *inode, fscrypt_direction_t rw,
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BUG_ON(len == 0);
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BUILD_BUG_ON(sizeof(iv) != FS_IV_SIZE);
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BUILD_BUG_ON(AES_BLOCK_SIZE != FS_IV_SIZE);
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iv.index = cpu_to_le64(lblk_num);
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memset(iv.padding, 0, sizeof(iv.padding));
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if (ci->ci_essiv_tfm != NULL) {
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crypto_cipher_encrypt_one(ci->ci_essiv_tfm, (u8 *)&iv,
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(u8 *)&iv);
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}
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fscrypt_generate_iv(&iv, lblk_num, ci);
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req = skcipher_request_alloc(tfm, gfp_flags);
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if (!req)
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@ -40,10 +40,11 @@ int fname_encrypt(struct inode *inode, const struct qstr *iname,
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{
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struct skcipher_request *req = NULL;
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DECLARE_CRYPTO_WAIT(wait);
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struct crypto_skcipher *tfm = inode->i_crypt_info->ci_ctfm;
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int res = 0;
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char iv[FS_CRYPTO_BLOCK_SIZE];
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struct fscrypt_info *ci = inode->i_crypt_info;
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struct crypto_skcipher *tfm = ci->ci_ctfm;
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union fscrypt_iv iv;
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struct scatterlist sg;
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int res;
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/*
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* Copy the filename to the output buffer for encrypting in-place and
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@ -55,7 +56,7 @@ int fname_encrypt(struct inode *inode, const struct qstr *iname,
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memset(out + iname->len, 0, olen - iname->len);
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/* Initialize the IV */
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memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
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fscrypt_generate_iv(&iv, 0, ci);
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/* Set up the encryption request */
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req = skcipher_request_alloc(tfm, GFP_NOFS);
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@ -65,7 +66,7 @@ int fname_encrypt(struct inode *inode, const struct qstr *iname,
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CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
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crypto_req_done, &wait);
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sg_init_one(&sg, out, olen);
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skcipher_request_set_crypt(req, &sg, &sg, olen, iv);
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skcipher_request_set_crypt(req, &sg, &sg, olen, &iv);
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/* Do the encryption */
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res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
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@ -94,9 +95,10 @@ static int fname_decrypt(struct inode *inode,
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struct skcipher_request *req = NULL;
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DECLARE_CRYPTO_WAIT(wait);
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struct scatterlist src_sg, dst_sg;
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struct crypto_skcipher *tfm = inode->i_crypt_info->ci_ctfm;
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int res = 0;
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char iv[FS_CRYPTO_BLOCK_SIZE];
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struct fscrypt_info *ci = inode->i_crypt_info;
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struct crypto_skcipher *tfm = ci->ci_ctfm;
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union fscrypt_iv iv;
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int res;
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/* Allocate request */
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req = skcipher_request_alloc(tfm, GFP_NOFS);
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@ -107,12 +109,12 @@ static int fname_decrypt(struct inode *inode,
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crypto_req_done, &wait);
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/* Initialize IV */
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memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
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fscrypt_generate_iv(&iv, 0, ci);
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/* Create decryption request */
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sg_init_one(&src_sg, iname->name, iname->len);
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sg_init_one(&dst_sg, oname->name, oname->len);
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skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv);
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skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, &iv);
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res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
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skcipher_request_free(req);
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if (res < 0) {
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@ -17,7 +17,6 @@
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#include <crypto/hash.h>
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/* Encryption parameters */
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#define FS_IV_SIZE 16
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#define FS_KEY_DERIVATION_NONCE_SIZE 16
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/**
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@ -52,16 +51,42 @@ struct fscrypt_symlink_data {
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} __packed;
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/*
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* A pointer to this structure is stored in the file system's in-core
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* representation of an inode.
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* fscrypt_info - the "encryption key" for an inode
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*
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* When an encrypted file's key is made available, an instance of this struct is
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* allocated and stored in ->i_crypt_info. Once created, it remains until the
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* inode is evicted.
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*/
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struct fscrypt_info {
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/* The actual crypto transform used for encryption and decryption */
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struct crypto_skcipher *ci_ctfm;
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/*
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* Cipher for ESSIV IV generation. Only set for CBC contents
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* encryption, otherwise is NULL.
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*/
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struct crypto_cipher *ci_essiv_tfm;
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/*
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* Encryption mode used for this inode. It corresponds to either
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* ci_data_mode or ci_filename_mode, depending on the inode type.
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*/
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struct fscrypt_mode *ci_mode;
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/*
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* If non-NULL, then this inode uses a master key directly rather than a
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* derived key, and ci_ctfm will equal ci_master_key->mk_ctfm.
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* Otherwise, this inode uses a derived key.
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*/
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struct fscrypt_master_key *ci_master_key;
|
||||
|
||||
/* fields from the fscrypt_context */
|
||||
u8 ci_data_mode;
|
||||
u8 ci_filename_mode;
|
||||
u8 ci_flags;
|
||||
struct crypto_skcipher *ci_ctfm;
|
||||
struct crypto_cipher *ci_essiv_tfm;
|
||||
u8 ci_master_key[FS_KEY_DESCRIPTOR_SIZE];
|
||||
u8 ci_master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
|
||||
u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE];
|
||||
};
|
||||
|
||||
typedef enum {
|
||||
|
|
@ -83,6 +108,10 @@ static inline bool fscrypt_valid_enc_modes(u32 contents_mode,
|
|||
filenames_mode == FS_ENCRYPTION_MODE_AES_256_CTS)
|
||||
return true;
|
||||
|
||||
if (contents_mode == FS_ENCRYPTION_MODE_ADIANTUM &&
|
||||
filenames_mode == FS_ENCRYPTION_MODE_ADIANTUM)
|
||||
return true;
|
||||
|
||||
return false;
|
||||
}
|
||||
|
||||
|
|
@ -107,6 +136,22 @@ fscrypt_msg(struct super_block *sb, const char *level, const char *fmt, ...);
|
|||
#define fscrypt_err(sb, fmt, ...) \
|
||||
fscrypt_msg(sb, KERN_ERR, fmt, ##__VA_ARGS__)
|
||||
|
||||
#define FSCRYPT_MAX_IV_SIZE 32
|
||||
|
||||
union fscrypt_iv {
|
||||
struct {
|
||||
/* logical block number within the file */
|
||||
__le64 lblk_num;
|
||||
|
||||
/* per-file nonce; only set in DIRECT_KEY mode */
|
||||
u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
|
||||
};
|
||||
u8 raw[FSCRYPT_MAX_IV_SIZE];
|
||||
};
|
||||
|
||||
void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
|
||||
const struct fscrypt_info *ci);
|
||||
|
||||
/* fname.c */
|
||||
extern int fname_encrypt(struct inode *inode, const struct qstr *iname,
|
||||
u8 *out, unsigned int olen);
|
||||
|
|
@ -115,6 +160,16 @@ extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
|
|||
u32 *encrypted_len_ret);
|
||||
|
||||
/* keyinfo.c */
|
||||
|
||||
struct fscrypt_mode {
|
||||
const char *friendly_name;
|
||||
const char *cipher_str;
|
||||
int keysize;
|
||||
int ivsize;
|
||||
bool logged_impl_name;
|
||||
bool needs_essiv;
|
||||
};
|
||||
|
||||
extern void __exit fscrypt_essiv_cleanup(void);
|
||||
|
||||
#endif /* _FSCRYPT_PRIVATE_H */
|
||||
|
|
|
|||
|
|
@ -10,15 +10,21 @@
|
|||
*/
|
||||
|
||||
#include <keys/user-type.h>
|
||||
#include <linux/hashtable.h>
|
||||
#include <linux/scatterlist.h>
|
||||
#include <linux/ratelimit.h>
|
||||
#include <crypto/aes.h>
|
||||
#include <crypto/algapi.h>
|
||||
#include <crypto/sha.h>
|
||||
#include <crypto/skcipher.h>
|
||||
#include "fscrypt_private.h"
|
||||
|
||||
static struct crypto_shash *essiv_hash_tfm;
|
||||
|
||||
/* Table of keys referenced by FS_POLICY_FLAG_DIRECT_KEY policies */
|
||||
static DEFINE_HASHTABLE(fscrypt_master_keys, 6); /* 6 bits = 64 buckets */
|
||||
static DEFINE_SPINLOCK(fscrypt_master_keys_lock);
|
||||
|
||||
/*
|
||||
* Key derivation function. This generates the derived key by encrypting the
|
||||
* master key with AES-128-ECB using the inode's nonce as the AES key.
|
||||
|
|
@ -123,56 +129,37 @@ invalid:
|
|||
return ERR_PTR(-ENOKEY);
|
||||
}
|
||||
|
||||
/* Find the master key, then derive the inode's actual encryption key */
|
||||
static int find_and_derive_key(const struct inode *inode,
|
||||
const struct fscrypt_context *ctx,
|
||||
u8 *derived_key, unsigned int derived_keysize)
|
||||
{
|
||||
struct key *key;
|
||||
const struct fscrypt_key *payload;
|
||||
int err;
|
||||
|
||||
key = find_and_lock_process_key(FS_KEY_DESC_PREFIX,
|
||||
ctx->master_key_descriptor,
|
||||
derived_keysize, &payload);
|
||||
if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) {
|
||||
key = find_and_lock_process_key(inode->i_sb->s_cop->key_prefix,
|
||||
ctx->master_key_descriptor,
|
||||
derived_keysize, &payload);
|
||||
}
|
||||
if (IS_ERR(key))
|
||||
return PTR_ERR(key);
|
||||
err = derive_key_aes(payload->raw, ctx, derived_key, derived_keysize);
|
||||
up_read(&key->sem);
|
||||
key_put(key);
|
||||
return err;
|
||||
}
|
||||
|
||||
static struct fscrypt_mode {
|
||||
const char *friendly_name;
|
||||
const char *cipher_str;
|
||||
int keysize;
|
||||
bool logged_impl_name;
|
||||
} available_modes[] = {
|
||||
static struct fscrypt_mode available_modes[] = {
|
||||
[FS_ENCRYPTION_MODE_AES_256_XTS] = {
|
||||
.friendly_name = "AES-256-XTS",
|
||||
.cipher_str = "xts(aes)",
|
||||
.keysize = 64,
|
||||
.ivsize = 16,
|
||||
},
|
||||
[FS_ENCRYPTION_MODE_AES_256_CTS] = {
|
||||
.friendly_name = "AES-256-CTS-CBC",
|
||||
.cipher_str = "cts(cbc(aes))",
|
||||
.keysize = 32,
|
||||
.ivsize = 16,
|
||||
},
|
||||
[FS_ENCRYPTION_MODE_AES_128_CBC] = {
|
||||
.friendly_name = "AES-128-CBC",
|
||||
.cipher_str = "cbc(aes)",
|
||||
.keysize = 16,
|
||||
.ivsize = 16,
|
||||
.needs_essiv = true,
|
||||
},
|
||||
[FS_ENCRYPTION_MODE_AES_128_CTS] = {
|
||||
.friendly_name = "AES-128-CTS-CBC",
|
||||
.cipher_str = "cts(cbc(aes))",
|
||||
.keysize = 16,
|
||||
.ivsize = 16,
|
||||
},
|
||||
[FS_ENCRYPTION_MODE_ADIANTUM] = {
|
||||
.friendly_name = "Adiantum",
|
||||
.cipher_str = "adiantum(xchacha12,aes)",
|
||||
.keysize = 32,
|
||||
.ivsize = 32,
|
||||
},
|
||||
};
|
||||
|
||||
|
|
@ -198,14 +185,196 @@ select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode)
|
|||
return ERR_PTR(-EINVAL);
|
||||
}
|
||||
|
||||
static void put_crypt_info(struct fscrypt_info *ci)
|
||||
/* Find the master key, then derive the inode's actual encryption key */
|
||||
static int find_and_derive_key(const struct inode *inode,
|
||||
const struct fscrypt_context *ctx,
|
||||
u8 *derived_key, const struct fscrypt_mode *mode)
|
||||
{
|
||||
if (!ci)
|
||||
return;
|
||||
struct key *key;
|
||||
const struct fscrypt_key *payload;
|
||||
int err;
|
||||
|
||||
crypto_free_skcipher(ci->ci_ctfm);
|
||||
crypto_free_cipher(ci->ci_essiv_tfm);
|
||||
kmem_cache_free(fscrypt_info_cachep, ci);
|
||||
key = find_and_lock_process_key(FS_KEY_DESC_PREFIX,
|
||||
ctx->master_key_descriptor,
|
||||
mode->keysize, &payload);
|
||||
if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) {
|
||||
key = find_and_lock_process_key(inode->i_sb->s_cop->key_prefix,
|
||||
ctx->master_key_descriptor,
|
||||
mode->keysize, &payload);
|
||||
}
|
||||
if (IS_ERR(key))
|
||||
return PTR_ERR(key);
|
||||
|
||||
if (ctx->flags & FS_POLICY_FLAG_DIRECT_KEY) {
|
||||
if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) {
|
||||
fscrypt_warn(inode->i_sb,
|
||||
"direct key mode not allowed with %s",
|
||||
mode->friendly_name);
|
||||
err = -EINVAL;
|
||||
} else if (ctx->contents_encryption_mode !=
|
||||
ctx->filenames_encryption_mode) {
|
||||
fscrypt_warn(inode->i_sb,
|
||||
"direct key mode not allowed with different contents and filenames modes");
|
||||
err = -EINVAL;
|
||||
} else {
|
||||
memcpy(derived_key, payload->raw, mode->keysize);
|
||||
err = 0;
|
||||
}
|
||||
} else {
|
||||
err = derive_key_aes(payload->raw, ctx, derived_key,
|
||||
mode->keysize);
|
||||
}
|
||||
up_read(&key->sem);
|
||||
key_put(key);
|
||||
return err;
|
||||
}
|
||||
|
||||
/* Allocate and key a symmetric cipher object for the given encryption mode */
|
||||
static struct crypto_skcipher *
|
||||
allocate_skcipher_for_mode(struct fscrypt_mode *mode, const u8 *raw_key,
|
||||
const struct inode *inode)
|
||||
{
|
||||
struct crypto_skcipher *tfm;
|
||||
int err;
|
||||
|
||||
tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
|
||||
if (IS_ERR(tfm)) {
|
||||
fscrypt_warn(inode->i_sb,
|
||||
"error allocating '%s' transform for inode %lu: %ld",
|
||||
mode->cipher_str, inode->i_ino, PTR_ERR(tfm));
|
||||
return tfm;
|
||||
}
|
||||
if (unlikely(!mode->logged_impl_name)) {
|
||||
/*
|
||||
* fscrypt performance can vary greatly depending on which
|
||||
* crypto algorithm implementation is used. Help people debug
|
||||
* performance problems by logging the ->cra_driver_name the
|
||||
* first time a mode is used. Note that multiple threads can
|
||||
* race here, but it doesn't really matter.
|
||||
*/
|
||||
mode->logged_impl_name = true;
|
||||
pr_info("fscrypt: %s using implementation \"%s\"\n",
|
||||
mode->friendly_name,
|
||||
crypto_skcipher_alg(tfm)->base.cra_driver_name);
|
||||
}
|
||||
crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
|
||||
err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize);
|
||||
if (err)
|
||||
goto err_free_tfm;
|
||||
|
||||
return tfm;
|
||||
|
||||
err_free_tfm:
|
||||
crypto_free_skcipher(tfm);
|
||||
return ERR_PTR(err);
|
||||
}
|
||||
|
||||
/* Master key referenced by FS_POLICY_FLAG_DIRECT_KEY policy */
|
||||
struct fscrypt_master_key {
|
||||
struct hlist_node mk_node;
|
||||
refcount_t mk_refcount;
|
||||
const struct fscrypt_mode *mk_mode;
|
||||
struct crypto_skcipher *mk_ctfm;
|
||||
u8 mk_descriptor[FS_KEY_DESCRIPTOR_SIZE];
|
||||
u8 mk_raw[FS_MAX_KEY_SIZE];
|
||||
};
|
||||
|
||||
static void free_master_key(struct fscrypt_master_key *mk)
|
||||
{
|
||||
if (mk) {
|
||||
crypto_free_skcipher(mk->mk_ctfm);
|
||||
kzfree(mk);
|
||||
}
|
||||
}
|
||||
|
||||
static void put_master_key(struct fscrypt_master_key *mk)
|
||||
{
|
||||
if (!refcount_dec_and_lock(&mk->mk_refcount, &fscrypt_master_keys_lock))
|
||||
return;
|
||||
hash_del(&mk->mk_node);
|
||||
spin_unlock(&fscrypt_master_keys_lock);
|
||||
|
||||
free_master_key(mk);
|
||||
}
|
||||
|
||||
/*
|
||||
* Find/insert the given master key into the fscrypt_master_keys table. If
|
||||
* found, it is returned with elevated refcount, and 'to_insert' is freed if
|
||||
* non-NULL. If not found, 'to_insert' is inserted and returned if it's
|
||||
* non-NULL; otherwise NULL is returned.
|
||||
*/
|
||||
static struct fscrypt_master_key *
|
||||
find_or_insert_master_key(struct fscrypt_master_key *to_insert,
|
||||
const u8 *raw_key, const struct fscrypt_mode *mode,
|
||||
const struct fscrypt_info *ci)
|
||||
{
|
||||
unsigned long hash_key;
|
||||
struct fscrypt_master_key *mk;
|
||||
|
||||
/*
|
||||
* Careful: to avoid potentially leaking secret key bytes via timing
|
||||
* information, we must key the hash table by descriptor rather than by
|
||||
* raw key, and use crypto_memneq() when comparing raw keys.
|
||||
*/
|
||||
|
||||
BUILD_BUG_ON(sizeof(hash_key) > FS_KEY_DESCRIPTOR_SIZE);
|
||||
memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key));
|
||||
|
||||
spin_lock(&fscrypt_master_keys_lock);
|
||||
hash_for_each_possible(fscrypt_master_keys, mk, mk_node, hash_key) {
|
||||
if (memcmp(ci->ci_master_key_descriptor, mk->mk_descriptor,
|
||||
FS_KEY_DESCRIPTOR_SIZE) != 0)
|
||||
continue;
|
||||
if (mode != mk->mk_mode)
|
||||
continue;
|
||||
if (crypto_memneq(raw_key, mk->mk_raw, mode->keysize))
|
||||
continue;
|
||||
/* using existing tfm with same (descriptor, mode, raw_key) */
|
||||
refcount_inc(&mk->mk_refcount);
|
||||
spin_unlock(&fscrypt_master_keys_lock);
|
||||
free_master_key(to_insert);
|
||||
return mk;
|
||||
}
|
||||
if (to_insert)
|
||||
hash_add(fscrypt_master_keys, &to_insert->mk_node, hash_key);
|
||||
spin_unlock(&fscrypt_master_keys_lock);
|
||||
return to_insert;
|
||||
}
|
||||
|
||||
/* Prepare to encrypt directly using the master key in the given mode */
|
||||
static struct fscrypt_master_key *
|
||||
fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode,
|
||||
const u8 *raw_key, const struct inode *inode)
|
||||
{
|
||||
struct fscrypt_master_key *mk;
|
||||
int err;
|
||||
|
||||
/* Is there already a tfm for this key? */
|
||||
mk = find_or_insert_master_key(NULL, raw_key, mode, ci);
|
||||
if (mk)
|
||||
return mk;
|
||||
|
||||
/* Nope, allocate one. */
|
||||
mk = kzalloc(sizeof(*mk), GFP_NOFS);
|
||||
if (!mk)
|
||||
return ERR_PTR(-ENOMEM);
|
||||
refcount_set(&mk->mk_refcount, 1);
|
||||
mk->mk_mode = mode;
|
||||
mk->mk_ctfm = allocate_skcipher_for_mode(mode, raw_key, inode);
|
||||
if (IS_ERR(mk->mk_ctfm)) {
|
||||
err = PTR_ERR(mk->mk_ctfm);
|
||||
mk->mk_ctfm = NULL;
|
||||
goto err_free_mk;
|
||||
}
|
||||
memcpy(mk->mk_descriptor, ci->ci_master_key_descriptor,
|
||||
FS_KEY_DESCRIPTOR_SIZE);
|
||||
memcpy(mk->mk_raw, raw_key, mode->keysize);
|
||||
|
||||
return find_or_insert_master_key(mk, raw_key, mode, ci);
|
||||
|
||||
err_free_mk:
|
||||
free_master_key(mk);
|
||||
return ERR_PTR(err);
|
||||
}
|
||||
|
||||
static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
|
||||
|
|
@ -275,11 +444,67 @@ void __exit fscrypt_essiv_cleanup(void)
|
|||
crypto_free_shash(essiv_hash_tfm);
|
||||
}
|
||||
|
||||
/*
|
||||
* Given the encryption mode and key (normally the derived key, but for
|
||||
* FS_POLICY_FLAG_DIRECT_KEY mode it's the master key), set up the inode's
|
||||
* symmetric cipher transform object(s).
|
||||
*/
|
||||
static int setup_crypto_transform(struct fscrypt_info *ci,
|
||||
struct fscrypt_mode *mode,
|
||||
const u8 *raw_key, const struct inode *inode)
|
||||
{
|
||||
struct fscrypt_master_key *mk;
|
||||
struct crypto_skcipher *ctfm;
|
||||
int err;
|
||||
|
||||
if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY) {
|
||||
mk = fscrypt_get_master_key(ci, mode, raw_key, inode);
|
||||
if (IS_ERR(mk))
|
||||
return PTR_ERR(mk);
|
||||
ctfm = mk->mk_ctfm;
|
||||
} else {
|
||||
mk = NULL;
|
||||
ctfm = allocate_skcipher_for_mode(mode, raw_key, inode);
|
||||
if (IS_ERR(ctfm))
|
||||
return PTR_ERR(ctfm);
|
||||
}
|
||||
ci->ci_master_key = mk;
|
||||
ci->ci_ctfm = ctfm;
|
||||
|
||||
if (mode->needs_essiv) {
|
||||
/* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */
|
||||
WARN_ON(mode->ivsize != AES_BLOCK_SIZE);
|
||||
WARN_ON(ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY);
|
||||
|
||||
err = init_essiv_generator(ci, raw_key, mode->keysize);
|
||||
if (err) {
|
||||
fscrypt_warn(inode->i_sb,
|
||||
"error initializing ESSIV generator for inode %lu: %d",
|
||||
inode->i_ino, err);
|
||||
return err;
|
||||
}
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
|
||||
static void put_crypt_info(struct fscrypt_info *ci)
|
||||
{
|
||||
if (!ci)
|
||||
return;
|
||||
|
||||
if (ci->ci_master_key) {
|
||||
put_master_key(ci->ci_master_key);
|
||||
} else {
|
||||
crypto_free_skcipher(ci->ci_ctfm);
|
||||
crypto_free_cipher(ci->ci_essiv_tfm);
|
||||
}
|
||||
kmem_cache_free(fscrypt_info_cachep, ci);
|
||||
}
|
||||
|
||||
int fscrypt_get_encryption_info(struct inode *inode)
|
||||
{
|
||||
struct fscrypt_info *crypt_info;
|
||||
struct fscrypt_context ctx;
|
||||
struct crypto_skcipher *ctfm;
|
||||
struct fscrypt_mode *mode;
|
||||
u8 *raw_key = NULL;
|
||||
int res;
|
||||
|
|
@ -312,74 +537,42 @@ int fscrypt_get_encryption_info(struct inode *inode)
|
|||
if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
|
||||
return -EINVAL;
|
||||
|
||||
crypt_info = kmem_cache_alloc(fscrypt_info_cachep, GFP_NOFS);
|
||||
crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS);
|
||||
if (!crypt_info)
|
||||
return -ENOMEM;
|
||||
|
||||
crypt_info->ci_flags = ctx.flags;
|
||||
crypt_info->ci_data_mode = ctx.contents_encryption_mode;
|
||||
crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
|
||||
crypt_info->ci_ctfm = NULL;
|
||||
crypt_info->ci_essiv_tfm = NULL;
|
||||
memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
|
||||
sizeof(crypt_info->ci_master_key));
|
||||
memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor,
|
||||
FS_KEY_DESCRIPTOR_SIZE);
|
||||
memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
|
||||
|
||||
mode = select_encryption_mode(crypt_info, inode);
|
||||
if (IS_ERR(mode)) {
|
||||
res = PTR_ERR(mode);
|
||||
goto out;
|
||||
}
|
||||
WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
|
||||
crypt_info->ci_mode = mode;
|
||||
|
||||
/*
|
||||
* This cannot be a stack buffer because it is passed to the scatterlist
|
||||
* crypto API as part of key derivation.
|
||||
* This cannot be a stack buffer because it may be passed to the
|
||||
* scatterlist crypto API as part of key derivation.
|
||||
*/
|
||||
res = -ENOMEM;
|
||||
raw_key = kmalloc(mode->keysize, GFP_NOFS);
|
||||
if (!raw_key)
|
||||
goto out;
|
||||
|
||||
res = find_and_derive_key(inode, &ctx, raw_key, mode->keysize);
|
||||
res = find_and_derive_key(inode, &ctx, raw_key, mode);
|
||||
if (res)
|
||||
goto out;
|
||||
|
||||
ctfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
|
||||
if (IS_ERR(ctfm)) {
|
||||
res = PTR_ERR(ctfm);
|
||||
fscrypt_warn(inode->i_sb,
|
||||
"error allocating '%s' transform for inode %lu: %d",
|
||||
mode->cipher_str, inode->i_ino, res);
|
||||
goto out;
|
||||
}
|
||||
if (unlikely(!mode->logged_impl_name)) {
|
||||
/*
|
||||
* fscrypt performance can vary greatly depending on which
|
||||
* crypto algorithm implementation is used. Help people debug
|
||||
* performance problems by logging the ->cra_driver_name the
|
||||
* first time a mode is used. Note that multiple threads can
|
||||
* race here, but it doesn't really matter.
|
||||
*/
|
||||
mode->logged_impl_name = true;
|
||||
pr_info("fscrypt: %s using implementation \"%s\"\n",
|
||||
mode->friendly_name,
|
||||
crypto_skcipher_alg(ctfm)->base.cra_driver_name);
|
||||
}
|
||||
crypt_info->ci_ctfm = ctfm;
|
||||
crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
|
||||
res = crypto_skcipher_setkey(ctfm, raw_key, mode->keysize);
|
||||
res = setup_crypto_transform(crypt_info, mode, raw_key, inode);
|
||||
if (res)
|
||||
goto out;
|
||||
|
||||
if (S_ISREG(inode->i_mode) &&
|
||||
crypt_info->ci_data_mode == FS_ENCRYPTION_MODE_AES_128_CBC) {
|
||||
res = init_essiv_generator(crypt_info, raw_key, mode->keysize);
|
||||
if (res) {
|
||||
fscrypt_warn(inode->i_sb,
|
||||
"error initializing ESSIV generator for inode %lu: %d",
|
||||
inode->i_ino, res);
|
||||
goto out;
|
||||
}
|
||||
}
|
||||
if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
|
||||
crypt_info = NULL;
|
||||
out:
|
||||
|
|
|
|||
|
|
@ -199,7 +199,8 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
|
|||
child_ci = child->i_crypt_info;
|
||||
|
||||
if (parent_ci && child_ci) {
|
||||
return memcmp(parent_ci->ci_master_key, child_ci->ci_master_key,
|
||||
return memcmp(parent_ci->ci_master_key_descriptor,
|
||||
child_ci->ci_master_key_descriptor,
|
||||
FS_KEY_DESCRIPTOR_SIZE) == 0 &&
|
||||
(parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
|
||||
(parent_ci->ci_filename_mode ==
|
||||
|
|
@ -254,7 +255,7 @@ int fscrypt_inherit_context(struct inode *parent, struct inode *child,
|
|||
ctx.contents_encryption_mode = ci->ci_data_mode;
|
||||
ctx.filenames_encryption_mode = ci->ci_filename_mode;
|
||||
ctx.flags = ci->ci_flags;
|
||||
memcpy(ctx.master_key_descriptor, ci->ci_master_key,
|
||||
memcpy(ctx.master_key_descriptor, ci->ci_master_key_descriptor,
|
||||
FS_KEY_DESCRIPTOR_SIZE);
|
||||
get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
|
||||
BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE);
|
||||
|
|
|
|||
|
|
@ -223,7 +223,8 @@ struct fsxattr {
|
|||
#define FS_POLICY_FLAGS_PAD_16 0x02
|
||||
#define FS_POLICY_FLAGS_PAD_32 0x03
|
||||
#define FS_POLICY_FLAGS_PAD_MASK 0x03
|
||||
#define FS_POLICY_FLAGS_VALID 0x03
|
||||
#define FS_POLICY_FLAG_DIRECT_KEY 0x04 /* use master key directly */
|
||||
#define FS_POLICY_FLAGS_VALID 0x07
|
||||
|
||||
/* Encryption algorithms */
|
||||
#define FS_ENCRYPTION_MODE_INVALID 0
|
||||
|
|
@ -235,6 +236,7 @@ struct fsxattr {
|
|||
#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
|
||||
|
||||
struct fscrypt_policy {
|
||||
__u8 version;
|
||||
|
|
|
|||
Loading…
Reference in New Issue