Lines Matching full:encryption
2 Filesystem-level encryption (fscrypt)
9 transparent encryption of files and directories.
15 use encryption, see the documentation for the userspace tool `fscrypt
20 <https://source.android.com/security/encryption/file-based>`_, over
56 Provided that userspace chooses a strong encryption key, fscrypt
72 fscrypt (and storage encryption in general) can only provide limited
89 After an encryption key has been added, fscrypt does not hide the
97 encryption but rather only by the correctness of the kernel.
98 Therefore, any encryption-specific access control checks would merely
107 security vulnerability, can compromise all encryption keys that are
110 However, fscrypt allows encryption keys to be removed from the kernel,
115 encryption key from kernel memory. If it does so, it will also try to
151 v1 encryption policies have some weaknesses with respect to online
165 - Non-root users cannot securely remove encryption keys.
167 All the above problems are fixed with v2 encryption policies. For
168 this reason among others, it is recommended to use v2 encryption
180 encryption modes being used. For example, if AES-256-XTS is used for
181 contents encryption, the master key must be 64 bytes (512 bits). Note
208 encryption directly. Instead, they are only used as input to a KDF
212 the key is used for v1 encryption policies or for v2 encryption
214 encryption policies. (No real-world attack is currently known on this
218 For v1 encryption policies, the KDF only supports deriving per-file
219 encryption keys. It works by encrypting the master key with
224 For v2 encryption policies, the KDF is HKDF-SHA512. The master key is
227 key to be derived. For example, when a per-file encryption key is
237 Per-file encryption keys
241 "tweak" the encryption of each file so that the same plaintext in two
246 inode's encryption xattr. Then, it uses a KDF (as described in `Key
262 The Adiantum encryption mode (see `Encryption modes and usage`_) is
263 suitable for both contents and filenames encryption, and it accepts
271 per-file encryption keys are not used. Instead, whenever any data
275 - For v1 encryption policies, the encryption is done directly with the
279 - For v2 encryption policies, the encryption is done with a per-mode
281 other v2 encryption policies.
287 the encryption keys are derived from the master key, encryption mode
289 protected by the same master key sharing a single contents encryption
290 key and a single filenames encryption key. To still encrypt different
294 This format is optimized for use with inline encryption hardware
306 This format is optimized for use with inline encryption hardware
315 For master keys used for v2 encryption policies, a unique 16-byte "key
325 just like deriving a per-file encryption key, except that a different
329 Encryption modes and usage
332 fscrypt allows one encryption mode to be specified for file contents
333 and one encryption mode to be specified for filenames. Different
334 directory trees are permitted to use different encryption modes.
335 Currently, the following pairs of encryption modes are supported:
352 per-file encryption keys. However, it depends on the security of two
354 paper "Adiantum: length-preserving encryption for entry-level
360 New encryption modes can be added relatively easily, without changes
361 to individual filesystems. However, authenticated encryption (AE)
365 Contents encryption
369 Starting from Linux kernel 5.5, encryption of filesystems with block
375 - With CBC mode encryption, ESSIV is also used. Specifically, each IV
377 of the file's data encryption key.
380 Currently this is only allowed with the Adiantum encryption mode.
394 Filenames encryption
411 weakness, as it is a wide-block encryption mode.
413 All supported filenames encryption modes accept any plaintext length
431 Setting an encryption policy
437 The FS_IOC_SET_ENCRYPTION_POLICY ioctl sets an encryption policy on an
439 has the specified encryption policy. It takes in a pointer to
475 encryption modes to use. If unsure, use FSCRYPT_MODE_AES_256_XTS
490 v1 encryption policies only support the PAD_* and DIRECT_KEY flags.
491 The other flags are only supported by v2 encryption policies.
496 - For v2 encryption policies, ``__reserved`` must be zeroed.
498 - For v1 encryption policies, ``master_key_descriptor`` specifies how
507 For v2 encryption policies, ``master_key_descriptor`` has been
517 encryption policy is assigned to the directory, turning it into an
521 directory will be encrypted, inheriting the same encryption policy.
525 FS_IOC_SET_ENCRYPTION_POLICY validates that the specified encryption
530 When a v2 encryption policy is assigned to a directory, it is also
548 - ``EEXIST``: the file is already encrypted with an encryption policy
550 - ``EINVAL``: an invalid encryption policy was specified (invalid
552 encryption policy was specified but the directory has the casefold
554 - ``ENOKEY``: a v2 encryption policy was specified, but the key with
561 - ``ENOTTY``: this type of filesystem does not implement encryption
562 - ``EOPNOTSUPP``: the kernel was not configured with encryption
564 had encryption enabled on it. (For example, to use encryption on an
573 Getting an encryption policy
576 Two ioctls are available to get a file's encryption policy:
590 The FS_IOC_GET_ENCRYPTION_POLICY_EX ioctl retrieves the encryption
616 encryption policy version
618 - ``ENOTTY``: this type of filesystem does not implement encryption,
621 - ``EOPNOTSUPP``: the kernel was not configured with encryption
623 had encryption enabled on it
625 encryption policy version, but the policy struct does not fit into
637 encryption policy, if any, for a directory or regular file. However,
646 encrypted using a newer encryption policy version.
654 value is intended to used as a salt when deriving an encryption key
660 Getting a file's encryption nonce
668 encryption is being done correctly. It is not needed for normal use
677 The FS_IOC_ADD_ENCRYPTION_KEY ioctl adds a master encryption key to
714 - If the key is being added for use by v1 encryption policies, then
722 Alternatively, if the key is being added for use by v2 encryption
784 - ``ENOTTY``: this type of filesystem does not implement encryption
785 - ``EOPNOTSUPP``: the kernel was not configured with encryption
787 had encryption enabled on it
792 For v1 encryption policies, a master encryption key can also be
797 This method is deprecated (and not supported for v2 encryption
815 ``master_key_descriptor`` that was set in the encryption policy. The
858 encryption key from the filesystem, and possibly removes the key
876 - To remove a key used by v1 encryption policies, set
882 - To remove a key used by v2 encryption policies, set
929 - ``ENOTTY``: this type of filesystem does not implement encryption
930 - ``EOPNOTSUPP``: the kernel was not configured with encryption
932 had encryption enabled on it
955 master encryption key. It can be executed on any file or directory on
978 - To get the status of a key for v1 encryption policies, set
982 - To get the status of a key for v2 encryption policies, set
1007 - ``ENOTTY``: this type of filesystem does not implement encryption
1008 - ``EOPNOTSUPP``: the kernel was not configured with encryption
1010 had encryption enabled on it
1021 encryption policies using the legacy mechanism involving
1030 With the encryption key, encrypted regular files, directories, and
1032 after all, the encryption is intended to be transparent. However,
1035 - Unencrypted files, or files encrypted with a different encryption
1037 linked into an encrypted directory; see `Encryption policy
1084 files, directories, and symlinks even before their encryption key has
1085 been added, or after their encryption key has been removed:
1121 without the encryption key. This would require special APIs which
1124 Encryption policy enforcement
1127 After an encryption policy has been set on a directory, all regular
1129 (recursively) will inherit that encryption policy. Special files ---
1134 files, or files encrypted with a different encryption policy, in an
1138 attacks that try to disable or downgrade encryption in known locations
1141 this by validating all top-level encryption policies prior to access.
1146 Encryption context
1149 An encryption policy is represented on-disk by
1154 setxattr() because of the special semantics of the encryption xattr.
1155 (In particular, there would be much confusion if an encryption policy
1183 policy structs (see `Setting an encryption policy`_), except that the
1186 different files to be encrypted differently; see `Per-file encryption
1202 buffers regardless of encryption. Other filesystems, such as ext4 and
1203 F2FS, have to allocate bounce pages specially for encryption.
1205 Fscrypt is also able to use inline encryption hardware instead of the
1208 for an ext4/F2FS filesystem), it adds encryption contexts to bios and
1211 make use of inline encryption, fscrypt will only be able to do so if
1212 either hardware inline encryption support is available for the
1213 selected encryption algorithm or CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK
1226 With encryption, lookups must be supported and efficient both with and
1227 without the encryption key. Clearly, it would not work to hash the
1265 inline encryption support. For example, to test ext4 and
1266 f2fs encryption using `kvm-xfstests
1272 UBIFS encryption can also be tested this way, but it should be done in
1278 No tests should fail. However, tests that use non-default encryption