However, where device manufacturers use customized versions of these apps, they will want to ensure at a minimum there are direct-boot aware packages providing the following services:. In addition to the core changes to use the file-based encryption capabilities in kernel, many system packages including the lockscreen and the SystemUI have been modified to support the FBE and Direct Boot features.
These include:. More examples of applications and services that are encryption aware can be found by running the command mangrep directBootAware in the frameworks or packages directory of the AOSP source tree. Note : Storage policies are applied to a folder and all of its subfolders. Manufacturers should limit the contents that go unencrypted to the OTA folder and the folder that holds the key that decrypts the system.
Most contents should reside in credential-encrypted storage rather than device-encrypted storage. First and foremost, apps such as alarm clocks, phone, accessibility features should be made android:directBootAware according to Direct Boot developer documentation.
To enable it in a kernel that is version 5. If your device will support adoptable storage or will use metadata encryption on internal storage, also enable the kernel configuration options needed for metadata encryption as described in the metadata encryption documentation. In addition to functional support for Ext4 or F2FS encryption, device manufacturers should also enable cryptographic acceleration to speed up file-based encryption and improve the user experience.
The Android common kernels version 4. The inline encryption framework can be enabled by setting the following kernel configuration options:. Enabling FBE on a device requires enabling it on the internal storage userdata. This also automatically enables FBE on adoptable storage; however, the encryption format on adoptable storage may be overridden if necessary.
This option defines the encryption format on internal storage. It contains up to three colon-separated parameters:. This mode is unimplemented by the Android common kernels, but it could be implemented by vendors using custom kernel patches. The on-disk format produced by this mode was vendor-specific. On devices launching with Android 11 or higher, this mode is no longer allowed and a standard encryption format must be used instead.
By default, file contents encryption is done using the Linux kernel's cryptography API. If you want to use inline encryption hardware instead, also add the inlinecrypt mount option. For example, a full fstab line might look like:. Since Android 9, FBE and adoptable storage can be used together.
Specifying the fileencryption fstab option for userdata also automatically enables both FBE and metadata encryption on adoptable storage. The generation of keys and management of the kernel keyring is handled by vold. There is no support for earlier versions of the Keymaster HAL. By the time the on-post-fs phase of init completes, the Keymaster must be ready to handle requests.
File-based encryption applies the encryption policy at the directory level. When additional users and profiles are created, the necessary additional keys are generated and stored in the keystore; their credential and devices storage locations are created and the encryption policy links these keys to those directories. In Android 11 and higher, the encryption policy is no longer hardcoded into a centralized location, but rather is defined by arguments to the mkdir commands in the init scripts.
It is possible to add exceptions to prevent certain directories from being encrypted at all. If modifications of this sort are made then the device manufacturer should include SELinux policies that only grant access to the applications that need to use the unencrypted directory. This should exclude all untrusted applications. To facilitate rapid migration of system apps, there are two new attributes that can be set at the application level.
The defaultToDeviceProtectedStorage attribute is available only to system apps. The directBootAware attribute is available to all. The directBootAware attribute at the application level is shorthand for marking all components in the app as being encryption aware. System apps using this flag must carefully audit all data stored in the default location, and change the paths of sensitive data to use CE storage.
Device manufactures using this option should carefully inspect the data that they are storing to ensure that it contains no personal information. When running in this mode, the following System APIs are available to explicitly manage a Context backed by CE storage when needed, which are equivalent to their Device Protected counterparts. Each user in a multi-user environment gets a separate encryption key. Every user gets two keys: a DE and a CE key.
User 0 must log into the device first as it is a special user. This is pertinent for Device Administration uses. However, those apps will be able to access only CE-encrypted directories for users that are already unlocked. An application may be able to interact freely across the DE areas, but one user unlocked does not mean that all the users on the device are unlocked.
The application should check this status before trying to access these areas. The recovery partition is unable to access the DE-protected storage on the userdata partition. As the OTA can be applied during normal operation there is no need for recovery to access data on the encrypted drive.
In addition, device manufacturers may perform the following manual tests. On a device with FBE enabled:. Additionally, testers can boot a userdebug instance with a lockscreen set on the primary user. Then adb shell into the device and use su to become root. Device manufacturers are also encouraged to explore running the upstream Linux tests for fscrypt on their devices or kernels. These tests are part of the xfstests filesystem test suite. However, these upstream tests are not offically supported by Android.
This section provides details on the AOSP implementation and describes how file-based encryption works. It should not be necessary for device manufacturers to make any changes here to use FBE and Direct Boot on their devices. The AOSP implementation uses "fscrypt" encryption supported by ext4 and f2fs in the kernel and normally is configured to:. Adiantum encryption is also supported. When Adiantum encryption is enabled, both file contents and file names are encrypted with Adiantum.
For more information about fscrypt, see the upstream kernel documentation. To use this TEE key, three requirements must be met:. The auth token is a cryptographically authenticated token generated by Gatekeeper when a user successfully logs in. The TEE will refuse to use the key unless the correct auth token is supplied. You can use it to encrypt entire storage devices or only selected partitions using pre-boot authentication.
It was created to address certain reliability problems in cryptoloop and can be used to back up several volume types. How useful are encryption tools to you and which utilities are your favourite to use? Feel free to drop your comments, questions, and suggestions below.
TecMint is the fastest growing and most trusted community site for any kind of Linux Articles, Guides and Books on the web. Millions of people visit TecMint! If you like what you are reading, please consider buying us a coffee or 2 as a token of appreciation. We are thankful for your never ending support. Must have VeraCrypt and 7-zip. These are great options for encryption. It may be flawed, intentionally or not.
Is there a backdoor? Is it sending you information to a remote server? Its really helpful tutorial and thanks for sharing. However I have one question regarding encrypting full disk without formatting the drive. Is there any way to do so? I looked for the tuts over internet and all those tuts mentioned to format the disk. Not sure how to without formatting. Could you please help me with this? Thanks in advanced. Have a question or suggestion?
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For synchronous operation, the set of API calls is small and conceptually similar to any other crypto library. Asynchronous operation is provided by the kernel crypto API which implies that the invocation of a cipher operation will complete almost instantly. That invocation triggers the cipher operation but it does not signal its completion. Before invoking a cipher operation, the caller must provide a callback function the kernel crypto API can invoke to signal the completion of the cipher operation.
Furthermore, the caller must ensure it can handle such asynchronous events by applying appropriate locking around its data. If applicable, additional templates may enclose other templates, such as. The kernel crypto API may provide multiple implementations of a template or a single block cipher.
The answer to that question is the priority number assigned to each cipher implementation by the kernel crypto API. When a caller uses the string to refer to a cipher during initialization of a cipher handle, the kernel crypto API looks up all implementations providing an implementation with that name and selects the implementation with the highest priority.
Now, a caller may have the need to refer to a specific cipher implementation and thus does not want to rely on the priority-based selection. To accommodate this scenario, the kernel crypto API allows the cipher implementation to register a unique name in addition to common names.
When using that unique name, a caller is therefore always sure to refer to the intended cipher implementation. However, that list does not specify all possible permutations of templates and ciphers. When allocating a cipher handle, the caller only specifies the cipher type.
Symmetric ciphers, however, typically support multiple key sizes e. AES vs. These key sizes are determined with the length of the provided key. Thus, the kernel crypto API does not provide a separate way to select the particular symmetric cipher key size. The different cipher handle allocation functions allow the specification of a type and mask flag. Both parameters have the following meaning and are therefore not covered in the subsequent sections.
The type flag specifies the type of the cipher algorithm. The caller usually provides a 0 when the caller wants the default handling. Otherwise, the caller may provide the following selections which match the aforementioned cipher types:. The mask flag restricts the type of cipher.
Usually, a caller provides a 0 for the mask flag. When the caller provides a mask and type specification, the caller limits the search the kernel crypto API can perform for a suitable cipher implementation for the given cipher name. Verify that you have xz installed, then you can proceed like so:. If wget was not used inside the build directory, it will be necessary to move the tarball into it, e.
To be absolutely sure that none permission errors occur, chown needs to be run to transfer ownership of the folder to the current user. This will transfer ownership of every file in the folder to you, so you do not encouter any errors related to permissions.
To finalise the preparation, ensure that the kernel tree is absolutely clean; do not rely on the source tree being clean after unpacking. To do so, first change into the new kernel source directory created, and then run the make mrproper command:.
This is the most crucial step in customizing the default kernel to reflect your computer's precise specifications. Kernel configuration is set in its. By setting the options in. This method will create a. If a stock Arch kernel is running, you can use the following command inside the custom kernel source directory:. Otherwise, the default configuration can be found online in the official Arch Linux kernel package.
There are several tools available to fine-tune the kernel configuration, which provide an alternative to otherwise spending hours manually configuring each and every one of the options available during compilation. The chosen method should be run inside the kernel source directory, and all will either create a new.
All optional configurations will be automatically enabled, although any newer configuration options i. Once the changes have been made save the. It is a good idea to make a backup copy outside the source directory. You may need to do this multiple times before you get all the options right. If unsure, only change a few options between compilations. If you cannot boot your newly built kernel, see the list of necessary items here.
Running lspci -k from liveCD lists names of kernel modules in use. Most importantly, you must maintain cgroups support. This is necessary for systemd. Compilation time will vary from as little as fifteen minutes to over an hour, depending on your kernel configuration and processor capability.
Once the. For example, for kernel version 5. This keeps the modules for individual kernels used separated. The kernel compilation process will generate a compressed bzImage big zImage of that kernel, if it does not, you may have to run. Provided the name is prefixed with vmlinuz- , you may name the kernel as you wish.
In the examples below, the installed and compiled 5. An existing mkinitcpio preset can be copied and modified so that the custom kernel initramfs images can be generated in the same way as for an official kernel. This is useful where intending to recompile the kernel e. In the example below, the preset file for the stock Arch kernel will be copied and modified for kernel 5.
Second, edit the file and amend for the custom kernel. Finally, generate the initramfs images for the custom kernel in the same way as for an official kernel:. Rather than use a preset file, mkinitcpio can also be used to generate an initramfs file manually. The syntax of the command is:. The System. It is a type of "phone directory" list of functions in a particular build of a kernel. This "symbol-name to address mapping" is used by:.
Add an entry for your new kernel in your bootloader's configuration file. See Arch boot process Feature comparison for possible boot loaders, their wiki articles and other information.