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diff --git a/Documentation/admin-guide/device-mapper/dm-inlinecrypt.rst b/Documentation/admin-guide/device-mapper/dm-inlinecrypt.rst new file mode 100644 index 000000000000..8258a72f00a8 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-inlinecrypt.rst @@ -0,0 +1,129 @@ +============== +dm-inlinecrypt +============== + +Device-Mapper's "inlinecrypt" target provides transparent encryption of block devices +using the inline encryption hardware. + +For a more detailed description of inline encryption, see: +https://docs.kernel.org/block/inline-encryption.html + +Parameters:: + + <cipher> <key> <iv_offset> <device path> \ + <offset> [<#opt_params> <opt_params>] + +<cipher> + Encryption cipher type. + + The cipher specifications format is:: + + cipher + + Examples:: + + aes-xts-plain64 + + The cipher type corresponds to the encryption modes supported by + inline crypto in the block layer. Currently, only + BLK_ENCRYPTION_MODE_AES_256_XTS (i.e. aes-xts-plain64) is supported. + +<key> + Key used for encryption. It is encoded either as a hexadecimal number + or it can be passed as <key_string> prefixed with single colon + character (':') for keys residing in kernel keyring service. + You can only use key sizes that are valid for the selected cipher. + Note that the size in bytes of a valid key must be in below range. + + [BLK_CRYPTO_KEY_TYPE_RAW, BLK_CRYPTO_KEY_TYPE_HW_WRAPPED] + +<key_string> + The kernel keyring key is identified by string in following format: + <key_size>:<keyring_type>:<key_description>. + +<key_size> + The encryption key size in bytes. The kernel key payload size must match + the value passed in <key_size>. + +<keyring_type> + The type of the key inside the kernel keyring. It can be either 'logon', + or 'trusted' kernel key type. + +<key_description> + The kernel keyring key description inlinecrypt target should look for + when loading key of <keyring_type>. + +<iv_offset> + The IV offset is a sector count that is added to the sector number + before creating the IV. + +<device path> + This is the device that is going to be used as backend and contains the + encrypted data. You can specify it as a path like /dev/xxx or a device + number <major>:<minor>. + +<offset> + Starting sector within the device where the encrypted data begins. + +<#opt_params> + Number of optional parameters. If there are no optional parameters, + the optional parameters section can be skipped or #opt_params can be zero. + Otherwise #opt_params is the number of following arguments. + + Example of optional parameters section: + keytype:raw allow_discards sector_size:4096 iv_large_sectors + +<key_type> + The type of the key as seen by the block layer, either standard or + hardware-wrapped. The string is supplied in the table as <keytype:raw> + or <keytype:hw-wrapped>. + +allow_discards + Block discard requests (a.k.a. TRIM) are passed through the inlinecrypt + device. The default is to ignore discard requests. + + WARNING: Assess the specific security risks carefully before enabling this + option. For example, allowing discards on encrypted devices may lead to + the leak of information about the ciphertext device (filesystem type, + used space etc.) if the discarded blocks can be located easily on the + device later. + +sector_size:<bytes> + Use <bytes> as the encryption unit instead of 512 bytes sectors. + This option can be in range 512 - 4096 bytes and must be power of two. + Virtual device will announce this size as a minimal IO and logical sector. + +iv_large_sectors + Use <sector_size>-based sector numbers for IV generation instead of + 512-byte sectors. + + For dm-inlinecrypt, this flag must be specified when <sector_size> + is larger than 512 bytes. The legacy 512-byte-based IV behavior is + not supported. + + When specified, if <sector_size> is 4096 bytes, plain64 IV for the + second sector will be 1, and <iv_offset> must be a multiple of + <sector_size> (in 512-byte units). + +Example scripts +=============== +Currently, dm-inlinecrypt devices must be set up directly using dmsetup. +There is no userspace support yet to integrate dm-inlinecrypt with LUKS +or cryptsetup. In particular, cryptsetup currently only supports +dm-crypt, and cannot be used to create dm-inlinecrypt mappings. + +The following examples demonstrate how to create dm-inlinecrypt devices +using dmsetup + +:: + + #!/bin/sh + # Create a inlinecrypt device using dmsetup + dmsetup create inlinecrypt1 --table "0 `blockdev --getsz $1` inlinecrypt aes-xts-plain64 babebabebabebabebabebabebabebabebabebabebabebabebabebabebabebabe 0 0 $1 0 1 keytype:raw" + +:: + + #!/bin/sh + # Create a inlinecrypt device using dmsetup when encryption key is stored in keyring service + dmsetup create inlinecrypt2 --table "0 `blockdev --getsz $1` inlinecrypt aes-xts-plain64 :64:logon:fde:dminlinecrypt_test_key 0 0 $1 0 1 keytype:raw" + |