Lines Matching full:the
5 The dm-integrity target emulates a block device that has additional
9 writing the sector and the integrity tag must be atomic - i.e. in case of
12 To guarantee write atomicity, the dm-integrity target uses journal, it
13 writes sector data and integrity tags into a journal, commits the journal
14 and then copies the data and integrity tags to their respective location.
16 The dm-integrity target can be used with the dm-crypt target - in this
17 situation the dm-crypt target creates the integrity data and passes them
18 to the dm-integrity target via bio_integrity_payload attached to the bio.
19 In this mode, the dm-crypt and dm-integrity targets provide authenticated
20 disk encryption - if the attacker modifies the encrypted device, an I/O
23 The dm-integrity target can also be used as a standalone target, in this
24 mode it calculates and verifies the integrity tag internally. In this
25 mode, the dm-integrity target can be used to detect silent data
26 corruption on the disk or in the I/O path.
29 instead of a journal. If a bit in the bitmap is 1, the corresponding
30 region's data and integrity tags are not synchronized - if the machine
31 crashes, the unsynchronized regions will be recalculated. The bitmap mode
32 is faster than the journal mode, because we don't have to write the data
34 when the machine crashes, it may not be detected.
36 When loading the target for the first time, the kernel driver will format
37 the device. But it will only format the device if the superblock contains
38 zeroes. If the superblock is neither valid nor zeroed, the dm-integrity
41 Accesses to the on-disk metadata area containing checksums (aka tags) are
43 occurs, each unique metadata area gets its own buffer(s). The buffer size
44 is capped at the size of the metadata area, but may be smaller, thereby
45 requiring multiple buffers to represent the full metadata area. A smaller
46 buffer size will produce a smaller resulting read/write operation to the
47 metadata area for small reads/writes. The metadata is still read even in
48 a full write to the data covered by a single buffer.
50 To use the target for the first time:
52 1. overwrite the superblock with zeroes
53 2. load the dm-integrity target with one-sector size, the kernel driver
54 will format the device
55 3. unload the dm-integrity target
56 4. read the "provided_data_sectors" value from the superblock
57 5. load the dm-integrity target with the target size
59 6. if you want to use dm-integrity with dm-crypt, load the dm-crypt target
60 with the size "provided_data_sectors"
65 1. the underlying block device
67 2. the number of reserved sector at the beginning of the device - the
70 3. the size of the integrity tag (if "-" is used, the size is taken from
71 the internal-hash algorithm)
78 separately. In case of crash, it is possible that the data
81 data and integrity tags are written to the
83 either both data and tag or none of them are written. The
84 journaled mode degrades write throughput twice because the
87 synchronization, the driver maintains a bitmap of dirty
91 checksums are not checked and writes to the device are not
92 allowed. This mode is useful for data recovery if the
93 device cannot be activated in any of the other standard
96 data directly in the underlying device sectors.
97 The underlying device must have an integrity profile that
99 space for the selected integrity tag.
101 5. the number of additional arguments
106 The size of journal, this argument is used only if formatting the
107 device. If the device is already formatted, the value from the
111 The number of interleaved sectors. This values is rounded down to
112 a power of two. If the device is already formatted, the value from
113 the superblock is used.
116 Don't interleave the data and metadata on the device. Use a
120 The number of sectors in one metadata buffer. The value is rounded
124 The journal watermark in percents. When the size of the journal
125 exceeds this watermark, the thread that flushes the journal will
129 Commit time in milliseconds. When this time passes, the journal is
130 written. The journal is also written immediately if the FLUSH
133 internal_hash:algorithm(:key) (the key is optional)
135 When this argument is used, the dm-integrity target won't accept
136 integrity tags from the upper target, but it will automatically
137 generate and verify the integrity tags.
140 will protect the data against accidental corruption.
143 cryptographic authentication of the data without encryption.
145 When this argument is not used, the integrity tags are accepted
146 from an upper layer target, such as dm-crypt. The upper layer
147 target should check the validity of the integrity tags.
150 Recalculate the integrity tags automatically. It is only valid
153 journal_crypt:algorithm(:key) (the key is optional)
154 Encrypt the journal using given algorithm to make sure that the
155 attacker can't read the journal. You can use a block cipher here
159 The journal contains history of last writes to the block device,
160 an attacker reading the journal could see the last sector numbers
161 that were written. From the sector numbers, the attacker can infer
162 the size of files that were written. To protect against this
163 situation, you can encrypt the journal.
165 journal_mac:algorithm(:key) (the key is optional)
166 Protect sector numbers in the journal from accidental or malicious
172 mode, the integrity of journal entries is checked when replaying
173 the journal. Thus, modified sector number would be detected at
177 The size of a data block in bytes. The larger the block size the
182 In the bitmap mode, this parameter specifies the number of
186 The bitmap flush interval in milliseconds. The metadata buffers
190 Allow block discard requests (a.k.a. TRIM) for the integrity device.
194 Use a smaller padding of the tag area that is more
201 - the section number is mixed to the mac, so that an attacker can't
203 - the superblock is protected by journal_mac
204 - a 16-byte salt stored in the superblock is mixed to the mac, so
205 that the attacker can't detect that two disks have the same hmac
206 key and also to disallow the attacker to move sectors from one
211 default for security reasons - an attacker could modify the volume,
212 set recalc_sector to zero, and the kernel would not detect the
215 The journal mode (D/J), buffer_sectors, journal_watermark, commit_time and
216 allow_discards can be changed when reloading the target (load an inactive
217 table and swap the tables with suspend and resume). The other arguments
218 should not be changed when reloading the target because the layout of disk
219 data depend on them and the reloaded target would be non-functional.
221 For example, on a device using the default interleave_sectors of 32768, a
224 256 sectors of metadata per data area. With the default buffer_sectors of
230 1. the number of integrity mismatches
231 2. provided data sectors - that is the number of sectors that the user
233 3. the current recalculating position (or '-' if we didn't recalculate)
236 The layout of the formatted block device:
240 storing LUKS metadata or for other purpose), the size of the reserved
241 area is specified in the target arguments
244 * magic string - identifies that the device was formatted
248 * the number of journal sections
249 * provided data sectors - the number of sectors that this target
250 provides (i.e. the size of the device minus the size of all
251 metadata and padding). The user of this target should not send
252 bios that access data beyond the "provided data sectors" limit.
259 - journal area contains the bitmap of dirty
264 The journal is divided into sections, each section contains:
270 * logical sector (specifies where the data and tag should
273 * integrity tag (the size is specified in the superblock)
277 * mac (8-bytes), all the macs in 8 metadata sectors form a
279 numbers in the journal section, to protect against a
280 possibility that the attacker tampers with sector
281 numbers in the journal.
284 * data area (the size is variable; it depends on how many journal
285 entries fit into the metadata area)
287 - every sector in the data area contains:
289 * data (504 bytes of data, the last 8 bytes are stored in
290 the journal entry)
293 To test if the whole journal section was written correctly, every
294 512-byte sector of the journal ends with 8-byte commit id. If the
296 assumed that the section was written correctly. If the commit id
297 doesn't match, the section was written partially and it should not
304 sector in the data area. The size of this area is always 4KiB or
306 * data area - it contains data sectors. The number of data sectors
308 in the superblock.