BACKPORT: dm crypt: optionally support larger encryption sector size
Add optional "sector_size" parameter that specifies encryption sector
size (atomic unit of block device encryption).
Parameter can be in range 512 - 4096 bytes and must be power of two.
For compatibility reasons, the maximal IO must fit into the page limit,
so the limit is set to the minimal page size possible (4096 bytes).
NOTE: this device cannot yet be handled by cryptsetup if this parameter
is set.
IV for the sector is calculated from the 512 bytes sector offset unless
the iv_large_sectors option is used.
Test script using dmsetup:
DEV="/dev/sdb"
DEV_SIZE=$(blockdev --getsz $DEV)
KEY="9c1185a5c5e9fc54612808977ee8f548b2258d31ddadef707ba62c166051b9e3cd0294c27515f2bccee924e8823ca6e124b8fc3167ed478bca702babe4e130ac"
BLOCK_SIZE=4096
# dmsetup create test_crypt --table "0 $DEV_SIZE crypt aes-xts-plain64 $KEY 0 $DEV 0 1 sector_size:$BLOCK_SIZE"
# dmsetup table --showkeys test_crypt
Signed-off-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
(cherry picked from commit 8f0009a225171cc1b76a6b443de5137b26e1374b)
Conflicts:
Documentation/device-mapper/dm-crypt.txt
drivers/md/dm-crypt.c
Bug: 112008522
Test: In an x86_64 VM, wrote 0's to a dm-crypt target using Adiantum and
a fixed key and verified the resulting ciphertext on the device
matches that produced by the upstream kernel in the same case.
Did this for both 512 and 4096-byte sectors.
key=EC0531985A96E87F756035F804D051DFE50036987D9AD706AAF9BDBDD1F5B786
dmsetup create crypt --table \
"0 $((1<<17)) crypt xchacha12,aes-adiantum-plain64 $key 0 /dev/vdc 0"
dd if=/dev/zero bs=4096 count=$((1<<14)) of=/dev/mapper/crypt
sync && echo 3 > /proc/sys/vm/drop_caches
head -c $((1<<26)) /dev/vdc | md5sum # 44e24946ce308f3b4495bc2ff9cade8b
head -c $((1<<26)) /dev/vdc | xz -9 | wc -c
dmsetup remove crypt
key=EC0531985A96E87F756035F804D051DFE50036987D9AD706AAF9BDBDD1F5B786
dmsetup create crypt --table \
"0 $((1<<17)) crypt xchacha12,aes-adiantum-plain64 $key 0 /dev/vdc 0 2 sector_size:4096 iv_large_sectors"
dd if=/dev/zero bs=4096 count=$((1<<14)) of=/dev/mapper/crypt
sync && echo 3 > /proc/sys/vm/drop_caches
head -c $((1<<26)) /dev/vdc | md5sum # 8aa1cb4f5ebef575b15b5f8d64763118
head -c $((1<<26)) /dev/vdc | xz -9 | wc -c
dmsetup remove crypt
Change-Id: Ie247fd41b11adcf8520de0b1554568a1b7155860
Signed-off-by: Eric Biggers <ebiggers@google.com>
diff --git a/Documentation/device-mapper/dm-crypt.txt b/Documentation/device-mapper/dm-crypt.txt
index 692171f..ae9a8f7 100644
--- a/Documentation/device-mapper/dm-crypt.txt
+++ b/Documentation/device-mapper/dm-crypt.txt
@@ -76,6 +76,20 @@
thread because it benefits CFQ to have writes submitted using the
same context.
+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
+ IV generators will use sector number counted in <sector_size> units
+ instead of default 512 bytes sectors.
+
+ For example, if <sector_size> is 4096 bytes, plain64 IV for the second
+ sector will be 8 (without flag) and 1 if iv_large_sectors is present.
+ The <iv_offset> must be multiple of <sector_size> (in 512 bytes units)
+ if this flag is specified.
+
Example scripts
===============
LUKS (Linux Unified Key Setup) is now the preferred way to set up disk