Some tests I did to understand how to work with dm-crypt.
Create
slap steph # dd if=/dev/urandom bs=1M count=2 >> crypttest
2+0 records in
2+0 records out
2097152 bytes (2.1 MB) copied, 0.673763 s, 3.1 MB/s
slap steph # ls -l crypttest
-rw-r--r-- 1 steph users 2097152 May 30 14:13 crypttest
slap steph # losetup -f
/dev/loop3
slap steph # losetup /dev/loop3 crypttest
slap steph # cryptsetup -y -c serpent -s 256 create mycrypt /dev/loop3
Enter passphrase:
Verify passphrase:
slap steph # dmsetup ls
mycrypt (254, 4)
crypt-steph (254, 3)
crypt-swap (254, 0)
crypt-bn (254, 2)
crypt-tmp (254, 1)
slap steph # mkreiserfs /dev/mapper/mycrypt
mkreiserfs 3.6.19 (2003 www.namesys.com)
A pair of credits:
Yury Umanets (aka Umka) developed libreiser4, userspace plugins, and all
userspace tools (reiser4progs) except of fsck.
Vladimir Saveliev started as the most junior programmer on the team, and became
the lead programmer. He is now an experienced highly productive programmer. He
wrote the extent handling code for Reiser4, plus parts of the balancing code
and file write and file read.
Guessing about desired format.. Kernel 2.6.18-gentoo-r6 is running.
reiserfs_create_journal: cannot create a journal of 8193 blocks with 18 offset on 512 blocks
Too small! Recreate at over 32M (521/2 = 256. 8193/256 ~= 32). I’ll do 100M
slap steph # cryptsetup remove mycrypt
slap steph # dmsetup ls
crypt-steph (254, 3)
crypt-swap (254, 0)
crypt-bn (254, 2)
crypt-tmp (254, 1)
slap steph # losetup -d /dev/loop3
slap steph # losetup -f
/dev/loop3
slap steph # dd if=/dev/urandom bs=1M count=100 > crypttest
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 34.2838 s, 3.1 MB/s
slap steph # ls -l crypttest
-rw-r--r-- 1 steph users 104857600 May 30 14:38 crypttest
slap steph # losetup /dev/loop3 crypttest
slap steph # cryptsetup -y -c serpent -s 256 create mycrypt /dev/loop3
Enter passphrase:
Verify passphrase:
slap steph # dmsetup ls
mycrypt (254, 4)
crypt-steph (254, 3)
crypt-swap (254, 0)
crypt-bn (254, 2)
crypt-tmp (254, 1)
slap steph # mkreiserfs /dev/mapper/mycrypt
mkreiserfs 3.6.19 (2003 www.namesys.com)
A pair of credits:
Oleg Drokin was the debugger for V3 during most of the time that V4 was under
development, and was quite skilled and fast at it. He wrote the large write
optimization of V3.
Jeremy Fitzhardinge wrote the teahash.c code for V3. Colin Plumb also
contributed to that.
Guessing about desired format.. Kernel 2.6.18-gentoo-r6 is running.
Format 3.6 with standard journal
Count of blocks on the device: 25600
Number of blocks consumed by mkreiserfs formatting process: 8212
Blocksize: 4096
Hash function used to sort names: "r5"
Journal Size 8193 blocks (first block 18)
Journal Max transaction length 1024
inode generation number: 0
UUID: da6a44e2-f7f8-4e69-a5d3-7c9c70b8adaf
ATTENTION: YOU SHOULD REBOOT AFTER FDISK!
ALL DATA WILL BE LOST ON '/dev/mapper/mycrypt'!
Continue (y/n):y
Initializing journal - 0%....20%....40%....60%....80%....100%
Syncing..ok
Tell your friends to use a kernel based on 2.4.18 or later, and especially not a
kernel based on 2.4.9, when you use reiserFS. Have fun.
ReiserFS is successfully created on /dev/mapper/mycrypt.
slap steph # mount /dev/mapper/mycrypt cryptmount
Create test files
slap steph # echo "testing testing 123" > cryptmount/test1.txt
slap steph # mkdir cryptmount/testdir
slap steph # echo "testing testing 234" > cryptmount/testdir/test2.txt
slap steph # echo "testing testing 345" > cryptmount/testdir/test3.txt
slap steph # cat cryptmount/test1.txt
testing testing 123
slap steph # cat cryptmount/testdir/test2.txt
testing testing 234
slap steph # cat cryptmount/testdir/test3.txt
testing testing 345
Test unmount
slap steph # umount cryptmount
slap steph # cryptsetup remove mycrypt
slap steph # losetup -d /dev/loop3
slap steph # losetup -f
/dev/loop3
slap steph # dmsetup ls
crypt-steph (254, 3)
crypt-swap (254, 0)
crypt-bn (254, 2)
crypt-tmp (254, 1)
Test remount
slap steph # losetup /dev/loop3 crypttest
slap steph # cryptsetup -y -c serpent -s 256 create mycrypt /dev/loop3
Enter passphrase:
Verify passphrase:
slap steph # mount /dev/mapper/mycrypt cryptmount
slap steph # ls cryptmount/
test1.txt testdir
slap steph # cat cryptmount/test1.txt
testing testing 123
slap steph # cat cryptmount/testdir/test2.txt
testing testing 234
slap steph # cat cryptmount/testdir/test3.txt
testing testing 345
Test resize
slap steph # umount cryptmount
slap steph # cryptsetup remove mycrypt
slap steph # losetup -d /dev/loop3
slap steph # losetup -f
/dev/loop3
slap steph # dmsetup ls
crypt-steph (254, 3)
crypt-swap (254, 0)
crypt-bn (254, 2)
crypt-tmp (254, 1)
slap steph # dd if=/dev/urandom bs=1M count=50 >> crypttest
50+0 records in
50+0 records out
52428800 bytes (52 MB) copied, 15.263 s, 3.4 MB/s
slap steph # ls -l crypttest
-rw-r--r-- 1 steph users 157286400 May 30 14:56 crypttest
slap steph # losetup /dev/loop3 crypttest
slap steph # cryptsetup -y -c serpent -s 256 create mycrypt /dev/loop3
Enter passphrase:
Verify passphrase:
slap steph # resize_reiserfs /dev/mapper/mycrypt
resize_reiserfs 3.6.19 (2003 www.namesys.com)
ReiserFS report:
blocksize 4096
block count 38400 (25600)
free blocks 30187 (17388)
bitmap block count 2 (1)
Syncing..done
resize_reiserfs: Resizing finished successfully.
slap steph # mount /dev/mapper/mycrypt cryptmount
slap steph # ls cryptmount/
test1.txt testdir
slap steph # df cryptmount
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/mycrypt 153588 32840 120748 22% /home/steph/cryptmount
slap steph # df -h cryptmount
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/mycrypt 150M 33M 118M 22% /home/steph/cryptmount
slap steph # cat cryptmount/test1.txt
testing testing 123
slap steph # cat cryptmount/testdir/test2.txt
testing testing 234
slap steph # cat cryptmount/testdir/test3.txt
testing testing 345
Test password
slap steph # losetup /dev/loop3 crypttest
slap steph # cryptsetup -c serpent -s 256 create mycrypt /dev/loop3
Enter passphrase: (incorrect password entered)
slap steph # mount /dev/mapper/mycrypt cryptmount/
mount: you must specify the filesystem type
References
- http://gentoo-wiki.com/SECURITY_dmcrypt
- http://forums.gentoo.org/viewtopic-t-274651-highlight-encryption+pam.html
- http://forums.gentoo.org/viewtopic-t-364612-highlight-cryptsetup+resize.html
Unused related links
- http://forums.gentoo.org/viewtopic-t-454329-highlight-cryptsetup+resize.html
- http://www.nabble.com/Encrypting-a-user-home-folder-on-a-laptop-td15512217.html
- http://h3g3m0n.wordpress.com/2007/04/16/quick-simple-encrypted-loopback-filesystem/
Questions
What is ‘cryptsetup resize’ for?
Perhaps for resizing a block device that has changed size whilst mapped. See http://thread.gmane.org/gmane.linux.kernel.device-mapper.dm-crypt/145
Test ‘cryptsetup resize’
Clean start
slap steph # cryptsetup remove mycrypt
slap steph # losetup -d /dev/loop3
slap steph # dd if=/dev/urandom bs=1M count=100 > crypttest
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 33.7287 s, 3.1 MB/s
slap steph # losetup /dev/loop3 crypttest
slap steph # cryptsetup -y -c serpent -s 256 create mycrypt /dev/loop3
Enter passphrase:
Verify passphrase:
slap steph # mkreiserfs /dev/mapper/mycrypt
mkreiserfs 3.6.19 (2003 www.namesys.com)
A pair of credits:
The Defense Advanced Research Projects Agency (DARPA, www.darpa.mil) is the
primary sponsor of Reiser4. DARPA does not endorse this project; it merely
sponsors it.
Vitaly Fertman wrote fsck for V3 and maintains the reiserfsprogs package now.
He wrote librepair, userspace plugins repair code, fsck for V4, and worked on
developing libreiser4 and userspace plugins with Umka.
Guessing about desired format.. Kernel 2.6.18-gentoo-r6 is running.
Format 3.6 with standard journal
Count of blocks on the device: 25600
Number of blocks consumed by mkreiserfs formatting process: 8212
Blocksize: 4096
Hash function used to sort names: "r5"
Journal Size 8193 blocks (first block 18)
Journal Max transaction length 1024
inode generation number: 0
UUID: 2e1b01ea-8376-4f07-8e95-7470abb4bc6d
ATTENTION: YOU SHOULD REBOOT AFTER FDISK!
ALL DATA WILL BE LOST ON '/dev/mapper/mycrypt'!
Continue (y/n):y
Initializing journal - 0%....20%....40%....60%....80%....100%
Syncing..ok
Tell your friends to use a kernel based on 2.4.18 or later, and especially not a
kernel based on 2.4.9, when you use reiserFS. Have fun.
ReiserFS is successfully created on /dev/mapper/mycrypt.
slap steph # mount /dev/mapper/mycrypt cryptmount
slap steph # dd if=/dev/zero > cryptmount/zeroes
dd: writing to `standard output': No space left on device
138961+0 records in
138960+0 records out
71147520 bytes (71 MB) copied, 2.78217 s, 25.6 MB/s
slap steph # ls -l cryptmount/zeroes
-rw-r--r-- 1 root root 71147520 Jun 2 00:19 cryptmount/zeroes
slap steph # df cryptmount
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/mycrypt 102392 102392 0 100% /home/steph/cryptmount
Resize crypttest
slap steph # dd if=/dev/urandom bs=1M count=100 >> crypttest
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 30.4674 s, 3.4 MB/s
slap steph # cryptsetup resize mycrypt
slap steph # resize_reiserfs /dev/mapper/mycrypt
resize_reiserfs 3.6.19 (2003 www.namesys.com)
/dev/mapper/mycrypt already is of the needed size. Nothing to be done
Reiserfs doesn’t think crypt size has changed. Perhaps ‘cryptsetup resize’ already resized the reiserfs filesystem…
slap steph # umount cryptmount
slap steph # mount /dev/mapper/mycrypt cryptmount
slap steph # dd if=/dev/zero >> cryptmount/zeroes
dd: writing to `standard output': No space left on device
1+0 records in
0+0 records out
0 bytes (0 B) copied, 0.0295515 s, 0.0 kB/s
slap steph # ls -l cryptmount/zeroes
-rw-r--r-- 1 root root 71147520 Jun 2 00:22 cryptmount/zeroes
slap steph # df cryptmount
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/mycrypt 102392 102392 0 100% /home/steph/cryptmount
It didn’t. Recreate crypt and try again…
slap steph # umount cryptmount
slap steph # cryptsetup remove mycrypt
slap steph # cryptsetup -c serpent -s 256 create mycrypt /dev/loop3
Enter passphrase:
slap steph # mount /dev/mapper/mycrypt cryptmount
slap steph # dd if=/dev/zero >> cryptmount/zeroes
dd: writing to `standard output': No space left on device
1+0 records in
0+0 records out
0 bytes (0 B) copied, 0.0294059 s, 0.0 kB/s
slap steph # ls -l cryptmount/zeroes
-rw-r--r-- 1 root root 71147520 Jun 2 00:24 cryptmount/zeroes
slap steph # resize_reiserfs /dev/mapper/mycrypt
resize_reiserfs 3.6.19 (2003 www.namesys.com)
/dev/mapper/mycrypt already is of the needed size. Nothing to be done
Reiserfs still doesn’t think crypt size has changed. Need to reset loop?…
slap steph # umount cryptmount
slap steph # cryptsetup remove mycrypt
slap steph # losetup -d /dev/loop3
slap steph # losetup /dev/loop3 crypttest
slap steph # cryptsetup -c serpent -s 256 create mycrypt /dev/loop3
Enter passphrase:
slap steph # mount /dev/mapper/mycrypt cryptmount
slap steph # dd if=/dev/zero >> cryptmount/zeroes
dd: writing to `standard output': No space left on device
1+0 records in
0+0 records out
0 bytes (0 B) copied, 0.00282065 s, 0.0 kB/s
slap steph # ls -l cryptmount/zeroes
-rw-r--r-- 1 root root 71147520 Jun 2 00:27 cryptmount/zeroes
slap steph # umount cryptmount
slap steph # resize_reiserfs /dev/mapper/mycrypt
resize_reiserfs 3.6.19 (2003 www.namesys.com)
ReiserFS report:
blocksize 4096
block count 51200 (25600)
free blocks 25599 (0)
bitmap block count 2 (1)
Syncing..done
resize_reiserfs: Resizing finished successfully.
slap steph # mount /dev/mapper/mycrypt cryptmounts
slap steph # dd if=/dev/zero >> cryptmount/zeroes
dd: writing to `standard output': No space left on device
204593+0 records in
204592+0 records out
104751104 bytes (105 MB) copied, 4.85683 s, 21.6 MB/s
slap steph # ls -l cryptmount/zeroes
-rw-r--r-- 1 root root 175898624 Jun 2 00:27 cryptmount/zeroes
slap steph # df cryptmount
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/mycrypt 204788 204788 0 100% /home/steph/cryptmount
Resetting loop works, as expected - no new information discovered.
Resize /dev/loop3
slap steph # umount cryptmount
slap steph # dd if=/dev/urandom bs=1M count=100 >> /dev/loop3
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 28.5788 s, 3.7 MB/s
slap steph # cryptsetup resize mycrypt
slap steph # resize_reiserfs /dev/mapper/mycrypt
resize_reiserfs 3.6.19 (2003 www.namesys.com)
reiserfs_open: the reiserfs superblock cannot be found on /dev/mapper/mycrypt.
Reiserfs can’t find filesystem. Recreate crypt and try again…
slap steph # cryptsetup remove mycrypt
slap steph # cryptsetup -c serpent -s 256 create mycrypt /dev/loop3
Enter passphrase:
slap steph # mount /dev/mapper/mycrypt cryptmount
mount: you must specify the filesystem type
slap steph # resize_reiserfs /dev/mapper/mycrypt
resize_reiserfs 3.6.19 (2003 www.namesys.com)
reiserfs_open: the reiserfs superblock cannot be found on /dev/mapper/mycrypt.
Filesystem lost. Resizing /dev/loop3 while active is a desctructive action.
Conclusion
Can’t find any discernible changes made by ‘cryptsetup resize’. Can’t find way of resizing block device without recreateing loop hence recreating crypt (and we already know that resizing via this method already works). Must assume that ‘cryptsetup resize’ applies to block devices that can change size whilst being mapped. Perhaps partitions rather than files?
Resizing reiserfs crypt mounted with dm-crypt
Restart computer and enter incorrect password for crypt-bn.
Back up image bn.img!
Then…
slap home # umount /home/bn
umount: /home/bn: not mounted
slap home # dmsetup ls
crypt-steph (254, 3)
crypt-swap (254, 0)
crypt-bn (254, 2)
crypt-tmp (254, 1)
slap home # cryptsetup remove crypt-bn
slap home # dmsetup ls
crypt-steph (254, 3)
crypt-swap (254, 0)
crypt-tmp (254, 1)
slap home # losetup -a
/dev/loop0: [0808]:942290 (/tmp.img)
/dev/loop1: [0808]:946234 (/home/bn.img)
/dev/loop2: [0808]:344097 (/home/steph.img)
/dev/loop/0: [0808]:942290 (/tmp.img)
/dev/loop/1: [0808]:946234 (/home/bn.img)
/dev/loop/2: [0808]:344097 (/home/steph.img)
slap home # losetup -d /dev/loop1
slap home # losetup -a
/dev/loop0: [0808]:942290 (/tmp.img)
/dev/loop2: [0808]:344097 (/home/steph.img)
/dev/loop/0: [0808]:942290 (/tmp.img)
/dev/loop/2: [0808]:344097 (/home/steph.img)
slap home # losetup -f
/dev/loop1
slap home # losetup /dev/loop1 /home/bn.img
slap home # cryptsetup -y -c serpent -s 256 create crypt-bn /dev/loop1
Enter passphrase:
Verify passphrase:
slap home # resize_reiserfs /dev/mapper/crypt-bn
resize_reiserfs 3.6.19 (2003 www.namesys.com)
ReiserFS report:
blocksize 4096
block count 2066432 (1280000)
free blocks 803801 (17393)
bitmap block count 64 (40)
Syncing..done
resize_reiserfs: Resizing finished successfully.
slap home # mount /dev/mapper/crypt-bn /home/bn
slap home # df -lh /home/bn
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/crypt-bn 7.9G 4.9G 3.1G 62% /home/bn
