[dm-crypt] Offset/size issue during LUKS recovery.

Milan Broz gmazyland at gmail.com
Fri Jul 15 13:12:30 CEST 2016


On 07/15/2016 11:13 AM, Arno Wagner wrote:
> On Fri, Jul 15, 2016 at 02:52:35 CEST, Julio Cesar Faracco wrote:
>> Hi,
>>
>> Since I moved to the version 1.6.7 of cryptsetup, I started to have some problems to recovery a LUKS partition
>> using a LUKS header file and a valid passphrase.
>>
>> # cryptsetup luksDump my_header_file --debug
>> # Detected kernel Linux 3.10.0-327.13.1.el7.x86_64 x86_64.
>> # Reading LUKS header of size 1024 from device /tmp/my_header_file
>> # Key length 64, device size 8192 sectors, header size 4036 sectors.
> [...]
>> # # cryptsetup luksOpen /dev/loop0 my_enc_partition <<EOF
>> $(PASSWORD)
>> EOF
>> # Detected kernel Linux 3.10.0-327.13.1.el7.x86_64 x86_64.
>> # Reading LUKS header of size 1024 from device /tmp/my_header_file
>> # Key length 64, device size 4060 sectors, header size 4036 sectors.
> 
> I take it, the device is  8192 sectors, i.e. 4MB? 
> 
> If so, there seem to be a bug in device-size detection
> as used by luksOpen.

libcryptsetup uses  BLKGETSIZE64 ioctl as all other tools, so more likely is that
device-size is really 4MB :)

But if separate header is used then the debug output above mean device (or file image) size for the header image,
not the data device

I should probably change wording in this message...

Milan


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