Ubuntu Manpage: stenc - SCSI Tape Hardware Encryption Manager

NAME

       stenc - SCSI Tape Hardware Encryption Manager

SYNOPSIS

       stenc -g length -k file [-kd description]
       stenc -f device [--detail]
       stenc   -f  device  -e  on|mixed|rawread  [-a  index]  [-k  file]  [--ckod]  [--protect  |
       --unprotect]
       stenc -f device -e off [-a index] [--ckod] [--protect | --unprotect]
       stenc --version

AVAILABILITY

       Linux, AIX

DESCRIPTION

       Allows you to manage hardware encryption on SSP enabled tape devices (LTO4, LTO5, etc).

OPTIONS

-g length -k <file to save as> [-kd <key descriptor(uKAD)>]
Generates a key file of length (in bits) containing a random hexadecimal key. After
entering this option, you will be required to press random keys followed by the
enter key. This will seed the random number generator so that your key is more
secure. Specify the file to save the key into with the -k option (you will need
write permissions to that file location). Lastly you can enter an optional key
description using the -kd flag (see KEY DESCRIPTORS). This key file can then be
used with the -k option. You should not generate a key file over an unsecured
remote session. Typically, key files should be set to 256 bits (32 hexadecimal
bytes), however your device may only support 128 bits.

-f device

Specifies the device to use (i.e. /dev/nst0, /dev/rmt0.1, /dev/sg0). Use the lsscsi
command to determine the appropriate device to use. You should always use a device
name that does not rewind (i.e. use /dev/nst0 instead of /dev/st0, /dev/rmt0.1
instead of /dev/rmt0). Use commands like 'cat /proc/scsi/scsi', 'lsscsi', and
'lsdev' to determine the proper device to use. On some distros, a /dev/sg device
must be used instead of a /dev/st device.

If this is the only option specified, the status of the device will be displayed.
To retrieve more detailed status information, add --detail. If you are root and
the status command fails, either the device is incorrect (try another link to the
device: /dev/rmt0.1, /dev/nst0, /dev/tape, etc.), a tape may not be in the drive,
you may be using the wrong algorithm for the tape drive (see the -a option), or the
device does not support SCSI Security Protocol. stenc may read up to 100 blocks of
the tape, starting at the current position, in order to determine if the volume has
been encrypted. For this reason, you should not run the status command while
another process is accessing the drive. If the device returns Unable to determine
for the volume encryption status, you may need to move to a section of the tape
that contains data (i.e. mt -f <device> fsr <count>) or rewind the tape in order
for stenc to output the volume status.

-e on | mixed | rawread | off

Sets the encryption mode for the device specified with -f option. Successful
operations of this type will create an audit entry in the /var/log/stenc file. If
off is not specified and the -k option is not specified, the program will require
the user to enter a hexadecimal key (see KEY INPUT SYNTAX) and an optional key
description (see KEY DESCRIPTORS).

on - The drive will encrypt all data sent to it and will only output data it is
able to decrypt, ignoring unencrypted data on the drive.

mixed - The drive will encrypt all data sent to it and will output both encrypted
data and unencrypted data, providing the drive is able to do so.

rawread - The drive will encrypt all data sent to it and will output unencrypted
data and raw encrypted data. You will probably need to have specified --unprotect
when the data was written in order to read it with this option. Some drives do not
support this option. See the --protect option.

off - The drive will neither encrypt data sent to it, or decrypt encrypted data
found on the drive. If this command fails you may have switch your algorithm or
specify a different default key size when you configure the program

WARNING: The SCSI device will revert all encryption settings if the tape device is
power cycled (if the tape drive is extenal, it may keep the settings even if the
system is rebooted). You can modify you local startup script (/etc/rc.local,
/etc/rc, etc.) to set encryption at reboot if need be. If you do this, you will
need to use the -k option to prevent the system from waiting on the local console
user to enter the encryption key.

-a index

Only valid when setting encryption (see the -e option). Specifies the algorithm
index to use for the device (defaults to 0, which can be changed using the --with-
default-algorithm configure option). Setting encryption on/off may fail on some
devices if this is not the correct algorithm for the drive (i.e. HP drives use an
algorithm index of 1).

--ckod

Only valid when setting encryption (see the -e option). Instructs the drive to
clear its encryption keys when the volume is unmounted instead of keeping it until
the drive is power cycled. Some devices may not support this option.

--protect | --unprotect

Only valid when setting encryption (see the -e option). Instructs the drive to
protect or unprotect any encrypted data from being raw read. See the -e rawread
option. Some devices may not support these options.

-k file

Only valid when turning encryption on (see the -e option) or generating a new key
(see the -g option). When turning encryption on, this specifies the location of a
key file previously generated with the -g option. When generating a new key with
the -g option, this specifies the key file that the new key will be saved into.
Key files should be owned by root ('chown root') and only readable by root ('chmod
600'). stenc automatically chmods key files generated with the -g option.

KEY INPUT SYNTAX

       All  keys  should  be  a maximum of 256 bits (32 bytes).  stenc requires that all keys are
       entered using 2 digit hexadecimal bytes, with no delimiters  in  between  bytes.   Do  not
       precede  your  key  input  with '0x'. If you try to use a key size that the drive does not
       support, the command will error. When using a key file, the second line in  the  file  can
       contain an optional key description that will be displayed with the device status (see the
       -f option).

       Example 128 bit Key:
              000102030405060708090a0b0c0d0e0f

       Example 256 bit Key:
              000102030405060708090a0b0c0d0e0f000102030405060708090a0b0c0d0e0f

EXAMPLE

       stenc -g 256 -k /etc/tape.key -kd "September Tape Key"
              Generate a random 256 bit key file with the description "September  Tape  Key"  and
              save it into /etc/tape.key

       stenc -f /dev/st0 -e on -k /etc/stenc.key
              Turns on encryption on /dev/st0 using the key contained in /etc/stenc.key

       stenc -f /dev/st0 -e on
              Asks  user  to  input  a key in hexadecimal format and then turns on encryption for
              /dev/st0 using that key

       stenc -f /dev/st0 -e off
              Turns off encryption for /dev/st0

       stenc -f /dev/st0 --detail
              Outputs the detailed encryption status of /dev/st0

       tail /var/log/stenc
              Lists the last few key change audit entries

KEY CHANGE AUDITING

       Each time a key is changed using this program, a corresponding entry will be entered  into
       the /var/log/stenc file.  These entries will have an Key Instance Counter corresponding to
       the counter listed in the device status (see the -f option).  Each time the key is set,  a
       checksum  of that key (or a key description) is also listed in this file.  This allows you
       to know when keys were changed and if the key you are using is the same as a prior key. If
       an unauthorized party would compromise this log file, your key security would be decreased
       if checksums were present in the log.  To prevent this, you  should  use  key  descriptors
       instead of checksums (see KEY DESCRIPTORS).

KEY DESCRIPTORS

       Key  descriptors are set when using the -g option or the -e option. They will be displayed
       when retrieving the drive status (see the -f option). These descriptors will be written to
       the volume, so they should NEVER contain information that would reduce the security of the
       key (i.e. a checksum, bitlength, algorithm, a portion of the key). If stenc  detects  that
       the  volume  is encrypted but it cannot decrypt the data, the key descriptor on the volume
       will be displayed as part of the device status.  This can be useful for determining  which
       key goes to which volume.

AUTHOR

       Written by John Coleman and Samuel Martinez Jr. of SunWest Educational Credit Union.

REPORTING BUGS

       Report stenc bugs to jcoleman1981@live.com.

PROJECT UPDATES

       Visit http://sourceforge.net/projects/stenc/ for more information.

COPYRIGHT

       Copyright    2012    contributing    authors.   License   GPLv2:   GNU   GPL   version   2
       <http://gnu.org/licenses/gpl.html>. This is free software: you are free  to   change   and
       redistribute it. There is NO WARRANTY, to the extent permitted by law.