goathtool

goathtool README

Synopsis

goathtool attempts reproduces the functionality of nongnu.org's oathtool http://www.nongnu.org/oath-toolkit/man-oathtool.html. How incompletely is to be determined. The intent is to implement the functionality the primary author uses most and then -- as time or PRs occur -- to fill in more of the features. The author also intends to differ in implementation of defaults and invocation.

goathtool will only implement the short flags as the author intends to forgo 3rd party libraries.

Description

goathtool

Generate OATH one-time passwords (OTP).

Examples

The following examples are borrowed/stolen from the oathtool man page and are therefore: Copyright © 2013 Simon Josefsson. License GPLv3+: GNU GPL version 3 or later http://gnu.org/licenses/gpl.html.

The commands have been modified to use the syntax goathtool uses.

To generate the first event-based (HOTP) one-time password for an all-zero key:

$ goathtool hotp 00
328482
$

Sometime you want to generate more than a single OTP. To generate 10 additional event-based one-time pass‐ words, with the secret key used in the examples of RFC 4226, use the -w (--window) parameter:

$ goathtool hotp -w 10 3132333435363738393031323334353637383930
755224
287082
359152
969429
338314
254676
287922
162583
399871
520489
403154
$

In the last output, the counter for the first OTP was 0, the second OTP had a counter of 1, and so on up to 10.

In order to use keys encoded in Base32 instead of hex, you may provide the -b (--base32) parameter:

$ goathtool hotp -b -w 3 GEZDGNBVGY3TQOJQGEZDGNBVGY3TQOJQ
755224
287082
359152
969429
$

The tool ignore whitespace in base32 data and re-add padding if necessary, thus you may supply keys format‐ ted like the one below.

$ goathtool totp -b  "gr6d 5br7 25s6 vnck v4vl hlao re"
977872
$

To generate a particular OTP, use the -c (--counter) parameter to give the exact position directly:

$ goathtool hotp -c 5 3132333435363738393031323334353637383930
254676
$

To validate a HOTP one-time password supply the OTP last on the command line:

$ goathtool hotp -w 10 3132333435363738393031323334353637383930 969429
3
$

The output indicates the counter that was used. It works by starting with counter 0 and increment until it founds a match (or not), within the supplied window of 10 OTPs.

The tool supports time-variant one-time passwords, in so called TOTP mode. Usage is similar, but --totp needs to be provided:

$ goathtool totp 00
943388
$

Don't be alarmed if you do not get the same output, this is because the output is time variant. To gener‐ ate a TOTP for a particular fixed time use the -N (--now) parameter:

$ goathtool totp -N "2008-04-23 17:42:17 UTC" 00
974945
$

The format is a mostly free format human readable date string such as "Sun, 29 Feb 2004 16:21:42 -0800" or "2004-02-29 16:21:42" or even "next Thursday". It is the same used as the --date parameter of the date(1) tool.

You may generate several TOTPs by specifying the --window parameter, similar to how it works for HOTP. The OTPs generated here will be for the initial time (normally current time) and then each following time step (e.g., 30 second window).

$ goathtool totp -w 5 00
815120
003818
814756
184042
582326
733842
$

You can validate a TOTP one-time password by supplying the secret and a window parameter (number of time steps before or after current time):

$ goathtool totp -w 5 00 `goathtool --totp 00`
0 # NB: this currently returns the counter not the item in the window that was found.
$

Similar when generating TOTPs, you can use a -N (--now) parameter to specify the time to use instead of the current time:

$  goathtool totp -d 8 -N "2005-03-18 01:58:29 UTC" -w 10000000 3132333435363738393031323334353637383930 89005924
4115227 # NB: this also returns a different number also because it returns the counter not the window item that matched
$

The previous test uses values from the TOTP specification and will stress test the tool because the expected window is around 4 million time-steps.

There are two system parameters for TOTP: the time-step size and the time start.

By default the time-step size is 30 seconds, which means you get a new OTP every 30 seconds. You may mod‐ ify this with the -s (--time-step-size) parameter:

$ goathtool totp -s 45 00
109841 # time based doesn't validate
$

The values are valid ISO-8601 durations, see: http://en.wikipedia.org/wiki/ISO_8601#Durations

The time start is normally 1970-01-01 00:00:00 UTC but you may change it using the -S (--start-time):

$ goathtool totp -S "1980-01-01 00:00:00 UTC" 00
273884 # time based doesnt' validate
$

To get more information about what the tool is using use the -v (--verbose) parameter. Finally, to gener‐ ate the last TOTP (for SHA-1) in the test vector table of draft-mraihi-totp-timebased-07 you can invoke the tool like this:

$ goathtool totp -v -N "2033-05-18 03:33:20 UTC" -d 8 3132333435363738393031323334353637383930
Hex secret: 3132333435363738393031323334353637383930
Base32 secret: GEZDGNBVGY3TQOJQGEZDGNBVGY3TQOJQ
Digits: 8
Window size: 0
Step size (seconds): 30
Start time: 1970-01-01 00:00:00 UTC (0)
Time now: 2033-05-18 03:33:20 UTC (2000000000)
Counter: 0x3F940AA (66666666)

69279037
$

In the last one the authoer only outputs either the hex or base32 secret that is provided.

To Do

• LICENSE
• COPYRIGHT
• Flags - outline basic flags
  • common flags
    • -b base32
    • -d number of digits in the OTP
    • -w window of counter values to test
  • hotp flags
    • -c counter
  • totp flags
    • -s time-step duration
    • -N time to use as current time
    • -S time to start counting steps from (epoch)
• subcommand switch (hotp, totp)
• implement hotp
• implement totp using hotp
• ignore whitespace
• autopad base32 strings
• tests
• examples
• godoc
• add relevant docs and installation to README
• fix totp validation to return the item from the window that matched not the abused counter
• don't abuse counter AKA refactor