oath_totp_validate4_callback man page on DragonFly

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oath_totp_validate4_callback(3)	    liboath    oath_totp_validate4_callback(3)

NAME
       oath_totp_validate4_callback - API function

SYNOPSIS
       #include <oath.h>

       int    oath_totp_validate4_callback(const   char	  *   secret,	size_t
       secret_length, time_t now, unsigned time_step_size,  time_t  start_off‐
       set,  unsigned  digits,	size_t	window,	 int  *	 otp_pos,  uint64_t  *
       otp_counter, int flags, oath_validate_strcmp_function strcmp_otp,  void
       * strcmp_handle);

ARGUMENTS
       const char * secret
		   the shared secret string

       size_t secret_length
		   length of secret

       time_t now  Unix time value to compute TOTP for

       unsigned time_step_size
		   time step system parameter (typically 30)

       time_t start_offset
		   Unix	 time  of when to start counting time steps (typically
		   0)

       unsigned digits
		   number of requested digits in the OTP

       size_t window
		   how many OTPs after start counter to test

       int * otp_pos
		   output search position in search window (may be NULL).

       uint64_t * otp_counter
		   counter value used to calculate OTP value (may be NULL).

       int flags   flags indicating mode, one of oath_totp_flags

       oath_validate_strcmp_function strcmp_otp
		   function pointer to a strcmp-like function.

       void * strcmp_handle
		   caller handle to be passed on to strcmp_otp.

DESCRIPTION
       Validate an OTP according to OATH TOTP algorithm per RFC 6238.

       Validation is implemented by generating a number of potential OTPs  and
       performing  a call to the strcmp_otp function, to compare the potential
       OTP against the given otp.  It has the following prototype:

       int  (*oath_validate_strcmp_function)   (void   *handle,	  const	  char
       *test_otp);

       The  function  should  be similar to strcmp in that it return 0 only on
       matches.	 It differs by permitting use  of  negative  return  codes  as
       indication of internal failures in the callback.	 Positive values indi‐
       cate OTP mismatch.

       This callback interface is useful when you cannot compare OTPs directly
       using  normal  strcmp,  but instead for example only have a hashed OTP.
       You would then typically pass in the hashed OTP	in  the	 strcmp_handle
       and  let	 your implementation of strcmp_otp hash the test_otp OTP using
       the same hash, and then compare the results.

       Currently only OTP lengths of 6, 7 or 8	digits	are  supported.	  This
       restrictions  may  be  lifted in future versions, although some limita‐
       tions are inherent in the protocol.

       The flags parameter may be used to change the MAC function, for example
       OATH_TOTP_HMAC_SHA256 or OATH_TOTP_HMAC_SHA512.

RETURNS
       Returns	absolute  value of position in OTP window (zero is first posi‐
       tion), or OATH_INVALID_OTP if no OTP was found in  OTP  window,	or  an
       error code.

SINCE
       2.6.0

REPORTING BUGS
       Report  bugs  to	 <oath-toolkit-help@nongnu.org>.   liboath  home page:
       http://www.gnu.org/software/liboath/ General help using	GNU  software:
       http://www.gnu.org/gethelp/

COPYRIGHT
       Copyright © 2009-2015 Simon Josefsson.
       Copying	and  distribution  of this file, with or without modification,
       are permitted in any medium  without  royalty  provided	the  copyright
       notice and this notice are preserved.

liboath				     2.6.1     oath_totp_validate4_callback(3)
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