NAME

       oath_totp_validate4 - API function

SYNOPSIS

       #include <oath.h>

       int  oath_totp_validate4(const  char  * secret, size_t secret_length, time_t now, unsigned
       time_step_size, time_t start_offset, size_t window, int * otp_pos, uint64_t * otp_counter,
       int flags, const char * otp);

ARGUMENTS

       const char * secret
                   the shared secret string

       size_t secret_length
                   length of secret

       time_t now  Unix time value to validate 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)

       size_t window
                   how many OTPs after/before start OTP 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

       const char * otp
                   the OTP to validate.

DESCRIPTION

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

       Currently  only  OTP  lengths of 6, 7 or 8 digits are supported.  This restrictions may be
       lifted in future versions, although some limitations 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  position),  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:
       https://www.nongnu.org/oath-toolkit/      General     help     using     GNU     software:
       http://www.gnu.org/gethelp/

COPYRIGHT

       Copyright © 2009-2020 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.