plucky (3) oath_totp_validate2_callback.3.gz

Provided by: liboath-dev_2.6.11-3ubuntu1_amd64 bug

NAME
       oath_totp_validate2_callback - API function


SYNOPSIS
       #include <oath.h>

       int  oath_totp_validate2_callback(const  char  *  secret,  size_t  secret_length,  time_t  now,  unsigned
       time_step_size,   time_t   start_offset,   unsigned   digits,   size_t    window,    int    *    otp_pos,
       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).

       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
       indicate 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 limitations are inherent in the protocol.


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
       1.10.0


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 © 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.