oath_totp_validate2_callback(3) liboath oath_totp_validate2_callback(3)
NAME
oath_totp_validate2_callback - API function
SYNOPSIS
#include <oath.h>
oath_totp_validate2_callback(3) 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
Copyright (C) 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.
liboath 2.6.7 oath_totp_validate2_callback(3)
oath-toolkit 2.6.7 - Generated Sat May 6 12:04:26 CDT 2023