oath

oath

Synopsis

#define             OATHAPI
#define             OATH_VERSION
#define             OATH_VERSION_NUMBER
enum                oath_rc;
int                 oath_init                           (void);
int                 oath_done                           (void);
const char *        oath_check_version                  (const char *req_version);
int                 oath_hex2bin                        (char *hexstr,
                                                         char *binstr,
                                                         size_t *binlen);
const char *        oath_strerror                       (int err);
const char *        oath_strerror_name                  (int err);
#define             OATH_HOTP_LENGTH                    (digits,
                                                         checksum)
#define             OATH_HOTP_DYNAMIC_TRUNCATION
int                 oath_hotp_generate                  (const char *secret,
                                                         size_t secret_length,
                                                         uint64_t moving_factor,
                                                         unsigned  digits,
                                                         bool add_checksum,
                                                         size_t truncation_offset,
                                                         char *output_otp);
int                 oath_hotp_validate                  (const char *secret,
                                                         size_t secret_length,
                                                         uint64_t start_moving_factor,
                                                         size_t window,
                                                         const char *otp);
int                 (*oath_validate_strcmp_function)    (void *handle,
                                                         const char *test_otp);
#define             oath_hotp_validate_strcmp_function
int                 oath_hotp_validate_callback         (const char *secret,
                                                         size_t secret_length,
                                                         uint64_t start_moving_factor,
                                                         size_t window,
                                                         unsigned  digits,
                                                         oath_validate_strcmp_function strcmp_otp,
                                                         void *strcmp_handle);
#define             OATH_TOTP_DEFAULT_TIME_STEP_SIZE
#define             OATH_TOTP_DEFAULT_START_TIME
int                 oath_totp_generate                  (const char *secret,
                                                         size_t secret_length,
                                                         time_t now,
                                                         unsigned  time_step_size,
                                                         time_t start_offset,
                                                         unsigned  digits,
                                                         char *output_otp);
int                 oath_totp_validate                  (const char *secret,
                                                         size_t secret_length,
                                                         time_t now,
                                                         unsigned  time_step_size,
                                                         time_t start_offset,
                                                         size_t window,
                                                         const char *otp);
int                 oath_totp_validate_callback         (const char *secret,
                                                         size_t secret_length,
                                                         time_t now,
                                                         unsigned  time_step_size,
                                                         time_t start_offset,
                                                         unsigned  digits,
                                                         size_t window,
                                                         oath_validate_strcmp_function strcmp_otp,
                                                         void *strcmp_handle);
int                 oath_authenticate_usersfile         (const char *usersfile,
                                                         const char *username,
                                                         const char *otp,
                                                         size_t window,
                                                         const char *passwd,
                                                         time_t *last_otp);

Description

Details

OATHAPI

#define             OATHAPI


OATH_VERSION

#define OATH_VERSION "1.8.2"

Pre-processor symbol with a string that describe the header file version number. Used together with oath_check_version() to verify header file and run-time library consistency.


OATH_VERSION_NUMBER

#define OATH_VERSION_NUMBER 0x01080200

Pre-processor symbol with a hexadecimal value describing the header file version number. For example, when the header version is 1.2.3 this symbol will have the value 0x01020300. The last two digits are only used between public releases, and will otherwise be 00.


enum oath_rc

typedef enum
{
  OATH_OK = 0,
  OATH_CRYPTO_ERROR = -1,
  OATH_INVALID_DIGITS = -2,
  OATH_PRINTF_ERROR = -3,
  OATH_INVALID_HEX = -4,
  OATH_TOO_SMALL_BUFFER = -5,
  OATH_INVALID_OTP = -6,
  OATH_REPLAYED_OTP = -7,
  OATH_BAD_PASSWORD = -8,
  OATH_INVALID_COUNTER = -9,
  OATH_INVALID_TIMESTAMP = -10,
  OATH_NO_SUCH_FILE = -11,
  OATH_UNKNOWN_USER = -12,
  OATH_FILE_SEEK_ERROR = -13,
  OATH_FILE_CREATE_ERROR = -14,
  OATH_FILE_LOCK_ERROR = -15,
  OATH_FILE_RENAME_ERROR = -16,
  OATH_FILE_UNLINK_ERROR = -17,
  OATH_TIME_ERROR = -18
} oath_rc;

Return codes for OATH functions. All return codes are negative except for the successful code OATH_OK which are guaranteed to be 0. Positive values are reserved for non-error return codes.

Note that the oath_rc enumeration may be extended at a later date to include new return codes.

OATH_OK

Successful return

OATH_CRYPTO_ERROR

Internal error in crypto functions

OATH_INVALID_DIGITS

Unsupported number of OTP digits

OATH_PRINTF_ERROR

Error from system printf call

OATH_INVALID_HEX

Hex string is invalid

OATH_TOO_SMALL_BUFFER

The output buffer is too small

OATH_INVALID_OTP

The OTP is not valid

OATH_REPLAYED_OTP

The OTP has been replayed

OATH_BAD_PASSWORD

The password does not match

OATH_INVALID_COUNTER

The counter value is corrupt

OATH_INVALID_TIMESTAMP

The timestamp is corrupt

OATH_NO_SUCH_FILE

The supplied filename does not exist

OATH_UNKNOWN_USER

Cannot find information about user

OATH_FILE_SEEK_ERROR

System error when seeking in file

OATH_FILE_CREATE_ERROR

System error when creating file

OATH_FILE_LOCK_ERROR

System error when locking file

OATH_FILE_RENAME_ERROR

System error when renaming file

OATH_FILE_UNLINK_ERROR

System error when removing file

OATH_TIME_ERROR

System error for time manipulation

oath_init ()

int                 oath_init                           (void);

This function initializes the OATH library. Every user of this library needs to call this function before using other functions. You should call oath_done() when use of the OATH library is no longer needed.

Note that this function may also initialize Libgcrypt, if the OATH library is built with libgcrypt support and libgcrypt has not been initialized before. Thus if you want to manually initialize libgcrypt you must do it before calling this function. This is useful in cases you want to disable libgcrypt's internal lockings etc.

Returns :

On success, OATH_OK (zero) is returned, otherwise an error code is returned.

oath_done ()

int                 oath_done                           (void);

This function deinitializes the OATH library, which were initialized using oath_init(). After calling this function, no other OATH library function may be called except for to re-initialize the library using oath_init().

Returns :

On success, OATH_OK (zero) is returned, otherwise an error code is returned.

oath_check_version ()

const char *        oath_check_version                  (const char *req_version);

Check OATH library version.

See OATH_VERSION for a suitable req_version string.

This function is one of few in the library that can be used without a successful call to oath_init().

req_version :

version string to compare with, or NULL.

Returns :

Check that the version of the library is at minimum the one given as a string in req_version and return the actual version string of the library; return NULL if the condition is not met. If NULL is passed to this function no check is done and only the version string is returned.

oath_hex2bin ()

int                 oath_hex2bin                        (char *hexstr,
                                                         char *binstr,
                                                         size_t *binlen);

Convert string with hex data to binary data.

Non-hexadecimal data are not ignored but instead will lead to an OATH_INVALID_HEX error.

If binstr is NULL, then binlen will be populated with the necessary length. If the binstr buffer is too small, OATH_TOO_SMALL_BUFFER is returned and binlen will contain the necessary length.

hexstr :

input string with hex data

binstr :

output string that holds binary data, or NULL

binlen :

output variable holding needed length of binstr

Returns :

On success, OATH_OK (zero) is returned, otherwise an error code is returned.

oath_strerror ()

const char *        oath_strerror                       (int err);

Convert return code to human readable string explanation of the reason for the particular error code.

This string can be used to output a diagnostic message to the user.

This function is one of few in the library that can be used without a successful call to oath_init().

err :

liboath error code

Returns :

Returns a pointer to a statically allocated string containing an explanation of the error code err.

Since 1.8.0


oath_strerror_name ()

const char *        oath_strerror_name                  (int err);

Convert return code to human readable string representing the error code symbol itself. For example, oath_strerror_name(OATH_OK) returns the string "OATH_OK".

This string can be used to output a diagnostic message to the user.

This function is one of few in the library that can be used without a successful call to oath_init().

err :

liboath error code

Returns :

Returns a pointer to a statically allocated string containing a string version of the error code err, or NULL if the error code is not known.

Since 1.8.0


OATH_HOTP_LENGTH()

#define OATH_HOTP_LENGTH(digits, checksum) (digits + (checksum ? 1 : 0))

digits :

checksum :


OATH_HOTP_DYNAMIC_TRUNCATION

#define OATH_HOTP_DYNAMIC_TRUNCATION SIZE_MAX


oath_hotp_generate ()

int                 oath_hotp_generate                  (const char *secret,
                                                         size_t secret_length,
                                                         uint64_t moving_factor,
                                                         unsigned  digits,
                                                         bool add_checksum,
                                                         size_t truncation_offset,
                                                         char *output_otp);

Generate a one-time-password using the HOTP algorithm as described in RFC 4226.

Use a value of OATH_HOTP_DYNAMIC_TRUNCATION for truncation_offset unless you really need a specific truncation offset.

To find out the size of the OTP you may use the OATH_HOTP_LENGTH() macro. The output_otp buffer must be have room for that length plus one for the terminating NUL.

Currently only values 6, 7 and 8 for digits are supported, and the add_checksum value is ignored. These restrictions may be lifted in future versions, although some limitations are inherent in the protocol.

secret :

the shared secret string

secret_length :

length of secret

moving_factor :

a counter indicating the current OTP to generate

digits :

number of requested digits in the OTP, excluding checksum

add_checksum :

whether to add a checksum digit or not

truncation_offset :

use a specific truncation offset

output_otp :

output buffer, must have room for the output OTP plus zero

Returns :

On success, OATH_OK (zero) is returned, otherwise an error code is returned.

oath_hotp_validate ()

int                 oath_hotp_validate                  (const char *secret,
                                                         size_t secret_length,
                                                         uint64_t start_moving_factor,
                                                         size_t window,
                                                         const char *otp);

Validate an OTP according to OATH HOTP algorithm per RFC 4226.

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.

secret :

the shared secret string

secret_length :

length of secret

start_moving_factor :

start counter in OTP stream

window :

how many OTPs after start counter to test

otp :

the OTP to validate.

Returns :

Returns position in OTP window (zero is first position), or OATH_INVALID_OTP if no OTP was found in OTP window, or an error code.

oath_validate_strcmp_function ()

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

Prototype of strcmp-like function that will be called by oath_hotp_validate_callback() or oath_totp_validate_callback() to validate OTPs.

The function should behave like strcmp, i.e., only ever return 0 on matches.

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 oath_strcmp hash the test_otp OTP using the same hash, and then compare the results.

handle :

caller handle as passed to oath_hotp_validate_callback()

test_otp :

OTP to match against.

Returns :

0 if and only if test_otp is identical to the OTP to be validated.

Since 1.6.0


oath_hotp_validate_strcmp_function

#define oath_hotp_validate_strcmp_function oath_validate_strcmp_function


oath_hotp_validate_callback ()

int                 oath_hotp_validate_callback         (const char *secret,
                                                         size_t secret_length,
                                                         uint64_t start_moving_factor,
                                                         size_t window,
                                                         unsigned  digits,
                                                         oath_validate_strcmp_function strcmp_otp,
                                                         void *strcmp_handle);

Validate an OTP according to OATH HOTP algorithm per RFC 4226.

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 behave like strcmp, i.e., only ever return 0 on matches.

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.

secret :

the shared secret string

secret_length :

length of secret

start_moving_factor :

start counter in OTP stream

window :

how many OTPs after start counter to test

digits :

number of requested digits in the OTP

strcmp_otp :

function pointer to a strcmp-like function.

strcmp_handle :

caller handle to be passed on to strcmp_otp.

Returns :

Returns 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 1.4.0


OATH_TOTP_DEFAULT_TIME_STEP_SIZE

#define OATH_TOTP_DEFAULT_TIME_STEP_SIZE 30


OATH_TOTP_DEFAULT_START_TIME

#define OATH_TOTP_DEFAULT_START_TIME		((time_t) 0)


oath_totp_generate ()

int                 oath_totp_generate                  (const char *secret,
                                                         size_t secret_length,
                                                         time_t now,
                                                         unsigned  time_step_size,
                                                         time_t start_offset,
                                                         unsigned  digits,
                                                         char *output_otp);

Generate a one-time-password using the time-variant TOTP algorithm described in draft-mraihi-totp-timebased-07. The input parameters are taken as time values.

The system parameter time_step_size describes how long the time window for each OTP is. The recommended value is 30 seconds, and you can use the value 0 or the symbol OATH_TOTP_DEFAULT_TIME_STEP_SIZE to indicate this.

The system parameter start_offset denote the Unix time when time steps are started to be counted. The recommended value is 0, to fall back on the Unix epoch) and you can use the symbol OATH_TOTP_DEFAULT_START_TIME to indicate this.

The output_otp buffer must have room for at least digits characters, plus one for the terminating NUL.

Currently only values 6, 7 and 8 for digits are supported. This restriction may be lifted in future versions.

secret :

the shared secret string

secret_length :

length of secret

now :

Unix time value to compute TOTP for

time_step_size :

time step system parameter (typically 30)

start_offset :

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

digits :

number of requested digits in the OTP, excluding checksum

output_otp :

output buffer, must have room for the output OTP plus zero

Returns :

On success, OATH_OK (zero) is returned, otherwise an error code is returned.

Since 1.4.0


oath_totp_validate ()

int                 oath_totp_validate                  (const char *secret,
                                                         size_t secret_length,
                                                         time_t now,
                                                         unsigned  time_step_size,
                                                         time_t start_offset,
                                                         size_t window,
                                                         const char *otp);

Validate an OTP according to OATH TOTP algorithm per draft-mraihi-totp-timebased-07.

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.

secret :

the shared secret string

secret_length :

length of secret

now :

Unix time value to validate TOTP for

time_step_size :

time step system parameter (typically 30)

start_offset :

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

window :

how many OTPs after/before start OTP to test

otp :

the OTP to validate.

Returns :

Returns 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 1.6.0


oath_totp_validate_callback ()

int                 oath_totp_validate_callback         (const char *secret,
                                                         size_t secret_length,
                                                         time_t now,
                                                         unsigned  time_step_size,
                                                         time_t start_offset,
                                                         unsigned  digits,
                                                         size_t window,
                                                         oath_validate_strcmp_function strcmp_otp,
                                                         void *strcmp_handle);

Validate an OTP according to OATH TOTP algorithm per draft-mraihi-totp-timebased-07.

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 behave like strcmp, i.e., only ever return 0 on matches.

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.

secret :

the shared secret string

secret_length :

length of secret

now :

Unix time value to compute TOTP for

time_step_size :

time step system parameter (typically 30)

start_offset :

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

digits :

number of requested digits in the OTP

window :

how many OTPs after start counter to test

strcmp_otp :

function pointer to a strcmp-like function.

strcmp_handle :

caller handle to be passed on to strcmp_otp.

Returns :

Returns 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 1.6.0


oath_authenticate_usersfile ()

int                 oath_authenticate_usersfile         (const char *usersfile,
                                                         const char *username,
                                                         const char *otp,
                                                         size_t window,
                                                         const char *passwd,
                                                         time_t *last_otp);

Authenticate user named username with the one-time password otp and (optional) password passwd. Credentials are read (and updated) from a text file named usersfile.

usersfile :

string with user credential filename, in UsersFile format

username :

string with name of user

otp :

string with one-time password to authenticate

window :

how many future OTPs to search

passwd :

string with password, or NULL to disable password checking

last_otp :

output variable holding last successful authentication

Returns :

On successful validation, OATH_OK is returned. If the supplied otp is the same as the last successfully authenticated one-time password, OATH_REPLAYED_OTP is returned and the timestamp of the last authentication is returned in last_otp. If the one-time password is not found in the indicated search window, OATH_INVALID_OTP is returned. Otherwise, an error code is returned.