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FIDO_DEV_SET_IO_FUNCTIONS(3)                          Library Functions Manual

NAME
     fido_dev_set_io_functions, fido_dev_set_sigmask, fido_dev_set_timeout,
     fido_dev_set_transport_functions, fido_dev_io_handle - FIDO2 device I/O
     interface

SYNOPSIS
     #include <fido.h>

     typedef void *fido_dev_io_open_t(const char *);
     typedef void  fido_dev_io_close_t(void *);
     typedef int   fido_dev_io_read_t(void *, unsigned char *, size_t, int);
     typedef int   fido_dev_io_write_t(void *, const unsigned char *, size_t);

     typedef struct fido_dev_io {
             fido_dev_io_open_t  *open;
             fido_dev_io_close_t *close;
             fido_dev_io_read_t  *read;
             fido_dev_io_write_t *write;
     } fido_dev_io_t;

     #ifdef _WIN32
     typedef int fido_sigset_t;
     #else
     typedef sigset_t fido_sigset_t;
     #endif

     typedef int   fido_dev_rx_t(struct fido_dev *,
                       uint8_t, unsigned char *, size_t, int);
     typedef int   fido_dev_tx_t(struct fido_dev *,
                       uint8_t, const unsigned char *, size_t);

     typedef struct fido_dev_transport {
             fido_dev_rx_t *rx;
             fido_dev_tx_t *tx;
     } fido_dev_transport_t;

     int
     fido_dev_set_io_functions(fido_dev_t *dev, const fido_dev_io_t *io);

     int
     fido_dev_set_sigmask(fido_dev_t *dev, const fido_sigset_t *sigmask);

     int
     fido_dev_set_timeout(fido_dev_t *dev, int ms);

     int
     fido_dev_set_transport_functions(fido_dev_t *dev,
         const fido_dev_transport_t *t);

     void *
     fido_dev_io_handle(const fido_dev_t *dev);

DESCRIPTION
     The fido_dev_set_io_functions() function sets the I/O handlers used by
     libfido2 to talk to dev.  By default, these handlers are set to the
     operating system's native HID or NFC interfaces.  They are defined as
     follows:

     fido_dev_open_t
             Receives a const char * holding a path and opens the
             corresponding device, returning a non-NULL opaque pointer on
             success and NULL on error.

     fido_dev_close_t
             Receives the opaque pointer returned by fido_dev_open_t and
             closes the device.

     fido_dev_read_t
             Reads a single transmission unit (HID report, APDU) from a
             device.  The first parameter is the opaque pointer returned by
             fido_dev_open_t.  The second parameter is the read buffer, and
             the third parameter is the read buffer size.  The fourth
             parameter is the number of milliseconds the caller is willing to
             sleep, should the call need to block.  If this value holds -1,
             fido_dev_read_t may block indefinitely.  On success, the number
             of bytes read is returned.  On error, -1 is returned.

     fido_dev_write_t
             Writes a single transmission unit (HID report, APDU) to dev.  The
             first parameter is the opaque pointer returned by
             fido_dev_open_t.  The second parameter is the write buffer, and
             the third parameter is the number of bytes to be written.  A
             fido_dev_write_t may block.  On success, the number of bytes
             written is returned.  On error, -1 is returned.

     When calling fido_dev_set_io_functions(), the open, close, read, and
     write fields of io may not be NULL.

     No references to io are held by fido_dev_set_io_functions().

     The fido_dev_set_sigmask() function may be used to specify a non-NULL
     signal mask sigmask to be used while libfido2's default I/O handlers wait
     on dev.  On UNIX-like operating systems, fido_sigset_t is defined as
     sigset_t.  On Windows, fido_sigset_t is defined as int and
     fido_dev_set_sigmask() is a no-op.

     No references to sigmask are held by fido_dev_set_sigmask().

     The fido_dev_set_timeout() function informs libfido2 not to block for
     more than ms milliseconds while communicating with dev.  If a timeout
     occurs, the corresponding fido_dev_* function will fail with FIDO_ERR_RX.
     If ms is -1, then libfido2 may block indefinitely.  This is the default
     behaviour.  When using the Windows Hello backend, ms is used as a
     guidance and may be overwritten by the platform.

     The fido_dev_set_transport_functions() function sets the transport
     functions used by libfido2 to talk to dev.  While the I/O handlers are
     responsible for sending and receiving transmission units of
     initialization and continuation packets already formatted by libfido2,
     the transport handlers are responsible for sending and receiving the
     CTAPHID commands and data directly, as defined in the FIDO Client to
     Authenticator Protocol (CTAP) standard.  They are defined as follows:

     fido_dev_tx_t
             Receives a device, a CTAPHID command to transmit, a data buffer
             to transmit, and the length of the data buffer.  On success, 0 is
             returned.  On error, -1 is returned.

     fido_dev_rx_t
             Receives a device, a CTAPHID command whose response the caller
             expects to receive, a data buffer to receive into, the size of
             the data buffer determining the maximum length of a response, and
             the maximum number of milliseconds to wait for a response.  On
             success, the number of bytes read into the data buffer is
             returned.  On error, -1 is returned.

     When transport functions are specified, libfido2 will use them instead of
     the read and write functions of the I/O handlers.  However, the I/O
     handlers must still be specified to open and close the device.

     The fido_dev_io_handle() function returns the opaque pointer returned by
     the open function of the I/O handlers.  This is useful mainly for the
     transport functions, which unlike the I/O handlers are passed the
     fido_dev_t pointer instead of the opaque I/O handle.

RETURN VALUES
     On success, fido_dev_set_io_functions(),
     fido_dev_set_transport_functions(), fido_dev_set_sigmask(), and
     fido_dev_set_timeout() return FIDO_OK.  On error, a different error code
     defined in <fido/err.h> is returned.

SEE ALSO
     fido_dev_info_manifest(3), fido_dev_open(3)

     Client to Authenticator Protocol (CTAP),
     https://fidoalliance.org/specs/fido-v2.1-ps-20210615/fido-client-to-authenticator-protocol-v2.1-ps-20210615.html,
     FIDO Alliance, 2021-06-15, Proposed Standard, Version 2.1.

NetBSD 10.99               $Mdocdate: May 25 2018 $               NetBSD 10.99