FIDO_CRED_EXCLUDE(3) | Library Functions Manual | FIDO_CRED_EXCLUDE(3)

# NAME

`fido_cred_exclude` — appends a credential ID to a credential's list of excluded credentials

# SYNOPSIS

library “libfido2” libcbor libcrypto libz
`#include <fido.h>`

int
`fido_cred_exclude`(fido_cred_t *cred, const unsigned char *ptr, size_t len);

# DESCRIPTION

The `fido_cred_exclude`() function adds ptr to the list of credentials excluded by cred, where ptr points to a credential ID of len bytes. A copy of ptr is made, and no references to the passed pointer are kept. If `fido_cred_exclude`() fails, the existing list of excluded credentials is preserved.

If `fido_cred_exclude` returns success and cred is later passed to fido_dev_make_cred(3) on a device that contains the credential denoted by ptr, then fido_dev_make_cred(3) will fail.

For the format of a FIDO2 credential ID, please refer to the Web Authentication (webauthn) standard.

# RETURN VALUES

The error codes returned by `fido_cred_exclude`() are defined in `<fido/err.h>`. On success, `FIDO_OK` is returned.

# SEE ALSO

fido_cred_new(3), fido_cred_set_authdata(3), fido_dev_make_cred(3)

July 9, 2025 | Debian