FIDO_CRED_NEW(3)

NAME
fido_cred_new, fido_cred_free, fido_cred_payment, fido_cred_pin_minlen, fido_cred_prot, fido_cred_fmt, fido_cred_rp_id, fido_cred_rp_name, fido_cred_user_name, fido_cred_display_name, fido_cred_authdata_ptr, fido_cred_authdata_raw_ptr, fido_cred_clientdata_hash_ptr, fido_cred_id_ptr, fido_cred_aaguid_ptr, fido_cred_hmac_secret_ptr, fido_cred_largeblob_key_ptr, fido_cred_pubkey_ptr, fido_cred_sig_ptr, fido_cred_user_id_ptr, fido_cred_x5c_list_count, fido_cred_x5c_list_ptr, fido_cred_x5c_ptr, fido_cred_attstmt_ptr, fido_cred_authdata_len, fido_cred_authdata_raw_len, fido_cred_clientdata_hash_len, fido_cred_id_len, fido_cred_aaguid_len, fido_cred_hmac_secret_len, fido_cred_largeblob_key_len, fido_cred_pubkey_len, fido_cred_sig_len, fido_cred_user_id_len, fido_cred_x5c_list_len, fido_cred_x5c_len, fido_cred_attstmt_len, fido_cred_entattest, fido_cred_type, fido_cred_flags, fido_cred_sigcount - FIDO2 credential API

SYNOPSIS
#include <fido.h>
fido_cred_t *
fido_cred_new(void);
void
fido_cred_free(fido_cred_t **cred_p);
bool
fido_cred_payment(const fido_cred_t *cred);
size_t
fido_cred_pin_minlen(const fido_cred_t *cred);
int
fido_cred_prot(const fido_cred_t *cred);
const char *
fido_cred_fmt(const fido_cred_t *cred);
const char *
fido_cred_rp_id(const fido_cred_t *cred);
const char *
fido_cred_rp_name(const fido_cred_t *cred);
const char *
fido_cred_user_name(const fido_cred_t *cred);
const char *
fido_cred_display_name(const fido_cred_t *cred);
const unsigned char *
fido_cred_authdata_ptr(const fido_cred_t *cred);
const unsigned char *
fido_cred_authdata_raw_ptr(const fido_cred_t *cred);
const unsigned char *
fido_cred_clientdata_hash_ptr(const fido_cred_t *cred);
const unsigned char *
fido_cred_id_ptr(const fido_cred_t *cred);
const unsigned char *
fido_cred_aaguid_ptr(const fido_cred_t *cred);
const unsigned char *
fido_cred_hmac_secret_ptr(const fido_cred_t *cred);
const unsigned char *
fido_cred_largeblob_key_ptr(const fido_cred_t *cred);
const unsigned char *
fido_cred_pubkey_ptr(const fido_cred_t *cred);
const unsigned char *
fido_cred_sig_ptr(const fido_cred_t *cred);
const unsigned char *
fido_cred_user_id_ptr(const fido_cred_t *cred);
size_t
fido_cred_x5c_list_count(const fido_cred_t *cred);
const unsigned char *
fido_cred_x5c_list_ptr(const fido_cred_t *cred, size_t idx);
const unsigned char *
fido_cred_x5c_ptr(const fido_cred_t *cred);
const unsigned char *
fido_cred_attstmt_ptr(const fido_cred_t *cred);
size_t
fido_cred_authdata_len(const fido_cred_t *cred);
size_t
fido_cred_authdata_raw_len(const fido_cred_t *cred);
size_t
fido_cred_clientdata_hash_len(const fido_cred_t *cred);
size_t
fido_cred_id_len(const fido_cred_t *cred);
size_t
fido_cred_aaguid_len(const fido_cred_t *cred);
size_t
fido_cred_hmac_secret_len(const fido_cred_t *cred);
size_t
fido_cred_largeblob_key_len(const fido_cred_t *cred);
size_t
fido_cred_pubkey_len(const fido_cred_t *cred);
size_t
fido_cred_sig_len(const fido_cred_t *cred);
size_t
fido_cred_user_id_len(const fido_cred_t *cred);
size_t
fido_cred_x5c_list_len(const fido_cred_t *cred, size_t idx);
size_t
fido_cred_x5c_len(const fido_cred_t *cred);
size_t
fido_cred_attstmt_len(const fido_cred_t *cred);
bool
fido_cred_entattest(const fido_cred_t *cred);
int
fido_cred_type(const fido_cred_t *cred);
uint8_t
fido_cred_flags(const fido_cred_t *cred);
uint32_t
fido_cred_sigcount(const fido_cred_t *cred);

DESCRIPTION
FIDO2 credentials are abstracted in libfido2 by the fido_cred_t type. The functions described in this page allow a fido_cred_t type to be allocated, deallocated, and inspected. For other operations on fido_cred_t, please refer to fido_cred_set_authdata(3), fido_cred_exclude(3), fido_cred_verify(3), and fido_dev_make_cred(3).

The fido_cred_new() function returns a pointer to a newly allocated, empty fido_cred_t type. If memory cannot be allocated, NULL is returned.

The fido_cred_free() function releases the memory backing *cred_p, where *cred_p must have been previously allocated by fido_cred_new(). On return, *cred_p is set to NULL. Either cred_p or *cred_p may be NULL, in which case fido_cred_free() is a NOP.

If the CTAP 2.2 FIDO_EXT_PAYMENT extension is enabled on cred, then the fido_cred_payment() function returns true. Since the extension has no output, the fido_cred_payment() function is only useful if cred was retrieved via fido_credman_rk(3).

If the CTAP 2.1 FIDO_EXT_MINPINLEN extension is enabled on cred, then the fido_cred_pin_minlen() function returns the minimum PIN length of cred. Otherwise, fido_cred_pin_minlen() returns zero. See fido_cred_set_pin_minlen(3) on how to enable this extension.

If the CTAP 2.1 FIDO_EXT_CRED_PROTECT extension is enabled on cred, then the fido_cred_prot() function returns the protection of cred. Otherwise, fido_cred_prot() returns zero. See fido_cred_set_prot(3) for the protection policies understood by libfido2.

The fido_cred_fmt() function returns a pointer to a NUL-terminated string containing the attestation statement format identifier of cred, or NULL if cred does not have a format set.

The fido_cred_rp_id(), fido_cred_rp_name(), fido_cred_user_name(), and fido_cred_display_name() functions return pointers to NUL-terminated strings holding the relying party ID, relying party name, user name, and user display name attributes of cred, or NULL if the respective entry is not set.

The fido_cred_authdata_ptr(), fido_cred_authdata_raw_ptr(), fido_cred_clientdata_hash_ptr(), fido_cred_id_ptr(), fido_cred_aaguid_ptr(), fido_cred_largeblob_key_ptr(), fido_cred_pubkey_ptr(), fido_cred_sig_ptr(), fido_cred_user_id_ptr(), fido_cred_x5c_ptr(), and fido_cred_attstmt_ptr() functions return pointers to the CBOR-encoded and raw authenticator data, client data hash, ID, authenticator attestation GUID, “largeBlobKey”, public key, signature, user ID, x509 leaf certificate, and attestation statement parts of cred, or NULL if the respective entry is not set.

The fido_cred_hmac_secret_ptr() function returns a pointer to the hmac-secret attribute of cred. The HMAC Secret MC Extension (hmac-secret-mc) is a CTAP 2.2 extension. Note that the resulting hmac-secret varies according to whether user verification was performed by the authenticator.

The fido_cred_authdata_len(), fido_cred_authdata_raw_len(), fido_cred_clientdata_hash_len(), fido_cred_id_len(), fido_cred_aaguid_len(), fido_cred_hmac_secret_len(), fido_cred_largeblob_key_len(), fido_cred_pubkey_len(), fido_cred_sig_len(), fido_cred_user_id_len(), fido_cred_x5c_len(), and fido_cred_attstmt_len() functions return the length of the given attribute.

The fido_cred_x5c_list_count() function returns the length of the x509 certificate chain in cred and the fido_cred_x5c_list_ptr() and fido_cred_x5c_list_len() functions return a pointer to and length of the x509 certificate at index idx respectively. Please note that the leaf certificate has an idx (index) value of 0 and calling fido_cred_x5c_list_ptr(cred, 0) and fido_cred_x5c_list_len(cred, 0) is equivalent to fido_cred_x5c_ptr(cred) and fido_cred_x5c_len(cred) respectively. If idx exceeds the return value of fido_cred_x5c_list_count(), fido_cred_x5c_list_ptr() returns NULL and fido_cred_x5c_list_len() returns 0.

The authenticator data, x509 certificate, and signature parts of a credential are typically passed to a FIDO2 server for verification.

The fido_cred_entattest() function returns true if an enterprise attestation was returned for cred.

The fido_cred_type() function returns the COSE algorithm of cred.

The fido_cred_flags() function returns the authenticator data flags of cred.

The fido_cred_sigcount() function returns the authenticator data signature counter of cred.

RETURN VALUES
The authenticator data returned by fido_cred_authdata_ptr() is a CBOR-encoded byte string, as obtained from the authenticator. To obtain the decoded byte string, use fido_cred_authdata_raw_ptr().

If not NULL, pointers returned by fido_cred_fmt(), fido_cred_authdata_ptr(), fido_cred_clientdata_hash_ptr(), fido_cred_id_ptr(), fido_cred_aaguid_ptr(), fido_cred_largeblob_key_ptr(), fido_cred_pubkey_ptr(), fido_cred_sig_ptr(), and fido_cred_x5c_ptr() are guaranteed to exist until any API function that takes cred without the const qualifier is invoked.

SEE ALSO
fido_cred_exclude(3), fido_cred_set_authdata(3), fido_cred_set_pin_minlen(3), fido_cred_set_prot(3), fido_cred_verify(3), fido_credman_metadata_new(3), fido_credman_rk(3), fido_dev_largeblob_get(3), fido_dev_make_cred(3)