---
name: "fido_assert_allow_cred"
section: "3"
platform: "linux"
package: "libfido2"
version: "1.17.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/fido_assert_allow_cred"
---

# fido\_assert\_allow\_cred(3)

manage allow lists in a FIDO2 assertion

## NAME

**fido\_assert\_allow\_cred**, **fido\_assert\_empty\_allow\_list** – manage allow lists in a FIDO2 assertion

## SYNOPSIS

**#include \<fido.h\>**

*int*\

**fido\_assert\_allow\_cred**(*fido\_assert\_t \*assert*, *const unsigned char \*ptr*, *size\_t len*);

*int*\

**fido\_assert\_empty\_allow\_list**(*fido\_assert\_t \*assert*);

## DESCRIPTION

The **fido\_assert\_allow\_cred**() function adds *ptr* to the list of credentials allowed in *assert*, 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\_assert\_allow\_cred**() fails, the existing list of allowed credentials is preserved.

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

The **fido\_assert\_empty\_allow\_list**() function empties the list of credentials allowed in *assert*.

## RETURN VALUES

The error codes returned by **fido\_assert\_allow\_cred**() and **fido\_assert\_empty\_allow\_list**() are defined in ⟨fido/err.h⟩. On success, FIDO\_OK is returned.

## SEE ALSO

[fido\_assert\_new(3)](/fido_assert_new/3.md), [fido\_assert\_set\_authdata(3)](/fido_assert_set_authdata/3.md), [fido\_dev\_get\_assert(3)](/fido_dev_get_assert/3.md)