.\" Copyright (c) 2018 Yubico AB. All rights reserved.
.\" Use of this source code is governed by a BSD-style
.\" license that can be found in the LICENSE file.
.\"
.Dd $Mdocdate: August 29 2022 $
.Dt FIDO_ASSERT_VERIFY 3
.Os
.Sh NAME
.Nm fido_assert_verify
.Nd verifies the signature of a FIDO2 assertion statement
.Sh SYNOPSIS
.In fido.h
.Ft int
.Fn fido_assert_verify "const fido_assert_t *assert" "size_t idx" "int cose_alg" "const void *pk"
.Sh DESCRIPTION
The
.Fn fido_assert_verify
function verifies whether the signature contained in statement index
.Fa idx
of
.Fa assert
matches the parameters of the assertion.
Before using
.Fn fido_assert_verify
in a sensitive context, the reader is strongly encouraged to make
herself familiar with the FIDO2 assertion statement process
as defined in the Web Authentication (webauthn) standard.
.Pp
A brief description follows:
.Pp
The
.Fn fido_assert_verify
function verifies whether the client data hash, relying party ID,
user presence and user verification attributes of
.Fa assert
have been attested by the holder of the private counterpart of
the public key
.Fa pk
of COSE type
.Fa cose_alg ,
where
.Fa cose_alg
is
.Dv COSE_ES256 ,
.Dv COSE_RS256 ,
or
.Dv COSE_EDDSA ,
and
.Fa pk
points to a
.Vt es256_pk_t ,
.Vt rs256_pk_t ,
or
.Vt eddsa_pk_t
type accordingly.
.Pp
Please note that the first statement in
.Fa assert
has an
.Fa idx
of 0.
.Sh RETURN VALUES
The error codes returned by
.Fn fido_assert_verify
are defined in
.In fido/err.h .
If
statement
.Fa idx
of
.Fa assert
passes verification with
.Fa pk ,
then
.Dv FIDO_OK
is returned.
.Sh SEE ALSO
.Xr fido_assert_new 3 ,
.Xr fido_assert_set_authdata 3