.\" $OpenBSD: EXTENDED_KEY_USAGE_new.3,v 1.6 2021/10/27 11:24:47 schwarze Exp $
.\"
.\" Copyright (c) 2016 Ingo Schwarze <schwarze@openbsd.org>
.\"
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.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
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.Dd $Mdocdate: October 27 2021 $
.Dt EXTENDED_KEY_USAGE_NEW 3
.Os
.Sh NAME
.Nm EXTENDED_KEY_USAGE_new ,
.Nm EXTENDED_KEY_USAGE_free
.Nd X.509 key usage restrictions
.Sh SYNOPSIS
.In openssl/x509v3.h
.Ft EXTENDED_KEY_USAGE
.Fn EXTENDED_KEY_USAGE_new void
.Ft void
.Fn EXTENDED_KEY_USAGE_free "EXTENDED_KEY_USAGE *eku"
.Sh DESCRIPTION
By using the key usage extension, the extended key usage extension,
or both of them,
.Vt X509
end entity certificates may indicate that the key contained in them
is only intended to be used for the specified purposes.
If both extensions are present, only uses compatible with both
extensions are intended.
.Pp
.Fn EXTENDED_KEY_USAGE_new
allocates and initializes an empty
.Vt EXTENDED_KEY_USAGE
object, which is a
.Vt STACK_OF(ASN1_OBJECT)
and represents an ASN.1
.Vt ExtKeyUsageSyntax
structure defined in RFC 5280 section 4.2.1.12.
It can hold key purpose identifiers.
.Pp
.Fn EXTENDED_KEY_USAGE_free
frees
.Fa eku .
.Pp
The key usage extension uses the ASN.1 BIT STRING data type
and doesn't require any dedicated object.
.Sh RETURN VALUES
.Fn EXTENDED_KEY_USAGE_new
returns the new
.Vt EXTENDED_KEY_USAGE
object or
.Dv NULL
if an error occurs.
.Sh SEE ALSO
.Xr BASIC_CONSTRAINTS_new 3 ,
.Xr d2i_EXTENDED_KEY_USAGE 3 ,
.Xr POLICYINFO_new 3 ,
.Xr X509_check_purpose 3 ,
.Xr X509_EXTENSION_new 3 ,
.Xr X509_get_extension_flags 3 ,
.Xr X509_new 3
.Sh STANDARDS
RFC 5280: Internet X.509 Public Key Infrastructure Certificate and
Certificate Revocation List (CRL) Profile:
.Bl -dash -compact
.It
section 4.2.1.3: Key Usage
.It
section 4.2.1.12: Extended Key Usage
.El
.Sh HISTORY
.Fn EXTENDED_KEY_USAGE_new
and
.Fn EXTENDED_KEY_USAGE_free
first appeared in OpenSSL 0.9.7 and have been available since
.Ox 3.2 .