--- /dev/null
+.\" $OpenBSD: EVP_PKEY_add1_attr.3,v 1.1 2021/10/22 15:50:19 schwarze Exp $
+.\"
+.\" Copyright (c) 2021 Ingo Schwarze <schwarze@openbsd.org>
+.\"
+.\" Permission to use, copy, modify, and distribute this software for any
+.\" purpose with or without fee is hereby granted, provided that the above
+.\" copyright notice and this permission notice appear in all copies.
+.\"
+.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+.\"
+.Dd $Mdocdate: October 22 2021 $
+.Dt EVP_PKEY_ADD1_ATTR 3
+.Os
+.Sh NAME
+.Nm EVP_PKEY_add1_attr ,
+.Nm EVP_PKEY_add1_attr_by_OBJ ,
+.Nm EVP_PKEY_add1_attr_by_NID ,
+.Nm EVP_PKEY_add1_attr_by_txt ,
+.Nm EVP_PKEY_delete_attr ,
+.Nm EVP_PKEY_get_attr ,
+.Nm EVP_PKEY_get_attr_count ,
+.Nm EVP_PKEY_get_attr_by_OBJ ,
+.Nm EVP_PKEY_get_attr_by_NID
+.Nd X.501 Attributes of private keys
+.Sh SYNOPSIS
+.In openssl/x509.h
+.Ft int
+.Fo EVP_PKEY_add1_attr
+.Fa "EVP_PKEY *key"
+.Fa "X509_ATTRIBUTE *attr"
+.Fc
+.Ft int
+.Fo EVP_PKEY_add1_attr_by_OBJ
+.Fa "EVP_PKEY *key"
+.Fa "const ASN1_OBJECT *obj"
+.Fa "int type"
+.Fa "const unsigned char *data"
+.Fa "int len"
+.Fc
+.Ft int
+.Fo EVP_PKEY_add1_attr_by_NID
+.Fa "EVP_PKEY *key"
+.Fa "int nid"
+.Fa "int type"
+.Fa "const unsigned char *data"
+.Fa "int len"
+.Fc
+.Ft int
+.Fo EVP_PKEY_add1_attr_by_txt
+.Fa "EVP_PKEY *key"
+.Fa "const char *name"
+.Fa "int type"
+.Fa "const unsigned char *data"
+.Fa "int len"
+.Fc
+.Ft X509_ATTRIBUTE *
+.Fo EVP_PKEY_delete_attr
+.Fa "EVP_PKEY *key"
+.Fa "int index"
+.Fc
+.Ft X509_ATTRIBUTE *
+.Fo EVP_PKEY_get_attr
+.Fa "const EVP_PKEY *key"
+.Fa "int index"
+.Fc
+.Ft int
+.Fo EVP_PKEY_get_attr_count
+.Fa "const EVP_PKEY *key"
+.Fc
+.Ft int
+.Fo EVP_PKEY_get_attr_by_OBJ
+.Fa "const EVP_PKEY *key"
+.Fa "const ASN1_OBJECT *obj"
+.Fa "int start_after"
+.Fc
+.Ft int
+.Fo EVP_PKEY_get_attr_by_NID
+.Fa "const EVP_PKEY *key"
+.Fa "int nid"
+.Fa "int start_after"
+.Fc
+.Sh DESCRIPTION
+These functions support associating an array of X.501 Attributes
+with a private key.
+Such attributes can for example be included in PKCS#12 structures.
+.Pp
+.Fn EVP_PKEY_add1_attr
+appends a deep copy of the
+.Fa attr
+using
+.Xr X509at_add1_attr 3 .
+.Pp
+.Fn EVP_PKEY_add1_attr_by_OBJ ,
+.Fn EVP_PKEY_add1_attr_by_NID ,
+and
+.Fn EVP_PKEY_add1_attr_by_txt
+create a new X.501 Attribute object using
+.Xr X509_ATTRIBUTE_create_by_OBJ 3 ,
+.Xr X509_ATTRIBUTE_create_by_NID 3 ,
+or
+.Xr X509_ATTRIBUTE_create_by_txt 3 ,
+respectively, and append it using
+.Xr X509at_add1_attr 3 .
+.Pp
+.Fn EVP_PKEY_delete_attr
+deletes the attribute with the zero-based
+.Fa index
+using
+.Xr X509at_delete_attr 3 .
+.Pp
+.Fn EVP_PKEY_get_attr
+returns the attribute with the zero-based
+.Fa index
+using
+.Xr X509at_get_attr 3 .
+.Pp
+.Fn EVP_PKEY_get_attr_count
+returns the number of attributes currently associated with the
+.Fa key
+using
+.Xr X509at_get_attr_count 3 .
+.Pp
+.Fn EVP_PKEY_get_attr_by_OBJ
+and
+.Fn EVP_PKEY_get_attr_by_NID
+search for an attribute of the type
+.Fa obj
+or
+.Fa nid
+using
+.Xr X509at_get_attr_by_OBJ 3
+or
+.Xr X509at_get_attr_by_NID 3 ,
+respectively.
+.Sh RETURN VALUES
+.Fn EVP_PKEY_add1_attr ,
+.Fn EVP_PKEY_add1_attr_by_OBJ ,
+.Fn EVP_PKEY_add1_attr_by_NID ,
+and
+.Fn EVP_PKEY_add1_attr_by_txt
+return 1 for success or 0 for failure.
+.Pp
+.Fn EVP_PKEY_delete_attr
+and
+.Fn X509at_get_attr
+return the deleted or requested attribute or
+.Dv NULL
+if the requested index is negative or greater than or equal to
+the current number of attributes associated with the
+.Fa key .
+.Pp
+.Fn EVP_PKEY_get_attr_count
+returns the current number of attributes.
+.Pp
+.Fn EVP_PKEY_get_attr_by_OBJ
+and
+.Fn EVP_PKEY_get_attr_by_NID
+return the index of the first attribute that has an index greater than
+.Fa start_after
+and a type matching
+.Fa obj
+or
+.Fa nid ,
+respectively, or \-1 on failure.
+In addition,
+.Fn EVP_PKEY_get_attr_by_NID
+returns \-2 if
+.Xr OBJ_nid2obj 3
+fails on the requested
+.Fa nid .
+.Sh SEE ALSO
+.Xr EVP_PKEY_new 3 ,
+.Xr OBJ_nid2obj 3 ,
+.Xr PKCS12_create 3 ,
+.Xr X509_ATTRIBUTE_create_by_OBJ 3 ,
+.Xr X509_ATTRIBUTE_new 3 ,
+.Xr X509at_add1_attr 3 ,
+.Xr X509at_get_attr 3
+.Sh HISTORY
+These funtions first appeared in OpenSSL 0.9.8
+and have been available since
+.Ox 4.5 .