ASN1_item_sign.3

.\" $OpenBSD: ASN1_item_sign.3,v 1.2 2021/12/18 17:47:44 schwarze Exp $
.\"
.\" Copyright (c) 2021 Ingo Schwarze <schwarze@openbsd.org>
.\"
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.Dd $Mdocdate: December 18 2021 $
.Dt ASN1_ITEM_SIGN 3
.Os
.Sh NAME
.Nm ASN1_item_sign ,
.Nm ASN1_item_sign_ctx
.Nd DER-encode and sign an ASN.1 value
.Sh SYNOPSIS
.In openssl/x509.h
.Ft int
.Fo ASN1_item_sign
.Fa "const ASN1_ITEM *it"
.Fa "X509_ALGOR *algor1"
.Fa "X509_ALGOR *algor2"
.Fa "ASN1_BIT_STRING *sig_out"
.Fa "void *val_in"
.Fa "EVP_PKEY *pkey"
.Fa "const EVP_MD *type"
.Fc
.Ft int
.Fo ASN1_item_sign_ctx
.Fa "const ASN1_ITEM *it"
.Fa "X509_ALGOR *algor1"
.Fa "X509_ALGOR *algor2"
.Fa "ASN1_BIT_STRING *sig_out"
.Fa "void *val_in"
.Fa "EVP_MD_CTX *ctx"
.Fc
.Sh DESCRIPTION
.Fn ASN1_item_sign
assumes that
.Fa val_in
is an
.Vt ASN1_VALUE
of the type specified by
.Fa it ,
encodes it into DER format by calling
.Xr ASN1_item_i2d 3 ,
and signs the resulting byte array in a way similar to
.Xr EVP_DigestSign 3 ,
using a signing context created with
.Xr EVP_DigestSignInit 3
for the given digest
.Fa type
and private key
.Fa pkey .
The created signature is placed into the
.Fa sig_out
object provided by the caller,
freeing and replacing any data already contained in that object.
.Pp
.Fn ASN1_item_sign_ctx
is similar except that the provided
.Ft ctx
is used rather than creating a new one.
No matter whether
.Fn ASN1_item_sign_ctx
succeeds or fails,
.Xr EVP_MD_CTX_cleanup 3
is called on
.Fa ctx
before returning.
.Pp
For both functions, unless
.Fa algor1
is
.Dv NULL ,
its algorithm OID and parameter type are set according to the digest
.Fa type
used, and its parameter value is cleared.
In RSA-PSS mode, the parameter value is also copied into
.Fa algor1 .
Unless
.Fa algor2
is
.Dv NULL ,
the same data is copied into it.
.\" The following is not yet supported by LibreSSL
.\" because we do not provide EVP_PKEY_asn1_set_item(3).
.\" except that user-defined key types set up with
.\" .Xr EVP_PKEY_asn1_new 3
.\" may optionally provide information about a second algorithm in
.\" .Fa algor2 .
.Sh RETURN VALUES
These functions return the length of the signature in bytes
or 0 if memory allocation, encoding, or signing fails.
.Pp
.Fn ASN1_item_sign_ctx
also fails and returns 0 if
.Fa ctx
is not fully initialized.
.Sh SEE ALSO
.Xr ASN1_BIT_STRING_new 3 ,
.Xr ASN1_item_digest 3 ,
.Xr ASN1_item_i2d 3 ,
.Xr ASN1_item_verify 3 ,
.Xr EVP_Digest 3 ,
.Xr EVP_DigestSign 3 ,
.Xr EVP_MD_CTX_new 3 ,
.\" We do not provide EVP_PKEY_asn1_set_item(3).
.\" .Xr EVP_PKEY_asn1_new 3 ,
.Xr EVP_PKEY_new 3 ,
.Xr OBJ_find_sigid_by_algs 3 ,
.Xr X509_ALGOR_new 3
.Sh HISTORY
.Fn ASN1_item_sign
first appeared in OpenSSL 0.9.7 and has been available since
.Ox 3.1 .
.Pp
.Fn ASN1_item_sign_ctx
first appeared in OpenSSL 1.0.1 and has been available since
.Ox 5.3 .