.\" $OpenBSD: SMIME_read_ASN1.3,v 1.2 2021/12/14 15:22:49 schwarze Exp $
.\" full merge up to:
.\" OpenSSL SMIME_read_PKCS7.pod 83cf7abf May 29 13:07:08 2018 +0100
.\" OpenSSL SMIME_read_CMS.pod b97fdb57 Nov 11 09:33:09 2016 +0100
.\"
.\" This file was written by Dr. Stephen Henson <steve@openssl.org>.
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.Dd $Mdocdate: December 14 2021 $
.Dt SMIME_READ_ASN1 3
.Os
.Sh NAME
.Nm SMIME_read_ASN1
.Nd generic S/MIME message parser
.Sh SYNOPSIS
.In openssl/asn1.h
.Ft ASN1_VALUE *
.Fo SMIME_read_ASN1
.Fa "BIO *in_bio"
.Fa "BIO **out_bio"
.Fa "const ASN1_ITEM *it"
.Fc
.Sh DESCRIPTION
.Fn SMIME_read_ASN1
reads a message in S/MIME format from
.Fa in_bio .
.Pp
If the message uses cleartext signing, the content is saved in a memory
.Vt BIO
which is written to
.Pf * Fa out_bio .
Otherwise,
.Pf * Fa out_bio
is set to
.Dv NULL .
.Pp
To support future functionality, if
.Fa out_bio
is not
.Dv NULL ,
.Pf * Fa out_bio
should be initialized to
.Dv NULL
before calling
.Fn SMIME_read_ASN1 .
.Sh RETURN VALUES
.Fn SMIME_read_ASN1
returns a newly allocated object of type
.Fa it
or
.Dv NULL
if an error occurred.
The error can be obtained from
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.Xr ASN1_item_d2i_bio 3 ,
.Xr BIO_f_base64 3 ,
.Xr BIO_new 3 ,
.Xr SMIME_read_CMS 3 ,
.Xr SMIME_read_PKCS7 3 ,
.Xr SMIME_text 3
.Sh HISTORY
.Fn SMIME_read_ASN1
first appeared in OpenSSL 0.9.8h and has been available since
.Ox 4.5 .
.Sh BUGS
The MIME parser used by
.Fn SMIME_read_ASN1
is somewhat primitive.
While it will handle most S/MIME messages, more complex compound
formats may not work.
.Pp
The parser assumes that the
structure is always base64 encoded, and it will not handle the case
where it is in binary format or uses quoted printable format.
.Pp
The use of a memory
to hold the signed content limits the size of the message which can
be processed due to memory restraints: a streaming single pass
option should be available.