1.\" $OpenBSD: SMIME_read_PKCS7.3,v 1.8 2021/12/14 14:30:50 schwarze Exp $ 2.\" full merge up to: OpenSSL 83cf7abf May 29 13:07:08 2018 +0100 3.\" 4.\" This file was written by Dr. Stephen Henson <steve@openssl.org>. 5.\" Copyright (c) 2002, 2006 The OpenSSL Project. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in 16.\" the documentation and/or other materials provided with the 17.\" distribution. 18.\" 19.\" 3. All advertising materials mentioning features or use of this 20.\" software must display the following acknowledgment: 21.\" "This product includes software developed by the OpenSSL Project 22.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 23.\" 24.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 25.\" endorse or promote products derived from this software without 26.\" prior written permission. For written permission, please contact 27.\" openssl-core@openssl.org. 28.\" 29.\" 5. Products derived from this software may not be called "OpenSSL" 30.\" nor may "OpenSSL" appear in their names without prior written 31.\" permission of the OpenSSL Project. 32.\" 33.\" 6. Redistributions of any form whatsoever must retain the following 34.\" acknowledgment: 35.\" "This product includes software developed by the OpenSSL Project 36.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 37.\" 38.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 39.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 40.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 41.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 42.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 43.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 44.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 45.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 46.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 47.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 48.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 49.\" OF THE POSSIBILITY OF SUCH DAMAGE. 50.\" 51.Dd $Mdocdate: December 14 2021 $ 52.Dt SMIME_READ_PKCS7 3 53.Os 54.Sh NAME 55.Nm SMIME_read_PKCS7 56.Nd extract a PKCS#7 object from an S/MIME message 57.Sh SYNOPSIS 58.In openssl/pkcs7.h 59.Ft PKCS7 * 60.Fo SMIME_read_PKCS7 61.Fa "BIO *in" 62.Fa "BIO **bcont" 63.Fc 64.Sh DESCRIPTION 65.Fn SMIME_read_PKCS7 66parses a message in S/MIME format. 67.Pp 68.Fa in 69is a 70.Vt BIO 71to read the message from. 72.Pp 73If cleartext signing is used, then the content is saved in a memory 74.Vt BIO 75which is written to 76.Pf * Fa bcont , 77otherwise 78.Pf * Fa bcont 79is set to 80.Dv NULL . 81.Pp 82The parsed PKCS#7 structure is returned, or 83.Dv NULL 84if an error occurred. 85.Pp 86If 87.Pf * Fa bcont 88is not 89.Dv NULL , 90then the message is clear text signed. 91.Pf * Fa bcont 92can then be passed to 93.Xr PKCS7_verify 3 94with the 95.Dv PKCS7_DETACHED 96flag set. 97.Pp 98Otherwise the type of the returned structure can be determined using the 99.Fn PKCS7_type_is_* 100macros defined in 101.In openssl/pkcs7.h . 102.Pp 103To support future functionality, if 104.Fa bcont 105is not 106.Dv NULL , 107.Pf * Fa bcont 108should be initialized to 109.Dv NULL . 110For example: 111.Bd -literal -offset indent 112BIO *cont = NULL; 113PKCS7 *p7; 114 115p7 = SMIME_read_PKCS7(in, &cont); 116.Ed 117.Sh RETURN VALUES 118.Fn SMIME_read_PKCS7 119returns a valid 120.Vt PKCS7 121structure or 122.Dv NULL 123if an error occurred. 124The error can be obtained from 125.Xr ERR_get_error 3 . 126.Sh SEE ALSO 127.Xr PKCS7_new 3 , 128.Xr SMIME_read_ASN1 3 , 129.Xr SMIME_write_PKCS7 3 130.Sh HISTORY 131.Fn SMIME_read_PKCS7 132first appeared in OpenSSL 0.9.5 and has been available since 133.Ox 2.7 . 134.Sh BUGS 135The MIME parser used by 136.Fn SMIME_read_PKCS7 137is somewhat primitive. 138While it will handle most S/MIME messages, more complex compound 139formats may not work. 140.Pp 141The parser assumes that the 142.Vt PKCS7 143structure is always base64 encoded, and it will not handle the case 144where it is in binary format or uses quoted printable format. 145.Pp 146The use of a memory 147.Vt BIO 148to hold the signed content limits the size of the message which can 149be processed due to memory restraints: a streaming single pass 150option should be available. 151