252 lines
7.3 KiB
Groff
252 lines
7.3 KiB
Groff
.\" $OpenBSD: PKCS7_sign.3,v 1.13 2020/06/10 11:43:08 schwarze Exp $
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.\" full merge up to: OpenSSL df75c2bf Dec 9 01:02:36 2018 +0100
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.\"
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.\" This file was written by Dr. Stephen Henson <steve@openssl.org>.
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.\" Copyright (c) 2002, 2003, 2006-2009, 2015 The OpenSSL Project.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\"
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\"
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in
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.\" the documentation and/or other materials provided with the
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.\" distribution.
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.\"
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.\" 3. All advertising materials mentioning features or use of this
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.\" software must display the following acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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.\"
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.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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.\" endorse or promote products derived from this software without
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.\" prior written permission. For written permission, please contact
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.\" openssl-core@openssl.org.
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.\"
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.\" 5. Products derived from this software may not be called "OpenSSL"
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.\" nor may "OpenSSL" appear in their names without prior written
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.\" permission of the OpenSSL Project.
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.\"
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.\" 6. Redistributions of any form whatsoever must retain the following
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.\" acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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.\" OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd $Mdocdate: June 10 2020 $
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.Dt PKCS7_SIGN 3
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.Os
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.Sh NAME
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.Nm PKCS7_sign
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.Nd create a PKCS#7 signedData structure
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.Sh SYNOPSIS
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.In openssl/pkcs7.h
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.Ft PKCS7 *
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.Fo PKCS7_sign
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.Fa "X509 *signcert"
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.Fa "EVP_PKEY *pkey"
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.Fa "STACK_OF(X509) *certs"
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.Fa "BIO *data"
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.Fa "int flags"
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.Fc
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.Sh DESCRIPTION
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.Fn PKCS7_sign
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creates and returns a PKCS#7 signedData structure.
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.Fa signcert
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is the certificate to sign with,
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.Fa pkey
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is the corresponding private key.
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.Fa certs
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is an optional additional set of certificates to include in the PKCS#7
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structure (for example any intermediate CAs in the chain).
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.Pp
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The data to be signed is read from
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.Vt BIO
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.Fa data .
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.Pp
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.Fa flags
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is an optional set of flags.
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.Pp
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Any of the following flags (OR'ed together) can be passed in the
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.Fa flags
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parameter.
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.Pp
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Many S/MIME clients expect the signed content to include valid MIME
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headers.
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If the
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.Dv PKCS7_TEXT
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flag is set, MIME headers for type
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.Sy text/plain
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are prepended to the data.
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.Pp
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If
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.Dv PKCS7_NOCERTS
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is set, the signer's certificate will not be included in the PKCS7
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structure, though the signer's certificate must still be supplied in the
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.Fa signcert
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parameter.
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This can reduce the size of the signature if the signer's certificate can
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be obtained by other means: for example a previously signed message.
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.Pp
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The data being signed is included in the
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.Vt PKCS7
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structure, unless
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.Dv PKCS7_DETACHED
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is set, in which case it is omitted.
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This is used for PKCS7 detached signatures which are used in S/MIME
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plaintext signed messages for example.
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.Pp
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Normally the supplied content is translated into MIME canonical format
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(as required by the S/MIME specifications).
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If
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.Dv PKCS7_BINARY
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is set, no translation occurs.
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This option should be used if the supplied data is in binary format;
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otherwise, the translation will corrupt it.
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.Pp
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The signedData structure includes several PKCS#7 authenticatedAttributes
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including the signing time, the PKCS#7 content type and the supported
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list of ciphers in an SMIMECapabilities attribute.
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If
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.Dv PKCS7_NOATTR
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is set, then no authenticatedAttributes will be used.
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If
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.Dv PKCS7_NOSMIMECAP
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is set, then just the SMIMECapabilities are omitted.
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.Pp
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If present, the SMIMECapabilities attribute indicates support for the
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following algorithms: triple DES, 128-bit RC2, 64-bit RC2, DES
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and 40-bit RC2.
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If any of these algorithms is disabled then it will not be included.
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.Pp
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If the flags
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.Dv PKCS7_STREAM
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is set, then the returned
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.Vt PKCS7
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structure is just initialized ready to perform the signing operation.
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The signing is however
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.Sy not
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performed and the data to be signed is not read from the
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.Fa data
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parameter.
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Signing is deferred until after the data has been written.
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In this way data can be signed in a single pass.
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.Pp
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If the
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.Dv PKCS7_PARTIAL
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flag is set, a partial
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.Vt PKCS7
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structure is output to which additional signers and capabilities can be
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added before finalization.
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.Pp
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If the flag
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.Dv PKCS7_STREAM
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is set, the returned
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.Vt PKCS7
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structure is
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.Sy not
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complete and outputting its contents via a function that does not
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properly finalize the
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.Vt PKCS7
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structure will give unpredictable results.
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.Pp
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Several functions including
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.Xr PKCS7_final 3 ,
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.Xr SMIME_write_PKCS7 3 ,
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.Xr PEM_write_bio_PKCS7_stream 3 ,
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and
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.Xr i2d_PKCS7_bio_stream 3
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finalize the structure.
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Alternatively finalization can be performed by obtaining the streaming
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ASN.1
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.Vt BIO
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directly using
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.Fn BIO_new_PKCS7 .
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.Pp
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If a signer is specified, it will use the default digest for the
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signing algorithm.
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This is
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.Sy SHA1
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for both RSA and DSA keys.
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.Pp
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In OpenSSL 1.0.0, the
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.Fa certs ,
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.Fa signcert ,
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and
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.Fa pkey
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parameters can all be
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.Dv NULL
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if the
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.Dv PKCS7_PARTIAL
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flag is set.
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One or more signers can be added using the function
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.Xr PKCS7_sign_add_signer 3
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and attributes can be added using the functions described in
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.Xr PKCS7_add_attribute 3 .
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.Xr PKCS7_final 3
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must also be called to finalize the structure if streaming is not
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enabled.
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Alternative signing digests can also be specified using this method.
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.Pp
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In OpenSSL 1.0.0, if
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.Fa signcert
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and
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.Fa pkey
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are
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.Dv NULL ,
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then a certificate-only PKCS#7 structure is output.
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.Pp
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In versions of OpenSSL before 1.0.0 the
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.Fa signcert
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and
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.Fa pkey
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parameters must
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.Sy NOT
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be
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.Dv NULL .
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.Sh RETURN VALUES
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.Fn PKCS7_sign
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returns either a valid
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.Vt PKCS7
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structure or
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.Dv NULL
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if an error occurred.
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The error can be obtained from
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.Xr ERR_get_error 3 .
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.Sh SEE ALSO
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.Xr PKCS7_add_attribute 3 ,
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.Xr PKCS7_encrypt 3 ,
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.Xr PKCS7_final 3 ,
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.Xr PKCS7_get_signer_info 3 ,
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.Xr PKCS7_new 3 ,
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.Xr PKCS7_sign_add_signer 3 ,
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.Xr PKCS7_verify 3
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.Sh HISTORY
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.Fn PKCS7_sign
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first appeared in OpenSSL 0.9.5 and have been available since
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.Ox 2.7 .
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.Pp
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The
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.Dv PKCS7_PARTIAL
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and
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.Dv PKCS7_STREAM
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flags were added in OpenSSL 1.0.0.
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.Sh BUGS
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Some advanced attributes such as counter signatures are not supported.
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