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<ul>
<li><a href="#name">NAME</a></li>
<li><a href="#synopsis">SYNOPSIS</a></li>
<li><a href="#description">DESCRIPTION</a></li>
<li><a href="#notes">NOTES</a></li>
<li><a href="#bugs">BUGS</a></li>
<li><a href="#return_values">RETURN VALUES</a></li>
<li><a href="#see_also">SEE ALSO</a></li>
<li><a href="#history">HISTORY</a></li>
<li><a href="#copyright">COPYRIGHT</a></li>
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<h1><a name="name">NAME</a></h1>
<p>PKCS7_sign - create a PKCS#7 signedData structure</p>
<p>
</p>
<hr />
<h1><a name="synopsis">SYNOPSIS</a></h1>
<pre>
#include <openssl/pkcs7.h></pre>
<pre>
PKCS7 *PKCS7_sign(X509 *signcert, EVP_PKEY *pkey, STACK_OF(X509) *certs,
BIO *data, int flags);</pre>
<p>
</p>
<hr />
<h1><a name="description">DESCRIPTION</a></h1>
<p>PKCS7_sign() creates and returns a PKCS#7 signedData structure.
<em>signcert</em> is the certificate to sign with, <em>pkey</em> is the corresponding
private key. <em>certs</em> is an optional set of extra certificates to include
in the PKCS#7 structure (for example any intermediate CAs in the chain).</p>
<p>The data to be signed is read from BIO <em>data</em>.</p>
<p><em>flags</em> is an optional set of flags.</p>
<p>Any of the following flags (ored together) can be passed in the <em>flags</em></p>
<p>Many S/MIME clients expect the signed content to include valid MIME headers. If
the <strong>PKCS7_TEXT</strong> flag is set MIME headers for type <code>text/plain</code> are prepended
to the data.</p>
<p>If <strong>PKCS7_NOCERTS</strong> is set the signer's certificate and the extra <em>certs</em>
will not be included in the PKCS7 structure.
The signer's certificate must still be supplied in the <em>signcert</em> parameter
though. This can reduce the size of the signatures if the signer's certificates
can be obtained by other means: for example a previously signed message.</p>
<p>The data being signed is included in the PKCS7 structure, unless
<strong>PKCS7_DETACHED</strong> is set in which case it is omitted. This is used for PKCS7
detached signatures which are used in S/MIME plaintext signed messages for
example.</p>
<p>Normally the supplied content is translated into MIME canonical format (as
required by the S/MIME specifications) if <strong>PKCS7_BINARY</strong> is set no translation
occurs. This option should be used if the supplied data is in binary format
otherwise the translation will corrupt it.</p>
<p>The signedData structure includes several PKCS#7 authenticatedAttributes
including the signing time, the PKCS#7 content type and the supported list of
ciphers in an SMIMECapabilities attribute. If <strong>PKCS7_NOATTR</strong> is set then no
authenticatedAttributes will be used. If <strong>PKCS7_NOSMIMECAP</strong> is set then just
the SMIMECapabilities are omitted.</p>
<p>If present the SMIMECapabilities attribute indicates support for the following
algorithms: triple DES, 128 bit RC2, 64 bit RC2, DES and 40 bit RC2. If any of
these algorithms is disabled then it will not be included.</p>
<p>If the flags <strong>PKCS7_STREAM</strong> is set then the returned <strong>PKCS7</strong> structure is
just initialized ready to perform the signing operation. The signing is however
<strong>not</strong> performed and the data to be signed is not read from the <em>data</em>
parameter. Signing is deferred until after the data has been written. In this
way data can be signed in a single pass.</p>
<p>If the <strong>PKCS7_PARTIAL</strong> flag is set a partial <strong>PKCS7</strong> structure is output to
which additional signers and capabilities can be added before finalization.</p>
<p>
</p>
<hr />
<h1><a name="notes">NOTES</a></h1>
<p>If the flag <strong>PKCS7_STREAM</strong> is set the returned <strong>PKCS7</strong> structure is <strong>not</strong>
complete and outputting its contents via a function that does not properly
finalize the <strong>PKCS7</strong> structure will give unpredictable results.</p>
<p>Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(),
PEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization
can be performed by obtaining the streaming ASN1 <strong>BIO</strong> directly using
BIO_new_PKCS7().</p>
<p>If a signer is specified it will use the default digest for the signing
algorithm. This is <strong>SHA1</strong> for both RSA and DSA keys.</p>
<p>The <em>certs</em>, <em>signcert</em> and <em>pkey</em> parameters can all be
NULL if the <strong>PKCS7_PARTIAL</strong> flag is set. One or more signers can be added
using the function PKCS7_sign_add_signer(). PKCS7_final() must also be
called to finalize the structure if streaming is not enabled. Alternative
signing digests can also be specified using this method.</p>
<p>If <em>signcert</em> and <em>pkey</em> are NULL then a certificates only
PKCS#7 structure is output.</p>
<p>In versions of OpenSSL before 1.0.0 the <em>signcert</em> and <em>pkey</em> parameters must
not be NULL.</p>
<p>
</p>
<hr />
<h1><a name="bugs">BUGS</a></h1>
<p>Some advanced attributes such as counter signatures are not supported.</p>
<p>
</p>
<hr />
<h1><a name="return_values">RETURN VALUES</a></h1>
<p>PKCS7_sign() returns either a valid PKCS7 structure or NULL if an error
occurred. The error can be obtained from <code>ERR_get_error(3)</code>.</p>
<p>
</p>
<hr />
<h1><a name="see_also">SEE ALSO</a></h1>
<p><em>ERR_get_error(3)</em>, <em>PKCS7_verify(3)</em></p>
<p>
</p>
<hr />
<h1><a name="history">HISTORY</a></h1>
<p>The <strong>PKCS7_PARTIAL</strong> flag, and the ability for <em>certs</em>, <em>signcert</em>,
and <em>pkey</em> parameters to be NULL were added in OpenSSL 1.0.0.</p>
<p>The <strong>PKCS7_STREAM</strong> flag was added in OpenSSL 1.0.0.</p>
<p>
</p>
<hr />
<h1><a name="copyright">COPYRIGHT</a></h1>
<p>Copyright 2002-2022 The OpenSSL Project Authors. All Rights Reserved.</p>
<p>Licensed under the OpenSSL license (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p>
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