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CMS_ADD1_SIGNER(3)		    OpenSSL		    CMS_ADD1_SIGNER(3)

NAME
       CMS_add1_signer,	CMS_SignerInfo_sign - add a signer to a
       CMS_ContentInfo signed data structure

SYNOPSIS
	#include <openssl/cms.h>

	CMS_SignerInfo *CMS_add1_signer(CMS_ContentInfo	*cms, X509 *signcert,
					EVP_PKEY *pkey,	const EVP_MD *md,
					unsigned int flags);

	int CMS_SignerInfo_sign(CMS_SignerInfo *si);

DESCRIPTION
       CMS_add1_signer() adds a	signer with certificate	signcert and private
       key pkey	using message digest md	to CMS_ContentInfo SignedData
       structure cms.

       The CMS_ContentInfo structure should be obtained	from an	initial	call
       to CMS_sign() with the flag CMS_PARTIAL set or in the case or re-
       signing a valid CMS_ContentInfo SignedData structure.

       If the md parameter is NULL then	the default digest for the public key
       algorithm will be used.

       Unless the CMS_REUSE_DIGEST flag	is set the returned CMS_ContentInfo
       structure is not	complete and must be finalized either by streaming (if
       applicable) or a	call to	CMS_final().

       The CMS_SignerInfo_sign() function will explicitly sign a
       CMS_SignerInfo structure, its main use is when CMS_REUSE_DIGEST and
       CMS_PARTIAL flags are both set.

NOTES
       The main	purpose	of CMS_add1_signer() is	to provide finer control over
       a CMS signed data structure where the simpler CMS_sign()	function
       defaults	are not	appropriate. For example if multiple signers or	non
       default digest algorithms are needed. New attributes can	also be	added
       using the returned CMS_SignerInfo structure and the CMS attribute
       utility functions or the	CMS signed receipt request functions.

       Any of the following flags (ored	together) can be passed	in the flags
       parameter.

       If CMS_REUSE_DIGEST is set then an attempt is made to copy the content
       digest value from the CMS_ContentInfo structure:	to add a signer	to an
       existing	structure.  An error occurs if a matching digest value cannot
       be found	to copy.  The returned CMS_ContentInfo structure will be valid
       and finalized when this flag is set.

       If CMS_PARTIAL is set in	addition to CMS_REUSE_DIGEST then the
       CMS_SignerInfo structure	will not be finalized so additional attributes
       can be added. In	this case an explicit call to CMS_SignerInfo_sign() is
       needed to finalize it.

       If CMS_NOCERTS is set the signer's certificate will not be included in
       the CMS_ContentInfo structure, the signer's certificate must still be
       supplied	in the signcert	parameter though. This can reduce the size of
       the signature if	the signers certificate	can be obtained	by other
       means: for example a previously signed message.

       The SignedData structure	includes several CMS signedAttributes
       including the signing time, the CMS content type	and the	supported list
       of ciphers in an	SMIMECapabilities attribute. If	CMS_NOATTR is set then
       no signedAttributes will	be used. If CMS_NOSMIMECAP is set then just
       the SMIMECapabilities are omitted.

       OpenSSL will by default identify	signing	certificates using issuer name
       and serial number. If CMS_USE_KEYID is set it will use the subject key
       identifier value	instead. An error occurs if the	signing	certificate
       does not	have a subject key identifier extension.

       If present the SMIMECapabilities	attribute indicates support for	the
       following algorithms in preference order: 256 bit AES, Gost R3411-94,
       Gost 28147-89, 192 bit AES, 128 bit AES,	triple DES, 128	bit RC2, 64
       bit RC2,	DES and	40 bit RC2.  If	any of these algorithms	is not
       available then it will not be included: for example the GOST algorithms
       will not	be included if the GOST	ENGINE is not loaded.

       CMS_add1_signer() returns an internal pointer to	the CMS_SignerInfo
       structure just added, this can be used to set additional	attributes
       before it is finalized.

RETURN VALUES
       CMS_add1_signer() returns an internal pointer to	the CMS_SignerInfo
       structure just added or NULL if an error	occurs.

SEE ALSO
       ERR_get_error(3), CMS_sign(3), CMS_final(3),

COPYRIGHT
       Copyright 2014-2016 The OpenSSL Project Authors.	All Rights Reserved.

       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
       <https://www.openssl.org/source/license.html>.

1.1.1a				  2018-11-20		    CMS_ADD1_SIGNER(3)

NAME | SYNOPSIS | DESCRIPTION | NOTES | RETURN VALUES | SEE ALSO | COPYRIGHT

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