1CMS_ADD1_SIGNER(3)                  OpenSSL                 CMS_ADD1_SIGNER(3)
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NAME

6       CMS_add1_signer, CMS_SignerInfo_sign - add a signer to a
7       CMS_ContentInfo signed data structure
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SYNOPSIS

10        #include <openssl/cms.h>
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12        CMS_SignerInfo *CMS_add1_signer(CMS_ContentInfo *cms, X509 *signcert,
13                                        EVP_PKEY *pkey, const EVP_MD *md,
14                                        unsigned int flags);
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16        int CMS_SignerInfo_sign(CMS_SignerInfo *si);
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DESCRIPTION

19       CMS_add1_signer() adds a signer with certificate signcert and private
20       key pkey using message digest md to CMS_ContentInfo SignedData
21       structure cms.
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23       The CMS_ContentInfo structure should be obtained from an initial call
24       to CMS_sign() with the flag CMS_PARTIAL set or in the case or re-
25       signing a valid CMS_ContentInfo SignedData structure.
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27       If the md parameter is NULL then the default digest for the public key
28       algorithm will be used.
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30       Unless the CMS_REUSE_DIGEST flag is set the returned CMS_ContentInfo
31       structure is not complete and must be finalized either by streaming (if
32       applicable) or a call to CMS_final().
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34       The CMS_SignerInfo_sign() function will explicitly sign a
35       CMS_SignerInfo structure, its main use is when CMS_REUSE_DIGEST and
36       CMS_PARTIAL flags are both set.
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NOTES

39       The main purpose of CMS_add1_signer() is to provide finer control over
40       a CMS signed data structure where the simpler CMS_sign() function
41       defaults are not appropriate. For example if multiple signers or non
42       default digest algorithms are needed. New attributes can also be added
43       using the returned CMS_SignerInfo structure and the CMS attribute
44       utility functions or the CMS signed receipt request functions.
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46       Any of the following flags (ored together) can be passed in the flags
47       parameter.
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49       If CMS_REUSE_DIGEST is set then an attempt is made to copy the content
50       digest value from the CMS_ContentInfo structure: to add a signer to an
51       existing structure.  An error occurs if a matching digest value cannot
52       be found to copy.  The returned CMS_ContentInfo structure will be valid
53       and finalized when this flag is set.
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55       If CMS_PARTIAL is set in addition to CMS_REUSE_DIGEST then the
56       CMS_SignerInfo structure will not be finalized so additional attributes
57       can be added. In this case an explicit call to CMS_SignerInfo_sign() is
58       needed to finalize it.
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60       If CMS_NOCERTS is set the signer's certificate will not be included in
61       the CMS_ContentInfo structure, the signer's certificate must still be
62       supplied in the signcert parameter though. This can reduce the size of
63       the signature if the signers certificate can be obtained by other
64       means: for example a previously signed message.
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66       The SignedData structure includes several CMS signedAttributes
67       including the signing time, the CMS content type and the supported list
68       of ciphers in an SMIMECapabilities attribute. If CMS_NOATTR is set then
69       no signedAttributes will be used. If CMS_NOSMIMECAP is set then just
70       the SMIMECapabilities are omitted.
71
72       OpenSSL will by default identify signing certificates using issuer name
73       and serial number. If CMS_USE_KEYID is set it will use the subject key
74       identifier value instead. An error occurs if the signing certificate
75       does not have a subject key identifier extension.
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77       If present the SMIMECapabilities attribute indicates support for the
78       following algorithms in preference order: 256 bit AES, Gost R3411-94,
79       Gost 28147-89, 192 bit AES, 128 bit AES, triple DES, 128 bit RC2, 64
80       bit RC2, DES and 40 bit RC2.  If any of these algorithms is not
81       available then it will not be included: for example the GOST algorithms
82       will not be included if the GOST ENGINE is not loaded.
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84       CMS_add1_signer() returns an internal pointer to the CMS_SignerInfo
85       structure just added, this can be used to set additional attributes
86       before it is finalized.
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RETURN VALUES

89       CMS_add1_signer() returns an internal pointer to the CMS_SignerInfo
90       structure just added or NULL if an error occurs.
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SEE ALSO

93       ERR_get_error(3), CMS_sign(3), CMS_final(3),
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96       Copyright 2014-2016 The OpenSSL Project Authors. All Rights Reserved.
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98       Licensed under the OpenSSL license (the "License").  You may not use
99       this file except in compliance with the License.  You can obtain a copy
100       in the file LICENSE in the source distribution or at
101       <https://www.openssl.org/source/license.html>.
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1051.1.1i                            2021-07-22                CMS_ADD1_SIGNER(3)
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