1=pod 2 3=head1 NAME 4 5CMS_add1_signer, CMS_SignerInfo_sign - add a signer to a CMS_ContentInfo signed data structure 6 7=head1 SYNOPSIS 8 9 #include <openssl/cms.h> 10 11 CMS_SignerInfo *CMS_add1_signer(CMS_ContentInfo *cms, X509 *signcert, 12 EVP_PKEY *pkey, const EVP_MD *md, 13 unsigned int flags); 14 15 int CMS_SignerInfo_sign(CMS_SignerInfo *si); 16 17=head1 DESCRIPTION 18 19CMS_add1_signer() adds a signer with certificate B<signcert> and private 20key B<pkey> using message digest B<md> to CMS_ContentInfo SignedData 21structure B<cms>. 22 23The CMS_ContentInfo structure should be obtained from an initial call to 24CMS_sign() with the flag B<CMS_PARTIAL> set or in the case or re-signing a 25valid CMS_ContentInfo SignedData structure. 26 27If the B<md> parameter is B<NULL> then the default digest for the public 28key algorithm will be used. 29 30Unless the B<CMS_REUSE_DIGEST> flag is set the returned CMS_ContentInfo 31structure is not complete and must be finalized either by streaming (if 32applicable) or a call to CMS_final(). 33 34The CMS_SignerInfo_sign() function will explicitly sign a CMS_SignerInfo 35structure, its main use is when B<CMS_REUSE_DIGEST> and B<CMS_PARTIAL> flags 36are both set. 37 38=head1 NOTES 39 40The main purpose of CMS_add1_signer() is to provide finer control 41over a CMS signed data structure where the simpler CMS_sign() function defaults 42are not appropriate. For example if multiple signers or non default digest 43algorithms are needed. New attributes can also be added using the returned 44CMS_SignerInfo structure and the CMS attribute utility functions or the 45CMS signed receipt request functions. 46 47Any of the following flags (ored together) can be passed in the B<flags> 48parameter. 49 50If B<CMS_REUSE_DIGEST> is set then an attempt is made to copy the content 51digest value from the CMS_ContentInfo structure: to add a signer to an existing 52structure. An error occurs if a matching digest value cannot be found to copy. 53The returned CMS_ContentInfo structure will be valid and finalized when this 54flag is set. 55 56If B<CMS_PARTIAL> is set in addition to B<CMS_REUSE_DIGEST> then the 57CMS_SignerInfo structure will not be finalized so additional attributes 58can be added. In this case an explicit call to CMS_SignerInfo_sign() is 59needed to finalize it. 60 61If B<CMS_NOCERTS> is set the signer's certificate will not be included in the 62CMS_ContentInfo structure, the signer's certificate must still be supplied in 63the B<signcert> parameter though. This can reduce the size of the signature if 64the signers certificate can be obtained by other means: for example a 65previously signed message. 66 67The SignedData structure includes several CMS signedAttributes including the 68signing time, the CMS content type and the supported list of ciphers in an 69SMIMECapabilities attribute. If B<CMS_NOATTR> is set then no signedAttributes 70will be used. If B<CMS_NOSMIMECAP> is set then just the SMIMECapabilities are 71omitted. 72 73OpenSSL will by default identify signing certificates using issuer name 74and serial number. If B<CMS_USE_KEYID> is set it will use the subject key 75identifier value instead. An error occurs if the signing certificate does not 76have a subject key identifier extension. 77 78If present the SMIMECapabilities attribute indicates support for the following 79algorithms in preference order: 256 bit AES, Gost R3411-94, Gost 28147-89, 192 80bit AES, 128 bit AES, triple DES, 128 bit RC2, 64 bit RC2, DES and 40 bit RC2. 81If 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 82not loaded. 83 84CMS_add1_signer() returns an internal pointer to the CMS_SignerInfo 85structure just added, this can be used to set additional attributes 86before it is finalized. 87 88=head1 RETURN VALUES 89 90CMS_add1_signer() returns an internal pointer to the CMS_SignerInfo 91structure just added or NULL if an error occurs. 92 93=head1 SEE ALSO 94 95L<ERR_get_error(3)>, L<CMS_sign(3)>, 96L<CMS_final(3)>, 97 98=head1 COPYRIGHT 99 100Copyright 2014-2016 The OpenSSL Project Authors. All Rights Reserved. 101 102Licensed under the OpenSSL license (the "License"). You may not use 103this file except in compliance with the License. You can obtain a copy 104in the file LICENSE in the source distribution or at 105L<https://www.openssl.org/source/license.html>. 106 107=cut 108