=pod =head1 NAME PKCS7_sign_add_signer - add a signer PKCS7 signed data structure =head1 SYNOPSIS #include PKCS7_SIGNER_INFO *PKCS7_sign_add_signer(PKCS7 *p7, X509 *signcert, EVP_PKEY *pkey, const EVP_MD *md, int flags); =head1 DESCRIPTION PKCS7_sign_add_signer() adds a signer with certificate B and private key B using message digest B to a PKCS7 signed data structure B. The PKCS7 structure should be obtained from an initial call to PKCS7_sign() with the flag B set or in the case or re-signing a valid PKCS7 signed data structure. If the B parameter is B then the default digest for the public key algorithm will be used. Unless the B flag is set the returned PKCS7 structure is not complete and must be finalized either by streaming (if applicable) or a call to PKCS7_final(). =head1 NOTES The main purpose of this function is to provide finer control over a PKCS#7 signed data structure where the simpler PKCS7_sign() function defaults are not appropriate. For example if multiple signers or non default digest algorithms are needed. Any of the following flags (ored together) can be passed in the B parameter. If B is set then an attempt is made to copy the content digest value from the PKCS7 structure: to add a signer to an existing structure. An error occurs if a matching digest value cannot be found to copy. The returned PKCS7 structure will be valid and finalized when this flag is set. If B is set in addition to B then the B structure will not be finalized so additional attributes can be added. In this case an explicit call to PKCS7_SIGNER_INFO_sign() is needed to finalize it. If B is set the signer's certificate will not be included in the PKCS7 structure, the signer's certificate must still be supplied in the B 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 PKCS#7 autenticatedAttributes including the signing time, the PKCS#7 content type and the supported list of ciphers in an SMIMECapabilities attribute. If B is set then no authenticatedAttributes will be used. If B is set then just the SMIMECapabilities are omitted. 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. PKCS7_sign_add_signers() returns an internal pointer to the PKCS7_SIGNER_INFO structure just added, this can be used to set additional attributes before it is finalized. =head1 RETURN VALUES PKCS7_sign_add_signers() returns an internal pointer to the PKCS7_SIGNER_INFO structure just added or NULL if an error occurs. =head1 SEE ALSO L, L, L, =head1 HISTORY PPKCS7_sign_add_signer() was added to OpenSSL 1.0.0 =head1 COPYRIGHT Copyright 2007-2016 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 L. =cut