.\" $OpenBSD: PKCS7_sign_add_signer.3,v 1.13 2020/06/10 11:43:08 schwarze Exp $ .\" full merge up to: OpenSSL df75c2bf Dec 9 01:02:36 2018 +0100 .\" .\" This file was written by Dr. Stephen Henson . .\" Copyright (c) 2007, 2008, 2009, 2015 The OpenSSL Project. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. 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Redistributions of any form whatsoever must retain the following .\" acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" .\" .\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY .\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: June 10 2020 $ .Dt PKCS7_SIGN_ADD_SIGNER 3 .Os .Sh NAME .Nm PKCS7_sign_add_signer .Nd add a signer to a SignedData structure .Sh SYNOPSIS .In openssl/pkcs7.h .Ft PKCS7_SIGNER_INFO * .Fo PKCS7_sign_add_signer .Fa "PKCS7 *p7" .Fa "X509 *signcert" .Fa "EVP_PKEY *pkey" .Fa "const EVP_MD *md" .Fa "int flags" .Fc .Sh DESCRIPTION .Fn PKCS7_sign_add_signer adds a signer with certificate .Fa signcert and private key .Fa pkey using message digest .Fa md to a .Vt PKCS7 signed data structure .Fa p7 . .Pp The .Vt PKCS7 structure should be obtained from an initial call to .Xr PKCS7_sign 3 with the flag .Dv PKCS7_PARTIAL set or, in the case or re-signing, a valid .Vt PKCS7 signed data structure. .Pp If the .Fa md parameter is .Dv NULL , then the default digest for the public key algorithm will be used. .Pp Unless the .Dv PKCS7_REUSE_DIGEST flag is set, the returned .Dv PKCS7 structure is not complete and must be finalized either by streaming (if applicable) or by a call to .Xr PKCS7_final 3 . .Pp The main purpose of this function is to provide finer control over a PKCS#7 signed data structure where the simpler .Xr PKCS7_sign 3 function defaults are not appropriate, for example if multiple signers or non default digest algorithms are needed. .Pp Any of the following flags (OR'ed together) can be passed in the .Fa flags parameter. .Pp If .Dv PKCS7_REUSE_DIGEST is set, then an attempt is made to copy the content digest value from the .Vt 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 .Vt PKCS7 structure will be valid and finalized when this flag is set. .Pp If .Dv PKCS7_PARTIAL is set in addition to .Dv PKCS7_REUSE_DIGEST , then the .Dv PKCS7_SIGNER_INO structure will not be finalized, so additional attributes can be added. In this case an explicit call to .Fn PKCS7_SIGNER_INFO_sign is needed to finalize it. .Pp If .Dv PKCS7_NOCERTS is set, the signer's certificate will not be included in the .Vt PKCS7 structure, though the signer's certificate must still be supplied in the .Fa signcert parameter. This can reduce the size of the signature if the signers certificate can be obtained by other means: for example a previously signed message. .Pp 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 .Dv PKCS7_NOATTR is set, then no authenticatedAttributes will be used. If .Dv PKCS7_NOSMIMECAP is set, then just the SMIMECapabilities are omitted. .Pp 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. .Pp .Fn PKCS7_sign_add_signer returns an internal pointer to the .Vt PKCS7_SIGNER_INFO structure just added, which can be used to set additional attributes with the functions described in .Xr PKCS7_add_attribute 3 before it is finalized. .Sh RETURN VALUES .Fn PKCS7_sign_add_signer returns an internal pointer to the .Vt PKCS7_SIGNER_INFO structure just added or .Dv NULL if an error occurs. In some cases of failure, the reason can be determined with .Xr ERR_get_error 3 . .Sh SEE ALSO .Xr EVP_DigestInit 3 , .Xr PKCS7_add_attribute 3 , .Xr PKCS7_final 3 , .Xr PKCS7_get_signer_info 3 , .Xr PKCS7_new 3 , .Xr PKCS7_sign 3 .Sh HISTORY .Fn PKCS7_sign_add_signer first appeared in OpenSSL 1.0.0 and has been available since .Ox 4.9 .