Updated: 2022/Sep/29

Please read Privacy Policy. It's for your privacy.

PKCS7_sign_add_signer(3)            OpenSSL           PKCS7_sign_add_signer(3)

       PKCS7_sign_add_signer - add a signer PKCS7 signed data structure

       libcrypto, -lcrypto

        #include <openssl/pkcs7.h>

        PKCS7_SIGNER_INFO *PKCS7_sign_add_signer(PKCS7 *p7, X509 *signcert,
                                                 EVP_PKEY *pkey, const EVP_MD *md, int flags);

       PKCS7_sign_add_signer() adds a signer with certificate signcert and
       private key pkey using message digest md to a PKCS7 signed data
       structure p7.

       The PKCS7 structure should be obtained from an initial call to
       PKCS7_sign() with the flag PKCS7_PARTIAL set or in the case or re-
       signing a valid PKCS7 signed data structure.

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

       Unless the PKCS7_REUSE_DIGEST 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().

       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 flags

       If PKCS7_REUSE_DIGEST 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 PKCS7_PARTIAL is set in addition to PKCS7_REUSE_DIGEST then the
       PKCS7_SIGNER_INO 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 PKCS7_NOCERTS is set the signer's certificate will not be included
       in the PKCS7 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 PKCS#7
       authenticatedAttributes including the signing time, the PKCS#7 content
       type and the supported list of ciphers in an SMIMECapabilities
       attribute. If PKCS7_NOATTR is set then no authenticatedAttributes will
       be used. If PKCS7_NOSMIMECAP is set then just the SMIMECapabilities are

       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

       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.

       PKCS7_sign_add_signers() returns an internal pointer to the
       PKCS7_SIGNER_INFO structure just added or NULL if an error occurs.

       ERR_get_error(3), PKCS7_sign(3), PKCS7_final(3),

       The PPKCS7_sign_add_signer() function was added in OpenSSL 1.0.0.

       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

1.1.1i                            2019-03-12          PKCS7_sign_add_signer(3)