PKCS7_sign_add_signer(3)

NAME

       PKCS7_sign_add_signer - add a signer PKCS7 signed data structure.

SYNOPSIS

        #include <openssl/pkcs7.h>

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

DESCRIPTION

       PKCS7_sign_add_signer() adds a signer with certificate signcert and
       private key pkey using message digest md to a PKCS7 signed data struc-
       ture 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-sign-
       ing 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 applica-
       ble) or a call to PKCS7_final().

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 flags
       parameter.

       If PKCS7_REUSE_DIGEST is set then an attempt is made to copy the con-
       tent digest value from the PKCS7 struture: to add a signer to an exist-
       ing 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 sig-
       nature 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 PKCS7_NOATTR is
       set then no authenticatedAttributes will be used. If PKCS7_NOSMIMECAP
       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 addi-
       tional attributes before it is finalized.

RETURN VALUES

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

SEE ALSO

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

HISTORY

       PPKCS7_sign_add_signer() was added to OpenSSL 1.0.0

1.0.2t                            2019-09-10          PKCS7_sign_add_signer(3)