PKCS7_sign_add_signer(3)     OpenSSL     PKCS7_sign_add_signer(3)


     PKCS7_sign_add_signer - add a signer PKCS7 signed data


      #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 parameter.

     If PKCS7_REUSE_DIGEST is set then an attempt is made to copy
     the content digest value from the PKCS7 struture: 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

1.0.2t               Last change: 2019-09-10                    1

PKCS7_sign_add_signer(3)     OpenSSL     PKCS7_sign_add_signer(3)

     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 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


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


     PPKCS7_sign_add_signer() was added to OpenSSL 1.0.0

1.0.2t               Last change: 2019-09-10                    2

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