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CMS_add1_signer(3)                  OpenSSL                 CMS_add1_signer(3)



NAME
        CMS_add1_signer, CMS_SignerInfo_sign - add a signer to a CMS_ContentInfo signed data structure.

LIBRARY
       libcrypto, -lcrypto

SYNOPSIS
        #include <openssl/cms.h>

        CMS_SignerInfo *CMS_add1_signer(CMS_ContentInfo *cms, X509 *signcert, EVP_PKEY *pkey, const EVP_MD *md, unsigned int flags);

        int CMS_SignerInfo_sign(CMS_SignerInfo *si);

DESCRIPTION
       CMS_add1_signer() adds a signer with certificate signcert and private
       key pkey using message digest md to CMS_ContentInfo SignedData
       structure cms.

       The CMS_ContentInfo structure should be obtained from an initial call
       to CMS_sign() with the flag CMS_PARTIAL set or in the case or re-
       signing a valid CMS_ContentInfo SignedData structure.

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

       Unless the CMS_REUSE_DIGEST flag is set the returned CMS_ContentInfo
       structure is not complete and must be finalized either by streaming (if
       applicable) or a call to CMS_final().

       The CMS_SignerInfo_sign() function will explicitly sign a
       CMS_SignerInfo structure, its main use is when CMS_REUSE_DIGEST and
       CMS_PARTIAL flags are both set.

NOTES
       The main purpose of CMS_add1_signer() is to provide finer control over
       a CMS signed data structure where the simpler CMS_sign() function
       defaults are not appropriate. For example if multiple signers or non
       default digest algorithms are needed. New attributes can also be added
       using the returned CMS_SignerInfo structure and the CMS attribute
       utility functions or the CMS signed receipt request functions.

       Any of the following flags (ored together) can be passed in the flags
       parameter.

       If CMS_REUSE_DIGEST is set then an attempt is made to copy the content
       digest value from the CMS_ContentInfo structure: to add a signer to an
       existing structure.  An error occurs if a matching digest value cannot
       be found to copy.  The returned CMS_ContentInfo structure will be valid
       and finalized when this flag is set.

       If CMS_PARTIAL is set in addition to CMS_REUSE_DIGEST then the
       CMS_SignerInfo structure will not be finalized so additional attributes
       can be added. In this case an explicit call to CMS_SignerInfo_sign() is
       needed to finalize it.

       If CMS_NOCERTS is set the signer's certificate will not be included in
       the CMS_ContentInfo 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 CMS signedAttributes
       including the signing time, the CMS content type and the supported list
       of ciphers in an SMIMECapabilities attribute. If CMS_NOATTR is set then
       no signedAttributes will be used. If CMS_NOSMIMECAP is set then just
       the SMIMECapabilities are omitted.

       OpenSSL will by default identify signing certificates using issuer name
       and serial number. If CMS_USE_KEYID is set it will use the subject key
       identifier value instead. An error occurs if the signing certificate
       does not have a subject key identifier extension.

       If present the SMIMECapabilities attribute indicates support for the
       following algorithms in preference order: 256 bit AES, Gost R3411-94,
       Gost 28147-89, 192 bit AES, 128 bit AES, triple DES, 128 bit RC2, 64
       bit RC2, DES and 40 bit RC2. If any of these algorithms is not
       available then it will not be included: for example the GOST algorithms
       will not be included if the GOST ENGINE is not loaded.

       CMS_add1_signer() returns an internal pointer to the CMS_SignerInfo
       structure just added, this can be used to set additional attributes
       before it is finalized.

RETURN VALUES
       CMS_add1_signer() returns an internal pointer to the CMS_SignerInfo
       structure just added or NULL if an error occurs.

SEE ALSO
       ERR_get_error(3), CMS_sign(3), CMS_final(3),

HISTORY
       CMS_add1_signer() was added to OpenSSL 0.9.8



1.0.1u                            2015-04-29                CMS_add1_signer(3)