/usr/man/cat.3/CMS_add1_signer.3

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.

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.

1.0.2t               Last change: 2019-09-10                    1

CMS_add1_signer(3)           OpenSSL           CMS_add1_signer(3)

     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

1.0.2t               Last change: 2019-09-10                    2

See also CMS_SignerInfo_sign(3)