CMS_sign_add1_signerNameCMS_sign_add1_signer, CMS_SignerInfo_sign -- add a signer to a CMS_ContentInfo signed data structure. SynopsisCMS_SignerInfo *CMS_sign_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_sign_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_sign_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_sign_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_sign1_add_signers() returns an internal pointer to the
CMS_SignerInfo structure just added or NULL if an error occurs.
HISTORY CMS_sign_add1_signer() was added to OpenSSL 0.9.8
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