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 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().
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 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
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.
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