pkcs7_sign_add_signer(3ssl) [debian man page]
PKCS7_sign_add_signer(3SSL) OpenSSL PKCS7_sign_add_signer(3SSL) 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 1.0.1e 2013-02-11 PKCS7_sign_add_signer(3SSL)
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PKCS7_sign(3) OpenSSL PKCS7_sign(3) NAME
PKCS7_sign - create a PKCS#7 signedData structure SYNOPSIS
PKCS7 *PKCS7_sign(X509 *signcert, EVP_PKEY *pkey, STACK_OF(X509) *certs, BIO *data, int flags); DESCRIPTION
PKCS7_sign() creates and returns a PKCS#7 signedData structure. signcert is the certificate to sign with, pkey is the corresponsding pri- vate key. certs is an optional additional set of certificates to include in the PKCS#7 structure (for example any intermediate CAs in the chain). The data to be signed is read from BIO data. flags is an optional set of flags. NOTES
Any of the following flags (ored together) can be passed in the flags parameter. Many S/MIME clients expect the signed content to include valid MIME headers. If the PKCS7_TEXT flag is set MIME headers for type text/plain are prepended to the data. If PKCS7_NOCERTS is set the signer's certificate will not be included in the PKCS7 structure, the signer's certificate must still be sup- plied 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 data being signed is included in the PKCS7 structure, unless PKCS7_DETACHED is set in which case it is omitted. This is used for PKCS7 detached signatures which are used in S/MIME plaintext signed messages for example. Normally the supplied content is translated into MIME canonical format (as required by the S/MIME specifications) if PKCS7_BINARY is set no translation occurs. This option should be used if the supplied data is in binary format otherwise the translation will corrupt it. The signedData structure includes several PKCS#7 autenticatedAttributes including the signing time, the PKCS#7 content type and the sup- ported 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. BUGS
PKCS7_sign() is somewhat limited. It does not support multiple signers, some advanced attributes such as counter signatures are not sup- ported. The SHA1 digest algorithm is currently always used. When the signed data is not detached it will be stored in memory within the PKCS7 structure. This effectively limits the size of messages which can be signed due to memory restraints. There should be a way to sign data without having to hold it all in memory, this would how- ever require fairly major revisions of the OpenSSL ASN1 code. Clear text signing does not store the content in memory but the way PKCS7_sign() operates means that two passes of the data must typically be made: one to compute the signatures and a second to output the data along with the signature. There should be a way to process the data with only a single pass. RETURN VALUES
PKCS7_sign() returns either a valid PKCS7 structure or NULL if an error occurred. The error can be obtained from ERR_get_error(3). SEE ALSO
ERR_get_error(3), PKCS7_verify(3) HISTORY
PKCS7_sign() was added to OpenSSL 0.9.5 0.9.7a 2002-10-09 PKCS7_sign(3)