pkcs7_sign_add_signer(3ssl) [linux 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 1.0.0e 2009-09-30 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 LIBRARY
libcrypto, -lcrypto SYNOPSIS
#include <openssl/pkcs7.h> 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 private 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 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 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 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. If the flags PKCS7_STREAM is set then the returned PKCS7 structure is just initialized ready to perform the signing operation. The signing is however not performed and the data to be signed is not read from the data parameter. Signing is deferred until after the data has been written. In this way data can be signed in a single pass. If the PKCS7_PARTIAL flag is set a partial PKCS7 structure is output to which additional signers and capabilities can be added before finalization. NOTES
If the flag PKCS7_STREAM is set the returned PKCS7 structure is not complete and outputting its contents via a function that does not properly finalize the PKCS7 structure will give unpredictable results. Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(), PEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization can be performed by obtaining the streaming ASN1 BIO directly using BIO_new_PKCS7(). If a signer is specified it will use the default digest for the signing algorithm. This is SHA1 for both RSA and DSA keys. In OpenSSL 1.0.0 the certs, signcert and pkey parameters can all be NULL if the PKCS7_PARTIAL flag is set. One or more signers can be added using the function PKCS7_sign_add_signer(). PKCS7_final() must also be called to finalize the structure if streaming is not enabled. Alternative signing digests can also be specified using this method. In OpenSSL 1.0.0 if signcert and pkey are NULL then a certificates only PKCS#7 structure is output. In versions of OpenSSL before 1.0.0 the signcert and pkey parameters must NOT be NULL. BUGS
Some advanced attributes such as counter signatures are not supported. 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 The PKCS7_PARTIAL flag was added in OpenSSL 1.0.0 The PKCS7_STREAM flag was added in OpenSSL 1.0.0 1.0.1i 2010-01-06 PKCS7_sign(3)