=pod =head1 NAME PKCS7_sign - create a PKCS#7 signedData structure =head1 SYNOPSIS #include PKCS7 *PKCS7_sign(X509 *signcert, EVP_PKEY *pkey, STACK_OF(X509) *certs, BIO *data, int flags); =head1 DESCRIPTION PKCS7_sign() creates and returns a PKCS#7 signedData structure. B is the certificate to sign with, B is the corresponding private key. B 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 B. B is an optional set of flags. =head1 NOTES Any of the following flags (ored together) can be passed in the B parameter. Many S/MIME clients expect the signed content to include valid MIME headers. If the B flag is set MIME headers for type B are prepended to the data. If B is set the signer's certificate will not be included in the PKCS7 structure, the signer's certificate must still be supplied in the B 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 B 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 B 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 B is set then no authenticatedAttributes will be used. If B 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 B is set then the returned B structure is just initialized ready to perform the signing operation. The signing is however B performed and the data to be signed is not read from the B parameter. Signing is deferred until after the data has been written. In this way data can be signed in a single pass. If the B flag is set a partial B structure is output to which additional signers and capabilities can be added before finalization. =head1 NOTES If the flag B is set the returned B structure is B complete and outputting its contents via a function that does not properly finalize the B 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 B directly using BIO_new_PKCS7(). If a signer is specified it will use the default digest for the signing algorithm. This is B for both RSA and DSA keys. The B, B and B parameters can all be B if the B 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. If B and B are NULL then a certificates only PKCS#7 structure is output. In versions of OpenSSL before 1.0.0 the B and B parameters must B be NULL. =head1 BUGS Some advanced attributes such as counter signatures are not supported. =head1 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). =head1 SEE ALSO L, L =head1 HISTORY The B flag, and the ability for B, B, and B parameters to be B to be was added in OpenSSL 1.0.0 The B flag was added in OpenSSL 1.0.0 =head1 COPYRIGHT Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved. Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at L. =cut