Updated: 2021/Apr/14


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 corresponding
       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
       authenticatedAttributes 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.

       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.

       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
       The PKCS7_PARTIAL flag, and the ability for certs, signcert, and pkey
       parameters to be NULL were added in OpenSSL 1.0.0.

       The PKCS7_STREAM flag was added in OpenSSL 1.0.0.

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
       <https://www.openssl.org/source/license.html>.



1.1.1i                            2019-03-12                     PKCS7_sign(3)