.\" $OpenBSD: PKCS7_sign.3,v 1.13 2020/06/10 11:43:08 schwarze Exp $ .\" full merge up to: OpenSSL df75c2bf Dec 9 01:02:36 2018 +0100 .\" .\" This file was written by Dr. Stephen Henson . .\" Copyright (c) 2002, 2003, 2006-2009, 2015 The OpenSSL Project. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" .\" .\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to .\" endorse or promote products derived from this software without .\" prior written permission. For written permission, please contact .\" openssl-core@openssl.org. .\" .\" 5. Products derived from this software may not be called "OpenSSL" .\" nor may "OpenSSL" appear in their names without prior written .\" permission of the OpenSSL Project. .\" .\" 6. Redistributions of any form whatsoever must retain the following .\" acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" .\" .\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY .\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: June 10 2020 $ .Dt PKCS7_SIGN 3 .Os .Sh NAME .Nm PKCS7_sign .Nd create a PKCS#7 signedData structure .Sh SYNOPSIS .In openssl/pkcs7.h .Ft PKCS7 * .Fo PKCS7_sign .Fa "X509 *signcert" .Fa "EVP_PKEY *pkey" .Fa "STACK_OF(X509) *certs" .Fa "BIO *data" .Fa "int flags" .Fc .Sh DESCRIPTION .Fn PKCS7_sign creates and returns a PKCS#7 signedData structure. .Fa signcert is the certificate to sign with, .Fa pkey is the corresponding private key. .Fa certs is an optional additional set of certificates to include in the PKCS#7 structure (for example any intermediate CAs in the chain). .Pp The data to be signed is read from .Vt BIO .Fa data . .Pp .Fa flags is an optional set of flags. .Pp Any of the following flags (OR'ed together) can be passed in the .Fa flags parameter. .Pp Many S/MIME clients expect the signed content to include valid MIME headers. If the .Dv PKCS7_TEXT flag is set, MIME headers for type .Sy text/plain are prepended to the data. .Pp If .Dv PKCS7_NOCERTS is set, the signer's certificate will not be included in the PKCS7 structure, though the signer's certificate must still be supplied in the .Fa signcert parameter. This can reduce the size of the signature if the signer's certificate can be obtained by other means: for example a previously signed message. .Pp The data being signed is included in the .Vt PKCS7 structure, unless .Dv 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. .Pp Normally the supplied content is translated into MIME canonical format (as required by the S/MIME specifications). If .Dv 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. .Pp 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 .Dv PKCS7_NOATTR is set, then no authenticatedAttributes will be used. If .Dv PKCS7_NOSMIMECAP is set, then just the SMIMECapabilities are omitted. .Pp 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. .Pp If the flags .Dv PKCS7_STREAM is set, then the returned .Vt PKCS7 structure is just initialized ready to perform the signing operation. The signing is however .Sy not performed and the data to be signed is not read from the .Fa data parameter. Signing is deferred until after the data has been written. In this way data can be signed in a single pass. .Pp If the .Dv PKCS7_PARTIAL flag is set, a partial .Vt PKCS7 structure is output to which additional signers and capabilities can be added before finalization. .Pp If the flag .Dv PKCS7_STREAM is set, the returned .Vt PKCS7 structure is .Sy not complete and outputting its contents via a function that does not properly finalize the .Vt PKCS7 structure will give unpredictable results. .Pp Several functions including .Xr PKCS7_final 3 , .Xr SMIME_write_PKCS7 3 , .Xr PEM_write_bio_PKCS7_stream 3 , and .Xr i2d_PKCS7_bio_stream 3 finalize the structure. Alternatively finalization can be performed by obtaining the streaming ASN.1 .Vt BIO directly using .Fn BIO_new_PKCS7 . .Pp If a signer is specified, it will use the default digest for the signing algorithm. This is .Sy SHA1 for both RSA and DSA keys. .Pp In OpenSSL 1.0.0, the .Fa certs , .Fa signcert , and .Fa pkey parameters can all be .Dv NULL if the .Dv PKCS7_PARTIAL flag is set. One or more signers can be added using the function .Xr PKCS7_sign_add_signer 3 and attributes can be added using the functions described in .Xr PKCS7_add_attribute 3 . .Xr PKCS7_final 3 must also be called to finalize the structure if streaming is not enabled. Alternative signing digests can also be specified using this method. .Pp In OpenSSL 1.0.0, if .Fa signcert and .Fa pkey are .Dv NULL , then a certificate-only PKCS#7 structure is output. .Pp In versions of OpenSSL before 1.0.0 the .Fa signcert and .Fa pkey parameters must .Sy NOT be .Dv NULL . .Sh RETURN VALUES .Fn PKCS7_sign returns either a valid .Vt PKCS7 structure or .Dv NULL if an error occurred. The error can be obtained from .Xr ERR_get_error 3 . .Sh SEE ALSO .Xr PKCS7_add_attribute 3 , .Xr PKCS7_encrypt 3 , .Xr PKCS7_final 3 , .Xr PKCS7_get_signer_info 3 , .Xr PKCS7_new 3 , .Xr PKCS7_sign_add_signer 3 , .Xr PKCS7_verify 3 .Sh HISTORY .Fn PKCS7_sign first appeared in OpenSSL 0.9.5 and have been available since .Ox 2.7 . .Pp The .Dv PKCS7_PARTIAL and .Dv PKCS7_STREAM flags were added in OpenSSL 1.0.0. .Sh BUGS Some advanced attributes such as counter signatures are not supported.