.\" $OpenBSD: SMIME_write_PKCS7.3,v 1.12 2025/06/11 23:16:32 schwarze Exp $ .\" full merge up to: OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400 .\" .\" This file is a derived work. .\" The changes are covered by the following Copyright and license: .\" .\" Copyright (c) 2021, 2025 Ingo Schwarze .\" .\" Permission to use, copy, modify, and distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS. 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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 11 2025 $ .Dt SMIME_WRITE_PKCS7 3 .Os .Sh NAME .Nm SMIME_write_PKCS7 .Nd convert PKCS#7 structure to S/MIME format .Sh SYNOPSIS .Lb libcrypto .In openssl/pkcs7.h .Ft int .Fo SMIME_write_PKCS7 .Fa "BIO *out" .Fa "PKCS7 *p7" .Fa "BIO *data" .Fa "int flags" .Fc .Sh DESCRIPTION .Fn SMIME_write_PKCS7 generates an S/MIME message on .Fa out by writing MIME 1.0 headers followed by a BER- and base64-encoded serialization of .Fa p7 . The BER encoding uses the DER format except as described for .Dv PKCS7_STREAM below. If streaming is enabled, then the content must be supplied in the .Fa data argument. .Pp The .Fa flags can be the logical OR of zero or more of the following bits: .Bl -tag -width Ds .It Dv PKCS7_DETACHED Use cleartext signing and generate a .Qq multipart/signed S/MIME message. The content is read from .Fa data . If .Fa data is a .Dv NULL pointer, this flag is ignored. .Pp This flag is only supported for signedData where .Dv PKCS7_DETACHED is also set when .Xr PKCS7_sign 3 is called. .Pp If .Dv PKCS7_STREAM is not set, the data must be read twice: once to compute the signature in .Xr PKCS7_sign 3 and once to output the S/MIME message. .Pp If .Dv PKCS7_DETACHED is ignored or not specified, the smime-type is chosen according to the type of .Fa p7 : .Bl -tag -width Ds .It Dv NID_pkcs7_enveloped .Qq enveloped-data .It Dv NID_pkcs7_signed .Bl -tag -width Msigned-dataM -compact .It Qq signed-data if .Fa p7 specifies any digest algorithm .It Qq certs-only otherwise .El .It Dv NID_id_smime_ct_compressedData .Qq compressed-data .El .It Dv PKCS7_REUSE_DIGEST Skip the calls to .Xr PKCS7_dataInit 3 and .Xr PKCS7_dataFinal 3 . This flag has no effect unless .Dv PKCS7_DETACHED is also set. .It Dv PKCS7_STREAM Perform streaming by reading the content from .Fa data . This only works if .Dv PKCS7_DETACHED is not specified. .Pp This flag should only be set if .Dv PKCS7_STREAM was also set in the previous call to .Xr PKCS7_sign 3 or .Xr PKCS7_encrypt 3 . .Pp The content is output in BER format using indefinite length constructed encoding except in the case of signed data with detached content where the content is absent and DER format is used. .It Dv PKCS7_TEXT Prepend the line .Qq Content-Type: text/plain to the content. This only makes sense if .Dv PKCS7_DETACHED is also set. It is ignored if the flag .Dv SMIME_BINARY is also set. .It Dv SMIME_BINARY If specified, this flag is passed through to .Xr SMIME_crlf_copy 3 . .It Dv SMIME_CRLFEOL End MIME header lines with pairs of carriage return and newline characters. By default, no carriage return characters are written and header lines are ended with newline characters only. .It Dv SMIME_OLDMIME If this bit is set in the .Fa flags argument, .Qq application/pkcs7-mime or .Qq application/pkcs7-signature is used in Content-Type headers. Otherwise, .Qq application/x-pkcs7-mime or .Qq application/x-pkcs7-signature is used. .El .Sh RETURN VALUES .Fn SMIME_write_PKCS7 is intended to return 1 on success or 0 on failure. .Sh SEE ALSO .Xr BIO_f_base64 3 , .Xr BIO_new 3 , .Xr i2d_PKCS7_bio_stream 3 , .Xr PEM_write_bio_PKCS7_stream 3 , .Xr PEM_write_PKCS7 3 , .Xr PKCS7_final 3 , .Xr PKCS7_new 3 , .Xr SMIME_crlf_copy 3 , .Xr SMIME_read_PKCS7 3 , .Xr SMIME_write_CMS 3 .Sh HISTORY .Fn SMIME_write_PKCS7 first appeared in OpenSSL 0.9.5 and has been available since .Ox 2.7 . .Sh BUGS .Fn SMIME_write_PKCS7 ignores most errors and is likely to return 1 even after producing corrupt or incomplete output. .Pp .Fn SMIME_write_PKCS7 always base64 encodes PKCS#7 structures. There should be an option to disable this.