path: root/lib/libcrypto/man/SMIME_write_PKCS7.3

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.Dd $Mdocdate: December 14 2021 $
.Dt SMIME_WRITE_PKCS7 3
.Os
.Sh NAME
.Nm SMIME_write_PKCS7
.Nd convert PKCS#7 structure to S/MIME format
.Sh SYNOPSIS
.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
adds the appropriate MIME headers to a PKCS#7 structure to produce an
S/MIME message.
.Pp
.Fa out
is the
.Vt BIO
to write the data to.
.Fa p7
is the appropriate
.Vt PKCS7
structure.
If streaming is enabled, then the content must be supplied in the
.Fa data
argument.
.Fa flags
is an optional set of flags.
.Pp
The following flags can be passed in the
.Fa flags
parameter.
.Pp
If
.Dv PKCS7_DETACHED
is set, then cleartext signing will be used.
This option only makes sense for signedData where
.Dv PKCS7_DETACHED
is also set when
.Xr PKCS7_sign 3
is also called.
.Pp
If the
.Dv PKCS7_TEXT
flag is set, MIME headers for type
.Sy text/plain
are added to the content.
This only makes sense if
.Dv PKCS7_DETACHED
is also set.
.Pp
If the
.Dv PKCS7_STREAM
flag is set, streaming is performed.
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 bit
.Dv SMIME_OLDMIME
is inverted before passing on the
.Fa flags
to
.Xr SMIME_write_ASN1 3 .
Consequently, 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.
.Pp
If cleartext signing is being used and
.Dv PKCS7_STREAM
is not set, then 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 streaming is performed, 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.
.Sh RETURN VALUES
Upon successful completion, 1 is returned;
otherwise 0 is returned and an error code can be retrieved with
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.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_read_PKCS7 3 ,
.Xr SMIME_write_ASN1 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
always base64 encodes PKCS#7 structures.
There should be an option to disable this.