NetBSD/lib/libcrypto/man/PKCS7_sign.3

.\"	$NetBSD: PKCS7_sign.3,v 1.4 2005/04/24 00:10:03 wiz Exp $
.\"
.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.14
.\"
.\" Standard preamble:
.\" ========================================================================
.de Sh \" Subsection heading
.br
.if t .Sp
.ne 5
.PP
\fB\\$1\fR
.PP
..
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R
.fi
..
.\" Set up some character translations and predefined strings.  \*(-- will
.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
.\" double quote, and \*(R" will give a right double quote.  | will give a
.\" real vertical bar.  \*(C+ will give a nicer C++.  Capital omega is used to
.\" do unbreakable dashes and therefore won't be available.  \*(C` and \*(C'
.\" expand to `' in nroff, nothing in troff, for use with C<>.
.tr \(*W-|\(bv\*(Tr
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.ie n \{\
.    ds -- \(*W-
.    ds PI pi
.    if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
.    if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\"  diablo 12 pitch
.    ds L" ""
.    ds R" ""
.    ds C` ""
.    ds C' ""
'br\}
.el\{\
.    ds -- \|\(em\|
.    ds PI \(*p
.    ds L" ``
.    ds R" ''
'br\}
.\"
.\" If the F register is turned on, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
.\" entries marked with X<> in POD.  Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
.if \nF \{\
.    de IX
.    tm Index:\\$1\t\\n%\t"\\$2"
..
.    nr % 0
.    rr F
.\}
.\"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.hy 0
.if n .na
.\"
.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
.\" Fear.  Run.  Save yourself.  No user-serviceable parts.
.    \" fudge factors for nroff and troff
.if n \{\
.    ds #H 0
.    ds #V .8m
.    ds #F .3m
.    ds #[ \f1
.    ds #] \fP
.\}
.if t \{\
.    ds #H ((1u-(\\\\n(.fu%2u))*.13m)
.    ds #V .6m
.    ds #F 0
.    ds #[ \&
.    ds #] \&
.\}
.    \" simple accents for nroff and troff
.if n \{\
.    ds ' \&
.    ds ` \&
.    ds ^ \&
.    ds , \&
.    ds ~ ~
.    ds /
.\}
.if t \{\
.    ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
.    ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
.    ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
.    ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
.    ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
.    ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
.\}
.    \" troff and (daisy-wheel) nroff accents
.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
.ds ae a\h'-(\w'a'u*4/10)'e
.ds Ae A\h'-(\w'A'u*4/10)'E
.    \" corrections for vroff
.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
.    \" for low resolution devices (crt and lpr)
.if \n(.H>23 .if \n(.V>19 \
\{\
.    ds : e
.    ds 8 ss
.    ds o a
.    ds d- d\h'-1'\(ga
.    ds D- D\h'-1'\(hy
.    ds th \o'bp'
.    ds Th \o'LP'
.    ds ae ae
.    ds Ae AE
.\}
.rm #[ #] #H #V #F C
.\" ========================================================================
.\"
.IX Title "PKCS7_sign 3"
.TH PKCS7_sign 3 "2003-07-24" "0.9.7g" "OpenSSL"
.SH "NAME"
PKCS7_sign \- create a PKCS#7 signedData structure
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
\&\s-1PKCS7\s0 *PKCS7_sign(X509 *signcert, \s-1EVP_PKEY\s0 *pkey, \s-1STACK_OF\s0(X509) *certs, \s-1BIO\s0 *data, int flags);
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fIPKCS7_sign()\fR creates and returns a PKCS#7 signedData structure. \fBsigncert\fR
is the certificate to sign with, \fBpkey\fR is the corresponsding private key.
\&\fBcerts\fR 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 \s-1BIO\s0 \fBdata\fR.
.PP
\&\fBflags\fR is an optional set of flags.
.SH "NOTES"
.IX Header "NOTES"
Any of the following flags (ored together) can be passed in the \fBflags\fR parameter.
.PP
Many S/MIME clients expect the signed content to include valid \s-1MIME\s0 headers. If
the \fB\s-1PKCS7_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are prepended
to the data.
.PP
If \fB\s-1PKCS7_NOCERTS\s0\fR is set the signer's certificate will not be included in the
\&\s-1PKCS7\s0 structure, the signer's certificate must still be supplied in the \fBsigncert\fR
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.
.PP
The data being signed is included in the \s-1PKCS7\s0 structure, unless \fB\s-1PKCS7_DETACHED\s0\fR 
is set in which case it is omitted. This is used for \s-1PKCS7\s0 detached signatures
which are used in S/MIME plaintext signed messages for example.
.PP
Normally the supplied content is translated into \s-1MIME\s0 canonical format (as required
by the S/MIME specifications) if \fB\s-1PKCS7_BINARY\s0\fR 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 autenticatedAttributes including
the signing time, the PKCS#7 content type and the supported list of ciphers in
an SMIMECapabilities attribute. If \fB\s-1PKCS7_NOATTR\s0\fR is set then no authenticatedAttributes
will be used. If \fB\s-1PKCS7_NOSMIMECAP\s0\fR is set then just the SMIMECapabilities are
omitted.
.PP
If present the SMIMECapabilities attribute indicates support for the following
algorithms: triple \s-1DES\s0, 128 bit \s-1RC2\s0, 64 bit \s-1RC2\s0, \s-1DES\s0 and 40 bit \s-1RC2\s0. If any
of these algorithms is disabled then it will not be included.
.SH "BUGS"
.IX Header "BUGS"
\&\fIPKCS7_sign()\fR is somewhat limited. It does not support multiple signers, some
advanced attributes such as counter signatures are not supported.
.PP
The \s-1SHA1\s0 digest algorithm is currently always used.
.PP
When the signed data is not detached it will be stored in memory within the
\&\fB\s-1PKCS7\s0\fR structure. This effectively limits the size of messages which can be
signed due to memory restraints. There should be a way to sign data without
having to hold it all in memory, this would however require fairly major
revisions of the OpenSSL \s-1ASN1\s0 code.
.PP
Clear text signing does not store the content in memory but the way \fIPKCS7_sign()\fR
operates means that two passes of the data must typically be made: one to compute
the signatures and a second to output the data along with the signature. There
should be a way to process the data with only a single pass.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fIPKCS7_sign()\fR returns either a valid \s-1PKCS7\s0 structure or \s-1NULL\s0 if an error occurred.
The error can be obtained from \fIERR_get_error\fR\|(3).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fIERR_get_error\fR\|(3), \fIPKCS7_verify\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fIPKCS7_sign()\fR was added to OpenSSL 0.9.5