Wed Feb 19 16:42:56 2003
Standard preamble:
======================================================================
\\$1
.. ..
.... 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 -- \(*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\} . 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.
. 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.
Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
Fear. Run. Save yourself. No user-serviceable parts.
.bd B 3 . \" fudge factors for nroff and troff . ds #H 0 . ds #V .8m . ds #F .3m . ds #[ \f1 . ds #] .\} . ds #H ((1u-(\\\\n(.fu%2u))*.13m) . ds #V .6m . ds #F 0 . ds #[ \& . ds #] \& .\} . \" simple accents for nroff and troff . ds ' \& . ds ` \& . ds ^ \& . ds , \& . ds ~ ~ . ds / .\} . 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 . \" corrections for vroff . \" for low resolution devices (crt and lpr) \{\ . 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 .\} ======================================================================
Title "PKCS7_sign 3"
The data to be signed is read from \s-1BIO\s0 data.
\fBflags is an optional set of flags.
Many S/MIME clients expect the signed content to include valid \s-1MIME\s0 headers. If the \s-1PKCS7_TEXT\s0 flag is set \s-1MIME\s0 headers for type text/plain are prepended to the data.
If \s-1PKCS7_NOCERTS\s0 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 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 \s-1PKCS7\s0 structure, unless \s-1PKCS7_DETACHED\s0 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.
Normally the supplied content is translated into \s-1MIME\s0 canonical format (as required by the S/MIME specifications) if \s-1PKCS7_BINARY\s0 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 autenticatedAttributes including the signing time, the PKCS#7 content type and the supported list of ciphers in an SMIMECapabilities attribute. If \s-1PKCS7_NOATTR\s0 is set then no authenticatedAttributes will be used. If \s-1PKCS7_NOSMIMECAP\s0 is set then just the SMIMECapabilities are omitted.
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.
The \s-1SHA1\s0 digest algorithm is currently always used.
When the signed data is not detached it will be stored in memory within the \fB\s-1PKCS7\s0 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.
Clear text signing does not store the content in memory but the way PKCS7_sign() 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.