26
Any of the following flags (ored together) can be passed in the B<flags> parameter.
26
Any of the following flags (ored together) can be passed in the B<flags>
28
29
Many S/MIME clients expect the signed content to include valid MIME headers. If
29
30
the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are prepended
32
33
If B<PKCS7_NOCERTS> is set the signer's certificate will not be included in the
33
PKCS7 structure, the signer's certificate must still be supplied in the B<signcert>
34
parameter though. This can reduce the size of the signature if the signers certificate
35
can be obtained by other means: for example a previously signed message.
37
The data being signed is included in the PKCS7 structure, unless B<PKCS7_DETACHED>
38
is set in which case it is omitted. This is used for PKCS7 detached signatures
39
which are used in S/MIME plaintext signed messages for example.
41
Normally the supplied content is translated into MIME canonical format (as required
42
by the S/MIME specifications) if B<PKCS7_BINARY> is set no translation occurs. This
43
option should be used if the supplied data is in binary format otherwise the translation
46
The signedData structure includes several PKCS#7 autenticatedAttributes including
47
the signing time, the PKCS#7 content type and the supported list of ciphers in
48
an SMIMECapabilities attribute. If B<PKCS7_NOATTR> is set then no authenticatedAttributes
49
will be used. If B<PKCS7_NOSMIMECAP> is set then just the SMIMECapabilities are
34
PKCS7 structure, the signer's certificate must still be supplied in the
35
B<signcert> parameter though. This can reduce the size of the signature if the
36
signers certificate can be obtained by other means: for example a previously
39
The data being signed is included in the PKCS7 structure, unless
40
B<PKCS7_DETACHED> is set in which case it is omitted. This is used for PKCS7
41
detached signatures which are used in S/MIME plaintext signed messages for
44
Normally the supplied content is translated into MIME canonical format (as
45
required by the S/MIME specifications) if B<PKCS7_BINARY> is set no translation
46
occurs. This option should be used if the supplied data is in binary format
47
otherwise the translation will corrupt it.
49
The signedData structure includes several PKCS#7 autenticatedAttributes
50
including the signing time, the PKCS#7 content type and the supported list of
51
ciphers in an SMIMECapabilities attribute. If B<PKCS7_NOATTR> is set then no
52
authenticatedAttributes will be used. If B<PKCS7_NOSMIMECAP> is set then just
53
the SMIMECapabilities are omitted.
52
55
If present the SMIMECapabilities attribute indicates support for the following
53
algorithms: triple DES, 128 bit RC2, 64 bit RC2, DES and 40 bit RC2. If any
54
of these algorithms is disabled then it will not be included.
56
If the flags B<PKCS7_PARTSIGN> is set then the returned B<PKCS7> structure
57
is just initialized ready to perform the signing operation. The signing
58
is however B<not> performed and the data to be signed is not read from
59
the B<data> parameter. Signing is deferred until after the data has been
60
written. In this way data can be signed in a single pass. Currently the
61
flag B<PKCS7_DETACHED> B<must> also be set.
56
algorithms: triple DES, 128 bit RC2, 64 bit RC2, DES and 40 bit RC2. If any of
57
these algorithms is disabled then it will not be included.
59
If the flags B<PKCS7_STREAM> is set then the returned B<PKCS7> structure is
60
just initialized ready to perform the signing operation. The signing is however
61
B<not> performed and the data to be signed is not read from the B<data>
62
parameter. Signing is deferred until after the data has been written. In this
63
way data can be signed in a single pass.
65
If the B<PKCS7_PARTIAL> flag is set a partial B<PKCS7> structure is output to
66
which additional signers and capabilities can be added before finalization.
65
Currently the flag B<PKCS7_PARTSIGN> is only supported for detached
66
data. If this flag is set the returned B<PKCS7> structure is B<not>
67
complete and outputting its contents via a function that does not
68
properly finalize the B<PKCS7> structure will give unpredictable
71
At present only the SMIME_write_PKCS7() function properly finalizes the
71
If the flag B<PKCS7_STREAM> is set the returned B<PKCS7> structure is B<not>
72
complete and outputting its contents via a function that does not properly
73
finalize the B<PKCS7> structure will give unpredictable results.
75
Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(),
76
PEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization
77
can be performed by obtaining the streaming ASN1 B<BIO> directly using
80
If a signer is specified it will use the default digest for the signing
81
algorithm. This is B<SHA1> for both RSA and DSA keys.
83
In OpenSSL 1.0.0 the B<certs>, B<signcert> and B<pkey> parameters can all be
84
B<NULL> if the B<PKCS7_PARTIAL> flag is set. One or more signers can be added
85
using the function B<PKCS7_sign_add_signer()>. B<PKCS7_final()> must also be
86
called to finalize the structure if streaming is not enabled. Alternative
87
signing digests can also be specified using this method.
89
In OpenSSL 1.0.0 if B<signcert> and B<pkey> are NULL then a certificates only
90
PKCS#7 structure is output.
92
In versions of OpenSSL before 1.0.0 the B<signcert> and B<pkey> parameters must
76
PKCS7_sign() is somewhat limited. It does not support multiple signers, some
77
advanced attributes such as counter signatures are not supported.
79
The SHA1 digest algorithm is currently always used.
81
When the signed data is not detached it will be stored in memory within the
82
B<PKCS7> structure. This effectively limits the size of messages which can be
83
signed due to memory restraints. There should be a way to sign data without
84
having to hold it all in memory, this would however require fairly major
85
revisions of the OpenSSL ASN1 code.
97
Some advanced attributes such as counter signatures are not supported.
88
99
=head1 RETURN VALUES
90
PKCS7_sign() returns either a valid PKCS7 structure or NULL if an error occurred.
91
The error can be obtained from ERR_get_error(3).
101
PKCS7_sign() returns either a valid PKCS7 structure or NULL if an error
102
occurred. The error can be obtained from ERR_get_error(3).