Index: openssl/doc/crypto/PKCS7_sign.pod |
=================================================================== |
--- openssl/doc/crypto/PKCS7_sign.pod (revision 105093) |
+++ openssl/doc/crypto/PKCS7_sign.pod (working copy) |
@@ -12,10 +12,10 @@ |
=head1 DESCRIPTION |
-PKCS7_sign() creates and returns a PKCS#7 signedData structure. B<signcert> |
-is the certificate to sign with, B<pkey> is the corresponsding private key. |
-B<certs> is an optional additional set of certificates to include in the |
-PKCS#7 structure (for example any intermediate CAs in the chain). |
+PKCS7_sign() creates and returns a PKCS#7 signedData structure. B<signcert> is |
+the certificate to sign with, B<pkey> is the corresponsding private key. |
+B<certs> is an optional additional set of certificates to include in the PKCS#7 |
+structure (for example any intermediate CAs in the chain). |
The data to be signed is read from BIO B<data>. |
@@ -23,72 +23,83 @@ |
=head1 NOTES |
-Any of the following flags (ored together) can be passed in the B<flags> parameter. |
+Any of the following flags (ored together) can be passed in the B<flags> |
+parameter. |
Many S/MIME clients expect the signed content to include valid MIME headers. If |
the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are prepended |
to the data. |
If B<PKCS7_NOCERTS> is set the signer's certificate will not be included in the |
-PKCS7 structure, the signer's certificate must still be supplied in the B<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. |
+PKCS7 structure, the signer's certificate must still be supplied in the |
+B<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 PKCS7 structure, unless B<PKCS7_DETACHED> |
-is set in which case it is omitted. This is used for PKCS7 detached signatures |
-which are used in S/MIME plaintext signed messages for example. |
+The data being signed is included in the PKCS7 structure, unless |
+B<PKCS7_DETACHED> is set in which case it is omitted. This is used for PKCS7 |
+detached signatures which are used in S/MIME plaintext signed messages for |
+example. |
-Normally the supplied content is translated into MIME canonical format (as required |
-by the S/MIME specifications) if B<PKCS7_BINARY> is set no translation occurs. This |
-option should be used if the supplied data is in binary format otherwise the translation |
-will corrupt it. |
+Normally the supplied content is translated into MIME canonical format (as |
+required by the S/MIME specifications) if B<PKCS7_BINARY> 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 B<PKCS7_NOATTR> is set then no authenticatedAttributes |
-will be used. If B<PKCS7_NOSMIMECAP> is set then just the SMIMECapabilities are |
-omitted. |
+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 B<PKCS7_NOATTR> is set then no |
+authenticatedAttributes will be used. If B<PKCS7_NOSMIMECAP> is set then just |
+the SMIMECapabilities are omitted. |
If present the SMIMECapabilities attribute indicates support for the following |
-algorithms: triple DES, 128 bit RC2, 64 bit RC2, DES and 40 bit RC2. If any |
-of these algorithms is disabled then it will not be included. |
+algorithms: triple DES, 128 bit RC2, 64 bit RC2, DES and 40 bit RC2. If any of |
+these algorithms is disabled then it will not be included. |
-If the flags B<PKCS7_PARTSIGN> is set then the returned B<PKCS7> structure |
-is just initialized ready to perform the signing operation. The signing |
-is however B<not> performed and the data to be signed is not read from |
-the B<data> parameter. Signing is deferred until after the data has been |
-written. In this way data can be signed in a single pass. Currently the |
-flag B<PKCS7_DETACHED> B<must> also be set. |
+If the flags B<PKCS7_STREAM> is set then the returned B<PKCS7> structure is |
+just initialized ready to perform the signing operation. The signing is however |
+B<not> performed and the data to be signed is not read from the B<data> |
+parameter. Signing is deferred until after the data has been written. In this |
+way data can be signed in a single pass. |
+If the B<PKCS7_PARTIAL> flag is set a partial B<PKCS7> structure is output to |
+which additional signers and capabilities can be added before finalization. |
+ |
+ |
=head1 NOTES |
-Currently the flag B<PKCS7_PARTSIGN> is only supported for detached |
-data. If this flag is set the returned B<PKCS7> structure is B<not> |
-complete and outputting its contents via a function that does not |
-properly finalize the B<PKCS7> structure will give unpredictable |
-results. |
+If the flag B<PKCS7_STREAM> is set the returned B<PKCS7> structure is B<not> |
+complete and outputting its contents via a function that does not properly |
+finalize the B<PKCS7> structure will give unpredictable results. |
-At present only the SMIME_write_PKCS7() function properly finalizes the |
-structure. |
+Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(), |
+PEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization |
+can be performed by obtaining the streaming ASN1 B<BIO> directly using |
+BIO_new_PKCS7(). |
-=head1 BUGS |
+If a signer is specified it will use the default digest for the signing |
+algorithm. This is B<SHA1> for both RSA and DSA keys. |
-PKCS7_sign() is somewhat limited. It does not support multiple signers, some |
-advanced attributes such as counter signatures are not supported. |
+In OpenSSL 1.0.0 the B<certs>, B<signcert> and B<pkey> parameters can all be |
+B<NULL> if the B<PKCS7_PARTIAL> flag is set. One or more signers can be added |
+using the function B<PKCS7_sign_add_signer()>. B<PKCS7_final()> must also be |
+called to finalize the structure if streaming is not enabled. Alternative |
+signing digests can also be specified using this method. |
-The SHA1 digest algorithm is currently always used. |
+In OpenSSL 1.0.0 if B<signcert> and B<pkey> are NULL then a certificates only |
+PKCS#7 structure is output. |
-When the signed data is not detached it will be stored in memory within the |
-B<PKCS7> 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 ASN1 code. |
+In versions of OpenSSL before 1.0.0 the B<signcert> and B<pkey> parameters must |
+B<NOT> be NULL. |
+=head1 BUGS |
+Some advanced attributes such as counter signatures are not supported. |
+ |
=head1 RETURN VALUES |
-PKCS7_sign() returns either a valid PKCS7 structure or NULL if an error occurred. |
-The error can be obtained from ERR_get_error(3). |
+PKCS7_sign() returns either a valid PKCS7 structure or NULL if an error |
+occurred. The error can be obtained from ERR_get_error(3). |
=head1 SEE ALSO |
@@ -98,6 +109,8 @@ |
PKCS7_sign() was added to OpenSSL 0.9.5 |
-The B<PKCS7_PARTSIGN> flag was added in OpenSSL 0.9.8 |
+The B<PKCS7_PARTIAL> flag was added in OpenSSL 1.0.0 |
+The B<PKCS7_STREAM> flag was added in OpenSSL 1.0.0 |
+ |
=cut |