| =pod |
| |
| =head1 NAME |
| |
| PKCS7_sign - create a PKCS#7 signedData structure |
| |
| =head1 SYNOPSIS |
| |
| #include <openssl/pkcs7.h> |
| |
| PKCS7 *PKCS7_sign(X509 *signcert, EVP_PKEY *pkey, STACK_OF(X509) *certs, BIO *data, int flags); |
| |
| =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). |
| |
| The data to be signed is read from BIO B<data>. |
| |
| B<flags> is an optional set of flags. |
| |
| =head1 NOTES |
| |
| 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. |
| |
| 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. |
| |
| 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. |
| |
| 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 |
| |
| 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. |
| |
| 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(). |
| |
| 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. |
| |
| 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. |
| |
| In OpenSSL 1.0.0 if B<signcert> and B<pkey> are NULL then a certificates only |
| PKCS#7 structure is output. |
| |
| In versions of OpenSSL before 1.0.0 the B<signcert> and B<pkey> parameters must |
| B<NOT> be NULL. |
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| =head1 BUGS |
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| Some advanced attributes such as counter signatures are not supported. |
| |
| =head1 RETURN VALUES |
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| 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 |
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| L<ERR_get_error(3)|ERR_get_error(3)>, L<PKCS7_verify(3)|PKCS7_verify(3)> |
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| =head1 HISTORY |
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| PKCS7_sign() was added to OpenSSL 0.9.5 |
| |
| 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 |
