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Diffstat (limited to 'openssl/doc/crypto/PKCS7_sign.pod')
| -rw-r--r-- | openssl/doc/crypto/PKCS7_sign.pod | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/openssl/doc/crypto/PKCS7_sign.pod b/openssl/doc/crypto/PKCS7_sign.pod new file mode 100644 index 000000000..ffd0c734b --- /dev/null +++ b/openssl/doc/crypto/PKCS7_sign.pod @@ -0,0 +1,101 @@ +=pod + +=head1 NAME + +PKCS7_sign - create a PKCS#7 signedData structure + +=head1 SYNOPSIS + +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_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. + +=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. + +At present only the SMIME_write_PKCS7() function properly finalizes the +structure. + +=head1 BUGS + +PKCS7_sign() is somewhat limited. It does not support multiple signers, some +advanced attributes such as counter signatures are not supported. + +The SHA1 digest algorithm is currently always used. + +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. + + +=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). + +=head1 SEE ALSO + +L<ERR_get_error(3)|ERR_get_error(3)>, L<PKCS7_verify(3)|PKCS7_verify(3)> + +=head1 HISTORY + +PKCS7_sign() was added to OpenSSL 0.9.5 + +The B<PKCS7_PARTSIGN> flag was added in OpenSSL 0.9.8 + +=cut |