| =pod |
| |
| =head1 NAME |
| |
| CMS_encrypt - create a CMS envelopedData structure |
| |
| =head1 SYNOPSIS |
| |
| #include <openssl/cms.h> |
| |
| CMS_ContentInfo *CMS_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, unsigned int flags); |
| |
| =head1 DESCRIPTION |
| |
| CMS_encrypt() creates and returns a CMS EnvelopedData structure. B<certs> |
| is a list of recipient certificates. B<in> is the content to be encrypted. |
| B<cipher> is the symmetric cipher to use. B<flags> is an optional set of flags. |
| |
| =head1 NOTES |
| |
| Only certificates carrying RSA keys are supported so the recipient certificates |
| supplied to this function must all contain RSA public keys, though they do not |
| have to be signed using the RSA algorithm. |
| |
| EVP_des_ede3_cbc() (triple DES) is the algorithm of choice for S/MIME use |
| because most clients will support it. |
| |
| The algorithm passed in the B<cipher> parameter must support ASN1 encoding of |
| its parameters. |
| |
| Many browsers implement a "sign and encrypt" option which is simply an S/MIME |
| envelopedData containing an S/MIME signed message. This can be readily produced |
| by storing the S/MIME signed message in a memory BIO and passing it to |
| CMS_encrypt(). |
| |
| The following flags can be passed in the B<flags> parameter. |
| |
| If the B<CMS_TEXT> flag is set MIME headers for type B<text/plain> are |
| prepended to the data. |
| |
| Normally the supplied content is translated into MIME canonical format (as |
| required by the S/MIME specifications) if B<CMS_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. If B<CMS_BINARY> is set then |
| B<CMS_TEXT> is ignored. |
| |
| OpenSSL will by default identify recipient certificates using issuer name |
| and serial number. If B<CMS_USE_KEYID> is set it will use the subject key |
| identifier value instead. An error occurs if all recipient certificates do not |
| have a subject key identifier extension. |
| |
| If the B<CMS_STREAM> flag is set a partial B<CMS_ContentInfo> structure is |
| returned suitable for streaming I/O: no data is read from the BIO B<in>. |
| |
| If the B<CMS_PARTIAL> flag is set a partial B<CMS_ContentInfo> structure is |
| returned to which additional recipients and attributes can be added before |
| finalization. |
| |
| The data being encrypted is included in the CMS_ContentInfo structure, unless |
| B<CMS_DETACHED> is set in which case it is omitted. This is rarely used in |
| practice and is not supported by SMIME_write_CMS(). |
| |
| =head1 NOTES |
| |
| If the flag B<CMS_STREAM> is set the returned B<CMS_ContentInfo> structure is |
| B<not> complete and outputting its contents via a function that does not |
| properly finalize the B<CMS_ContentInfo> structure will give unpredictable |
| results. |
| |
| Several functions including SMIME_write_CMS(), i2d_CMS_bio_stream(), |
| PEM_write_bio_CMS_stream() finalize the structure. Alternatively finalization |
| can be performed by obtaining the streaming ASN1 B<BIO> directly using |
| BIO_new_CMS(). |
| |
| The recipients specified in B<certs> use a CMS KeyTransRecipientInfo info |
| structure. KEKRecipientInfo is also supported using the flag B<CMS_PARTIAL> |
| and CMS_add0_recipient_key(). |
| |
| The parameter B<certs> may be NULL if B<CMS_PARTIAL> is set and recipients |
| added later using CMS_add1_recipient_cert() or CMS_add0_recipient_key(). |
| |
| =head1 RETURN VALUES |
| |
| CMS_encrypt() returns either a CMS_ContentInfo 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)>, L<CMS_decrypt(3)> |
| |
| =head1 HISTORY |
| |
| The B<CMS_STREAM> flag was first supported in OpenSSL 1.0.0. |
| |
| =cut |
