Initial Commit

openssl-1.0.2f/doc/crypto/CMS_encrypt.pod

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+=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
+
+L<ERR_get_error(3)|ERR_get_error(3)>, L<CMS_decrypt(3)|CMS_decrypt(3)>
+
+=head1 HISTORY
+
+CMS_decrypt() was added to OpenSSL 0.9.8
+The B<CMS_STREAM> flag was first supported in OpenSSL 1.0.0.
+
+=cut