1=pod 2 3=head1 NAME 4 5CMS_encrypt_ex, CMS_encrypt - create a CMS envelopedData structure 6 7=head1 SYNOPSIS 8 9 #include <openssl/cms.h> 10 11 CMS_ContentInfo *CMS_encrypt_ex(STACK_OF(X509) *certs, BIO *in, 12 const EVP_CIPHER *cipher, unsigned int flags, 13 OSSL_LIB_CTX *libctx, const char *propq); 14 CMS_ContentInfo *CMS_encrypt(STACK_OF(X509) *certs, BIO *in, 15 const EVP_CIPHER *cipher, unsigned int flags); 16 17=head1 DESCRIPTION 18 19CMS_encrypt_ex() creates and returns a CMS EnvelopedData or 20AuthEnvelopedData structure. I<certs> is a list of recipient certificates. 21I<in> is the content to be encrypted. I<cipher> is the symmetric cipher to use. 22I<flags> is an optional set of flags. The library context I<libctx> and the 23property query I<propq> are used internally when retrieving algorithms from 24providers. 25 26Only certificates carrying RSA, Diffie-Hellman or EC keys are supported by this 27function. 28 29EVP_des_ede3_cbc() (triple DES) is the algorithm of choice for S/MIME use 30because most clients will support it. 31 32The algorithm passed in the B<cipher> parameter must support ASN1 encoding of 33its parameters. If the cipher mode is GCM, then an AuthEnvelopedData structure 34containing MAC is used. Otherwise an EnvelopedData structure is used. Currently 35the AES variants with GCM mode are the only supported AEAD algorithms. 36 37Many browsers implement a "sign and encrypt" option which is simply an S/MIME 38envelopedData containing an S/MIME signed message. This can be readily produced 39by storing the S/MIME signed message in a memory BIO and passing it to 40CMS_encrypt(). 41 42The following flags can be passed in the B<flags> parameter. 43 44If the B<CMS_TEXT> flag is set MIME headers for type B<text/plain> are 45prepended to the data. 46 47Normally the supplied content is translated into MIME canonical format (as 48required by the S/MIME specifications) if B<CMS_BINARY> is set no translation 49occurs. This option should be used if the supplied data is in binary format 50otherwise the translation will corrupt it. If B<CMS_BINARY> is set then 51B<CMS_TEXT> is ignored. 52 53OpenSSL will by default identify recipient certificates using issuer name 54and serial number. If B<CMS_USE_KEYID> is set it will use the subject key 55identifier value instead. An error occurs if all recipient certificates do not 56have a subject key identifier extension. 57 58If the B<CMS_STREAM> flag is set a partial B<CMS_ContentInfo> structure is 59returned suitable for streaming I/O: no data is read from the BIO B<in>. 60 61If the B<CMS_PARTIAL> flag is set a partial B<CMS_ContentInfo> structure is 62returned to which additional recipients and attributes can be added before 63finalization. 64 65The data being encrypted is included in the CMS_ContentInfo structure, unless 66B<CMS_DETACHED> is set in which case it is omitted. This is rarely used in 67practice and is not supported by SMIME_write_CMS(). 68 69If the flag B<CMS_STREAM> is set the returned B<CMS_ContentInfo> structure is 70B<not> complete and outputting its contents via a function that does not 71properly finalize the B<CMS_ContentInfo> structure will give unpredictable 72results. 73 74Several functions including SMIME_write_CMS(), i2d_CMS_bio_stream(), 75PEM_write_bio_CMS_stream() finalize the structure. Alternatively finalization 76can be performed by obtaining the streaming ASN1 B<BIO> directly using 77BIO_new_CMS(). 78 79The recipients specified in B<certs> use a CMS KeyTransRecipientInfo info 80structure. KEKRecipientInfo is also supported using the flag B<CMS_PARTIAL> 81and CMS_add0_recipient_key(). 82 83The parameter B<certs> may be NULL if B<CMS_PARTIAL> is set and recipients 84added later using CMS_add1_recipient_cert() or CMS_add0_recipient_key(). 85 86CMS_encrypt() is similar to CMS_encrypt_ex() but uses default values 87of NULL for the library context I<libctx> and the property query I<propq>. 88 89=head1 RETURN VALUES 90 91CMS_encrypt_ex() and CMS_encrypt() return either a CMS_ContentInfo 92structure or NULL if an error occurred. The error can be obtained from 93ERR_get_error(3). 94 95=head1 SEE ALSO 96 97L<ERR_get_error(3)>, L<CMS_decrypt(3)> 98 99=head1 HISTORY 100 101The function CMS_encrypt_ex() was added in OpenSSL 3.0. 102 103The B<CMS_STREAM> flag was first supported in OpenSSL 1.0.0. 104 105=head1 COPYRIGHT 106 107Copyright 2008-2020 The OpenSSL Project Authors. All Rights Reserved. 108 109Licensed under the Apache License 2.0 (the "License"). You may not use 110this file except in compliance with the License. You can obtain a copy 111in the file LICENSE in the source distribution or at 112L<https://www.openssl.org/source/license.html>. 113 114=cut 115