1=pod
2
3=head1 NAME
4
5 CMS_encrypt - create a CMS envelopedData structure
6
7=head1 SYNOPSIS
8
9 #include <openssl/cms.h>
10
11 CMS_ContentInfo *CMS_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, unsigned int flags);
12
13=head1 DESCRIPTION
14
15CMS_encrypt() creates and returns a CMS EnvelopedData structure. B<certs>
16is a list of recipient certificates. B<in> is the content to be encrypted.
17B<cipher> is the symmetric cipher to use. B<flags> is an optional set of flags.
18
19=head1 NOTES
20
21Only certificates carrying RSA keys are supported so the recipient certificates
22supplied to this function must all contain RSA public keys, though they do not
23have to be signed using the RSA algorithm.
24
25EVP_des_ede3_cbc() (triple DES) is the algorithm of choice for S/MIME use
26because most clients will support it.
27
28The algorithm passed in the B<cipher> parameter must support ASN1 encoding of
29its parameters.
30
31Many browsers implement a "sign and encrypt" option which is simply an S/MIME
32envelopedData containing an S/MIME signed message. This can be readily produced
33by storing the S/MIME signed message in a memory BIO and passing it to
34CMS_encrypt().
35
36The following flags can be passed in the B<flags> parameter.
37
38If the B<CMS_TEXT> flag is set MIME headers for type B<text/plain> are
39prepended to the data.
40
41Normally the supplied content is translated into MIME canonical format (as
42required by the S/MIME specifications) if B<CMS_BINARY> is set no translation
43occurs. This option should be used if the supplied data is in binary format
44otherwise the translation will corrupt it. If B<CMS_BINARY> is set then
45B<CMS_TEXT> is ignored.
46
47OpenSSL will by default identify recipient certificates using issuer name
48and serial number. If B<CMS_USE_KEYID> is set it will use the subject key
49identifier value instead. An error occurs if all recipient certificates do not
50have a subject key identifier extension.
51
52If the B<CMS_STREAM> flag is set a partial B<CMS_ContentInfo> structure is
53returned suitable for streaming I/O: no data is read from the BIO B<in>.
54
55If the B<CMS_PARTIAL> flag is set a partial B<CMS_ContentInfo> structure is
56returned to which additional recipients and attributes can be added before
57finalization.
58
59The data being encrypted is included in the CMS_ContentInfo structure, unless
60B<CMS_DETACHED> is set in which case it is omitted. This is rarely used in
61practice and is not supported by SMIME_write_CMS().
62
63=head1 NOTES
64
65If the flag B<CMS_STREAM> is set the returned B<CMS_ContentInfo> structure is
66B<not> complete and outputting its contents via a function that does not
67properly finalize the B<CMS_ContentInfo> structure will give unpredictable
68results.
69
70Several functions including SMIME_write_CMS(), i2d_CMS_bio_stream(),
71PEM_write_bio_CMS_stream() finalize the structure. Alternatively finalization
72can be performed by obtaining the streaming ASN1 B<BIO> directly using
73BIO_new_CMS().
74
75The recipients specified in B<certs> use a CMS KeyTransRecipientInfo info
76structure. KEKRecipientInfo is also supported using the flag B<CMS_PARTIAL>
77and CMS_add0_recipient_key().
78
79The parameter B<certs> may be NULL if B<CMS_PARTIAL> is set and recipients
80added later using CMS_add1_recipient_cert() or CMS_add0_recipient_key().
81
82=head1 RETURN VALUES
83
84CMS_encrypt() returns either a CMS_ContentInfo structure or NULL if an error
85occurred. The error can be obtained from ERR_get_error(3).
86
87=head1 SEE ALSO
88
89L<ERR_get_error(3)|ERR_get_error(3)>, L<CMS_decrypt(3)|CMS_decrypt(3)>
90
91=head1 HISTORY
92
93CMS_decrypt() was added to OpenSSL 0.9.8
94The B<CMS_STREAM> flag was first supported in OpenSSL 1.0.0.
95
96=cut
97