5 CMS_encrypt - create a CMS envelopedData structure
9 #include <openssl/cms.h>
11 CMS_ContentInfo *CMS_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, unsigned int flags);
15 CMS_encrypt() creates and returns a CMS envelopedData structure. B<certs>
16 is a list of recipient certificates. B<in> is the content to be encrypted.
17 B<cipher> is the symmetric cipher to use. B<flags> is an optional set of flags.
21 Only certificates carrying RSA keys are supported in CMS and envelopedData so
22 the recipient certificates supplied to this function must all contain RSA
23 public keys, though they do not have to be signed using the RSA algorithm.
25 EVP_des_ede3_cbc() (triple DES) is the algorithm of choice for S/MIME use
26 because most clients will support it.
28 Some old "export grade" clients may only support weak encryption using 40 or 64
29 bit RC2. These can be used by passing EVP_rc2_40_cbc() and EVP_rc2_64_cbc()
32 The algorithm passed in the B<cipher> parameter must support ASN1 encoding of
35 Many browsers implement a "sign and encrypt" option which is simply an S/MIME
36 envelopedData containing an S/MIME signed message. This can be readily produced
37 by storing the S/MIME signed message in a memory BIO and passing it to
40 The following flags can be passed in the B<flags> parameter.
42 If the B<CMS_TEXT> flag is set MIME headers for type B<text/plain> are
43 prepended to the data.
45 Normally the supplied content is translated into MIME canonical format (as
46 required by the S/MIME specifications) if B<CMS_BINARY> is set no translation
47 occurs. This option should be used if the supplied data is in binary format
48 otherwise the translation will corrupt it. If B<CMS_BINARY> is set then
49 B<CMS_TEXT> is ignored.
51 OpenSSL will by default identify recipient certificates using issuer name
52 and serial number. If B<CMS_USE_KEYID> is set it will use the subject key
53 identifier value instead. An error occurs if all recipient certificates do not
54 have a subject key identifier extension.
56 If the B<CMS_STREAM> flag is set a partial B<CMS_ContentInfo> structure is
57 returned suitable for streaming I/O: no data is read from the BIO B<in>.
59 If the B<CMS_PARTIAL> flag is set a partial B<CMS_ContentInfo> structure is
60 returned to which additional recipients and attributes can be added before
63 The data being encrypted is included in the CMS_ContentInfo structure, unless
64 B<CMS_DETACHED> is set in which case it is omitted. This is rarely used in
65 practice and is not supported by SMIME_write_CMS().
69 If the flag B<CMS_STREAM> is set the returned B<CMS_ContentInfo> structure is
70 B<not> complete and outputting its contents via a function that does not
71 properly finalize the B<CMS_ContentInfo> structure will give unpredictable
74 Several functions including SMIME_write_CMS(), i2d_CMS_bio_stream(),
75 PEM_write_bio_CMS_stream() finalize the structure. Alternatively finalization
76 can be performed by obtaining the streaming ASN1 B<BIO> directly using
79 The recipients specified in B<certs> use a CMS KeyTransRecipientInfo info
80 structure. KEKRecipientInfo is also supported using the flag B<CMS_PARTIAL>
81 and CMS_add0_recipient_key().
83 The parameter B<certs> may be NULL if B<CMS_PARTIAL> is set and recipients
84 added later using CMS_add1_recipient_cert() or CMS_add0_recipient_key().
88 CMS_encrypt() returns either a CMS_ContentInfo structure or NULL if an error
89 occurred. The error can be obtained from ERR_get_error(3).
93 L<ERR_get_error(3)|ERR_get_error(3)>, L<CMS_decrypt(3)|CMS_decrypt(3)>
97 CMS_decrypt() was added to OpenSSL 0.9.8
98 The B<CMS_STREAM> flag was first supported in OpenSSL 0.9.9.