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