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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
38d3a738 | 5 | CMS_encrypt - create a CMS envelopedData structure |
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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 | ||
38d3a738 | 15 | CMS_encrypt() creates and returns a CMS EnvelopedData structure. B<certs> |
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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 | ||
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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. | |
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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 | ||
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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 | ||
9034c56c | 70 | Several functions including SMIME_write_CMS(), i2d_CMS_bio_stream(), |
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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 | ||
c420fab5 | 75 | The recipients specified in B<certs> use a CMS KeyTransRecipientInfo info |
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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 | |
fb552ac6 | 94 | The B<CMS_STREAM> flag was first supported in OpenSSL 1.0.0. |
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95 | |
96 | =cut |