1CMS_DECRYPT(3ossl) OpenSSL CMS_DECRYPT(3ossl)
2
6 CMS_decrypt, CMS_decrypt_set1_pkey_and_peer, CMS_decrypt_set1_pkey -
7 decrypt content from a CMS envelopedData structure
8
10 #include <openssl/cms.h>
11 int CMS_decrypt(CMS_ContentInfo *cms, EVP_PKEY *pkey, X509 *cert,
13 BIO *dcont, BIO *out, unsigned int flags);
14 int CMS_decrypt_set1_pkey_and_peer(CMS_ContentInfo *cms,
15 EVP_PKEY *pk, X509 *cert, X509 *peer);
16 int CMS_decrypt_set1_pkey(CMS_ContentInfo *cms, EVP_PKEY *pk, X509 *cert);
17
19 CMS_decrypt() extracts and decrypts the content from a CMS
20 EnvelopedData or AuthEnvelopedData structure. pkey is the private key
21 of the recipient, cert is the recipient's certificate, out is a BIO to
22 write the content to and flags is an optional set of flags.
23 The dcont parameter is used in the rare case where the encrypted
25 content is detached. It will normally be set to NULL.
26 CMS_decrypt_set1_pkey_and_peer() associates the private key pkey, the
28 corresponding certificate cert and the originator certificate peer with
29 the CMS_ContentInfo structure cms.
30 CMS_decrypt_set1_pkey() associates the private key pkey, corresponding
32 certificate cert with the CMS_ContentInfo structure cms.
33
35 Although the recipients certificate is not needed to decrypt the data
36 it is needed to locate the appropriate (of possible several) recipients
37 in the CMS structure.
38 If cert is set to NULL all possible recipients are tried. This case
40 however is problematic. To thwart the MMA attack (Bleichenbacher's
41 attack on PKCS #1 v1.5 RSA padding) all recipients are tried whether
42 they succeed or not. If no recipient succeeds then a random symmetric
43 key is used to decrypt the content: this will typically output garbage
44 and may (but is not guaranteed to) ultimately return a padding error
45 only. If CMS_decrypt() just returned an error when all recipient
46 encrypted keys failed to decrypt an attacker could use this in a timing
47 attack. If the special flag CMS_DEBUG_DECRYPT is set then the above
48 behaviour is modified and an error is returned if no recipient
49 encrypted key can be decrypted without generating a random content
50 encryption key. Applications should use this flag with extreme caution
51 especially in automated gateways as it can leave them open to attack.
52 It is possible to determine the correct recipient key by other means
54 (for example looking them up in a database) and setting them in the CMS
55 structure in advance using the CMS utility functions such as
56 CMS_set1_pkey(). In this case both cert and pkey should be set to NULL.
57 To process KEKRecipientInfo types CMS_set1_key() or
59 CMS_RecipientInfo_set0_key() and CMS_RecipientInfo_decrypt() should be
60 called before CMS_decrypt() and cert and pkey set to NULL.
61 The following flags can be passed in the flags parameter.
63 If the CMS_TEXT flag is set MIME headers for type text/plain are
65 deleted from the content. If the content is not of type text/plain then
66 an error is returned.
67
69 CMS_decrypt() returns either 1 for success or 0 for failure. The error
70 can be obtained from ERR_get_error(3)
71
73 The lack of single pass processing and the need to hold all data in
74 memory as mentioned in CMS_verify() also applies to CMS_decrypt().
75
77 ERR_get_error(3), CMS_encrypt(3)
78
80 CMS_decrypt_set1_pkey_and_peer was added in OpenSSL 3.0.
81
83 Copyright 2008-2020 The OpenSSL Project Authors. All Rights Reserved.
84 Licensed under the Apache License 2.0 (the "License"). You may not use
86 this file except in compliance with the License. You can obtain a copy
87 in the file LICENSE in the source distribution or at
88 <https://www.openssl.org/source/license.html>.
893.0.5 2022-07-05 CMS_DECRYPT(3ossl)