1=pod
2
3=head1 NAME
4
5PKCS7_encrypt - create a PKCS#7 envelopedData structure
6
7=head1 SYNOPSIS
8
9 #include <openssl/pkcs7.h>
10
11 PKCS7 *PKCS7_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, int flags);
12
13=head1 DESCRIPTION
14
15PKCS7_encrypt() creates and returns a PKCS#7 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 RSA keys are supported in PKCS#7 and envelopedData so the recipient
22certificates supplied to this function must all contain RSA public keys, though
23they do not have 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
28Some old "export grade" clients may only support weak encryption using 40 or 64
29bit RC2. These can be used by passing EVP_rc2_40_cbc() and EVP_rc2_64_cbc()
30respectively.
31
32The algorithm passed in the B<cipher> parameter must support ASN1 encoding of
33its parameters.
34
35Many browsers implement a "sign and encrypt" option which is simply an S/MIME
36envelopedData containing an S/MIME signed message. This can be readily produced
37by storing the S/MIME signed message in a memory BIO and passing it to
38PKCS7_encrypt().
39
40The following flags can be passed in the B<flags> parameter.
41
42If the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are
43prepended to the data.
44
45Normally the supplied content is translated into MIME canonical format (as
46required by the S/MIME specifications) if B<PKCS7_BINARY> is set no translation
47occurs. This option should be used if the supplied data is in binary format
48otherwise the translation will corrupt it. If B<PKCS7_BINARY> is set then
49B<PKCS7_TEXT> is ignored.
50
51If the B<PKCS7_STREAM> flag is set a partial B<PKCS7> structure is output
52suitable for streaming I/O: no data is read from the BIO B<in>.
53
54=head1 NOTES
55
56If the flag B<PKCS7_STREAM> is set the returned B<PKCS7> structure is B<not>
57complete and outputting its contents via a function that does not
58properly finalize the B<PKCS7> structure will give unpredictable
59results.
60
61Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(),
62PEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization
63can be performed by obtaining the streaming ASN1 B<BIO> directly using
64BIO_new_PKCS7().
65
66=head1 RETURN VALUES
67
68PKCS7_encrypt() returns either a PKCS7 structure or NULL if an error occurred.
69The error can be obtained from ERR_get_error(3).
70
71=head1 SEE ALSO
72
73L<ERR_get_error(3)|ERR_get_error(3)>, L<PKCS7_decrypt(3)|PKCS7_decrypt(3)>
74
75=head1 HISTORY
76
77PKCS7_decrypt() was added to OpenSSL 0.9.5
78The B<PKCS7_STREAM> flag was first supported in OpenSSL 1.0.0.
79
80=cut
81