xref: /openssl/doc/man3/SMIME_read_CMS.pod (revision 0789c7d8)
1=pod
2
3=head1 NAME
4
5SMIME_read_CMS_ex, SMIME_read_CMS - parse S/MIME message
6
7=head1 SYNOPSIS
8
9 #include <openssl/cms.h>
10
11 CMS_ContentInfo *SMIME_read_CMS_ex(BIO *bio, int flags, BIO **bcont,
12                                    CMS_ContentInfo **cms);
13 CMS_ContentInfo *SMIME_read_CMS(BIO *in, BIO **bcont);
14
15=head1 DESCRIPTION
16
17SMIME_read_CMS() parses a message in S/MIME format.
18
19B<in> is a BIO to read the message from.
20
21If cleartext signing is used then the content is saved in a memory bio which is
22written to B<*bcont>, otherwise B<*bcont> is set to NULL.
23
24The parsed CMS_ContentInfo structure is returned or NULL if an
25error occurred.
26
27SMIME_read_CMS_ex() is similar to SMIME_read_CMS() but optionally a previously
28created I<cms> CMS_ContentInfo object can be supplied as well as some I<flags>.
29To create a I<cms> object use L<CMS_ContentInfo_new_ex(3)>.
30If the I<flags> argument contains B<CMS_BINARY> then the input is assumed to be
31in binary format and is not translated to canonical form.
32If in addition B<SMIME_ASCIICRLF> is set then the binary input is assumed
33to be followed by B<CR> and B<LF> characters, else only by an B<LF> character.
34If I<flags> is 0 and I<cms> is NULL then it is identical to SMIME_read_CMS().
35
36=head1 NOTES
37
38If B<*bcont> is not NULL then the message is clear text signed. B<*bcont> can
39then be passed to CMS_verify() with the B<CMS_DETACHED> flag set.
40
41Otherwise the type of the returned structure can be determined
42using CMS_get0_type().
43
44To support future functionality if B<bcont> is not NULL B<*bcont> should be
45initialized to NULL. For example:
46
47 BIO *cont = NULL;
48 CMS_ContentInfo *cms;
49
50 cms = SMIME_read_CMS(in, &cont);
51
52=head1 BUGS
53
54The MIME parser used by SMIME_read_CMS() is somewhat primitive.  While it will
55handle most S/MIME messages more complex compound formats may not work.
56
57The parser assumes that the CMS_ContentInfo structure is always base64 encoded
58and will not handle the case where it is in binary format or uses quoted
59printable format.
60
61The use of a memory BIO to hold the signed content limits the size of message
62which can be processed due to memory restraints: a streaming single pass option
63should be available.
64
65=head1 RETURN VALUES
66
67SMIME_read_CMS_ex() and SMIME_read_CMS() return a valid B<CMS_ContentInfo>
68structure or B<NULL> if an error occurred. The error can be obtained from
69ERR_get_error(3).
70
71=head1 SEE ALSO
72
73L<ERR_get_error(3)>,
74L<CMS_sign(3)>,
75L<CMS_verify(3)>,
76L<CMS_encrypt(3)>,
77L<CMS_decrypt(3)>
78
79=head1 HISTORY
80
81The function SMIME_read_CMS_ex() was added in OpenSSL 3.0.
82
83=head1 COPYRIGHT
84
85Copyright 2008-2021 The OpenSSL Project Authors. All Rights Reserved.
86
87Licensed under the Apache License 2.0 (the "License").  You may not use
88this file except in compliance with the License.  You can obtain a copy
89in the file LICENSE in the source distribution or at
90L<https://www.openssl.org/source/license.html>.
91
92=cut
93