| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | CMS_compress - create a CMS CompressedData structure
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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | #include <openssl/cms.h>
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| 10 |
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| 11 | CMS_ContentInfo *CMS_compress(BIO *in, int comp_nid, unsigned int flags);
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| 12 |
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| 13 | =head1 DESCRIPTION
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| 14 |
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| 15 | CMS_compress() creates and returns a CMS CompressedData structure. B<comp_nid>
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| 16 | is the compression algorithm to use or B<NID_undef> to use the default
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| 17 | algorithm (zlib compression). B<in> is the content to be compressed.
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| 18 | B<flags> is an optional set of flags.
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| 19 |
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| 20 | =head1 NOTES
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| 21 |
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| 22 | The only currently supported compression algorithm is zlib using the NID
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| 23 | NID_zlib_compression.
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| 24 |
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| 25 | If zlib support is not compiled into OpenSSL then CMS_compress() will return
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| 26 | an error.
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| 27 |
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| 28 | If the B<CMS_TEXT> flag is set MIME headers for type B<text/plain> are
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| 29 | prepended to the data.
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| 30 |
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| 31 | Normally the supplied content is translated into MIME canonical format (as
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| 32 | required by the S/MIME specifications) if B<CMS_BINARY> is set no translation
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| 33 | occurs. This option should be used if the supplied data is in binary format
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| 34 | otherwise the translation will corrupt it. If B<CMS_BINARY> is set then
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| 35 | B<CMS_TEXT> is ignored.
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| 36 |
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| 37 | If the B<CMS_STREAM> flag is set a partial B<CMS_ContentInfo> structure is
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| 38 | returned suitable for streaming I/O: no data is read from the BIO B<in>.
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| 39 |
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| 40 | The compressed data is included in the CMS_ContentInfo structure, unless
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| 41 | B<CMS_DETACHED> is set in which case it is omitted. This is rarely used in
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| 42 | practice and is not supported by SMIME_write_CMS().
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| 43 |
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| 44 | =head1 NOTES
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| 45 |
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| 46 | If the flag B<CMS_STREAM> is set the returned B<CMS_ContentInfo> structure is
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| 47 | B<not> complete and outputting its contents via a function that does not
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| 48 | properly finalize the B<CMS_ContentInfo> structure will give unpredictable
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| 49 | results.
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| 50 |
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| 51 | Several functions including SMIME_write_CMS(), i2d_CMS_bio_stream(),
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| 52 | PEM_write_bio_CMS_stream() finalize the structure. Alternatively finalization
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| 53 | can be performed by obtaining the streaming ASN1 B<BIO> directly using
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| 54 | BIO_new_CMS().
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| 55 |
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| 56 | Additional compression parameters such as the zlib compression level cannot
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| 57 | currently be set.
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| 58 |
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| 59 | =head1 RETURN VALUES
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| 60 |
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| 61 | CMS_compress() returns either a CMS_ContentInfo structure or NULL if an error
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| 62 | occurred. The error can be obtained from ERR_get_error(3).
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| 63 |
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| 64 | =head1 SEE ALSO
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| 65 |
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| 66 | L<ERR_get_error(3)>, L<CMS_uncompress(3)>
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| 67 |
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| 68 | =head1 HISTORY
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| 69 |
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| 70 | The B<CMS_STREAM> flag was added in OpenSSL 1.0.0.
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| 71 |
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| 72 | =head1 COPYRIGHT
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| 73 |
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| 74 | Copyright 2008-2016 The OpenSSL Project Authors. All Rights Reserved.
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| 75 |
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| 76 | Licensed under the OpenSSL license (the "License"). You may not use
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| 77 | this file except in compliance with the License. You can obtain a copy
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| 78 | in the file LICENSE in the source distribution or at
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| 79 | L<https://www.openssl.org/source/license.html>.
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| 80 |
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| 81 | =cut
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