=pod
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=head1 NAME
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BIO_new_CMS - CMS streaming filter BIO
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=head1 SYNOPSIS
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#include <openssl/cms.h>
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BIO *BIO_new_CMS(BIO *out, CMS_ContentInfo *cms);
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=head1 DESCRIPTION
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BIO_new_CMS() returns a streaming filter BIO chain based on B<cms>. The output
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of the filter is written to B<out>. Any data written to the chain is
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automatically translated to a BER format CMS structure of the appropriate type.
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=head1 NOTES
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The chain returned by this function behaves like a standard filter BIO. It
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supports non blocking I/O. Content is processed and streamed on the fly and not
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all held in memory at once: so it is possible to encode very large structures.
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After all content has been written through the chain BIO_flush() must be called
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to finalise the structure.
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The B<CMS_STREAM> flag must be included in the corresponding B<flags>
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parameter of the B<cms> creation function.
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If an application wishes to write additional data to B<out> BIOs should be
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removed from the chain using BIO_pop() and freed with BIO_free() until B<out>
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is reached. If no additional data needs to be written BIO_free_all() can be
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called to free up the whole chain.
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Any content written through the filter is used verbatim: no canonical
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translation is performed.
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It is possible to chain multiple BIOs to, for example, create a triple wrapped
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signed, enveloped, signed structure. In this case it is the applications
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responsibility to set the inner content type of any outer CMS_ContentInfo
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structures.
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Large numbers of small writes through the chain should be avoided as this will
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produce an output consisting of lots of OCTET STRING structures. Prepending
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a BIO_f_buffer() buffering BIO will prevent this.
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=head1 BUGS
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There is currently no corresponding inverse BIO: i.e. one which can decode
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a CMS structure on the fly.
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=head1 RETURN VALUES
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BIO_new_CMS() returns a BIO chain when successful or NULL if an error
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occurred. The error can be obtained from ERR_get_error(3).
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=head1 SEE ALSO
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L<ERR_get_error(3)|ERR_get_error(3)>, L<CMS_sign(3)|CMS_sign(3)>,
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L<CMS_encrypt(3)|CMS_encrypt(3)>
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=head1 HISTORY
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BIO_new_CMS() was added to OpenSSL 1.0.0
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=cut
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