BIO_NEW_CMS(3) BSD Library Functions Manual BIO_NEW_CMS(3)NAMEBIO_new_CMS — CMS streaming filter BIO
SYNOPSIS
#include <openssl/cms.h>
BIO *
BIO_new_CMS(BIO *out, CMS_ContentInfo *cms);
DESCRIPTIONBIO_new_CMS() returns a streaming filter BIO chain based on cms. The
output of the filter is written to out. Any data written to the chain is
automatically translated to a BER format CMS structure of the appropriate
type.
RETURN VALUESBIO_new_CMS() returns a BIO chain when successful or NULL if an error
occurred. The error can be obtained from ERR_get_error(3).
NOTES
The chain returned by this function behaves like a standard filter BIO.
It supports non blocking I/O. Content is processed and streamed on the
fly and not all held in memory at once: so it is possible to encode very
large structures. After all content has been written through the chain
BIO_flush(3) must be called to finalise the structure.
The CMS_STREAM flag must be included in the corresponding flags parameter
of the cms creation function.
If an application wishes to write additional data to out, BIOs should be
removed from the chain using BIO_pop(3) and freed with BIO_free(3) until
out is reached. If no additional data needs to be written,
BIO_free_all(3) can be called to free up the whole chain.
Any content written through the filter is used verbatim: no canonical
translation is performed.
It is possible to chain multiple BIOs to, for example, create a triple
wrapped signed, enveloped, signed structure. In this case it is the
application's responsibility to set the inner content type of any outer
CMS_ContentInfo structures.
Large numbers of small writes through the chain should be avoided as this
will produce an output consisting of lots of OCTET STRING structures.
Prepending a BIO_f_buffer(3) buffering BIO will prevent this.
SEE ALSOCMS_encrypt(3), CMS_sign(3), ERR_get_error(3)HISTORYBIO_new_CMS() was added to OpenSSL 1.0.0.
BUGS
There is currently no corresponding inverse BIO which can decode a CMS
structure on the fly.
BSD October 2, 2010 BSD
