NAME¶
BIO_new_CMS - CMS streaming filter BIO
SYNOPSIS¶
#include <openssl/cms.h>
BIO *BIO_new_CMS(BIO *out, CMS_ContentInfo *cms);
DESCRIPTION¶
BIO_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.
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() 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() and freed with
BIO_free()
until
out is reached. If no additional data needs to be written
BIO_free_all() 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 applications
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() buffering BIO will prevent this.
BUGS¶
There is currently no corresponding inverse BIO: i.e. one which can decode a CMS
structure on the fly.
RETURN VALUES¶
BIO_new_CMS() returns a BIO chain when successful or NULL if an error
occurred. The error can be obtained from
ERR_get_error(3).
SEE ALSO¶
ERR_get_error(3),
CMS_sign(3),
CMS_encrypt(3)
HISTORY¶
BIO_new_CMS() was added to OpenSSL 1.0.0