BIO_new_CMS (3)

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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 chain based on cms. The output of the filter is written to out. Any data written to the chain is automatically translated to a format structure of the appropriate type.

NOTES

The chain returned by this function behaves like a standard filter 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

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

structures. Prepending a BIO_f_buffer() buffering will prevent this.

BUGS

There is currently no corresponding inverse i.e. one which can decode a structure on the fly.

RETURN VALUES

BIO_new_CMS() returns a chain when successful or 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