SMIME_write_CMS man page

SMIME_write_CMS — convert CMS structure to S/MIME format.


#include <openssl/cms.h>
int SMIME_write_CMS(BIO *out, CMS_ContentInfo *cms, BIO *data, int flags);


SMIME_write_CMS() adds the appropriate MIME headers to a CMS structure to produce an S/MIME message.

out is the BIO to write the data to. cms is the appropriate CMS_ContentInfo structure. If streaming is enabled then the content must be supplied in the data argument. flags is an optional set of flags.


The following flags can be passed in the flags parameter.

If CMS_DETACHED is set then cleartext signing will be used, this option only makes sense for SignedData where CMS_DETACHED is also set when CMS_sign() is called.

If the CMS_TEXT flag is set MIME headers for type text/plain are added to the content, this only makes sense if CMS_DETACHED is also set.

If the CMS_STREAM flag is set streaming is performed. This flag should only be set if CMS_STREAM was also set in the previous call to a CMS_ContentInfo creation function.

If cleartext signing is being used and CMS_STREAM not set then the data must be read twice: once to compute the signature in CMS_sign() and once to output the S/MIME message.

If streaming is performed the content is output in BER format using indefinite length constructed encoding except in the case of signed data with detached content where the content is absent and DER format is used.


SMIME_write_CMS() always base64 encodes CMS structures, there should be an option to disable this.

Return Values

SMIME_write_CMS() returns 1 for success or 0 for failure.

See Also

ERR_get_error(3), CMS_sign(3), CMS_verify(3), CMS_encrypt(3) CMS_decrypt(3)


SMIME_write_CMS() was added to OpenSSL 0.9.8

Referenced By

i2d_CMS_bio_stream(3), i2d_CMS_bio_stream.3ssl(3), PEM_write_bio_CMS_stream(3), PEM_write_bio_CMS_stream.3ssl(3).

Explore man page connections for SMIME_write_CMS(3).

OpenSSL 1.0.2j 2016-09-26