SMIME_read_CMS.3ssl man page

SMIME_read_CMS — parse S/MIME message


#include <openssl/cms.h>
CMS_ContentInfo *SMIME_read_CMS(BIO *in, BIO **bcont);


SMIME_read_CMS() parses a message in S/MIME format.

in is a BIO to read the message from.

If cleartext signing is used then the content is saved in a memory bio which is written to *bcont, otherwise *bcont is set to NULL.

The parsed CMS_ContentInfo structure is returned or NULL if an error occurred.


If *bcont is not NULL then the message is clear text signed. *bcont can then be passed to CMS_verify() with the CMS_DETACHED flag set.

Otherwise the type of the returned structure can be determined using CMS_get0_type().

To support future functionality if bcont is not NULL *bcont should be initialized to NULL. For example:

BIO *cont = NULL;
CMS_ContentInfo *cms;

cms = SMIME_read_CMS(in, &cont);


The MIME parser used by SMIME_read_CMS() is somewhat primitive. While it will handle most S/MIME messages more complex compound formats may not work.

The parser assumes that the CMS_ContentInfo structure is always base64 encoded and will not handle the case where it is in binary format or uses quoted printable format.

The use of a memory BIO to hold the signed content limits the size of message which can be processed due to memory restraints: a streaming single pass option should be available.

Return Values

SMIME_read_CMS() returns a valid CMS_ContentInfo structure or NULL if an error occurred. The error can be obtained from ERR_get_error(3).

See Also

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