SMIME_READ_CMS(3)

NAME
SMIME_read_CMS - extract CMS ContentInfo from an S/MIME message

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

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

If the message uses cleartext signing, the content is saved in a memory BIO which is written to *bcont and which can then be passed to CMS_verify(3) with the CMS_DETACHED flag set. Otherwise, *bcont is set to NULL and the type of the returned structure can be determined using CMS_get0_type(3).

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

    BIO *cont = NULL;
    CMS_ContentInfo *cms = SMIME_read_CMS(in, &cont);

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
CMS_ContentInfo_new(3), CMS_decrypt(3), CMS_get0_type(3), CMS_verify(3), d2i_CMS_ContentInfo(3), SMIME_read_ASN1(3), SMIME_write_CMS(3)

HISTORY
SMIME_read_CMS() first appeared in OpenSSL 0.9.8h and has been available since OpenBSD 6.7.

BUGS
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 the message which can be processed due to memory restraints: a streaming single pass option should be available.