/usr/include/pkcs9_asn1.h is in heimdal-dev 1.6~git20120311.dfsg.1-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/include/heimdal/pkcs9_asn1.h
/usr/include/heimdal/pkcs9_asn1.h