According to Section 377 of the Indian Penal Code 1860,
Unnatural offences — Whoever voluntarily has carnal intercourse against the order of nature with any man, woman or animal, shall be punished with imprisonment for life, or with imprisonment of either description for a term which may extend to ten years, and shall also be liable to fine.
Explanation — Penetration is sufficient to constitute the carnal intercourse necessary to the offence described in this section.