Cabinet makes a law to increase salary of President, Vice president, MP’s etc. But who passes it? President of India. So President himself/herself passes his/her salary hike.

Last hike was done by then President Pratibha Patil giving her a 300 per cent hike in salary taking her monthly pay cheque to Rs 1.5 lakh from Rs 50,000 per month.

source: http://archive.indianexpress.com/news/president-okays-her-own-salary-hike-by-300-per-cent/406240/