In cases in which contracts for the sale or lease of lands owned by the state have been duly signed, executed and delivered to the purchaser or purchasers or lessees named in such contracts, by the proper state officers, the omission on the part of the proper officers to have first offered such lands at public sale shall not invalidate the private sales or leasing of such lands; but the purchaser or purchasers or lessees in such contracts mentioned, or their assignees, upon performance by them of the covenants and conditions on their part, by the terms of such contracts to be done, kept and performed, shall be entitled to a deed or contract of sale from the state for such lands; and the proper officers of the state in such cases are authorized and directed to make, execute and deliver to such purchaser or purchasers or lessees, or their assignees, deeds or contracts of sale from the state, which deeds, when properly executed and delivered, shall convey all right, title and interest of the state in and to the lands described therein.