It was a bit different than you say but not too far off: https://en.m.wikipedia.org/wiki/Budapest_Memorandum

In a nutshell, among several more countries Russia and Ukraine signed this agreement, Ukraine and other countries pledged to get rid of sovjet nukes, in return Russia and other countries pledged to not excert force against the countries that signed, except for self defense. And well, we know now how that went.