Did you sign a bond before leaving for your on-site assignment? What is the separation policy of your firm? If you default on the parameters mentioned, you will be blacklisted. However, if you abide by the rules, you have little or no reason to worry.
There is another area you should consider before you resign, which is communication with your existing reporting leaders. Please consider this beyond the organizational realms. You may not violate policy but could still damage your relationship with them. Please handle this very sensitively as they have been guiding you thus far. In the future, you might cross paths with them. Please maintain your values intact, no matter how challenging your situation becomes.
Looking forward to hearing from you.