Thanks to this popular benchmark database, the detailed specs of the upcoming Galaxy S8 flagships are now public. The processors used are Samsung's Exynos 8895 and the Snapdragon 835 chip by Qualcomm.
http://www.notebookcheck.net/Snapdragon-and-Exynos-powered-Galaxy-S8-flagships-hit-AnTuTu.209086.0.html