This is functional but is merely a workaround until we get vsis3 - you can try out preliminary vsis3 support with GDAL 2.1 and rasterio 0.32a1
Goal: Based on the GeoTiff and TIFF specs, manually parse out tags to allow for the most IO-efficient reading of georeferencing information.
It works almost the same as rio info --bounds
but gives a json array, and it's fast
$ time rio info --bounds R4C1.tif
153.984375 24.2578125 154.072265625 24.345703125