Safe for your camera, yes; safe for your eyes, maybe not. Whether you cite NASA, the American Astronomical Society or whoever -- they all rely on the international safety standard ISO12312-2 (2015). That standard specifies a range of 14.9 to 20.6 stops for safe viewing of the sun. However, the ISO standard emphasizes the need to protect the eyes from nonvisible radiation (UV and IR) as well as visible light. If you are using Neutral Density filters, be aware that they are designed to filter light in the visible range and are much less effective on UV and IR (eg, about 2 -4 stops). In short, your camera will be OK, but you will be OK only if you use Live View or digital viewfinder -- if you use an analog viewfinder typical in most DSLRs, you could do serious damage to your eyes. If you use white light filters, as those designed for viewing the sun, no problem.

Also, contrary to what many have read here and elsewhere, welder's glasses are not a good choice for the same reason. They are designed to filter radiation from an arc welding torch which generates a very different light spectrum than the sun -- much lower in UV and IR radiation. Welders glasses therefore are explicitly classified under ISO as "inappropriate for solar viewers".