net/http: invalid RAR sniff signature from the MIME Sniff spec

[odeke-em]

I am coming here from CL https://go-review.googlesource.com/c/go/+/167781 created by @cuonglm's vigilance.

In particular it uses a wrong character for the 4th byte i.e.
0x20 " " for both RAR v5 and RAR v4 instead of 0x21 "!"

as per

go/src/net/http/sniff.go

Lines 188 to 189 in faa7fa0

	&exactSig{[]byte("Rar \x1A\x07\x00"), "application/x-rar-compressed"}, // RAR v1.5-v4.0
	&exactSig{[]byte("Rar \x1A\x07\x01\x00"), "application/x-rar-compressed"}, // RAR v5+

The sniff signature that we got from the MIME sniff spec is wrong and that's acknowledged at
whatwg/mimesniff#63
but also the official RAR Labs website shows the correct signature as
https://www.rarlab.com/technote.htm#rarsign

[gopherbot]

Change https://golang.org/cl/167781 mentions this issue: net/http: fix wrong mime rar signature