net/http: Detect MIME type of v5 RAR archives

Change-Id: Id9dedc861523e2dafe0e67f70862973124fa07b3
GitHub-Last-Rev: b662561f1980dff9861dd8a738c75a03baa72681
GitHub-Pull-Request: golang/go#30909
Reviewed-on: https://go-review.googlesource.com/c/go/+/168039Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/http/sniff.go

@@ -185,7 +185,8 @@ var sniffSignatures = []sniffSig{
 	// Archive types
 	&exactSig{[]byte("\x1F\x8B\x08"), "application/x-gzip"},
 	&exactSig{[]byte("PK\x03\x04"), "application/zip"},
-	&exactSig{[]byte("Rar \x1A\x07\x00"), "application/x-rar-compressed"},
+	&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+
 
 	&exactSig{[]byte("\x00\x61\x73\x6D"), "application/wasm"},
 

src/net/http/sniff_test.go

@@ -72,6 +72,10 @@ var sniffTests = []struct {
 	{"woff sample  I", []byte("\x77\x4f\x46\x46\x00\x01\x00\x00\x00\x00\x30\x54\x00\x0d\x00\x00"), "font/woff"},
 	{"woff2 sample", []byte("\x77\x4f\x46\x32\x00\x01\x00\x00\x00"), "font/woff2"},
 	{"wasm sample", []byte("\x00\x61\x73\x6d\x01\x00"), "application/wasm"},
+
+	// Archive types
+	{"RAR v1.5-v4.0", []byte("Rar \x1A\x07\x00"), "application/x-rar-compressed"},
+	{"RAR v5+", []byte("Rar \x1A\x07\x01\x00"), "application/x-rar-compressed"},
 }
 
 func TestDetectContentType(t *testing.T) {