Properly parse r.RemoteAddr (#50)

* Properly parse r.RemoteAddr

* Add tests, and fix net.ParseCIDR issues with IPv6 addresses enclosed in brackets

auth_test.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"net/http"
+	"testing"
+)
+
+func TestUpdateAllowedFromIP(t *testing.T) {
+	userWithAllow := newACMETxt()
+	userWithAllow.AllowFrom = cidrslice{"192.168.1.2/32", "[::1]/128"}
+	userWithoutAllow := newACMETxt()
+
+	for i, test := range []struct {
+		remoteaddr string
+		expected   bool
+	}{
+		{"192.168.1.2:1234", true},
+		{"192.168.1.1:1234", false},
+		{"invalid", false},
+		{"[::1]:4567", true},
+	} {
+		newreq, _ := http.NewRequest("GET", "/whatever", nil)
+		newreq.RemoteAddr = test.remoteaddr
+		ret := updateAllowedFromIP(newreq, userWithAllow)
+		if test.expected != ret {
+			t.Errorf("Test %d: Unexpected result for user with allowForm set", i)
+		}
+
+		if !updateAllowedFromIP(newreq, userWithoutAllow) {
+			t.Errorf("Test %d: Unexpected result for user without allowForm set", i)
+		}
+	}
+}