fix: unbracket a port-less IPv6 address in Forwarded

plugin.go

@@ -205,7 +205,13 @@ func parserFor(canon string) func(string) string {
 func parseForwarded(v string) string {
 	if m := forwardedRegex.FindStringSubmatch(v); len(m) > 1 {
 		// An IPv6 address (and any node-port) MUST be quoted, so trim the quotes.
-		return strings.Trim(m[1], `"`)
+		node := strings.Trim(m[1], `"`)
+		// A bracketed IPv6 address without a port is not a valid IP, so strip the brackets.
+		if strings.HasPrefix(node, "[") && strings.HasSuffix(node, "]") {
+			return node[1 : len(node)-1]
+		}
+
+		return node
 	}
 
 	return ""

tests/proxy_ip_test.go

@@ -84,6 +84,7 @@ func TestForwarded(t *testing.T) {
 		want   string
 	}{
 		{"for element is extracted", "by=foo;for=3.11.0.1;host=foo.workstation;proto=http", "3.11.0.1"},
+		{"bracketed IPv6 without port is unbracketed", `for="[2001:db8:cafe::17]";proto=http`, "2001:db8:cafe::17"},
 		{"trusted loopback stays loopback", "by=foo;for=127.0.0.1;host=foo.workstation;proto=http", loopback},
 		{"value without for= falls back to the peer", "foo.workstation", loopback},
 	}

trusted_test.go

@@ -29,6 +29,7 @@ func TestIP(t *testing.T) {
 		{tcip, "8.8.8.8", "8.8.8.8"},                                   // Single address
 		{forwarded, `for="_foo"`, "_foo"},                              // Hostname
 		{forwarded, `For="[2001:db8:cafe::17]:4711`, `[2001:db8:cafe::17]:4711`},      // IPv6 address
+		{forwarded, `for="[2001:db8:cafe::17]"`, `2001:db8:cafe::17`},                 // IPv6 address without port
 		{forwarded, `for=192.0.2.60;proto=http;by=203.0.113.43`, `192.0.2.60`},        // Multiple params
 		{forwarded, `for=192.0.2.43, for=198.51.100.17`, "192.0.2.43"},                // Multiple params
 		{forwarded, `for="workstation.local",for=198.51.100.17`, "workstation.local"}, // Hostname