gateway-api: make wildcards suffix matchers (e.g. match multiple labels)

source/gateway.go

@@ -19,6 +19,7 @@ package source
 import (
 	"context"
 	"fmt"
+	"net/netip"
 	"sort"
 	"strings"
 	"text/template"
@@ -486,39 +487,89 @@ func gwProtocolMatches(a, b v1.ProtocolType) bool {
 }
 
 // gwMatchingHost returns the most-specific overlapping host and a bool indicating if one was found.
-// For example, if one host is "*.foo.com" and the other is "bar.foo.com", "bar.foo.com" will be returned.
-// An empty string matches anything.
-func gwMatchingHost(gwHost, rtHost string) (string, bool) {
-	gwHost = toLowerCaseASCII(gwHost) // TODO: trim "." suffix?
-	rtHost = toLowerCaseASCII(rtHost) // TODO: trim "." suffix?
+// Hostnames that are prefixed with a wildcard label (`*.`) are interpreted as a suffix match.
+// That means that "*.example.com" would match both "test.example.com" and "foo.test.example.com",
+// but not "example.com". An empty string matches anything.
+func gwMatchingHost(a, b string) (string, bool) {
+	var ok bool
+	if a, ok = gwHost(a); !ok {
+		return "", false
+	}
+	if b, ok = gwHost(b); !ok {
+		return "", false
+	}
 
-	if gwHost == "" {
-		return rtHost, true
+	if a == "" {
+		return b, true
 	}
-	if rtHost == "" {
-		return gwHost, true
+	if b == "" || a == b {
+		return a, true
 	}
+	if na, nb := len(a), len(b); nb < na || (na == nb && strings.HasPrefix(b, "*.")) {
+		a, b = b, a
+	}
+	if strings.HasPrefix(a, "*.") && strings.HasSuffix(b, a[1:]) {
+		return b, true
+	}
+	return "", false
+}
 
-	gwParts := strings.Split(gwHost, ".")
-	rtParts := strings.Split(rtHost, ".")
-	if len(gwParts) != len(rtParts) {
+// gwHost returns the canonical host and a value indicating if it's valid.
+func gwHost(host string) (string, bool) {
+	if host == "" {
+		return "", true
+	}
+	if isIPAddr(host) || !isDNS1123Domain(strings.TrimPrefix(host, "*.")) {
 		return "", false
 	}
+	return toLowerCaseASCII(host), true // TODO: trim "." suffix?
+}
+
+// isIPAddr returns whether s in an IP address.
+func isIPAddr(s string) bool {
+	_, err := netip.ParseAddr(s)
+	return err == nil
+}
 
-	host := rtHost
-	for i, gwPart := range gwParts {
-		switch rtPart := rtParts[i]; {
-		case rtPart == gwPart:
-			// continue
-		case i == 0 && gwPart == "*":
-			// continue
-		case i == 0 && rtPart == "*":
-			host = gwHost // gwHost is more specific
-		default:
-			return "", false
+// isDNS1123Domain returns whether s is a valid domain name according to RFC 1123.
+func isDNS1123Domain(s string) bool {
+	if n := len(s); n == 0 || n > 255 {
+		return false
+	}
+	for lbl, rest := "", s; rest != ""; {
+		if lbl, rest, _ = strings.Cut(rest, "."); !isDNS1123Label(lbl) {
+			return false
 		}
 	}
-	return host, true
+	return true
+}
+
+// isDNS1123Label returns whether s is a valid domain label according to RFC 1123.
+func isDNS1123Label(s string) bool {
+	n := len(s)
+	if n == 0 || n > 63 {
+		return false
+	}
+	if !isAlphaNum(s[0]) || !isAlphaNum(s[n-1]) {
+		return false
+	}
+	for i, k := 1, n-1; i < k; i++ {
+		if b := s[i]; b != '-' && !isAlphaNum(b) {
+			return false
+		}
+	}
+	return true
+}
+
+func isAlphaNum(b byte) bool {
+	switch {
+	case 'a' <= b && b <= 'z',
+		'A' <= b && b <= 'Z',
+		'0' <= b && b <= '9':
+		return true
+	default:
+		return false
+	}
 }
 
 func strVal(ptr *string, def string) string {

source/gateway_test.go

@@ -0,0 +1,175 @@
+package source
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestGatewayMatchingHost(t *testing.T) {
+	tests := []struct {
+		desc string
+		a, b string
+		host string
+		ok   bool
+	}{
+		{
+			desc: "ipv4-rejected",
+			a:    "1.2.3.4",
+			ok:   false,
+		},
+		{
+			desc: "ipv6-rejected",
+			a:    "2001:0db8:85a3:0000:0000:8a2e:0370:7334",
+			ok:   false,
+		},
+		{
+			desc: "empty-matches-empty",
+			ok:   true,
+		},
+		{
+			desc: "empty-matches-nonempty",
+			a:    "example.net",
+			host: "example.net",
+			ok:   true,
+		},
+		{
+			desc: "simple-match",
+			a:    "example.net",
+			b:    "example.net",
+			host: "example.net",
+			ok:   true,
+		},
+		{
+			desc: "wildcard-matches-longer",
+			a:    "*.example.net",
+			b:    "test.example.net",
+			host: "test.example.net",
+			ok:   true,
+		},
+		{
+			desc: "wildcard-matches-equal-length",
+			a:    "*.example.net",
+			b:    "a.example.net",
+			host: "a.example.net",
+			ok:   true,
+		},
+		{
+			desc: "wildcard-matches-multiple-subdomains",
+			a:    "*.example.net",
+			b:    "foo.bar.test.example.net",
+			host: "foo.bar.test.example.net",
+			ok:   true,
+		},
+		{
+			desc: "wildcard-doesnt-match-parent",
+			a:    "*.example.net",
+			b:    "example.net",
+			ok:   false,
+		},
+		{
+			desc: "wildcard-must-be-complete-label",
+			a:    "*example.net",
+			b:    "test.example.net",
+			ok:   false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			for i := 0; i < 2; i++ {
+				if host, ok := gwMatchingHost(tt.a, tt.b); host != tt.host || ok != tt.ok {
+					t.Errorf(
+						"gwMatchingHost(%q, %q); got: %q, %v; want: %q, %v",
+						tt.a, tt.b, host, ok, tt.host, tt.ok,
+					)
+				}
+				tt.a, tt.b = tt.b, tt.a
+			}
+		})
+
+	}
+}
+
+func TestIsDNS1123Domain(t *testing.T) {
+	tests := []struct {
+		desc string
+		in   string
+		ok   bool
+	}{
+		{
+			desc: "empty",
+			ok:   false,
+		},
+		{
+			desc: "label-too-long",
+			in:   strings.Repeat("x", 64) + ".example.net",
+			ok:   false,
+		},
+		{
+			desc: "domain-too-long",
+			in:   strings.Repeat("testing.", 256/(len("testing."))) + "example.net",
+			ok:   false,
+		},
+		{
+			desc: "hostname",
+			in:   "example",
+			ok:   true,
+		},
+		{
+			desc: "domain",
+			in:   "example.net",
+			ok:   true,
+		},
+		{
+			desc: "subdomain",
+			in:   "test.example.net",
+			ok:   true,
+		},
+		{
+			desc: "dashes",
+			in:   "test-with-dash.example.net",
+			ok:   true,
+		},
+		{
+			desc: "dash-prefix",
+			in:   "-dash-prefix.example.net",
+			ok:   false,
+		},
+		{
+			desc: "dash-suffix",
+			in:   "dash-suffix-.example.net",
+			ok:   false,
+		},
+		{
+			desc: "underscore",
+			in:   "under_score.example.net",
+			ok:   false,
+		},
+		{
+			desc: "plus",
+			in:   "pl+us.example.net",
+			ok:   false,
+		},
+		{
+			desc: "brackets",
+			in:   "bra[k]ets.example.net",
+			ok:   false,
+		},
+		{
+			desc: "parens",
+			in:   "pa[re]ns.example.net",
+			ok:   false,
+		},
+		{
+			desc: "wild",
+			in:   "*.example.net",
+			ok:   false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			if ok := isDNS1123Domain(tt.in); ok != tt.ok {
+				t.Errorf("isDNS1123Domain(%q); got: %v; want: %v", tt.in, ok, tt.ok)
+			}
+		})
+	}
+}