fix(broker): match service hosts case-insensitively

internal/broker/broker.go

@@ -585,10 +585,15 @@ func MatchService(host string, targetPort int, path string, services []Service)
 // matchHostPattern reports the tier and whether pattern matches host.
 // "*." matches exactly one subdomain level (e.g. "*.github.com" matches
 // "api.github.com" but not "a.b.github.com" or the bare "github.com").
+// Hostnames are case-insensitive (RFC 4343), so both sides are lowercased.
+// Only ASCII letters are folded: Unicode case mapping would turn e.g.
+// U+0130 into "i" and let a different IDNA domain match a service.
 func matchHostPattern(pattern, host string) (tier int, ok bool) {
 	if h, _, err := net.SplitHostPort(pattern); err == nil {
 		pattern = h
 	}
+	pattern = asciiLower(pattern)
+	host = asciiLower(host)
 	if pattern == host {
 		return HostTierExact, true
 	}
@@ -604,6 +609,17 @@ func matchHostPattern(pattern, host string) (tier int, ok bool) {
 	return 0, false
 }
 
+// asciiLower lowercases ASCII letters in s and leaves all other bytes alone.
+func asciiLower(s string) string {
+	b := []byte(s)
+	for i, c := range b {
+		if 'A' <= c && c <= 'Z' {
+			b[i] = c + ('a' - 'A')
+		}
+	}
+	return string(b)
+}
+
 // AnyHostMatches reports whether any service's host pattern matches
 // host, ignoring paths. Used to filter discovered hosts against the
 // current service list so hosts that are already covered by a

internal/broker/broker_test.go

@@ -42,6 +42,51 @@ func TestMatchServiceWildcard(t *testing.T) {
 	}
 }
 
+func TestMatchServiceHostCaseInsensitive(t *testing.T) {
+	services := []Service{
+		{Name: "stripe", Host: "api.stripe.com", Auth: Auth{Type: "bearer", Token: "STRIPE_KEY"}},
+		{Name: "github", Host: "*.GitHub.com", Auth: Auth{Type: "bearer", Token: "GH_TOKEN"}},
+	}
+	cases := []struct {
+		host string
+		want string
+		tier int
+	}{
+		{"API.Stripe.COM", "stripe", HostTierExact},
+		{"api.github.com", "github", HostTierWildcard},
+		{"Uploads.GITHUB.com", "github", HostTierWildcard},
+	}
+	for _, tc := range cases {
+		r, score := MatchService(tc.host, 0, "/", services)
+		if r == nil || r.Name != tc.want {
+			t.Fatalf("host %q: expected %s, got %+v", tc.host, tc.want, r)
+		}
+		if score.HostTier != tc.tier {
+			t.Fatalf("host %q: expected tier %d, got %d", tc.host, tc.tier, score.HostTier)
+		}
+	}
+	if !AnyHostMatches("API.STRIPE.COM", services) {
+		t.Fatal("expected AnyHostMatches to ignore host case")
+	}
+}
+
+func TestMatchServiceHostNonASCIINotFolded(t *testing.T) {
+	services := []Service{
+		{Name: "stripe", Host: "api.stripe.com", Auth: Auth{Type: "bearer", Token: "STRIPE_KEY"}},
+		{Name: "kube", Host: "*.k8s.example.com", Auth: Auth{Type: "bearer", Token: "KUBE_TOKEN"}},
+	}
+	// U+0130 and the Kelvin sign U+212A lowercase to ASCII "i" and "k"
+	// under Unicode rules, but name different IDNA domains.
+	for _, host := range []string{"api.str\u0130pe.com", "api.\u212A8s.example.com"} {
+		if r, _ := MatchService(host, 0, "/", services); r != nil {
+			t.Fatalf("host %q: expected no match, got %s", host, r.Name)
+		}
+		if AnyHostMatches(host, services) {
+			t.Fatalf("host %q: expected AnyHostMatches to be false", host)
+		}
+	}
+}
+
 func TestMatchServiceNoMatch(t *testing.T) {
 	services := []Service{
 		{Name: "stripe", Host: "api.stripe.com", Auth: Auth{Type: "bearer", Token: "STRIPE_KEY"}},