fix: match actor DNS names case-insensitively at the router

cmd/atenet/internal/router/extproc_in_test.go

@@ -151,6 +151,12 @@ func TestParseActorRef(t *testing.T) {
 			want:    resources.ActorRef{Atespace: "team-a", Name: "my-actor"},
 			wantErr: false,
 		},
+		{
+			name:    "mixed-case host",
+			host:    "My-Actor.Team-A.actors.resources.substrate.ate.dev",
+			want:    resources.ActorRef{Atespace: "team-a", Name: "my-actor"},
+			wantErr: false,
+		},
 		{
 			name:    "missing atespace label",
 			host:    "my-actor.actors.resources.substrate.ate.dev",

internal/resources/actorref.go

@@ -71,9 +71,31 @@ func ActorRefFromActor(a *ateapipb.Actor) ActorRef {
 	}
 }
 
+// lowerASCII folds A-Z and leaves every other byte alone. Resource names are
+// DNS-1123 labels, so ASCII is the whole alphabet here, and strings.ToLower
+// would additionally fold characters outside it onto ASCII letters (the Kelvin
+// sign U+212A onto "k", U+017F onto "s"), letting a non-ASCII host reach an
+// actor under a spelling that is not its name.
+func lowerASCII(s string) string {
+	b := []byte(s)
+	for i, c := range b {
+		if c >= 'A' && c <= 'Z' {
+			b[i] = c + ('a' - 'A')
+		}
+	}
+	return string(b)
+}
+
 // ParseActorDNSName parses a DNS name for a given actor.
+//
+// The name is folded to lower case first. DNS lookups are case-insensitive
+// (RFC 4343), so a client that resolved "MyActor.MySpace.<suffix>" reaches us
+// with that spelling preserved in the Host header, while actor and atespace
+// names are always lower case. Folding keeps the request addressed to the same
+// actor its DNS lookup resolved to instead of failing to parse.
 func ParseActorDNSName(name string) (ActorRef, error) {
-	rest, found := strings.CutSuffix(strings.TrimSuffix(name, "."), "."+ActorDNSSuffix)
+	normalized := lowerASCII(strings.TrimSuffix(name, "."))
+	rest, found := strings.CutSuffix(normalized, "."+ActorDNSSuffix)
 	if !found {
 		return ActorRef{}, fmt.Errorf("invalid actor DNS name: must end with %s, got %q", ActorDNSSuffix, name)
 	}

internal/resources/actorref_test.go

@@ -56,8 +56,14 @@ func TestParseActorDNSName(t *testing.T) {
 		{"valid trailing dot", "act-1.team-a.actors.resources.substrate.ate.dev.", ActorRef{Atespace: "team-a", Name: "act-1"}, false},
 		{"wrong suffix", "act-1.team-a.example.com", ActorRef{}, true},
 		{"missing atespace", "act-1.actors.resources.substrate.ate.dev", ActorRef{}, true},
-		{"invalid actor name", "ACT-1.team-a.actors.resources.substrate.ate.dev", ActorRef{}, true},
-		{"invalid atespace", "act-1.TEAM.actors.resources.substrate.ate.dev", ActorRef{}, true},
+		{"mixed-case actor name", "ACT-1.team-a.actors.resources.substrate.ate.dev", ActorRef{Atespace: "team-a", Name: "act-1"}, false},
+		{"mixed-case atespace", "act-1.TEAM-A.actors.resources.substrate.ate.dev", ActorRef{Atespace: "team-a", Name: "act-1"}, false},
+		{"mixed-case suffix", "act-1.team-a.Actors.Resources.Substrate.Ate.Dev", ActorRef{Atespace: "team-a", Name: "act-1"}, false},
+		// strings.ToLower would fold the Kelvin sign onto "k" and hand "act-1k" a
+		// request addressed to a name no actor can have.
+		{"non-ASCII actor name", "act-1K.team-a.actors.resources.substrate.ate.dev", ActorRef{}, true},
+		{"invalid actor name", "act_1.team-a.actors.resources.substrate.ate.dev", ActorRef{}, true},
+		{"invalid atespace", "act-1.team_a.actors.resources.substrate.ate.dev", ActorRef{}, true},
 		{"host:port not accepted", "act-1.team-a.actors.resources.substrate.ate.dev:8080", ActorRef{}, true},
 		{"empty", "", ActorRef{}, true},
 	}