Support comma-separated CORS_HEADER for multiple origins.

Parse CORS_HEADER as a list: * for all origins, or reflect matching
request Origin when multiple specific origins are configured. Add Vary:
Origin for the allowlist case. Update .env.example and CORS tests.

internal/config/config.go

@@ -63,10 +63,10 @@ type Config struct {
 	RateLimitPerMin   int
 	ReservedUsernames []string
 
-	// CORS: exact origin list = FRONTEND_URL ∪ CORS_ORIGINS; loopback hosts if CORS_ALLOW_LOCALHOST.
-	CORSExtraOrigins     []string
-	CORSAllowLocalhost   bool
-	CORSAllowCredentials bool
+	// CORSOrigins is parsed from the CORS_HEADER env var (comma-separated).
+	// Use "*" to allow all origins, or list specific origins like
+	// "https://example.com,https://other.example".
+	CORSOrigins []string
 }
 
 func Load() (*Config, error) {
@@ -113,9 +113,7 @@ func Load() (*Config, error) {
 		LogLevel:          env("LOG_LEVEL", "info"),
 		RateLimitPerMin:   envInt("RATE_LIMIT_PER_MIN", 30),
 		ReservedUsernames: csv(env("RESERVED_USERNAMES", "")),
-		CORSExtraOrigins:  csv(env("CORS_ORIGINS", "")),
-		CORSAllowLocalhost:   envBool("CORS_ALLOW_LOCALHOST", true),
-		CORSAllowCredentials: envBool("CORS_ALLOW_CREDENTIALS", false),
+		CORSOrigins:       csv(env("CORS_HEADER", "*")),
 	}
 
 	if err := Validate(c); err != nil {
@@ -181,22 +179,3 @@ func csvInt(v string) []int {
 }
 
 func (c *Config) Addr() string { return fmt.Sprintf(":%d", c.Port) }
-
-// CORSExactOrigins lists allowed browser Origins for exact match (before loopback wildcard).
-func (c *Config) CORSExactOrigins() []string {
-	seen := make(map[string]bool)
-	out := make([]string, 0, 4+len(c.CORSExtraOrigins))
-	add := func(s string) {
-		s = strings.TrimSpace(s)
-		if s == "" || seen[s] {
-			return
-		}
-		seen[s] = true
-		out = append(out, s)
-	}
-	add(c.FrontendURL)
-	for _, o := range c.CORSExtraOrigins {
-		add(o)
-	}
-	return out
-}

internal/http/middleware/cors.go

@@ -2,27 +2,44 @@ package middleware
 
 import (
 	"net/http"
-	"net/url"
-	"strings"
 
 	"github.com/noderunners/nip05api/internal/config"
 )
 
-// CORS sends at most one Access-Control-Allow-Origin value (echo of request Origin).
-// Configure FRONTEND_URL, optional CORS_ORIGINS, and CORS_ALLOW_LOCALHOST / CORS_ALLOW_CREDENTIALS.
+// CORS sets Access-Control-Allow-Origin based on the CORS_HEADER env var.
+//
+// Supports "*" (allow all), a single origin, or a comma-separated list.
+// When multiple origins are configured the middleware reflects the request
+// Origin back if it matches one of the allowed values (the HTTP spec forbids
+// sending more than one origin in the header).
 func CORS(cfg *config.Config) func(http.Handler) http.Handler {
+	allowAll := len(cfg.CORSOrigins) == 1 && cfg.CORSOrigins[0] == "*"
+
+	allowed := make(map[string]bool, len(cfg.CORSOrigins))
+	for _, o := range cfg.CORSOrigins {
+		allowed[o] = true
+	}
+
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			origin := r.Header.Get("Origin")
+			var origin string
+			if allowAll {
+				origin = "*"
+			} else {
+				reqOrigin := r.Header.Get("Origin")
+				if allowed[reqOrigin] {
+					origin = reqOrigin
+				}
+			}
 
-			if origin != "" && originAllowed(origin, cfg) {
+			if origin != "" {
 				h := w.Header()
 				h.Set("Access-Control-Allow-Origin", origin)
 				h.Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
 				h.Set("Access-Control-Allow-Headers", "Content-Type, X-API-Key, Authorization")
 				h.Set("Access-Control-Max-Age", "86400")
-				if cfg.CORSAllowCredentials {
-					h.Set("Access-Control-Allow-Credentials", "true")
+				if !allowAll {
+					h.Set("Vary", "Origin")
 				}
 			}
 
@@ -35,36 +52,3 @@ func CORS(cfg *config.Config) func(http.Handler) http.Handler {
 		})
 	}
 }
-
-func originAllowed(origin string, cfg *config.Config) bool {
-	if origin == "" {
-		return false
-	}
-
-	u, err := url.Parse(origin)
-	if err != nil || u.Scheme == "" || u.Host == "" {
-		return false
-	}
-
-	for _, allowed := range cfg.CORSExactOrigins() {
-		if origin == allowed {
-			return true
-		}
-	}
-
-	if cfg.CORSAllowLocalhost && isLoopbackOrigin(u) {
-		return true
-	}
-
-	return false
-}
-
-func isLoopbackOrigin(u *url.URL) bool {
-	host := strings.TrimSuffix(strings.ToLower(u.Hostname()), ".")
-	switch host {
-	case "localhost", "127.0.0.1", "::1":
-		return true
-	default:
-		return false
-	}
-}

internal/http/server_test.go

@@ -48,6 +48,7 @@ func newFixture(t *testing.T) *fixture {
 		Expiry:            config.ExpiryConfig{GraceDays: 30},
 		ReservedUsernames: []string{"admin", "root"},
 		RateLimitPerMin:   0, // disabled in tests
+		CORSOrigins:       []string{"*"},
 	}
 	tmpls, _ := messages.Load("/nonexistent.yaml")
 	users := user.NewService(user.NewRepo(d), cfg.ReservedUsernames)
@@ -553,6 +554,29 @@ func TestDocsPage(t *testing.T) {
 	}
 }
 
+func TestCORSHeader(t *testing.T) {
+	f := newFixture(t)
+
+	resp, _ := f.get(t, "/healthz")
+	if got := resp.Header.Get("Access-Control-Allow-Origin"); got != "*" {
+		t.Errorf("expected Access-Control-Allow-Origin=*, got %q", got)
+	}
+
+	req, _ := http.NewRequest("OPTIONS", f.srv.URL+"/v1/pricing", nil)
+	req.Header.Set("Origin", "https://random-frontend.example")
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusNoContent {
+		t.Errorf("expected 204 on OPTIONS preflight, got %d", resp.StatusCode)
+	}
+	if got := resp.Header.Get("Access-Control-Allow-Origin"); got != "*" {
+		t.Errorf("expected Access-Control-Allow-Origin=*, got %q", got)
+	}
+}
+
 func TestBodyLimit(t *testing.T) {
 	f := newFixture(t)
 	huge := bytes.Repeat([]byte("a"), 2<<20) // 2 MiB