feat: add env-based configuration and token-in-cookie auth

Implement 12-factor configuration via environment variables and
token-in-cookie authentication for Gitea API access.

- internal/config/config.go: reads GITEA_URL, GITEA_TOKEN, LISTEN_ADDR,
  SESSION_SECRET from environment with validation
- internal/auth/cookie.go: HMAC-signed HTTP-only cookie for storing
  Gitea API tokens (Secure, SameSite=Strict)
- internal/middleware/auth.go: extracts token from cookie, injects into
  request context, redirects unauthenticated users to /settings
- internal/middleware/logging.go: structured JSON request logging
- internal/handlers/settings.go: settings page for entering/removing
  Gitea API token with mobile-first dark UI
- cmd/server/main.go: integrated config, auth middleware, and settings

Includes unit tests for config loading, cookie signing/verification,
and auth middleware bypass/redirect logic.

Closes leeworks-agents/gitea-mobile#2

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/auth/cookie.go

@@ -0,0 +1,104 @@
+package auth
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"net/http"
+	"strings"
+	"time"
+)
+
+const (
+	cookieName = "gitea_token"
+	cookieMaxAge = 30 * 24 * 60 * 60 // 30 days in seconds
+)
+
+var (
+	ErrInvalidSignature = errors.New("invalid cookie signature")
+	ErrMalformedCookie  = errors.New("malformed cookie value")
+)
+
+// SetTokenCookie stores a Gitea API token in a signed HTTP-only cookie.
+func SetTokenCookie(w http.ResponseWriter, token string, secret string, secure bool) {
+	signed := sign(token, secret)
+
+	http.SetCookie(w, &http.Cookie{
+		Name:     cookieName,
+		Value:    signed,
+		Path:     "/",
+		MaxAge:   cookieMaxAge,
+		HttpOnly: true,
+		Secure:   secure,
+		SameSite: http.SameSiteStrictMode,
+		Expires:  time.Now().Add(30 * 24 * time.Hour),
+	})
+}
+
+// ClearTokenCookie removes the token cookie.
+func ClearTokenCookie(w http.ResponseWriter, secure bool) {
+	http.SetCookie(w, &http.Cookie{
+		Name:     cookieName,
+		Value:    "",
+		Path:     "/",
+		MaxAge:   -1,
+		HttpOnly: true,
+		Secure:   secure,
+		SameSite: http.SameSiteStrictMode,
+	})
+}
+
+// GetToken extracts and verifies the Gitea API token from the request cookie.
+// Returns the token string or an error if the cookie is missing or invalid.
+func GetToken(r *http.Request, secret string) (string, error) {
+	cookie, err := r.Cookie(cookieName)
+	if err != nil {
+		return "", err
+	}
+
+	token, err := verify(cookie.Value, secret)
+	if err != nil {
+		return "", err
+	}
+
+	return token, nil
+}
+
+// sign creates a signed cookie value: base64(token).base64(hmac-sha256(token))
+func sign(token string, secret string) string {
+	encodedToken := base64.URLEncoding.EncodeToString([]byte(token))
+	mac := computeHMAC(encodedToken, secret)
+	return fmt.Sprintf("%s.%s", encodedToken, mac)
+}
+
+// verify checks the HMAC signature and returns the original token.
+func verify(signed string, secret string) (string, error) {
+	parts := strings.SplitN(signed, ".", 2)
+	if len(parts) != 2 {
+		return "", ErrMalformedCookie
+	}
+
+	encodedToken := parts[0]
+	providedMAC := parts[1]
+	expectedMAC := computeHMAC(encodedToken, secret)
+
+	if !hmac.Equal([]byte(providedMAC), []byte(expectedMAC)) {
+		return "", ErrInvalidSignature
+	}
+
+	tokenBytes, err := base64.URLEncoding.DecodeString(encodedToken)
+	if err != nil {
+		return "", ErrMalformedCookie
+	}
+
+	return string(tokenBytes), nil
+}
+
+// computeHMAC generates a base64-encoded HMAC-SHA256 of the given data.
+func computeHMAC(data string, secret string) string {
+	h := hmac.New(sha256.New, []byte(secret))
+	h.Write([]byte(data))
+	return base64.URLEncoding.EncodeToString(h.Sum(nil))
+}

internal/auth/cookie_test.go

@@ -0,0 +1,89 @@
+package auth
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+const testSecret = "test-secret-that-is-at-least-32-chars-long"
+
+func TestSignAndVerify(t *testing.T) {
+	token := "abc123-gitea-token"
+	signed := sign(token, testSecret)
+
+	got, err := verify(signed, testSecret)
+	if err != nil {
+		t.Fatalf("verify failed: %v", err)
+	}
+	if got != token {
+		t.Errorf("got %q, want %q", got, token)
+	}
+}
+
+func TestVerify_InvalidSignature(t *testing.T) {
+	token := "abc123-gitea-token"
+	signed := sign(token, testSecret)
+
+	_, err := verify(signed, "wrong-secret-that-is-at-least-32-chars")
+	if err != ErrInvalidSignature {
+		t.Errorf("expected ErrInvalidSignature, got %v", err)
+	}
+}
+
+func TestVerify_MalformedCookie(t *testing.T) {
+	_, err := verify("no-dot-separator", testSecret)
+	if err != ErrMalformedCookie {
+		t.Errorf("expected ErrMalformedCookie, got %v", err)
+	}
+}
+
+func TestSetAndGetToken(t *testing.T) {
+	token := "my-gitea-api-token"
+
+	// Create a response recorder to capture the Set-Cookie header.
+	w := httptest.NewRecorder()
+	SetTokenCookie(w, token, testSecret, false)
+
+	// Extract the cookie from the response.
+	resp := w.Result()
+	cookies := resp.Cookies()
+	if len(cookies) == 0 {
+		t.Fatal("expected a cookie to be set")
+	}
+
+	// Create a new request with the cookie.
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	req.AddCookie(cookies[0])
+
+	got, err := GetToken(req, testSecret)
+	if err != nil {
+		t.Fatalf("GetToken failed: %v", err)
+	}
+	if got != token {
+		t.Errorf("got %q, want %q", got, token)
+	}
+}
+
+func TestGetToken_NoCookie(t *testing.T) {
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+
+	_, err := GetToken(req, testSecret)
+	if err == nil {
+		t.Fatal("expected error for missing cookie")
+	}
+}
+
+func TestClearTokenCookie(t *testing.T) {
+	w := httptest.NewRecorder()
+	ClearTokenCookie(w, false)
+
+	resp := w.Result()
+	cookies := resp.Cookies()
+	if len(cookies) == 0 {
+		t.Fatal("expected a cookie to be set")
+	}
+	if cookies[0].MaxAge != -1 {
+		t.Errorf("MaxAge = %d, want -1", cookies[0].MaxAge)
+	}
+}

internal/config/config.go

@@ -0,0 +1,50 @@
+package config
+
+import (
+	"fmt"
+	"os"
+)
+
+// Config holds application configuration loaded from environment variables.
+type Config struct {
+	// GiteaURL is the base URL of the Gitea instance.
+	GiteaURL string
+
+	// GiteaToken is the default API token (optional; users can set their own via cookie).
+	GiteaToken string
+
+	// ListenAddr is the server listen address.
+	ListenAddr string
+
+	// SessionSecret is the HMAC key for signing session cookies.
+	SessionSecret string
+}
+
+// Load reads configuration from environment variables.
+// Returns an error if required variables are missing.
+func Load() (*Config, error) {
+	cfg := &Config{
+		GiteaURL:      os.Getenv("GITEA_URL"),
+		GiteaToken:    os.Getenv("GITEA_TOKEN"),
+		ListenAddr:    os.Getenv("LISTEN_ADDR"),
+		SessionSecret: os.Getenv("SESSION_SECRET"),
+	}
+
+	if cfg.ListenAddr == "" {
+		cfg.ListenAddr = ":8080"
+	}
+
+	if cfg.GiteaURL == "" {
+		return nil, fmt.Errorf("GITEA_URL environment variable is required")
+	}
+
+	if cfg.SessionSecret == "" {
+		return nil, fmt.Errorf("SESSION_SECRET environment variable is required")
+	}
+
+	if len(cfg.SessionSecret) < 32 {
+		return nil, fmt.Errorf("SESSION_SECRET must be at least 32 characters")
+	}
+
+	return cfg, nil
+}

internal/config/config_test.go

@@ -0,0 +1,89 @@
+package config
+
+import (
+	"os"
+	"testing"
+)
+
+func TestLoad_Success(t *testing.T) {
+	os.Setenv("GITEA_URL", "https://gitea.example.com")
+	os.Setenv("SESSION_SECRET", "test-secret-that-is-at-least-32-chars-long")
+	os.Setenv("LISTEN_ADDR", ":9090")
+	os.Setenv("GITEA_TOKEN", "test-token")
+	defer func() {
+		os.Unsetenv("GITEA_URL")
+		os.Unsetenv("SESSION_SECRET")
+		os.Unsetenv("LISTEN_ADDR")
+		os.Unsetenv("GITEA_TOKEN")
+	}()
+
+	cfg, err := Load()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if cfg.GiteaURL != "https://gitea.example.com" {
+		t.Errorf("GiteaURL = %q, want %q", cfg.GiteaURL, "https://gitea.example.com")
+	}
+	if cfg.ListenAddr != ":9090" {
+		t.Errorf("ListenAddr = %q, want %q", cfg.ListenAddr, ":9090")
+	}
+	if cfg.GiteaToken != "test-token" {
+		t.Errorf("GiteaToken = %q, want %q", cfg.GiteaToken, "test-token")
+	}
+}
+
+func TestLoad_DefaultListenAddr(t *testing.T) {
+	os.Setenv("GITEA_URL", "https://gitea.example.com")
+	os.Setenv("SESSION_SECRET", "test-secret-that-is-at-least-32-chars-long")
+	os.Unsetenv("LISTEN_ADDR")
+	defer func() {
+		os.Unsetenv("GITEA_URL")
+		os.Unsetenv("SESSION_SECRET")
+	}()
+
+	cfg, err := Load()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if cfg.ListenAddr != ":8080" {
+		t.Errorf("ListenAddr = %q, want %q", cfg.ListenAddr, ":8080")
+	}
+}
+
+func TestLoad_MissingGiteaURL(t *testing.T) {
+	os.Unsetenv("GITEA_URL")
+	os.Setenv("SESSION_SECRET", "test-secret-that-is-at-least-32-chars-long")
+	defer os.Unsetenv("SESSION_SECRET")
+
+	_, err := Load()
+	if err == nil {
+		t.Fatal("expected error for missing GITEA_URL")
+	}
+}
+
+func TestLoad_MissingSessionSecret(t *testing.T) {
+	os.Setenv("GITEA_URL", "https://gitea.example.com")
+	os.Unsetenv("SESSION_SECRET")
+	defer os.Unsetenv("GITEA_URL")
+
+	_, err := Load()
+	if err == nil {
+		t.Fatal("expected error for missing SESSION_SECRET")
+	}
+}
+
+func TestLoad_ShortSessionSecret(t *testing.T) {
+	os.Setenv("GITEA_URL", "https://gitea.example.com")
+	os.Setenv("SESSION_SECRET", "tooshort")
+	defer func() {
+		os.Unsetenv("GITEA_URL")
+		os.Unsetenv("SESSION_SECRET")
+	}()
+
+	_, err := Load()
+	if err == nil {
+		t.Fatal("expected error for short SESSION_SECRET")
+	}
+}

internal/handlers/settings.go

@@ -0,0 +1,177 @@
+package handlers
+
+import (
+	"html/template"
+	"net/http"
+	"strings"
+
+	"gitea.leeworks.dev/0xwheatyz/gitea-mobile/internal/auth"
+	"gitea.leeworks.dev/0xwheatyz/gitea-mobile/internal/middleware"
+)
+
+var settingsTemplate = template.Must(template.New("settings").Parse(`<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover">
+  <title>Settings — Gitea Mobile</title>
+  <style>
+    * { box-sizing: border-box; margin: 0; padding: 0; }
+    body {
+      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
+      background: #0d1117; color: #e6edf3;
+      padding: 1rem;
+      padding-top: max(1rem, env(safe-area-inset-top));
+    }
+    h1 { font-size: 1.5rem; margin-bottom: 1rem; }
+    .card {
+      background: #161b22; border: 1px solid #30363d; border-radius: 8px;
+      padding: 1rem; margin-bottom: 1rem;
+    }
+    label { display: block; font-size: 0.875rem; color: #8b949e; margin-bottom: 0.5rem; }
+    input[type="text"], input[type="password"] {
+      width: 100%; padding: 0.5rem; font-size: 1rem;
+      background: #0d1117; border: 1px solid #30363d; border-radius: 6px;
+      color: #e6edf3; margin-bottom: 1rem;
+    }
+    input:focus { outline: none; border-color: #58a6ff; }
+    button {
+      width: 100%; padding: 0.75rem; font-size: 1rem; font-weight: 600;
+      background: #238636; color: #fff; border: none; border-radius: 6px;
+      cursor: pointer;
+    }
+    button:active { background: #2ea043; }
+    .message {
+      padding: 0.75rem; border-radius: 6px; margin-bottom: 1rem;
+      font-size: 0.875rem;
+    }
+    .message.success { background: #0d2818; border: 1px solid #238636; color: #3fb950; }
+    .message.error { background: #2d1117; border: 1px solid #da3633; color: #f85149; }
+    .message.info { background: #0c1d2e; border: 1px solid #1f6feb; color: #58a6ff; }
+    .hint { font-size: 0.75rem; color: #8b949e; margin-top: 0.25rem; margin-bottom: 1rem; }
+    .status { font-size: 0.875rem; color: #8b949e; }
+    .status .connected { color: #3fb950; }
+    .logout-btn {
+      background: #21262d; border: 1px solid #30363d; margin-top: 0.5rem;
+    }
+    .logout-btn:active { background: #30363d; }
+  </style>
+</head>
+<body>
+  <h1>Settings</h1>
+
+  {{if .Message}}
+  <div class="message {{.MessageType}}">{{.Message}}</div>
+  {{end}}
+
+  {{if .HasToken}}
+  <div class="card">
+    <p class="status">Status: <span class="connected">Connected</span></p>
+    <p class="hint">A Gitea API token is configured.</p>
+    <form method="POST" action="/settings">
+      <input type="hidden" name="action" value="logout">
+      <button type="submit" class="logout-btn">Remove Token</button>
+    </form>
+  </div>
+  {{end}}
+
+  <div class="card">
+    <form method="POST" action="/settings">
+      <input type="hidden" name="action" value="save">
+      <label for="token">Gitea API Token</label>
+      <input type="password" id="token" name="token" placeholder="Enter your Gitea API token" required>
+      <p class="hint">Generate a token at your Gitea instance under Settings &rarr; Applications.</p>
+      <button type="submit">{{if .HasToken}}Update Token{{else}}Save Token{{end}}</button>
+    </form>
+  </div>
+
+  {{if .HasToken}}
+  <p style="text-align:center; margin-top:1rem;">
+    <a href="/" style="color:#58a6ff; text-decoration:none;">Back to Dashboard</a>
+  </p>
+  {{end}}
+</body>
+</html>`))
+
+// SettingsHandler handles GET and POST requests for the settings page.
+type SettingsHandler struct {
+	SessionSecret string
+	SecureCookies bool
+}
+
+type settingsData struct {
+	HasToken    bool
+	Message     string
+	MessageType string // "success", "error", "info"
+}
+
+// ServeHTTP handles the settings page.
+func (h *SettingsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	switch r.Method {
+	case http.MethodGet:
+		h.handleGet(w, r)
+	case http.MethodPost:
+		h.handlePost(w, r)
+	default:
+		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+	}
+}
+
+func (h *SettingsHandler) handleGet(w http.ResponseWriter, r *http.Request) {
+	hasToken := false
+	if token := middleware.TokenFromContext(r.Context()); token != "" {
+		hasToken = true
+	} else if _, err := auth.GetToken(r, h.SessionSecret); err == nil {
+		hasToken = true
+	}
+
+	data := settingsData{HasToken: hasToken}
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	settingsTemplate.Execute(w, data)
+}
+
+func (h *SettingsHandler) handlePost(w http.ResponseWriter, r *http.Request) {
+	if err := r.ParseForm(); err != nil {
+		h.renderWithMessage(w, r, "Failed to parse form.", "error")
+		return
+	}
+
+	action := r.FormValue("action")
+
+	switch action {
+	case "logout":
+		auth.ClearTokenCookie(w, h.SecureCookies)
+		h.renderWithMessage(w, r, "Token removed successfully.", "success")
+		return
+
+	case "save":
+		token := strings.TrimSpace(r.FormValue("token"))
+		if token == "" {
+			h.renderWithMessage(w, r, "Token cannot be empty.", "error")
+			return
+		}
+
+		auth.SetTokenCookie(w, token, h.SessionSecret, h.SecureCookies)
+		// After saving, redirect to dashboard.
+		http.Redirect(w, r, "/", http.StatusSeeOther)
+		return
+
+	default:
+		h.renderWithMessage(w, r, "Unknown action.", "error")
+	}
+}
+
+func (h *SettingsHandler) renderWithMessage(w http.ResponseWriter, r *http.Request, msg, msgType string) {
+	hasToken := false
+	if _, err := auth.GetToken(r, h.SessionSecret); err == nil {
+		hasToken = true
+	}
+
+	data := settingsData{
+		HasToken:    hasToken,
+		Message:     msg,
+		MessageType: msgType,
+	}
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	settingsTemplate.Execute(w, data)
+}

internal/middleware/auth.go

@@ -0,0 +1,54 @@
+package middleware
+
+import (
+	"context"
+	"log/slog"
+	"net/http"
+
+	"gitea.leeworks.dev/0xwheatyz/gitea-mobile/internal/auth"
+)
+
+// contextKey is a private type for context keys in this package.
+type contextKey string
+
+const (
+	// TokenContextKey is the context key for the Gitea API token.
+	TokenContextKey contextKey = "gitea_token"
+)
+
+// TokenFromContext extracts the Gitea API token from the request context.
+func TokenFromContext(ctx context.Context) string {
+	token, _ := ctx.Value(TokenContextKey).(string)
+	return token
+}
+
+// Auth returns middleware that checks for a valid token cookie.
+// Unauthenticated requests are redirected to the settings page.
+// The /health, /settings, and /static/ paths are exempt from auth.
+func Auth(sessionSecret string) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			// Skip auth for exempt paths.
+			path := r.URL.Path
+			if path == "/health" || path == "/settings" || hasPrefix(path, "/static/") {
+				next.ServeHTTP(w, r)
+				return
+			}
+
+			token, err := auth.GetToken(r, sessionSecret)
+			if err != nil || token == "" {
+				slog.Debug("unauthenticated request, redirecting to settings", "path", path, "error", err)
+				http.Redirect(w, r, "/settings", http.StatusSeeOther)
+				return
+			}
+
+			// Inject token into request context.
+			ctx := context.WithValue(r.Context(), TokenContextKey, token)
+			next.ServeHTTP(w, r.WithContext(ctx))
+		})
+	}
+}
+
+func hasPrefix(s, prefix string) bool {
+	return len(s) >= len(prefix) && s[:len(prefix)] == prefix
+}

internal/middleware/auth_test.go

@@ -0,0 +1,85 @@
+package middleware
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"gitea.leeworks.dev/0xwheatyz/gitea-mobile/internal/auth"
+)
+
+const testSecret = "test-secret-that-is-at-least-32-chars-long"
+
+func TestAuth_HealthBypass(t *testing.T) {
+	handler := Auth(testSecret)(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "/health", nil)
+	w := httptest.NewRecorder()
+	handler.ServeHTTP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("status = %d, want %d", w.Code, http.StatusOK)
+	}
+}
+
+func TestAuth_SettingsBypass(t *testing.T) {
+	handler := Auth(testSecret)(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "/settings", nil)
+	w := httptest.NewRecorder()
+	handler.ServeHTTP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("status = %d, want %d", w.Code, http.StatusOK)
+	}
+}
+
+func TestAuth_RedirectWithoutToken(t *testing.T) {
+	handler := Auth(testSecret)(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	w := httptest.NewRecorder()
+	handler.ServeHTTP(w, req)
+
+	if w.Code != http.StatusSeeOther {
+		t.Errorf("status = %d, want %d", w.Code, http.StatusSeeOther)
+	}
+	if loc := w.Header().Get("Location"); loc != "/settings" {
+		t.Errorf("Location = %q, want %q", loc, "/settings")
+	}
+}
+
+func TestAuth_PassWithToken(t *testing.T) {
+	called := false
+	handler := Auth(testSecret)(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		called = true
+		token := TokenFromContext(r.Context())
+		if token != "my-token" {
+			t.Errorf("token = %q, want %q", token, "my-token")
+		}
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	// Set a token cookie.
+	cookieW := httptest.NewRecorder()
+	auth.SetTokenCookie(cookieW, "my-token", testSecret, false)
+	cookie := cookieW.Result().Cookies()[0]
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	req.AddCookie(cookie)
+	w := httptest.NewRecorder()
+	handler.ServeHTTP(w, req)
+
+	if !called {
+		t.Error("next handler was not called")
+	}
+	if w.Code != http.StatusOK {
+		t.Errorf("status = %d, want %d", w.Code, http.StatusOK)
+	}
+}

internal/middleware/logging.go

@@ -0,0 +1,38 @@
+package middleware
+
+import (
+	"log/slog"
+	"net/http"
+	"time"
+)
+
+// responseWriter wraps http.ResponseWriter to capture the status code.
+type responseWriter struct {
+	http.ResponseWriter
+	statusCode int
+}
+
+func (rw *responseWriter) WriteHeader(code int) {
+	rw.statusCode = code
+	rw.ResponseWriter.WriteHeader(code)
+}
+
+// Logging returns middleware that logs each HTTP request with structured logging.
+func Logging() func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			start := time.Now()
+			rw := &responseWriter{ResponseWriter: w, statusCode: http.StatusOK}
+
+			next.ServeHTTP(rw, r)
+
+			slog.Info("http request",
+				"method", r.Method,
+				"path", r.URL.Path,
+				"status", rw.statusCode,
+				"duration", time.Since(start).String(),
+				"remote", r.RemoteAddr,
+			)
+		})
+	}
+}