fix: restrict SCP-like URLs to git user only and reject path traversal

- Changed SCP regex to only accept 'git' as the username
- Added path traversal check: reject URLs containing '..'
- Added test cases for non-git users and path traversal

internal/config/config.go

@@ -52,6 +52,7 @@ type Config struct {
 	MetricsUsername string
 	MetricsPassword string
 	SessionSecret   string
+	CORSOrigins     string
 	params          *Params
 	log             *slog.Logger
 }
@@ -102,6 +103,7 @@ func setupViper(name string) {
 	viper.SetDefault("METRICS_USERNAME", "")
 	viper.SetDefault("METRICS_PASSWORD", "")
 	viper.SetDefault("SESSION_SECRET", "")
+	viper.SetDefault("CORS_ORIGINS", "")
 }
 
 func buildConfig(log *slog.Logger, params *Params) (*Config, error) {
@@ -136,6 +138,7 @@ func buildConfig(log *slog.Logger, params *Params) (*Config, error) {
 		MetricsUsername: viper.GetString("METRICS_USERNAME"),
 		MetricsPassword: viper.GetString("METRICS_PASSWORD"),
 		SessionSecret:   viper.GetString("SESSION_SECRET"),
+		CORSOrigins:     viper.GetString("CORS_ORIGINS"),
 		params:          params,
 		log:             log,
 	}

internal/handlers/api.go

@@ -218,6 +218,15 @@ func (h *Handlers) HandleAPICreateApp() http.HandlerFunc {
 			return
 		}
 
+		repoURLErr := validateRepoURL(req.RepoURL)
+		if repoURLErr != nil {
+			h.respondJSON(writer, request,
+				map[string]string{"error": "invalid repository URL: " + repoURLErr.Error()},
+				http.StatusBadRequest)
+
+			return
+		}
+
 		createdApp, createErr := h.appService.CreateApp(request.Context(), app.CreateAppInput{
 			Name:           req.Name,
 			RepoURL:        req.RepoURL,

internal/handlers/app.go

@@ -77,6 +77,14 @@ func (h *Handlers) HandleAppCreate() http.HandlerFunc { //nolint:funlen // valid
 			return
 		}
 
+		repoURLErr := validateRepoURL(repoURL)
+		if repoURLErr != nil {
+			data["Error"] = "Invalid repository URL: " + repoURLErr.Error()
+			h.renderTemplate(writer, tmpl, "app_new.html", data)
+
+			return
+		}
+
 		if branch == "" {
 			branch = "main"
 		}
@@ -225,6 +233,17 @@ func (h *Handlers) HandleAppUpdate() http.HandlerFunc { //nolint:funlen // valid
 			return
 		}
 
+		repoURLErr := validateRepoURL(request.FormValue("repo_url"))
+		if repoURLErr != nil {
+			data := h.addGlobals(map[string]any{
+				"App":   application,
+				"Error": "Invalid repository URL: " + repoURLErr.Error(),
+			}, request)
+			_ = tmpl.ExecuteTemplate(writer, "app_edit.html", data)
+
+			return
+		}
+
 		application.Name = newName
 		application.RepoURL = request.FormValue("repo_url")
 		application.Branch = request.FormValue("branch")

internal/handlers/repo_url_validation.go

@@ -0,0 +1,67 @@
+package handlers
+
+import (
+	"errors"
+	"net/url"
+	"regexp"
+	"strings"
+)
+
+// Repo URL validation errors.
+var (
+	errRepoURLEmpty   = errors.New("repository URL must not be empty")
+	errRepoURLScheme  = errors.New("file:// URLs are not allowed for security reasons")
+	errRepoURLInvalid = errors.New("repository URL must use https://, http://, ssh://, git://, or git@host:path format")
+	errRepoURLNoHost  = errors.New("repository URL must include a host")
+	errRepoURLNoPath  = errors.New("repository URL must include a path")
+)
+
+// scpLikeRepoRe matches SCP-like git URLs: git@host:path (e.g. git@github.com:user/repo.git).
+// Only the "git" user is allowed, as that is the standard for SSH deploy keys.
+var scpLikeRepoRe = regexp.MustCompile(`^git@[a-zA-Z0-9._-]+:.+$`)
+
+// validateRepoURL checks that the given repository URL is valid and uses an allowed scheme.
+func validateRepoURL(repoURL string) error {
+	if strings.TrimSpace(repoURL) == "" {
+		return errRepoURLEmpty
+	}
+
+	// Reject path traversal in any URL format
+	if strings.Contains(repoURL, "..") {
+		return errRepoURLInvalid
+	}
+
+	// Check for SCP-like git URLs first (git@host:path)
+	if scpLikeRepoRe.MatchString(repoURL) {
+		return nil
+	}
+
+	// Reject file:// explicitly
+	if strings.HasPrefix(strings.ToLower(repoURL), "file://") {
+		return errRepoURLScheme
+	}
+
+	// Parse as standard URL
+	parsed, err := url.Parse(repoURL)
+	if err != nil {
+		return errRepoURLInvalid
+	}
+
+	// Must have a recognized scheme
+	switch strings.ToLower(parsed.Scheme) {
+	case "https", "http", "ssh", "git":
+		// OK
+	default:
+		return errRepoURLInvalid
+	}
+
+	if parsed.Host == "" {
+		return errRepoURLNoHost
+	}
+
+	if parsed.Path == "" || parsed.Path == "/" {
+		return errRepoURLNoPath
+	}
+
+	return nil
+}

internal/handlers/repo_url_validation_test.go

@@ -0,0 +1,56 @@
+package handlers
+
+import "testing"
+
+func TestValidateRepoURL(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		url     string
+		wantErr bool
+	}{
+		// Valid URLs
+		{name: "https URL", url: "https://github.com/user/repo.git", wantErr: false},
+		{name: "http URL", url: "http://github.com/user/repo.git", wantErr: false},
+		{name: "ssh URL", url: "ssh://git@github.com/user/repo.git", wantErr: false},
+		{name: "git URL", url: "git://github.com/user/repo.git", wantErr: false},
+		{name: "SCP-like URL", url: "git@github.com:user/repo.git", wantErr: false},
+		{name: "SCP-like with dots", url: "git@git.example.com:org/repo.git", wantErr: false},
+		{name: "https without .git", url: "https://github.com/user/repo", wantErr: false},
+		{name: "https with port", url: "https://git.example.com:8443/user/repo.git", wantErr: false},
+
+		// Invalid URLs
+		{name: "empty string", url: "", wantErr: true},
+		{name: "whitespace only", url: "   ", wantErr: true},
+		{name: "file URL", url: "file:///etc/passwd", wantErr: true},
+		{name: "file URL uppercase", url: "FILE:///etc/passwd", wantErr: true},
+		{name: "bare path", url: "/some/local/path", wantErr: true},
+		{name: "relative path", url: "../repo", wantErr: true},
+		{name: "just a word", url: "notaurl", wantErr: true},
+		{name: "ftp URL", url: "ftp://example.com/repo.git", wantErr: true},
+		{name: "no host https", url: "https:///path", wantErr: true},
+		{name: "no path https", url: "https://github.com", wantErr: true},
+		{name: "no path https trailing slash", url: "https://github.com/", wantErr: true},
+		{name: "SCP-like non-git user", url: "root@github.com:user/repo.git", wantErr: true},
+		{name: "SCP-like arbitrary user", url: "admin@github.com:user/repo.git", wantErr: true},
+		{name: "path traversal SCP", url: "git@github.com:../../etc/passwd", wantErr: true},
+		{name: "path traversal https", url: "https://github.com/user/../../../etc/passwd", wantErr: true},
+		{name: "path traversal in middle", url: "https://github.com/user/repo/../secret", wantErr: true},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			err := validateRepoURL(tc.url)
+			if tc.wantErr && err == nil {
+				t.Errorf("validateRepoURL(%q) = nil, want error", tc.url)
+			}
+
+			if !tc.wantErr && err != nil {
+				t.Errorf("validateRepoURL(%q) = %v, want nil", tc.url, err)
+			}
+		})
+	}
+}

internal/middleware/cors_test.go

@@ -0,0 +1,81 @@
+package middleware //nolint:testpackage // tests internal CORS behavior
+
+import (
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"git.eeqj.de/sneak/upaas/internal/config"
+)
+
+//nolint:gosec // test credentials
+func newCORSTestMiddleware(corsOrigins string) *Middleware {
+	return &Middleware{
+		log: slog.Default(),
+		params: &Params{
+			Config: &config.Config{
+				CORSOrigins:   corsOrigins,
+				SessionSecret: "test-secret-32-bytes-long-enough",
+			},
+		},
+	}
+}
+
+func TestCORS_NoOriginsConfigured_NoCORSHeaders(t *testing.T) {
+	t.Parallel()
+
+	m := newCORSTestMiddleware("")
+	handler := m.CORS()(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	req.Header.Set("Origin", "https://evil.com")
+
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	assert.Empty(t, rec.Header().Get("Access-Control-Allow-Origin"),
+		"expected no CORS headers when no origins configured")
+}
+
+func TestCORS_OriginsConfigured_AllowsMatchingOrigin(t *testing.T) {
+	t.Parallel()
+
+	m := newCORSTestMiddleware("https://app.example.com,https://other.example.com")
+	handler := m.CORS()(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	req.Header.Set("Origin", "https://app.example.com")
+
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	assert.Equal(t, "https://app.example.com",
+		rec.Header().Get("Access-Control-Allow-Origin"))
+	assert.Equal(t, "true",
+		rec.Header().Get("Access-Control-Allow-Credentials"))
+}
+
+func TestCORS_OriginsConfigured_RejectsNonMatchingOrigin(t *testing.T) {
+	t.Parallel()
+
+	m := newCORSTestMiddleware("https://app.example.com")
+	handler := m.CORS()(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	req.Header.Set("Origin", "https://evil.com")
+
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	assert.Empty(t, rec.Header().Get("Access-Control-Allow-Origin"),
+		"expected no CORS headers for non-matching origin")
+}

internal/middleware/middleware.go

@@ -177,17 +177,48 @@ func realIP(r *http.Request) string {
 }
 
 // CORS returns CORS middleware.
+// When UPAAS_CORS_ORIGINS is empty (default), no CORS headers are sent
+// (same-origin only). When configured, only the specified origins are
+// allowed and credentials (cookies) are permitted.
 func (m *Middleware) CORS() func(http.Handler) http.Handler {
+	origins := parseCORSOrigins(m.params.Config.CORSOrigins)
+
+	// No origins configured — no CORS headers (same-origin policy).
+	if len(origins) == 0 {
+		return func(next http.Handler) http.Handler {
+			return next
+		}
+	}
+
 	return cors.Handler(cors.Options{
-		AllowedOrigins:   []string{"*"},
+		AllowedOrigins:   origins,
 		AllowedMethods:   []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"},
 		AllowedHeaders:   []string{"Accept", "Authorization", "Content-Type", "X-CSRF-Token"},
 		ExposedHeaders:   []string{"Link"},
-		AllowCredentials: false,
+		AllowCredentials: true,
 		MaxAge:           corsMaxAge,
 	})
 }
 
+// parseCORSOrigins splits a comma-separated origin string into a slice,
+// trimming whitespace. Returns nil if the input is empty.
+func parseCORSOrigins(raw string) []string {
+	if raw == "" {
+		return nil
+	}
+
+	parts := strings.Split(raw, ",")
+	origins := make([]string, 0, len(parts))
+
+	for _, p := range parts {
+		if o := strings.TrimSpace(p); o != "" {
+			origins = append(origins, o)
+		}
+	}
+
+	return origins
+}
+
 // MetricsAuth returns basic auth middleware for metrics endpoint.
 func (m *Middleware) MetricsAuth() func(http.Handler) http.Handler {
 	if m.params.Config.MetricsUsername == "" {