fix(provisioner): skip symlinks in collectCPConfigFiles (OFFSEC-010)

OFFSEC-010: filepath.WalkDir descends into symlinks by default. A
malicious template could contain `ln -s /etc/passwd snapshot`, and
WalkDir would traverse it — the existing `../`/absolute-path guards in
addFile don't catch symlinks because the symlink path itself contains
no ".." or leading "/".

Fix: check d.Type()&os.ModeSymlink in the WalkDir callback and return
nil to skip symlinks before they are descended. d.Type() is a zero-cost
DirEntry attribute (no extra syscall).

Also add TestCollectCPConfigFiles_SkipsSymlinks regression test.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workspace-server/internal/provisioner/cp_provisioner.go

@@ -269,6 +269,14 @@ func collectCPConfigFiles(cfg WorkspaceConfig) (map[string]string, error) {
 			if walkErr != nil {
 				return walkErr
 			}
+			// OFFSEC-010: skip symlinks — WalkDir descends into them by default,
+			// and a malicious template could symlink to sensitive files outside
+			// the intended template root (e.g. /etc/passwd).  The path checks
+			// in addFile guard against ../-escaped paths, but symlinks can
+			// cross the root without any ".." component, so we must skip them.
+			if d.Type()&os.ModeSymlink != 0 {
+				return nil
+			}
 			if d.IsDir() {
 				return nil
 			}

workspace-server/internal/provisioner/cp_provisioner_test.go

@@ -263,6 +263,57 @@ func TestStart_SendsTemplateAndGeneratedConfigFiles(t *testing.T) {
 	}
 }
 
+// TestCollectCPConfigFiles_SkipsSymlinks verifies OFFSEC-010: WalkDir descends
+// into symlinks by default, but we skip them so a template containing
+// ln -s /etc/passwd myapp/snapshot cannot exfiltrate files outside the root.
+func TestCollectCPConfigFiles_SkipsSymlinks(t *testing.T) {
+	tmpl := t.TempDir()
+	// Regular file inside the template — should be included.
+	if err := os.WriteFile(filepath.Join(tmpl, "config.yaml"), []byte("name: template\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	// Symlink pointing outside the template root — must NOT be followed.
+	sensitive := t.TempDir()
+	sensitiveFile := filepath.Join(sensitive, "secret.txt")
+	if err := os.WriteFile(sensitiveFile, []byte("ssh keys!"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Symlink(sensitiveFile, filepath.Join(tmpl, "snapshot")); err != nil {
+		t.Fatal(err)
+	}
+
+	var body cpProvisionRequest
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+			t.Errorf("decode request: %v", err)
+		}
+		w.WriteHeader(http.StatusCreated)
+		_, _ = io.WriteString(w, `{"instance_id":"i-abc123","state":"pending"}`)
+	}))
+	defer srv.Close()
+
+	p := &CPProvisioner{baseURL: srv.URL, orgID: "org-1", httpClient: srv.Client()}
+	_, err := p.Start(context.Background(), WorkspaceConfig{
+		WorkspaceID:  "ws-1",
+		Runtime:      "claude-code",
+		Tier:         4,
+		PlatformURL:  "http://tenant",
+		TemplatePath: tmpl,
+	})
+	if err != nil {
+		t.Fatalf("Start: %v", err)
+	}
+
+	// Only the regular file should be included; the symlink target must not appear.
+	wantConfig := base64.StdEncoding.EncodeToString([]byte("name: template\n"))
+	if got := body.ConfigFiles["config.yaml"]; got != wantConfig {
+		t.Errorf("config.yaml payload = %q, want %q", got, wantConfig)
+	}
+	if _, ok := body.ConfigFiles["snapshot"]; ok {
+		t.Error("snapshot symlink should not appear in config_files (OFFSEC-010)")
+	}
+}
+
 // TestStart_Non201ReturnsStructuredError — when CP returns 401 with a
 // structured {"error":"..."} body, Start surfaces that error message.
 // Verifies the defense against log-leaking raw upstream bodies.