fix: harden SSH trust and dependency security

internal/vncclient/vncclient_test.go

@@ -0,0 +1,26 @@
+package vncclient
+
+import "testing"
+
+func TestNewProxyTokenIsRandomHex(t *testing.T) {
+	first, err := newProxyToken()
+	if err != nil {
+		t.Fatalf("newProxyToken() error = %v", err)
+	}
+	second, err := newProxyToken()
+	if err != nil {
+		t.Fatalf("newProxyToken() second error = %v", err)
+	}
+
+	if len(first) != 32 {
+		t.Fatalf("token length = %d, want 32", len(first))
+	}
+	if first == second {
+		t.Fatal("expected separate tokens to differ")
+	}
+	for _, ch := range first {
+		if !((ch >= '0' && ch <= '9') || (ch >= 'a' && ch <= 'f')) {
+			t.Fatalf("token contains non-hex character %q", ch)
+		}
+	}
+}