fix: Introduce bounded demangling in an attempt to fix unbounded memo…

…ry growth (#481)

symbolic-demangle/src/lib.rs

@@ -204,6 +204,33 @@ fn strip_hash_suffix(ident: &str) -> &str {
     ident
 }
 
+struct BoundedString {
+    str: String,
+    bound: usize,
+}
+
+impl BoundedString {
+    fn new(bound: usize) -> Self {
+        Self {
+            str: String::new(),
+            bound,
+        }
+    }
+
+    pub fn into_inner(self) -> String {
+        self.str
+    }
+}
+
+impl std::fmt::Write for BoundedString {
+    fn write_str(&mut self, s: &str) -> std::fmt::Result {
+        if self.str.len().saturating_add(s.len()) > self.bound {
+            return Err(std::fmt::Error);
+        }
+        self.str.write_str(s)
+    }
+}
+
 fn try_demangle_cpp(ident: &str, opts: DemangleOptions) -> Option<String> {
     if is_maybe_msvc(ident) {
         return try_demangle_msvc(ident, opts);
@@ -231,10 +258,14 @@ fn try_demangle_cpp(ident: &str, opts: DemangleOptions) -> Option<String> {
             cpp_options = cpp_options.no_return_type();
         }
 
-        match symbol.demangle(&cpp_options) {
-            Ok(demangled) => Some(demangled),
-            Err(_) => None,
-        }
+        // Bound the maximum output string, as a huge number of substitutions could potentially
+        // lead to a "Billion laughs attack".
+        let mut buf = BoundedString::new(4096);
+
+        symbol
+            .structured_demangle(&mut buf, &cpp_options)
+            .ok()
+            .map(|_| buf.into_inner())
     }
     #[cfg(not(feature = "cpp"))]
     {

symbolic-demangle/tests/test_cpp.rs

@@ -59,3 +59,14 @@ fn test_deep_recursion() {
     "boost::variant<int, long long, unsigned int, double, bool, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::basic_string_view<char, std::char_traits<char> >, long, unsigned long, long long, unsigned long long, boost::filesystem::path>::assigner::result_type boost::detail::variant::visitation_impl<mpl_::int_<0>, boost::detail::variant::visitation_impl_step<boost::mpl::l_iter<boost::mpl::l_item<mpl_::long_<(long)12>, int, boost::mpl::l_item<mpl_::long_<(long)11>, long long, boost::mpl::l_item<mpl_::long_<(long)10>, unsigned int, boost::mpl::l_item<mpl_::long_<(long)9>, double, boost::mpl::l_item<mpl_::long_<(long)8>, bool, boost::mpl::l_item<mpl_::long_<(long)7>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::mpl::l_item<mpl_::long_<(long)6>, boost::basic_string_view<char, std::char_traits<char> >, boost::mpl::l_item<mpl_::long_<(long)5>, long, boost::mpl::l_item<mpl_::long_<(long)4>, unsigned long, boost::mpl::l_item<mpl_::long_<(long)3>, long long, boost::mpl::l_item<mpl_::long_<(long)2>, unsigned long long, boost::mpl::l_item<mpl_::long_<(long)1>, boost::filesystem::path, boost::mpl::l_end> > > > > > > > > > > > >, boost::mpl::l_iter<boost::mpl::l_end> >, boost::variant<int, long long, unsigned int, double, bool, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::basic_string_view<char, std::char_traits<char> >, long, unsigned long, long long, unsigned long long, boost::filesystem::path>::assigner, void const*, boost::variant<int, long long, unsigned int, double, bool, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::basic_string_view<char, std::char_traits<char> >, long, unsigned long, long long, unsigned long long, boost::filesystem::path>::has_fallback_type_>(int, int, boost::variant<int, long long, unsigned int, double, bool, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::basic_string_view<char, std::char_traits<char> >, long, unsigned long, long long, unsigned long long, boost::filesystem::path>::assigner&, void const*, mpl_::bool_<false>, boost::variant<int, long long, unsigned int, double, bool, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::basic_string_view<char, std::char_traits<char> >, long, unsigned long, long long, unsigned long long, boost::filesystem::path>::has_fallback_type_, mpl_::int_<0>*, boost::detail::variant::visitation_impl_step<boost::mpl::l_iter<boost::mpl::l_item<mpl_::long_<(long)12>, int, boost::mpl::l_item<mpl_::long_<(long)11>, long long, boost::mpl::l_item<mpl_::long_<(long)10>, unsigned int, boost::mpl::l_item<mpl_::long_<(long)9>, double, boost::mpl::l_item<mpl_::long_<(long)8>, bool, boost::mpl::l_item<mpl_::long_<(long)7>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::mpl::l_item<mpl_::long_<(long)6>, boost::basic_string_view<char, std::char_traits<char> >, boost::mpl::l_item<mpl_::long_<(long)5>, long, boost::mpl::l_item<mpl_::long_<(long)4>, unsigned long, boost::mpl::l_item<mpl_::long_<(long)3>, long long, boost::mpl::l_item<mpl_::long_<(long)2>, unsigned long long, boost::mpl::l_item<mpl_::long_<(long)1>, boost::filesystem::path, boost::mpl::l_end> > > > > > > > > > > > >, boost::mpl::l_iter<boost::mpl::l_end> >*)"
     });
 }
+
+// See https://github.com/getsentry/symbolic/issues/477
+// Not fully fixed, so skip for now :-(
+// #[test]
+// fn test_bounded_buf() {
+//     let s = "_ZUlzjjlZZL1zStUlSt7j_Z3kjIIjIjL1vfIIEEEjzjjfjzSt7j_Z3kjIIjfjzL4t3kjIIjfjtUlSt7j_Z3kjIIjIjL1vfIIEEEjzjjfjzSt7j_Z3kjIIjfjzL4t3kjIIjfjzL4t7IjIjjzjjzSt7j_Z3kjIIjfjzStfjzSt7j_ZA3kjIIjIjL1vfIIEEEjzjjfjzSt7j_Z3kjIIjIjL1vfIIEEEjzjjfjzSt7j_Z3kjIIjfjzL4t3kjIIjzL4t7IjIjjzjjzSt7j_Z3kjIIjfjzStfjzSt7j_ZA3kjIIjIjL1vfIIEEEjzjjfjzSt7j_Z3kjIIjIjL1vfIIEEEjzjjfjzSt7j_Z3kjIIjfjzL4t3kjIIjfjzL4t7IjIjL1vfIIEEEjzjjSI";
+//     assert_eq!(
+//         symbolic_demangle::demangle(s),
+//         std::borrow::Cow::Borrowed(s)
+//     );
+// }