Emit: fix possible stack-overflow by adding maxdepth; add append

changelog/current.md

@@ -3,9 +3,18 @@ Most of the changes are from the giant Parser refactor described below. Before g
 
 ### Fixes
 
-- Fix `_RYML_CB_ALLOC()` using `T` in parenthesis, making the macro unusable.
+- [#PR431](https://github.com/biojppm/rapidyaml/pull/431) - Emitter: prevent stack overflows when emitting malicious trees by providing a max tree depth for the emit visitor. This was done by adding an `EmitOptions` structure as an argument both to the emitter and to the emit functions, which is then forwarded to the emitter. This `EmitOptions` structure has a max tree depth setting with a default value of 64.
+- [#PR431](https://github.com/biojppm/rapidyaml/pull/431) - Fix `_RYML_CB_ALLOC()` using `(T)` in parenthesis, making the macro unusable.
 
 
+### New features
+
+- [#PR431](https://github.com/biojppm/rapidyaml/pull/431) - append-emitting to the `emitrs_` functions, suggested in [#345](https://github.com/biojppm/rapidyaml/issues/345). This was achieved by adding a `bool append=false` as the last parameter of these functions.
+
+
+------
+All other changes come from [#PR414](https://github.com/biojppm/rapidyaml/pull/414).
+
 ### Parser refactor
 
 The parser was completely refactored ([#PR414](https://github.com/biojppm/rapidyaml/pull/414)). This was a large and hard job carried out over several months, but it brings important improvements.

src/c4/yml/emit.def.hpp

@@ -36,21 +36,6 @@ substr Emitter<Writer>::emit_as(EmitType_e type, Tree const& t, id_type id, bool
     return this->Writer::_get(error_on_excess);
 }
 
-template<class Writer>
-substr Emitter<Writer>::emit_as(EmitType_e type, Tree const& t, bool error_on_excess)
-{
-    if(t.empty())
-        return {};
-    return this->emit_as(type, t, t.root_id(), error_on_excess);
-}
-
-template<class Writer>
-substr Emitter<Writer>::emit_as(EmitType_e type, ConstNodeRef const& n, bool error_on_excess)
-{
-    _RYML_CB_CHECK(n.tree()->callbacks(), n.readable());
-    return this->emit_as(type, *n.tree(), n.id(), error_on_excess);
-}
-
 
 //-----------------------------------------------------------------------------
 
@@ -263,6 +248,8 @@ void Emitter<Writer>::_do_visit_flow_sl(id_type node, id_type ilevel)
     RYML_ASSERT(!m_tree->is_stream(node));
     RYML_ASSERT(m_tree->is_container(node) || m_tree->is_doc(node));
     RYML_ASSERT(m_tree->is_root(node) || (m_tree->parent_is_map(node) || m_tree->parent_is_seq(node)));
+    if(C4_UNLIKELY(ilevel > m_opts.max_depth()))
+        _RYML_CB_ERR(m_tree->callbacks(), "max depth exceeded");
 
     if(m_tree->is_doc(node))
     {
@@ -368,6 +355,8 @@ void Emitter<Writer>::_do_visit_flow_ml(id_type id, id_type ilevel, id_type do_i
     C4_UNUSED(id);
     C4_UNUSED(ilevel);
     C4_UNUSED(do_indent);
+    if(C4_UNLIKELY(ilevel > m_opts.max_depth()))
+        _RYML_CB_ERR(m_tree->callbacks(), "max depth exceeded");
     const bool prev_flow = m_flow;
     m_flow = true;
     c4::yml::error("not implemented");
@@ -461,6 +450,8 @@ void Emitter<Writer>::_do_visit_block(id_type node, id_type ilevel, id_type do_i
     RYML_ASSERT(!m_tree->is_stream(node));
     RYML_ASSERT(m_tree->is_container(node) || m_tree->is_doc(node));
     RYML_ASSERT(m_tree->is_root(node) || (m_tree->parent_is_map(node) || m_tree->parent_is_seq(node)));
+    if(C4_UNLIKELY(ilevel > m_opts.max_depth()))
+        _RYML_CB_ERR(m_tree->callbacks(), "max depth exceeded");
     if(m_tree->is_doc(node))
     {
         _write_doc(node);