🐛 fix for #962

include/nlohmann/detail/exceptions.hpp

@@ -263,6 +263,7 @@ json.exception.out_of_range.404 | unresolved reference token 'foo' | A reference
 json.exception.out_of_range.405 | JSON pointer has no parent | The JSON Patch operations 'remove' and 'add' can not be applied to the root element of the JSON value.
 json.exception.out_of_range.406 | number overflow parsing '10E1000' | A parsed number could not be stored as without changing it to NaN or INF.
 json.exception.out_of_range.407 | number overflow serializing '9223372036854775808' | UBJSON only supports integers numbers up to 9223372036854775807. |
+json.exception.out_of_range.408 | excessive array size: 8658170730974374167 | The size (following `#`) of an UBJSON array or object exceeds the maximal capacity. |
 
 @liveexample{The following code shows how an `out_of_range` exception can be
 caught.,out_of_range}

include/nlohmann/detail/input/binary_reader.hpp

@@ -1246,14 +1246,22 @@ class binary_reader
 
         if (size_and_type.first != string_t::npos)
         {
+            if (JSON_UNLIKELY(size_and_type.first > result.max_size()))
+            {
+                JSON_THROW(out_of_range::create(408,
+                                                "excessive array size: " + std::to_string(size_and_type.first)));
+            }
+
             if (size_and_type.second != 0)
             {
                 if (size_and_type.second != 'N')
+                {
                     std::generate_n(std::back_inserter(*result.m_value.array),
                                     size_and_type.first, [this, size_and_type]()
-                {
-                    return get_ubjson_value(size_and_type.second);
-                });
+                    {
+                        return get_ubjson_value(size_and_type.second);
+                    });
+                }
             }
             else
             {
@@ -1283,6 +1291,12 @@ class binary_reader
 
         if (size_and_type.first != string_t::npos)
         {
+            if (JSON_UNLIKELY(size_and_type.first > result.max_size()))
+            {
+                JSON_THROW(out_of_range::create(408,
+                                                "excessive object size: " + std::to_string(size_and_type.first)));
+            }
+
             if (size_and_type.second != 0)
             {
                 std::generate_n(std::inserter(*result.m_value.object,

single_include/nlohmann/json.hpp

@@ -756,6 +756,7 @@ json.exception.out_of_range.404 | unresolved reference token 'foo' | A reference
 json.exception.out_of_range.405 | JSON pointer has no parent | The JSON Patch operations 'remove' and 'add' can not be applied to the root element of the JSON value.
 json.exception.out_of_range.406 | number overflow parsing '10E1000' | A parsed number could not be stored as without changing it to NaN or INF.
 json.exception.out_of_range.407 | number overflow serializing '9223372036854775808' | UBJSON only supports integers numbers up to 9223372036854775807. |
+json.exception.out_of_range.408 | excessive array size: 8658170730974374167 | The size (following `#`) of an UBJSON array or object exceeds the maximal capacity. |
 
 @liveexample{The following code shows how an `out_of_range` exception can be
 caught.,out_of_range}
@@ -6066,14 +6067,22 @@ class binary_reader
 
         if (size_and_type.first != string_t::npos)
         {
+            if (JSON_UNLIKELY(size_and_type.first > result.max_size()))
+            {
+                JSON_THROW(out_of_range::create(408,
+                                                "excessive array size: " + std::to_string(size_and_type.first)));
+            }
+
             if (size_and_type.second != 0)
             {
                 if (size_and_type.second != 'N')
+                {
                     std::generate_n(std::back_inserter(*result.m_value.array),
                                     size_and_type.first, [this, size_and_type]()
-                {
-                    return get_ubjson_value(size_and_type.second);
-                });
+                    {
+                        return get_ubjson_value(size_and_type.second);
+                    });
+                }
             }
             else
             {
@@ -6103,6 +6112,12 @@ class binary_reader
 
         if (size_and_type.first != string_t::npos)
         {
+            if (JSON_UNLIKELY(size_and_type.first > result.max_size()))
+            {
+                JSON_THROW(out_of_range::create(408,
+                                                "excessive object size: " + std::to_string(size_and_type.first)));
+            }
+
             if (size_and_type.second != 0)
             {
                 std::generate_n(std::inserter(*result.m_value.object,

test/src/fuzzer-parse_ubjson.cpp

@@ -58,6 +58,10 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // type errors can occur during parsing, too
     }
+    catch (const json::out_of_range&)
+    {
+        // out of range errors may happen if provided sizes are excessive
+    }
 
     // return 0 - non-zero return values are reserved for future use
     return 0;

test/src/unit-regression.cpp

@@ -1423,4 +1423,17 @@ TEST_CASE("regression tests")
         json j = json::from_cbor(v_cbor);
         CHECK(j == "abcd123");
     }
+
+    SECTION("issue #962 - Timeout (OSS-Fuzz 6034)")
+    {
+        std::vector<uint8_t> v_ubjson = {0x5b, 0x24, 0x5a, 0x23, 0x4c, 0x78, 0x28, 0x00, 0x68, 0x28, 0x69, 0x69, 0x17};
+        CHECK_THROWS_AS(json::from_ubjson(v_ubjson), json::out_of_range&);
+        CHECK_THROWS_WITH(json::from_ubjson(v_ubjson),
+                          "[json.exception.out_of_range.408] excessive array size: 8658170730974374167");
+
+        v_ubjson[0] = '{';
+        CHECK_THROWS_AS(json::from_ubjson(v_ubjson), json::out_of_range&);
+        CHECK_THROWS_WITH(json::from_ubjson(v_ubjson),
+                          "[json.exception.out_of_range.408] excessive object size: 8658170730974374167");
+    }
 }