Merge branch 'fix-little-issues' into minor

src/Common.cpp

@@ -384,10 +384,16 @@ void SplitString(const std::string& str, const char delim, std::vector<std::stri
         out.push_back(str.substr(start, end - start));
     }
 }
+static constexpr size_t STARTING_MAX_DECOMPRESSION_BUFFER_SIZE = 15 * 1024 * 1024;
+static constexpr size_t MAX_DECOMPRESSION_BUFFER_SIZE = 30 * 1024 * 1024;
+
 std::vector<uint8_t> DeComp(std::span<const uint8_t> input) {
     beammp_debugf("got {} bytes of input data", input.size());
 
-    std::vector<uint8_t> output_buffer(std::min<size_t>(input.size() * 5, 15 * 1024 * 1024));
+    // start with a decompression buffer of 5x the input size, clamped to a maximum of 15 MB.
+    // this buffer can and will grow, but we don't want to start it too large. A 5x compression ratio
+    // is pretty optimistic.
+    std::vector<uint8_t> output_buffer(std::min<size_t>(input.size() * 5, STARTING_MAX_DECOMPRESSION_BUFFER_SIZE));
 
     uLongf output_size = output_buffer.size();
 
@@ -398,11 +404,17 @@ std::vector<uint8_t> DeComp(std::span<const uint8_t> input) {
             reinterpret_cast<const Bytef*>(input.data()),
             static_cast<uLongf>(input.size()));
         if (res == Z_BUF_ERROR) {
-            if (output_buffer.size() > 30 * 1024 * 1024) {
-                throw std::runtime_error("decompressed packet size of 30 MB exceeded");
+            // We assume that a reasonable maximum size for decompressed packets exists. We want to avoid
+            // a client effectively "zip bombing" us by sending a lot of small packets which decompress
+            // into huge data.
+            // If this limit were to be an issue, this could be made configurable, however clients have a similar
+            // limit. For that reason, we just reject packets which decompress into too much data.
+            if (output_buffer.size() >= MAX_DECOMPRESSION_BUFFER_SIZE) {
+                throw std::runtime_error(fmt::format("decompressed packet size of {} bytes exceeded", MAX_DECOMPRESSION_BUFFER_SIZE));
             }
-            beammp_warn("zlib uncompress() failed, trying with 2x buffer size of " + std::to_string(output_buffer.size() * 2));
-            output_buffer.resize(output_buffer.size() * 2);
+            // if decompression fails, we double the buffer size (up to the allowed limit) and try again
+            output_buffer.resize(std::max<size_t>(output_buffer.size() * 2, MAX_DECOMPRESSION_BUFFER_SIZE));
+            beammp_warnf("zlib uncompress() failed, trying with a larger buffer size of {}", output_buffer.size());
             output_size = output_buffer.size();
         } else if (res != Z_OK) {
             beammp_error("zlib uncompress() failed: " + std::to_string(res));