SERVER-115508 Make minimally sized buffers for uncompressed Messages

nadeaudi · bui-andrew · commit 505b660a1469 · 2025-12-22T14:53:00.000-08:00
diff --git a/src/mongo/transport/message_compressor_manager_test.cpp b/src/mongo/transport/message_compressor_manager_test.cpp
@@ -167,6 +167,26 @@ void checkOverflow(std::unique_ptr<MessageCompressorBase> compressor) {
         compressor->decompressData(tooSmallRange, DataRange(scratch.data(), scratch.size())));
 }
 
+void checkUndersize(const Message& compressedMsg,
+                    std::unique_ptr<MessageCompressorBase> compressor) {
+    MessageCompressorRegistry registry;
+    const auto compressorName = compressor->getName();
+
+    std::vector<std::string> compressorList = {compressorName};
+    registry.setSupportedCompressors(std::move(compressorList));
+    registry.registerImplementation(std::move(compressor));
+    registry.finalizeSupportedCompressors().transitional_ignore();
+
+    MessageCompressorManager mgr(&registry);
+    BSONObjBuilder negotiatorOut;
+    auto negotiator = BSON("isMaster" << 1 << "compression" << BSON_ARRAY(compressorName));
+    mgr.serverNegotiate(negotiator, &negotiatorOut);
+    checkNegotiationResult(negotiatorOut.done(), {compressorName});
+
+    auto swm = mgr.decompressMessage(compressedMsg);
+    ASSERT_EQ(ErrorCodes::BadValue, swm.getStatus());
+}
+
 Message buildMessage() {
     const auto data = std::string{"Hello, world!"};
     const auto bufferSize = MsgData::MsgDataHeaderSize + data.size();
@@ -252,6 +272,52 @@ TEST(ZstdMessageCompressor, Overflow) {
     checkOverflow(std::make_unique<ZstdMessageCompressor>());
 }
 
+TEST(ZlibMessageCompressor, Mismatch) {
+    checkOverflow(std::make_unique<ZlibMessageCompressor>());
+}
+
+TEST(SnappyMessageCompressor, Undersize) {
+    std::vector<std::uint8_t> payload = {
+        0x41, 0x0, 0x0,  0x0,  0xad, 0xde, 0x0,  0x0,  0x0,  0x0,  0x0,  0x0,  0xdc,
+        0x7,  0x0, 0x0,  0xdd, 0x7,  0x0,  0x0,  0x0,  0x20, 0x0,  0x0,  0x1,  0x27,
+        0x0,  0x0, 0x1,  0x1,  0x84, 0xfb, 0x1f, 0x0,  0x0,  0x5,  0x5f, 0x69, 0x64,
+        0x0,  0x0, 0x10, 0x0,  0x0,  0x0,  0x48, 0x45, 0x41, 0x50, 0x4c, 0x45, 0x41,
+        0x4b, 0x0, 0x0,  0x0,  0x0,  0x0,  0x0,  0x0,  0x0,  0x0,  0x0,  0x0,  0x0};
+
+
+    auto buffer = SharedBuffer::allocate(payload.size());
+    std::copy(payload.begin(), payload.end(), buffer.get());
+
+    checkUndersize(Message(buffer), std::make_unique<SnappyMessageCompressor>());
+}
+
+TEST(ZlibMessageCompressor, Undersize) {
+    std::vector<std::uint8_t> payload = {
+        0x3c, 0x00, 0x00, 0x00, 0xad, 0xde, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xdc, 0x07, 0x00,
+        0x00, 0xdd, 0x07, 0x00, 0x00, 0x00, 0x20, 0x00, 0x00, 0x02, 0x78, 0xda, 0x63, 0x60, 0x00,
+        0x82, 0xdf, 0xf2, 0x0c, 0x0c, 0xac, 0xf1, 0x99, 0x29, 0x0c, 0x0c, 0x02, 0x40, 0x9e, 0x87,
+        0xab, 0x63, 0x80, 0x8f, 0xab, 0xa3, 0x37, 0x03, 0x12, 0x00, 0x00, 0x6d, 0x26, 0x04, 0x97};
+
+    auto buffer = SharedBuffer::allocate(payload.size());
+    std::copy(payload.begin(), payload.end(), buffer.get());
+
+    checkUndersize(Message(buffer), std::make_unique<ZlibMessageCompressor>());
+}
+
+TEST(ZstdMessageCompressor, Undersize) {
+    std::vector<std::uint8_t> payload = {
+        0x44, 0x0,  0x0,  0x0,  0xad, 0xde, 0x0,  0x0,  0x0,  0x0,  0x0,  0x0,  0xdc, 0x7,
+        0x0,  0x0,  0xdd, 0x7,  0x0,  0x0,  0x0,  0x20, 0x0,  0x0,  0x3,  0x28, 0xb5, 0x2f,
+        0xfd, 0x20, 0x27, 0x15, 0x1,  0x0,  0xe0, 0x0,  0x0,  0x0,  0x0,  0x0,  0xfb, 0x1f,
+        0x0,  0x0,  0x5,  0x5f, 0x69, 0x64, 0x0,  0x0,  0x10, 0x0,  0x0,  0x0,  0x48, 0x45,
+        0x41, 0x50, 0x4c, 0x45, 0x41, 0x4b, 0x0,  0x1,  0x0,  0x18, 0xc0, 0x9};
+
+    auto buffer = SharedBuffer::allocate(payload.size());
+    std::copy(payload.begin(), payload.end(), buffer.get());
+
+    checkUndersize(Message(buffer), std::make_unique<ZstdMessageCompressor>());
+}
+
 TEST(MessageCompressorManager, SERVER_28008) {
 
     // Create a client and server that will negotiate the same compressors,
diff --git a/src/mongo/transport/message_compressor_zlib.cpp b/src/mongo/transport/message_compressor_zlib.cpp
@@ -74,7 +74,7 @@ StatusWith<std::size_t> ZlibMessageCompressor::decompressData(ConstDataRange inp
     }
 
     counterHitDecompress(input.length(), output.length());
-    return {output.length()};
+    return length;
 }
 
 

Original file line number	Diff line number	Diff line change
`@@ -74,7 +74,7 @@ StatusWith<std::size_t> ZlibMessageCompressor::decompressData(ConstDataRange inp`
`74`	`74`	`}`
`75`	`75`
`76`	`76`	`counterHitDecompress(input.length(), output.length());`
`77`		`- return {output.length()};`
	`77`	`+ return length;`
`78`	`78`	`}`
`79`	`79`
`80`	`80`