Copilot commented on code in PR #3854: URL: https://github.com/apache/avro/pull/3854#discussion_r3564409486
########## lang/c++/test/DecompressionLimitTests.cc: ########## @@ -0,0 +1,135 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * https://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +// AVRO-4285: a data-file block is decompressed according to the file's codec. A +// block with a very high compression ratio (or a malformed block) can expand to +// far more memory than its compressed size. Reading such a block must be +// rejected once its decompressed size would exceed the configured maximum, which +// these tests set to a small value via AVRO_MAX_DECOMPRESS_LENGTH. + +#include <cstdlib> +#include <filesystem> +#include <sstream> +#include <string> + +#include <boost/test/included/unit_test.hpp> + +#include "Compiler.hh" +#include "DataFile.hh" +#include "Exception.hh" +#include "ValidSchema.hh" + +namespace avro { + +static void setDecompressLimit(const char *value) { +#ifdef _WIN32 + _putenv_s("AVRO_MAX_DECOMPRESS_LENGTH", value); +#else + setenv("AVRO_MAX_DECOMPRESS_LENGTH", value, 1); +#endif +} + +static ValidSchema stringSchema() { + std::istringstream iss("\"string\""); + ValidSchema vs; + compileJsonSchema(iss, vs); + return vs; +} + +static std::string tempFile(const char *name) { + return (std::filesystem::temp_directory_path() / name).string(); +} + +// Write a single, highly compressible value with the given codec, then read it +// back with a small decompression limit and confirm the read is rejected. +static void checkCodecRejectsOversized(Codec codec, const char *name) { + ValidSchema schema = stringSchema(); + std::string path = tempFile(name); + std::string big(4 * 1024 * 1024, 'a'); // 4 MiB, compresses tiny + + try { + DataFileWriter<std::string> writer(path.c_str(), schema, 64 * 1024 * 1024, codec); + writer.write(big); + writer.close(); + } catch (const Exception &) { + // Codec not available in this build; nothing to exercise. + std::filesystem::remove(path); + return; + } Review Comment: `checkCodecRejectsOversized()` treats *any* `avro::Exception` thrown during file creation/writing as “codec not available” and silently skips the test. This can mask real failures (e.g., temp directory permissions, I/O errors, or other writer exceptions). Prefer explicitly checking `isCodecAvailable(codec)` and letting other exceptions fail the test. ########## lang/c++/impl/DataFile.cc: ########## @@ -55,6 +56,26 @@ const size_t maxSyncInterval = 1u << 30; // Recommended by https://www.zlib.net/zlib_how.html const size_t zlibBufGrowSize = 128 * 1024; +// Default upper bound, in bytes, on the size a single data-file block may +// decompress to. A block with a very high compression ratio (or a malformed +// block) can otherwise expand to far more memory than its compressed size. +// Mirrors the Java SDK's decompression limit (AVRO-4247). Overridable with the +// AVRO_MAX_DECOMPRESS_LENGTH environment variable. +const size_t defaultMaxDecompressLength = static_cast<size_t>(200) * 1024 * 1024; // 200 MiB + +size_t maxDecompressLength() { + const char *env = std::getenv("AVRO_MAX_DECOMPRESS_LENGTH"); + if (env != nullptr && *env != '\0') { + errno = 0; + char *end = nullptr; + unsigned long long value = std::strtoull(env, &end, 10); + if (errno == 0 && end != nullptr && *end == '\0' && value > 0) { + return static_cast<size_t>(value); + } + } + return defaultMaxDecompressLength; +} Review Comment: `maxDecompressLength()` accepts any `strtoull` value that parses cleanly, but does not guard against values larger than `std::numeric_limits<size_t>::max()`. On 32-bit (or smaller `size_t`) builds this will silently truncate, producing an unexpected limit value. ########## lang/c++/impl/ZstdDecompressWrapper.cc: ########## @@ -44,8 +44,19 @@ std::string ZstdDecompressWrapper::decompress(const std::vector<char> &compresse throw Exception("ZSTD decompression error: {}", ZSTD_getErrorName(ret)); } uncompressed.append(tmp.data(), out.pos); + // Reject a block that decompresses to more than the allowed maximum. + if (uncompressed.size() > maxLength) { + throw Exception( + "Decompressed block size exceeds the maximum allowed of {} bytes", maxLength); + } Review Comment: In the streaming (unknown content size) Zstandard path, the code appends to `uncompressed` and only then checks whether the maximum was exceeded. This can temporarily grow `uncompressed` past the configured limit (and potentially trigger larger reallocations) before throwing. ########## lang/c++/impl/DataFile.cc: ########## @@ -18,6 +18,7 @@ #include "DataFile.hh" #include "Compiler.hh" +#include <cstdlib> #include <cstring> #include "Exception.hh" Review Comment: `maxDecompressLength()` uses `errno` (and the fix below also uses `std::numeric_limits`), but this file does not include the corresponding standard headers. This can fail to compile depending on platform/libc++ headers. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
