iemejia commented on code in PR #3854: URL: https://github.com/apache/avro/pull/3854#discussion_r3564664115
########## lang/c++/impl/DataFile.cc: ########## @@ -55,6 +58,32 @@ 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); + // Reject a leading sign (strtoull would otherwise wrap it) and clamp to + // what size_t can represent so a huge value does not truncate on 32-bit + // (or smaller size_t) builds. + if (errno == 0 && end != nullptr && *end == '\0' && value > 0 && env[0] != '-') { + if (value > std::numeric_limits<size_t>::max()) { + return std::numeric_limits<size_t>::max(); + } + return static_cast<size_t>(value); + } + } + return defaultMaxDecompressLength; +} Review Comment: Fixed. `maxDecompressLength()` now skips leading whitespace before rejecting an explicit sign, so a value like `" -5"` is caught (strtoull accepts leading whitespace and would otherwise wrap the negative). Pushed in 710bbe2. ########## lang/c++/impl/DataFile.cc: ########## @@ -568,6 +597,18 @@ void DataFileReaderBase::readDataBlock() { int b4 = compressed_[len - 1] & 0xFF; checksum = (b1 << 24) + (b2 << 16) + (b3 << 8) + (b4); + { + // Reject an over-large block before allocating for it, based on the + // uncompressed length declared in the Snappy block header. + size_t declared = 0; + if (snappy::GetUncompressedLength(reinterpret_cast<const char *>(compressed_.data()), + len - 4, &declared) && + declared > maxDecompressLength()) { + throw Exception( + "Decompressed block size {} exceeds the maximum allowed of {} bytes", + declared, maxDecompressLength()); + } + } Review Comment: Fixed. The Snappy path now evaluates `maxDecompressLength()` once into a local and reuses it for both the check and the error message. Pushed in 710bbe2. ########## lang/c++/test/DecompressionLimitTests.cc: ########## @@ -0,0 +1,142 @@ +/* + * 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 + + // Let any writer exception propagate: a failure here is a real problem + // (e.g. permissions or I/O), not a reason to silently skip. Codecs that are + // not compiled in are excluded via the #ifdef guards on the callers below. + { + DataFileWriter<std::string> writer(path.c_str(), schema, 64 * 1024 * 1024, codec); + writer.write(big); + writer.close(); + } + + setDecompressLimit("1048576"); // 1 MiB, smaller than the 4 MiB block + + bool rejected = false; + try { + DataFileReader<std::string> reader(path.c_str(), schema); + std::string out; + reader.read(out); // triggers block decompression + } catch (const Exception &) { + rejected = true; + } + std::filesystem::remove(path); + BOOST_CHECK_MESSAGE(rejected, std::string("codec not bounded: ") + name); +} Review Comment: Fixed. Added a RAII `DecompressLimitGuard` that saves and restores `AVRO_MAX_DECOMPRESS_LENGTH` (unsetting it if it was previously unset), applied to every test that overrides it, so the override no longer leaks into other test cases. Pushed in 710bbe2. ########## lang/c++/test/DecompressionLimitTests.cc: ########## @@ -0,0 +1,142 @@ +/* + * 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 + + // Let any writer exception propagate: a failure here is a real problem + // (e.g. permissions or I/O), not a reason to silently skip. Codecs that are + // not compiled in are excluded via the #ifdef guards on the callers below. + { + DataFileWriter<std::string> writer(path.c_str(), schema, 64 * 1024 * 1024, codec); + writer.write(big); + writer.close(); + } + + setDecompressLimit("1048576"); // 1 MiB, smaller than the 4 MiB block + + bool rejected = false; + try { + DataFileReader<std::string> reader(path.c_str(), schema); + std::string out; + reader.read(out); // triggers block decompression + } catch (const Exception &) { + rejected = true; + } + std::filesystem::remove(path); + BOOST_CHECK_MESSAGE(rejected, std::string("codec not bounded: ") + name); +} + +static void testDeflateDecompressionLimit() { + checkCodecRejectsOversized(DEFLATE_CODEC, "avro_decompress_limit_deflate.avro"); +} + +static void testSnappyDecompressionLimit() { +#ifdef SNAPPY_CODEC_AVAILABLE + checkCodecRejectsOversized(SNAPPY_CODEC, "avro_decompress_limit_snappy.avro"); +#else + BOOST_TEST_MESSAGE("Snappy codec not available; skipping"); +#endif +} + +static void testZstdDecompressionLimit() { +#ifdef ZSTD_CODEC_AVAILABLE + checkCodecRejectsOversized(ZSTD_CODEC, "avro_decompress_limit_zstd.avro"); +#else + BOOST_TEST_MESSAGE("Zstandard codec not available; skipping"); +#endif +} + +static void testWithinLimitStillReads() { + ValidSchema schema = stringSchema(); + std::string path = tempFile("avro_decompress_within_limit.avro"); + std::string payload = "hello world"; + + { + DataFileWriter<std::string> writer(path.c_str(), schema, 64 * 1024 * 1024, DEFLATE_CODEC); + writer.write(payload); + writer.close(); + } + + setDecompressLimit("1048576"); + + std::string out; + { + DataFileReader<std::string> reader(path.c_str(), schema); + BOOST_CHECK(reader.read(out)); + } Review Comment: Same RAII guard applied here so this test restores the previous `AVRO_MAX_DECOMPRESS_LENGTH` value on exit. 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