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MINOR: [C++][Parquet] Reject too-short statistics values in FormatStatValue #50025

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MINOR: [C++][Parquet] Reject too-short statistics values in FormatStatValue #50025

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5c73eed
reject too-short statistics values in FormatStatValue
jmestwa-coder May 23, 2026
4897dee
Group BYTE_ARRAY with skipped types in stat length guard
jmestwa-coder May 26, 2026
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37 changes: 37 additions & 0 deletions cpp/src/parquet/types.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -184,6 +184,43 @@ std::string FormatFloat16Value(::std::string_view val) {

std::string FormatStatValue(Type::type parquet_type, ::std::string_view val,
const std::shared_ptr<const LogicalType>& logical_type) {
// Statistics blobs come from the file's Thrift-encoded metadata and may have
// arbitrary length under a malicious writer. Reject any value that is shorter
// than what the physical (and, for FLOAT16, logical) type requires so the
// memcpy/byte loads below cannot run past the buffer.
size_t required = 0;
switch (parquet_type) {
case Type::BOOLEAN:
required = sizeof(bool);
break;
case Type::INT32:
case Type::FLOAT:
required = 4;
break;
case Type::INT64:
case Type::DOUBLE:
required = 8;
break;
case Type::INT96:
required = 3 * sizeof(int32_t);
break;
case Type::FIXED_LEN_BYTE_ARRAY:
if (logical_type != nullptr && logical_type->is_float16()) {
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@wgtmac wgtmac May 24, 2026

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Why not dealing with the length of FIXED_LEN_BYTE_ARRAY?

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@jmestwa-coder jmestwa-coder May 26, 2026

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FormatStatValue doesn't receive the column's type_length, so it can't validate the full FLBA width here. The only fixed-size read for FLBA is the 2-byte float16 load, which is what this case guards. The decimal, string and hex paths all key off val.size() and stay in bounds.

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@wgtmac wgtmac May 27, 2026

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I admit that it is better than nothing to check types with known sizes. It still looks confusing with this partial support. If we do want to add the check, I think we need to support all types. We can either pass the type instance instead of only the enum or pass the type length to FormatStatValue. The challenge is that FormatStatValue is a public API so we cannot changing its signature without breaking backward compatibility.

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@wgtmac wgtmac May 27, 2026

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BTW, we need to create an issue for changes like this.

required = 2;
}
break;
case Type::BYTE_ARRAY:
case Type::UNDEFINED:
default:
break;
}
if (val.size() < required) {
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@wgtmac wgtmac May 24, 2026

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I'm a little hesitant to complicate FormatStatValue by introducing this check. FormatStatValue is usually called in the printer when we want to print some information of a parquet file for debugging purpuse.

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@jmestwa-coder jmestwa-coder May 26, 2026

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Fair, it's mostly the debug/printer path. The thing is val is taken verbatim from the file's Thrift stats, so a truncated min/max makes the BOOLEAN/INT96/numeric memcpys read past the end of the buffer even there. The guard is just a size check in front of the existing loads, so I tried to keep it minimal. Happy to trim it further if it still feels too heavy.

std::stringstream ss;
ss << "Statistics value of " << val.size() << " bytes is too small for "
<< TypeToString(parquet_type);
throw ParquetException(ss.str());
}

std::stringstream result;
const char* bytes = val.data();
switch (parquet_type) {
Expand Down
23 changes: 23 additions & 0 deletions cpp/src/parquet/types_test.cc
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Expand Up @@ -20,6 +20,7 @@
#include <string>

#include "arrow/util/endian.h"
#include "parquet/exception.h"
#include "parquet/types.h"

namespace parquet {
Expand Down Expand Up @@ -179,6 +180,28 @@ TEST(TypePrinter, StatisticsTypes) {
FormatStatValue(Type::FIXED_LEN_BYTE_ARRAY, smin, LogicalType::Float16()));
}

TEST(TypePrinter, StatisticsTypesShortValue) {
// A maliciously crafted Parquet file may set a statistics min/max shorter
// than the column's physical type. FormatStatValue must reject it instead of
// memcpy'ing past the buffer.
ASSERT_THROW(FormatStatValue(Type::BOOLEAN, std::string()), ParquetException);
ASSERT_THROW(FormatStatValue(Type::INT32, std::string("abc")), ParquetException);
ASSERT_THROW(FormatStatValue(Type::INT64, std::string("abcdefg")), ParquetException);
ASSERT_THROW(FormatStatValue(Type::FLOAT, std::string()), ParquetException);
ASSERT_THROW(FormatStatValue(Type::DOUBLE, std::string("1234567")), ParquetException);
ASSERT_THROW(FormatStatValue(Type::INT96, std::string("12345678901")),
ParquetException);
ASSERT_THROW(FormatStatValue(Type::INT32, std::string("abc"),
LogicalType::Decimal(6, 2)),
ParquetException);
ASSERT_THROW(FormatStatValue(Type::INT64, std::string("abcdefg"),
LogicalType::Decimal(18, 4)),
ParquetException);
ASSERT_THROW(FormatStatValue(Type::FIXED_LEN_BYTE_ARRAY, std::string("a"),
LogicalType::Float16()),
ParquetException);
}

TEST(TestInt96Timestamp, Decoding) {
auto check = [](int32_t julian_day, uint64_t nanoseconds) {
#if ARROW_LITTLE_ENDIAN
Expand Down
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