src/google/protobuf/parse_context.cc

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd

#include "google/protobuf/parse_context.h"

#include <algorithm>
#include <cstring>

#include "absl/strings/cord.h"
#include "absl/strings/string_view.h"
#include "google/protobuf/message_lite.h"
#include "google/protobuf/repeated_field.h"
#include "google/protobuf/wire_format_lite.h"
#include "utf8_validity.h"


// Must be included last.
#include "google/protobuf/port_def.inc"

namespace google {
namespace protobuf {
namespace internal {

// Only call if at start of tag.
bool EpsCopyInputStream::ParseEndsInSlopRegion(const char* begin, int overrun,
                                               int depth) {
  constexpr int kSlopBytes = EpsCopyInputStream::kSlopBytes;
  ABSL_DCHECK_GE(overrun, 0);
  ABSL_DCHECK_LE(overrun, kSlopBytes);
  auto ptr = begin + overrun;
  auto end = begin + kSlopBytes;
  while (ptr < end) {
    uint32_t tag;
    ptr = ReadTag(ptr, &tag);
    if (ptr == nullptr || ptr > end) return false;
    // ending on 0 tag is allowed and is the major reason for the necessity of
    // this function.
    if (tag == 0) return true;
    switch (tag & 7) {
      case 0: {  // Varint
        uint64_t val;
        ptr = VarintParse(ptr, &val);
        if (ptr == nullptr) return false;
        break;
      }
      case 1: {  // fixed64
        ptr += 8;
        break;
      }
      case 2: {  // len delim
        int32_t size = ReadSize(&ptr);
        if (ptr == nullptr || size > end - ptr) return false;
        ptr += size;
        break;
      }
      case 3: {  // start group
        depth++;
        break;
      }
      case 4: {                    // end group
        if (--depth < 0) return true;  // We exit early
        break;
      }
      case 5: {  // fixed32
        ptr += 4;
        break;
      }
      default:
        return false;  // Unknown wireformat
    }
  }
  return false;
}

const char* EpsCopyInputStream::NextBuffer(int overrun, int depth) {
  if (next_chunk_ == nullptr) return nullptr;  // We've reached end of stream.
  if (next_chunk_ != patch_buffer_) {
    ABSL_DCHECK(size_ > kSlopBytes);
    // The chunk is large enough to be used directly
    buffer_end_ = next_chunk_ + size_ - kSlopBytes;
    auto res = next_chunk_;
    next_chunk_ = patch_buffer_;
    if (aliasing_ == kOnPatch) aliasing_ = kNoDelta;
    return res;
  }
  // Move the slop bytes of previous buffer to start of the patch buffer.
  // Note we must use memmove because the previous buffer could be part of
  // patch_buffer_.
  std::memmove(patch_buffer_, buffer_end_, kSlopBytes);
  if (overall_limit_ > 0 &&
      (depth < 0 || !ParseEndsInSlopRegion(patch_buffer_, overrun, depth))) {
    const void* data;
    // ZeroCopyInputStream indicates Next may return 0 size buffers. Hence
    // we loop.
    while (StreamNext(&data)) {
      if (size_ > kSlopBytes) {
        // We got a large chunk
        std::memcpy(patch_buffer_ + kSlopBytes, data, kSlopBytes);
        next_chunk_ = static_cast<const char*>(data);
        buffer_end_ = patch_buffer_ + kSlopBytes;
        if (aliasing_ >= kNoDelta) aliasing_ = kOnPatch;
        return patch_buffer_;
      } else if (size_ > 0) {
        std::memcpy(patch_buffer_ + kSlopBytes, data, size_);
        next_chunk_ = patch_buffer_;
        buffer_end_ = patch_buffer_ + size_;
        if (aliasing_ >= kNoDelta) aliasing_ = kOnPatch;
        return patch_buffer_;
      }
      ABSL_DCHECK(size_ == 0) << size_;
    }
    overall_limit_ = 0;  // Next failed, no more needs for next
  }
  // End of stream or array
  if (aliasing_ == kNoDelta) {
    // If there is no more block and aliasing is true, the previous block
    // is still valid and we can alias. We have users relying on string_view's
    // obtained from protos to outlive the proto, when the parse was from an
    // array. This guarantees string_view's are always aliased if parsed from
    // an array.
    aliasing_ = reinterpret_cast<std::uintptr_t>(buffer_end_) -
                reinterpret_cast<std::uintptr_t>(patch_buffer_);
  }
  next_chunk_ = nullptr;
  buffer_end_ = patch_buffer_ + kSlopBytes;
  size_ = 0;
  return patch_buffer_;
}

const char* EpsCopyInputStream::Next() {
  ABSL_DCHECK(limit_ > kSlopBytes);
  auto p = NextBuffer(0 /* immaterial */, -1);
  if (p == nullptr) {
    limit_end_ = buffer_end_;
    // Distinguish ending on a pushed limit or ending on end-of-stream.
    SetEndOfStream();
    return nullptr;
  }
  limit_ -= buffer_end_ - p;  // Adjust limit_ relative to new anchor
  limit_end_ = buffer_end_ + std::min(0, limit_);
  return p;
}

std::pair<const char*, bool> EpsCopyInputStream::DoneFallback(int overrun,
                                                              int depth) {
  // Did we exceeded the limit (parse error).
  if (PROTOBUF_PREDICT_FALSE(overrun > limit_)) return {nullptr, true};
  ABSL_DCHECK(overrun != limit_);  // Guaranteed by caller.
  ABSL_DCHECK(overrun < limit_);   // Follows from above
  // TODO Instead of this dcheck we could just assign, and remove
  // updating the limit_end from PopLimit, ie.
  // limit_end_ = buffer_end_ + (std::min)(0, limit_);
  // if (ptr < limit_end_) return {ptr, false};
  ABSL_DCHECK(limit_end_ == buffer_end_ + (std::min)(0, limit_));
  // At this point we know the following assertion holds.
  ABSL_DCHECK_GT(limit_, 0);
  ABSL_DCHECK(limit_end_ == buffer_end_);  // because limit_ > 0
  const char* p;
  do {
    // We are past the end of buffer_end_, in the slop region.
    ABSL_DCHECK_GE(overrun, 0);
    p = NextBuffer(overrun, depth);
    if (p == nullptr) {
      // We are at the end of the stream
      if (PROTOBUF_PREDICT_FALSE(overrun != 0)) return {nullptr, true};
      ABSL_DCHECK_GT(limit_, 0);
      limit_end_ = buffer_end_;
      // Distinguish ending on a pushed limit or ending on end-of-stream.
      SetEndOfStream();
      return {buffer_end_, true};
    }
    limit_ -= buffer_end_ - p;  // Adjust limit_ relative to new anchor
    p += overrun;
    overrun = p - buffer_end_;
  } while (overrun >= 0);
  limit_end_ = buffer_end_ + std::min(0, limit_);
  return {p, false};
}

const char* EpsCopyInputStream::SkipFallback(const char* ptr, int size) {
  return AppendSize(ptr, size, [](const char* /*p*/, int /*s*/) {});
}

const char* EpsCopyInputStream::ReadStringFallback(const char* ptr, int size,
                                                   std::string* str) {
  str->clear();
  if (PROTOBUF_PREDICT_TRUE(size <= buffer_end_ - ptr + limit_)) {
    // Reserve the string up to a static safe size. If strings are bigger than
    // this we proceed by growing the string as needed. This protects against
    // malicious payloads making protobuf hold on to a lot of memory.
    str->reserve(str->size() + std::min<int>(size, kSafeStringSize));
  }
  return AppendSize(ptr, size,
                    [str](const char* p, int s) { str->append(p, s); });
}

const char* EpsCopyInputStream::AppendStringFallback(const char* ptr, int size,
                                                     std::string* str) {
  if (PROTOBUF_PREDICT_TRUE(size <= buffer_end_ - ptr + limit_)) {
    // Reserve the string up to a static safe size. If strings are bigger than
    // this we proceed by growing the string as needed. This protects against
    // malicious payloads making protobuf hold on to a lot of memory.
    str->reserve(str->size() + std::min<int>(size, kSafeStringSize));
  }
  return AppendSize(ptr, size,
                    [str](const char* p, int s) { str->append(p, s); });
}

const char* EpsCopyInputStream::ReadCordFallback(const char* ptr, int size,
                                                 absl::Cord* cord) {
  if (zcis_ == nullptr) {
    int bytes_from_buffer = buffer_end_ - ptr + kSlopBytes;
    if (size <= bytes_from_buffer) {
      *cord = absl::string_view(ptr, size);
      return ptr + size;
    }
    return AppendSize(ptr, size, [cord](const char* p, int s) {
      cord->Append(absl::string_view(p, s));
    });
  }
  int new_limit = buffer_end_ - ptr + limit_;
  if (size > new_limit) return nullptr;
  new_limit -= size;
  int bytes_from_buffer = buffer_end_ - ptr + kSlopBytes;
  const bool in_patch_buf = reinterpret_cast<uintptr_t>(ptr) -
                                reinterpret_cast<uintptr_t>(patch_buffer_) <=
                            kPatchBufferSize;
  if (bytes_from_buffer > kPatchBufferSize || !in_patch_buf) {
    cord->Clear();
    StreamBackUp(bytes_from_buffer);
  } else if (bytes_from_buffer == kSlopBytes && next_chunk_ != nullptr &&
             // Only backup if next_chunk_ points to a valid buffer returned by
             // ZeroCopyInputStream. This happens when NextStream() returns a
             // chunk that's smaller than or equal to kSlopBytes.
             next_chunk_ != patch_buffer_) {
    cord->Clear();
    StreamBackUp(size_);
  } else {
    size -= bytes_from_buffer;
    ABSL_DCHECK_GT(size, 0);
    *cord = absl::string_view(ptr, bytes_from_buffer);
    if (next_chunk_ == patch_buffer_) {
      // We have read to end of the last buffer returned by
      // ZeroCopyInputStream. So the stream is in the right position.
    } else if (next_chunk_ == nullptr) {
      // There is no remaining chunks. We can't read size.
      SetEndOfStream();
      return nullptr;
    } else {
      // Next chunk is already loaded
      ABSL_DCHECK(size_ > kSlopBytes);
      StreamBackUp(size_ - kSlopBytes);
    }
  }
  if (size > overall_limit_) return nullptr;
  overall_limit_ -= size;
  if (!zcis_->ReadCord(cord, size)) return nullptr;
  ptr = InitFrom(zcis_);
  limit_ = new_limit - static_cast<int>(buffer_end_ - ptr);
  limit_end_ = buffer_end_ + (std::min)(0, limit_);
  return ptr;
}


const char* EpsCopyInputStream::InitFrom(io::ZeroCopyInputStream* zcis) {
  zcis_ = zcis;
  const void* data;
  int size;
  limit_ = INT_MAX;
  if (zcis->Next(&data, &size)) {
    overall_limit_ -= size;
    if (size > kSlopBytes) {
      auto ptr = static_cast<const char*>(data);
      limit_ -= size - kSlopBytes;
      limit_end_ = buffer_end_ = ptr + size - kSlopBytes;
      next_chunk_ = patch_buffer_;
      if (aliasing_ == kOnPatch) aliasing_ = kNoDelta;
      return ptr;
    } else {
      limit_end_ = buffer_end_ = patch_buffer_ + kSlopBytes;
      next_chunk_ = patch_buffer_;
      auto ptr = patch_buffer_ + kPatchBufferSize - size;
      std::memcpy(ptr, data, size);
      return ptr;
    }
  }
  overall_limit_ = 0;
  next_chunk_ = nullptr;
  size_ = 0;
  limit_end_ = buffer_end_ = patch_buffer_;
  return patch_buffer_;
}

const char* ParseContext::ReadSizeAndPushLimitAndDepth(const char* ptr,
                                                       LimitToken* old_limit) {
  return ReadSizeAndPushLimitAndDepthInlined(ptr, old_limit);
}

const char* ParseContext::ParseMessage(MessageLite* msg, const char* ptr) {
  LimitToken old;
  ptr = ReadSizeAndPushLimitAndDepth(ptr, &old);
  if (ptr == nullptr) return ptr;
  auto old_depth = depth_;
  ptr = msg->_InternalParse(ptr, this);
  if (ptr != nullptr) ABSL_DCHECK_EQ(old_depth, depth_);
  depth_++;
  if (!PopLimit(std::move(old))) return nullptr;
  return ptr;
}

inline void WriteVarint(uint64_t val, std::string* s) {
  while (val >= 128) {
    uint8_t c = val | 0x80;
    s->push_back(c);
    val >>= 7;
  }
  s->push_back(val);
}

void WriteVarint(uint32_t num, uint64_t val, std::string* s) {
  WriteVarint(num << 3, s);
  WriteVarint(val, s);
}

void WriteLengthDelimited(uint32_t num, absl::string_view val, std::string* s) {
  WriteVarint((num << 3) + 2, s);
  WriteVarint(val.size(), s);
  s->append(val.data(), val.size());
}

std::pair<const char*, uint32_t> VarintParseSlow32(const char* p,
                                                   uint32_t res) {
  for (std::uint32_t i = 1; i < 5; i++) {
    uint32_t byte = static_cast<uint8_t>(p[i]);
    res += (byte - 1) << (7 * i);
    if (PROTOBUF_PREDICT_TRUE(byte < 128)) {
      return {p + i + 1, res};
    }
  }
  // Accept >5 bytes
  for (std::uint32_t i = 5; i < 10; i++) {
    uint32_t byte = static_cast<uint8_t>(p[i]);
    if (PROTOBUF_PREDICT_TRUE(byte < 128)) {
      return {p + i + 1, res};
    }
  }
  return {nullptr, 0};
}

std::pair<const char*, uint64_t> VarintParseSlow64(const char* p,
                                                   uint32_t res32) {
  uint64_t res = res32;
  for (std::uint32_t i = 1; i < 10; i++) {
    uint64_t byte = static_cast<uint8_t>(p[i]);
    res += (byte - 1) << (7 * i);
    if (PROTOBUF_PREDICT_TRUE(byte < 128)) {
      return {p + i + 1, res};
    }
  }
  return {nullptr, 0};
}

std::pair<const char*, uint32_t> ReadTagFallback(const char* p, uint32_t res) {
  for (std::uint32_t i = 2; i < 5; i++) {
    uint32_t byte = static_cast<uint8_t>(p[i]);
    res += (byte - 1) << (7 * i);
    if (PROTOBUF_PREDICT_TRUE(byte < 128)) {
      return {p + i + 1, res};
    }
  }
  return {nullptr, 0};
}

std::pair<const char*, int32_t> ReadSizeFallback(const char* p, uint32_t res) {
  for (std::uint32_t i = 1; i < 4; i++) {
    uint32_t byte = static_cast<uint8_t>(p[i]);
    res += (byte - 1) << (7 * i);
    if (PROTOBUF_PREDICT_TRUE(byte < 128)) {
      return {p + i + 1, res};
    }
  }
  std::uint32_t byte = static_cast<uint8_t>(p[4]);
  if (PROTOBUF_PREDICT_FALSE(byte >= 8)) return {nullptr, 0};  // size >= 2gb
  res += (byte - 1) << 28;
  // Protect against sign integer overflow in PushLimit. Limits are relative
  // to buffer ends and ptr could potential be kSlopBytes beyond a buffer end.
  // To protect against overflow we reject limits absurdly close to INT_MAX.
  if (PROTOBUF_PREDICT_FALSE(res > INT_MAX - ParseContext::kSlopBytes)) {
    return {nullptr, 0};
  }
  return {p + 5, res};
}

const char* StringParser(const char* begin, const char* end, void* object,
                         ParseContext*) {
  auto str = static_cast<std::string*>(object);
  str->append(begin, end - begin);
  return end;
}

// Defined in wire_format_lite.cc
void PrintUTF8ErrorLog(absl::string_view message_name,
                       absl::string_view field_name, const char* operation_str,
                       bool emit_stacktrace);

bool VerifyUTF8(absl::string_view str, const char* field_name) {
  if (!utf8_range::IsStructurallyValid(str)) {
    PrintUTF8ErrorLog("", field_name, "parsing", false);
    return false;
  }
  return true;
}

const char* InlineGreedyStringParser(std::string* s, const char* ptr,
                                     ParseContext* ctx) {
  int size = ReadSize(&ptr);
  if (!ptr) return nullptr;
  return ctx->ReadString(ptr, size, s);
}


template <typename T, bool sign>
const char* VarintParser(void* object, const char* ptr, ParseContext* ctx) {
  return ctx->ReadPackedVarint(ptr, [object](uint64_t varint) {
    T val;
    if (sign) {
      if (sizeof(T) == 8) {
        val = WireFormatLite::ZigZagDecode64(varint);
      } else {
        val = WireFormatLite::ZigZagDecode32(varint);
      }
    } else {
      val = varint;
    }
    static_cast<RepeatedField<T>*>(object)->Add(val);
  });
}

const char* PackedInt32Parser(void* object, const char* ptr,
                              ParseContext* ctx) {
  return VarintParser<int32_t, false>(object, ptr, ctx);
}
const char* PackedUInt32Parser(void* object, const char* ptr,
                               ParseContext* ctx) {
  return VarintParser<uint32_t, false>(object, ptr, ctx);
}
const char* PackedInt64Parser(void* object, const char* ptr,
                              ParseContext* ctx) {
  return VarintParser<int64_t, false>(object, ptr, ctx);
}
const char* PackedUInt64Parser(void* object, const char* ptr,
                               ParseContext* ctx) {
  return VarintParser<uint64_t, false>(object, ptr, ctx);
}
const char* PackedSInt32Parser(void* object, const char* ptr,
                               ParseContext* ctx) {
  return VarintParser<int32_t, true>(object, ptr, ctx);
}
const char* PackedSInt64Parser(void* object, const char* ptr,
                               ParseContext* ctx) {
  return VarintParser<int64_t, true>(object, ptr, ctx);
}

const char* PackedEnumParser(void* object, const char* ptr, ParseContext* ctx) {
  return VarintParser<int, false>(object, ptr, ctx);
}

const char* PackedBoolParser(void* object, const char* ptr, ParseContext* ctx) {
  return VarintParser<bool, false>(object, ptr, ctx);
}

template <typename T>
const char* FixedParser(void* object, const char* ptr, ParseContext* ctx) {
  int size = ReadSize(&ptr);
  return ctx->ReadPackedFixed(ptr, size,
                              static_cast<RepeatedField<T>*>(object));
}

const char* PackedFixed32Parser(void* object, const char* ptr,
                                ParseContext* ctx) {
  return FixedParser<uint32_t>(object, ptr, ctx);
}
const char* PackedSFixed32Parser(void* object, const char* ptr,
                                 ParseContext* ctx) {
  return FixedParser<int32_t>(object, ptr, ctx);
}
const char* PackedFixed64Parser(void* object, const char* ptr,
                                ParseContext* ctx) {
  return FixedParser<uint64_t>(object, ptr, ctx);
}
const char* PackedSFixed64Parser(void* object, const char* ptr,
                                 ParseContext* ctx) {
  return FixedParser<int64_t>(object, ptr, ctx);
}
const char* PackedFloatParser(void* object, const char* ptr,
                              ParseContext* ctx) {
  return FixedParser<float>(object, ptr, ctx);
}
const char* PackedDoubleParser(void* object, const char* ptr,
                               ParseContext* ctx) {
  return FixedParser<double>(object, ptr, ctx);
}

class UnknownFieldLiteParserHelper {
 public:
  explicit UnknownFieldLiteParserHelper(std::string* unknown)
      : unknown_(unknown) {}

  void AddVarint(uint32_t num, uint64_t value) {
    if (unknown_ == nullptr) return;
    WriteVarint(num * 8, unknown_);
    WriteVarint(value, unknown_);
  }
  void AddFixed64(uint32_t num, uint64_t value) {
    if (unknown_ == nullptr) return;
    WriteVarint(num * 8 + 1, unknown_);
    char buffer[8];
    io::CodedOutputStream::WriteLittleEndian64ToArray(
        value, reinterpret_cast<uint8_t*>(buffer));
    unknown_->append(buffer, 8);
  }
  const char* ParseLengthDelimited(uint32_t num, const char* ptr,
                                   ParseContext* ctx) {
    int size = ReadSize(&ptr);
    GOOGLE_PROTOBUF_PARSER_ASSERT(ptr);
    if (unknown_ == nullptr) return ctx->Skip(ptr, size);
    WriteVarint(num * 8 + 2, unknown_);
    WriteVarint(size, unknown_);
    return ctx->AppendString(ptr, size, unknown_);
  }
  const char* ParseGroup(uint32_t num, const char* ptr, ParseContext* ctx) {
    if (unknown_) WriteVarint(num * 8 + 3, unknown_);
    ptr = ctx->ParseGroupInlined(ptr, num * 8 + 3, [&](const char* ptr) {
      return WireFormatParser(*this, ptr, ctx);
    });
    GOOGLE_PROTOBUF_PARSER_ASSERT(ptr);
    if (unknown_) WriteVarint(num * 8 + 4, unknown_);
    return ptr;
  }
  void AddFixed32(uint32_t num, uint32_t value) {
    if (unknown_ == nullptr) return;
    WriteVarint(num * 8 + 5, unknown_);
    char buffer[4];
    io::CodedOutputStream::WriteLittleEndian32ToArray(
        value, reinterpret_cast<uint8_t*>(buffer));
    unknown_->append(buffer, 4);
  }

 private:
  std::string* unknown_;
};

const char* UnknownGroupLiteParse(std::string* unknown, const char* ptr,
                                  ParseContext* ctx) {
  UnknownFieldLiteParserHelper field_parser(unknown);
  return WireFormatParser(field_parser, ptr, ctx);
}

const char* UnknownFieldParse(uint32_t tag, std::string* unknown,
                              const char* ptr, ParseContext* ctx) {
  UnknownFieldLiteParserHelper field_parser(unknown);
  return FieldParser(tag, field_parser, ptr, ctx);
}

}  // namespace internal
}  // namespace protobuf
}  // namespace google

#include "google/protobuf/port_undef.inc"