[libxml2] Use FuzzedDataProvider isntead of byte_stream. (#2809)

2 files changed, 9 insertions, 150 deletions

diff --git a/projects/libxml2/byte_stream.h b/projects/libxml2/byte_stream.h
deleted file mode 100644
index da72d5573..000000000
--- a/projects/libxml2/byte_stream.h
+++ /dev/null
@@ -1,142 +0,0 @@
-// Copyright 2018 Google Inc.
-//
-// Licensed 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
-//
-//      http://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.
-
-#ifndef BYTE_STREAM_H_
-#define BYTE_STREAM_H_
-
-#include <algorithm>
-#include <cstddef>
-#include <cstdint>
-#include <limits>
-#include <string>
-
-// Wrapper for fuzzer input strings that helps consume and interpret the data
-// as a sequence of values, such as strings and PODs.
-class ByteStream {
- public:
-  // Does not take ownership of data.
-  ByteStream(const uint8_t* data, size_t size)
-      : data_(data), size_(size), position_(0) {}
-
-  ByteStream(const ByteStream&) = delete;
-  ByteStream& operator=(const ByteStream&) = delete;
-
-  // Returns a pointer to the chunk of data of |size| bytes, where |size| is
-  // either a requested value or all the bytes that are available. If the
-  // requested |size| is 0, return all the bytes that are available.
-  const uint8_t* GetNextChunk(size_t* size);
-
-  // Returns a string. Strings are obtained from the byte stream by reading a
-  // size_t N followed by N char elements. If there are fewer than N bytes left
-  // in the stream, this returns as many bytes as are available.
-  std::string GetNextString();
-
-  // The following GetNext{integer type} functions all return the next
-  // sizeof(integer type) bytes in the stream or 0 if there is insufficient
-  // capacity.
-  size_t GetNextSizeT() { return ConsumeCopyOrDefault<size_t>(0); }
-  int GetNextInt() { return ConsumeCopyOrDefault<int>(0); }
-  uint8_t GetNextUint8() { return ConsumeCopyOrDefault<uint8_t>(0); }
-  int64_t GetNextInt64() { return ConsumeCopyOrDefault<int64_t>(0); }
-
-  // Returns an integer in the range [0,n) for n > 0 and consumes up to
-  // sizeof(int) bytes. For n<=0, returns 0 and consumes 0 bytes.
-  int GetNextInt(int n);
-
- private:
-  // The remaining capacity of the ByteStream.
-  size_t capacity() const { return size_ - position_; }
-
-  // Returns data_ + position_ and then advances position_ by requested bytes.
-  //
-  // This is the canonical way for the class to request regions of memory
-  // or to advance the position by requested bytes. This operation is unchecked
-  // for maintaining that position_ <= size_. Requesting 0 bytes always
-  // succeeds.
-  const uint8_t* UncheckedConsume(size_t requested) {
-    const uint8_t* region = data_ + position_;
-    position_ += requested;
-    return region;
-  }
-
-  // Directly initialize T by copying sizeof(T) bytes into results if there is
-  // sufficient capacity in the stream. If there is not sufficient capacity
-  // result is unmodified.
-  template <class T>
-  void ConsumeBytesByCopy(T* result) {
-    constexpr size_t type_size = sizeof(T);
-    if (type_size <= capacity()) {
-      const uint8_t* region = UncheckedConsume(type_size);
-      memcpy(static_cast<void*>(result), region, type_size);
-    } else {
-      // Consume the remainder of data_.
-      UncheckedConsume(capacity());
-    }
-  }
-
-  // A helper function for using ConsumeBytesByCopy and returning a default
-  // value `t` if there is insufficient capacity to read a full `T`. T should
-  // probably be a primitive type.
-  template <class T>
-  T ConsumeCopyOrDefault(T t) {
-    ConsumeBytesByCopy(&t);
-    return t;
-  }
-
-  const uint8_t* data_;
-  const size_t size_;
-  size_t position_;
-};
-
-inline const uint8_t* ByteStream::GetNextChunk(size_t* size) {
-  if (*size)
-    *size = std::min(*size, capacity());
-  else
-    *size = capacity();
-
-  return UncheckedConsume(*size);
-}
-
-inline std::string ByteStream::GetNextString() {
-  const size_t requested_size = GetNextSizeT();
-  const size_t consumed_size = std::min(requested_size, capacity());
-  const uint8_t* selection = UncheckedConsume(consumed_size);
-  return std::string(reinterpret_cast<const char*>(selection), consumed_size);
-}
-
-inline int ByteStream::GetNextInt(int n) {
-  if (n <= 0) {
-    return 0;
-  }
-  // We grab as few bytes as possible as n will often be fixed.
-  int selection = 0;
-  if (n <= std::numeric_limits<uint8_t>::max()) {
-    selection = static_cast<int>(GetNextUint8());
-  } else if (n <= std::numeric_limits<uint16_t>::max()) {
-    selection = ConsumeCopyOrDefault<uint16_t>(0);
-  } else {
-    selection = GetNextInt();
-  }
-
-  // Take the absolute value of selection w/o undefined behavior.
-  // If selection is INT_MIN, return 0.
-  if (selection == std::numeric_limits<int>::min()) {
-    selection = 0;
-  } else if (selection < 0) {
-    selection = -selection;
-  }
-  return selection % n;
-}
-
-#endif  // BYTE_STREAM_H_
diff --git a/projects/libxml2/libxml2_xml_reader_for_file_fuzzer.cc b/projects/libxml2/libxml2_xml_reader_for_file_fuzzer.cc
index ab296d834..4a71aa5a9 100644
--- a/projects/libxml2/libxml2_xml_reader_for_file_fuzzer.cc
+++ b/projects/libxml2/libxml2_xml_reader_for_file_fuzzer.cc
@@ -12,11 +12,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <fuzzer/FuzzedDataProvider.h>
+
 #include <cstddef>
 #include <cstdint>
 #include <string>
 
-#include "byte_stream.h"
 #include "fuzzer_temp_file.h"
 
 #include "libxml/xmlreader.h"
@@ -28,14 +29,14 @@ void ignore (void* ctx, const char* msg, ...) {
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
   xmlSetGenericErrorFunc(NULL, &ignore);
 
-  ByteStream stream(data, size);
-  const int options = stream.GetNextInt();
-  const std::string encoding = stream.GetNextString();
-  size_t file_contents_size = 0;
-  const uint8_t* file_contents = stream.GetNextChunk(&file_contents_size);
+  FuzzedDataProvider provider(data, size);
+  const int options = provider.ConsumeIntegral<int>();
+
+  // libxml does not expect more than 100 characters, let's go beyond that.
+  const std::string encoding = provider.ConsumeRandomLengthString(128);
+  auto file_contents = provider.ConsumeRemainingBytes<uint8_t>();
 
-  // Intentionally pass raw data as the API does not require trailing \0.
-  FuzzerTemporaryFile file(file_contents, file_contents_size);
+  FuzzerTemporaryFile file(file_contents.data(), file_contents.size());
 
   xmlTextReaderPtr xmlReader =
       xmlReaderForFile(file.filename(), encoding.c_str(), options);