Introducing single for loop into clang_proto_fuzzer

[emmettneyman]

Summary

Created a new protobuf and protobuf-to-C++ "converter" that wraps the entire C++ code in a single for loop.

• Slightly changed cxx_proto.proto -> cxx_loop_proto.proto
• Made some changes to proto_to_cxx files to handle the new kind of protobuf
• Created ExampleClangLoopProtoFuzzer to test new protobuf and "converter"

Patch by Emmett Neyman

[emmettneyman]

Took out typo'd comment

[vitalybuka]

tools/clang-fuzzer/fuzzer-initialize/fuzzer_initialize.cpp

23 ↗

(On Diff #150192)

I guess you already committed this patch.
Could you please try rebase to upstream, e.g. "git pull -r" and re-upload the review

[morehouse]

This contains changes from previous patch. Please rebase.

[emmettneyman]

Hopefully rebased correctly.

[morehouse]

tools/clang-fuzzer/cxx_loop_proto.proto

94

Maybe call this LoopFunction to distinguish from the other protobuf.

tools/clang-fuzzer/fuzzer-initialize/fuzzer_initialize.cpp

14 ↗

(On Diff #150200)

Nit: Try not to introduce whitespace at end of lines. Depending on your configuration, this causes git to complain.

tools/clang-fuzzer/proto-to-cxx/loop_proto_to_cxx.cpp

116

Right now this file duplicates a lot of code from proto_to_cxx.cpp. But assuming this file will continue to diverge from proto_to_cxx.cpp, I'm fine with the duplication for now.

tools/clang-fuzzer/proto-to-cxx/loop_proto_to_cxx.h

22

Instead of making a whole new header for this, can we simply add LoopProtoToCxx() and LoopFunctionToString() to proto_to_cxx.h? Then implement them in loop_proto_to_cxx.cpp?

[emmettneyman]

• Combined two header files into one
• Also renamed protobuf to LoopFunction

[morehouse]

tools/clang-fuzzer/CMakeLists.txt

28

I think it makes sense to use separate SRCS and HDRS variables for cxx_loop_proto.proto. Otherwise each proto-fuzzer will be compiled with both protobufs even though each only uses one.

58

Why is this here twice?

90

Maybe you can cut down on some LOC here by creating a COMMON_PROTO_FUZZ_LIBRARIES variable with the dependencies that overlap between the proto-fuzzers.

tools/clang-fuzzer/proto-to-cxx/loop_proto_to_cxx.h

22

Can we remove this file completely?

[emmettneyman]

• refactored cmake and deleted header file

[vitalybuka]

git clang-format -f --style=file HEAD^

tools/clang-fuzzer/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS ${LLVM_TARGETS_TO_BUILD} FuzzMutate)
 set(CXX_FLAGS_NOFUZZ ${CMAKE_CXX_FLAGS})
 set(DUMMY_MAIN DummyClangFuzzer.cpp)
 if(LLVM_LIB_FUZZING_ENGINE)
   unset(DUMMY_MAIN)
 elseif(LLVM_USE_SANITIZE_COVERAGE)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=fuzzer")
   set(CXX_FLAGS_NOFUZZ "${CXX_FLAGS_NOFUZZ} -fsanitize=fuzzer-no-link")
   unset(DUMMY_MAIN)
 endif()
 
 # Needed by LLVM's CMake checks because this file defines multiple targets.
 set(LLVM_OPTIONAL_SOURCES
   ClangFuzzer.cpp
   DummyClangFuzzer.cpp
   ExampleClangProtoFuzzer.cpp
+  ExampleClangLoopProtoFuzzer.cpp
   )
 
 if(CLANG_ENABLE_PROTO_FUZZER)
   # Create protobuf .h and .cc files, and put them in a library for use by
   # clang-proto-fuzzer components.
   find_package(Protobuf REQUIRED)
   add_definitions(-DGOOGLE_PROTOBUF_NO_RTTI)
   include_directories(${PROTOBUF_INCLUDE_DIRS})
   include_directories(${CMAKE_CURRENT_BINARY_DIR})
   protobuf_generate_cpp(PROTO_SRCS PROTO_HDRS cxx_proto.proto)
+  protobuf_generate_cpp(PROTO_SRCS PROTO_HDRS cxx_loop_proto.proto)
   set(LLVM_OPTIONAL_SOURCES ${LLVM_OPTIONAL_SOURCES} ${PROTO_SRCS})
   add_clang_library(clangCXXProto
     ${PROTO_SRCS}
     ${PROTO_HDRS}
 
     LINK_LIBS
     ${PROTOBUF_LIBRARIES}
     )
 
+  add_clang_library(clangCXXLoopProto
+    ${PROTO_SRCS}
+    ${PROTO_HDRS}
+
+    LINK_LIBS
+    ${PROTOBUF_LIBRARIES}
+    )
+
   # Build and include libprotobuf-mutator
   include(ProtobufMutator)
   include_directories(${ProtobufMutator_INCLUDE_DIRS})
 
   # Build the protobuf->C++ translation library and driver.
   add_clang_subdirectory(proto-to-cxx)
   
   # Build the fuzzer initialization library.
   add_clang_subdirectory(fuzzer-initialize)
 
+  # Build the fuzzer initialization library.
+  add_clang_subdirectory(fuzzer-initialize)
+
   # Build the protobuf fuzzer
   add_clang_executable(clang-proto-fuzzer
     ${DUMMY_MAIN}
     ExampleClangProtoFuzzer.cpp
     )
 
+  # Build the loop protobuf fuzzer
+  add_clang_executable(clang-loop-proto-fuzzer
+    ${DUMMY_MAIN}
+    ExampleClangLoopProtoFuzzer.cpp
+    )
+
   target_link_libraries(clang-proto-fuzzer
     PRIVATE
     ${ProtobufMutator_LIBRARIES}
     ${PROTOBUF_LIBRARIES}
     ${LLVM_LIB_FUZZING_ENGINE}
     clangCXXProto
     clangFuzzerInitialize
     clangHandleCXX
     clangProtoToCXX
     )
+  target_link_libraries(clang-loop-proto-fuzzer
+    PRIVATE
+    ${ProtobufMutator_LIBRARIES}
+    ${PROTOBUF_LIBRARIES}
+    ${LLVM_LIB_FUZZING_ENGINE}
+    clangCXXLoopProto
+    clangFuzzerInitialize
+    clangHandleCXX
+    clangLoopProtoToCXX
+    )
 endif()
 
 add_clang_subdirectory(handle-cxx)
 
 add_clang_executable(clang-fuzzer
   EXCLUDE_FROM_ALL
   ${DUMMY_MAIN}
   ClangFuzzer.cpp
   )
 
 target_link_libraries(clang-fuzzer
   PRIVATE
   ${LLVM_LIB_FUZZING_ENGINE}
   clangHandleCXX
   )

tools/clang-fuzzer/ExampleClangLoopProtoFuzzer.cpp

+//===-- ExampleClangLoopProtoFuzzer.cpp - Fuzz Clang ----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+///  This file implements a function that runs Clang on a single
+///  input and uses libprotobuf-mutator to find new inputs. This function is
+///  then linked into the Fuzzer library. This file differs from 
+///  ExampleClangProtoFuzzer in that it uses the new protobuf that includes 
+///  C++ code with a single for loop.
+///
+//===----------------------------------------------------------------------===//
+
+#include "cxx_loop_proto.pb.h"
+#include "handle-cxx/handle_cxx.h"
+#include "proto-to-cxx/proto_to_cxx.h"
+#include "fuzzer-initialize/fuzzer_initialize.h"
+#include "src/libfuzzer/libfuzzer_macro.h"
+
+
+using namespace clang_fuzzer;
+
+DEFINE_BINARY_PROTO_FUZZER(const LoopFunction& input) {
+  auto S = LoopFunctionToString(input);
+  HandleCXX(S, GetCLArgs());
+}

tools/clang-fuzzer/cxx_loop_proto.proto

+//===-- cxx_loop_proto.proto - Protobuf description of C++ with for loops -===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+///  This file describes a subset of C++ as a protobuf. It is used to
+///  more easily find interesting inputs for fuzzing Clang. This subset
+///  extends the one defined in cxx_proto.proto by adding the option that
+///  a VarRef can use the for loop's counter variable.
+///
+//===----------------------------------------------------------------------===//
+
+
+syntax = "proto2";
+
+message VarRef {
+  required int32 varnum = 1;
+  required bool is_loop_var = 2;
+}
+
+message Lvalue {
+  required VarRef varref = 1;
+}
+
+message Const {
+  required int32 val = 1;
+}
+
+message BinaryOp {
+  enum Op {
+    PLUS = 0;
+    MINUS = 1;
+    MUL = 2;
+    DIV = 3;
+    MOD = 4;
+    XOR = 5;
+    AND = 6;
+    OR = 7;
+    EQ = 8;
+    NE = 9;
+    LE = 10;
+    GE = 11;
+    LT = 12;
+    GT = 13;
+  };
+  required Op op = 1;
+  required Rvalue left = 2;
+  required Rvalue right = 3;
+}
+
+message Rvalue {
+  oneof rvalue_oneof {
+    VarRef varref = 1;
+    Const cons = 2;
+    BinaryOp binop = 3;
+  }
+}
+
+message AssignmentStatement {
+  required Lvalue lvalue = 1;
+  required Rvalue rvalue = 2;
+}
+
+
+message IfElse {
+  required Rvalue cond = 1;
+  required StatementSeq if_body = 2;
+  required StatementSeq else_body = 3;
+}
+
+message While {
+  required Rvalue cond = 1;
+  required StatementSeq body = 2;
+}
+
+message Statement {
+  oneof stmt_oneof {
+    AssignmentStatement assignment = 1;
+    IfElse              ifelse     = 2;
+    While               while_loop = 3;
+  }
+}
+
+message StatementSeq {
+  repeated Statement statements = 1;
+}
+
+message LoopFunction {
+  required StatementSeq statements = 1;
+}
+
+package clang_fuzzer;

tools/clang-fuzzer/proto-to-cxx/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS ${LLVM_TARGETS_TO_BUILD})
 set(CMAKE_CXX_FLAGS ${CXX_FLAGS_NOFUZZ})
 
 # Needed by LLVM's CMake checks because this file defines multiple targets.
-set(LLVM_OPTIONAL_SOURCES proto_to_cxx.cpp proto_to_cxx_main.cpp)
+set(LLVM_OPTIONAL_SOURCES proto_to_cxx.cpp proto_to_cxx_main.cpp
+                          loop_proto_to_cxx.cpp loop_proto_to_cxx_main.cpp)
 
 add_clang_library(clangProtoToCXX proto_to_cxx.cpp
                   DEPENDS clangCXXProto
                   LINK_LIBS clangCXXProto ${PROTOBUF_LIBRARIES}
                   )
 
+add_clang_library(clangLoopProtoToCXX loop_proto_to_cxx.cpp
+                  DEPENDS clangCXXLoopProto
+                  LINK_LIBS clangCXXLoopProto ${PROTOBUF_LIBRARIES}
+                  )
+
 add_clang_executable(clang-proto-to-cxx proto_to_cxx_main.cpp)
+add_clang_executable(clang-loop-proto-to-cxx loop_proto_to_cxx_main.cpp)
+
 target_link_libraries(clang-proto-to-cxx PRIVATE clangProtoToCXX)
+target_link_libraries(clang-loop-proto-to-cxx PRIVATE clangLoopProtoToCXX)

tools/clang-fuzzer/proto-to-cxx/loop_proto_to_cxx.h

-//==-- proto_to_cxx.h - Protobuf-C++ conversion ----------------------------==//
+//==-- loop_proto_to_cxx.h - Protobuf-C++ conversion ----------------------------==//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
-// Defines functions for converting between protobufs and C++.
+// Defines functions for converting between protobufs with loops and C++.
 //
 //===----------------------------------------------------------------------===//
 
 #include <cstdint>
 #include <cstddef>
 #include <string>
 
 namespace clang_fuzzer {
-class Function;
-std::string FunctionToString(const Function &input);
-std::string ProtoToCxx(const uint8_t *data, size_t size);
+class LoopFunction;
 }

tools/clang-fuzzer/proto-to-cxx/loop_proto_to_cxx.cpp

+//==-- loop_proto_to_cxx.cpp - Protobuf-C++ conversion ---------------------==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Implements functions for converting between protobufs and C++. Extends
+// proto_to_cxx.cpp by wrapping all the generated C++ code in a single for
+// loop. Also coutputs a different function signature that includes a 
+// size_t parameter for the loop to use.
+//
+//===----------------------------------------------------------------------===//
+
+#include "proto_to_cxx.h"
+#include "cxx_loop_proto.pb.h"
+
+// The following is needed to convert protos in human-readable form
+#include <google/protobuf/text_format.h>
+
+
+#include <ostream>
+#include <sstream>
+
+namespace clang_fuzzer {
+
+// Forward decls.
+std::ostream &operator<<(std::ostream &os, const BinaryOp &x);
+std::ostream &operator<<(std::ostream &os, const StatementSeq &x);
+
+// Proto to C++.
+std::ostream &operator<<(std::ostream &os, const Const &x) {
+  return os << "(" << x.val() << ")";
+}
+std::ostream &operator<<(std::ostream &os, const VarRef &x) {
+  if (x.is_loop_var()) {
+    return os << "a[loop_ctr]";
+  } else {
+    return os << "a[" << static_cast<uint32_t>(x.varnum()) << " % s]";
+  }
+}
+std::ostream &operator<<(std::ostream &os, const Lvalue &x) {
+  return os << x.varref();
+}
+std::ostream &operator<<(std::ostream &os, const Rvalue &x) {
+    if (x.has_varref()) return os << x.varref();
+    if (x.has_cons())   return os << x.cons();
+    if (x.has_binop())  return os << x.binop();
+    return os << "1";
+}
+std::ostream &operator<<(std::ostream &os, const BinaryOp &x) {
+  os << "(" << x.left();
+  switch (x.op()) {
+    case BinaryOp::PLUS: os << "+"; break;
+    case BinaryOp::MINUS: os << "-"; break;
+    case BinaryOp::MUL: os << "*"; break;
+    case BinaryOp::DIV: os << "/"; break;
+    case BinaryOp::MOD: os << "%"; break;
+    case BinaryOp::XOR: os << "^"; break;
+    case BinaryOp::AND: os << "&"; break;
+    case BinaryOp::OR: os << "|"; break;
+    case BinaryOp::EQ: os << "=="; break;
+    case BinaryOp::NE: os << "!="; break;
+    case BinaryOp::LE: os << "<="; break;
+    case BinaryOp::GE: os << ">="; break;
+    case BinaryOp::LT: os << "<"; break;
+    case BinaryOp::GT: os << ">"; break;
+  }
+  return os << x.right() << ")";
+}
+std::ostream &operator<<(std::ostream &os, const AssignmentStatement &x) {
+  return os << x.lvalue() << "=" << x.rvalue();
+}
+std::ostream &operator<<(std::ostream &os, const IfElse &x) {
+  return os << "if (" << x.cond() << "){\n"
+            << x.if_body() << "} else { \n"
+            << x.else_body() << "}\n";
+}
+std::ostream &operator<<(std::ostream &os, const While &x) {
+  return os << "while (" << x.cond() << "){\n" << x.body() << "}\n";
+}
+std::ostream &operator<<(std::ostream &os, const Statement &x) {
+  if (x.has_assignment()) return os << x.assignment() << ";\n";
+  if (x.has_ifelse())     return os << x.ifelse();
+  if (x.has_while_loop()) return os << x.while_loop();
+  return os << "(void)0;\n";
+}
+std::ostream &operator<<(std::ostream &os, const StatementSeq &x) {
+  for (auto &st : x.statements()) os << st;
+  return os;
+}
+std::ostream &operator<<(std::ostream &os, const LoopFunction &x) {
+  return os << "void foo(int *a, size_t s) {\n"
+            << "for (int loop_ctr = 0; loop_ctr < s; loop_ctr++){\n"
+            << x.statements() << "}\n}\n";
+}
+
+// ---------------------------------
+
+std::string LoopFunctionToString(const LoopFunction &input) {
+  std::ostringstream os;
+  os << input;
+  return os.str();
+
+}
+std::string LoopProtoToCxx(const uint8_t *data, size_t size) {
+  LoopFunction message;
+  if (!message.ParsePartialFromArray(data, size))
+    return "#error invalid proto, may not be binary encoded\n";
+  return LoopFunctionToString(message);
+}
+
+} // namespace clang_fuzzer

tools/clang-fuzzer/proto-to-cxx/loop_proto_to_cxx_main.cpp

+//==-- loop_proto_to_cxx_main.cpp - Driver for protobuf-C++ conversion -----==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Implements a simple driver to print a C++ program from a protobuf with loops.
+//
+//===----------------------------------------------------------------------===//
+
+// This is a copy and will be updated later to introduce changes
+
+#include <fstream>
+#include <iostream>
+#include <streambuf>
+#include <string>
+
+#include "proto_to_cxx.h"
+
+int main(int argc, char **argv) {
+  for (int i = 1; i < argc; i++) {
+    std::fstream in(argv[i]);
+    std::string str((std::istreambuf_iterator<char>(in)),
+                    std::istreambuf_iterator<char>());
+    std::cout << "// " << argv[i] << std::endl;
+    std::cout << clang_fuzzer::LoopProtoToCxx(
+        reinterpret_cast<const uint8_t *>(str.data()), str.size());
+  }
+}
+

tools/clang-fuzzer/proto-to-cxx/proto_to_cxx.h

 //===----------------------------------------------------------------------===//
 
 #include <cstdint>
 #include <cstddef>
 #include <string>
 
 namespace clang_fuzzer {
 class Function;
+class LoopFunction;
+
 std::string FunctionToString(const Function &input);
 std::string ProtoToCxx(const uint8_t *data, size_t size);
+std::string LoopFunctionToString(const LoopFunction &input);
+std::string LoopProtoToCxx(const uint8_t *data, size_t size);
 }