| //===- FuzzerTraceState.cpp - Trace-based fuzzer mutator ------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // This file implements a mutation algorithm based on instruction traces and |
| // on taint analysis feedback from DFSan. |
| // |
| // Instruction traces are special hooks inserted by the compiler around |
| // interesting instructions. Currently supported traces: |
| // * __sanitizer_cov_trace_cmp -- inserted before every ICMP instruction, |
| // receives the type, size and arguments of ICMP. |
| // |
| // Every time a traced event is intercepted we analyse the data involved |
| // in the event and suggest a mutation for future executions. |
| // For example if 4 bytes of data that derive from input bytes {4,5,6,7} |
| // are compared with a constant 12345, |
| // we try to insert 12345, 12344, 12346 into bytes |
| // {4,5,6,7} of the next fuzzed inputs. |
| // |
| // The fuzzer can work only with the traces, or with both traces and DFSan. |
| // |
| // DataFlowSanitizer (DFSan) is a tool for |
| // generalised dynamic data flow (taint) analysis: |
| // http://clang.llvm.org/docs/DataFlowSanitizer.html . |
| // |
| // The approach with DFSan-based fuzzing has some similarity to |
| // "Taint-based Directed Whitebox Fuzzing" |
| // by Vijay Ganesh & Tim Leek & Martin Rinard: |
| // http://dspace.mit.edu/openaccess-disseminate/1721.1/59320, |
| // but it uses a full blown LLVM IR taint analysis and separate instrumentation |
| // to analyze all of the "attack points" at once. |
| // |
| // Workflow with DFSan: |
| // * lib/Fuzzer/Fuzzer*.cpp is compiled w/o any instrumentation. |
| // * The code under test is compiled with DFSan *and* with instruction traces. |
| // * Every call to HOOK(a,b) is replaced by DFSan with |
| // __dfsw_HOOK(a, b, label(a), label(b)) so that __dfsw_HOOK |
| // gets all the taint labels for the arguments. |
| // * At the Fuzzer startup we assign a unique DFSan label |
| // to every byte of the input string (Fuzzer::CurrentUnit) so that for any |
| // chunk of data we know which input bytes it has derived from. |
| // * The __dfsw_* functions (implemented in this file) record the |
| // parameters (i.e. the application data and the corresponding taint labels) |
| // in a global state. |
| // * Fuzzer::ApplyTraceBasedMutation() tries to use the data recorded |
| // by __dfsw_* hooks to guide the fuzzing towards new application states. |
| // |
| // Parts of this code will not function when DFSan is not linked in. |
| // Instead of using ifdefs and thus requiring a separate build of lib/Fuzzer |
| // we redeclare the dfsan_* interface functions as weak and check if they |
| // are nullptr before calling. |
| // If this approach proves to be useful we may add attribute(weak) to the |
| // dfsan declarations in dfsan_interface.h |
| // |
| // This module is in the "proof of concept" stage. |
| // It is capable of solving only the simplest puzzles |
| // like test/dfsan/DFSanSimpleCmpTest.cpp. |
| //===----------------------------------------------------------------------===// |
| |
| /* Example of manual usage (-fsanitize=dataflow is optional): |
| ( |
| cd $LLVM/lib/Fuzzer/ |
| clang -fPIC -c -g -O2 -std=c++11 Fuzzer*.cpp |
| clang++ -O0 -std=c++11 -fsanitize-coverage=edge,trace-cmp \ |
| -fsanitize=dataflow \ |
| test/dfsan/DFSanSimpleCmpTest.cpp Fuzzer*.o |
| ./a.out |
| ) |
| */ |
| |
| #include "FuzzerInternal.h" |
| #include <sanitizer/dfsan_interface.h> |
| |
| #include <algorithm> |
| #include <cstring> |
| #include <unordered_map> |
| |
| extern "C" { |
| __attribute__((weak)) |
| dfsan_label dfsan_create_label(const char *desc, void *userdata); |
| __attribute__((weak)) |
| void dfsan_set_label(dfsan_label label, void *addr, size_t size); |
| __attribute__((weak)) |
| void dfsan_add_label(dfsan_label label, void *addr, size_t size); |
| __attribute__((weak)) |
| const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label); |
| __attribute__((weak)) |
| dfsan_label dfsan_read_label(const void *addr, size_t size); |
| } // extern "C" |
| |
| namespace fuzzer { |
| |
| static bool ReallyHaveDFSan() { |
| return &dfsan_create_label != nullptr; |
| } |
| |
| // These values are copied from include/llvm/IR/InstrTypes.h. |
| // We do not include the LLVM headers here to remain independent. |
| // If these values ever change, an assertion in ComputeCmp will fail. |
| enum Predicate { |
| ICMP_EQ = 32, ///< equal |
| ICMP_NE = 33, ///< not equal |
| ICMP_UGT = 34, ///< unsigned greater than |
| ICMP_UGE = 35, ///< unsigned greater or equal |
| ICMP_ULT = 36, ///< unsigned less than |
| ICMP_ULE = 37, ///< unsigned less or equal |
| ICMP_SGT = 38, ///< signed greater than |
| ICMP_SGE = 39, ///< signed greater or equal |
| ICMP_SLT = 40, ///< signed less than |
| ICMP_SLE = 41, ///< signed less or equal |
| }; |
| |
| template <class U, class S> |
| bool ComputeCmp(size_t CmpType, U Arg1, U Arg2) { |
| switch(CmpType) { |
| case ICMP_EQ : return Arg1 == Arg2; |
| case ICMP_NE : return Arg1 != Arg2; |
| case ICMP_UGT: return Arg1 > Arg2; |
| case ICMP_UGE: return Arg1 >= Arg2; |
| case ICMP_ULT: return Arg1 < Arg2; |
| case ICMP_ULE: return Arg1 <= Arg2; |
| case ICMP_SGT: return (S)Arg1 > (S)Arg2; |
| case ICMP_SGE: return (S)Arg1 >= (S)Arg2; |
| case ICMP_SLT: return (S)Arg1 < (S)Arg2; |
| case ICMP_SLE: return (S)Arg1 <= (S)Arg2; |
| default: assert(0 && "unsupported CmpType"); |
| } |
| return false; |
| } |
| |
| static bool ComputeCmp(size_t CmpSize, size_t CmpType, uint64_t Arg1, |
| uint64_t Arg2) { |
| if (CmpSize == 8) return ComputeCmp<uint64_t, int64_t>(CmpType, Arg1, Arg2); |
| if (CmpSize == 4) return ComputeCmp<uint32_t, int32_t>(CmpType, Arg1, Arg2); |
| if (CmpSize == 2) return ComputeCmp<uint16_t, int16_t>(CmpType, Arg1, Arg2); |
| if (CmpSize == 1) return ComputeCmp<uint8_t, int8_t>(CmpType, Arg1, Arg2); |
| assert(0 && "unsupported type size"); |
| return true; |
| } |
| |
| // As a simplification we use the range of input bytes instead of a set of input |
| // bytes. |
| struct LabelRange { |
| uint16_t Beg, End; // Range is [Beg, End), thus Beg==End is an empty range. |
| |
| LabelRange(uint16_t Beg = 0, uint16_t End = 0) : Beg(Beg), End(End) {} |
| |
| static LabelRange Join(LabelRange LR1, LabelRange LR2) { |
| if (LR1.Beg == LR1.End) return LR2; |
| if (LR2.Beg == LR2.End) return LR1; |
| return {std::min(LR1.Beg, LR2.Beg), std::max(LR1.End, LR2.End)}; |
| } |
| LabelRange &Join(LabelRange LR) { |
| return *this = Join(*this, LR); |
| } |
| static LabelRange Singleton(const dfsan_label_info *LI) { |
| uint16_t Idx = (uint16_t)(uintptr_t)LI->userdata; |
| assert(Idx > 0); |
| return {(uint16_t)(Idx - 1), Idx}; |
| } |
| }; |
| |
| // For now, very simple: put Size bytes of Data at position Pos. |
| struct TraceBasedMutation { |
| size_t Pos; |
| size_t Size; |
| uint64_t Data; |
| }; |
| |
| class TraceState { |
| public: |
| TraceState(const Fuzzer::FuzzingOptions &Options, const Unit &CurrentUnit) |
| : Options(Options), CurrentUnit(CurrentUnit) {} |
| |
| LabelRange GetLabelRange(dfsan_label L); |
| void DFSanCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType, |
| uint64_t Arg1, uint64_t Arg2, dfsan_label L1, |
| dfsan_label L2); |
| void TraceCmpCallback(size_t CmpSize, size_t CmpType, uint64_t Arg1, |
| uint64_t Arg2); |
| int TryToAddDesiredData(uint64_t PresentData, uint64_t DesiredData, |
| size_t DataSize); |
| |
| void StartTraceRecording() { |
| if (!Options.UseTraces) return; |
| RecordingTraces = true; |
| Mutations.clear(); |
| } |
| |
| size_t StopTraceRecording() { |
| RecordingTraces = false; |
| std::random_shuffle(Mutations.begin(), Mutations.end()); |
| return Mutations.size(); |
| } |
| |
| void ApplyTraceBasedMutation(size_t Idx, fuzzer::Unit *U); |
| |
| private: |
| bool IsTwoByteData(uint64_t Data) { |
| int64_t Signed = static_cast<int64_t>(Data); |
| Signed >>= 16; |
| return Signed == 0 || Signed == -1L; |
| } |
| bool RecordingTraces = false; |
| std::vector<TraceBasedMutation> Mutations; |
| LabelRange LabelRanges[1 << (sizeof(dfsan_label) * 8)] = {}; |
| const Fuzzer::FuzzingOptions &Options; |
| const Unit &CurrentUnit; |
| }; |
| |
| LabelRange TraceState::GetLabelRange(dfsan_label L) { |
| LabelRange &LR = LabelRanges[L]; |
| if (LR.Beg < LR.End || L == 0) |
| return LR; |
| const dfsan_label_info *LI = dfsan_get_label_info(L); |
| if (LI->l1 || LI->l2) |
| return LR = LabelRange::Join(GetLabelRange(LI->l1), GetLabelRange(LI->l2)); |
| return LR = LabelRange::Singleton(LI); |
| } |
| |
| void TraceState::ApplyTraceBasedMutation(size_t Idx, fuzzer::Unit *U) { |
| assert(Idx < Mutations.size()); |
| auto &M = Mutations[Idx]; |
| if (Options.Verbosity >= 3) |
| Printf("TBM %zd %zd %zd\n", M.Pos, M.Size, M.Data); |
| if (M.Pos + M.Size > U->size()) return; |
| memcpy(U->data() + M.Pos, &M.Data, M.Size); |
| } |
| |
| void TraceState::DFSanCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType, |
| uint64_t Arg1, uint64_t Arg2, dfsan_label L1, |
| dfsan_label L2) { |
| assert(ReallyHaveDFSan()); |
| if (!RecordingTraces) return; |
| if (L1 == 0 && L2 == 0) |
| return; // Not actionable. |
| if (L1 != 0 && L2 != 0) |
| return; // Probably still actionable. |
| bool Res = ComputeCmp(CmpSize, CmpType, Arg1, Arg2); |
| uint64_t Data = L1 ? Arg2 : Arg1; |
| LabelRange LR = L1 ? GetLabelRange(L1) : GetLabelRange(L2); |
| |
| for (size_t Pos = LR.Beg; Pos + CmpSize <= LR.End; Pos++) { |
| Mutations.push_back({Pos, CmpSize, Data}); |
| Mutations.push_back({Pos, CmpSize, Data + 1}); |
| Mutations.push_back({Pos, CmpSize, Data - 1}); |
| } |
| |
| if (CmpSize > LR.End - LR.Beg) |
| Mutations.push_back({LR.Beg, (unsigned)(LR.End - LR.Beg), Data}); |
| |
| |
| if (Options.Verbosity >= 3) |
| Printf("DFSAN: PC %lx S %zd T %zd A1 %llx A2 %llx R %d L1 %d L2 %d MU %zd\n", |
| PC, CmpSize, CmpType, Arg1, Arg2, Res, L1, L2, Mutations.size()); |
| } |
| |
| int TraceState::TryToAddDesiredData(uint64_t PresentData, uint64_t DesiredData, |
| size_t DataSize) { |
| int Res = 0; |
| const uint8_t *Beg = CurrentUnit.data(); |
| const uint8_t *End = Beg + CurrentUnit.size(); |
| for (const uint8_t *Cur = Beg; Cur < End; Cur += DataSize) { |
| Cur = (uint8_t *)memmem(Cur, End - Cur, &PresentData, DataSize); |
| if (!Cur) |
| break; |
| size_t Pos = Cur - Beg; |
| assert(Pos < CurrentUnit.size()); |
| Mutations.push_back({Pos, DataSize, DesiredData}); |
| Mutations.push_back({Pos, DataSize, DesiredData + 1}); |
| Mutations.push_back({Pos, DataSize, DesiredData - 1}); |
| Cur += DataSize; |
| Res++; |
| } |
| return Res; |
| } |
| |
| void TraceState::TraceCmpCallback(size_t CmpSize, size_t CmpType, uint64_t Arg1, |
| uint64_t Arg2) { |
| if (!RecordingTraces) return; |
| int Added = 0; |
| if (Options.Verbosity >= 3) |
| Printf("TraceCmp: %zd %zd\n", Arg1, Arg2); |
| Added += TryToAddDesiredData(Arg1, Arg2, CmpSize); |
| Added += TryToAddDesiredData(Arg2, Arg1, CmpSize); |
| if (!Added && CmpSize == 4 && IsTwoByteData(Arg1) && IsTwoByteData(Arg2)) { |
| Added += TryToAddDesiredData(Arg1, Arg2, 2); |
| Added += TryToAddDesiredData(Arg2, Arg1, 2); |
| } |
| } |
| |
| static TraceState *TS; |
| |
| void Fuzzer::StartTraceRecording() { |
| if (!TS) return; |
| TS->StartTraceRecording(); |
| } |
| |
| size_t Fuzzer::StopTraceRecording() { |
| if (!TS) return 0; |
| return TS->StopTraceRecording(); |
| } |
| |
| void Fuzzer::ApplyTraceBasedMutation(size_t Idx, Unit *U) { |
| assert(TS); |
| TS->ApplyTraceBasedMutation(Idx, U); |
| } |
| |
| void Fuzzer::InitializeTraceState() { |
| if (!Options.UseTraces) return; |
| TS = new TraceState(Options, CurrentUnit); |
| CurrentUnit.resize(Options.MaxLen); |
| // The rest really requires DFSan. |
| if (!ReallyHaveDFSan()) return; |
| for (size_t i = 0; i < static_cast<size_t>(Options.MaxLen); i++) { |
| dfsan_label L = dfsan_create_label("input", (void*)(i + 1)); |
| // We assume that no one else has called dfsan_create_label before. |
| assert(L == i + 1); |
| dfsan_set_label(L, &CurrentUnit[i], 1); |
| } |
| } |
| |
| } // namespace fuzzer |
| |
| using fuzzer::TS; |
| |
| extern "C" { |
| void __dfsw___sanitizer_cov_trace_cmp(uint64_t SizeAndType, uint64_t Arg1, |
| uint64_t Arg2, dfsan_label L0, |
| dfsan_label L1, dfsan_label L2) { |
| if (!TS) return; |
| assert(L0 == 0); |
| uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0)); |
| uint64_t CmpSize = (SizeAndType >> 32) / 8; |
| uint64_t Type = (SizeAndType << 32) >> 32; |
| TS->DFSanCmpCallback(PC, CmpSize, Type, Arg1, Arg2, L1, L2); |
| } |
| |
| void dfsan_weak_hook_memcmp(void *caller_pc, const void *s1, const void *s2, |
| size_t n, dfsan_label s1_label, |
| dfsan_label s2_label, dfsan_label n_label) { |
| if (!TS) return; |
| uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc); |
| uint64_t S1 = 0, S2 = 0; |
| // Simplification: handle only first 8 bytes. |
| memcpy(&S1, s1, std::min(n, sizeof(S1))); |
| memcpy(&S2, s2, std::min(n, sizeof(S2))); |
| dfsan_label L1 = dfsan_read_label(s1, n); |
| dfsan_label L2 = dfsan_read_label(s2, n); |
| TS->DFSanCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2, L1, L2); |
| } |
| |
| void __sanitizer_cov_trace_cmp(uint64_t SizeAndType, uint64_t Arg1, |
| uint64_t Arg2) { |
| if (!TS) return; |
| uint64_t CmpSize = (SizeAndType >> 32) / 8; |
| uint64_t Type = (SizeAndType << 32) >> 32; |
| TS->TraceCmpCallback(CmpSize, Type, Arg1, Arg2); |
| } |
| |
| } // extern "C" |