forked from OSchip/llvm-project
276 lines
10 KiB
C++
276 lines
10 KiB
C++
//===- FuzzerDFSan.cpp - DFSan-based fuzzer mutator -----------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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// DataFlowSanitizer (DFSan) is a tool for
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// generalised dynamic data flow (taint) analysis:
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// http://clang.llvm.org/docs/DataFlowSanitizer.html .
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//
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// This file implements a mutation algorithm based on taint
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// analysis feedback from DFSan.
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//
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// The approach has some similarity to "Taint-based Directed Whitebox Fuzzing"
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// by Vijay Ganesh & Tim Leek & Martin Rinard:
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// http://dspace.mit.edu/openaccess-disseminate/1721.1/59320,
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// but it uses a full blown LLVM IR taint analysis and separate instrumentation
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// to analyze all of the "attack points" at once.
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//
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// Workflow:
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// * lib/Fuzzer/Fuzzer*.cpp is compiled w/o any instrumentation.
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// * The code under test is compiled with DFSan *and* with special extra hooks
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// that are inserted before dfsan. Currently supported hooks:
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// - __sanitizer_cov_trace_cmp: inserted before every ICMP instruction,
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// receives the type, size and arguments of ICMP.
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// * Every call to HOOK(a,b) is replaced by DFSan with
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// __dfsw_HOOK(a, b, label(a), label(b)) so that __dfsw_HOOK
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// gets all the taint labels for the arguments.
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// * At the Fuzzer startup we assign a unique DFSan label
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// to every byte of the input string (Fuzzer::CurrentUnit) so that for any
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// chunk of data we know which input bytes it has derived from.
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// * The __dfsw_* functions (implemented in this file) record the
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// parameters (i.e. the application data and the corresponding taint labels)
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// in a global state.
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// * Fuzzer::MutateWithDFSan() tries to use the data recorded by __dfsw_*
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// hooks to guide the fuzzing towards new application states.
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// For example if 4 bytes of data that derive from input bytes {4,5,6,7}
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// are compared with a constant 12345 and the comparison always yields
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// the same result, we try to insert 12345, 12344, 12346 into bytes
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// {4,5,6,7} of the next fuzzed inputs.
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//
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// This code does not function when DFSan is not linked in.
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// Instead of using ifdefs and thus requiring a separate build of lib/Fuzzer
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// we redeclare the dfsan_* interface functions as weak and check if they
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// are nullptr before calling.
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// If this approach proves to be useful we may add attribute(weak) to the
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// dfsan declarations in dfsan_interface.h
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//
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// This module is in the "proof of concept" stage.
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// It is capable of solving only the simplest puzzles
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// like test/dfsan/DFSanSimpleCmpTest.cpp.
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//===----------------------------------------------------------------------===//
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/* Example of manual usage:
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(
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cd $LLVM/lib/Fuzzer/
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clang -fPIC -c -g -O2 -std=c++11 Fuzzer*.cpp
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clang++ -O0 -std=c++11 -fsanitize-coverage=3 \
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-mllvm -sanitizer-coverage-experimental-trace-compares=1 \
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-fsanitize=dataflow -fsanitize-blacklist=./dfsan_fuzzer_abi.list \
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test/dfsan/DFSanSimpleCmpTest.cpp Fuzzer*.o
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./a.out
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)
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*/
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#include "FuzzerInternal.h"
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#include <sanitizer/dfsan_interface.h>
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#include <cstring>
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#include <iostream>
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#include <unordered_map>
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extern "C" {
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__attribute__((weak))
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dfsan_label dfsan_create_label(const char *desc, void *userdata);
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__attribute__((weak))
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void dfsan_set_label(dfsan_label label, void *addr, size_t size);
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__attribute__((weak))
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void dfsan_add_label(dfsan_label label, void *addr, size_t size);
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__attribute__((weak))
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const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label);
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} // extern "C"
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namespace {
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// These values are copied from include/llvm/IR/InstrTypes.h.
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// We do not include the LLVM headers here to remain independent.
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// If these values ever change, an assertion in ComputeCmp will fail.
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enum Predicate {
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ICMP_EQ = 32, ///< equal
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ICMP_NE = 33, ///< not equal
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ICMP_UGT = 34, ///< unsigned greater than
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ICMP_UGE = 35, ///< unsigned greater or equal
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ICMP_ULT = 36, ///< unsigned less than
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ICMP_ULE = 37, ///< unsigned less or equal
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ICMP_SGT = 38, ///< signed greater than
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ICMP_SGE = 39, ///< signed greater or equal
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ICMP_SLT = 40, ///< signed less than
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ICMP_SLE = 41, ///< signed less or equal
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};
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template <class U, class S>
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bool ComputeCmp(size_t CmpType, U Arg1, U Arg2) {
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switch(CmpType) {
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case ICMP_EQ : return Arg1 == Arg2;
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case ICMP_NE : return Arg1 != Arg2;
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case ICMP_UGT: return Arg1 > Arg2;
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case ICMP_UGE: return Arg1 >= Arg2;
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case ICMP_ULT: return Arg1 < Arg2;
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case ICMP_ULE: return Arg1 <= Arg2;
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case ICMP_SGT: return (S)Arg1 > (S)Arg2;
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case ICMP_SGE: return (S)Arg1 >= (S)Arg2;
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case ICMP_SLT: return (S)Arg1 < (S)Arg2;
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case ICMP_SLE: return (S)Arg1 <= (S)Arg2;
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default: assert(0 && "unsupported CmpType");
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}
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return false;
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}
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static bool ComputeCmp(size_t CmpSize, size_t CmpType, uint64_t Arg1,
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uint64_t Arg2) {
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if (CmpSize == 8) return ComputeCmp<uint64_t, int64_t>(CmpType, Arg1, Arg2);
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if (CmpSize == 4) return ComputeCmp<uint32_t, int32_t>(CmpType, Arg1, Arg2);
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if (CmpSize == 2) return ComputeCmp<uint16_t, int16_t>(CmpType, Arg1, Arg2);
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if (CmpSize == 1) return ComputeCmp<uint8_t, int8_t>(CmpType, Arg1, Arg2);
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assert(0 && "unsupported type size");
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return true;
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}
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// As a simplification we use the range of input bytes instead of a set of input
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// bytes.
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struct LabelRange {
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uint16_t Beg, End; // Range is [Beg, End), thus Beg==End is an empty range.
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LabelRange(uint16_t Beg = 0, uint16_t End = 0) : Beg(Beg), End(End) {}
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static LabelRange Join(LabelRange LR1, LabelRange LR2) {
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if (LR1.Beg == LR1.End) return LR2;
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if (LR2.Beg == LR2.End) return LR1;
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return {std::min(LR1.Beg, LR2.Beg), std::max(LR1.End, LR2.End)};
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}
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LabelRange &Join(LabelRange LR) {
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return *this = Join(*this, LR);
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}
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static LabelRange Singleton(const dfsan_label_info *LI) {
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uint16_t Idx = (uint16_t)(uintptr_t)LI->userdata;
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assert(Idx > 0);
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return {(uint16_t)(Idx - 1), Idx};
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}
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};
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std::ostream &operator<<(std::ostream &os, const LabelRange &LR) {
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return os << "[" << LR.Beg << "," << LR.End << ")";
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}
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class DFSanState {
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public:
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DFSanState(const fuzzer::Fuzzer::FuzzingOptions &Options)
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: Options(Options) {}
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struct CmpSiteInfo {
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size_t ResCounters[2] = {0, 0};
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size_t CmpSize = 0;
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LabelRange LR;
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std::unordered_map<uint64_t, size_t> CountedConstants;
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};
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LabelRange GetLabelRange(dfsan_label L);
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void DFSanCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType,
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uint64_t Arg1, uint64_t Arg2, dfsan_label L1,
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dfsan_label L2);
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bool Mutate(fuzzer::Unit *U);
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private:
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std::unordered_map<uintptr_t, CmpSiteInfo> PcToCmpSiteInfoMap;
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LabelRange LabelRanges[1 << (sizeof(dfsan_label) * 8)] = {};
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const fuzzer::Fuzzer::FuzzingOptions &Options;
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};
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LabelRange DFSanState::GetLabelRange(dfsan_label L) {
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LabelRange &LR = LabelRanges[L];
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if (LR.Beg < LR.End || L == 0)
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return LR;
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const dfsan_label_info *LI = dfsan_get_label_info(L);
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if (LI->l1 || LI->l2)
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return LR = LabelRange::Join(GetLabelRange(LI->l1), GetLabelRange(LI->l2));
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return LR = LabelRange::Singleton(LI);
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}
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void DFSanState::DFSanCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType,
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uint64_t Arg1, uint64_t Arg2, dfsan_label L1,
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dfsan_label L2) {
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if (L1 == 0 && L2 == 0)
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return; // Not actionable.
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if (L1 != 0 && L2 != 0)
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return; // Probably still actionable.
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bool Res = ComputeCmp(CmpSize, CmpType, Arg1, Arg2);
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CmpSiteInfo &CSI = PcToCmpSiteInfoMap[PC];
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CSI.CmpSize = CmpSize;
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CSI.LR.Join(GetLabelRange(L1)).Join(GetLabelRange(L2));
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if (!L1) CSI.CountedConstants[Arg1]++;
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if (!L2) CSI.CountedConstants[Arg2]++;
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size_t Counter = CSI.ResCounters[Res]++;
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if (Options.Verbosity >= 2 &&
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(Counter & (Counter - 1)) == 0 &&
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CSI.ResCounters[!Res] == 0)
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std::cerr << "DFSAN:"
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<< " PC " << std::hex << PC << std::dec
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<< " S " << CmpSize
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<< " T " << CmpType
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<< " A1 " << Arg1 << " A2 " << Arg2 << " R " << Res
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<< " L" << L1 << GetLabelRange(L1)
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<< " L" << L2 << GetLabelRange(L2)
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<< " LR " << CSI.LR
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<< "\n";
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}
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bool DFSanState::Mutate(fuzzer::Unit *U) {
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for (auto &PCToCmp : PcToCmpSiteInfoMap) {
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auto &CSI = PCToCmp.second;
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if (CSI.ResCounters[0] * CSI.ResCounters[1] != 0) continue;
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if (CSI.ResCounters[0] + CSI.ResCounters[1] < 1000) continue;
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if (CSI.CountedConstants.size() != 1) continue;
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uintptr_t C = CSI.CountedConstants.begin()->first;
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if (U->size() >= CSI.CmpSize) {
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size_t RangeSize = CSI.LR.End - CSI.LR.Beg;
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size_t Idx = CSI.LR.Beg + rand() % RangeSize;
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if (Idx + CSI.CmpSize > U->size()) continue;
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C += rand() % 5 - 2;
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memcpy(U->data() + Idx, &C, CSI.CmpSize);
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return true;
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}
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}
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return false;
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}
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static DFSanState *DFSan;
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} // namespace
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namespace fuzzer {
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bool Fuzzer::MutateWithDFSan(Unit *U) {
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if (!&dfsan_create_label || !DFSan) return false;
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return DFSan->Mutate(U);
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}
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void Fuzzer::InitializeDFSan() {
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if (!&dfsan_create_label || !Options.UseDFSan) return;
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DFSan = new DFSanState(Options);
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CurrentUnit.resize(Options.MaxLen);
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for (size_t i = 0; i < static_cast<size_t>(Options.MaxLen); i++) {
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dfsan_label L = dfsan_create_label("input", (void*)(i + 1));
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// We assume that no one else has called dfsan_create_label before.
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assert(L == i + 1);
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dfsan_set_label(L, &CurrentUnit[i], 1);
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}
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}
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} // namespace fuzzer
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extern "C" {
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void __dfsw___sanitizer_cov_trace_cmp(uint64_t SizeAndType, uint64_t Arg1,
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uint64_t Arg2, dfsan_label L0,
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dfsan_label L1, dfsan_label L2) {
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assert(L0 == 0);
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uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
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uint64_t CmpSize = (SizeAndType >> 32) / 8;
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uint64_t Type = (SizeAndType << 32) >> 32;
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DFSan->DFSanCmpCallback(PC, CmpSize, Type, Arg1, Arg2, L1, L2);
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}
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} // extern "C"
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