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| //===-- llvm-cfi-verify.cpp - CFI Verification tool for LLVM --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This tool verifies Control Flow Integrity (CFI) instrumentation by static
// binary anaylsis. See the design document in /docs/CFIVerify.rst for more
// information.
//
// This tool is currently incomplete. It currently only does disassembly for
// object files, and searches through the code for indirect control flow
// instructions, printing them once found.
//
//===----------------------------------------------------------------------===//
#include "lib/FileAnalysis.h"
#include "lib/GraphBuilder.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/FormatVariadic.h"
#include "llvm/Support/SpecialCaseList.h"
#include <cstdlib>
using namespace llvm;
using namespace llvm::object;
using namespace llvm::cfi_verify;
cl::opt<std::string> InputFilename(cl::Positional, cl::desc("<input file>"),
cl::Required);
cl::opt<std::string> BlacklistFilename(cl::Positional,
cl::desc("[blacklist file]"),
cl::init("-"));
cl::opt<bool> PrintGraphs(
"print-graphs",
cl::desc("Print graphs around indirect CF instructions in DOT format."),
cl::init(false));
cl::opt<unsigned> PrintBlameContext(
"blame-context",
cl::desc("Print the blame context (if possible) for BAD instructions. This "
"specifies the number of lines of context to include, where zero "
"disables this feature."),
cl::init(0));
cl::opt<unsigned> PrintBlameContextAll(
"blame-context-all",
cl::desc("Prints the blame context (if possible) for ALL instructions. "
"This specifies the number of lines of context for non-BAD "
"instructions (see --blame-context). If --blame-context is "
"unspecified, it prints this number of contextual lines for BAD "
"instructions as well."),
cl::init(0));
cl::opt<bool> Summarize("summarize", cl::desc("Print the summary only."),
cl::init(false));
ExitOnError ExitOnErr;
void printBlameContext(const DILineInfo &LineInfo, unsigned Context) {
auto FileOrErr = MemoryBuffer::getFile(LineInfo.FileName);
if (!FileOrErr) {
errs() << "Could not open file: " << LineInfo.FileName << "\n";
return;
}
std::unique_ptr<MemoryBuffer> File = std::move(FileOrErr.get());
SmallVector<StringRef, 100> Lines;
File->getBuffer().split(Lines, '\n');
for (unsigned i = std::max<size_t>(1, LineInfo.Line - Context);
i <
std::min<size_t>(Lines.size() + 1, LineInfo.Line + Context + 1);
++i) {
if (i == LineInfo.Line)
outs() << ">";
else
outs() << " ";
outs() << i << ": " << Lines[i - 1] << "\n";
}
}
void printInstructionInformation(const FileAnalysis &Analysis,
const Instr &InstrMeta,
const GraphResult &Graph,
CFIProtectionStatus ProtectionStatus) {
outs() << "Instruction: " << format_hex(InstrMeta.VMAddress, 2) << " ("
<< stringCFIProtectionStatus(ProtectionStatus) << "): ";
Analysis.printInstruction(InstrMeta, outs());
outs() << " \n";
if (PrintGraphs)
Graph.printToDOT(Analysis, outs());
}
void printInstructionStatus(unsigned BlameLine, bool CFIProtected,
const DILineInfo &LineInfo) {
if (BlameLine) {
outs() << "Blacklist Match: " << BlacklistFilename << ":" << BlameLine
<< "\n";
if (CFIProtected)
outs() << "====> Unexpected Protected\n";
else
outs() << "====> Expected Unprotected\n";
if (PrintBlameContextAll)
printBlameContext(LineInfo, PrintBlameContextAll);
} else {
if (CFIProtected) {
outs() << "====> Expected Protected\n";
if (PrintBlameContextAll)
printBlameContext(LineInfo, PrintBlameContextAll);
} else {
outs() << "====> Unexpected Unprotected (BAD)\n";
if (PrintBlameContext)
printBlameContext(LineInfo, PrintBlameContext);
}
}
}
void printIndirectCFInstructions(FileAnalysis &Analysis,
const SpecialCaseList *SpecialCaseList) {
uint64_t ExpectedProtected = 0;
uint64_t UnexpectedProtected = 0;
uint64_t ExpectedUnprotected = 0;
uint64_t UnexpectedUnprotected = 0;
std::map<unsigned, uint64_t> BlameCounter;
for (object::SectionedAddress Address : Analysis.getIndirectInstructions()) {
const auto &InstrMeta = Analysis.getInstructionOrDie(Address.Address);
GraphResult Graph = GraphBuilder::buildFlowGraph(Analysis, Address);
CFIProtectionStatus ProtectionStatus =
Analysis.validateCFIProtection(Graph);
bool CFIProtected = (ProtectionStatus == CFIProtectionStatus::PROTECTED);
if (!Summarize) {
outs() << "-----------------------------------------------------\n";
printInstructionInformation(Analysis, InstrMeta, Graph, ProtectionStatus);
}
if (IgnoreDWARFFlag) {
if (CFIProtected)
ExpectedProtected++;
else
UnexpectedUnprotected++;
continue;
}
auto InliningInfo = Analysis.symbolizeInlinedCode(Address);
if (!InliningInfo || InliningInfo->getNumberOfFrames() == 0) {
errs() << "Failed to symbolise " << format_hex(Address.Address, 2)
<< " with line tables from " << InputFilename << "\n";
exit(EXIT_FAILURE);
}
const auto &LineInfo = InliningInfo->getFrame(0);
// Print the inlining symbolisation of this instruction.
if (!Summarize) {
for (uint32_t i = 0; i < InliningInfo->getNumberOfFrames(); ++i) {
const auto &Line = InliningInfo->getFrame(i);
outs() << " " << format_hex(Address.Address, 2) << " = "
<< Line.FileName << ":" << Line.Line << ":" << Line.Column
<< " (" << Line.FunctionName << ")\n";
}
}
if (!SpecialCaseList) {
if (CFIProtected) {
if (PrintBlameContextAll && !Summarize)
printBlameContext(LineInfo, PrintBlameContextAll);
ExpectedProtected++;
} else {
if (PrintBlameContext && !Summarize)
printBlameContext(LineInfo, PrintBlameContext);
UnexpectedUnprotected++;
}
continue;
}
unsigned BlameLine = 0;
for (auto &K : {"cfi-icall", "cfi-vcall"}) {
if (!BlameLine)
BlameLine =
SpecialCaseList->inSectionBlame(K, "src", LineInfo.FileName);
if (!BlameLine)
BlameLine =
SpecialCaseList->inSectionBlame(K, "fun", LineInfo.FunctionName);
}
if (BlameLine) {
BlameCounter[BlameLine]++;
if (CFIProtected)
UnexpectedProtected++;
else
ExpectedUnprotected++;
} else {
if (CFIProtected)
ExpectedProtected++;
else
UnexpectedUnprotected++;
}
if (!Summarize)
printInstructionStatus(BlameLine, CFIProtected, LineInfo);
}
uint64_t IndirectCFInstructions = ExpectedProtected + UnexpectedProtected +
ExpectedUnprotected + UnexpectedUnprotected;
if (IndirectCFInstructions == 0) {
outs() << "No indirect CF instructions found.\n";
return;
}
outs() << formatv("\nTotal Indirect CF Instructions: {0}\n"
"Expected Protected: {1} ({2:P})\n"
"Unexpected Protected: {3} ({4:P})\n"
"Expected Unprotected: {5} ({6:P})\n"
"Unexpected Unprotected (BAD): {7} ({8:P})\n",
IndirectCFInstructions, ExpectedProtected,
((double)ExpectedProtected) / IndirectCFInstructions,
UnexpectedProtected,
((double)UnexpectedProtected) / IndirectCFInstructions,
ExpectedUnprotected,
((double)ExpectedUnprotected) / IndirectCFInstructions,
UnexpectedUnprotected,
((double)UnexpectedUnprotected) / IndirectCFInstructions);
if (!SpecialCaseList)
return;
outs() << "\nBlacklist Results:\n";
for (const auto &KV : BlameCounter) {
outs() << " " << BlacklistFilename << ":" << KV.first << " affects "
<< KV.second << " indirect CF instructions.\n";
}
}
int main(int argc, char **argv) {
cl::ParseCommandLineOptions(
argc, argv,
"Identifies whether Control Flow Integrity protects all indirect control "
"flow instructions in the provided object file, DSO or binary.\nNote: "
"Anything statically linked into the provided file *must* be compiled "
"with '-g'. This can be relaxed through the '--ignore-dwarf' flag.");
InitializeAllTargetInfos();
InitializeAllTargetMCs();
InitializeAllAsmParsers();
InitializeAllDisassemblers();
if (PrintBlameContextAll && !PrintBlameContext)
PrintBlameContext.setValue(PrintBlameContextAll);
std::unique_ptr<SpecialCaseList> SpecialCaseList;
if (BlacklistFilename != "-") {
std::string Error;
SpecialCaseList = SpecialCaseList::create({BlacklistFilename}, Error);
if (!SpecialCaseList) {
errs() << "Failed to get blacklist: " << Error << "\n";
exit(EXIT_FAILURE);
}
}
FileAnalysis Analysis = ExitOnErr(FileAnalysis::Create(InputFilename));
printIndirectCFInstructions(Analysis, SpecialCaseList.get());
return EXIT_SUCCESS;
}
|