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//===-- llvm-cfi-verify.cpp - CFI Verification tool for LLVM --------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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));
ExitOnError ExitOnErr;
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 (uint64_t Address : Analysis.getIndirectInstructions()) {
const auto &InstrMeta = Analysis.getInstructionOrDie(Address);
GraphResult Graph = GraphBuilder::buildFlowGraph(Analysis, Address);
CFIProtectionStatus ProtectionStatus =
Analysis.validateCFIProtection(Graph);
bool CFIProtected = (ProtectionStatus == CFIProtectionStatus::PROTECTED);
if (CFIProtected)
outs() << "P ";
else
outs() << "U ";
outs() << format_hex(Address, 2) << " | ";
Analysis.printInstruction(InstrMeta, outs());
outs() << " \n";
if (PrintGraphs)
Graph.printToDOT(Analysis, outs());
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, 2)
<< " with line tables from " << InputFilename << "\n";
exit(EXIT_FAILURE);
}
const auto &LineInfo =
InliningInfo->getFrame(InliningInfo->getNumberOfFrames() - 1);
// Print the inlining symbolisation of this instruction.
for (uint32_t i = 0; i < InliningInfo->getNumberOfFrames(); ++i) {
const auto &Line = InliningInfo->getFrame(i);
outs() << " " << format_hex(Address, 2) << " = " << Line.FileName << ":"
<< Line.Line << ":" << Line.Column << " (" << Line.FunctionName
<< ")\n";
}
if (!SpecialCaseList) {
if (CFIProtected)
ExpectedProtected++;
else
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) {
outs() << "Blacklist Match: " << BlacklistFilename << ":" << BlameLine
<< "\n";
BlameCounter[BlameLine]++;
if (CFIProtected) {
UnexpectedProtected++;
outs() << "====> Unexpected Protected\n";
} else {
ExpectedUnprotected++;
outs() << "====> Expected Unprotected\n";
}
} else {
if (CFIProtected) {
ExpectedProtected++;
outs() << "====> Expected Protected\n";
} else {
UnexpectedUnprotected++;
outs() << "====> Unexpected Unprotected\n";
}
}
}
uint64_t IndirectCFInstructions = ExpectedProtected + UnexpectedProtected +
ExpectedUnprotected + UnexpectedUnprotected;
if (IndirectCFInstructions == 0) {
outs() << "No indirect CF instructions found.\n";
return;
}
outs() << formatv("Expected Protected: {0} ({1:P})\n"
"Unexpected Protected: {2} ({3:P})\n"
"Expected Unprotected: {4} ({5:P})\n"
"Unexpected Unprotected (BAD): {6} ({7:P})\n",
ExpectedProtected,
((double)ExpectedProtected) / IndirectCFInstructions,
UnexpectedProtected,
((double)UnexpectedProtected) / IndirectCFInstructions,
ExpectedUnprotected,
((double)ExpectedUnprotected) / IndirectCFInstructions,
UnexpectedUnprotected,
((double)UnexpectedUnprotected) / IndirectCFInstructions);
if (!SpecialCaseList)
return;
outs() << "Blacklist 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();
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;
}
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