1 //= UnixAPIChecker.h - Checks preconditions for various Unix APIs --*- C++ -*-// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This defines UnixAPIChecker, which is an assortment of checks on calls 11 // to various, widely used UNIX/Posix functions. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "ClangSACheckers.h" 16 #include "clang/Basic/TargetInfo.h" 17 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 18 #include "clang/StaticAnalyzer/Core/Checker.h" 19 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 20 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 21 #include "llvm/ADT/Optional.h" 22 #include "llvm/ADT/STLExtras.h" 23 #include "llvm/ADT/SmallString.h" 24 #include "llvm/ADT/StringExtras.h" 25 #include "llvm/ADT/StringSwitch.h" 26 #include "llvm/Support/raw_ostream.h" 27 #include <fcntl.h> 28 29 using namespace clang; 30 using namespace ento; 31 32 enum class OpenVariant { 33 /// The standard open() call: 34 /// int open(const char *path, int oflag, ...); 35 Open, 36 37 /// The variant taking a directory file descriptor and a relative path: 38 /// int openat(int fd, const char *path, int oflag, ...); 39 OpenAt 40 }; 41 42 namespace { 43 class UnixAPIChecker : public Checker< check::PreStmt<CallExpr> > { 44 mutable std::unique_ptr<BugType> BT_open, BT_pthreadOnce, BT_mallocZero; 45 mutable Optional<uint64_t> Val_O_CREAT; 46 47 public: 48 DefaultBool CheckMisuse, CheckPortability; 49 50 void checkPreStmt(const CallExpr *CE, CheckerContext &C) const; 51 52 void CheckOpen(CheckerContext &C, const CallExpr *CE) const; 53 void CheckOpenAt(CheckerContext &C, const CallExpr *CE) const; 54 55 void CheckPthreadOnce(CheckerContext &C, const CallExpr *CE) const; 56 void CheckCallocZero(CheckerContext &C, const CallExpr *CE) const; 57 void CheckMallocZero(CheckerContext &C, const CallExpr *CE) const; 58 void CheckReallocZero(CheckerContext &C, const CallExpr *CE) const; 59 void CheckReallocfZero(CheckerContext &C, const CallExpr *CE) const; 60 void CheckAllocaZero(CheckerContext &C, const CallExpr *CE) const; 61 void CheckAllocaWithAlignZero(CheckerContext &C, const CallExpr *CE) const; 62 void CheckVallocZero(CheckerContext &C, const CallExpr *CE) const; 63 64 typedef void (UnixAPIChecker::*SubChecker)(CheckerContext &, 65 const CallExpr *) const; 66 private: 67 68 void CheckOpenVariant(CheckerContext &C, 69 const CallExpr *CE, OpenVariant Variant) const; 70 71 bool ReportZeroByteAllocation(CheckerContext &C, 72 ProgramStateRef falseState, 73 const Expr *arg, 74 const char *fn_name) const; 75 void BasicAllocationCheck(CheckerContext &C, 76 const CallExpr *CE, 77 const unsigned numArgs, 78 const unsigned sizeArg, 79 const char *fn) const; 80 void LazyInitialize(std::unique_ptr<BugType> &BT, const char *name) const { 81 if (BT) 82 return; 83 BT.reset(new BugType(this, name, categories::UnixAPI)); 84 } 85 void ReportOpenBug(CheckerContext &C, 86 ProgramStateRef State, 87 const char *Msg, 88 SourceRange SR) const; 89 }; 90 } //end anonymous namespace 91 92 //===----------------------------------------------------------------------===// 93 // "open" (man 2 open) 94 //===----------------------------------------------------------------------===// 95 96 void UnixAPIChecker::ReportOpenBug(CheckerContext &C, 97 ProgramStateRef State, 98 const char *Msg, 99 SourceRange SR) const { 100 ExplodedNode *N = C.generateErrorNode(State); 101 if (!N) 102 return; 103 104 LazyInitialize(BT_open, "Improper use of 'open'"); 105 106 auto Report = llvm::make_unique<BugReport>(*BT_open, Msg, N); 107 Report->addRange(SR); 108 C.emitReport(std::move(Report)); 109 } 110 111 void UnixAPIChecker::CheckOpen(CheckerContext &C, const CallExpr *CE) const { 112 CheckOpenVariant(C, CE, OpenVariant::Open); 113 } 114 115 void UnixAPIChecker::CheckOpenAt(CheckerContext &C, const CallExpr *CE) const { 116 CheckOpenVariant(C, CE, OpenVariant::OpenAt); 117 } 118 119 void UnixAPIChecker::CheckOpenVariant(CheckerContext &C, 120 const CallExpr *CE, 121 OpenVariant Variant) const { 122 // The index of the argument taking the flags open flags (O_RDONLY, 123 // O_WRONLY, O_CREAT, etc.), 124 unsigned int FlagsArgIndex; 125 const char *VariantName; 126 switch (Variant) { 127 case OpenVariant::Open: 128 FlagsArgIndex = 1; 129 VariantName = "open"; 130 break; 131 case OpenVariant::OpenAt: 132 FlagsArgIndex = 2; 133 VariantName = "openat"; 134 break; 135 }; 136 137 // All calls should at least provide arguments up to the 'flags' parameter. 138 unsigned int MinArgCount = FlagsArgIndex + 1; 139 140 // If the flags has O_CREAT set then open/openat() require an additional 141 // argument specifying the file mode (permission bits) for the created file. 142 unsigned int CreateModeArgIndex = FlagsArgIndex + 1; 143 144 // The create mode argument should be the last argument. 145 unsigned int MaxArgCount = CreateModeArgIndex + 1; 146 147 ProgramStateRef state = C.getState(); 148 149 if (CE->getNumArgs() < MinArgCount) { 150 // The frontend should issue a warning for this case, so this is a sanity 151 // check. 152 return; 153 } else if (CE->getNumArgs() == MaxArgCount) { 154 const Expr *Arg = CE->getArg(CreateModeArgIndex); 155 QualType QT = Arg->getType(); 156 if (!QT->isIntegerType()) { 157 SmallString<256> SBuf; 158 llvm::raw_svector_ostream OS(SBuf); 159 OS << "The " << CreateModeArgIndex + 1 160 << llvm::getOrdinalSuffix(CreateModeArgIndex + 1) 161 << " argument to '" << VariantName << "' is not an integer"; 162 163 ReportOpenBug(C, state, 164 SBuf.c_str(), 165 Arg->getSourceRange()); 166 return; 167 } 168 } else if (CE->getNumArgs() > MaxArgCount) { 169 SmallString<256> SBuf; 170 llvm::raw_svector_ostream OS(SBuf); 171 OS << "Call to '" << VariantName << "' with more than " << MaxArgCount 172 << " arguments"; 173 174 ReportOpenBug(C, state, 175 SBuf.c_str(), 176 CE->getArg(MaxArgCount)->getSourceRange()); 177 return; 178 } 179 180 // The definition of O_CREAT is platform specific. We need a better way 181 // of querying this information from the checking environment. 182 if (!Val_O_CREAT.hasValue()) { 183 if (C.getASTContext().getTargetInfo().getTriple().getVendor() 184 == llvm::Triple::Apple) 185 Val_O_CREAT = 0x0200; 186 else { 187 // FIXME: We need a more general way of getting the O_CREAT value. 188 // We could possibly grovel through the preprocessor state, but 189 // that would require passing the Preprocessor object to the ExprEngine. 190 // See also: MallocChecker.cpp / M_ZERO. 191 return; 192 } 193 } 194 195 // Now check if oflags has O_CREAT set. 196 const Expr *oflagsEx = CE->getArg(FlagsArgIndex); 197 const SVal V = C.getSVal(oflagsEx); 198 if (!V.getAs<NonLoc>()) { 199 // The case where 'V' can be a location can only be due to a bad header, 200 // so in this case bail out. 201 return; 202 } 203 NonLoc oflags = V.castAs<NonLoc>(); 204 NonLoc ocreateFlag = C.getSValBuilder() 205 .makeIntVal(Val_O_CREAT.getValue(), oflagsEx->getType()).castAs<NonLoc>(); 206 SVal maskedFlagsUC = C.getSValBuilder().evalBinOpNN(state, BO_And, 207 oflags, ocreateFlag, 208 oflagsEx->getType()); 209 if (maskedFlagsUC.isUnknownOrUndef()) 210 return; 211 DefinedSVal maskedFlags = maskedFlagsUC.castAs<DefinedSVal>(); 212 213 // Check if maskedFlags is non-zero. 214 ProgramStateRef trueState, falseState; 215 std::tie(trueState, falseState) = state->assume(maskedFlags); 216 217 // Only emit an error if the value of 'maskedFlags' is properly 218 // constrained; 219 if (!(trueState && !falseState)) 220 return; 221 222 if (CE->getNumArgs() < MaxArgCount) { 223 SmallString<256> SBuf; 224 llvm::raw_svector_ostream OS(SBuf); 225 OS << "Call to '" << VariantName << "' requires a " 226 << CreateModeArgIndex + 1 227 << llvm::getOrdinalSuffix(CreateModeArgIndex + 1) 228 << " argument when the 'O_CREAT' flag is set"; 229 ReportOpenBug(C, trueState, 230 SBuf.c_str(), 231 oflagsEx->getSourceRange()); 232 } 233 } 234 235 //===----------------------------------------------------------------------===// 236 // pthread_once 237 //===----------------------------------------------------------------------===// 238 239 void UnixAPIChecker::CheckPthreadOnce(CheckerContext &C, 240 const CallExpr *CE) const { 241 242 // This is similar to 'CheckDispatchOnce' in the MacOSXAPIChecker. 243 // They can possibly be refactored. 244 245 if (CE->getNumArgs() < 1) 246 return; 247 248 // Check if the first argument is stack allocated. If so, issue a warning 249 // because that's likely to be bad news. 250 ProgramStateRef state = C.getState(); 251 const MemRegion *R = C.getSVal(CE->getArg(0)).getAsRegion(); 252 if (!R || !isa<StackSpaceRegion>(R->getMemorySpace())) 253 return; 254 255 ExplodedNode *N = C.generateErrorNode(state); 256 if (!N) 257 return; 258 259 SmallString<256> S; 260 llvm::raw_svector_ostream os(S); 261 os << "Call to 'pthread_once' uses"; 262 if (const VarRegion *VR = dyn_cast<VarRegion>(R)) 263 os << " the local variable '" << VR->getDecl()->getName() << '\''; 264 else 265 os << " stack allocated memory"; 266 os << " for the \"control\" value. Using such transient memory for " 267 "the control value is potentially dangerous."; 268 if (isa<VarRegion>(R) && isa<StackLocalsSpaceRegion>(R->getMemorySpace())) 269 os << " Perhaps you intended to declare the variable as 'static'?"; 270 271 LazyInitialize(BT_pthreadOnce, "Improper use of 'pthread_once'"); 272 273 auto report = llvm::make_unique<BugReport>(*BT_pthreadOnce, os.str(), N); 274 report->addRange(CE->getArg(0)->getSourceRange()); 275 C.emitReport(std::move(report)); 276 } 277 278 //===----------------------------------------------------------------------===// 279 // "calloc", "malloc", "realloc", "reallocf", "alloca" and "valloc" 280 // with allocation size 0 281 //===----------------------------------------------------------------------===// 282 // FIXME: Eventually these should be rolled into the MallocChecker, but right now 283 // they're more basic and valuable for widespread use. 284 285 // Returns true if we try to do a zero byte allocation, false otherwise. 286 // Fills in trueState and falseState. 287 static bool IsZeroByteAllocation(ProgramStateRef state, 288 const SVal argVal, 289 ProgramStateRef *trueState, 290 ProgramStateRef *falseState) { 291 std::tie(*trueState, *falseState) = 292 state->assume(argVal.castAs<DefinedSVal>()); 293 294 return (*falseState && !*trueState); 295 } 296 297 // Generates an error report, indicating that the function whose name is given 298 // will perform a zero byte allocation. 299 // Returns false if an error occurred, true otherwise. 300 bool UnixAPIChecker::ReportZeroByteAllocation(CheckerContext &C, 301 ProgramStateRef falseState, 302 const Expr *arg, 303 const char *fn_name) const { 304 ExplodedNode *N = C.generateErrorNode(falseState); 305 if (!N) 306 return false; 307 308 LazyInitialize(BT_mallocZero, 309 "Undefined allocation of 0 bytes (CERT MEM04-C; CWE-131)"); 310 311 SmallString<256> S; 312 llvm::raw_svector_ostream os(S); 313 os << "Call to '" << fn_name << "' has an allocation size of 0 bytes"; 314 auto report = llvm::make_unique<BugReport>(*BT_mallocZero, os.str(), N); 315 316 report->addRange(arg->getSourceRange()); 317 bugreporter::trackExpressionValue(N, arg, *report); 318 C.emitReport(std::move(report)); 319 320 return true; 321 } 322 323 // Does a basic check for 0-sized allocations suitable for most of the below 324 // functions (modulo "calloc") 325 void UnixAPIChecker::BasicAllocationCheck(CheckerContext &C, 326 const CallExpr *CE, 327 const unsigned numArgs, 328 const unsigned sizeArg, 329 const char *fn) const { 330 // Sanity check for the correct number of arguments 331 if (CE->getNumArgs() != numArgs) 332 return; 333 334 // Check if the allocation size is 0. 335 ProgramStateRef state = C.getState(); 336 ProgramStateRef trueState = nullptr, falseState = nullptr; 337 const Expr *arg = CE->getArg(sizeArg); 338 SVal argVal = C.getSVal(arg); 339 340 if (argVal.isUnknownOrUndef()) 341 return; 342 343 // Is the value perfectly constrained to zero? 344 if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) { 345 (void) ReportZeroByteAllocation(C, falseState, arg, fn); 346 return; 347 } 348 // Assume the value is non-zero going forward. 349 assert(trueState); 350 if (trueState != state) 351 C.addTransition(trueState); 352 } 353 354 void UnixAPIChecker::CheckCallocZero(CheckerContext &C, 355 const CallExpr *CE) const { 356 unsigned int nArgs = CE->getNumArgs(); 357 if (nArgs != 2) 358 return; 359 360 ProgramStateRef state = C.getState(); 361 ProgramStateRef trueState = nullptr, falseState = nullptr; 362 363 unsigned int i; 364 for (i = 0; i < nArgs; i++) { 365 const Expr *arg = CE->getArg(i); 366 SVal argVal = C.getSVal(arg); 367 if (argVal.isUnknownOrUndef()) { 368 if (i == 0) 369 continue; 370 else 371 return; 372 } 373 374 if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) { 375 if (ReportZeroByteAllocation(C, falseState, arg, "calloc")) 376 return; 377 else if (i == 0) 378 continue; 379 else 380 return; 381 } 382 } 383 384 // Assume the value is non-zero going forward. 385 assert(trueState); 386 if (trueState != state) 387 C.addTransition(trueState); 388 } 389 390 void UnixAPIChecker::CheckMallocZero(CheckerContext &C, 391 const CallExpr *CE) const { 392 BasicAllocationCheck(C, CE, 1, 0, "malloc"); 393 } 394 395 void UnixAPIChecker::CheckReallocZero(CheckerContext &C, 396 const CallExpr *CE) const { 397 BasicAllocationCheck(C, CE, 2, 1, "realloc"); 398 } 399 400 void UnixAPIChecker::CheckReallocfZero(CheckerContext &C, 401 const CallExpr *CE) const { 402 BasicAllocationCheck(C, CE, 2, 1, "reallocf"); 403 } 404 405 void UnixAPIChecker::CheckAllocaZero(CheckerContext &C, 406 const CallExpr *CE) const { 407 BasicAllocationCheck(C, CE, 1, 0, "alloca"); 408 } 409 410 void UnixAPIChecker::CheckAllocaWithAlignZero(CheckerContext &C, 411 const CallExpr *CE) const { 412 BasicAllocationCheck(C, CE, 2, 0, "__builtin_alloca_with_align"); 413 } 414 415 void UnixAPIChecker::CheckVallocZero(CheckerContext &C, 416 const CallExpr *CE) const { 417 BasicAllocationCheck(C, CE, 1, 0, "valloc"); 418 } 419 420 421 //===----------------------------------------------------------------------===// 422 // Central dispatch function. 423 //===----------------------------------------------------------------------===// 424 425 void UnixAPIChecker::checkPreStmt(const CallExpr *CE, 426 CheckerContext &C) const { 427 const FunctionDecl *FD = C.getCalleeDecl(CE); 428 if (!FD || FD->getKind() != Decl::Function) 429 return; 430 431 // Don't treat functions in namespaces with the same name a Unix function 432 // as a call to the Unix function. 433 const DeclContext *NamespaceCtx = FD->getEnclosingNamespaceContext(); 434 if (NamespaceCtx && isa<NamespaceDecl>(NamespaceCtx)) 435 return; 436 437 StringRef FName = C.getCalleeName(FD); 438 if (FName.empty()) 439 return; 440 441 if (CheckMisuse) { 442 if (SubChecker SC = 443 llvm::StringSwitch<SubChecker>(FName) 444 .Case("open", &UnixAPIChecker::CheckOpen) 445 .Case("openat", &UnixAPIChecker::CheckOpenAt) 446 .Case("pthread_once", &UnixAPIChecker::CheckPthreadOnce) 447 .Default(nullptr)) { 448 (this->*SC)(C, CE); 449 } 450 } 451 if (CheckPortability) { 452 if (SubChecker SC = 453 llvm::StringSwitch<SubChecker>(FName) 454 .Case("calloc", &UnixAPIChecker::CheckCallocZero) 455 .Case("malloc", &UnixAPIChecker::CheckMallocZero) 456 .Case("realloc", &UnixAPIChecker::CheckReallocZero) 457 .Case("reallocf", &UnixAPIChecker::CheckReallocfZero) 458 .Cases("alloca", "__builtin_alloca", 459 &UnixAPIChecker::CheckAllocaZero) 460 .Case("__builtin_alloca_with_align", 461 &UnixAPIChecker::CheckAllocaWithAlignZero) 462 .Case("valloc", &UnixAPIChecker::CheckVallocZero) 463 .Default(nullptr)) { 464 (this->*SC)(C, CE); 465 } 466 } 467 } 468 469 //===----------------------------------------------------------------------===// 470 // Registration. 471 //===----------------------------------------------------------------------===// 472 473 #define REGISTER_CHECKER(Name) \ 474 void ento::registerUnixAPI##Name##Checker(CheckerManager &mgr) { \ 475 mgr.registerChecker<UnixAPIChecker>()->Check##Name = true; \ 476 } 477 478 REGISTER_CHECKER(Misuse) 479 REGISTER_CHECKER(Portability) 480