1 //= UnixAPIChecker.h - Checks preconditions for various Unix APIs --*- C++ -*-// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This defines UnixAPIChecker, which is an assortment of checks on calls 10 // to various, widely used UNIX/Posix functions. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" 15 #include "clang/Basic/TargetInfo.h" 16 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 17 #include "clang/StaticAnalyzer/Core/Checker.h" 18 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 20 #include "llvm/ADT/Optional.h" 21 #include "llvm/ADT/STLExtras.h" 22 #include "llvm/ADT/SmallString.h" 23 #include "llvm/ADT/StringExtras.h" 24 #include "llvm/ADT/StringSwitch.h" 25 #include "llvm/Support/raw_ostream.h" 26 #include <fcntl.h> 27 28 using namespace clang; 29 using namespace ento; 30 31 enum class OpenVariant { 32 /// The standard open() call: 33 /// int open(const char *path, int oflag, ...); 34 Open, 35 36 /// The variant taking a directory file descriptor and a relative path: 37 /// int openat(int fd, const char *path, int oflag, ...); 38 OpenAt 39 }; 40 41 namespace { 42 class UnixAPIChecker : public Checker< check::PreStmt<CallExpr> > { 43 mutable std::unique_ptr<BugType> BT_open, BT_pthreadOnce, BT_mallocZero; 44 mutable Optional<uint64_t> Val_O_CREAT; 45 46 public: 47 DefaultBool CheckMisuse, CheckPortability; 48 49 void checkPreStmt(const CallExpr *CE, CheckerContext &C) const; 50 51 void CheckOpen(CheckerContext &C, const CallExpr *CE) const; 52 void CheckOpenAt(CheckerContext &C, const CallExpr *CE) const; 53 54 void CheckPthreadOnce(CheckerContext &C, const CallExpr *CE) const; 55 void CheckCallocZero(CheckerContext &C, const CallExpr *CE) const; 56 void CheckMallocZero(CheckerContext &C, const CallExpr *CE) const; 57 void CheckReallocZero(CheckerContext &C, const CallExpr *CE) const; 58 void CheckReallocfZero(CheckerContext &C, const CallExpr *CE) const; 59 void CheckAllocaZero(CheckerContext &C, const CallExpr *CE) const; 60 void CheckAllocaWithAlignZero(CheckerContext &C, const CallExpr *CE) const; 61 void CheckVallocZero(CheckerContext &C, const CallExpr *CE) const; 62 63 typedef void (UnixAPIChecker::*SubChecker)(CheckerContext &, 64 const CallExpr *) const; 65 private: 66 67 void CheckOpenVariant(CheckerContext &C, 68 const CallExpr *CE, OpenVariant Variant) const; 69 70 bool ReportZeroByteAllocation(CheckerContext &C, 71 ProgramStateRef falseState, 72 const Expr *arg, 73 const char *fn_name) const; 74 void BasicAllocationCheck(CheckerContext &C, 75 const CallExpr *CE, 76 const unsigned numArgs, 77 const unsigned sizeArg, 78 const char *fn) const; 79 void LazyInitialize(std::unique_ptr<BugType> &BT, const char *name) const { 80 if (BT) 81 return; 82 BT.reset(new BugType(this, name, categories::UnixAPI)); 83 } 84 void ReportOpenBug(CheckerContext &C, 85 ProgramStateRef State, 86 const char *Msg, 87 SourceRange SR) const; 88 }; 89 } //end anonymous namespace 90 91 //===----------------------------------------------------------------------===// 92 // "open" (man 2 open) 93 //===----------------------------------------------------------------------===// 94 95 void UnixAPIChecker::ReportOpenBug(CheckerContext &C, 96 ProgramStateRef State, 97 const char *Msg, 98 SourceRange SR) const { 99 ExplodedNode *N = C.generateErrorNode(State); 100 if (!N) 101 return; 102 103 LazyInitialize(BT_open, "Improper use of 'open'"); 104 105 auto Report = llvm::make_unique<BugReport>(*BT_open, Msg, N); 106 Report->addRange(SR); 107 C.emitReport(std::move(Report)); 108 } 109 110 void UnixAPIChecker::CheckOpen(CheckerContext &C, const CallExpr *CE) const { 111 CheckOpenVariant(C, CE, OpenVariant::Open); 112 } 113 114 void UnixAPIChecker::CheckOpenAt(CheckerContext &C, const CallExpr *CE) const { 115 CheckOpenVariant(C, CE, OpenVariant::OpenAt); 116 } 117 118 void UnixAPIChecker::CheckOpenVariant(CheckerContext &C, 119 const CallExpr *CE, 120 OpenVariant Variant) const { 121 // The index of the argument taking the flags open flags (O_RDONLY, 122 // O_WRONLY, O_CREAT, etc.), 123 unsigned int FlagsArgIndex; 124 const char *VariantName; 125 switch (Variant) { 126 case OpenVariant::Open: 127 FlagsArgIndex = 1; 128 VariantName = "open"; 129 break; 130 case OpenVariant::OpenAt: 131 FlagsArgIndex = 2; 132 VariantName = "openat"; 133 break; 134 }; 135 136 // All calls should at least provide arguments up to the 'flags' parameter. 137 unsigned int MinArgCount = FlagsArgIndex + 1; 138 139 // If the flags has O_CREAT set then open/openat() require an additional 140 // argument specifying the file mode (permission bits) for the created file. 141 unsigned int CreateModeArgIndex = FlagsArgIndex + 1; 142 143 // The create mode argument should be the last argument. 144 unsigned int MaxArgCount = CreateModeArgIndex + 1; 145 146 ProgramStateRef state = C.getState(); 147 148 if (CE->getNumArgs() < MinArgCount) { 149 // The frontend should issue a warning for this case, so this is a sanity 150 // check. 151 return; 152 } else if (CE->getNumArgs() == MaxArgCount) { 153 const Expr *Arg = CE->getArg(CreateModeArgIndex); 154 QualType QT = Arg->getType(); 155 if (!QT->isIntegerType()) { 156 SmallString<256> SBuf; 157 llvm::raw_svector_ostream OS(SBuf); 158 OS << "The " << CreateModeArgIndex + 1 159 << llvm::getOrdinalSuffix(CreateModeArgIndex + 1) 160 << " argument to '" << VariantName << "' is not an integer"; 161 162 ReportOpenBug(C, state, 163 SBuf.c_str(), 164 Arg->getSourceRange()); 165 return; 166 } 167 } else if (CE->getNumArgs() > MaxArgCount) { 168 SmallString<256> SBuf; 169 llvm::raw_svector_ostream OS(SBuf); 170 OS << "Call to '" << VariantName << "' with more than " << MaxArgCount 171 << " arguments"; 172 173 ReportOpenBug(C, state, 174 SBuf.c_str(), 175 CE->getArg(MaxArgCount)->getSourceRange()); 176 return; 177 } 178 179 // The definition of O_CREAT is platform specific. We need a better way 180 // of querying this information from the checking environment. 181 if (!Val_O_CREAT.hasValue()) { 182 if (C.getASTContext().getTargetInfo().getTriple().getVendor() 183 == llvm::Triple::Apple) 184 Val_O_CREAT = 0x0200; 185 else { 186 // FIXME: We need a more general way of getting the O_CREAT value. 187 // We could possibly grovel through the preprocessor state, but 188 // that would require passing the Preprocessor object to the ExprEngine. 189 // See also: MallocChecker.cpp / M_ZERO. 190 return; 191 } 192 } 193 194 // Now check if oflags has O_CREAT set. 195 const Expr *oflagsEx = CE->getArg(FlagsArgIndex); 196 const SVal V = C.getSVal(oflagsEx); 197 if (!V.getAs<NonLoc>()) { 198 // The case where 'V' can be a location can only be due to a bad header, 199 // so in this case bail out. 200 return; 201 } 202 NonLoc oflags = V.castAs<NonLoc>(); 203 NonLoc ocreateFlag = C.getSValBuilder() 204 .makeIntVal(Val_O_CREAT.getValue(), oflagsEx->getType()).castAs<NonLoc>(); 205 SVal maskedFlagsUC = C.getSValBuilder().evalBinOpNN(state, BO_And, 206 oflags, ocreateFlag, 207 oflagsEx->getType()); 208 if (maskedFlagsUC.isUnknownOrUndef()) 209 return; 210 DefinedSVal maskedFlags = maskedFlagsUC.castAs<DefinedSVal>(); 211 212 // Check if maskedFlags is non-zero. 213 ProgramStateRef trueState, falseState; 214 std::tie(trueState, falseState) = state->assume(maskedFlags); 215 216 // Only emit an error if the value of 'maskedFlags' is properly 217 // constrained; 218 if (!(trueState && !falseState)) 219 return; 220 221 if (CE->getNumArgs() < MaxArgCount) { 222 SmallString<256> SBuf; 223 llvm::raw_svector_ostream OS(SBuf); 224 OS << "Call to '" << VariantName << "' requires a " 225 << CreateModeArgIndex + 1 226 << llvm::getOrdinalSuffix(CreateModeArgIndex + 1) 227 << " argument when the 'O_CREAT' flag is set"; 228 ReportOpenBug(C, trueState, 229 SBuf.c_str(), 230 oflagsEx->getSourceRange()); 231 } 232 } 233 234 //===----------------------------------------------------------------------===// 235 // pthread_once 236 //===----------------------------------------------------------------------===// 237 238 void UnixAPIChecker::CheckPthreadOnce(CheckerContext &C, 239 const CallExpr *CE) const { 240 241 // This is similar to 'CheckDispatchOnce' in the MacOSXAPIChecker. 242 // They can possibly be refactored. 243 244 if (CE->getNumArgs() < 1) 245 return; 246 247 // Check if the first argument is stack allocated. If so, issue a warning 248 // because that's likely to be bad news. 249 ProgramStateRef state = C.getState(); 250 const MemRegion *R = C.getSVal(CE->getArg(0)).getAsRegion(); 251 if (!R || !isa<StackSpaceRegion>(R->getMemorySpace())) 252 return; 253 254 ExplodedNode *N = C.generateErrorNode(state); 255 if (!N) 256 return; 257 258 SmallString<256> S; 259 llvm::raw_svector_ostream os(S); 260 os << "Call to 'pthread_once' uses"; 261 if (const VarRegion *VR = dyn_cast<VarRegion>(R)) 262 os << " the local variable '" << VR->getDecl()->getName() << '\''; 263 else 264 os << " stack allocated memory"; 265 os << " for the \"control\" value. Using such transient memory for " 266 "the control value is potentially dangerous."; 267 if (isa<VarRegion>(R) && isa<StackLocalsSpaceRegion>(R->getMemorySpace())) 268 os << " Perhaps you intended to declare the variable as 'static'?"; 269 270 LazyInitialize(BT_pthreadOnce, "Improper use of 'pthread_once'"); 271 272 auto report = llvm::make_unique<BugReport>(*BT_pthreadOnce, os.str(), N); 273 report->addRange(CE->getArg(0)->getSourceRange()); 274 C.emitReport(std::move(report)); 275 } 276 277 //===----------------------------------------------------------------------===// 278 // "calloc", "malloc", "realloc", "reallocf", "alloca" and "valloc" 279 // with allocation size 0 280 //===----------------------------------------------------------------------===// 281 // FIXME: Eventually these should be rolled into the MallocChecker, but right now 282 // they're more basic and valuable for widespread use. 283 284 // Returns true if we try to do a zero byte allocation, false otherwise. 285 // Fills in trueState and falseState. 286 static bool IsZeroByteAllocation(ProgramStateRef state, 287 const SVal argVal, 288 ProgramStateRef *trueState, 289 ProgramStateRef *falseState) { 290 std::tie(*trueState, *falseState) = 291 state->assume(argVal.castAs<DefinedSVal>()); 292 293 return (*falseState && !*trueState); 294 } 295 296 // Generates an error report, indicating that the function whose name is given 297 // will perform a zero byte allocation. 298 // Returns false if an error occurred, true otherwise. 299 bool UnixAPIChecker::ReportZeroByteAllocation(CheckerContext &C, 300 ProgramStateRef falseState, 301 const Expr *arg, 302 const char *fn_name) const { 303 ExplodedNode *N = C.generateErrorNode(falseState); 304 if (!N) 305 return false; 306 307 LazyInitialize(BT_mallocZero, 308 "Undefined allocation of 0 bytes (CERT MEM04-C; CWE-131)"); 309 310 SmallString<256> S; 311 llvm::raw_svector_ostream os(S); 312 os << "Call to '" << fn_name << "' has an allocation size of 0 bytes"; 313 auto report = llvm::make_unique<BugReport>(*BT_mallocZero, os.str(), N); 314 315 report->addRange(arg->getSourceRange()); 316 bugreporter::trackExpressionValue(N, arg, *report); 317 C.emitReport(std::move(report)); 318 319 return true; 320 } 321 322 // Does a basic check for 0-sized allocations suitable for most of the below 323 // functions (modulo "calloc") 324 void UnixAPIChecker::BasicAllocationCheck(CheckerContext &C, 325 const CallExpr *CE, 326 const unsigned numArgs, 327 const unsigned sizeArg, 328 const char *fn) const { 329 // Sanity check for the correct number of arguments 330 if (CE->getNumArgs() != numArgs) 331 return; 332 333 // Check if the allocation size is 0. 334 ProgramStateRef state = C.getState(); 335 ProgramStateRef trueState = nullptr, falseState = nullptr; 336 const Expr *arg = CE->getArg(sizeArg); 337 SVal argVal = C.getSVal(arg); 338 339 if (argVal.isUnknownOrUndef()) 340 return; 341 342 // Is the value perfectly constrained to zero? 343 if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) { 344 (void) ReportZeroByteAllocation(C, falseState, arg, fn); 345 return; 346 } 347 // Assume the value is non-zero going forward. 348 assert(trueState); 349 if (trueState != state) 350 C.addTransition(trueState); 351 } 352 353 void UnixAPIChecker::CheckCallocZero(CheckerContext &C, 354 const CallExpr *CE) const { 355 unsigned int nArgs = CE->getNumArgs(); 356 if (nArgs != 2) 357 return; 358 359 ProgramStateRef state = C.getState(); 360 ProgramStateRef trueState = nullptr, falseState = nullptr; 361 362 unsigned int i; 363 for (i = 0; i < nArgs; i++) { 364 const Expr *arg = CE->getArg(i); 365 SVal argVal = C.getSVal(arg); 366 if (argVal.isUnknownOrUndef()) { 367 if (i == 0) 368 continue; 369 else 370 return; 371 } 372 373 if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) { 374 if (ReportZeroByteAllocation(C, falseState, arg, "calloc")) 375 return; 376 else if (i == 0) 377 continue; 378 else 379 return; 380 } 381 } 382 383 // Assume the value is non-zero going forward. 384 assert(trueState); 385 if (trueState != state) 386 C.addTransition(trueState); 387 } 388 389 void UnixAPIChecker::CheckMallocZero(CheckerContext &C, 390 const CallExpr *CE) const { 391 BasicAllocationCheck(C, CE, 1, 0, "malloc"); 392 } 393 394 void UnixAPIChecker::CheckReallocZero(CheckerContext &C, 395 const CallExpr *CE) const { 396 BasicAllocationCheck(C, CE, 2, 1, "realloc"); 397 } 398 399 void UnixAPIChecker::CheckReallocfZero(CheckerContext &C, 400 const CallExpr *CE) const { 401 BasicAllocationCheck(C, CE, 2, 1, "reallocf"); 402 } 403 404 void UnixAPIChecker::CheckAllocaZero(CheckerContext &C, 405 const CallExpr *CE) const { 406 BasicAllocationCheck(C, CE, 1, 0, "alloca"); 407 } 408 409 void UnixAPIChecker::CheckAllocaWithAlignZero(CheckerContext &C, 410 const CallExpr *CE) const { 411 BasicAllocationCheck(C, CE, 2, 0, "__builtin_alloca_with_align"); 412 } 413 414 void UnixAPIChecker::CheckVallocZero(CheckerContext &C, 415 const CallExpr *CE) const { 416 BasicAllocationCheck(C, CE, 1, 0, "valloc"); 417 } 418 419 420 //===----------------------------------------------------------------------===// 421 // Central dispatch function. 422 //===----------------------------------------------------------------------===// 423 424 void UnixAPIChecker::checkPreStmt(const CallExpr *CE, 425 CheckerContext &C) const { 426 const FunctionDecl *FD = C.getCalleeDecl(CE); 427 if (!FD || FD->getKind() != Decl::Function) 428 return; 429 430 // Don't treat functions in namespaces with the same name a Unix function 431 // as a call to the Unix function. 432 const DeclContext *NamespaceCtx = FD->getEnclosingNamespaceContext(); 433 if (NamespaceCtx && isa<NamespaceDecl>(NamespaceCtx)) 434 return; 435 436 StringRef FName = C.getCalleeName(FD); 437 if (FName.empty()) 438 return; 439 440 if (CheckMisuse) { 441 if (SubChecker SC = 442 llvm::StringSwitch<SubChecker>(FName) 443 .Case("open", &UnixAPIChecker::CheckOpen) 444 .Case("openat", &UnixAPIChecker::CheckOpenAt) 445 .Case("pthread_once", &UnixAPIChecker::CheckPthreadOnce) 446 .Default(nullptr)) { 447 (this->*SC)(C, CE); 448 } 449 } 450 if (CheckPortability) { 451 if (SubChecker SC = 452 llvm::StringSwitch<SubChecker>(FName) 453 .Case("calloc", &UnixAPIChecker::CheckCallocZero) 454 .Case("malloc", &UnixAPIChecker::CheckMallocZero) 455 .Case("realloc", &UnixAPIChecker::CheckReallocZero) 456 .Case("reallocf", &UnixAPIChecker::CheckReallocfZero) 457 .Cases("alloca", "__builtin_alloca", 458 &UnixAPIChecker::CheckAllocaZero) 459 .Case("__builtin_alloca_with_align", 460 &UnixAPIChecker::CheckAllocaWithAlignZero) 461 .Case("valloc", &UnixAPIChecker::CheckVallocZero) 462 .Default(nullptr)) { 463 (this->*SC)(C, CE); 464 } 465 } 466 } 467 468 //===----------------------------------------------------------------------===// 469 // Registration. 470 //===----------------------------------------------------------------------===// 471 472 #define REGISTER_CHECKER(Name) \ 473 void ento::registerUnixAPI##Name##Checker(CheckerManager &mgr) { \ 474 mgr.registerChecker<UnixAPIChecker>()->Check##Name = true; \ 475 } 476 477 REGISTER_CHECKER(Misuse) 478 REGISTER_CHECKER(Portability) 479