1 //==- CheckSecuritySyntaxOnly.cpp - Basic security checks --------*- 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 file defines a set of flow-insensitive security checks. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" 14 #include "clang/AST/StmtVisitor.h" 15 #include "clang/Analysis/AnalysisDeclContext.h" 16 #include "clang/Basic/TargetInfo.h" 17 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h" 18 #include "clang/StaticAnalyzer/Core/Checker.h" 19 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h" 20 #include "llvm/ADT/SmallString.h" 21 #include "llvm/ADT/StringSwitch.h" 22 #include "llvm/Support/raw_ostream.h" 23 24 using namespace clang; 25 using namespace ento; 26 27 static bool isArc4RandomAvailable(const ASTContext &Ctx) { 28 const llvm::Triple &T = Ctx.getTargetInfo().getTriple(); 29 return T.getVendor() == llvm::Triple::Apple || 30 T.getOS() == llvm::Triple::CloudABI || 31 T.isOSFreeBSD() || 32 T.isOSNetBSD() || 33 T.isOSOpenBSD() || 34 T.isOSDragonFly(); 35 } 36 37 namespace { 38 struct ChecksFilter { 39 DefaultBool check_bcmp; 40 DefaultBool check_bcopy; 41 DefaultBool check_bzero; 42 DefaultBool check_gets; 43 DefaultBool check_getpw; 44 DefaultBool check_mktemp; 45 DefaultBool check_mkstemp; 46 DefaultBool check_strcpy; 47 DefaultBool check_rand; 48 DefaultBool check_vfork; 49 DefaultBool check_FloatLoopCounter; 50 DefaultBool check_UncheckedReturn; 51 52 CheckName checkName_bcmp; 53 CheckName checkName_bcopy; 54 CheckName checkName_bzero; 55 CheckName checkName_gets; 56 CheckName checkName_getpw; 57 CheckName checkName_mktemp; 58 CheckName checkName_mkstemp; 59 CheckName checkName_strcpy; 60 CheckName checkName_rand; 61 CheckName checkName_vfork; 62 CheckName checkName_FloatLoopCounter; 63 CheckName checkName_UncheckedReturn; 64 }; 65 66 class WalkAST : public StmtVisitor<WalkAST> { 67 BugReporter &BR; 68 AnalysisDeclContext* AC; 69 enum { num_setids = 6 }; 70 IdentifierInfo *II_setid[num_setids]; 71 72 const bool CheckRand; 73 const ChecksFilter &filter; 74 75 public: 76 WalkAST(BugReporter &br, AnalysisDeclContext* ac, 77 const ChecksFilter &f) 78 : BR(br), AC(ac), II_setid(), 79 CheckRand(isArc4RandomAvailable(BR.getContext())), 80 filter(f) {} 81 82 // Statement visitor methods. 83 void VisitCallExpr(CallExpr *CE); 84 void VisitForStmt(ForStmt *S); 85 void VisitCompoundStmt (CompoundStmt *S); 86 void VisitStmt(Stmt *S) { VisitChildren(S); } 87 88 void VisitChildren(Stmt *S); 89 90 // Helpers. 91 bool checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD); 92 93 typedef void (WalkAST::*FnCheck)(const CallExpr *, const FunctionDecl *); 94 95 // Checker-specific methods. 96 void checkLoopConditionForFloat(const ForStmt *FS); 97 void checkCall_bcmp(const CallExpr *CE, const FunctionDecl *FD); 98 void checkCall_bcopy(const CallExpr *CE, const FunctionDecl *FD); 99 void checkCall_bzero(const CallExpr *CE, const FunctionDecl *FD); 100 void checkCall_gets(const CallExpr *CE, const FunctionDecl *FD); 101 void checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD); 102 void checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD); 103 void checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD); 104 void checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD); 105 void checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD); 106 void checkCall_rand(const CallExpr *CE, const FunctionDecl *FD); 107 void checkCall_random(const CallExpr *CE, const FunctionDecl *FD); 108 void checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD); 109 void checkUncheckedReturnValue(CallExpr *CE); 110 }; 111 } // end anonymous namespace 112 113 //===----------------------------------------------------------------------===// 114 // AST walking. 115 //===----------------------------------------------------------------------===// 116 117 void WalkAST::VisitChildren(Stmt *S) { 118 for (Stmt *Child : S->children()) 119 if (Child) 120 Visit(Child); 121 } 122 123 void WalkAST::VisitCallExpr(CallExpr *CE) { 124 // Get the callee. 125 const FunctionDecl *FD = CE->getDirectCallee(); 126 127 if (!FD) 128 return; 129 130 // Get the name of the callee. If it's a builtin, strip off the prefix. 131 IdentifierInfo *II = FD->getIdentifier(); 132 if (!II) // if no identifier, not a simple C function 133 return; 134 StringRef Name = II->getName(); 135 if (Name.startswith("__builtin_")) 136 Name = Name.substr(10); 137 138 // Set the evaluation function by switching on the callee name. 139 FnCheck evalFunction = llvm::StringSwitch<FnCheck>(Name) 140 .Case("bcmp", &WalkAST::checkCall_bcmp) 141 .Case("bcopy", &WalkAST::checkCall_bcopy) 142 .Case("bzero", &WalkAST::checkCall_bzero) 143 .Case("gets", &WalkAST::checkCall_gets) 144 .Case("getpw", &WalkAST::checkCall_getpw) 145 .Case("mktemp", &WalkAST::checkCall_mktemp) 146 .Case("mkstemp", &WalkAST::checkCall_mkstemp) 147 .Case("mkdtemp", &WalkAST::checkCall_mkstemp) 148 .Case("mkstemps", &WalkAST::checkCall_mkstemp) 149 .Cases("strcpy", "__strcpy_chk", &WalkAST::checkCall_strcpy) 150 .Cases("strcat", "__strcat_chk", &WalkAST::checkCall_strcat) 151 .Case("drand48", &WalkAST::checkCall_rand) 152 .Case("erand48", &WalkAST::checkCall_rand) 153 .Case("jrand48", &WalkAST::checkCall_rand) 154 .Case("lrand48", &WalkAST::checkCall_rand) 155 .Case("mrand48", &WalkAST::checkCall_rand) 156 .Case("nrand48", &WalkAST::checkCall_rand) 157 .Case("lcong48", &WalkAST::checkCall_rand) 158 .Case("rand", &WalkAST::checkCall_rand) 159 .Case("rand_r", &WalkAST::checkCall_rand) 160 .Case("random", &WalkAST::checkCall_random) 161 .Case("vfork", &WalkAST::checkCall_vfork) 162 .Default(nullptr); 163 164 // If the callee isn't defined, it is not of security concern. 165 // Check and evaluate the call. 166 if (evalFunction) 167 (this->*evalFunction)(CE, FD); 168 169 // Recurse and check children. 170 VisitChildren(CE); 171 } 172 173 void WalkAST::VisitCompoundStmt(CompoundStmt *S) { 174 for (Stmt *Child : S->children()) 175 if (Child) { 176 if (CallExpr *CE = dyn_cast<CallExpr>(Child)) 177 checkUncheckedReturnValue(CE); 178 Visit(Child); 179 } 180 } 181 182 void WalkAST::VisitForStmt(ForStmt *FS) { 183 checkLoopConditionForFloat(FS); 184 185 // Recurse and check children. 186 VisitChildren(FS); 187 } 188 189 //===----------------------------------------------------------------------===// 190 // Check: floating point variable used as loop counter. 191 // Originally: <rdar://problem/6336718> 192 // Implements: CERT security coding advisory FLP-30. 193 //===----------------------------------------------------------------------===// 194 195 static const DeclRefExpr* 196 getIncrementedVar(const Expr *expr, const VarDecl *x, const VarDecl *y) { 197 expr = expr->IgnoreParenCasts(); 198 199 if (const BinaryOperator *B = dyn_cast<BinaryOperator>(expr)) { 200 if (!(B->isAssignmentOp() || B->isCompoundAssignmentOp() || 201 B->getOpcode() == BO_Comma)) 202 return nullptr; 203 204 if (const DeclRefExpr *lhs = getIncrementedVar(B->getLHS(), x, y)) 205 return lhs; 206 207 if (const DeclRefExpr *rhs = getIncrementedVar(B->getRHS(), x, y)) 208 return rhs; 209 210 return nullptr; 211 } 212 213 if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(expr)) { 214 const NamedDecl *ND = DR->getDecl(); 215 return ND == x || ND == y ? DR : nullptr; 216 } 217 218 if (const UnaryOperator *U = dyn_cast<UnaryOperator>(expr)) 219 return U->isIncrementDecrementOp() 220 ? getIncrementedVar(U->getSubExpr(), x, y) : nullptr; 221 222 return nullptr; 223 } 224 225 /// CheckLoopConditionForFloat - This check looks for 'for' statements that 226 /// use a floating point variable as a loop counter. 227 /// CERT: FLP30-C, FLP30-CPP. 228 /// 229 void WalkAST::checkLoopConditionForFloat(const ForStmt *FS) { 230 if (!filter.check_FloatLoopCounter) 231 return; 232 233 // Does the loop have a condition? 234 const Expr *condition = FS->getCond(); 235 236 if (!condition) 237 return; 238 239 // Does the loop have an increment? 240 const Expr *increment = FS->getInc(); 241 242 if (!increment) 243 return; 244 245 // Strip away '()' and casts. 246 condition = condition->IgnoreParenCasts(); 247 increment = increment->IgnoreParenCasts(); 248 249 // Is the loop condition a comparison? 250 const BinaryOperator *B = dyn_cast<BinaryOperator>(condition); 251 252 if (!B) 253 return; 254 255 // Is this a comparison? 256 if (!(B->isRelationalOp() || B->isEqualityOp())) 257 return; 258 259 // Are we comparing variables? 260 const DeclRefExpr *drLHS = 261 dyn_cast<DeclRefExpr>(B->getLHS()->IgnoreParenLValueCasts()); 262 const DeclRefExpr *drRHS = 263 dyn_cast<DeclRefExpr>(B->getRHS()->IgnoreParenLValueCasts()); 264 265 // Does at least one of the variables have a floating point type? 266 drLHS = drLHS && drLHS->getType()->isRealFloatingType() ? drLHS : nullptr; 267 drRHS = drRHS && drRHS->getType()->isRealFloatingType() ? drRHS : nullptr; 268 269 if (!drLHS && !drRHS) 270 return; 271 272 const VarDecl *vdLHS = drLHS ? dyn_cast<VarDecl>(drLHS->getDecl()) : nullptr; 273 const VarDecl *vdRHS = drRHS ? dyn_cast<VarDecl>(drRHS->getDecl()) : nullptr; 274 275 if (!vdLHS && !vdRHS) 276 return; 277 278 // Does either variable appear in increment? 279 const DeclRefExpr *drInc = getIncrementedVar(increment, vdLHS, vdRHS); 280 281 if (!drInc) 282 return; 283 284 // Emit the error. First figure out which DeclRefExpr in the condition 285 // referenced the compared variable. 286 assert(drInc->getDecl()); 287 const DeclRefExpr *drCond = vdLHS == drInc->getDecl() ? drLHS : drRHS; 288 289 SmallVector<SourceRange, 2> ranges; 290 SmallString<256> sbuf; 291 llvm::raw_svector_ostream os(sbuf); 292 293 os << "Variable '" << drCond->getDecl()->getName() 294 << "' with floating point type '" << drCond->getType().getAsString() 295 << "' should not be used as a loop counter"; 296 297 ranges.push_back(drCond->getSourceRange()); 298 ranges.push_back(drInc->getSourceRange()); 299 300 const char *bugType = "Floating point variable used as loop counter"; 301 302 PathDiagnosticLocation FSLoc = 303 PathDiagnosticLocation::createBegin(FS, BR.getSourceManager(), AC); 304 BR.EmitBasicReport(AC->getDecl(), filter.checkName_FloatLoopCounter, 305 bugType, "Security", os.str(), 306 FSLoc, ranges); 307 } 308 309 //===----------------------------------------------------------------------===// 310 // Check: Any use of bcmp. 311 // CWE-477: Use of Obsolete Functions 312 // bcmp was deprecated in POSIX.1-2008 313 //===----------------------------------------------------------------------===// 314 315 void WalkAST::checkCall_bcmp(const CallExpr *CE, const FunctionDecl *FD) { 316 if (!filter.check_bcmp) 317 return; 318 319 const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); 320 if (!FPT) 321 return; 322 323 // Verify that the function takes three arguments. 324 if (FPT->getNumParams() != 3) 325 return; 326 327 for (int i = 0; i < 2; i++) { 328 // Verify the first and second argument type is void*. 329 const PointerType *PT = FPT->getParamType(i)->getAs<PointerType>(); 330 if (!PT) 331 return; 332 333 if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().VoidTy) 334 return; 335 } 336 337 // Verify the third argument type is integer. 338 if (!FPT->getParamType(2)->isIntegralOrUnscopedEnumerationType()) 339 return; 340 341 // Issue a warning. 342 PathDiagnosticLocation CELoc = 343 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 344 BR.EmitBasicReport(AC->getDecl(), filter.checkName_bcmp, 345 "Use of deprecated function in call to 'bcmp()'", 346 "Security", 347 "The bcmp() function is obsoleted by memcmp().", 348 CELoc, CE->getCallee()->getSourceRange()); 349 } 350 351 //===----------------------------------------------------------------------===// 352 // Check: Any use of bcopy. 353 // CWE-477: Use of Obsolete Functions 354 // bcopy was deprecated in POSIX.1-2008 355 //===----------------------------------------------------------------------===// 356 357 void WalkAST::checkCall_bcopy(const CallExpr *CE, const FunctionDecl *FD) { 358 if (!filter.check_bcopy) 359 return; 360 361 const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); 362 if (!FPT) 363 return; 364 365 // Verify that the function takes three arguments. 366 if (FPT->getNumParams() != 3) 367 return; 368 369 for (int i = 0; i < 2; i++) { 370 // Verify the first and second argument type is void*. 371 const PointerType *PT = FPT->getParamType(i)->getAs<PointerType>(); 372 if (!PT) 373 return; 374 375 if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().VoidTy) 376 return; 377 } 378 379 // Verify the third argument type is integer. 380 if (!FPT->getParamType(2)->isIntegralOrUnscopedEnumerationType()) 381 return; 382 383 // Issue a warning. 384 PathDiagnosticLocation CELoc = 385 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 386 BR.EmitBasicReport(AC->getDecl(), filter.checkName_bcopy, 387 "Use of deprecated function in call to 'bcopy()'", 388 "Security", 389 "The bcopy() function is obsoleted by memcpy() " 390 "or memmove().", 391 CELoc, CE->getCallee()->getSourceRange()); 392 } 393 394 //===----------------------------------------------------------------------===// 395 // Check: Any use of bzero. 396 // CWE-477: Use of Obsolete Functions 397 // bzero was deprecated in POSIX.1-2008 398 //===----------------------------------------------------------------------===// 399 400 void WalkAST::checkCall_bzero(const CallExpr *CE, const FunctionDecl *FD) { 401 if (!filter.check_bzero) 402 return; 403 404 const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); 405 if (!FPT) 406 return; 407 408 // Verify that the function takes two arguments. 409 if (FPT->getNumParams() != 2) 410 return; 411 412 // Verify the first argument type is void*. 413 const PointerType *PT = FPT->getParamType(0)->getAs<PointerType>(); 414 if (!PT) 415 return; 416 417 if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().VoidTy) 418 return; 419 420 // Verify the second argument type is integer. 421 if (!FPT->getParamType(1)->isIntegralOrUnscopedEnumerationType()) 422 return; 423 424 // Issue a warning. 425 PathDiagnosticLocation CELoc = 426 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 427 BR.EmitBasicReport(AC->getDecl(), filter.checkName_bzero, 428 "Use of deprecated function in call to 'bzero()'", 429 "Security", 430 "The bzero() function is obsoleted by memset().", 431 CELoc, CE->getCallee()->getSourceRange()); 432 } 433 434 435 //===----------------------------------------------------------------------===// 436 // Check: Any use of 'gets' is insecure. 437 // Originally: <rdar://problem/6335715> 438 // Implements (part of): 300-BSI (buildsecurityin.us-cert.gov) 439 // CWE-242: Use of Inherently Dangerous Function 440 //===----------------------------------------------------------------------===// 441 442 void WalkAST::checkCall_gets(const CallExpr *CE, const FunctionDecl *FD) { 443 if (!filter.check_gets) 444 return; 445 446 const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); 447 if (!FPT) 448 return; 449 450 // Verify that the function takes a single argument. 451 if (FPT->getNumParams() != 1) 452 return; 453 454 // Is the argument a 'char*'? 455 const PointerType *PT = FPT->getParamType(0)->getAs<PointerType>(); 456 if (!PT) 457 return; 458 459 if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) 460 return; 461 462 // Issue a warning. 463 PathDiagnosticLocation CELoc = 464 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 465 BR.EmitBasicReport(AC->getDecl(), filter.checkName_gets, 466 "Potential buffer overflow in call to 'gets'", 467 "Security", 468 "Call to function 'gets' is extremely insecure as it can " 469 "always result in a buffer overflow", 470 CELoc, CE->getCallee()->getSourceRange()); 471 } 472 473 //===----------------------------------------------------------------------===// 474 // Check: Any use of 'getpwd' is insecure. 475 // CWE-477: Use of Obsolete Functions 476 //===----------------------------------------------------------------------===// 477 478 void WalkAST::checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD) { 479 if (!filter.check_getpw) 480 return; 481 482 const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); 483 if (!FPT) 484 return; 485 486 // Verify that the function takes two arguments. 487 if (FPT->getNumParams() != 2) 488 return; 489 490 // Verify the first argument type is integer. 491 if (!FPT->getParamType(0)->isIntegralOrUnscopedEnumerationType()) 492 return; 493 494 // Verify the second argument type is char*. 495 const PointerType *PT = FPT->getParamType(1)->getAs<PointerType>(); 496 if (!PT) 497 return; 498 499 if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) 500 return; 501 502 // Issue a warning. 503 PathDiagnosticLocation CELoc = 504 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 505 BR.EmitBasicReport(AC->getDecl(), filter.checkName_getpw, 506 "Potential buffer overflow in call to 'getpw'", 507 "Security", 508 "The getpw() function is dangerous as it may overflow the " 509 "provided buffer. It is obsoleted by getpwuid().", 510 CELoc, CE->getCallee()->getSourceRange()); 511 } 512 513 //===----------------------------------------------------------------------===// 514 // Check: Any use of 'mktemp' is insecure. It is obsoleted by mkstemp(). 515 // CWE-377: Insecure Temporary File 516 //===----------------------------------------------------------------------===// 517 518 void WalkAST::checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD) { 519 if (!filter.check_mktemp) { 520 // Fall back to the security check of looking for enough 'X's in the 521 // format string, since that is a less severe warning. 522 checkCall_mkstemp(CE, FD); 523 return; 524 } 525 526 const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); 527 if(!FPT) 528 return; 529 530 // Verify that the function takes a single argument. 531 if (FPT->getNumParams() != 1) 532 return; 533 534 // Verify that the argument is Pointer Type. 535 const PointerType *PT = FPT->getParamType(0)->getAs<PointerType>(); 536 if (!PT) 537 return; 538 539 // Verify that the argument is a 'char*'. 540 if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) 541 return; 542 543 // Issue a warning. 544 PathDiagnosticLocation CELoc = 545 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 546 BR.EmitBasicReport(AC->getDecl(), filter.checkName_mktemp, 547 "Potential insecure temporary file in call 'mktemp'", 548 "Security", 549 "Call to function 'mktemp' is insecure as it always " 550 "creates or uses insecure temporary file. Use 'mkstemp' " 551 "instead", 552 CELoc, CE->getCallee()->getSourceRange()); 553 } 554 555 556 //===----------------------------------------------------------------------===// 557 // Check: Use of 'mkstemp', 'mktemp', 'mkdtemp' should contain at least 6 X's. 558 //===----------------------------------------------------------------------===// 559 560 void WalkAST::checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD) { 561 if (!filter.check_mkstemp) 562 return; 563 564 StringRef Name = FD->getIdentifier()->getName(); 565 std::pair<signed, signed> ArgSuffix = 566 llvm::StringSwitch<std::pair<signed, signed> >(Name) 567 .Case("mktemp", std::make_pair(0,-1)) 568 .Case("mkstemp", std::make_pair(0,-1)) 569 .Case("mkdtemp", std::make_pair(0,-1)) 570 .Case("mkstemps", std::make_pair(0,1)) 571 .Default(std::make_pair(-1, -1)); 572 573 assert(ArgSuffix.first >= 0 && "Unsupported function"); 574 575 // Check if the number of arguments is consistent with out expectations. 576 unsigned numArgs = CE->getNumArgs(); 577 if ((signed) numArgs <= ArgSuffix.first) 578 return; 579 580 const StringLiteral *strArg = 581 dyn_cast<StringLiteral>(CE->getArg((unsigned)ArgSuffix.first) 582 ->IgnoreParenImpCasts()); 583 584 // Currently we only handle string literals. It is possible to do better, 585 // either by looking at references to const variables, or by doing real 586 // flow analysis. 587 if (!strArg || strArg->getCharByteWidth() != 1) 588 return; 589 590 // Count the number of X's, taking into account a possible cutoff suffix. 591 StringRef str = strArg->getString(); 592 unsigned numX = 0; 593 unsigned n = str.size(); 594 595 // Take into account the suffix. 596 unsigned suffix = 0; 597 if (ArgSuffix.second >= 0) { 598 const Expr *suffixEx = CE->getArg((unsigned)ArgSuffix.second); 599 Expr::EvalResult EVResult; 600 if (!suffixEx->EvaluateAsInt(EVResult, BR.getContext())) 601 return; 602 llvm::APSInt Result = EVResult.Val.getInt(); 603 // FIXME: Issue a warning. 604 if (Result.isNegative()) 605 return; 606 suffix = (unsigned) Result.getZExtValue(); 607 n = (n > suffix) ? n - suffix : 0; 608 } 609 610 for (unsigned i = 0; i < n; ++i) 611 if (str[i] == 'X') ++numX; 612 613 if (numX >= 6) 614 return; 615 616 // Issue a warning. 617 PathDiagnosticLocation CELoc = 618 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 619 SmallString<512> buf; 620 llvm::raw_svector_ostream out(buf); 621 out << "Call to '" << Name << "' should have at least 6 'X's in the" 622 " format string to be secure (" << numX << " 'X'"; 623 if (numX != 1) 624 out << 's'; 625 out << " seen"; 626 if (suffix) { 627 out << ", " << suffix << " character"; 628 if (suffix > 1) 629 out << 's'; 630 out << " used as a suffix"; 631 } 632 out << ')'; 633 BR.EmitBasicReport(AC->getDecl(), filter.checkName_mkstemp, 634 "Insecure temporary file creation", "Security", 635 out.str(), CELoc, strArg->getSourceRange()); 636 } 637 638 //===----------------------------------------------------------------------===// 639 // Check: Any use of 'strcpy' is insecure. 640 // 641 // CWE-119: Improper Restriction of Operations within 642 // the Bounds of a Memory Buffer 643 //===----------------------------------------------------------------------===// 644 void WalkAST::checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD) { 645 if (!filter.check_strcpy) 646 return; 647 648 if (!checkCall_strCommon(CE, FD)) 649 return; 650 651 const auto *Target = CE->getArg(0)->IgnoreImpCasts(), 652 *Source = CE->getArg(1)->IgnoreImpCasts(); 653 654 if (const auto *Array = dyn_cast<ConstantArrayType>(Target->getType())) { 655 uint64_t ArraySize = BR.getContext().getTypeSize(Array) / 8; 656 if (const auto *String = dyn_cast<StringLiteral>(Source)) { 657 if (ArraySize >= String->getLength() + 1) 658 return; 659 } 660 } 661 662 // Issue a warning. 663 PathDiagnosticLocation CELoc = 664 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 665 BR.EmitBasicReport(AC->getDecl(), filter.checkName_strcpy, 666 "Potential insecure memory buffer bounds restriction in " 667 "call 'strcpy'", 668 "Security", 669 "Call to function 'strcpy' is insecure as it does not " 670 "provide bounding of the memory buffer. Replace " 671 "unbounded copy functions with analogous functions that " 672 "support length arguments such as 'strlcpy'. CWE-119.", 673 CELoc, CE->getCallee()->getSourceRange()); 674 } 675 676 //===----------------------------------------------------------------------===// 677 // Check: Any use of 'strcat' is insecure. 678 // 679 // CWE-119: Improper Restriction of Operations within 680 // the Bounds of a Memory Buffer 681 //===----------------------------------------------------------------------===// 682 void WalkAST::checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD) { 683 if (!filter.check_strcpy) 684 return; 685 686 if (!checkCall_strCommon(CE, FD)) 687 return; 688 689 // Issue a warning. 690 PathDiagnosticLocation CELoc = 691 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 692 BR.EmitBasicReport(AC->getDecl(), filter.checkName_strcpy, 693 "Potential insecure memory buffer bounds restriction in " 694 "call 'strcat'", 695 "Security", 696 "Call to function 'strcat' is insecure as it does not " 697 "provide bounding of the memory buffer. Replace " 698 "unbounded copy functions with analogous functions that " 699 "support length arguments such as 'strlcat'. CWE-119.", 700 CELoc, CE->getCallee()->getSourceRange()); 701 } 702 703 //===----------------------------------------------------------------------===// 704 // Common check for str* functions with no bounds parameters. 705 //===----------------------------------------------------------------------===// 706 bool WalkAST::checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD) { 707 const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); 708 if (!FPT) 709 return false; 710 711 // Verify the function takes two arguments, three in the _chk version. 712 int numArgs = FPT->getNumParams(); 713 if (numArgs != 2 && numArgs != 3) 714 return false; 715 716 // Verify the type for both arguments. 717 for (int i = 0; i < 2; i++) { 718 // Verify that the arguments are pointers. 719 const PointerType *PT = FPT->getParamType(i)->getAs<PointerType>(); 720 if (!PT) 721 return false; 722 723 // Verify that the argument is a 'char*'. 724 if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) 725 return false; 726 } 727 728 return true; 729 } 730 731 //===----------------------------------------------------------------------===// 732 // Check: Linear congruent random number generators should not be used 733 // Originally: <rdar://problem/63371000> 734 // CWE-338: Use of cryptographically weak prng 735 //===----------------------------------------------------------------------===// 736 737 void WalkAST::checkCall_rand(const CallExpr *CE, const FunctionDecl *FD) { 738 if (!filter.check_rand || !CheckRand) 739 return; 740 741 const FunctionProtoType *FTP = FD->getType()->getAs<FunctionProtoType>(); 742 if (!FTP) 743 return; 744 745 if (FTP->getNumParams() == 1) { 746 // Is the argument an 'unsigned short *'? 747 // (Actually any integer type is allowed.) 748 const PointerType *PT = FTP->getParamType(0)->getAs<PointerType>(); 749 if (!PT) 750 return; 751 752 if (! PT->getPointeeType()->isIntegralOrUnscopedEnumerationType()) 753 return; 754 } else if (FTP->getNumParams() != 0) 755 return; 756 757 // Issue a warning. 758 SmallString<256> buf1; 759 llvm::raw_svector_ostream os1(buf1); 760 os1 << '\'' << *FD << "' is a poor random number generator"; 761 762 SmallString<256> buf2; 763 llvm::raw_svector_ostream os2(buf2); 764 os2 << "Function '" << *FD 765 << "' is obsolete because it implements a poor random number generator." 766 << " Use 'arc4random' instead"; 767 768 PathDiagnosticLocation CELoc = 769 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 770 BR.EmitBasicReport(AC->getDecl(), filter.checkName_rand, os1.str(), 771 "Security", os2.str(), CELoc, 772 CE->getCallee()->getSourceRange()); 773 } 774 775 //===----------------------------------------------------------------------===// 776 // Check: 'random' should not be used 777 // Originally: <rdar://problem/63371000> 778 //===----------------------------------------------------------------------===// 779 780 void WalkAST::checkCall_random(const CallExpr *CE, const FunctionDecl *FD) { 781 if (!CheckRand || !filter.check_rand) 782 return; 783 784 const FunctionProtoType *FTP = FD->getType()->getAs<FunctionProtoType>(); 785 if (!FTP) 786 return; 787 788 // Verify that the function takes no argument. 789 if (FTP->getNumParams() != 0) 790 return; 791 792 // Issue a warning. 793 PathDiagnosticLocation CELoc = 794 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 795 BR.EmitBasicReport(AC->getDecl(), filter.checkName_rand, 796 "'random' is not a secure random number generator", 797 "Security", 798 "The 'random' function produces a sequence of values that " 799 "an adversary may be able to predict. Use 'arc4random' " 800 "instead", CELoc, CE->getCallee()->getSourceRange()); 801 } 802 803 //===----------------------------------------------------------------------===// 804 // Check: 'vfork' should not be used. 805 // POS33-C: Do not use vfork(). 806 //===----------------------------------------------------------------------===// 807 808 void WalkAST::checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD) { 809 if (!filter.check_vfork) 810 return; 811 812 // All calls to vfork() are insecure, issue a warning. 813 PathDiagnosticLocation CELoc = 814 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 815 BR.EmitBasicReport(AC->getDecl(), filter.checkName_vfork, 816 "Potential insecure implementation-specific behavior in " 817 "call 'vfork'", 818 "Security", 819 "Call to function 'vfork' is insecure as it can lead to " 820 "denial of service situations in the parent process. " 821 "Replace calls to vfork with calls to the safer " 822 "'posix_spawn' function", 823 CELoc, CE->getCallee()->getSourceRange()); 824 } 825 826 //===----------------------------------------------------------------------===// 827 // Check: Should check whether privileges are dropped successfully. 828 // Originally: <rdar://problem/6337132> 829 //===----------------------------------------------------------------------===// 830 831 void WalkAST::checkUncheckedReturnValue(CallExpr *CE) { 832 if (!filter.check_UncheckedReturn) 833 return; 834 835 const FunctionDecl *FD = CE->getDirectCallee(); 836 if (!FD) 837 return; 838 839 if (II_setid[0] == nullptr) { 840 static const char * const identifiers[num_setids] = { 841 "setuid", "setgid", "seteuid", "setegid", 842 "setreuid", "setregid" 843 }; 844 845 for (size_t i = 0; i < num_setids; i++) 846 II_setid[i] = &BR.getContext().Idents.get(identifiers[i]); 847 } 848 849 const IdentifierInfo *id = FD->getIdentifier(); 850 size_t identifierid; 851 852 for (identifierid = 0; identifierid < num_setids; identifierid++) 853 if (id == II_setid[identifierid]) 854 break; 855 856 if (identifierid >= num_setids) 857 return; 858 859 const FunctionProtoType *FTP = FD->getType()->getAs<FunctionProtoType>(); 860 if (!FTP) 861 return; 862 863 // Verify that the function takes one or two arguments (depending on 864 // the function). 865 if (FTP->getNumParams() != (identifierid < 4 ? 1 : 2)) 866 return; 867 868 // The arguments must be integers. 869 for (unsigned i = 0; i < FTP->getNumParams(); i++) 870 if (!FTP->getParamType(i)->isIntegralOrUnscopedEnumerationType()) 871 return; 872 873 // Issue a warning. 874 SmallString<256> buf1; 875 llvm::raw_svector_ostream os1(buf1); 876 os1 << "Return value is not checked in call to '" << *FD << '\''; 877 878 SmallString<256> buf2; 879 llvm::raw_svector_ostream os2(buf2); 880 os2 << "The return value from the call to '" << *FD 881 << "' is not checked. If an error occurs in '" << *FD 882 << "', the following code may execute with unexpected privileges"; 883 884 PathDiagnosticLocation CELoc = 885 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 886 BR.EmitBasicReport(AC->getDecl(), filter.checkName_UncheckedReturn, os1.str(), 887 "Security", os2.str(), CELoc, 888 CE->getCallee()->getSourceRange()); 889 } 890 891 //===----------------------------------------------------------------------===// 892 // SecuritySyntaxChecker 893 //===----------------------------------------------------------------------===// 894 895 namespace { 896 class SecuritySyntaxChecker : public Checker<check::ASTCodeBody> { 897 public: 898 ChecksFilter filter; 899 900 void checkASTCodeBody(const Decl *D, AnalysisManager& mgr, 901 BugReporter &BR) const { 902 WalkAST walker(BR, mgr.getAnalysisDeclContext(D), filter); 903 walker.Visit(D->getBody()); 904 } 905 }; 906 } 907 908 void ento::registerSecuritySyntaxChecker(CheckerManager &mgr) { 909 mgr.registerChecker<SecuritySyntaxChecker>(); 910 } 911 912 bool ento::shouldRegisterSecuritySyntaxChecker(const LangOptions &LO) { 913 return true; 914 } 915 916 #define REGISTER_CHECKER(name) \ 917 void ento::register##name(CheckerManager &mgr) { \ 918 SecuritySyntaxChecker *checker = \ 919 mgr.registerChecker<SecuritySyntaxChecker>(); \ 920 checker->filter.check_##name = true; \ 921 checker->filter.checkName_##name = mgr.getCurrentCheckName(); \ 922 } \ 923 \ 924 bool ento::shouldRegister##name(const LangOptions &LO) { \ 925 return true; \ 926 } 927 928 REGISTER_CHECKER(bcmp) 929 REGISTER_CHECKER(bcopy) 930 REGISTER_CHECKER(bzero) 931 REGISTER_CHECKER(gets) 932 REGISTER_CHECKER(getpw) 933 REGISTER_CHECKER(mkstemp) 934 REGISTER_CHECKER(mktemp) 935 REGISTER_CHECKER(strcpy) 936 REGISTER_CHECKER(rand) 937 REGISTER_CHECKER(vfork) 938 REGISTER_CHECKER(FloatLoopCounter) 939 REGISTER_CHECKER(UncheckedReturn) 940 941 942