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