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/Analysis/AnalysisContext.h" 16 #include "clang/AST/StmtVisitor.h" 17 #include "clang/Basic/TargetInfo.h" 18 #include "clang/StaticAnalyzer/Core/Checker.h" 19 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.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::FreeBSD || 32 T.getOS() == llvm::Triple::NetBSD || 33 T.getOS() == llvm::Triple::OpenBSD || 34 T.getOS() == llvm::Triple::DragonFly; 35 } 36 37 namespace { 38 struct DefaultBool { 39 bool val; 40 DefaultBool() : val(false) {} 41 operator bool() const { return val; } 42 DefaultBool &operator=(bool b) { val = b; return *this; } 43 }; 44 45 struct ChecksFilter { 46 DefaultBool check_gets; 47 DefaultBool check_getpw; 48 DefaultBool check_mktemp; 49 DefaultBool check_mkstemp; 50 DefaultBool check_strcpy; 51 DefaultBool check_rand; 52 DefaultBool check_vfork; 53 DefaultBool check_FloatLoopCounter; 54 DefaultBool check_UncheckedReturn; 55 }; 56 57 class WalkAST : public StmtVisitor<WalkAST> { 58 BugReporter &BR; 59 AnalysisDeclContext* AC; 60 enum { num_setids = 6 }; 61 IdentifierInfo *II_setid[num_setids]; 62 63 const bool CheckRand; 64 const ChecksFilter &filter; 65 66 public: 67 WalkAST(BugReporter &br, AnalysisDeclContext* ac, 68 const ChecksFilter &f) 69 : BR(br), AC(ac), II_setid(), 70 CheckRand(isArc4RandomAvailable(BR.getContext())), 71 filter(f) {} 72 73 // Statement visitor methods. 74 void VisitCallExpr(CallExpr *CE); 75 void VisitForStmt(ForStmt *S); 76 void VisitCompoundStmt (CompoundStmt *S); 77 void VisitStmt(Stmt *S) { VisitChildren(S); } 78 79 void VisitChildren(Stmt *S); 80 81 // Helpers. 82 bool checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD); 83 84 typedef void (WalkAST::*FnCheck)(const CallExpr *, 85 const FunctionDecl *); 86 87 // Checker-specific methods. 88 void checkLoopConditionForFloat(const ForStmt *FS); 89 void checkCall_gets(const CallExpr *CE, const FunctionDecl *FD); 90 void checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD); 91 void checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD); 92 void checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD); 93 void checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD); 94 void checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD); 95 void checkCall_rand(const CallExpr *CE, const FunctionDecl *FD); 96 void checkCall_random(const CallExpr *CE, const FunctionDecl *FD); 97 void checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD); 98 void checkUncheckedReturnValue(CallExpr *CE); 99 }; 100 } // end anonymous namespace 101 102 //===----------------------------------------------------------------------===// 103 // AST walking. 104 //===----------------------------------------------------------------------===// 105 106 void WalkAST::VisitChildren(Stmt *S) { 107 for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I) 108 if (Stmt *child = *I) 109 Visit(child); 110 } 111 112 void WalkAST::VisitCallExpr(CallExpr *CE) { 113 // Get the callee. 114 const FunctionDecl *FD = CE->getDirectCallee(); 115 116 if (!FD) 117 return; 118 119 // Get the name of the callee. If it's a builtin, strip off the prefix. 120 IdentifierInfo *II = FD->getIdentifier(); 121 if (!II) // if no identifier, not a simple C function 122 return; 123 StringRef Name = II->getName(); 124 if (Name.startswith("__builtin_")) 125 Name = Name.substr(10); 126 127 // Set the evaluation function by switching on the callee name. 128 FnCheck evalFunction = llvm::StringSwitch<FnCheck>(Name) 129 .Case("gets", &WalkAST::checkCall_gets) 130 .Case("getpw", &WalkAST::checkCall_getpw) 131 .Case("mktemp", &WalkAST::checkCall_mktemp) 132 .Case("mkstemp", &WalkAST::checkCall_mkstemp) 133 .Case("mkdtemp", &WalkAST::checkCall_mkstemp) 134 .Case("mkstemps", &WalkAST::checkCall_mkstemp) 135 .Cases("strcpy", "__strcpy_chk", &WalkAST::checkCall_strcpy) 136 .Cases("strcat", "__strcat_chk", &WalkAST::checkCall_strcat) 137 .Case("drand48", &WalkAST::checkCall_rand) 138 .Case("erand48", &WalkAST::checkCall_rand) 139 .Case("jrand48", &WalkAST::checkCall_rand) 140 .Case("lrand48", &WalkAST::checkCall_rand) 141 .Case("mrand48", &WalkAST::checkCall_rand) 142 .Case("nrand48", &WalkAST::checkCall_rand) 143 .Case("lcong48", &WalkAST::checkCall_rand) 144 .Case("rand", &WalkAST::checkCall_rand) 145 .Case("rand_r", &WalkAST::checkCall_rand) 146 .Case("random", &WalkAST::checkCall_random) 147 .Case("vfork", &WalkAST::checkCall_vfork) 148 .Default(NULL); 149 150 // If the callee isn't defined, it is not of security concern. 151 // Check and evaluate the call. 152 if (evalFunction) 153 (this->*evalFunction)(CE, FD); 154 155 // Recurse and check children. 156 VisitChildren(CE); 157 } 158 159 void WalkAST::VisitCompoundStmt(CompoundStmt *S) { 160 for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I) 161 if (Stmt *child = *I) { 162 if (CallExpr *CE = dyn_cast<CallExpr>(child)) 163 checkUncheckedReturnValue(CE); 164 Visit(child); 165 } 166 } 167 168 void WalkAST::VisitForStmt(ForStmt *FS) { 169 checkLoopConditionForFloat(FS); 170 171 // Recurse and check children. 172 VisitChildren(FS); 173 } 174 175 //===----------------------------------------------------------------------===// 176 // Check: floating poing variable used as loop counter. 177 // Originally: <rdar://problem/6336718> 178 // Implements: CERT security coding advisory FLP-30. 179 //===----------------------------------------------------------------------===// 180 181 static const DeclRefExpr* 182 getIncrementedVar(const Expr *expr, const VarDecl *x, const VarDecl *y) { 183 expr = expr->IgnoreParenCasts(); 184 185 if (const BinaryOperator *B = dyn_cast<BinaryOperator>(expr)) { 186 if (!(B->isAssignmentOp() || B->isCompoundAssignmentOp() || 187 B->getOpcode() == BO_Comma)) 188 return NULL; 189 190 if (const DeclRefExpr *lhs = getIncrementedVar(B->getLHS(), x, y)) 191 return lhs; 192 193 if (const DeclRefExpr *rhs = getIncrementedVar(B->getRHS(), x, y)) 194 return rhs; 195 196 return NULL; 197 } 198 199 if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(expr)) { 200 const NamedDecl *ND = DR->getDecl(); 201 return ND == x || ND == y ? DR : NULL; 202 } 203 204 if (const UnaryOperator *U = dyn_cast<UnaryOperator>(expr)) 205 return U->isIncrementDecrementOp() 206 ? getIncrementedVar(U->getSubExpr(), x, y) : NULL; 207 208 return NULL; 209 } 210 211 /// CheckLoopConditionForFloat - This check looks for 'for' statements that 212 /// use a floating point variable as a loop counter. 213 /// CERT: FLP30-C, FLP30-CPP. 214 /// 215 void WalkAST::checkLoopConditionForFloat(const ForStmt *FS) { 216 if (!filter.check_FloatLoopCounter) 217 return; 218 219 // Does the loop have a condition? 220 const Expr *condition = FS->getCond(); 221 222 if (!condition) 223 return; 224 225 // Does the loop have an increment? 226 const Expr *increment = FS->getInc(); 227 228 if (!increment) 229 return; 230 231 // Strip away '()' and casts. 232 condition = condition->IgnoreParenCasts(); 233 increment = increment->IgnoreParenCasts(); 234 235 // Is the loop condition a comparison? 236 const BinaryOperator *B = dyn_cast<BinaryOperator>(condition); 237 238 if (!B) 239 return; 240 241 // Is this a comparison? 242 if (!(B->isRelationalOp() || B->isEqualityOp())) 243 return; 244 245 // Are we comparing variables? 246 const DeclRefExpr *drLHS = 247 dyn_cast<DeclRefExpr>(B->getLHS()->IgnoreParenLValueCasts()); 248 const DeclRefExpr *drRHS = 249 dyn_cast<DeclRefExpr>(B->getRHS()->IgnoreParenLValueCasts()); 250 251 // Does at least one of the variables have a floating point type? 252 drLHS = drLHS && drLHS->getType()->isRealFloatingType() ? drLHS : NULL; 253 drRHS = drRHS && drRHS->getType()->isRealFloatingType() ? drRHS : NULL; 254 255 if (!drLHS && !drRHS) 256 return; 257 258 const VarDecl *vdLHS = drLHS ? dyn_cast<VarDecl>(drLHS->getDecl()) : NULL; 259 const VarDecl *vdRHS = drRHS ? dyn_cast<VarDecl>(drRHS->getDecl()) : NULL; 260 261 if (!vdLHS && !vdRHS) 262 return; 263 264 // Does either variable appear in increment? 265 const DeclRefExpr *drInc = getIncrementedVar(increment, vdLHS, vdRHS); 266 267 if (!drInc) 268 return; 269 270 // Emit the error. First figure out which DeclRefExpr in the condition 271 // referenced the compared variable. 272 const DeclRefExpr *drCond = vdLHS == drInc->getDecl() ? drLHS : drRHS; 273 274 SmallVector<SourceRange, 2> ranges; 275 SmallString<256> sbuf; 276 llvm::raw_svector_ostream os(sbuf); 277 278 os << "Variable '" << drCond->getDecl()->getName() 279 << "' with floating point type '" << drCond->getType().getAsString() 280 << "' should not be used as a loop counter"; 281 282 ranges.push_back(drCond->getSourceRange()); 283 ranges.push_back(drInc->getSourceRange()); 284 285 const char *bugType = "Floating point variable used as loop counter"; 286 287 PathDiagnosticLocation FSLoc = 288 PathDiagnosticLocation::createBegin(FS, BR.getSourceManager(), AC); 289 BR.EmitBasicReport(AC->getDecl(), 290 bugType, "Security", os.str(), 291 FSLoc, ranges.data(), ranges.size()); 292 } 293 294 //===----------------------------------------------------------------------===// 295 // Check: Any use of 'gets' is insecure. 296 // Originally: <rdar://problem/6335715> 297 // Implements (part of): 300-BSI (buildsecurityin.us-cert.gov) 298 // CWE-242: Use of Inherently Dangerous Function 299 //===----------------------------------------------------------------------===// 300 301 void WalkAST::checkCall_gets(const CallExpr *CE, const FunctionDecl *FD) { 302 if (!filter.check_gets) 303 return; 304 305 const FunctionProtoType *FPT 306 = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens()); 307 if (!FPT) 308 return; 309 310 // Verify that the function takes a single argument. 311 if (FPT->getNumArgs() != 1) 312 return; 313 314 // Is the argument a 'char*'? 315 const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(0)); 316 if (!PT) 317 return; 318 319 if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) 320 return; 321 322 // Issue a warning. 323 SourceRange R = CE->getCallee()->getSourceRange(); 324 PathDiagnosticLocation CELoc = 325 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 326 BR.EmitBasicReport(AC->getDecl(), 327 "Potential buffer overflow in call to 'gets'", 328 "Security", 329 "Call to function 'gets' is extremely insecure as it can " 330 "always result in a buffer overflow", 331 CELoc, &R, 1); 332 } 333 334 //===----------------------------------------------------------------------===// 335 // Check: Any use of 'getpwd' is insecure. 336 // CWE-477: Use of Obsolete Functions 337 //===----------------------------------------------------------------------===// 338 339 void WalkAST::checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD) { 340 if (!filter.check_getpw) 341 return; 342 343 const FunctionProtoType *FPT 344 = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens()); 345 if (!FPT) 346 return; 347 348 // Verify that the function takes two arguments. 349 if (FPT->getNumArgs() != 2) 350 return; 351 352 // Verify the first argument type is integer. 353 if (!FPT->getArgType(0)->isIntegerType()) 354 return; 355 356 // Verify the second argument type is char*. 357 const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(1)); 358 if (!PT) 359 return; 360 361 if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) 362 return; 363 364 // Issue a warning. 365 SourceRange R = CE->getCallee()->getSourceRange(); 366 PathDiagnosticLocation CELoc = 367 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 368 BR.EmitBasicReport(AC->getDecl(), 369 "Potential buffer overflow in call to 'getpw'", 370 "Security", 371 "The getpw() function is dangerous as it may overflow the " 372 "provided buffer. It is obsoleted by getpwuid().", 373 CELoc, &R, 1); 374 } 375 376 //===----------------------------------------------------------------------===// 377 // Check: Any use of 'mktemp' is insecure. It is obsoleted by mkstemp(). 378 // CWE-377: Insecure Temporary File 379 //===----------------------------------------------------------------------===// 380 381 void WalkAST::checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD) { 382 if (!filter.check_mktemp) { 383 // Fall back to the security check of looking for enough 'X's in the 384 // format string, since that is a less severe warning. 385 checkCall_mkstemp(CE, FD); 386 return; 387 } 388 389 const FunctionProtoType *FPT 390 = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens()); 391 if(!FPT) 392 return; 393 394 // Verify that the function takes a single argument. 395 if (FPT->getNumArgs() != 1) 396 return; 397 398 // Verify that the argument is Pointer Type. 399 const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(0)); 400 if (!PT) 401 return; 402 403 // Verify that the argument is a 'char*'. 404 if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) 405 return; 406 407 // Issue a waring. 408 SourceRange R = CE->getCallee()->getSourceRange(); 409 PathDiagnosticLocation CELoc = 410 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 411 BR.EmitBasicReport(AC->getDecl(), 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, &R, 1); 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 SourceRange R = strArg->getSourceRange(); 482 PathDiagnosticLocation CELoc = 483 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 484 SmallString<512> buf; 485 llvm::raw_svector_ostream out(buf); 486 out << "Call to '" << Name << "' should have at least 6 'X's in the" 487 " format string to be secure (" << numX << " 'X'"; 488 if (numX != 1) 489 out << 's'; 490 out << " seen"; 491 if (suffix) { 492 out << ", " << suffix << " character"; 493 if (suffix > 1) 494 out << 's'; 495 out << " used as a suffix"; 496 } 497 out << ')'; 498 BR.EmitBasicReport(AC->getDecl(), 499 "Insecure temporary file creation", "Security", 500 out.str(), CELoc, &R, 1); 501 } 502 503 //===----------------------------------------------------------------------===// 504 // Check: Any use of 'strcpy' is insecure. 505 // 506 // CWE-119: Improper Restriction of Operations within 507 // the Bounds of a Memory Buffer 508 //===----------------------------------------------------------------------===// 509 void WalkAST::checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD) { 510 if (!filter.check_strcpy) 511 return; 512 513 if (!checkCall_strCommon(CE, FD)) 514 return; 515 516 // Issue a warning. 517 SourceRange R = CE->getCallee()->getSourceRange(); 518 PathDiagnosticLocation CELoc = 519 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 520 BR.EmitBasicReport(AC->getDecl(), 521 "Potential insecure memory buffer bounds restriction in " 522 "call 'strcpy'", 523 "Security", 524 "Call to function 'strcpy' is insecure as it does not " 525 "provide bounding of the memory buffer. Replace " 526 "unbounded copy functions with analogous functions that " 527 "support length arguments such as 'strlcpy'. CWE-119.", 528 CELoc, &R, 1); 529 } 530 531 //===----------------------------------------------------------------------===// 532 // Check: Any use of 'strcat' is insecure. 533 // 534 // CWE-119: Improper Restriction of Operations within 535 // the Bounds of a Memory Buffer 536 //===----------------------------------------------------------------------===// 537 void WalkAST::checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD) { 538 if (!filter.check_strcpy) 539 return; 540 541 if (!checkCall_strCommon(CE, FD)) 542 return; 543 544 // Issue a warning. 545 SourceRange R = CE->getCallee()->getSourceRange(); 546 PathDiagnosticLocation CELoc = 547 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 548 BR.EmitBasicReport(AC->getDecl(), 549 "Potential insecure memory buffer bounds restriction in " 550 "call 'strcat'", 551 "Security", 552 "Call to function 'strcat' is insecure as it does not " 553 "provide bounding of the memory buffer. Replace " 554 "unbounded copy functions with analogous functions that " 555 "support length arguments such as 'strlcat'. CWE-119.", 556 CELoc, &R, 1); 557 } 558 559 //===----------------------------------------------------------------------===// 560 // Common check for str* functions with no bounds parameters. 561 //===----------------------------------------------------------------------===// 562 bool WalkAST::checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD) { 563 const FunctionProtoType *FPT 564 = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens()); 565 if (!FPT) 566 return false; 567 568 // Verify the function takes two arguments, three in the _chk version. 569 int numArgs = FPT->getNumArgs(); 570 if (numArgs != 2 && numArgs != 3) 571 return false; 572 573 // Verify the type for both arguments. 574 for (int i = 0; i < 2; i++) { 575 // Verify that the arguments are pointers. 576 const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(i)); 577 if (!PT) 578 return false; 579 580 // Verify that the argument is a 'char*'. 581 if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) 582 return false; 583 } 584 585 return true; 586 } 587 588 //===----------------------------------------------------------------------===// 589 // Check: Linear congruent random number generators should not be used 590 // Originally: <rdar://problem/63371000> 591 // CWE-338: Use of cryptographically weak prng 592 //===----------------------------------------------------------------------===// 593 594 void WalkAST::checkCall_rand(const CallExpr *CE, const FunctionDecl *FD) { 595 if (!filter.check_rand || !CheckRand) 596 return; 597 598 const FunctionProtoType *FTP 599 = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens()); 600 if (!FTP) 601 return; 602 603 if (FTP->getNumArgs() == 1) { 604 // Is the argument an 'unsigned short *'? 605 // (Actually any integer type is allowed.) 606 const PointerType *PT = dyn_cast<PointerType>(FTP->getArgType(0)); 607 if (!PT) 608 return; 609 610 if (! PT->getPointeeType()->isIntegerType()) 611 return; 612 } 613 else if (FTP->getNumArgs() != 0) 614 return; 615 616 // Issue a warning. 617 SmallString<256> buf1; 618 llvm::raw_svector_ostream os1(buf1); 619 os1 << '\'' << *FD << "' is a poor random number generator"; 620 621 SmallString<256> buf2; 622 llvm::raw_svector_ostream os2(buf2); 623 os2 << "Function '" << *FD 624 << "' is obsolete because it implements a poor random number generator." 625 << " Use 'arc4random' instead"; 626 627 SourceRange R = CE->getCallee()->getSourceRange(); 628 PathDiagnosticLocation CELoc = 629 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 630 BR.EmitBasicReport(AC->getDecl(), os1.str(), "Security", os2.str(), 631 CELoc, &R, 1); 632 } 633 634 //===----------------------------------------------------------------------===// 635 // Check: 'random' should not be used 636 // Originally: <rdar://problem/63371000> 637 //===----------------------------------------------------------------------===// 638 639 void WalkAST::checkCall_random(const CallExpr *CE, const FunctionDecl *FD) { 640 if (!CheckRand || !filter.check_rand) 641 return; 642 643 const FunctionProtoType *FTP 644 = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens()); 645 if (!FTP) 646 return; 647 648 // Verify that the function takes no argument. 649 if (FTP->getNumArgs() != 0) 650 return; 651 652 // Issue a warning. 653 SourceRange R = CE->getCallee()->getSourceRange(); 654 PathDiagnosticLocation CELoc = 655 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 656 BR.EmitBasicReport(AC->getDecl(), 657 "'random' is not a secure random number generator", 658 "Security", 659 "The 'random' function produces a sequence of values that " 660 "an adversary may be able to predict. Use 'arc4random' " 661 "instead", CELoc, &R, 1); 662 } 663 664 //===----------------------------------------------------------------------===// 665 // Check: 'vfork' should not be used. 666 // POS33-C: Do not use vfork(). 667 //===----------------------------------------------------------------------===// 668 669 void WalkAST::checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD) { 670 if (!filter.check_vfork) 671 return; 672 673 // All calls to vfork() are insecure, issue a warning. 674 SourceRange R = CE->getCallee()->getSourceRange(); 675 PathDiagnosticLocation CELoc = 676 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 677 BR.EmitBasicReport(AC->getDecl(), 678 "Potential insecure implementation-specific behavior in " 679 "call 'vfork'", 680 "Security", 681 "Call to function 'vfork' is insecure as it can lead to " 682 "denial of service situations in the parent process. " 683 "Replace calls to vfork with calls to the safer " 684 "'posix_spawn' function", 685 CELoc, &R, 1); 686 } 687 688 //===----------------------------------------------------------------------===// 689 // Check: Should check whether privileges are dropped successfully. 690 // Originally: <rdar://problem/6337132> 691 //===----------------------------------------------------------------------===// 692 693 void WalkAST::checkUncheckedReturnValue(CallExpr *CE) { 694 if (!filter.check_UncheckedReturn) 695 return; 696 697 const FunctionDecl *FD = CE->getDirectCallee(); 698 if (!FD) 699 return; 700 701 if (II_setid[0] == NULL) { 702 static const char * const identifiers[num_setids] = { 703 "setuid", "setgid", "seteuid", "setegid", 704 "setreuid", "setregid" 705 }; 706 707 for (size_t i = 0; i < num_setids; i++) 708 II_setid[i] = &BR.getContext().Idents.get(identifiers[i]); 709 } 710 711 const IdentifierInfo *id = FD->getIdentifier(); 712 size_t identifierid; 713 714 for (identifierid = 0; identifierid < num_setids; identifierid++) 715 if (id == II_setid[identifierid]) 716 break; 717 718 if (identifierid >= num_setids) 719 return; 720 721 const FunctionProtoType *FTP 722 = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens()); 723 if (!FTP) 724 return; 725 726 // Verify that the function takes one or two arguments (depending on 727 // the function). 728 if (FTP->getNumArgs() != (identifierid < 4 ? 1 : 2)) 729 return; 730 731 // The arguments must be integers. 732 for (unsigned i = 0; i < FTP->getNumArgs(); i++) 733 if (! FTP->getArgType(i)->isIntegerType()) 734 return; 735 736 // Issue a warning. 737 SmallString<256> buf1; 738 llvm::raw_svector_ostream os1(buf1); 739 os1 << "Return value is not checked in call to '" << *FD << '\''; 740 741 SmallString<256> buf2; 742 llvm::raw_svector_ostream os2(buf2); 743 os2 << "The return value from the call to '" << *FD 744 << "' is not checked. If an error occurs in '" << *FD 745 << "', the following code may execute with unexpected privileges"; 746 747 SourceRange R = CE->getCallee()->getSourceRange(); 748 PathDiagnosticLocation CELoc = 749 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 750 BR.EmitBasicReport(AC->getDecl(), os1.str(), "Security", os2.str(), 751 CELoc, &R, 1); 752 } 753 754 //===----------------------------------------------------------------------===// 755 // SecuritySyntaxChecker 756 //===----------------------------------------------------------------------===// 757 758 namespace { 759 class SecuritySyntaxChecker : public Checker<check::ASTCodeBody> { 760 public: 761 ChecksFilter filter; 762 763 void checkASTCodeBody(const Decl *D, AnalysisManager& mgr, 764 BugReporter &BR) const { 765 WalkAST walker(BR, mgr.getAnalysisDeclContext(D), filter); 766 walker.Visit(D->getBody()); 767 } 768 }; 769 } 770 771 #define REGISTER_CHECKER(name) \ 772 void ento::register##name(CheckerManager &mgr) {\ 773 mgr.registerChecker<SecuritySyntaxChecker>()->filter.check_##name = true;\ 774 } 775 776 REGISTER_CHECKER(gets) 777 REGISTER_CHECKER(getpw) 778 REGISTER_CHECKER(mkstemp) 779 REGISTER_CHECKER(mktemp) 780 REGISTER_CHECKER(strcpy) 781 REGISTER_CHECKER(rand) 782 REGISTER_CHECKER(vfork) 783 REGISTER_CHECKER(FloatLoopCounter) 784 REGISTER_CHECKER(UncheckedReturn) 785 786 787