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