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