1218887Sdim//==- CheckSecuritySyntaxOnly.cpp - Basic security checks --------*- C++ -*-==// 2218887Sdim// 3218887Sdim// The LLVM Compiler Infrastructure 4218887Sdim// 5218887Sdim// This file is distributed under the University of Illinois Open Source 6218887Sdim// License. See LICENSE.TXT for details. 7218887Sdim// 8218887Sdim//===----------------------------------------------------------------------===// 9218887Sdim// 10218887Sdim// This file defines a set of flow-insensitive security checks. 11218887Sdim// 12218887Sdim//===----------------------------------------------------------------------===// 13218887Sdim 14218887Sdim#include "ClangSACheckers.h" 15249423Sdim#include "clang/AST/StmtVisitor.h" 16226633Sdim#include "clang/Analysis/AnalysisContext.h" 17226633Sdim#include "clang/Basic/TargetInfo.h" 18249423Sdim#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h" 19221345Sdim#include "clang/StaticAnalyzer/Core/Checker.h" 20226633Sdim#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h" 21234353Sdim#include "llvm/ADT/SmallString.h" 22226633Sdim#include "llvm/ADT/StringSwitch.h" 23218887Sdim#include "llvm/Support/raw_ostream.h" 24218887Sdim 25218887Sdimusing namespace clang; 26218887Sdimusing namespace ento; 27218887Sdim 28218887Sdimstatic bool isArc4RandomAvailable(const ASTContext &Ctx) { 29226633Sdim const llvm::Triple &T = Ctx.getTargetInfo().getTriple(); 30218887Sdim return T.getVendor() == llvm::Triple::Apple || 31218887Sdim T.getOS() == llvm::Triple::FreeBSD || 32218887Sdim T.getOS() == llvm::Triple::NetBSD || 33218887Sdim T.getOS() == llvm::Triple::OpenBSD || 34239462Sdim T.getOS() == llvm::Triple::Bitrig || 35218887Sdim T.getOS() == llvm::Triple::DragonFly; 36218887Sdim} 37218887Sdim 38218887Sdimnamespace { 39234353Sdimstruct ChecksFilter { 40234353Sdim DefaultBool check_gets; 41234353Sdim DefaultBool check_getpw; 42234353Sdim DefaultBool check_mktemp; 43234353Sdim DefaultBool check_mkstemp; 44234353Sdim DefaultBool check_strcpy; 45234353Sdim DefaultBool check_rand; 46234353Sdim DefaultBool check_vfork; 47234353Sdim DefaultBool check_FloatLoopCounter; 48234353Sdim DefaultBool check_UncheckedReturn; 49234353Sdim}; 50234353Sdim 51218887Sdimclass WalkAST : public StmtVisitor<WalkAST> { 52218887Sdim BugReporter &BR; 53234353Sdim AnalysisDeclContext* AC; 54218887Sdim enum { num_setids = 6 }; 55218887Sdim IdentifierInfo *II_setid[num_setids]; 56218887Sdim 57218887Sdim const bool CheckRand; 58234353Sdim const ChecksFilter &filter; 59218887Sdim 60218887Sdimpublic: 61234353Sdim WalkAST(BugReporter &br, AnalysisDeclContext* ac, 62234353Sdim const ChecksFilter &f) 63226633Sdim : BR(br), AC(ac), II_setid(), 64234353Sdim CheckRand(isArc4RandomAvailable(BR.getContext())), 65234353Sdim filter(f) {} 66218887Sdim 67218887Sdim // Statement visitor methods. 68218887Sdim void VisitCallExpr(CallExpr *CE); 69218887Sdim void VisitForStmt(ForStmt *S); 70218887Sdim void VisitCompoundStmt (CompoundStmt *S); 71218887Sdim void VisitStmt(Stmt *S) { VisitChildren(S); } 72218887Sdim 73218887Sdim void VisitChildren(Stmt *S); 74218887Sdim 75218887Sdim // Helpers. 76221345Sdim bool checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD); 77218887Sdim 78221345Sdim typedef void (WalkAST::*FnCheck)(const CallExpr *, 79221345Sdim const FunctionDecl *); 80221345Sdim 81218887Sdim // Checker-specific methods. 82221345Sdim void checkLoopConditionForFloat(const ForStmt *FS); 83221345Sdim void checkCall_gets(const CallExpr *CE, const FunctionDecl *FD); 84221345Sdim void checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD); 85221345Sdim void checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD); 86234353Sdim void checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD); 87221345Sdim void checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD); 88221345Sdim void checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD); 89221345Sdim void checkCall_rand(const CallExpr *CE, const FunctionDecl *FD); 90221345Sdim void checkCall_random(const CallExpr *CE, const FunctionDecl *FD); 91226633Sdim void checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD); 92221345Sdim void checkUncheckedReturnValue(CallExpr *CE); 93218887Sdim}; 94218887Sdim} // end anonymous namespace 95218887Sdim 96218887Sdim//===----------------------------------------------------------------------===// 97218887Sdim// AST walking. 98218887Sdim//===----------------------------------------------------------------------===// 99218887Sdim 100218887Sdimvoid WalkAST::VisitChildren(Stmt *S) { 101218887Sdim for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I) 102218887Sdim if (Stmt *child = *I) 103218887Sdim Visit(child); 104218887Sdim} 105218887Sdim 106218887Sdimvoid WalkAST::VisitCallExpr(CallExpr *CE) { 107221345Sdim // Get the callee. 108221345Sdim const FunctionDecl *FD = CE->getDirectCallee(); 109218887Sdim 110221345Sdim if (!FD) 111221345Sdim return; 112221345Sdim 113221345Sdim // Get the name of the callee. If it's a builtin, strip off the prefix. 114221345Sdim IdentifierInfo *II = FD->getIdentifier(); 115221345Sdim if (!II) // if no identifier, not a simple C function 116221345Sdim return; 117226633Sdim StringRef Name = II->getName(); 118221345Sdim if (Name.startswith("__builtin_")) 119221345Sdim Name = Name.substr(10); 120221345Sdim 121221345Sdim // Set the evaluation function by switching on the callee name. 122221345Sdim FnCheck evalFunction = llvm::StringSwitch<FnCheck>(Name) 123221345Sdim .Case("gets", &WalkAST::checkCall_gets) 124221345Sdim .Case("getpw", &WalkAST::checkCall_getpw) 125221345Sdim .Case("mktemp", &WalkAST::checkCall_mktemp) 126234353Sdim .Case("mkstemp", &WalkAST::checkCall_mkstemp) 127234353Sdim .Case("mkdtemp", &WalkAST::checkCall_mkstemp) 128234353Sdim .Case("mkstemps", &WalkAST::checkCall_mkstemp) 129221345Sdim .Cases("strcpy", "__strcpy_chk", &WalkAST::checkCall_strcpy) 130221345Sdim .Cases("strcat", "__strcat_chk", &WalkAST::checkCall_strcat) 131221345Sdim .Case("drand48", &WalkAST::checkCall_rand) 132221345Sdim .Case("erand48", &WalkAST::checkCall_rand) 133221345Sdim .Case("jrand48", &WalkAST::checkCall_rand) 134221345Sdim .Case("lrand48", &WalkAST::checkCall_rand) 135221345Sdim .Case("mrand48", &WalkAST::checkCall_rand) 136221345Sdim .Case("nrand48", &WalkAST::checkCall_rand) 137221345Sdim .Case("lcong48", &WalkAST::checkCall_rand) 138221345Sdim .Case("rand", &WalkAST::checkCall_rand) 139221345Sdim .Case("rand_r", &WalkAST::checkCall_rand) 140221345Sdim .Case("random", &WalkAST::checkCall_random) 141226633Sdim .Case("vfork", &WalkAST::checkCall_vfork) 142221345Sdim .Default(NULL); 143221345Sdim 144221345Sdim // If the callee isn't defined, it is not of security concern. 145221345Sdim // Check and evaluate the call. 146221345Sdim if (evalFunction) 147221345Sdim (this->*evalFunction)(CE, FD); 148221345Sdim 149218887Sdim // Recurse and check children. 150218887Sdim VisitChildren(CE); 151218887Sdim} 152218887Sdim 153218887Sdimvoid WalkAST::VisitCompoundStmt(CompoundStmt *S) { 154218887Sdim for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I) 155218887Sdim if (Stmt *child = *I) { 156218887Sdim if (CallExpr *CE = dyn_cast<CallExpr>(child)) 157221345Sdim checkUncheckedReturnValue(CE); 158218887Sdim Visit(child); 159218887Sdim } 160218887Sdim} 161218887Sdim 162218887Sdimvoid WalkAST::VisitForStmt(ForStmt *FS) { 163221345Sdim checkLoopConditionForFloat(FS); 164218887Sdim 165218887Sdim // Recurse and check children. 166218887Sdim VisitChildren(FS); 167218887Sdim} 168218887Sdim 169218887Sdim//===----------------------------------------------------------------------===// 170218887Sdim// Check: floating poing variable used as loop counter. 171218887Sdim// Originally: <rdar://problem/6336718> 172218887Sdim// Implements: CERT security coding advisory FLP-30. 173218887Sdim//===----------------------------------------------------------------------===// 174218887Sdim 175218887Sdimstatic const DeclRefExpr* 176221345SdimgetIncrementedVar(const Expr *expr, const VarDecl *x, const VarDecl *y) { 177218887Sdim expr = expr->IgnoreParenCasts(); 178218887Sdim 179218887Sdim if (const BinaryOperator *B = dyn_cast<BinaryOperator>(expr)) { 180218887Sdim if (!(B->isAssignmentOp() || B->isCompoundAssignmentOp() || 181218887Sdim B->getOpcode() == BO_Comma)) 182218887Sdim return NULL; 183218887Sdim 184221345Sdim if (const DeclRefExpr *lhs = getIncrementedVar(B->getLHS(), x, y)) 185218887Sdim return lhs; 186218887Sdim 187221345Sdim if (const DeclRefExpr *rhs = getIncrementedVar(B->getRHS(), x, y)) 188218887Sdim return rhs; 189218887Sdim 190218887Sdim return NULL; 191218887Sdim } 192218887Sdim 193218887Sdim if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(expr)) { 194218887Sdim const NamedDecl *ND = DR->getDecl(); 195218887Sdim return ND == x || ND == y ? DR : NULL; 196218887Sdim } 197218887Sdim 198218887Sdim if (const UnaryOperator *U = dyn_cast<UnaryOperator>(expr)) 199218887Sdim return U->isIncrementDecrementOp() 200221345Sdim ? getIncrementedVar(U->getSubExpr(), x, y) : NULL; 201218887Sdim 202218887Sdim return NULL; 203218887Sdim} 204218887Sdim 205218887Sdim/// CheckLoopConditionForFloat - This check looks for 'for' statements that 206218887Sdim/// use a floating point variable as a loop counter. 207218887Sdim/// CERT: FLP30-C, FLP30-CPP. 208218887Sdim/// 209221345Sdimvoid WalkAST::checkLoopConditionForFloat(const ForStmt *FS) { 210234353Sdim if (!filter.check_FloatLoopCounter) 211234353Sdim return; 212234353Sdim 213218887Sdim // Does the loop have a condition? 214218887Sdim const Expr *condition = FS->getCond(); 215218887Sdim 216218887Sdim if (!condition) 217218887Sdim return; 218218887Sdim 219218887Sdim // Does the loop have an increment? 220218887Sdim const Expr *increment = FS->getInc(); 221218887Sdim 222218887Sdim if (!increment) 223218887Sdim return; 224218887Sdim 225218887Sdim // Strip away '()' and casts. 226218887Sdim condition = condition->IgnoreParenCasts(); 227218887Sdim increment = increment->IgnoreParenCasts(); 228218887Sdim 229218887Sdim // Is the loop condition a comparison? 230218887Sdim const BinaryOperator *B = dyn_cast<BinaryOperator>(condition); 231218887Sdim 232218887Sdim if (!B) 233218887Sdim return; 234218887Sdim 235218887Sdim // Is this a comparison? 236218887Sdim if (!(B->isRelationalOp() || B->isEqualityOp())) 237218887Sdim return; 238218887Sdim 239218887Sdim // Are we comparing variables? 240218887Sdim const DeclRefExpr *drLHS = 241218887Sdim dyn_cast<DeclRefExpr>(B->getLHS()->IgnoreParenLValueCasts()); 242218887Sdim const DeclRefExpr *drRHS = 243218887Sdim dyn_cast<DeclRefExpr>(B->getRHS()->IgnoreParenLValueCasts()); 244218887Sdim 245218887Sdim // Does at least one of the variables have a floating point type? 246218887Sdim drLHS = drLHS && drLHS->getType()->isRealFloatingType() ? drLHS : NULL; 247218887Sdim drRHS = drRHS && drRHS->getType()->isRealFloatingType() ? drRHS : NULL; 248218887Sdim 249218887Sdim if (!drLHS && !drRHS) 250218887Sdim return; 251218887Sdim 252218887Sdim const VarDecl *vdLHS = drLHS ? dyn_cast<VarDecl>(drLHS->getDecl()) : NULL; 253218887Sdim const VarDecl *vdRHS = drRHS ? dyn_cast<VarDecl>(drRHS->getDecl()) : NULL; 254218887Sdim 255218887Sdim if (!vdLHS && !vdRHS) 256218887Sdim return; 257218887Sdim 258218887Sdim // Does either variable appear in increment? 259221345Sdim const DeclRefExpr *drInc = getIncrementedVar(increment, vdLHS, vdRHS); 260218887Sdim 261218887Sdim if (!drInc) 262218887Sdim return; 263218887Sdim 264218887Sdim // Emit the error. First figure out which DeclRefExpr in the condition 265218887Sdim // referenced the compared variable. 266243830Sdim assert(drInc->getDecl()); 267218887Sdim const DeclRefExpr *drCond = vdLHS == drInc->getDecl() ? drLHS : drRHS; 268218887Sdim 269226633Sdim SmallVector<SourceRange, 2> ranges; 270234353Sdim SmallString<256> sbuf; 271218887Sdim llvm::raw_svector_ostream os(sbuf); 272218887Sdim 273218887Sdim os << "Variable '" << drCond->getDecl()->getName() 274218887Sdim << "' with floating point type '" << drCond->getType().getAsString() 275218887Sdim << "' should not be used as a loop counter"; 276218887Sdim 277218887Sdim ranges.push_back(drCond->getSourceRange()); 278218887Sdim ranges.push_back(drInc->getSourceRange()); 279218887Sdim 280218887Sdim const char *bugType = "Floating point variable used as loop counter"; 281226633Sdim 282226633Sdim PathDiagnosticLocation FSLoc = 283226633Sdim PathDiagnosticLocation::createBegin(FS, BR.getSourceManager(), AC); 284234353Sdim BR.EmitBasicReport(AC->getDecl(), 285234353Sdim bugType, "Security", os.str(), 286263508Sdim FSLoc, ranges); 287218887Sdim} 288218887Sdim 289218887Sdim//===----------------------------------------------------------------------===// 290218887Sdim// Check: Any use of 'gets' is insecure. 291218887Sdim// Originally: <rdar://problem/6335715> 292218887Sdim// Implements (part of): 300-BSI (buildsecurityin.us-cert.gov) 293218887Sdim// CWE-242: Use of Inherently Dangerous Function 294218887Sdim//===----------------------------------------------------------------------===// 295218887Sdim 296221345Sdimvoid WalkAST::checkCall_gets(const CallExpr *CE, const FunctionDecl *FD) { 297234353Sdim if (!filter.check_gets) 298234353Sdim return; 299234353Sdim 300263508Sdim const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); 301218887Sdim if (!FPT) 302218887Sdim return; 303218887Sdim 304218887Sdim // Verify that the function takes a single argument. 305218887Sdim if (FPT->getNumArgs() != 1) 306218887Sdim return; 307218887Sdim 308218887Sdim // Is the argument a 'char*'? 309263508Sdim const PointerType *PT = FPT->getArgType(0)->getAs<PointerType>(); 310218887Sdim if (!PT) 311218887Sdim return; 312218887Sdim 313218887Sdim if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) 314218887Sdim return; 315218887Sdim 316218887Sdim // Issue a warning. 317226633Sdim PathDiagnosticLocation CELoc = 318226633Sdim PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 319234353Sdim BR.EmitBasicReport(AC->getDecl(), 320234353Sdim "Potential buffer overflow in call to 'gets'", 321218887Sdim "Security", 322218887Sdim "Call to function 'gets' is extremely insecure as it can " 323218887Sdim "always result in a buffer overflow", 324263508Sdim CELoc, CE->getCallee()->getSourceRange()); 325218887Sdim} 326218887Sdim 327218887Sdim//===----------------------------------------------------------------------===// 328218887Sdim// Check: Any use of 'getpwd' is insecure. 329218887Sdim// CWE-477: Use of Obsolete Functions 330218887Sdim//===----------------------------------------------------------------------===// 331218887Sdim 332221345Sdimvoid WalkAST::checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD) { 333234353Sdim if (!filter.check_getpw) 334234353Sdim return; 335234353Sdim 336263508Sdim const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); 337218887Sdim if (!FPT) 338218887Sdim return; 339218887Sdim 340218887Sdim // Verify that the function takes two arguments. 341218887Sdim if (FPT->getNumArgs() != 2) 342218887Sdim return; 343218887Sdim 344218887Sdim // Verify the first argument type is integer. 345251662Sdim if (!FPT->getArgType(0)->isIntegralOrUnscopedEnumerationType()) 346218887Sdim return; 347218887Sdim 348218887Sdim // Verify the second argument type is char*. 349263508Sdim const PointerType *PT = FPT->getArgType(1)->getAs<PointerType>(); 350218887Sdim if (!PT) 351218887Sdim return; 352218887Sdim 353218887Sdim if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) 354218887Sdim return; 355218887Sdim 356218887Sdim // Issue a warning. 357226633Sdim PathDiagnosticLocation CELoc = 358226633Sdim PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 359234353Sdim BR.EmitBasicReport(AC->getDecl(), 360234353Sdim "Potential buffer overflow in call to 'getpw'", 361218887Sdim "Security", 362218887Sdim "The getpw() function is dangerous as it may overflow the " 363218887Sdim "provided buffer. It is obsoleted by getpwuid().", 364263508Sdim CELoc, CE->getCallee()->getSourceRange()); 365218887Sdim} 366218887Sdim 367218887Sdim//===----------------------------------------------------------------------===// 368234353Sdim// Check: Any use of 'mktemp' is insecure. It is obsoleted by mkstemp(). 369218887Sdim// CWE-377: Insecure Temporary File 370218887Sdim//===----------------------------------------------------------------------===// 371218887Sdim 372221345Sdimvoid WalkAST::checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD) { 373234353Sdim if (!filter.check_mktemp) { 374234353Sdim // Fall back to the security check of looking for enough 'X's in the 375234353Sdim // format string, since that is a less severe warning. 376234353Sdim checkCall_mkstemp(CE, FD); 377234353Sdim return; 378234353Sdim } 379234353Sdim 380263508Sdim const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); 381218887Sdim if(!FPT) 382218887Sdim return; 383218887Sdim 384221345Sdim // Verify that the function takes a single argument. 385218887Sdim if (FPT->getNumArgs() != 1) 386218887Sdim return; 387218887Sdim 388218887Sdim // Verify that the argument is Pointer Type. 389263508Sdim const PointerType *PT = FPT->getArgType(0)->getAs<PointerType>(); 390218887Sdim if (!PT) 391218887Sdim return; 392218887Sdim 393218887Sdim // Verify that the argument is a 'char*'. 394218887Sdim if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) 395218887Sdim return; 396218887Sdim 397218887Sdim // Issue a waring. 398226633Sdim PathDiagnosticLocation CELoc = 399226633Sdim PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 400234353Sdim BR.EmitBasicReport(AC->getDecl(), 401234353Sdim "Potential insecure temporary file in call 'mktemp'", 402218887Sdim "Security", 403218887Sdim "Call to function 'mktemp' is insecure as it always " 404234353Sdim "creates or uses insecure temporary file. Use 'mkstemp' " 405234353Sdim "instead", 406263508Sdim CELoc, CE->getCallee()->getSourceRange()); 407218887Sdim} 408218887Sdim 409234353Sdim 410218887Sdim//===----------------------------------------------------------------------===// 411234353Sdim// Check: Use of 'mkstemp', 'mktemp', 'mkdtemp' should contain at least 6 X's. 412234353Sdim//===----------------------------------------------------------------------===// 413234353Sdim 414234353Sdimvoid WalkAST::checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD) { 415234353Sdim if (!filter.check_mkstemp) 416234353Sdim return; 417234353Sdim 418234353Sdim StringRef Name = FD->getIdentifier()->getName(); 419234353Sdim std::pair<signed, signed> ArgSuffix = 420234353Sdim llvm::StringSwitch<std::pair<signed, signed> >(Name) 421234353Sdim .Case("mktemp", std::make_pair(0,-1)) 422234353Sdim .Case("mkstemp", std::make_pair(0,-1)) 423234353Sdim .Case("mkdtemp", std::make_pair(0,-1)) 424234353Sdim .Case("mkstemps", std::make_pair(0,1)) 425234353Sdim .Default(std::make_pair(-1, -1)); 426234353Sdim 427234353Sdim assert(ArgSuffix.first >= 0 && "Unsupported function"); 428234353Sdim 429234353Sdim // Check if the number of arguments is consistent with out expectations. 430234353Sdim unsigned numArgs = CE->getNumArgs(); 431234353Sdim if ((signed) numArgs <= ArgSuffix.first) 432234353Sdim return; 433234353Sdim 434234353Sdim const StringLiteral *strArg = 435234353Sdim dyn_cast<StringLiteral>(CE->getArg((unsigned)ArgSuffix.first) 436234353Sdim ->IgnoreParenImpCasts()); 437234353Sdim 438234353Sdim // Currently we only handle string literals. It is possible to do better, 439234353Sdim // either by looking at references to const variables, or by doing real 440234353Sdim // flow analysis. 441234353Sdim if (!strArg || strArg->getCharByteWidth() != 1) 442234353Sdim return; 443234353Sdim 444234353Sdim // Count the number of X's, taking into account a possible cutoff suffix. 445234353Sdim StringRef str = strArg->getString(); 446234353Sdim unsigned numX = 0; 447234353Sdim unsigned n = str.size(); 448234353Sdim 449234353Sdim // Take into account the suffix. 450234353Sdim unsigned suffix = 0; 451234353Sdim if (ArgSuffix.second >= 0) { 452234353Sdim const Expr *suffixEx = CE->getArg((unsigned)ArgSuffix.second); 453234353Sdim llvm::APSInt Result; 454234353Sdim if (!suffixEx->EvaluateAsInt(Result, BR.getContext())) 455234353Sdim return; 456234353Sdim // FIXME: Issue a warning. 457234353Sdim if (Result.isNegative()) 458234353Sdim return; 459234353Sdim suffix = (unsigned) Result.getZExtValue(); 460234353Sdim n = (n > suffix) ? n - suffix : 0; 461234353Sdim } 462234353Sdim 463234353Sdim for (unsigned i = 0; i < n; ++i) 464234353Sdim if (str[i] == 'X') ++numX; 465234353Sdim 466234353Sdim if (numX >= 6) 467234353Sdim return; 468234353Sdim 469234353Sdim // Issue a warning. 470234353Sdim PathDiagnosticLocation CELoc = 471234353Sdim PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 472234353Sdim SmallString<512> buf; 473234353Sdim llvm::raw_svector_ostream out(buf); 474234353Sdim out << "Call to '" << Name << "' should have at least 6 'X's in the" 475234353Sdim " format string to be secure (" << numX << " 'X'"; 476234353Sdim if (numX != 1) 477234353Sdim out << 's'; 478234353Sdim out << " seen"; 479234353Sdim if (suffix) { 480234353Sdim out << ", " << suffix << " character"; 481234353Sdim if (suffix > 1) 482234353Sdim out << 's'; 483234353Sdim out << " used as a suffix"; 484234353Sdim } 485234353Sdim out << ')'; 486234353Sdim BR.EmitBasicReport(AC->getDecl(), 487234353Sdim "Insecure temporary file creation", "Security", 488263508Sdim out.str(), CELoc, strArg->getSourceRange()); 489234353Sdim} 490234353Sdim 491234353Sdim//===----------------------------------------------------------------------===// 492221345Sdim// Check: Any use of 'strcpy' is insecure. 493221345Sdim// 494221345Sdim// CWE-119: Improper Restriction of Operations within 495221345Sdim// the Bounds of a Memory Buffer 496218887Sdim//===----------------------------------------------------------------------===// 497221345Sdimvoid WalkAST::checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD) { 498234353Sdim if (!filter.check_strcpy) 499234353Sdim return; 500234353Sdim 501221345Sdim if (!checkCall_strCommon(CE, FD)) 502221345Sdim return; 503218887Sdim 504221345Sdim // Issue a warning. 505226633Sdim PathDiagnosticLocation CELoc = 506226633Sdim PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 507234353Sdim BR.EmitBasicReport(AC->getDecl(), 508234353Sdim "Potential insecure memory buffer bounds restriction in " 509221345Sdim "call 'strcpy'", 510221345Sdim "Security", 511221345Sdim "Call to function 'strcpy' is insecure as it does not " 512234353Sdim "provide bounding of the memory buffer. Replace " 513234353Sdim "unbounded copy functions with analogous functions that " 514234353Sdim "support length arguments such as 'strlcpy'. CWE-119.", 515263508Sdim CELoc, CE->getCallee()->getSourceRange()); 516221345Sdim} 517218887Sdim 518221345Sdim//===----------------------------------------------------------------------===// 519221345Sdim// Check: Any use of 'strcat' is insecure. 520221345Sdim// 521221345Sdim// CWE-119: Improper Restriction of Operations within 522221345Sdim// the Bounds of a Memory Buffer 523221345Sdim//===----------------------------------------------------------------------===// 524221345Sdimvoid WalkAST::checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD) { 525234353Sdim if (!filter.check_strcpy) 526234353Sdim return; 527234353Sdim 528221345Sdim if (!checkCall_strCommon(CE, FD)) 529221345Sdim return; 530221345Sdim 531221345Sdim // Issue a warning. 532226633Sdim PathDiagnosticLocation CELoc = 533226633Sdim PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 534234353Sdim BR.EmitBasicReport(AC->getDecl(), 535234353Sdim "Potential insecure memory buffer bounds restriction in " 536234353Sdim "call 'strcat'", 537234353Sdim "Security", 538234353Sdim "Call to function 'strcat' is insecure as it does not " 539234353Sdim "provide bounding of the memory buffer. Replace " 540234353Sdim "unbounded copy functions with analogous functions that " 541234353Sdim "support length arguments such as 'strlcat'. CWE-119.", 542263508Sdim CELoc, CE->getCallee()->getSourceRange()); 543221345Sdim} 544221345Sdim 545221345Sdim//===----------------------------------------------------------------------===// 546221345Sdim// Common check for str* functions with no bounds parameters. 547221345Sdim//===----------------------------------------------------------------------===// 548221345Sdimbool WalkAST::checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD) { 549263508Sdim const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); 550221345Sdim if (!FPT) 551221345Sdim return false; 552221345Sdim 553221345Sdim // Verify the function takes two arguments, three in the _chk version. 554221345Sdim int numArgs = FPT->getNumArgs(); 555221345Sdim if (numArgs != 2 && numArgs != 3) 556221345Sdim return false; 557221345Sdim 558221345Sdim // Verify the type for both arguments. 559221345Sdim for (int i = 0; i < 2; i++) { 560221345Sdim // Verify that the arguments are pointers. 561263508Sdim const PointerType *PT = FPT->getArgType(i)->getAs<PointerType>(); 562221345Sdim if (!PT) 563221345Sdim return false; 564221345Sdim 565221345Sdim // Verify that the argument is a 'char*'. 566221345Sdim if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) 567221345Sdim return false; 568218887Sdim } 569218887Sdim 570221345Sdim return true; 571221345Sdim} 572218887Sdim 573221345Sdim//===----------------------------------------------------------------------===// 574221345Sdim// Check: Linear congruent random number generators should not be used 575221345Sdim// Originally: <rdar://problem/63371000> 576221345Sdim// CWE-338: Use of cryptographically weak prng 577221345Sdim//===----------------------------------------------------------------------===// 578218887Sdim 579221345Sdimvoid WalkAST::checkCall_rand(const CallExpr *CE, const FunctionDecl *FD) { 580234353Sdim if (!filter.check_rand || !CheckRand) 581218887Sdim return; 582218887Sdim 583263508Sdim const FunctionProtoType *FTP = FD->getType()->getAs<FunctionProtoType>(); 584218887Sdim if (!FTP) 585218887Sdim return; 586218887Sdim 587218887Sdim if (FTP->getNumArgs() == 1) { 588218887Sdim // Is the argument an 'unsigned short *'? 589218887Sdim // (Actually any integer type is allowed.) 590263508Sdim const PointerType *PT = FTP->getArgType(0)->getAs<PointerType>(); 591218887Sdim if (!PT) 592218887Sdim return; 593218887Sdim 594251662Sdim if (! PT->getPointeeType()->isIntegralOrUnscopedEnumerationType()) 595218887Sdim return; 596218887Sdim } 597218887Sdim else if (FTP->getNumArgs() != 0) 598218887Sdim return; 599218887Sdim 600218887Sdim // Issue a warning. 601234353Sdim SmallString<256> buf1; 602218887Sdim llvm::raw_svector_ostream os1(buf1); 603226633Sdim os1 << '\'' << *FD << "' is a poor random number generator"; 604218887Sdim 605234353Sdim SmallString<256> buf2; 606218887Sdim llvm::raw_svector_ostream os2(buf2); 607226633Sdim os2 << "Function '" << *FD 608218887Sdim << "' is obsolete because it implements a poor random number generator." 609218887Sdim << " Use 'arc4random' instead"; 610218887Sdim 611226633Sdim PathDiagnosticLocation CELoc = 612226633Sdim PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 613234353Sdim BR.EmitBasicReport(AC->getDecl(), os1.str(), "Security", os2.str(), 614263508Sdim CELoc, CE->getCallee()->getSourceRange()); 615218887Sdim} 616218887Sdim 617218887Sdim//===----------------------------------------------------------------------===// 618218887Sdim// Check: 'random' should not be used 619218887Sdim// Originally: <rdar://problem/63371000> 620218887Sdim//===----------------------------------------------------------------------===// 621218887Sdim 622221345Sdimvoid WalkAST::checkCall_random(const CallExpr *CE, const FunctionDecl *FD) { 623234353Sdim if (!CheckRand || !filter.check_rand) 624218887Sdim return; 625218887Sdim 626263508Sdim const FunctionProtoType *FTP = FD->getType()->getAs<FunctionProtoType>(); 627218887Sdim if (!FTP) 628218887Sdim return; 629218887Sdim 630218887Sdim // Verify that the function takes no argument. 631218887Sdim if (FTP->getNumArgs() != 0) 632218887Sdim return; 633218887Sdim 634218887Sdim // Issue a warning. 635226633Sdim PathDiagnosticLocation CELoc = 636226633Sdim PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 637234353Sdim BR.EmitBasicReport(AC->getDecl(), 638234353Sdim "'random' is not a secure random number generator", 639218887Sdim "Security", 640218887Sdim "The 'random' function produces a sequence of values that " 641218887Sdim "an adversary may be able to predict. Use 'arc4random' " 642263508Sdim "instead", CELoc, CE->getCallee()->getSourceRange()); 643218887Sdim} 644218887Sdim 645218887Sdim//===----------------------------------------------------------------------===// 646226633Sdim// Check: 'vfork' should not be used. 647226633Sdim// POS33-C: Do not use vfork(). 648226633Sdim//===----------------------------------------------------------------------===// 649226633Sdim 650226633Sdimvoid WalkAST::checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD) { 651234353Sdim if (!filter.check_vfork) 652234353Sdim return; 653234353Sdim 654226633Sdim // All calls to vfork() are insecure, issue a warning. 655226633Sdim PathDiagnosticLocation CELoc = 656226633Sdim PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 657234353Sdim BR.EmitBasicReport(AC->getDecl(), 658234353Sdim "Potential insecure implementation-specific behavior in " 659226633Sdim "call 'vfork'", 660226633Sdim "Security", 661226633Sdim "Call to function 'vfork' is insecure as it can lead to " 662226633Sdim "denial of service situations in the parent process. " 663226633Sdim "Replace calls to vfork with calls to the safer " 664226633Sdim "'posix_spawn' function", 665263508Sdim CELoc, CE->getCallee()->getSourceRange()); 666226633Sdim} 667226633Sdim 668226633Sdim//===----------------------------------------------------------------------===// 669218887Sdim// Check: Should check whether privileges are dropped successfully. 670218887Sdim// Originally: <rdar://problem/6337132> 671218887Sdim//===----------------------------------------------------------------------===// 672218887Sdim 673221345Sdimvoid WalkAST::checkUncheckedReturnValue(CallExpr *CE) { 674234353Sdim if (!filter.check_UncheckedReturn) 675234353Sdim return; 676234353Sdim 677218887Sdim const FunctionDecl *FD = CE->getDirectCallee(); 678218887Sdim if (!FD) 679218887Sdim return; 680218887Sdim 681218887Sdim if (II_setid[0] == NULL) { 682218887Sdim static const char * const identifiers[num_setids] = { 683218887Sdim "setuid", "setgid", "seteuid", "setegid", 684218887Sdim "setreuid", "setregid" 685218887Sdim }; 686218887Sdim 687218887Sdim for (size_t i = 0; i < num_setids; i++) 688218887Sdim II_setid[i] = &BR.getContext().Idents.get(identifiers[i]); 689218887Sdim } 690218887Sdim 691218887Sdim const IdentifierInfo *id = FD->getIdentifier(); 692218887Sdim size_t identifierid; 693218887Sdim 694218887Sdim for (identifierid = 0; identifierid < num_setids; identifierid++) 695218887Sdim if (id == II_setid[identifierid]) 696218887Sdim break; 697218887Sdim 698218887Sdim if (identifierid >= num_setids) 699218887Sdim return; 700218887Sdim 701263508Sdim const FunctionProtoType *FTP = FD->getType()->getAs<FunctionProtoType>(); 702218887Sdim if (!FTP) 703218887Sdim return; 704218887Sdim 705218887Sdim // Verify that the function takes one or two arguments (depending on 706218887Sdim // the function). 707218887Sdim if (FTP->getNumArgs() != (identifierid < 4 ? 1 : 2)) 708218887Sdim return; 709218887Sdim 710218887Sdim // The arguments must be integers. 711218887Sdim for (unsigned i = 0; i < FTP->getNumArgs(); i++) 712251662Sdim if (! FTP->getArgType(i)->isIntegralOrUnscopedEnumerationType()) 713218887Sdim return; 714218887Sdim 715218887Sdim // Issue a warning. 716234353Sdim SmallString<256> buf1; 717218887Sdim llvm::raw_svector_ostream os1(buf1); 718226633Sdim os1 << "Return value is not checked in call to '" << *FD << '\''; 719218887Sdim 720234353Sdim SmallString<256> buf2; 721218887Sdim llvm::raw_svector_ostream os2(buf2); 722226633Sdim os2 << "The return value from the call to '" << *FD 723226633Sdim << "' is not checked. If an error occurs in '" << *FD 724218887Sdim << "', the following code may execute with unexpected privileges"; 725218887Sdim 726226633Sdim PathDiagnosticLocation CELoc = 727226633Sdim PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); 728234353Sdim BR.EmitBasicReport(AC->getDecl(), os1.str(), "Security", os2.str(), 729263508Sdim CELoc, CE->getCallee()->getSourceRange()); 730218887Sdim} 731218887Sdim 732218887Sdim//===----------------------------------------------------------------------===// 733218887Sdim// SecuritySyntaxChecker 734218887Sdim//===----------------------------------------------------------------------===// 735218887Sdim 736218887Sdimnamespace { 737221345Sdimclass SecuritySyntaxChecker : public Checker<check::ASTCodeBody> { 738218887Sdimpublic: 739234353Sdim ChecksFilter filter; 740234353Sdim 741218887Sdim void checkASTCodeBody(const Decl *D, AnalysisManager& mgr, 742218887Sdim BugReporter &BR) const { 743234353Sdim WalkAST walker(BR, mgr.getAnalysisDeclContext(D), filter); 744218887Sdim walker.Visit(D->getBody()); 745218887Sdim } 746218887Sdim}; 747218887Sdim} 748218887Sdim 749234353Sdim#define REGISTER_CHECKER(name) \ 750234353Sdimvoid ento::register##name(CheckerManager &mgr) {\ 751234353Sdim mgr.registerChecker<SecuritySyntaxChecker>()->filter.check_##name = true;\ 752218887Sdim} 753234353Sdim 754234353SdimREGISTER_CHECKER(gets) 755234353SdimREGISTER_CHECKER(getpw) 756234353SdimREGISTER_CHECKER(mkstemp) 757234353SdimREGISTER_CHECKER(mktemp) 758234353SdimREGISTER_CHECKER(strcpy) 759234353SdimREGISTER_CHECKER(rand) 760234353SdimREGISTER_CHECKER(vfork) 761234353SdimREGISTER_CHECKER(FloatLoopCounter) 762234353SdimREGISTER_CHECKER(UncheckedReturn) 763234353Sdim 764234353Sdim 765