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Diffstat (limited to 'clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp')
| -rw-r--r-- | clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp | 740 |
1 files changed, 740 insertions, 0 deletions
diff --git a/clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp new file mode 100644 index 0000000..135b81d --- /dev/null +++ b/clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp @@ -0,0 +1,740 @@ +//== GenericTaintChecker.cpp ----------------------------------- -*- C++ -*--=// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This checker defines the attack surface for generic taint propagation. +// +// The taint information produced by it might be useful to other checkers. For +// example, checkers should report errors which involve tainted data more +// aggressively, even if the involved symbols are under constrained. +// +//===----------------------------------------------------------------------===// +#include "ClangSACheckers.h" +#include "clang/StaticAnalyzer/Core/Checker.h" +#include "clang/StaticAnalyzer/Core/CheckerManager.h" +#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" +#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h" +#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" +#include "clang/Basic/Builtins.h" +#include <climits> + +using namespace clang; +using namespace ento; + +namespace { +class GenericTaintChecker : public Checker< check::PostStmt<CallExpr>, + check::PreStmt<CallExpr> > { +public: + static void *getTag() { static int Tag; return &Tag; } + + void checkPostStmt(const CallExpr *CE, CheckerContext &C) const; + void checkPostStmt(const DeclRefExpr *DRE, CheckerContext &C) const; + + void checkPreStmt(const CallExpr *CE, CheckerContext &C) const; + +private: + static const unsigned InvalidArgIndex = UINT_MAX; + /// Denotes the return vale. + static const unsigned ReturnValueIndex = UINT_MAX - 1; + + mutable OwningPtr<BugType> BT; + inline void initBugType() const { + if (!BT) + BT.reset(new BugType("Use of Untrusted Data", "Untrusted Data")); + } + + /// \brief Catch taint related bugs. Check if tainted data is passed to a + /// system call etc. + bool checkPre(const CallExpr *CE, CheckerContext &C) const; + + /// \brief Add taint sources on a pre-visit. + void addSourcesPre(const CallExpr *CE, CheckerContext &C) const; + + /// \brief Propagate taint generated at pre-visit. + bool propagateFromPre(const CallExpr *CE, CheckerContext &C) const; + + /// \brief Add taint sources on a post visit. + void addSourcesPost(const CallExpr *CE, CheckerContext &C) const; + + /// Check if the region the expression evaluates to is the standard input, + /// and thus, is tainted. + static bool isStdin(const Expr *E, CheckerContext &C); + + /// \brief Given a pointer argument, get the symbol of the value it contains + /// (points to). + static SymbolRef getPointedToSymbol(CheckerContext &C, const Expr *Arg); + + /// Functions defining the attack surface. + typedef ProgramStateRef (GenericTaintChecker::*FnCheck)(const CallExpr *, + CheckerContext &C) const; + ProgramStateRef postScanf(const CallExpr *CE, CheckerContext &C) const; + ProgramStateRef postSocket(const CallExpr *CE, CheckerContext &C) const; + ProgramStateRef postRetTaint(const CallExpr *CE, CheckerContext &C) const; + + /// Taint the scanned input if the file is tainted. + ProgramStateRef preFscanf(const CallExpr *CE, CheckerContext &C) const; + + /// Check for CWE-134: Uncontrolled Format String. + static const char MsgUncontrolledFormatString[]; + bool checkUncontrolledFormatString(const CallExpr *CE, + CheckerContext &C) const; + + /// Check for: + /// CERT/STR02-C. "Sanitize data passed to complex subsystems" + /// CWE-78, "Failure to Sanitize Data into an OS Command" + static const char MsgSanitizeSystemArgs[]; + bool checkSystemCall(const CallExpr *CE, StringRef Name, + CheckerContext &C) const; + + /// Check if tainted data is used as a buffer size ins strn.. functions, + /// and allocators. + static const char MsgTaintedBufferSize[]; + bool checkTaintedBufferSize(const CallExpr *CE, const FunctionDecl *FDecl, + CheckerContext &C) const; + + /// Generate a report if the expression is tainted or points to tainted data. + bool generateReportIfTainted(const Expr *E, const char Msg[], + CheckerContext &C) const; + + + typedef llvm::SmallVector<unsigned, 2> ArgVector; + + /// \brief A struct used to specify taint propagation rules for a function. + /// + /// If any of the possible taint source arguments is tainted, all of the + /// destination arguments should also be tainted. Use InvalidArgIndex in the + /// src list to specify that all of the arguments can introduce taint. Use + /// InvalidArgIndex in the dst arguments to signify that all the non-const + /// pointer and reference arguments might be tainted on return. If + /// ReturnValueIndex is added to the dst list, the return value will be + /// tainted. + struct TaintPropagationRule { + /// List of arguments which can be taint sources and should be checked. + ArgVector SrcArgs; + /// List of arguments which should be tainted on function return. + ArgVector DstArgs; + // TODO: Check if using other data structures would be more optimal. + + TaintPropagationRule() {} + + TaintPropagationRule(unsigned SArg, + unsigned DArg, bool TaintRet = false) { + SrcArgs.push_back(SArg); + DstArgs.push_back(DArg); + if (TaintRet) + DstArgs.push_back(ReturnValueIndex); + } + + TaintPropagationRule(unsigned SArg1, unsigned SArg2, + unsigned DArg, bool TaintRet = false) { + SrcArgs.push_back(SArg1); + SrcArgs.push_back(SArg2); + DstArgs.push_back(DArg); + if (TaintRet) + DstArgs.push_back(ReturnValueIndex); + } + + /// Get the propagation rule for a given function. + static TaintPropagationRule + getTaintPropagationRule(const FunctionDecl *FDecl, + StringRef Name, + CheckerContext &C); + + inline void addSrcArg(unsigned A) { SrcArgs.push_back(A); } + inline void addDstArg(unsigned A) { DstArgs.push_back(A); } + + inline bool isNull() const { return SrcArgs.empty(); } + + inline bool isDestinationArgument(unsigned ArgNum) const { + return (std::find(DstArgs.begin(), + DstArgs.end(), ArgNum) != DstArgs.end()); + } + + static inline bool isTaintedOrPointsToTainted(const Expr *E, + ProgramStateRef State, + CheckerContext &C) { + return (State->isTainted(E, C.getLocationContext()) || isStdin(E, C) || + (E->getType().getTypePtr()->isPointerType() && + State->isTainted(getPointedToSymbol(C, E)))); + } + + /// \brief Pre-process a function which propagates taint according to the + /// taint rule. + ProgramStateRef process(const CallExpr *CE, CheckerContext &C) const; + + }; +}; + +const unsigned GenericTaintChecker::ReturnValueIndex; +const unsigned GenericTaintChecker::InvalidArgIndex; + +const char GenericTaintChecker::MsgUncontrolledFormatString[] = + "Untrusted data is used as a format string " + "(CWE-134: Uncontrolled Format String)"; + +const char GenericTaintChecker::MsgSanitizeSystemArgs[] = + "Untrusted data is passed to a system call " + "(CERT/STR02-C. Sanitize data passed to complex subsystems)"; + +const char GenericTaintChecker::MsgTaintedBufferSize[] = + "Untrusted data is used to specify the buffer size " + "(CERT/STR31-C. Guarantee that storage for strings has sufficient space for " + "character data and the null terminator)"; + +} // end of anonymous namespace + +/// A set which is used to pass information from call pre-visit instruction +/// to the call post-visit. The values are unsigned integers, which are either +/// ReturnValueIndex, or indexes of the pointer/reference argument, which +/// points to data, which should be tainted on return. +namespace { struct TaintArgsOnPostVisit{}; } +namespace clang { namespace ento { +template<> struct ProgramStateTrait<TaintArgsOnPostVisit> + : public ProgramStatePartialTrait<llvm::ImmutableSet<unsigned> > { + static void *GDMIndex() { return GenericTaintChecker::getTag(); } +}; +}} + +GenericTaintChecker::TaintPropagationRule +GenericTaintChecker::TaintPropagationRule::getTaintPropagationRule( + const FunctionDecl *FDecl, + StringRef Name, + CheckerContext &C) { + // TODO: Currently, we might loose precision here: we always mark a return + // value as tainted even if it's just a pointer, pointing to tainted data. + + // Check for exact name match for functions without builtin substitutes. + TaintPropagationRule Rule = llvm::StringSwitch<TaintPropagationRule>(Name) + .Case("atoi", TaintPropagationRule(0, ReturnValueIndex)) + .Case("atol", TaintPropagationRule(0, ReturnValueIndex)) + .Case("atoll", TaintPropagationRule(0, ReturnValueIndex)) + .Case("getc", TaintPropagationRule(0, ReturnValueIndex)) + .Case("fgetc", TaintPropagationRule(0, ReturnValueIndex)) + .Case("getc_unlocked", TaintPropagationRule(0, ReturnValueIndex)) + .Case("getw", TaintPropagationRule(0, ReturnValueIndex)) + .Case("toupper", TaintPropagationRule(0, ReturnValueIndex)) + .Case("tolower", TaintPropagationRule(0, ReturnValueIndex)) + .Case("strchr", TaintPropagationRule(0, ReturnValueIndex)) + .Case("strrchr", TaintPropagationRule(0, ReturnValueIndex)) + .Case("read", TaintPropagationRule(0, 2, 1, true)) + .Case("pread", TaintPropagationRule(InvalidArgIndex, 1, true)) + .Case("gets", TaintPropagationRule(InvalidArgIndex, 0, true)) + .Case("fgets", TaintPropagationRule(2, 0, true)) + .Case("getline", TaintPropagationRule(2, 0)) + .Case("getdelim", TaintPropagationRule(3, 0)) + .Case("fgetln", TaintPropagationRule(0, ReturnValueIndex)) + .Default(TaintPropagationRule()); + + if (!Rule.isNull()) + return Rule; + + // Check if it's one of the memory setting/copying functions. + // This check is specialized but faster then calling isCLibraryFunction. + unsigned BId = 0; + if ( (BId = FDecl->getMemoryFunctionKind()) ) + switch(BId) { + case Builtin::BImemcpy: + case Builtin::BImemmove: + case Builtin::BIstrncpy: + case Builtin::BIstrncat: + return TaintPropagationRule(1, 2, 0, true); + case Builtin::BIstrlcpy: + case Builtin::BIstrlcat: + return TaintPropagationRule(1, 2, 0, false); + case Builtin::BIstrndup: + return TaintPropagationRule(0, 1, ReturnValueIndex); + + default: + break; + }; + + // Process all other functions which could be defined as builtins. + if (Rule.isNull()) { + if (C.isCLibraryFunction(FDecl, "snprintf") || + C.isCLibraryFunction(FDecl, "sprintf")) + return TaintPropagationRule(InvalidArgIndex, 0, true); + else if (C.isCLibraryFunction(FDecl, "strcpy") || + C.isCLibraryFunction(FDecl, "stpcpy") || + C.isCLibraryFunction(FDecl, "strcat")) + return TaintPropagationRule(1, 0, true); + else if (C.isCLibraryFunction(FDecl, "bcopy")) + return TaintPropagationRule(0, 2, 1, false); + else if (C.isCLibraryFunction(FDecl, "strdup") || + C.isCLibraryFunction(FDecl, "strdupa")) + return TaintPropagationRule(0, ReturnValueIndex); + else if (C.isCLibraryFunction(FDecl, "wcsdup")) + return TaintPropagationRule(0, ReturnValueIndex); + } + + // Skipping the following functions, since they might be used for cleansing + // or smart memory copy: + // - memccpy - copying untill hitting a special character. + + return TaintPropagationRule(); +} + +void GenericTaintChecker::checkPreStmt(const CallExpr *CE, + CheckerContext &C) const { + // Check for errors first. + if (checkPre(CE, C)) + return; + + // Add taint second. + addSourcesPre(CE, C); +} + +void GenericTaintChecker::checkPostStmt(const CallExpr *CE, + CheckerContext &C) const { + if (propagateFromPre(CE, C)) + return; + addSourcesPost(CE, C); +} + +void GenericTaintChecker::addSourcesPre(const CallExpr *CE, + CheckerContext &C) const { + ProgramStateRef State = 0; + const FunctionDecl *FDecl = C.getCalleeDecl(CE); + StringRef Name = C.getCalleeName(FDecl); + if (Name.empty()) + return; + + // First, try generating a propagation rule for this function. + TaintPropagationRule Rule = + TaintPropagationRule::getTaintPropagationRule(FDecl, Name, C); + if (!Rule.isNull()) { + State = Rule.process(CE, C); + if (!State) + return; + C.addTransition(State); + return; + } + + // Otherwise, check if we have custom pre-processing implemented. + FnCheck evalFunction = llvm::StringSwitch<FnCheck>(Name) + .Case("fscanf", &GenericTaintChecker::preFscanf) + .Default(0); + // Check and evaluate the call. + if (evalFunction) + State = (this->*evalFunction)(CE, C); + if (!State) + return; + C.addTransition(State); + +} + +bool GenericTaintChecker::propagateFromPre(const CallExpr *CE, + CheckerContext &C) const { + ProgramStateRef State = C.getState(); + + // Depending on what was tainted at pre-visit, we determined a set of + // arguments which should be tainted after the function returns. These are + // stored in the state as TaintArgsOnPostVisit set. + llvm::ImmutableSet<unsigned> TaintArgs = State->get<TaintArgsOnPostVisit>(); + if (TaintArgs.isEmpty()) + return false; + + for (llvm::ImmutableSet<unsigned>::iterator + I = TaintArgs.begin(), E = TaintArgs.end(); I != E; ++I) { + unsigned ArgNum = *I; + + // Special handling for the tainted return value. + if (ArgNum == ReturnValueIndex) { + State = State->addTaint(CE, C.getLocationContext()); + continue; + } + + // The arguments are pointer arguments. The data they are pointing at is + // tainted after the call. + if (CE->getNumArgs() < (ArgNum + 1)) + return false; + const Expr* Arg = CE->getArg(ArgNum); + SymbolRef Sym = getPointedToSymbol(C, Arg); + if (Sym) + State = State->addTaint(Sym); + } + + // Clear up the taint info from the state. + State = State->remove<TaintArgsOnPostVisit>(); + + if (State != C.getState()) { + C.addTransition(State); + return true; + } + return false; +} + +void GenericTaintChecker::addSourcesPost(const CallExpr *CE, + CheckerContext &C) const { + // Define the attack surface. + // Set the evaluation function by switching on the callee name. + StringRef Name = C.getCalleeName(CE); + if (Name.empty()) + return; + FnCheck evalFunction = llvm::StringSwitch<FnCheck>(Name) + .Case("scanf", &GenericTaintChecker::postScanf) + // TODO: Add support for vfscanf & family. + .Case("getchar", &GenericTaintChecker::postRetTaint) + .Case("getchar_unlocked", &GenericTaintChecker::postRetTaint) + .Case("getenv", &GenericTaintChecker::postRetTaint) + .Case("fopen", &GenericTaintChecker::postRetTaint) + .Case("fdopen", &GenericTaintChecker::postRetTaint) + .Case("freopen", &GenericTaintChecker::postRetTaint) + .Case("getch", &GenericTaintChecker::postRetTaint) + .Case("wgetch", &GenericTaintChecker::postRetTaint) + .Case("socket", &GenericTaintChecker::postSocket) + .Default(0); + + // If the callee isn't defined, it is not of security concern. + // Check and evaluate the call. + ProgramStateRef State = 0; + if (evalFunction) + State = (this->*evalFunction)(CE, C); + if (!State) + return; + + C.addTransition(State); +} + +bool GenericTaintChecker::checkPre(const CallExpr *CE, CheckerContext &C) const{ + + if (checkUncontrolledFormatString(CE, C)) + return true; + + const FunctionDecl *FDecl = C.getCalleeDecl(CE); + StringRef Name = C.getCalleeName(FDecl); + if (Name.empty()) + return false; + + if (checkSystemCall(CE, Name, C)) + return true; + + if (checkTaintedBufferSize(CE, FDecl, C)) + return true; + + return false; +} + +SymbolRef GenericTaintChecker::getPointedToSymbol(CheckerContext &C, + const Expr* Arg) { + ProgramStateRef State = C.getState(); + SVal AddrVal = State->getSVal(Arg->IgnoreParens(), C.getLocationContext()); + if (AddrVal.isUnknownOrUndef()) + return 0; + + Loc *AddrLoc = dyn_cast<Loc>(&AddrVal); + if (!AddrLoc) + return 0; + + const PointerType *ArgTy = + dyn_cast<PointerType>(Arg->getType().getCanonicalType().getTypePtr()); + SVal Val = State->getSVal(*AddrLoc, + ArgTy ? ArgTy->getPointeeType(): QualType()); + return Val.getAsSymbol(); +} + +ProgramStateRef +GenericTaintChecker::TaintPropagationRule::process(const CallExpr *CE, + CheckerContext &C) const { + ProgramStateRef State = C.getState(); + + // Check for taint in arguments. + bool IsTainted = false; + for (ArgVector::const_iterator I = SrcArgs.begin(), + E = SrcArgs.end(); I != E; ++I) { + unsigned ArgNum = *I; + + if (ArgNum == InvalidArgIndex) { + // Check if any of the arguments is tainted, but skip the + // destination arguments. + for (unsigned int i = 0; i < CE->getNumArgs(); ++i) { + if (isDestinationArgument(i)) + continue; + if ((IsTainted = isTaintedOrPointsToTainted(CE->getArg(i), State, C))) + break; + } + break; + } + + if (CE->getNumArgs() < (ArgNum + 1)) + return State; + if ((IsTainted = isTaintedOrPointsToTainted(CE->getArg(ArgNum), State, C))) + break; + } + if (!IsTainted) + return State; + + // Mark the arguments which should be tainted after the function returns. + for (ArgVector::const_iterator I = DstArgs.begin(), + E = DstArgs.end(); I != E; ++I) { + unsigned ArgNum = *I; + + // Should we mark all arguments as tainted? + if (ArgNum == InvalidArgIndex) { + // For all pointer and references that were passed in: + // If they are not pointing to const data, mark data as tainted. + // TODO: So far we are just going one level down; ideally we'd need to + // recurse here. + for (unsigned int i = 0; i < CE->getNumArgs(); ++i) { + const Expr *Arg = CE->getArg(i); + // Process pointer argument. + const Type *ArgTy = Arg->getType().getTypePtr(); + QualType PType = ArgTy->getPointeeType(); + if ((!PType.isNull() && !PType.isConstQualified()) + || (ArgTy->isReferenceType() && !Arg->getType().isConstQualified())) + State = State->add<TaintArgsOnPostVisit>(i); + } + continue; + } + + // Should mark the return value? + if (ArgNum == ReturnValueIndex) { + State = State->add<TaintArgsOnPostVisit>(ReturnValueIndex); + continue; + } + + // Mark the given argument. + assert(ArgNum < CE->getNumArgs()); + State = State->add<TaintArgsOnPostVisit>(ArgNum); + } + + return State; +} + + +// If argument 0 (file descriptor) is tainted, all arguments except for arg 0 +// and arg 1 should get taint. +ProgramStateRef GenericTaintChecker::preFscanf(const CallExpr *CE, + CheckerContext &C) const { + assert(CE->getNumArgs() >= 2); + ProgramStateRef State = C.getState(); + + // Check is the file descriptor is tainted. + if (State->isTainted(CE->getArg(0), C.getLocationContext()) || + isStdin(CE->getArg(0), C)) { + // All arguments except for the first two should get taint. + for (unsigned int i = 2; i < CE->getNumArgs(); ++i) + State = State->add<TaintArgsOnPostVisit>(i); + return State; + } + + return 0; +} + + +// If argument 0(protocol domain) is network, the return value should get taint. +ProgramStateRef GenericTaintChecker::postSocket(const CallExpr *CE, + CheckerContext &C) const { + ProgramStateRef State = C.getState(); + if (CE->getNumArgs() < 3) + return State; + + SourceLocation DomLoc = CE->getArg(0)->getExprLoc(); + StringRef DomName = C.getMacroNameOrSpelling(DomLoc); + // White list the internal communication protocols. + if (DomName.equals("AF_SYSTEM") || DomName.equals("AF_LOCAL") || + DomName.equals("AF_UNIX") || DomName.equals("AF_RESERVED_36")) + return State; + State = State->addTaint(CE, C.getLocationContext()); + return State; +} + +ProgramStateRef GenericTaintChecker::postScanf(const CallExpr *CE, + CheckerContext &C) const { + ProgramStateRef State = C.getState(); + if (CE->getNumArgs() < 2) + return State; + + SVal x = State->getSVal(CE->getArg(1), C.getLocationContext()); + // All arguments except for the very first one should get taint. + for (unsigned int i = 1; i < CE->getNumArgs(); ++i) { + // The arguments are pointer arguments. The data they are pointing at is + // tainted after the call. + const Expr* Arg = CE->getArg(i); + SymbolRef Sym = getPointedToSymbol(C, Arg); + if (Sym) + State = State->addTaint(Sym); + } + return State; +} + +ProgramStateRef GenericTaintChecker::postRetTaint(const CallExpr *CE, + CheckerContext &C) const { + return C.getState()->addTaint(CE, C.getLocationContext()); +} + +bool GenericTaintChecker::isStdin(const Expr *E, CheckerContext &C) { + ProgramStateRef State = C.getState(); + SVal Val = State->getSVal(E, C.getLocationContext()); + + // stdin is a pointer, so it would be a region. + const MemRegion *MemReg = Val.getAsRegion(); + + // The region should be symbolic, we do not know it's value. + const SymbolicRegion *SymReg = dyn_cast_or_null<SymbolicRegion>(MemReg); + if (!SymReg) + return false; + + // Get it's symbol and find the declaration region it's pointing to. + const SymbolRegionValue *Sm =dyn_cast<SymbolRegionValue>(SymReg->getSymbol()); + if (!Sm) + return false; + const DeclRegion *DeclReg = dyn_cast_or_null<DeclRegion>(Sm->getRegion()); + if (!DeclReg) + return false; + + // This region corresponds to a declaration, find out if it's a global/extern + // variable named stdin with the proper type. + if (const VarDecl *D = dyn_cast_or_null<VarDecl>(DeclReg->getDecl())) { + D = D->getCanonicalDecl(); + if ((D->getName().find("stdin") != StringRef::npos) && D->isExternC()) + if (const PointerType * PtrTy = + dyn_cast<PointerType>(D->getType().getTypePtr())) + if (PtrTy->getPointeeType() == C.getASTContext().getFILEType()) + return true; + } + return false; +} + +static bool getPrintfFormatArgumentNum(const CallExpr *CE, + const CheckerContext &C, + unsigned int &ArgNum) { + // Find if the function contains a format string argument. + // Handles: fprintf, printf, sprintf, snprintf, vfprintf, vprintf, vsprintf, + // vsnprintf, syslog, custom annotated functions. + const FunctionDecl *FDecl = C.getCalleeDecl(CE); + if (!FDecl) + return false; + for (specific_attr_iterator<FormatAttr> + i = FDecl->specific_attr_begin<FormatAttr>(), + e = FDecl->specific_attr_end<FormatAttr>(); i != e ; ++i) { + + const FormatAttr *Format = *i; + ArgNum = Format->getFormatIdx() - 1; + if ((Format->getType() == "printf") && CE->getNumArgs() > ArgNum) + return true; + } + + // Or if a function is named setproctitle (this is a heuristic). + if (C.getCalleeName(CE).find("setproctitle") != StringRef::npos) { + ArgNum = 0; + return true; + } + + return false; +} + +bool GenericTaintChecker::generateReportIfTainted(const Expr *E, + const char Msg[], + CheckerContext &C) const { + assert(E); + + // Check for taint. + ProgramStateRef State = C.getState(); + if (!State->isTainted(getPointedToSymbol(C, E)) && + !State->isTainted(E, C.getLocationContext())) + return false; + + // Generate diagnostic. + if (ExplodedNode *N = C.addTransition()) { + initBugType(); + BugReport *report = new BugReport(*BT, Msg, N); + report->addRange(E->getSourceRange()); + C.EmitReport(report); + return true; + } + return false; +} + +bool GenericTaintChecker::checkUncontrolledFormatString(const CallExpr *CE, + CheckerContext &C) const{ + // Check if the function contains a format string argument. + unsigned int ArgNum = 0; + if (!getPrintfFormatArgumentNum(CE, C, ArgNum)) + return false; + + // If either the format string content or the pointer itself are tainted, warn. + if (generateReportIfTainted(CE->getArg(ArgNum), + MsgUncontrolledFormatString, C)) + return true; + return false; +} + +bool GenericTaintChecker::checkSystemCall(const CallExpr *CE, + StringRef Name, + CheckerContext &C) const { + // TODO: It might make sense to run this check on demand. In some cases, + // we should check if the environment has been cleansed here. We also might + // need to know if the user was reset before these calls(seteuid). + unsigned ArgNum = llvm::StringSwitch<unsigned>(Name) + .Case("system", 0) + .Case("popen", 0) + .Case("execl", 0) + .Case("execle", 0) + .Case("execlp", 0) + .Case("execv", 0) + .Case("execvp", 0) + .Case("execvP", 0) + .Case("execve", 0) + .Case("dlopen", 0) + .Default(UINT_MAX); + + if (ArgNum == UINT_MAX || CE->getNumArgs() < (ArgNum + 1)) + return false; + + if (generateReportIfTainted(CE->getArg(ArgNum), + MsgSanitizeSystemArgs, C)) + return true; + + return false; +} + +// TODO: Should this check be a part of the CString checker? +// If yes, should taint be a global setting? +bool GenericTaintChecker::checkTaintedBufferSize(const CallExpr *CE, + const FunctionDecl *FDecl, + CheckerContext &C) const { + // If the function has a buffer size argument, set ArgNum. + unsigned ArgNum = InvalidArgIndex; + unsigned BId = 0; + if ( (BId = FDecl->getMemoryFunctionKind()) ) + switch(BId) { + case Builtin::BImemcpy: + case Builtin::BImemmove: + case Builtin::BIstrncpy: + ArgNum = 2; + break; + case Builtin::BIstrndup: + ArgNum = 1; + break; + default: + break; + }; + + if (ArgNum == InvalidArgIndex) { + if (C.isCLibraryFunction(FDecl, "malloc") || + C.isCLibraryFunction(FDecl, "calloc") || + C.isCLibraryFunction(FDecl, "alloca")) + ArgNum = 0; + else if (C.isCLibraryFunction(FDecl, "memccpy")) + ArgNum = 3; + else if (C.isCLibraryFunction(FDecl, "realloc")) + ArgNum = 1; + else if (C.isCLibraryFunction(FDecl, "bcopy")) + ArgNum = 2; + } + + if (ArgNum != InvalidArgIndex && CE->getNumArgs() > ArgNum && + generateReportIfTainted(CE->getArg(ArgNum), MsgTaintedBufferSize, C)) + return true; + + return false; +} + +void ento::registerGenericTaintChecker(CheckerManager &mgr) { + mgr.registerChecker<GenericTaintChecker>(); +} |