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Diffstat (limited to 'gnu/llvm/clang/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp')
| -rw-r--r-- | gnu/llvm/clang/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp | 1105 |
1 files changed, 1105 insertions, 0 deletions
diff --git a/gnu/llvm/clang/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp b/gnu/llvm/clang/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp new file mode 100644 index 00000000000..d9ffa562c0a --- /dev/null +++ b/gnu/llvm/clang/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp @@ -0,0 +1,1105 @@ +//==- CheckSecuritySyntaxOnly.cpp - Basic security checks --------*- C++ -*-==// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This file defines a set of flow-insensitive security checks. +// +//===----------------------------------------------------------------------===// + +#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" +#include "clang/AST/StmtVisitor.h" +#include "clang/Analysis/AnalysisDeclContext.h" +#include "clang/Basic/TargetInfo.h" +#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h" +#include "clang/StaticAnalyzer/Core/Checker.h" +#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h" +#include "llvm/ADT/SmallString.h" +#include "llvm/ADT/StringSwitch.h" +#include "llvm/Support/raw_ostream.h" + +using namespace clang; +using namespace ento; + +static bool isArc4RandomAvailable(const ASTContext &Ctx) { + const llvm::Triple &T = Ctx.getTargetInfo().getTriple(); + return T.getVendor() == llvm::Triple::Apple || + T.getOS() == llvm::Triple::CloudABI || + T.isOSFreeBSD() || + T.isOSNetBSD() || + T.isOSOpenBSD() || + T.isOSDragonFly(); +} + +namespace { +struct ChecksFilter { + DefaultBool check_bcmp; + DefaultBool check_bcopy; + DefaultBool check_bzero; + DefaultBool check_gets; + DefaultBool check_getpw; + DefaultBool check_mktemp; + DefaultBool check_mkstemp; + DefaultBool check_strcpy; + DefaultBool check_DeprecatedOrUnsafeBufferHandling; + DefaultBool check_rand; + DefaultBool check_vfork; + DefaultBool check_FloatLoopCounter; + DefaultBool check_UncheckedReturn; + DefaultBool check_decodeValueOfObjCType; + + CheckerNameRef checkName_bcmp; + CheckerNameRef checkName_bcopy; + CheckerNameRef checkName_bzero; + CheckerNameRef checkName_gets; + CheckerNameRef checkName_getpw; + CheckerNameRef checkName_mktemp; + CheckerNameRef checkName_mkstemp; + CheckerNameRef checkName_strcpy; + CheckerNameRef checkName_DeprecatedOrUnsafeBufferHandling; + CheckerNameRef checkName_rand; + CheckerNameRef checkName_vfork; + CheckerNameRef checkName_FloatLoopCounter; + CheckerNameRef checkName_UncheckedReturn; + CheckerNameRef checkName_decodeValueOfObjCType; +}; + +class WalkAST : public StmtVisitor<WalkAST> { + BugReporter &BR; + AnalysisDeclContext* AC; + enum { num_setids = 6 }; + IdentifierInfo *II_setid[num_setids]; + + const bool CheckRand; + const ChecksFilter &filter; + +public: + WalkAST(BugReporter &br, AnalysisDeclContext* ac, + const ChecksFilter &f) + : BR(br), AC(ac), II_setid(), + CheckRand(isArc4RandomAvailable(BR.getContext())), + filter(f) {} + + // Statement visitor methods. + void VisitCallExpr(CallExpr *CE); + void VisitObjCMessageExpr(ObjCMessageExpr *CE); + void VisitForStmt(ForStmt *S); + void VisitCompoundStmt (CompoundStmt *S); + void VisitStmt(Stmt *S) { VisitChildren(S); } + + void VisitChildren(Stmt *S); + + // Helpers. + bool checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD); + + typedef void (WalkAST::*FnCheck)(const CallExpr *, const FunctionDecl *); + typedef void (WalkAST::*MsgCheck)(const ObjCMessageExpr *); + + // Checker-specific methods. + void checkLoopConditionForFloat(const ForStmt *FS); + void checkCall_bcmp(const CallExpr *CE, const FunctionDecl *FD); + void checkCall_bcopy(const CallExpr *CE, const FunctionDecl *FD); + void checkCall_bzero(const CallExpr *CE, const FunctionDecl *FD); + void checkCall_gets(const CallExpr *CE, const FunctionDecl *FD); + void checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD); + void checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD); + void checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD); + void checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD); + void checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD); + void checkDeprecatedOrUnsafeBufferHandling(const CallExpr *CE, + const FunctionDecl *FD); + void checkCall_rand(const CallExpr *CE, const FunctionDecl *FD); + void checkCall_random(const CallExpr *CE, const FunctionDecl *FD); + void checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD); + void checkMsg_decodeValueOfObjCType(const ObjCMessageExpr *ME); + void checkUncheckedReturnValue(CallExpr *CE); +}; +} // end anonymous namespace + +//===----------------------------------------------------------------------===// +// AST walking. +//===----------------------------------------------------------------------===// + +void WalkAST::VisitChildren(Stmt *S) { + for (Stmt *Child : S->children()) + if (Child) + Visit(Child); +} + +void WalkAST::VisitCallExpr(CallExpr *CE) { + // Get the callee. + const FunctionDecl *FD = CE->getDirectCallee(); + + if (!FD) + return; + + // Get the name of the callee. If it's a builtin, strip off the prefix. + IdentifierInfo *II = FD->getIdentifier(); + if (!II) // if no identifier, not a simple C function + return; + StringRef Name = II->getName(); + if (Name.startswith("__builtin_")) + Name = Name.substr(10); + + // Set the evaluation function by switching on the callee name. + FnCheck evalFunction = llvm::StringSwitch<FnCheck>(Name) + .Case("bcmp", &WalkAST::checkCall_bcmp) + .Case("bcopy", &WalkAST::checkCall_bcopy) + .Case("bzero", &WalkAST::checkCall_bzero) + .Case("gets", &WalkAST::checkCall_gets) + .Case("getpw", &WalkAST::checkCall_getpw) + .Case("mktemp", &WalkAST::checkCall_mktemp) + .Case("mkstemp", &WalkAST::checkCall_mkstemp) + .Case("mkdtemp", &WalkAST::checkCall_mkstemp) + .Case("mkstemps", &WalkAST::checkCall_mkstemp) + .Cases("strcpy", "__strcpy_chk", &WalkAST::checkCall_strcpy) + .Cases("strcat", "__strcat_chk", &WalkAST::checkCall_strcat) + .Cases("sprintf", "vsprintf", "scanf", "wscanf", "fscanf", "fwscanf", + "vscanf", "vwscanf", "vfscanf", "vfwscanf", + &WalkAST::checkDeprecatedOrUnsafeBufferHandling) + .Cases("sscanf", "swscanf", "vsscanf", "vswscanf", "swprintf", + "snprintf", "vswprintf", "vsnprintf", "memcpy", "memmove", + &WalkAST::checkDeprecatedOrUnsafeBufferHandling) + .Cases("strncpy", "strncat", "memset", + &WalkAST::checkDeprecatedOrUnsafeBufferHandling) + .Case("drand48", &WalkAST::checkCall_rand) + .Case("erand48", &WalkAST::checkCall_rand) + .Case("jrand48", &WalkAST::checkCall_rand) + .Case("lrand48", &WalkAST::checkCall_rand) + .Case("mrand48", &WalkAST::checkCall_rand) + .Case("nrand48", &WalkAST::checkCall_rand) + .Case("lcong48", &WalkAST::checkCall_rand) + .Case("rand", &WalkAST::checkCall_rand) + .Case("rand_r", &WalkAST::checkCall_rand) + .Case("random", &WalkAST::checkCall_random) + .Case("vfork", &WalkAST::checkCall_vfork) + .Default(nullptr); + + // If the callee isn't defined, it is not of security concern. + // Check and evaluate the call. + if (evalFunction) + (this->*evalFunction)(CE, FD); + + // Recurse and check children. + VisitChildren(CE); +} + +void WalkAST::VisitObjCMessageExpr(ObjCMessageExpr *ME) { + MsgCheck evalFunction = + llvm::StringSwitch<MsgCheck>(ME->getSelector().getAsString()) + .Case("decodeValueOfObjCType:at:", + &WalkAST::checkMsg_decodeValueOfObjCType) + .Default(nullptr); + + if (evalFunction) + (this->*evalFunction)(ME); + + // Recurse and check children. + VisitChildren(ME); +} + +void WalkAST::VisitCompoundStmt(CompoundStmt *S) { + for (Stmt *Child : S->children()) + if (Child) { + if (CallExpr *CE = dyn_cast<CallExpr>(Child)) + checkUncheckedReturnValue(CE); + Visit(Child); + } +} + +void WalkAST::VisitForStmt(ForStmt *FS) { + checkLoopConditionForFloat(FS); + + // Recurse and check children. + VisitChildren(FS); +} + +//===----------------------------------------------------------------------===// +// Check: floating point variable used as loop counter. +// Originally: <rdar://problem/6336718> +// Implements: CERT security coding advisory FLP-30. +//===----------------------------------------------------------------------===// + +// Returns either 'x' or 'y', depending on which one of them is incremented +// in 'expr', or nullptr if none of them is incremented. +static const DeclRefExpr* +getIncrementedVar(const Expr *expr, const VarDecl *x, const VarDecl *y) { + expr = expr->IgnoreParenCasts(); + + if (const BinaryOperator *B = dyn_cast<BinaryOperator>(expr)) { + if (!(B->isAssignmentOp() || B->isCompoundAssignmentOp() || + B->getOpcode() == BO_Comma)) + return nullptr; + + if (const DeclRefExpr *lhs = getIncrementedVar(B->getLHS(), x, y)) + return lhs; + + if (const DeclRefExpr *rhs = getIncrementedVar(B->getRHS(), x, y)) + return rhs; + + return nullptr; + } + + if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(expr)) { + const NamedDecl *ND = DR->getDecl(); + return ND == x || ND == y ? DR : nullptr; + } + + if (const UnaryOperator *U = dyn_cast<UnaryOperator>(expr)) + return U->isIncrementDecrementOp() + ? getIncrementedVar(U->getSubExpr(), x, y) : nullptr; + + return nullptr; +} + +/// CheckLoopConditionForFloat - This check looks for 'for' statements that +/// use a floating point variable as a loop counter. +/// CERT: FLP30-C, FLP30-CPP. +/// +void WalkAST::checkLoopConditionForFloat(const ForStmt *FS) { + if (!filter.check_FloatLoopCounter) + return; + + // Does the loop have a condition? + const Expr *condition = FS->getCond(); + + if (!condition) + return; + + // Does the loop have an increment? + const Expr *increment = FS->getInc(); + + if (!increment) + return; + + // Strip away '()' and casts. + condition = condition->IgnoreParenCasts(); + increment = increment->IgnoreParenCasts(); + + // Is the loop condition a comparison? + const BinaryOperator *B = dyn_cast<BinaryOperator>(condition); + + if (!B) + return; + + // Is this a comparison? + if (!(B->isRelationalOp() || B->isEqualityOp())) + return; + + // Are we comparing variables? + const DeclRefExpr *drLHS = + dyn_cast<DeclRefExpr>(B->getLHS()->IgnoreParenLValueCasts()); + const DeclRefExpr *drRHS = + dyn_cast<DeclRefExpr>(B->getRHS()->IgnoreParenLValueCasts()); + + // Does at least one of the variables have a floating point type? + drLHS = drLHS && drLHS->getType()->isRealFloatingType() ? drLHS : nullptr; + drRHS = drRHS && drRHS->getType()->isRealFloatingType() ? drRHS : nullptr; + + if (!drLHS && !drRHS) + return; + + const VarDecl *vdLHS = drLHS ? dyn_cast<VarDecl>(drLHS->getDecl()) : nullptr; + const VarDecl *vdRHS = drRHS ? dyn_cast<VarDecl>(drRHS->getDecl()) : nullptr; + + if (!vdLHS && !vdRHS) + return; + + // Does either variable appear in increment? + const DeclRefExpr *drInc = getIncrementedVar(increment, vdLHS, vdRHS); + if (!drInc) + return; + + const VarDecl *vdInc = cast<VarDecl>(drInc->getDecl()); + assert(vdInc && (vdInc == vdLHS || vdInc == vdRHS)); + + // Emit the error. First figure out which DeclRefExpr in the condition + // referenced the compared variable. + const DeclRefExpr *drCond = vdLHS == vdInc ? drLHS : drRHS; + + SmallVector<SourceRange, 2> ranges; + SmallString<256> sbuf; + llvm::raw_svector_ostream os(sbuf); + + os << "Variable '" << drCond->getDecl()->getName() + << "' with floating point type '" << drCond->getType().getAsString() + << "' should not be used as a loop counter"; + + ranges.push_back(drCond->getSourceRange()); + ranges.push_back(drInc->getSourceRange()); + + const char *bugType = "Floating point variable used as loop counter"; + + PathDiagnosticLocation FSLoc = + PathDiagnosticLocation::createBegin(FS, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_FloatLoopCounter, + bugType, "Security", os.str(), + FSLoc, ranges); +} + +//===----------------------------------------------------------------------===// +// Check: Any use of bcmp. +// CWE-477: Use of Obsolete Functions +// bcmp was deprecated in POSIX.1-2008 +//===----------------------------------------------------------------------===// + +void WalkAST::checkCall_bcmp(const CallExpr *CE, const FunctionDecl *FD) { + if (!filter.check_bcmp) + return; + + const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); + if (!FPT) + return; + + // Verify that the function takes three arguments. + if (FPT->getNumParams() != 3) + return; + + for (int i = 0; i < 2; i++) { + // Verify the first and second argument type is void*. + const PointerType *PT = FPT->getParamType(i)->getAs<PointerType>(); + if (!PT) + return; + + if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().VoidTy) + return; + } + + // Verify the third argument type is integer. + if (!FPT->getParamType(2)->isIntegralOrUnscopedEnumerationType()) + return; + + // Issue a warning. + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_bcmp, + "Use of deprecated function in call to 'bcmp()'", + "Security", + "The bcmp() function is obsoleted by memcmp().", + CELoc, CE->getCallee()->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Check: Any use of bcopy. +// CWE-477: Use of Obsolete Functions +// bcopy was deprecated in POSIX.1-2008 +//===----------------------------------------------------------------------===// + +void WalkAST::checkCall_bcopy(const CallExpr *CE, const FunctionDecl *FD) { + if (!filter.check_bcopy) + return; + + const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); + if (!FPT) + return; + + // Verify that the function takes three arguments. + if (FPT->getNumParams() != 3) + return; + + for (int i = 0; i < 2; i++) { + // Verify the first and second argument type is void*. + const PointerType *PT = FPT->getParamType(i)->getAs<PointerType>(); + if (!PT) + return; + + if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().VoidTy) + return; + } + + // Verify the third argument type is integer. + if (!FPT->getParamType(2)->isIntegralOrUnscopedEnumerationType()) + return; + + // Issue a warning. + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_bcopy, + "Use of deprecated function in call to 'bcopy()'", + "Security", + "The bcopy() function is obsoleted by memcpy() " + "or memmove().", + CELoc, CE->getCallee()->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Check: Any use of bzero. +// CWE-477: Use of Obsolete Functions +// bzero was deprecated in POSIX.1-2008 +//===----------------------------------------------------------------------===// + +void WalkAST::checkCall_bzero(const CallExpr *CE, const FunctionDecl *FD) { + if (!filter.check_bzero) + return; + + const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); + if (!FPT) + return; + + // Verify that the function takes two arguments. + if (FPT->getNumParams() != 2) + return; + + // Verify the first argument type is void*. + const PointerType *PT = FPT->getParamType(0)->getAs<PointerType>(); + if (!PT) + return; + + if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().VoidTy) + return; + + // Verify the second argument type is integer. + if (!FPT->getParamType(1)->isIntegralOrUnscopedEnumerationType()) + return; + + // Issue a warning. + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_bzero, + "Use of deprecated function in call to 'bzero()'", + "Security", + "The bzero() function is obsoleted by memset().", + CELoc, CE->getCallee()->getSourceRange()); +} + + +//===----------------------------------------------------------------------===// +// Check: Any use of 'gets' is insecure. +// Originally: <rdar://problem/6335715> +// Implements (part of): 300-BSI (buildsecurityin.us-cert.gov) +// CWE-242: Use of Inherently Dangerous Function +//===----------------------------------------------------------------------===// + +void WalkAST::checkCall_gets(const CallExpr *CE, const FunctionDecl *FD) { + if (!filter.check_gets) + return; + + const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); + if (!FPT) + return; + + // Verify that the function takes a single argument. + if (FPT->getNumParams() != 1) + return; + + // Is the argument a 'char*'? + const PointerType *PT = FPT->getParamType(0)->getAs<PointerType>(); + if (!PT) + return; + + if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) + return; + + // Issue a warning. + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_gets, + "Potential buffer overflow in call to 'gets'", + "Security", + "Call to function 'gets' is extremely insecure as it can " + "always result in a buffer overflow", + CELoc, CE->getCallee()->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Check: Any use of 'getpwd' is insecure. +// CWE-477: Use of Obsolete Functions +//===----------------------------------------------------------------------===// + +void WalkAST::checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD) { + if (!filter.check_getpw) + return; + + const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); + if (!FPT) + return; + + // Verify that the function takes two arguments. + if (FPT->getNumParams() != 2) + return; + + // Verify the first argument type is integer. + if (!FPT->getParamType(0)->isIntegralOrUnscopedEnumerationType()) + return; + + // Verify the second argument type is char*. + const PointerType *PT = FPT->getParamType(1)->getAs<PointerType>(); + if (!PT) + return; + + if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) + return; + + // Issue a warning. + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_getpw, + "Potential buffer overflow in call to 'getpw'", + "Security", + "The getpw() function is dangerous as it may overflow the " + "provided buffer. It is obsoleted by getpwuid().", + CELoc, CE->getCallee()->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Check: Any use of 'mktemp' is insecure. It is obsoleted by mkstemp(). +// CWE-377: Insecure Temporary File +//===----------------------------------------------------------------------===// + +void WalkAST::checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD) { + if (!filter.check_mktemp) { + // Fall back to the security check of looking for enough 'X's in the + // format string, since that is a less severe warning. + checkCall_mkstemp(CE, FD); + return; + } + + const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); + if(!FPT) + return; + + // Verify that the function takes a single argument. + if (FPT->getNumParams() != 1) + return; + + // Verify that the argument is Pointer Type. + const PointerType *PT = FPT->getParamType(0)->getAs<PointerType>(); + if (!PT) + return; + + // Verify that the argument is a 'char*'. + if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) + return; + + // Issue a warning. + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_mktemp, + "Potential insecure temporary file in call 'mktemp'", + "Security", + "Call to function 'mktemp' is insecure as it always " + "creates or uses insecure temporary file. Use 'mkstemp' " + "instead", + CELoc, CE->getCallee()->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Check: Use of 'mkstemp', 'mktemp', 'mkdtemp' should contain at least 6 X's. +//===----------------------------------------------------------------------===// + +void WalkAST::checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD) { + if (!filter.check_mkstemp) + return; + + StringRef Name = FD->getIdentifier()->getName(); + std::pair<signed, signed> ArgSuffix = + llvm::StringSwitch<std::pair<signed, signed> >(Name) + .Case("mktemp", std::make_pair(0,-1)) + .Case("mkstemp", std::make_pair(0,-1)) + .Case("mkdtemp", std::make_pair(0,-1)) + .Case("mkstemps", std::make_pair(0,1)) + .Default(std::make_pair(-1, -1)); + + assert(ArgSuffix.first >= 0 && "Unsupported function"); + + // Check if the number of arguments is consistent with out expectations. + unsigned numArgs = CE->getNumArgs(); + if ((signed) numArgs <= ArgSuffix.first) + return; + + const StringLiteral *strArg = + dyn_cast<StringLiteral>(CE->getArg((unsigned)ArgSuffix.first) + ->IgnoreParenImpCasts()); + + // Currently we only handle string literals. It is possible to do better, + // either by looking at references to const variables, or by doing real + // flow analysis. + if (!strArg || strArg->getCharByteWidth() != 1) + return; + + // Count the number of X's, taking into account a possible cutoff suffix. + StringRef str = strArg->getString(); + unsigned numX = 0; + unsigned n = str.size(); + + // Take into account the suffix. + unsigned suffix = 0; + if (ArgSuffix.second >= 0) { + const Expr *suffixEx = CE->getArg((unsigned)ArgSuffix.second); + Expr::EvalResult EVResult; + if (!suffixEx->EvaluateAsInt(EVResult, BR.getContext())) + return; + llvm::APSInt Result = EVResult.Val.getInt(); + // FIXME: Issue a warning. + if (Result.isNegative()) + return; + suffix = (unsigned) Result.getZExtValue(); + n = (n > suffix) ? n - suffix : 0; + } + + for (unsigned i = 0; i < n; ++i) + if (str[i] == 'X') ++numX; + + if (numX >= 6) + return; + + // Issue a warning. + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + SmallString<512> buf; + llvm::raw_svector_ostream out(buf); + out << "Call to '" << Name << "' should have at least 6 'X's in the" + " format string to be secure (" << numX << " 'X'"; + if (numX != 1) + out << 's'; + out << " seen"; + if (suffix) { + out << ", " << suffix << " character"; + if (suffix > 1) + out << 's'; + out << " used as a suffix"; + } + out << ')'; + BR.EmitBasicReport(AC->getDecl(), filter.checkName_mkstemp, + "Insecure temporary file creation", "Security", + out.str(), CELoc, strArg->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Check: Any use of 'strcpy' is insecure. +// +// CWE-119: Improper Restriction of Operations within +// the Bounds of a Memory Buffer +//===----------------------------------------------------------------------===// + +void WalkAST::checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD) { + if (!filter.check_strcpy) + return; + + if (!checkCall_strCommon(CE, FD)) + return; + + const auto *Target = CE->getArg(0)->IgnoreImpCasts(), + *Source = CE->getArg(1)->IgnoreImpCasts(); + + if (const auto *Array = dyn_cast<ConstantArrayType>(Target->getType())) { + uint64_t ArraySize = BR.getContext().getTypeSize(Array) / 8; + if (const auto *String = dyn_cast<StringLiteral>(Source)) { + if (ArraySize >= String->getLength() + 1) + return; + } + } + + // Issue a warning. + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_strcpy, + "Potential insecure memory buffer bounds restriction in " + "call 'strcpy'", + "Security", + "Call to function 'strcpy' is insecure as it does not " + "provide bounding of the memory buffer. Replace " + "unbounded copy functions with analogous functions that " + "support length arguments such as 'strlcpy'. CWE-119.", + CELoc, CE->getCallee()->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Check: Any use of 'strcat' is insecure. +// +// CWE-119: Improper Restriction of Operations within +// the Bounds of a Memory Buffer +//===----------------------------------------------------------------------===// + +void WalkAST::checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD) { + if (!filter.check_strcpy) + return; + + if (!checkCall_strCommon(CE, FD)) + return; + + // Issue a warning. + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_strcpy, + "Potential insecure memory buffer bounds restriction in " + "call 'strcat'", + "Security", + "Call to function 'strcat' is insecure as it does not " + "provide bounding of the memory buffer. Replace " + "unbounded copy functions with analogous functions that " + "support length arguments such as 'strlcat'. CWE-119.", + CELoc, CE->getCallee()->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Check: Any use of 'sprintf', 'vsprintf', 'scanf', 'wscanf', 'fscanf', +// 'fwscanf', 'vscanf', 'vwscanf', 'vfscanf', 'vfwscanf', 'sscanf', +// 'swscanf', 'vsscanf', 'vswscanf', 'swprintf', 'snprintf', 'vswprintf', +// 'vsnprintf', 'memcpy', 'memmove', 'strncpy', 'strncat', 'memset' +// is deprecated since C11. +// +// Use of 'sprintf', 'vsprintf', 'scanf', 'wscanf','fscanf', +// 'fwscanf', 'vscanf', 'vwscanf', 'vfscanf', 'vfwscanf', 'sscanf', +// 'swscanf', 'vsscanf', 'vswscanf' without buffer limitations +// is insecure. +// +// CWE-119: Improper Restriction of Operations within +// the Bounds of a Memory Buffer +//===----------------------------------------------------------------------===// + +void WalkAST::checkDeprecatedOrUnsafeBufferHandling(const CallExpr *CE, + const FunctionDecl *FD) { + if (!filter.check_DeprecatedOrUnsafeBufferHandling) + return; + + if (!BR.getContext().getLangOpts().C11) + return; + + // Issue a warning. ArgIndex == -1: Deprecated but not unsafe (has size + // restrictions). + enum { DEPR_ONLY = -1, UNKNOWN_CALL = -2 }; + + StringRef Name = FD->getIdentifier()->getName(); + if (Name.startswith("__builtin_")) + Name = Name.substr(10); + + int ArgIndex = + llvm::StringSwitch<int>(Name) + .Cases("scanf", "wscanf", "vscanf", "vwscanf", 0) + .Cases("sprintf", "vsprintf", "fscanf", "fwscanf", "vfscanf", + "vfwscanf", "sscanf", "swscanf", "vsscanf", "vswscanf", 1) + .Cases("swprintf", "snprintf", "vswprintf", "vsnprintf", "memcpy", + "memmove", "memset", "strncpy", "strncat", DEPR_ONLY) + .Default(UNKNOWN_CALL); + + assert(ArgIndex != UNKNOWN_CALL && "Unsupported function"); + bool BoundsProvided = ArgIndex == DEPR_ONLY; + + if (!BoundsProvided) { + // Currently we only handle (not wide) string literals. It is possible to do + // better, either by looking at references to const variables, or by doing + // real flow analysis. + auto FormatString = + dyn_cast<StringLiteral>(CE->getArg(ArgIndex)->IgnoreParenImpCasts()); + if (FormatString && + FormatString->getString().find("%s") == StringRef::npos && + FormatString->getString().find("%[") == StringRef::npos) + BoundsProvided = true; + } + + SmallString<128> Buf1; + SmallString<512> Buf2; + llvm::raw_svector_ostream Out1(Buf1); + llvm::raw_svector_ostream Out2(Buf2); + + Out1 << "Potential insecure memory buffer bounds restriction in call '" + << Name << "'"; + Out2 << "Call to function '" << Name + << "' is insecure as it does not provide "; + + if (!BoundsProvided) { + Out2 << "bounding of the memory buffer or "; + } + + Out2 << "security checks introduced " + "in the C11 standard. Replace with analogous functions that " + "support length arguments or provides boundary checks such as '" + << Name << "_s' in case of C11"; + + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), + filter.checkName_DeprecatedOrUnsafeBufferHandling, + Out1.str(), "Security", Out2.str(), CELoc, + CE->getCallee()->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Common check for str* functions with no bounds parameters. +//===----------------------------------------------------------------------===// + +bool WalkAST::checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD) { + const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>(); + if (!FPT) + return false; + + // Verify the function takes two arguments, three in the _chk version. + int numArgs = FPT->getNumParams(); + if (numArgs != 2 && numArgs != 3) + return false; + + // Verify the type for both arguments. + for (int i = 0; i < 2; i++) { + // Verify that the arguments are pointers. + const PointerType *PT = FPT->getParamType(i)->getAs<PointerType>(); + if (!PT) + return false; + + // Verify that the argument is a 'char*'. + if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy) + return false; + } + + return true; +} + +//===----------------------------------------------------------------------===// +// Check: Linear congruent random number generators should not be used +// Originally: <rdar://problem/63371000> +// CWE-338: Use of cryptographically weak prng +//===----------------------------------------------------------------------===// + +void WalkAST::checkCall_rand(const CallExpr *CE, const FunctionDecl *FD) { + if (!filter.check_rand || !CheckRand) + return; + + const FunctionProtoType *FTP = FD->getType()->getAs<FunctionProtoType>(); + if (!FTP) + return; + + if (FTP->getNumParams() == 1) { + // Is the argument an 'unsigned short *'? + // (Actually any integer type is allowed.) + const PointerType *PT = FTP->getParamType(0)->getAs<PointerType>(); + if (!PT) + return; + + if (! PT->getPointeeType()->isIntegralOrUnscopedEnumerationType()) + return; + } else if (FTP->getNumParams() != 0) + return; + + // Issue a warning. + SmallString<256> buf1; + llvm::raw_svector_ostream os1(buf1); + os1 << '\'' << *FD << "' is a poor random number generator"; + + SmallString<256> buf2; + llvm::raw_svector_ostream os2(buf2); + os2 << "Function '" << *FD + << "' is obsolete because it implements a poor random number generator." + << " Use 'arc4random' instead"; + + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_rand, os1.str(), + "Security", os2.str(), CELoc, + CE->getCallee()->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Check: 'random' should not be used +// Originally: <rdar://problem/63371000> +//===----------------------------------------------------------------------===// + +void WalkAST::checkCall_random(const CallExpr *CE, const FunctionDecl *FD) { + if (!CheckRand || !filter.check_rand) + return; + + const FunctionProtoType *FTP = FD->getType()->getAs<FunctionProtoType>(); + if (!FTP) + return; + + // Verify that the function takes no argument. + if (FTP->getNumParams() != 0) + return; + + // Issue a warning. + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_rand, + "'random' is not a secure random number generator", + "Security", + "The 'random' function produces a sequence of values that " + "an adversary may be able to predict. Use 'arc4random' " + "instead", CELoc, CE->getCallee()->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Check: 'vfork' should not be used. +// POS33-C: Do not use vfork(). +//===----------------------------------------------------------------------===// + +void WalkAST::checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD) { + if (!filter.check_vfork) + return; + + // All calls to vfork() are insecure, issue a warning. + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_vfork, + "Potential insecure implementation-specific behavior in " + "call 'vfork'", + "Security", + "Call to function 'vfork' is insecure as it can lead to " + "denial of service situations in the parent process. " + "Replace calls to vfork with calls to the safer " + "'posix_spawn' function", + CELoc, CE->getCallee()->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Check: '-decodeValueOfObjCType:at:' should not be used. +// It is deprecated in favor of '-decodeValueOfObjCType:at:size:' due to +// likelihood of buffer overflows. +//===----------------------------------------------------------------------===// + +void WalkAST::checkMsg_decodeValueOfObjCType(const ObjCMessageExpr *ME) { + if (!filter.check_decodeValueOfObjCType) + return; + + // Check availability of the secure alternative: + // iOS 11+, macOS 10.13+, tvOS 11+, and watchOS 4.0+ + // FIXME: We probably shouldn't register the check if it's not available. + const TargetInfo &TI = AC->getASTContext().getTargetInfo(); + const llvm::Triple &T = TI.getTriple(); + const VersionTuple &VT = TI.getPlatformMinVersion(); + switch (T.getOS()) { + case llvm::Triple::IOS: + if (VT < VersionTuple(11, 0)) + return; + break; + case llvm::Triple::MacOSX: + if (VT < VersionTuple(10, 13)) + return; + break; + case llvm::Triple::WatchOS: + if (VT < VersionTuple(4, 0)) + return; + break; + case llvm::Triple::TvOS: + if (VT < VersionTuple(11, 0)) + return; + break; + default: + return; + } + + PathDiagnosticLocation MELoc = + PathDiagnosticLocation::createBegin(ME, BR.getSourceManager(), AC); + BR.EmitBasicReport( + AC->getDecl(), filter.checkName_decodeValueOfObjCType, + "Potential buffer overflow in '-decodeValueOfObjCType:at:'", "Security", + "Deprecated method '-decodeValueOfObjCType:at:' is insecure " + "as it can lead to potential buffer overflows. Use the safer " + "'-decodeValueOfObjCType:at:size:' method.", + MELoc, ME->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// Check: Should check whether privileges are dropped successfully. +// Originally: <rdar://problem/6337132> +//===----------------------------------------------------------------------===// + +void WalkAST::checkUncheckedReturnValue(CallExpr *CE) { + if (!filter.check_UncheckedReturn) + return; + + const FunctionDecl *FD = CE->getDirectCallee(); + if (!FD) + return; + + if (II_setid[0] == nullptr) { + static const char * const identifiers[num_setids] = { + "setuid", "setgid", "seteuid", "setegid", + "setreuid", "setregid" + }; + + for (size_t i = 0; i < num_setids; i++) + II_setid[i] = &BR.getContext().Idents.get(identifiers[i]); + } + + const IdentifierInfo *id = FD->getIdentifier(); + size_t identifierid; + + for (identifierid = 0; identifierid < num_setids; identifierid++) + if (id == II_setid[identifierid]) + break; + + if (identifierid >= num_setids) + return; + + const FunctionProtoType *FTP = FD->getType()->getAs<FunctionProtoType>(); + if (!FTP) + return; + + // Verify that the function takes one or two arguments (depending on + // the function). + if (FTP->getNumParams() != (identifierid < 4 ? 1 : 2)) + return; + + // The arguments must be integers. + for (unsigned i = 0; i < FTP->getNumParams(); i++) + if (!FTP->getParamType(i)->isIntegralOrUnscopedEnumerationType()) + return; + + // Issue a warning. + SmallString<256> buf1; + llvm::raw_svector_ostream os1(buf1); + os1 << "Return value is not checked in call to '" << *FD << '\''; + + SmallString<256> buf2; + llvm::raw_svector_ostream os2(buf2); + os2 << "The return value from the call to '" << *FD + << "' is not checked. If an error occurs in '" << *FD + << "', the following code may execute with unexpected privileges"; + + PathDiagnosticLocation CELoc = + PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC); + BR.EmitBasicReport(AC->getDecl(), filter.checkName_UncheckedReturn, os1.str(), + "Security", os2.str(), CELoc, + CE->getCallee()->getSourceRange()); +} + +//===----------------------------------------------------------------------===// +// SecuritySyntaxChecker +//===----------------------------------------------------------------------===// + +namespace { +class SecuritySyntaxChecker : public Checker<check::ASTCodeBody> { +public: + ChecksFilter filter; + + void checkASTCodeBody(const Decl *D, AnalysisManager& mgr, + BugReporter &BR) const { + WalkAST walker(BR, mgr.getAnalysisDeclContext(D), filter); + walker.Visit(D->getBody()); + } +}; +} + +void ento::registerSecuritySyntaxChecker(CheckerManager &mgr) { + mgr.registerChecker<SecuritySyntaxChecker>(); +} + +bool ento::shouldRegisterSecuritySyntaxChecker(const LangOptions &LO) { + return true; +} + +#define REGISTER_CHECKER(name) \ + void ento::register##name(CheckerManager &mgr) { \ + SecuritySyntaxChecker *checker = mgr.getChecker<SecuritySyntaxChecker>(); \ + checker->filter.check_##name = true; \ + checker->filter.checkName_##name = mgr.getCurrentCheckerName(); \ + } \ + \ + bool ento::shouldRegister##name(const LangOptions &LO) { return true; } + +REGISTER_CHECKER(bcmp) +REGISTER_CHECKER(bcopy) +REGISTER_CHECKER(bzero) +REGISTER_CHECKER(gets) +REGISTER_CHECKER(getpw) +REGISTER_CHECKER(mkstemp) +REGISTER_CHECKER(mktemp) +REGISTER_CHECKER(strcpy) +REGISTER_CHECKER(rand) +REGISTER_CHECKER(vfork) +REGISTER_CHECKER(FloatLoopCounter) +REGISTER_CHECKER(UncheckedReturn) +REGISTER_CHECKER(DeprecatedOrUnsafeBufferHandling) +REGISTER_CHECKER(decodeValueOfObjCType) |