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llvm-project/clang/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp

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//==- 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)
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