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//==- CheckSecuritySyntaxOnly.cpp - Basic security checks --------*- C++ -*-==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a set of flow-insensitive security checks.
//
//===----------------------------------------------------------------------===//
#include "clang/Analysis/PathSensitive/BugReporter.h"
#include "clang/Analysis/LocalCheckers.h"
#include "clang/AST/StmtVisitor.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/raw_ostream.h"
using namespace clang;
namespace {
class VISIBILITY_HIDDEN WalkAST : public StmtVisitor<WalkAST> {
BugReporter &BR;
public:
WalkAST(BugReporter &br) : BR(br) {}
// Statement visitor methods.
void VisitForStmt(ForStmt *S);
void VisitStmt(Stmt *S) { VisitChildren(S); }
void VisitChildren(Stmt *S);
// Checker-specific methods.
void CheckLoopConditionForFloat(const ForStmt *FS);
};
} // end anonymous namespace
//===----------------------------------------------------------------------===//
// AST walking.
//===----------------------------------------------------------------------===//
void WalkAST::VisitChildren(Stmt *S) {
for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
if (Stmt *child = *I)
Visit(child);
}
void WalkAST::VisitForStmt(ForStmt *FS) {
CheckLoopConditionForFloat(FS);
// Recurse and check children.
VisitChildren(FS);
}
//===----------------------------------------------------------------------===//
// Check: floating poing variable used as loop counter.
// Originally: <rdar://problem/6336718>
// Implements: CERT security coding advisory FLP-30.
//===----------------------------------------------------------------------===//
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() == BinaryOperator::Comma))
return NULL;
if (const DeclRefExpr *lhs = GetIncrementedVar(B->getLHS(), x, y))
return lhs;
if (const DeclRefExpr *rhs = GetIncrementedVar(B->getRHS(), x, y))
return rhs;
return NULL;
}
if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(expr)) {
const NamedDecl *ND = DR->getDecl();
return ND == x || ND == y ? DR : NULL;
}
if (const UnaryOperator *U = dyn_cast<UnaryOperator>(expr))
return U->isIncrementDecrementOp()
? GetIncrementedVar(U->getSubExpr(), x, y) : NULL;
return NULL;
}
/// 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) {
// 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;
// The actual error condition.
if (!((B->isRelationalOp() || B->isEqualityOp()) &&
((B->getLHS()->getType()->isFloatingType() ||
B->getRHS()->getType()->isFloatingType()))))
return;
// Are we comparing variables?
const DeclRefExpr *drLHS = dyn_cast<DeclRefExpr>(B->getLHS()->IgnoreParens());
const DeclRefExpr *drRHS = dyn_cast<DeclRefExpr>(B->getRHS()->IgnoreParens());
if (!drLHS && !drRHS)
return;
const VarDecl *vdLHS = drLHS ? dyn_cast<VarDecl>(drLHS->getDecl()) : NULL;
const VarDecl *vdRHS = drRHS ? dyn_cast<VarDecl>(drRHS->getDecl()) : NULL;
if (!vdLHS && !vdRHS)
return;
// Does either variable appear in increment?
const DeclRefExpr *drInc = GetIncrementedVar(increment, vdLHS, vdRHS);
if (!drInc)
return;
// Emit the error. First figure out which DeclRefExpr in the condition
// referenced the compared variable.
const DeclRefExpr *drCond = vdLHS == drInc->getDecl() ? drLHS : drRHS;
llvm::SmallVector<SourceRange, 2> ranges;
std::string sbuf;
llvm::raw_string_ostream os(sbuf);
os << "Variable '" << drCond->getDecl()->getNameAsCString()
<< "' 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";
BR.EmitBasicReport(bugType, "Security", os.str().c_str(),
FS->getLocStart(), ranges.data(), ranges.size());
}
//===----------------------------------------------------------------------===//
// Entry point for check.
//===----------------------------------------------------------------------===//
void clang::CheckSecuritySyntaxOnly(Decl *D, BugReporter &BR) {
WalkAST walker(BR);
walker.Visit(D->getBody());
}
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