cppcheck/lib/checkbufferoverrun.cpp

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/*
* Cppcheck - A tool for static C/C++ code analysis
2014-02-15 07:45:39 +01:00
* Copyright (C) 2007-2014 Daniel Marjamäki and Cppcheck team.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
//---------------------------------------------------------------------------
// Buffer overrun..
//---------------------------------------------------------------------------
#include "checkbufferoverrun.h"
#include "tokenize.h"
#include "mathlib.h"
#include "symboldatabase.h"
#include <algorithm>
#include <sstream>
#include <list>
#include <cassert> // <- assert
#include <cstdlib>
//---------------------------------------------------------------------------
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// Register this check class (by creating a static instance of it)
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namespace {
CheckBufferOverrun instance;
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}
//---------------------------------------------------------------------------
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static void makeArrayIndexOutOfBoundsError(std::ostream& oss, const CheckBufferOverrun::ArrayInfo &arrayInfo, const std::vector<MathLib::bigint> &index)
{
oss << "Array '" << arrayInfo.varname();
for (std::size_t i = 0; i < arrayInfo.num().size(); ++i)
oss << "[" << arrayInfo.num(i) << "]";
if (index.size() == 1)
oss << "' accessed at index " << index[0] << ", which is";
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else {
oss << "' index " << arrayInfo.varname();
for (std::size_t i = 0; i < index.size(); ++i)
oss << "[" << index[i] << "]";
}
oss << " out of bounds.";
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}
void CheckBufferOverrun::arrayIndexOutOfBoundsError(const Token *tok, const ArrayInfo &arrayInfo, const std::vector<MathLib::bigint> &index)
{
std::ostringstream oss;
makeArrayIndexOutOfBoundsError(oss, arrayInfo, index);
reportError(tok, Severity::error, "arrayIndexOutOfBounds", oss.str());
}
void CheckBufferOverrun::arrayIndexOutOfBoundsError(const Token *tok, const ArrayInfo &arrayInfo, const std::vector<ValueFlow::Value> &index)
{
std::ostringstream errmsg;
errmsg << "Array '" << arrayInfo.varname();
for (std::size_t i = 0; i < arrayInfo.num().size(); ++i)
errmsg << "[" << arrayInfo.num(i) << "]";
if (index.size() == 1)
errmsg << "' accessed at index " << index[0].intvalue << ", which is out of bounds.";
else {
errmsg << "' index " << arrayInfo.varname();
for (std::size_t i = 0; i < index.size(); ++i)
errmsg << "[" << index[i].intvalue << "]";
errmsg << " out of bounds.";
}
const Token *condition = nullptr;
for (std::size_t i = 0; i < index.size(); ++i) {
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if (condition == nullptr)
condition = index[i].condition;
}
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if (condition != nullptr) {
errmsg << " Otherwise condition '" << condition->expressionString() << "' is redundant.";
std::list<const Token *> callstack;
callstack.push_back(tok);
callstack.push_back(condition);
reportError(callstack, Severity::warning, "arrayIndexOutOfBoundsCond", errmsg.str());
} else {
reportError(tok, Severity::error, "arrayIndexOutOfBounds", errmsg.str());
}
}
void CheckBufferOverrun::arrayIndexOutOfBoundsError(const std::list<const Token *> &callstack, const ArrayInfo &arrayInfo, const std::vector<MathLib::bigint> &index)
{
std::ostringstream oss;
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makeArrayIndexOutOfBoundsError(oss, arrayInfo, index);
reportError(callstack, Severity::error, "arrayIndexOutOfBounds", oss.str());
}
static std::string bufferOverrunMessage(std::string varnames)
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{
varnames.erase(std::remove(varnames.begin(), varnames.end(), ' '), varnames.end());
std::string errmsg("Buffer is accessed out of bounds");
if (!varnames.empty())
errmsg += ": " + varnames;
else
errmsg += ".";
return errmsg;
}
void CheckBufferOverrun::bufferOverrunError(const Token *tok, const std::string &varnames)
{
reportError(tok, Severity::error, "bufferAccessOutOfBounds", bufferOverrunMessage(varnames));
}
void CheckBufferOverrun::bufferOverrunError(const std::list<const Token *> &callstack, const std::string &varnames)
{
reportError(callstack, Severity::error, "bufferAccessOutOfBounds", bufferOverrunMessage(varnames));
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}
void CheckBufferOverrun::possibleBufferOverrunError(const Token *tok, const std::string &src, const std::string &dst, bool cat)
{
if (cat)
reportError(tok, Severity::warning, "possibleBufferAccessOutOfBounds",
"Possible buffer overflow if strlen(" + src + ") is larger than sizeof(" + dst + ")-strlen(" + dst +").\n"
"Possible buffer overflow if strlen(" + src + ") is larger than sizeof(" + dst + ")-strlen(" + dst +"). "
"The source buffer is larger than the destination buffer so there is the potential for overflowing the destination buffer.");
else
reportError(tok, Severity::warning, "possibleBufferAccessOutOfBounds",
"Possible buffer overflow if strlen(" + src + ") is larger than or equal to sizeof(" + dst + ").\n"
"Possible buffer overflow if strlen(" + src + ") is larger than or equal to sizeof(" + dst + "). "
"The source buffer is larger than the destination buffer so there is the potential for overflowing the destination buffer.");
}
void CheckBufferOverrun::possibleReadlinkBufferOverrunError(const Token* tok, const std::string &funcname, const std::string &varname)
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{
const std::string errmsg = funcname + "() might return the full size of '" + varname + "'. Lower the supplied size by one.\n" +
funcname + "() might return the full size of '" + varname + "'. "
"If a " + varname + "[len] = '\\0'; statement follows, it will overrun the buffer. Lower the supplied size by one.";
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reportError(tok, Severity::warning, "possibleReadlinkBufferOverrun", errmsg, true);
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}
void CheckBufferOverrun::strncatUsageError(const Token *tok)
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{
if (_settings && !_settings->isEnabled("warning"))
return;
reportError(tok, Severity::warning, "strncatUsage",
"Dangerous usage of strncat - 3rd parameter is the maximum number of characters to append.\n"
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"At most, strncat appends the 3rd parameter's amount of characters and adds a terminating null byte.\n"
"The safe way to use strncat is to subtract one from the remaining space in the buffer and use it as 3rd parameter."
"Source: http://www.cplusplus.com/reference/cstring/strncat/\n"
"Source: http://www.opensource.apple.com/source/Libc/Libc-167/gen.subproj/i386.subproj/strncat.c");
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}
void CheckBufferOverrun::outOfBoundsError(const Token *tok, const std::string &what, const bool show_size_info, const MathLib::bigint &supplied_size, const MathLib::bigint &actual_size)
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{
std::ostringstream oss;
oss << what << " is out of bounds";
if (show_size_info)
oss << ": Supplied size " << supplied_size << " is larger than actual size " << actual_size;
oss << '.';
reportError(tok, Severity::error, "outOfBounds", oss.str());
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}
void CheckBufferOverrun::pointerOutOfBoundsError(const Token *tok, const std::string &object)
{
reportError(tok, Severity::portability, "pointerOutOfBounds", "Undefined behaviour: Pointer arithmetic result does not point into or just past the end of the " + object + ".\n"
"Undefined behaviour: The result of this pointer arithmetic does not point into or just one element past the end of the " + object + ". Further information: https://www.securecoding.cert.org/confluence/display/seccode/ARR30-C.+Do+not+form+or+use+out+of+bounds+pointers+or+array+subscripts");
}
void CheckBufferOverrun::sizeArgumentAsCharError(const Token *tok)
{
if (_settings && !_settings->isEnabled("warning"))
return;
reportError(tok, Severity::warning, "sizeArgumentAsChar", "The size argument is given as a char constant.");
}
void CheckBufferOverrun::terminateStrncpyError(const Token *tok, const std::string &varname)
{
reportError(tok, Severity::warning, "terminateStrncpy",
"The buffer '" + varname + "' may not be null-terminated after the call to strncpy().\n"
"If the source string's size fits or exceeds the given size, strncpy() does not add a "
"zero at the end of the buffer. This causes bugs later in the code if the code "
"assumes buffer is null-terminated.", true);
}
void CheckBufferOverrun::cmdLineArgsError(const Token *tok)
{
reportError(tok, Severity::error, "insecureCmdLineArgs", "Buffer overrun possible for long command line arguments.");
}
void CheckBufferOverrun::bufferNotZeroTerminatedError(const Token *tok, const std::string &varname, const std::string &function)
{
const std::string errmsg = "The buffer '" + varname + "' is not null-terminated after the call to " + function + "().\n"
"The buffer '" + varname + "' is not null-terminated after the call to " + function + "(). "
"This will cause bugs later in the code if the code assumes the buffer is null-terminated.";
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reportError(tok, Severity::warning, "bufferNotZeroTerminated", errmsg, true);
}
void CheckBufferOverrun::argumentSizeError(const Token *tok, const std::string &functionName, const std::string &varname)
{
reportError(tok, Severity::warning, "argumentSize", "The array '" + varname + "' is too small, the function '" + functionName + "' expects a bigger one.");
}
void CheckBufferOverrun::negativeMemoryAllocationSizeError(const Token *tok)
{
reportError(tok, Severity::error, "negativeMemoryAllocationSize",
"Memory allocation size is negative.\n"
"Memory allocation size is negative."
"Negative allocation size has no specified behaviour.");
}
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// Check array usage..
//---------------------------------------------------------------------------
/**
* bailout if variable is used inside if/else/switch block or if there is "break"
* @param tok token for "if" or "switch"
* @param varid variable id
* @return is bailout recommended?
*/
static bool bailoutIfSwitch(const Token *tok, const unsigned int varid)
{
const Token* end = tok->linkAt(1)->linkAt(1);
if (Token::simpleMatch(end, "} else {")) // scan the else-block
end = end->linkAt(2);
if (Token::simpleMatch(end, "{")) // Ticket #5203: Invalid code, bailout
return true;
// Used later to check if the body belongs to a "if"
const bool is_if = tok->str() == "if";
for (; tok && tok != end; tok = tok->next()) {
// If scanning a "if" block then bailout for "break"
if (is_if && (tok->str() == "break" || tok->str() == "continue"))
return true;
// bailout for "return"
else if (tok->str() == "return")
return true;
// bailout if varid is found
else if (tok->varId() == varid)
return true;
}
// No bailout stuff found => return false
return false;
}
//---------------------------------------------------------------------------
static bool checkMinSizes(const std::list<Library::ArgumentChecks::MinSize> &minsizes, const Token * const ftok, const std::size_t arraySize, const Token **charSizeToken)
{
if (charSizeToken)
*charSizeToken = nullptr;
if (minsizes.empty())
return false;
// All conditions must be true
bool error = true;
for (std::list<Library::ArgumentChecks::MinSize>::const_iterator minsize = minsizes.begin(); minsize != minsizes.end(); ++minsize) {
if (!error)
return false;
error = false;
const Token *argtok = ftok->tokAt(2);
for (int argnum = 1; argtok && argnum < minsize->arg; argnum++)
argtok = argtok->nextArgument();
if (!argtok)
return false;
switch (minsize->type) {
case Library::ArgumentChecks::MinSize::ARGVALUE:
if (Token::Match(argtok, "%num% ,|)")) {
const MathLib::bigint sz = MathLib::toLongNumber(argtok->str());
if ((std::size_t)sz > arraySize)
error = true;
} else if (argtok->type() == Token::eChar && Token::Match(argtok->next(), ",|)") && charSizeToken)
*charSizeToken = argtok; //sizeArgumentAsCharError(argtok);
break;
case Library::ArgumentChecks::MinSize::MUL:
// TODO: handle arbitrary arg2
if (minsize->arg2 == minsize->arg+1 && Token::Match(argtok, "%num% , %num% ,|)")) {
const MathLib::bigint sz = MathLib::toLongNumber(argtok->str()) * MathLib::toLongNumber(argtok->strAt(2));
if ((std::size_t)sz > arraySize)
error = true;
}
break;
case Library::ArgumentChecks::MinSize::STRLEN: {
const Token *strtoken = argtok->getValueTokenMaxStrLength();
if (strtoken && Token::getStrLength(strtoken) >= arraySize)
error = true;
}
break;
case Library::ArgumentChecks::MinSize::SIZEOF:
if (argtok->type() == Token::eString && Token::getStrLength(argtok) >= arraySize)
error = true;
break;
case Library::ArgumentChecks::MinSize::NONE:
return false;
};
}
return error;
}
void CheckBufferOverrun::checkFunctionParameter(const Token &ftok, unsigned int par, const ArrayInfo &arrayInfo, const std::list<const Token *>& callstack)
{
const std::list<Library::ArgumentChecks::MinSize> * const minsizes = _settings->library.argminsizes(ftok.str(),par);
if (minsizes && (!(Token::simpleMatch(ftok.previous(), ".") || Token::Match(ftok.tokAt(-2), "!!std ::")))) {
if (arrayInfo.element_size() == 0)
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return;
MathLib::bigint arraySize = arrayInfo.element_size();
for (std::size_t i = 0; i < arrayInfo.num().size(); ++i)
arraySize *= arrayInfo.num(i);
const Token *charSizeToken = nullptr;
if (checkMinSizes(*minsizes, &ftok, (std::size_t)arraySize, &charSizeToken))
bufferOverrunError(callstack, arrayInfo.varname());
if (charSizeToken)
sizeArgumentAsCharError(charSizeToken);
}
// Calling a user function?
// only 1-dimensional arrays can be checked currently
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else if (arrayInfo.num().size() == 1) {
const Function* const func = ftok.function();
if (func && func->hasBody) {
// Get corresponding parameter..
const Variable* const parameter = func->getArgumentVar(par-1);
// Ensure that it has a compatible size..
if (!parameter || _tokenizer->sizeOfType(parameter->typeStartToken()) != arrayInfo.element_size())
return;
// No variable id occur for instance when:
// - Variable function arguments: "void f(...)"
// - Unnamed parameter: "void f(char *)"
if (parameter->declarationId() == 0)
return;
// Check the parameter usage in the function scope..
for (const Token* ftok2 = func->functionScope->classStart; ftok2 != func->functionScope->classEnd; ftok2 = ftok2->next()) {
if (Token::Match(ftok2, "if|for|switch|while (")) {
// bailout if there is buffer usage..
if (bailoutIfSwitch(ftok2, parameter->declarationId())) {
break;
}
// no bailout is needed. skip the if-block
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else {
// goto end of if block..
ftok2 = ftok2->linkAt(1)->linkAt(1);
if (Token::simpleMatch(ftok2, "} else {"))
ftok2 = ftok2->linkAt(2);
if (!ftok2)
break;
continue;
}
}
if (ftok2->str() == "}")
break;
if (ftok2->varId() == parameter->declarationId()) {
if (Token::Match(ftok2->previous(), "-- %var%") ||
Token::Match(ftok2, "%var% --"))
break;
if (Token::Match(ftok2->previous(), ";|{|}|%op% %var% [ %num% ]")) {
const MathLib::bigint index = MathLib::toLongNumber(ftok2->strAt(2));
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if (index >= 0 && arrayInfo.num(0) > 0 && index >= arrayInfo.num(0)) {
std::list<const Token *> callstack2(callstack);
callstack2.push_back(ftok2);
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std::vector<MathLib::bigint> indexes;
indexes.push_back(index);
arrayIndexOutOfBoundsError(callstack2, arrayInfo, indexes);
}
}
}
// Calling function..
if (Token::Match(ftok2, "%var% (")) {
ArrayInfo ai(arrayInfo);
ai.declarationId(parameter->declarationId());
checkFunctionCall(ftok2, ai, callstack);
}
}
}
}
// Check 'float x[10]' arguments in declaration
if (_settings->isEnabled("warning")) {
const Function* const func = ftok.function();
// If argument is '%type% a[num]' then check bounds against num
if (func) {
const Variable* const argument = func->getArgumentVar(par-1);
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const Token *nameToken;
if (argument && Token::Match(argument->typeStartToken(), "%type% %var% [ %num% ] [,)[]")
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&& (nameToken = argument->nameToken()) != nullptr) {
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const Token *tok2 = nameToken->next();
MathLib::bigint argsize = _tokenizer->sizeOfType(argument->typeStartToken());
if (argsize == 100) // unknown size
argsize = 0;
while (Token::Match(tok2, "[ %num% ] [,)[]")) {
argsize *= MathLib::toLongNumber(tok2->strAt(1));
tok2 = tok2->tokAt(3);
}
MathLib::bigint arraysize = arrayInfo.element_size();
if (arraysize == 100) // unknown size
arraysize = 0;
for (std::size_t i = 0; i < arrayInfo.num().size(); i++)
arraysize *= arrayInfo.num(i);
if (Token::Match(tok2, "[,)]") && arraysize > 0 && argsize > arraysize)
argumentSizeError(&ftok, ftok.str(), arrayInfo.varname());
}
}
}
}
void CheckBufferOverrun::checkFunctionCall(const Token *tok, const ArrayInfo &arrayInfo, std::list<const Token *> callstack)
{
// Don't go deeper than 2 levels, the checking can get very slow
// when there is no limit
if (callstack.size() >= 2)
return;
// Prevent recursion
for (std::list<const Token*>::const_iterator it = callstack.begin(); it != callstack.end(); ++it) {
// Same function name => bail out
if (tok->str() == (*it)->str())
return;
}
callstack.push_back(tok);
const unsigned int declarationId = arrayInfo.declarationId();
const Token *tok2 = tok->tokAt(2);
// 1st parameter..
if (Token::Match(tok2, "%varid% ,|)", declarationId))
checkFunctionParameter(*tok, 1, arrayInfo, callstack);
else if (Token::Match(tok2, "%varid% + %num% ,|)", declarationId)) {
const ArrayInfo ai(arrayInfo.limit(MathLib::toLongNumber(tok2->strAt(2))));
checkFunctionParameter(*tok, 1, ai, callstack);
}
// goto 2nd parameter and check it..
tok2 = tok2->nextArgument();
if (Token::Match(tok2, "%varid% ,|)", declarationId))
checkFunctionParameter(*tok, 2, arrayInfo, callstack);
else if (Token::Match(tok2, "%varid% + %num% ,|)", declarationId)) {
const ArrayInfo ai(arrayInfo.limit(MathLib::toLongNumber(tok2->strAt(2))));
checkFunctionParameter(*tok, 2, ai, callstack);
}
}
void CheckBufferOverrun::checkScope(const Token *tok, const std::vector<std::string> &varname, const ArrayInfo &arrayInfo)
{
const MathLib::bigint size = arrayInfo.num(0);
if (size == 0) // unknown size
return;
if (tok->str() == "return") {
tok = tok->next();
if (!tok)
return;
}
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const MathLib::bigint total_size = arrayInfo.element_size() * size;
const unsigned int declarationId = arrayInfo.declarationId();
std::string varnames;
for (std::size_t i = 0; i < varname.size(); ++i)
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varnames += (i == 0 ? "" : " . ") + varname[i];
const unsigned char varcount = static_cast<unsigned char>(varname.empty() ? 0U : (varname.size() - 1) * 2U);
// ValueFlow array index..
if ((declarationId > 0 && Token::Match(tok, "%varid% [", declarationId)) ||
(declarationId == 0 && Token::Match(tok, (varnames + " [").c_str()))) {
const Token *tok2 = tok;
while (tok2->str() != "[")
tok2 = tok2->next();
valueFlowCheckArrayIndex(tok2, arrayInfo);
}
// If the result of pointer arithmetic means that the pointer is
// out of bounds then this flag will be set.
bool pointerIsOutOfBounds = false;
const bool isPortabilityEnabled = _settings->isEnabled("portability");
for (const Token* const end = tok->scope()->classEnd; tok != end; tok = tok->next()) {
if (declarationId != 0 && Token::Match(tok, "%varid% = new|malloc|realloc", declarationId)) {
// Abort
break;
}
// reassign buffer
if (declarationId > 0 && Token::Match(tok, "[;{}] %varid% = %any%", declarationId)) {
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// using varid .. bailout
if (tok->tokAt(3)->varId() != declarationId)
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break;
pointerIsOutOfBounds = false;
}
// Array index..
if ((declarationId > 0 && ((tok->str() == "return" || (!tok->isName() && !Token::Match(tok, "[.&]"))) && Token::Match(tok->next(), "%varid% [ %num% ]", declarationId))) ||
(declarationId == 0 && ((tok->str() == "return" || (!tok->isName() && !Token::Match(tok, "[.&]"))) && (Token::Match(tok->next(), (varnames + " [ %num% ]").c_str()) || Token::Match(tok->next(), (varname[0] +" [ %num% ] . " + varname[1] + " [ %num% ]").c_str()))))) {
std::vector<MathLib::bigint> indexes;
const Token *tok2 = tok->tokAt(2 + varcount);
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for (; Token::Match(tok2, "[ %num% ]"); tok2 = tok2->tokAt(3)) {
const MathLib::bigint index = MathLib::toLongNumber(tok2->strAt(1));
indexes.push_back(index);
}
for (; Token::Match(tok2->tokAt(3), "[ %num% ]"); tok2 = tok2->tokAt(3)) {
const MathLib::bigint index = MathLib::toLongNumber(tok2->strAt(4));
indexes.push_back(index);
}
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if (indexes.size() == arrayInfo.num().size()) {
// Check if the indexes point outside the whole array..
// char a[10][10];
// a[0][20] <-- ok.
// a[9][20] <-- error.
// total number of elements of array..
MathLib::bigint totalElements = 1;
// total index..
MathLib::bigint totalIndex = 0;
// calculate the totalElements and totalIndex..
for (std::size_t i = 0; i < indexes.size(); ++i) {
const std::size_t ri = indexes.size() - 1 - i;
totalIndex += indexes[ri] * totalElements;
totalElements *= arrayInfo.num(ri);
}
// totalElements == 0 => Unknown size
if (totalElements == 0)
continue;
const Token *tok3 = tok->previous();
while (tok3 && Token::Match(tok3->previous(), "%var% ."))
tok3 = tok3->tokAt(-2);
// taking address of 1 past end?
if (totalIndex == totalElements) {
const bool addr = (tok3 && (tok3->str() == "&" ||
Token::simpleMatch(tok3->previous(), "& (")));
if (addr)
continue;
}
// Is totalIndex in bounds?
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if (totalIndex > totalElements || totalIndex < 0) {
arrayIndexOutOfBoundsError(tok->tokAt(1 + varcount), arrayInfo, indexes);
}
// Is any array index out of bounds?
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else {
// check each index for overflow
for (std::size_t i = 0; i < indexes.size(); ++i) {
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if (indexes[i] >= arrayInfo.num(i)) {
if (indexes.size() == 1U) {
arrayIndexOutOfBoundsError(tok->tokAt(1 + varcount), arrayInfo, indexes);
break; // only warn about the first one
}
// The access is still within the memory range for the array
// so it may be intentional.
else if (_settings->inconclusive) {
arrayIndexOutOfBoundsError(tok->tokAt(1 + varcount), arrayInfo, indexes);
break; // only warn about the first one
}
}
}
}
}
tok = tok2;
continue;
}
// memset, memcmp, memcpy, strncpy, fgets..
if (declarationId == 0 && size > 0) {
std::list<const Token *> callstack;
callstack.push_back(tok);
if (Token::Match(tok, ("%var% ( " + varnames + " ,").c_str()))
checkFunctionParameter(*tok, 1, arrayInfo, callstack);
if (Token::Match(tok, ("%var% ( %var% , " + varnames + " ,").c_str()))
checkFunctionParameter(*tok, 2, arrayInfo, callstack);
}
// Writing data into array..
if ((declarationId > 0 && Token::Match(tok, "strcpy|strcat ( %varid% , %str% )", declarationId)) ||
(declarationId == 0 && Token::Match(tok, ("strcpy|strcat ( " + varnames + " , %str% )").c_str()))) {
const std::size_t len = Token::getStrLength(tok->tokAt(varcount + 4));
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if (total_size > 0 && len >= (unsigned int)total_size) {
bufferOverrunError(tok, declarationId > 0 ? emptyString : varnames);
continue;
}
} else if ((declarationId > 0 && Token::Match(tok, "strcpy|strcat ( %varid% , %var% )", declarationId)) ||
(declarationId == 0 && Token::Match(tok, ("strcpy|strcat ( " + varnames + " , %var% )").c_str()))) {
const Variable *var = tok->tokAt(4)->variable();
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if (var && var->isArray() && var->dimensions().size() == 1) {
const std::size_t len = (std::size_t)var->dimension(0);
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if (total_size > 0 && len > (unsigned int)total_size) {
if (_settings->inconclusive)
possibleBufferOverrunError(tok, tok->strAt(4), tok->strAt(2), tok->str() == "strcat");
continue;
}
}
}
// Detect few strcat() calls
const std::string strcatPattern = declarationId > 0 ? std::string("strcat ( %varid% , %str% ) ;") : ("strcat ( " + varnames + " , %str% ) ;");
if (Token::Match(tok, strcatPattern.c_str(), declarationId)) {
std::size_t charactersAppend = 0;
const Token *tok2 = tok;
while (Token::Match(tok2, strcatPattern.c_str(), declarationId)) {
charactersAppend += Token::getStrLength(tok2->tokAt(4 + varcount));
if (charactersAppend >= static_cast<std::size_t>(total_size)) {
bufferOverrunError(tok2);
break;
}
tok2 = tok2->tokAt(7 + varcount);
}
}
// sprintf..
// TODO: change total_size to an unsigned value and remove the "&& total_size > 0" check.
const std::string sprintfPattern = declarationId > 0 ? std::string("sprintf ( %varid% , %str% [,)]") : ("sprintf ( " + varnames + " , %str% [,)]");
if (Token::Match(tok, sprintfPattern.c_str(), declarationId) && total_size > 0) {
checkSprintfCall(tok, static_cast<unsigned int>(total_size));
}
// snprintf..
const std::string snprintfPattern = declarationId > 0 ? std::string("snprintf ( %varid% , %num% ,") : ("snprintf ( " + varnames + " , %num% ,");
if (Token::Match(tok, snprintfPattern.c_str(), declarationId)) {
const MathLib::bigint n = MathLib::toLongNumber(tok->strAt(4 + varcount));
if (n > total_size)
outOfBoundsError(tok->tokAt(4 + varcount), "snprintf size", true, n, total_size);
}
// Check function call..
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if (Token::Match(tok, "%var% (") && total_size > 0) {
// No varid => function calls are not handled
if (declarationId == 0)
continue;
const ArrayInfo arrayInfo1(declarationId, varnames, total_size / size, size);
const std::list<const Token *> callstack;
checkFunctionCall(tok, arrayInfo1, callstack);
}
// undefined behaviour: result of pointer arithmetic is out of bounds
else if (declarationId && Token::Match(tok, "= %varid% + %num% ;", declarationId)) {
const MathLib::bigint index = MathLib::toLongNumber(tok->strAt(3));
if (isPortabilityEnabled && index > size)
pointerOutOfBoundsError(tok->next(), "buffer");
if (index >= size && Token::Match(tok->tokAt(-2), "[;{}] %varid% =", declarationId))
pointerIsOutOfBounds = true;
}
else if (pointerIsOutOfBounds && Token::Match(tok, "[;{}=] * %varid% [;=]", declarationId)) {
outOfBoundsError(tok->tokAt(2), tok->strAt(2), false, 0, 0);
}
}
}
void CheckBufferOverrun::valueFlowCheckArrayIndex(const Token * const tok, const ArrayInfo &arrayInfo)
{
// Declaration in global scope?
if (tok->scope()->type == Scope::eGlobal)
return;
/*
{
const Token *parent = tok->astParent();
while (Token::Match(parent, "%var%|::|*|&"))
parent = parent->astParent();
if (parent && !Token::simpleMatch(parent, "="))
return;
}
*/
// Taking address?
bool addressOf = false;
{
const Token *tok2 = tok->astParent();
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while (Token::Match(tok2, "%var%|.|::|["))
tok2 = tok2->astParent();
addressOf = tok2 && tok2->str() == "&" && !(tok2->astOperand1() && tok2->astOperand2());
}
// Look for errors first
for (int warn = 0; warn == 0 || warn == 1; ++warn) {
// Negative index..
for (const Token *tok2 = tok; tok2 && tok2->str() == "["; tok2 = tok2->link()->next()) {
const Token *index = tok2->astOperand2();
if (!index)
continue;
const ValueFlow::Value *value = index->getValueLE(-1LL,_settings);
if (value)
negativeIndexError(index, *value);
}
// Index out of bounds..
std::vector<ValueFlow::Value> indexes;
unsigned int valuevarid = 0;
for (const Token *tok2 = tok; indexes.size() < arrayInfo.num().size() && Token::Match(tok2, "["); tok2 = tok2->link()->next()) {
if (!tok2->astOperand2()) {
indexes.clear();
break;
}
const ValueFlow::Value *value = tok2->astOperand2()->getMaxValue(warn == 1);
if (!value) {
indexes.clear();
break;
}
if (valuevarid == 0U)
valuevarid = value->varId;
if (value->varId > 0 && valuevarid != value->varId) {
indexes.clear();
break;
}
if (value->intvalue < 0) {
indexes.clear();
break;
}
indexes.push_back(*value);
}
if (indexes.size() == arrayInfo.num().size()) {
// Check if the indexes point outside the whole array..
// char a[10][10];
// a[0][20] <-- ok.
// a[9][20] <-- error.
// total number of elements of array..
MathLib::bigint totalElements = 1;
// total index..
MathLib::bigint totalIndex = 0;
// calculate the totalElements and totalIndex..
for (std::size_t i = 0; i < indexes.size(); ++i) {
const std::size_t ri = indexes.size() - 1 - i;
totalIndex += indexes[ri].intvalue * totalElements;
totalElements *= arrayInfo.num(ri);
}
// totalElements <= 0 => Unknown size
if (totalElements <= 0)
continue;
// taking address of 1 past end?
if (addressOf && totalIndex == totalElements)
continue;
// Is totalIndex in bounds?
if (totalIndex >= totalElements) {
arrayIndexOutOfBoundsError(tok, arrayInfo, indexes);
break;
}
// Is any array index out of bounds?
else {
// check each index for overflow
for (std::size_t i = 0; i < indexes.size(); ++i) {
if (indexes[i].intvalue >= arrayInfo.num(i)) {
// The access is still within the memory range for the array
// so it may be intentional.
if (_settings->inconclusive) {
arrayIndexOutOfBoundsError(tok, arrayInfo, indexes);
break; // only warn about the first one
}
}
}
}
}
}
}
void CheckBufferOverrun::checkScope(const Token *tok, const ArrayInfo &arrayInfo)
{
const MathLib::bigint total_size = arrayInfo.num(0) * arrayInfo.element_size();
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const Token *scope_begin = tok->previous();
assert(scope_begin != 0);
const unsigned int declarationId = arrayInfo.declarationId();
const bool isPortabilityEnabled = _settings->isEnabled("portability");
const bool isWarningEnabled = _settings->isEnabled("warning");
for (const Token* const end = tok->scope()->classEnd; tok != end; tok = tok->next()) {
if (tok->varId() == declarationId) {
if (tok->strAt(1) == "[") {
valueFlowCheckArrayIndex(tok->next(), arrayInfo);
}
// undefined behaviour: result of pointer arithmetic is out of bounds
else if (isPortabilityEnabled && Token::Match(tok->previous(), "= %varid% + %num% ;", declarationId)) {
const MathLib::bigint index = MathLib::toLongNumber(tok->strAt(2));
if (index < 0 || index > arrayInfo.num(0)) {
pointerOutOfBoundsError(tok, "array");
}
}
}
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else if (!tok->scope()->isExecutable()) // No executable code outside of executable scope - continue to increase performance
continue;
else if (Token::Match(tok, "%var% (")) {
// Check function call..
checkFunctionCall(tok, arrayInfo, std::list<const Token*>());
if (_settings->inconclusive && Token::Match(tok, "strncpy|memcpy|memmove ( %varid% , %str% , %num% )", declarationId)) {
if (Token::getStrLength(tok->tokAt(4)) >= (unsigned int)total_size) {
const unsigned int num = (unsigned int)MathLib::toLongNumber(tok->strAt(6));
if ((unsigned int)total_size == num)
bufferNotZeroTerminatedError(tok, tok->strAt(2), tok->str());
}
}
if ((Token::Match(tok, "strncpy|strncat ( %varid% ,", declarationId) && Token::Match(tok->linkAt(1)->tokAt(-2), ", %num% )"))) {
const Token* param3 = tok->linkAt(1)->previous();
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// check for strncpy which is not terminated
if (tok->str() == "strncpy") {
// strncpy takes entire variable length as input size
unsigned int num = (unsigned int)MathLib::toLongNumber(param3->str());
// this is currently 'inconclusive'. See TestBufferOverrun::terminateStrncpy3
if (isWarningEnabled && num >= total_size && _settings->inconclusive) {
const Token *tok2 = tok->next()->link()->next();
for (; tok2; tok2 = tok2->next()) {
if (tok2->varId() == tok->tokAt(2)->varId()) {
if (!Token::Match(tok2, "%varid% [ %any% ] = 0 ;", tok->tokAt(2)->varId())) {
terminateStrncpyError(tok, tok->strAt(2));
}
break;
}
}
}
}
// Dangerous usage of strncat..
else if (tok->str() == "strncat") {
const MathLib::bigint n = MathLib::toLongNumber(param3->str());
if (n >= total_size)
strncatUsageError(tok);
}
// Dangerous usage of strncpy + strncat..
if (Token::Match(param3->tokAt(2), "; strncat ( %varid% ,", declarationId) && Token::Match(param3->linkAt(4)->tokAt(-2), ", %num% )")) {
const MathLib::bigint n = MathLib::toLongNumber(param3->str()) + MathLib::toLongNumber(param3->linkAt(4)->strAt(-1));
if (n > total_size)
strncatUsageError(param3->tokAt(3));
}
}
// Writing data into array..
if (Token::Match(tok, "strcpy|strcat ( %varid% , %str% )", declarationId)) {
const std::size_t len = Token::getStrLength(tok->tokAt(4));
if (total_size > 0 && len >= (unsigned int)total_size) {
bufferOverrunError(tok, arrayInfo.varname());
continue;
}
}
// Detect few strcat() calls
if (total_size > 0 && Token::Match(tok, "strcat ( %varid% , %str% ) ;", declarationId)) {
std::size_t charactersAppend = 0;
const Token *tok2 = tok;
while (tok2 && Token::Match(tok2, "strcat ( %varid% , %str% ) ;", declarationId)) {
charactersAppend += Token::getStrLength(tok2->tokAt(4));
if (charactersAppend >= (unsigned int)total_size) {
bufferOverrunError(tok2, arrayInfo.varname());
break;
}
tok2 = tok2->tokAt(7);
}
}
if (Token::Match(tok, "sprintf ( %varid% , %str% [,)]", declarationId)) {
checkSprintfCall(tok, total_size);
}
// snprintf..
if (total_size > 0 && Token::Match(tok, "snprintf ( %varid% , %num% ,", declarationId)) {
const MathLib::bigint n = MathLib::toLongNumber(tok->strAt(4));
if (n > total_size)
outOfBoundsError(tok->tokAt(4), "snprintf size", true, n, total_size);
}
// readlink() / readlinkat() buffer usage
if (_settings->standards.posix && Token::Match(tok, "readlink|readlinkat ("))
checkReadlinkBufferUsage(tok, scope_begin, declarationId, total_size);
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}
}
}
//---------------------------------------------------------------------------
// Checking member variables of structs..
//---------------------------------------------------------------------------
bool CheckBufferOverrun::isArrayOfStruct(const Token* tok, int &position)
{
if (Token::Match(tok->next(), "%var% [ %num% ] ")) {
tok = tok->tokAt(4);
int i = 1;
for (;;) {
if (Token::Match(tok->next(), "[ %num% ] ")) {
i++;
tok = tok->tokAt(4);
} else
break;
}
Use simple match where possible Fixes these warnings found by "--enable=internal": [lib/checkclass.cpp:972]: (warning) Found simple pattern inside Token::Match() call: "* *" [lib/checkbufferoverrun.cpp:635]: (warning) Found simple pattern inside Token::Match() call: "." [lib/checkbufferoverrun.cpp:1397]: (warning) Found simple pattern inside Token::Match() call: ";" [lib/checksizeof.cpp:299]: (warning) Found simple pattern inside Token::Match() call: "." [lib/checksizeof.cpp:301]: (warning) Found simple pattern inside Token::Match() call: ")" [lib/checksizeof.cpp:303]: (warning) Found simple pattern inside Token::Match() call: "]" [lib/checksizeof.cpp:318]: (warning) Found simple pattern inside Token::Match() call: ")" [lib/checknullpointer.cpp:413]: (warning) Found simple pattern inside Token::Match() call: "delete" [lib/checkio.cpp:1336]: (warning) Found simple pattern inside Token::Match() call: "> (" [lib/checkstl.cpp:1509]: (warning) Found simple pattern inside Token::findmatch() call: ";" [lib/checkstl.cpp:1512]: (warning) Found simple pattern inside Token::findmatch() call: ";" [lib/checkstl.cpp:1594]: (warning) Found simple pattern inside Token::Match() call: "=" [lib/checkstl.cpp:1598]: (warning) Found simple pattern inside Token::Match() call: "] =" [lib/checkunusedvar.cpp:755]: (warning) Found simple pattern inside Token::Match() call: "goto" [lib/checkunusedvar.cpp:793]: (warning) Found simple pattern inside Token::Match() call: "=" [lib/checkuninitvar.cpp:376]: (warning) Found simple pattern inside Token::Match() call: "> (" [lib/checkother.cpp:86]: (warning) Found simple pattern inside Token::Match() call: "> (" [lib/checkother.cpp:2181]: (warning) Found simple pattern inside Token::Match() call: "> {" [lib/valueflow.cpp:54]: (warning) Found simple pattern inside Token::Match() call: "&" [lib/valueflow.cpp:409]: (warning) Found simple pattern inside Token::Match() call: "do" [lib/valueflow.cpp:425]: (warning) Found simple pattern inside Token::Match() call: ") {" [lib/valueflow.cpp:487]: (warning) Found simple pattern inside Token::Match() call: ") {" [lib/valueflow.cpp:511]: (warning) Found simple pattern inside Token::Match() call: "} else {" [lib/valueflow.cpp:615]: (warning) Found simple pattern inside Token::Match() call: "for (" [lib/symboldatabase.cpp:80]: (warning) Found simple pattern inside Token::Match() call: "= {" [lib/symboldatabase.cpp:1069]: (warning) Found simple pattern inside Token::Match() call: "std ::" [lib/tokenize.cpp:2207]: (warning) Found simple pattern inside Token::Match() call: "< >" [lib/tokenize.cpp:2730]: (warning) Found simple pattern inside Token::Match() call: ";" [lib/tokenize.cpp:4234]: (warning) Found simple pattern inside Token::Match() call: "try {" [lib/tokenize.cpp:4235]: (warning) Found simple pattern inside Token::Match() call: "} catch (" [lib/tokenize.cpp:5500]: (warning) Found simple pattern inside Token::Match() call: "INT8" [lib/tokenize.cpp:5752]: (warning) Found simple pattern inside Token::Match() call: "}" [lib/tokenize.cpp:5752]: (warning) Found simple pattern inside Token::Match() call: "do"
2014-03-14 16:26:37 +01:00
if (Token::simpleMatch(tok->next(),";")) {
position = i;
return true;
}
}
return false;
}
void CheckBufferOverrun::checkReadlinkBufferUsage(const Token* ftok, const Token *scope_begin, const unsigned int varid, const MathLib::bigint total_size)
{
const std::string& funcname = ftok->str();
const Token* bufParam = ftok->tokAt(2)->nextArgument();
if (funcname == "readlinkat")
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bufParam = bufParam ? bufParam->nextArgument() : nullptr;
if (!Token::Match(bufParam, "%varid% , %num% )", varid))
return;
const MathLib::bigint n = MathLib::toLongNumber(bufParam->strAt(2));
if (total_size > 0 && n > total_size)
outOfBoundsError(bufParam, funcname + "() buf size", true, n, total_size);
if (!_settings->inconclusive)
return;
// only writing a part of the buffer
if (n < total_size)
return;
// readlink()/readlinkat() never terminates the buffer, check the end of the scope for buffer termination.
bool found_termination = false;
const Token *scope_end = scope_begin->link();
for (const Token *tok2 = bufParam->tokAt(4); tok2 && tok2 != scope_end; tok2 = tok2->next()) {
if (Token::Match(tok2, "%varid% [ %any% ] = 0 ;", bufParam->varId())) {
found_termination = true;
break;
}
}
if (!found_termination) {
bufferNotZeroTerminatedError(ftok, bufParam->str(), funcname);
} else if (n == total_size) {
possibleReadlinkBufferOverrunError(ftok, funcname, bufParam->str());
}
}
//---------------------------------------------------------------------------
// Checking local variables in a scope
//---------------------------------------------------------------------------
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void CheckBufferOverrun::checkGlobalAndLocalVariable()
{
// check string literals
for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
if (Token::Match(tok, "%str% [ %num% ]")) {
const std::size_t strLen = tok->str().size() - 2; // Don't count enclosing quotes
const std::size_t index = (std::size_t)std::atoi(tok->strAt(2).c_str());
if (index > strLen)
bufferOverrunError(tok, tok->str());
}
}
// check all known fixed size arrays first by just looking them up
const SymbolDatabase* symbolDatabase = _tokenizer->getSymbolDatabase();
for (unsigned int i = 1; i <= _tokenizer->varIdCount(); i++) {
const Variable *var = symbolDatabase->getVariableFromVarId(i);
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if (var && var->isArray() && var->dimension(0) > 0) {
const ArrayInfo arrayInfo(var, _tokenizer, i);
const Token *tok = var->nameToken();
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while (tok && tok->str() != ";") {
if (tok->str() == "{") {
if (Token::simpleMatch(tok->previous(), "= {"))
tok = tok->link();
else
break;
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}
tok = tok->next();
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}
if (!tok)
break;
if (tok->str() == "{")
tok = tok->next();
checkScope(tok, arrayInfo);
}
}
// find all dynamically allocated arrays next
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
2011-11-26 21:02:04 +01:00
for (const Token *tok = scope->classStart; tok != scope->classEnd; tok = tok->next()) {
// if the previous token exists, it must be either a variable name or "[;{}]"
if (tok->previous() && (!tok->previous()->isName() && !Token::Match(tok->previous(), "[;{}]")))
continue;
2011-01-06 13:02:21 +01:00
// size : Max array index
MathLib::bigint size = 0;
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// type : The type of a array element
std::string type;
// varid : The variable id for the array
const Variable *var = nullptr;
// nextTok : number of tokens used in variable declaration - used to skip to next statement.
int nextTok = 0;
_errorLogger->reportProgress(_tokenizer->list.getSourceFilePath(),
"Check (BufferOverrun::checkGlobalAndLocalVariable)",
tok->progressValue());
if (Token::Match(tok, "[*;{}] %var% = new %type% [ %num% ]")) {
size = MathLib::toLongNumber(tok->strAt(6));
type = tok->strAt(4);
var = tok->next()->variable();
nextTok = 8;
if (size < 0) {
negativeMemoryAllocationSizeError(tok->next()->next());
}
} else if (Token::Match(tok, "[*;{}] %var% = new %type% ( %num% )")) {
size = 1;
type = tok->strAt(4);
var = tok->next()->variable();
nextTok = 8;
} else if (Token::Match(tok, "[;{}] %var% = %str% ;") &&
tok->next()->variable() &&
tok->next()->variable()->isPointer()) {
size = 1 + int(tok->tokAt(3)->strValue().size());
type = "char";
var = tok->next()->variable();
nextTok = 4;
} else if (Token::Match(tok, "[*;{}] %var% = malloc|alloca ( %num% ) ;")) {
size = MathLib::toLongNumber(tok->strAt(5));
type = "char"; // minimum type, typesize=1
var = tok->next()->variable();
nextTok = 7;
if (size < 0) {
negativeMemoryAllocationSizeError(tok->next()->next());
}
/** @todo false negatives: this may be too conservative */
if (!var || var->typeEndToken()->str() != "*" || var->typeStartToken()->next() != var->typeEndToken())
continue;
// get name of variable
type = var->typeStartToken()->str();
// malloc() gets count of bytes and not count of
// elements, so we should calculate count of elements
// manually
const unsigned int sizeOfType = _tokenizer->sizeOfType(var->typeStartToken());
if (sizeOfType > 0) {
size /= static_cast<int>(sizeOfType);
}
if (size < 0) {
negativeMemoryAllocationSizeError(tok->next()->next());
}
} else {
continue;
}
if (var == 0)
continue;
Token sizeTok(0);
sizeTok.str(type);
const MathLib::bigint total_size = size * static_cast<int>(_tokenizer->sizeOfType(&sizeTok));
if (total_size == 0)
continue;
std::vector<std::string> v;
ArrayInfo temp(var->declarationId(), tok->next()->str(), total_size / size, size);
checkScope(tok->tokAt(nextTok), v, temp);
}
}
}
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// Checking member variables of structs..
//---------------------------------------------------------------------------
2009-07-13 16:00:15 +02:00
void CheckBufferOverrun::checkStructVariable()
{
const SymbolDatabase * symbolDatabase = _tokenizer->getSymbolDatabase();
// find every class and struct
const std::size_t classes = symbolDatabase->classAndStructScopes.size();
for (std::size_t i = 0; i < classes; ++i) {
const Scope * scope = symbolDatabase->classAndStructScopes[i];
// check all variables to see if they are arrays
std::list<Variable>::const_iterator var;
2011-10-13 20:53:06 +02:00
for (var = scope->varlist.begin(); var != scope->varlist.end(); ++var) {
if (var->isArray()) {
// create ArrayInfo from the array variable
ArrayInfo arrayInfo(&*var, _tokenizer);
// find every function
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t j = 0; j < functions; ++j) {
const Scope * func_scope = symbolDatabase->functionScopes[j];
// If struct is declared in a function then check
// if scope_func matches
if (scope->nestedIn->type == Scope::eFunction &&
scope->nestedIn != &*func_scope) {
continue;
}
// check for member variables
2011-10-13 20:53:06 +02:00
if (func_scope->functionOf == &*scope) {
// only check non-empty function
if (func_scope->classStart->next() != func_scope->classEnd) {
// start checking after the {
const Token *tok = func_scope->classStart->next();
checkScope(tok, arrayInfo);
}
}
// skip inner scopes..
/** @todo false negatives: handle inner scopes someday */
if (scope->nestedIn->isClassOrStruct())
continue;
std::vector<std::string> varname;
varname.push_back("");
varname.push_back(arrayInfo.varname());
// search the function and it's parameters
2011-10-13 20:53:06 +02:00
for (const Token *tok3 = func_scope->classDef; tok3 && tok3 != func_scope->classEnd; tok3 = tok3->next()) {
// search for the class/struct name
if (tok3->str() != scope->className)
continue;
// find all array variables
int posOfSemicolon = -1;
// Declare variable: Fred fred1;
if (Token::Match(tok3->next(), "%var% ;"))
varname[0] = tok3->strAt(1);
else if (isArrayOfStruct(tok3,posOfSemicolon)) {
varname[0] = tok3->strAt(1);
int pos = 2;
for (int k = 0 ; k < posOfSemicolon; k++) {
for (int index = pos; index < (pos + 3); index++)
tok3->strAt(index);
pos += 3;
}
}
// Declare pointer or reference: Fred *fred1
else if (Token::Match(tok3->next(), "*|& %var% [,);=]"))
varname[0] = tok3->strAt(2);
else
continue;
// check for variable sized structure
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if (scope->type == Scope::eStruct && var->isPublic()) {
// last member of a struct with array size of 0 or 1 could be a variable sized structure
if (var->dimensions().size() == 1 && var->dimension(0) < 2 &&
2011-10-13 20:53:06 +02:00
var->index() == (scope->varlist.size() - 1)) {
// dynamically allocated so could be variable sized structure
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if (tok3->next()->str() == "*") {
// check for allocation
if ((Token::Match(tok3->tokAt(3), "; %var% = malloc ( %num% ) ;") ||
(Token::Match(tok3->tokAt(3), "; %var% = (") &&
Token::Match(tok3->linkAt(6), ") malloc ( %num% ) ;"))) &&
2011-10-13 20:53:06 +02:00
(tok3->strAt(4) == tok3->strAt(2))) {
MathLib::bigint size;
// find size of allocation
if (tok3->strAt(3) == "(") // has cast
size = MathLib::toLongNumber(tok3->linkAt(6)->strAt(3));
else
size = MathLib::toLongNumber(tok3->strAt(8));
// We don't calculate the size of a structure even when we know
// the size of the members. We just assign a length of 100 for
// any struct. If the size is less than 100, we assume the
// programmer knew the size and specified it rather than using
// sizeof(struct). If the size is greater than 100, we assume
// the programmer specified the size as sizeof(struct) + number.
// Either way, this is just a guess and could be wrong. The
// information to make the right decision has been simplified
// away by the time we get here.
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if (size != 100) { // magic number for size of struct
// check if a real size was specified and give up
// malloc(10) rather than malloc(sizeof(struct))
if (size < 100 || arrayInfo.element_size() == 0)
continue;
// calculate real array size based on allocated size
MathLib::bigint elements = (size - 100) / arrayInfo.element_size();
arrayInfo.num(0, arrayInfo.num(0) + elements);
}
}
// size unknown so assume it is a variable sized structure
else
continue;
}
}
}
// Goto end of statement.
const Token *checkTok = nullptr;
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while (tok3 && tok3 != func_scope->classEnd) {
// End of statement.
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if (tok3->str() == ";") {
checkTok = tok3;
break;
}
// End of function declaration..
if (Token::simpleMatch(tok3, ") ;"))
break;
// Function implementation..
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if (Token::simpleMatch(tok3, ") {")) {
checkTok = tok3->tokAt(2);
break;
}
tok3 = tok3->next();
}
if (!tok3)
break;
if (!checkTok)
continue;
// Check variable usage..
ArrayInfo temp = arrayInfo;
temp.declarationId(0); // do variable lookup by variable and member names rather than varid
std::string varnames; // use class and member name for messages
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for (std::size_t k = 0; k < varname.size(); ++k)
varnames += (k == 0 ? "" : ".") + varname[k];
temp.varname(varnames);
checkScope(checkTok, varname, temp);
}
}
}
}
}
}
//---------------------------------------------------------------------------
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void CheckBufferOverrun::bufferOverrun()
{
checkGlobalAndLocalVariable();
checkStructVariable();
checkBufferAllocatedWithStrlen();
checkStringArgument();
checkInsecureCmdLineArgs();
}
//---------------------------------------------------------------------------
void CheckBufferOverrun::bufferOverrun2()
{
// singlepass checking using ast, symboldatabase and valueflow
for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
// Array index
if (!Token::Match(tok, "%var% ["))
continue;
// TODO: what to do about negative index..
const Token *index = tok->next()->astOperand2();
if (index && index->getValueLE(-1LL,_settings))
continue;
// Set full varname..
std::string varname(tok->str());
if (tok->astParent() && tok->astParent()->str() == ".") {
const Token *parent = tok->astParent();
while (parent->astParent() && parent->astParent()->str() == ".")
parent = parent->astParent();
varname = parent->expressionString();
}
const Token * const strtoken = tok->getValueTokenMinStrSize();
if (strtoken) {
ArrayInfo arrayInfo(tok->varId(), varname, 1U, Token::getStrSize(strtoken));
valueFlowCheckArrayIndex(tok->next(), arrayInfo);
}
else {
const Variable * const var = tok->variable();
if (!var || var->nameToken() == tok || !var->isArray())
continue;
// TODO: last array in struct..
if (var->dimension(0) <= 1 && Token::simpleMatch(var->nameToken()->linkAt(1),"] ; }"))
continue;
ArrayInfo arrayInfo(var,_tokenizer);
arrayInfo.varname(varname);
valueFlowCheckArrayIndex(tok->next(), arrayInfo);
}
}
}
//---------------------------------------------------------------------------
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MathLib::bigint CheckBufferOverrun::countSprintfLength(const std::string &input_string, const std::list<const Token*> &parameters)
{
bool percentCharFound = false;
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std::size_t input_string_size = 1;
bool handleNextParameter = false;
std::string digits_string = "";
bool i_d_x_f_found = false;
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std::list<const Token*>::const_iterator paramIter = parameters.begin();
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std::size_t parameterLength = 0;
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for (std::string::size_type i = 0; i < input_string.length(); ++i) {
if (input_string[i] == '\\') {
if (input_string[i+1] == '0')
break;
++input_string_size;
++i;
continue;
}
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if (percentCharFound) {
switch (input_string[i]) {
case 'f':
case 'x':
case 'X':
case 'i':
i_d_x_f_found = true;
case 'c':
case 'e':
case 'E':
case 'g':
case 'o':
case 'u':
case 'p':
case 'n':
handleNextParameter = true;
break;
case 'd':
i_d_x_f_found = true;
if (paramIter != parameters.end() && *paramIter && (*paramIter)->type() != Token::eString)
parameterLength = (*paramIter)->str().length();
handleNextParameter = true;
break;
case 's':
if (paramIter != parameters.end() && *paramIter && (*paramIter)->type() == Token::eString)
parameterLength = Token::getStrLength(*paramIter);
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handleNextParameter = true;
break;
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}
}
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if (input_string[i] == '%')
percentCharFound = !percentCharFound;
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else if (percentCharFound) {
digits_string.append(1, input_string[i]);
}
if (!percentCharFound)
input_string_size++;
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if (handleNextParameter) {
unsigned int tempDigits = static_cast<unsigned int>(std::abs(std::atoi(digits_string.c_str())));
if (i_d_x_f_found)
tempDigits = std::max(static_cast<unsigned int>(tempDigits), 1U);
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if (digits_string.find('.') != std::string::npos) {
const std::string endStr = digits_string.substr(digits_string.find('.') + 1);
const unsigned int maxLen = std::max(static_cast<unsigned int>(std::abs(std::atoi(endStr.c_str()))), 1U);
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if (input_string[i] == 's') {
// For strings, the length after the dot "%.2s" will limit
// the length of the string.
if (parameterLength > maxLen)
parameterLength = maxLen;
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} else {
// For integers, the length after the dot "%.2d" can
// increase required length
if (tempDigits < maxLen)
tempDigits = maxLen;
}
}
if (tempDigits < parameterLength)
input_string_size += parameterLength;
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else
input_string_size += tempDigits;
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parameterLength = 0;
digits_string = "";
i_d_x_f_found = false;
percentCharFound = false;
handleNextParameter = false;
if (paramIter != parameters.end())
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++paramIter;
}
}
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return (MathLib::bigint)input_string_size;
}
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void CheckBufferOverrun::checkSprintfCall(const Token *tok, const MathLib::bigint size)
{
if (size == 0)
return;
std::list<const Token*> parameters;
const Token* vaArg = tok->tokAt(2)->nextArgument()->nextArgument();
while (vaArg) {
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if (Token::Match(vaArg->next(), "[,)]")) {
if (vaArg->type() == Token::eString)
parameters.push_back(vaArg);
else if (vaArg->isNumber())
parameters.push_back(vaArg);
else
parameters.push_back(nullptr);
} else // Parameter is more complex than just a value or variable. Ignore it for now and skip to next token.
parameters.push_back(nullptr);
vaArg = vaArg->nextArgument();
}
MathLib::bigint len = countSprintfLength(tok->tokAt(2)->nextArgument()->strValue(), parameters);
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if (len > size) {
bufferOverrunError(tok);
}
}
//---------------------------------------------------------------------------
// Checking for allocating insufficient memory for copying a string by
// allocating only strlen(src) bytes instead of strlen(src) + 1 bytes (one
// extra for the terminating null character).
// Example:
// char *b = malloc(strlen(a)); // Should be malloc(strlen(a) + 1);
// strcpy(b, a); // <== Buffer overrun
//---------------------------------------------------------------------------
void CheckBufferOverrun::checkBufferAllocatedWithStrlen()
{
const SymbolDatabase* const symbolDatabase = _tokenizer->getSymbolDatabase();
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const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token *tok = scope->classStart->next(); tok && tok != scope->classEnd; tok = tok->next()) {
unsigned int dstVarId;
unsigned int srcVarId;
// Look for allocation of a buffer based on the size of a string
if (Token::Match(tok, "%var% = malloc|g_malloc|g_try_malloc ( strlen ( %var% ) )")) {
dstVarId = tok->varId();
srcVarId = tok->tokAt(6)->varId();
tok = tok->tokAt(8);
} else if (Token::Match(tok, "%var% = new char [ strlen ( %var% ) ]")) {
dstVarId = tok->varId();
srcVarId = tok->tokAt(7)->varId();
tok = tok->tokAt(9);
} else if (Token::Match(tok, "%var% = realloc|g_realloc|g_try_realloc ( %var% , strlen ( %var% ) )")) {
dstVarId = tok->varId();
srcVarId = tok->tokAt(8)->varId();
tok = tok->tokAt(10);
} else
continue;
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// To avoid false positives and added complexity, we will only look for
// improper usage of the buffer within the block that it was allocated
for (const Token* const end = tok->scope()->classEnd; tok && tok->next() && tok != end; tok = tok->next()) {
// If the buffers are modified, we can't be sure of their sizes
if (tok->varId() == srcVarId || tok->varId() == dstVarId)
break;
if (Token::Match(tok, "strcpy ( %varid% , %var% )", dstVarId) &&
tok->tokAt(4)->varId() == srcVarId) {
bufferOverrunError(tok);
} else if (Token::Match(tok, "sprintf ( %varid% , %str% , %var% )", dstVarId) &&
tok->tokAt(6)->varId() == srcVarId &&
tok->strAt(4).find("%s") != std::string::npos) {
bufferOverrunError(tok);
}
}
if (!tok)
return;
}
}
}
//---------------------------------------------------------------------------
// memcpy(temp, "hello world", 50);
//---------------------------------------------------------------------------
void CheckBufferOverrun::checkStringArgument()
{
const SymbolDatabase* const symbolDatabase = _tokenizer->getSymbolDatabase();
std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t functionIndex = 0; functionIndex < functions; ++functionIndex) {
const Scope * const scope = symbolDatabase->functionScopes[functionIndex];
for (const Token *tok = scope->classStart; tok != scope->classEnd; tok = tok->next()) {
if (!Token::Match(tok, "%var% (") || !_settings->library.hasminsize(tok->str()))
continue;
unsigned int argnr = 1;
for (const Token *argtok = tok->tokAt(2); argtok; argtok = argtok->nextArgument(), argnr++) {
if (!Token::Match(argtok, "%var%|%str% ,|)"))
continue;
const Token *strtoken = argtok->getValueTokenMinStrSize();
if (!strtoken)
continue;
const std::list<Library::ArgumentChecks::MinSize> *minsizes = _settings->library.argminsizes(tok->str(), argnr);
if (!minsizes)
continue;
if (checkMinSizes(*minsizes, tok, Token::getStrSize(strtoken), nullptr))
bufferOverrunError(argtok);
}
}
}
}
//---------------------------------------------------------------------------
// Checking for buffer overflow caused by copying command line arguments
// into fixed-sized buffers without checking to make sure that the command
// line arguments will not overflow the buffer.
//
// int main(int argc, char* argv[])
// {
// char prog[10];
// strcpy(prog, argv[0]); <-- Possible buffer overrun
// }
//---------------------------------------------------------------------------
void CheckBufferOverrun::checkInsecureCmdLineArgs()
{
const SymbolDatabase* const symbolDatabase = _tokenizer->getSymbolDatabase();
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std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
Function * j = scope->function;
if (j) {
const Token* tok = j->token;
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// Get the name of the argv variable
unsigned int varid = 0;
if (Token::Match(tok, "main ( int %var% , char * %var% [ ] ,|)")) {
varid = tok->tokAt(7)->varId();
} else if (Token::Match(tok, "main ( int %var% , char * * %var% ,|)")) {
varid = tok->tokAt(8)->varId();
}
if (varid == 0)
continue;
// Jump to the opening curly brace
tok = tok->next()->link();
if (!Token::simpleMatch(tok, ") {"))
continue;
tok = tok->next();
// Search within main() for possible buffer overruns involving argv
for (const Token* end = tok->link(); tok != end; tok = tok->next()) {
// If argv is modified or tested, its size may be being limited properly
if (tok->varId() == varid)
break;
// Match common patterns that can result in a buffer overrun
// e.g. strcpy(buffer, argv[0])
if (Token::Match(tok, "strcpy|strcat ( %var% , * %varid%", varid) ||
Token::Match(tok, "strcpy|strcat ( %var% , %varid% [", varid)) {
cmdLineArgsError(tok);
} else if (Token::Match(tok, "sprintf ( %var% , %str% , %varid% [", varid) &&
tok->strAt(4).find("%s") != std::string::npos) {
cmdLineArgsError(tok);
} else if (Token::Match(tok, "sprintf ( %var% , %str% , * %varid%", varid) &&
tok->strAt(4).find("%s") != std::string::npos) {
cmdLineArgsError(tok);
}
}
}
}
}
//---------------------------------------------------------------------------
void CheckBufferOverrun::negativeIndexError(const Token *tok, MathLib::bigint index)
{
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std::ostringstream ostr;
ostr << "Array index " << index << " is out of bounds.";
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reportError(tok, Severity::error, "negativeIndex", ostr.str());
}
void CheckBufferOverrun::negativeIndexError(const Token *tok, const ValueFlow::Value &index)
{
std::ostringstream ostr;
ostr << "Array index " << index.intvalue << " is out of bounds.";
if (index.condition)
ostr << " Otherwise there is useless condition at line " << index.condition->linenr() << ".";
reportError(tok, index.condition ? Severity::warning : Severity::error, "negativeIndex", ostr.str(), index.inconclusive);
}
CheckBufferOverrun::ArrayInfo::ArrayInfo()
: _element_size(0), _declarationId(0)
{
}
CheckBufferOverrun::ArrayInfo::ArrayInfo(const Variable *var, const Tokenizer *tokenizer, const unsigned int forcedeclid)
: _varname(var->name()), _declarationId((forcedeclid == 0U) ? var->declarationId() : forcedeclid)
{
for (std::size_t i = 0; i < var->dimensions().size(); i++)
_num.push_back(var->dimension(i));
if (var->typeEndToken()->str() == "*")
_element_size = tokenizer->sizeOfType(var->typeEndToken());
else if (var->typeStartToken()->str() == "struct")
_element_size = 100;
else
_element_size = tokenizer->sizeOfType(var->typeEndToken());
}
/**
* Create array info with specified data
* The intention is that this is only a temporary solution.. all
* checking should be based on ArrayInfo from the start and then
* this will not be needed as the declare can be used instead.
*/
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CheckBufferOverrun::ArrayInfo::ArrayInfo(unsigned int id, const std::string &name, MathLib::bigint size1, MathLib::bigint n)
: _varname(name), _element_size(size1), _declarationId(id)
{
_num.push_back(n);
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}
CheckBufferOverrun::ArrayInfo CheckBufferOverrun::ArrayInfo::limit(MathLib::bigint value) const
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{
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MathLib::bigint uvalue = std::max(MathLib::bigint(0), value);
MathLib::bigint n = 1;
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for (std::size_t i = 0; i < _num.size(); ++i)
n *= _num[i];
if (uvalue > n)
n = uvalue;
return ArrayInfo(_declarationId, _varname, _element_size, n - uvalue);
}
void CheckBufferOverrun::arrayIndexThenCheck()
{
if (!_settings->isEnabled("style"))
return;
const SymbolDatabase * const symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * const scope = symbolDatabase->functionScopes[i];
for (const Token *tok = scope->classStart; tok && tok != scope->classEnd; tok = tok->next()) {
if (Token::Match(tok, "%var% [ %var% ]")) {
tok = tok->tokAt(2);
unsigned int indexID = tok->varId();
if (!indexID)
continue;
const std::string& indexName(tok->str());
// skip array index..
tok = tok->tokAt(2);
while (tok && tok->str() == "[")
tok = tok->link()->next();
// syntax error
if (!tok)
return;
// skip comparison
if (tok->type() == Token::eComparisonOp)
tok = tok->tokAt(2);
// skip close parenthesis
if (tok->str() == ")")
tok = tok->next();
// check if array index is ok
// statement can be closed in parentheses, so "(| " is using
if (Token::Match(tok, "&& (| %varid% <|<=", indexID))
arrayIndexThenCheckError(tok, indexName);
else if (Token::Match(tok, "&& (| %any% >|>= %varid% !!+", indexID))
arrayIndexThenCheckError(tok, indexName);
}
}
}
}
void CheckBufferOverrun::arrayIndexThenCheckError(const Token *tok, const std::string &indexName)
{
reportError(tok, Severity::style, "arrayIndexThenCheck",
"Array index '" + indexName + "' is used before limits check.\n"
"Defensive programming: The variable '" + indexName + "' is used as an array index before it "
2013-10-23 08:03:37 +02:00
"is checked that is within limits. This can mean that the array might be accessed out of bounds. "
"Reorder conditions such as '(a[i] && i < 10)' to '(i < 10 && a[i])'. That way the array will "
"not be accessed if the index is out of limits.");
}
// -------------------------------------------------------------------------------------
// Check the second and the third parameter of the POSIX function write and validate
// their values.
// The parameters have the following meaning:
// - 1.parameter: file descripter (not required for this check)
// - 2.parameter: is a null terminated character string of the content to write.
// - 3.parameter: the number of bytes to write.
//
// This check is triggered if the size of the string ( 2. parameter) is lower than
// the number of bytes provided at the 3. parameter.
//
// References:
// - http://pubs.opengroup.org/onlinepubs/9699919799/functions/write.html
// - http://gd.tuwien.ac.at/languages/c/programming-bbrown/c_075.htm
// - http://codewiki.wikidot.com/c:system-calls:write
// -------------------------------------------------------------------------------------
void CheckBufferOverrun::writeOutsideBufferSize()
{
if (!_settings->standards.posix)
return;
const SymbolDatabase* const symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * const scope = symbolDatabase->functionScopes[i];
for (const Token *tok = scope->classStart; tok && tok != scope->classEnd; tok = tok->next()) {
if (Token::Match(tok, "pwrite|write (") && Token::Match(tok->tokAt(2)->nextArgument(), "%str% , %num%")) {
const std::string & functionName(tok->str());
tok = tok->tokAt(2)->nextArgument(); // set tokenptr to %str% parameter
const std::size_t stringLength = Token::getStrLength(tok)+1; // zero-terminated string!
tok = tok->tokAt(2); // set tokenptr to %num% parameter
const MathLib::bigint writeLength = MathLib::toLongNumber(tok->str());
if (static_cast<std::size_t>(writeLength) > stringLength)
writeOutsideBufferSizeError(tok, stringLength, writeLength, functionName);
}
}
}
}
void CheckBufferOverrun::writeOutsideBufferSizeError(const Token *tok, const std::size_t stringLength, const MathLib::bigint writeLength, const std::string &strFunctionName)
{
reportError(tok, Severity::error, "writeOutsideBufferSize",
"Writing " + MathLib::toString(writeLength-stringLength) + " bytes outside buffer size.\n"
"The number of bytes to write (" + MathLib::toString(writeLength) + " bytes) are bigger than the source buffer (" +MathLib::toString(stringLength)+ " bytes)."
" Please check the second and the third parameter of the function '"+strFunctionName+"'.");
}