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cppcheck/lib/checkbufferoverrun.cpp

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/*
* Cppcheck - A tool for static C/C++ code analysis
* Copyright (C) 2007-2011 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 "errorlogger.h"
#include "mathlib.h"
#include "symboldatabase.h"
#include <algorithm>
#include <sstream>
#include <list>
#include <cstring>
#include <cctype>
#include <climits>
#include <cassert> // <- assert
#include <cstdlib> // <- strtoul
//---------------------------------------------------------------------------
// Register this check class (by creating a static instance of it)
namespace
{
CheckBufferOverrun instance;
}
//---------------------------------------------------------------------------
void CheckBufferOverrun::arrayIndexOutOfBoundsError(const Token *tok, const ArrayInfo &arrayInfo, const std::vector<MathLib::bigint> &index)
{
std::ostringstream oss;
oss << "Array '" << arrayInfo.varname();
for (unsigned int i = 0; i < arrayInfo.num().size(); ++i)
oss << "[" << arrayInfo.num(i) << "]";
oss << "' index ";
if (index.size() == 1)
oss << index[0];
else
{
oss << arrayInfo.varname();
for (unsigned int i = 0; i < index.size(); ++i)
oss << "[" << index[i] << "]";
}
oss << " out of bounds";
reportError(tok, Severity::error, "arrayIndexOutOfBounds", oss.str().c_str());
}
void CheckBufferOverrun::arrayIndexOutOfBoundsError(const std::list<const Token *> &callstack, const ArrayInfo &arrayInfo, const std::vector<MathLib::bigint> &index)
{
std::ostringstream oss;
oss << "Array '" << arrayInfo.varname();
for (unsigned int i = 0; i < arrayInfo.num().size(); ++i)
oss << "[" << arrayInfo.num(i) << "]";
oss << "' index ";
if (index.size() == 1)
oss << index[0];
else
{
oss << arrayInfo.varname();
for (unsigned int i = 0; i < index.size(); ++i)
oss << "[" << index[i] << "]";
}
oss << " out of bounds";
reportError(callstack, Severity::error, "arrayIndexOutOfBounds", oss.str().c_str());
}
void CheckBufferOverrun::bufferOverrunError(const Token *tok, const std::string &varnames)
{
std::string v = varnames;
while (v.find(" ") != std::string::npos)
v.erase(v.find(" "), 1);
std::string errmsg("Buffer access out-of-bounds");
if (!v.empty())
errmsg += ": " + v;
reportError(tok, Severity::error, "bufferAccessOutOfBounds", errmsg);
}
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"
"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"
"The source buffer is larger than the destination buffer so there is the potential for overflowing the destination buffer.");
}
void CheckBufferOverrun::strncatUsageError(const Token *tok)
{
if (_settings && !_settings->isEnabled("style"))
return;
reportError(tok, Severity::warning, "strncatUsage",
"Dangerous usage of strncat - 3rd parameter is the maximum number of characters to append.\n"
"strncat appends at max its 3rd parameter's amount of characters. The safe way to use "
"strncat is to calculate remaining space in the buffer and use it as 3rd parameter.");
}
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)
{
std::ostringstream oss;
oss << what << " is out of bounds";
if (show_size_info)
oss << ": Supplied size " << supplied_size << " is larger than actual size of " << actual_size;
reportError(tok, Severity::error, "outOfBounds", oss.str());
}
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: Using pointer arithmetic so that the result does not point into or just past the end of the same 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("style"))
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 zero-terminated after the call to strncpy().\n"
"The use of strncpy() usually indicates that the programmer wants to ensure "
"the buffer is zero-terminated after the call. However if the (buffer) size given for "
"the strncpy() call matches the actual buffer size strncpy() does not add the "
"zero at the end of the buffer. This may cause bugs later in the code if "
"the code assumes buffer is zero-terminated.");
}
void CheckBufferOverrun::cmdLineArgsError(const Token *tok)
{
reportError(tok, Severity::error, "insecureCmdLineArgs", "Buffer overrun possible for long cmd-line args");
}
void CheckBufferOverrun::bufferNotZeroTerminatedError(const Token *tok, const std::string &varname, const std::string &function)
{
reportError(tok, Severity::warning, "bufferNotZeroTerminated",
"The buffer '" + varname + "' is not zero-terminated after the call to " + function + "().\n"
"This will cause bugs later in the code if the code assumes buffer is zero-terminated.");
}
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// Check array usage..
//---------------------------------------------------------------------------
/**
* @brief This is a helper class to be used with std::find_if
*/
class TokenStrEquals
{
public:
/**
* @param str Token::str() is compared against this.
*/
TokenStrEquals(const std::string &str)
: value(str)
{
}
/**
* Called automatically by std::find_if
* @param tok Token inside the list
*/
bool operator()(const Token *tok) const
{
return value == tok->str();
}
private:
TokenStrEquals& operator=(const TokenStrEquals&); // disallow assignments
const std::string value;
};
/**
* 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)
{
// Used later to check if the body belongs to a "if"
const std::string str1(tok->str());
// Count { and }
unsigned int indentlevel = 0;
for (; tok; tok = tok->next())
{
if (tok->str() == "{")
indentlevel++;
else if (tok->str() == "}")
{
// scan the else-block
if (indentlevel == 1 && Token::simpleMatch(tok, "} else {"))
{
--indentlevel;
continue;
}
else if (indentlevel <= 1)
{
break;
}
--indentlevel;
}
// If scanning a "if" block then bailout for "break"
else if (str1 == "if" && tok->str() == "break")
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;
}
/**
* Parse for loop initialization statement. Look for a counter variable
* \param tok [in] first token inside the parentheses
* \param varid [out] varid of counter variable
* \param init_value [out] init value of counter variable
* \return success => pointer to the for loop condition. fail => 0
*/
static const Token *for_init(const Token *tok, unsigned int &varid, std::string &init_value)
{
if (Token::Match(tok, "%var% = %any% ;"))
{
if (tok->tokAt(2)->isNumber())
{
init_value = tok->strAt(2);
}
varid = tok->varId();
tok = tok->tokAt(4);
}
else if (Token::Match(tok, "%type% %var% = %any% ;"))
{
if (tok->tokAt(3)->isNumber())
{
init_value = tok->strAt(3);
}
varid = tok->next()->varId();
tok = tok->tokAt(5);
}
else if (Token::Match(tok, "%type% %type% %var% = %any% ;"))
{
if (tok->tokAt(4)->isNumber())
{
init_value = tok->strAt(4);
}
varid = tok->tokAt(2)->varId();
tok = tok->tokAt(6);
}
else
return 0;
return tok;
}
/** Parse for condition */
static bool for_condition(const Token * const tok2, unsigned int varid, std::string &min_value, std::string &max_value, std::string &strindex, bool &maxMinFlipped)
{
if (Token::Match(tok2, "%varid% < %num% ;", varid) ||
Token::Match(tok2, "%varid% != %num% ; ++ %varid%", varid) ||
Token::Match(tok2, "%varid% != %num% ; %varid% ++", varid))
{
maxMinFlipped = false;
const MathLib::bigint value = MathLib::toLongNumber(tok2->strAt(2));
max_value = MathLib::toString<MathLib::bigint>(value - 1);
}
else if (Token::Match(tok2, "%varid% <= %num% ;", varid))
{
maxMinFlipped = false;
max_value = tok2->strAt(2);
}
else if (Token::Match(tok2, "%num% < %varid% ;", varid) ||
Token::Match(tok2, "%num% != %varid% ; ++ %varid%", varid) ||
Token::Match(tok2, "%num% != %varid% ; %varid% ++", varid))
{
maxMinFlipped = true;
const MathLib::bigint value = MathLib::toLongNumber(tok2->str());
max_value = min_value;
min_value = MathLib::toString<MathLib::bigint>(value + 1);
}
else if (Token::Match(tok2, "%num% <= %varid% ;", varid))
{
maxMinFlipped = true;
max_value = min_value;
min_value = tok2->str();
}
else
{
return false;
}
strindex = tok2->isName() ? tok2->str() : tok2->strAt(2);
return true;
}
/**
* calculate maximum value of loop variable
* @param stepvalue token that contains the step value
* @param min_value the minimum value of loop variable
* @param max_value maximum value of the loop variable
*/
static bool for_maxvalue(const Token * const stepvalue, const std::string &min_value, std::string &max_value)
{
if (!MathLib::isInt(stepvalue->str()))
return false;
// We have for example code: "for(i=2;i<22;i+=6)
// We can calculate that max value for i is 20, not 21
// 21-2 = 19
// 19/6 = 3
// 6*3+2 = 20
const MathLib::bigint num = MathLib::toLongNumber(stepvalue->str());
MathLib::bigint max = MathLib::toLongNumber(max_value);
const MathLib::bigint min = MathLib::toLongNumber(min_value);
max = ((max - min) / num) * num + min;
max_value = MathLib::toString<MathLib::bigint>(max);
return true;
}
/**
* Parse the third sub-statement in for head
* \param tok first token
* \param varid variable id of counter
* \param min_value min value of counter
* \param max_value max value of counter
* \param maxMinFlipped counting from max to min
*/
static bool for3(const Token * const tok,
unsigned int varid,
std::string &min_value,
std::string &max_value,
const bool maxMinFlipped)
{
assert(tok != 0);
if (Token::Match(tok, "%varid% += %num% )", varid) ||
Token::Match(tok, "%varid% = %num% + %varid% )", varid))
{
if (!for_maxvalue(tok->tokAt(2), min_value, max_value))
return false;
}
else if (Token::Match(tok, "%varid% = %varid% + %num% )", varid))
{
if (!for_maxvalue(tok->tokAt(4), min_value, max_value))
return false;
}
else if (Token::Match(tok, "%varid% -= %num% )", varid) ||
Token::Match(tok, "%varid% = %num% - %varid% )", varid))
{
if (!for_maxvalue(tok->tokAt(2), min_value, max_value))
return false;
}
else if (Token::Match(tok, "%varid% = %varid% - %num% )", varid))
{
if (!for_maxvalue(tok->tokAt(4), min_value, max_value))
return false;
}
else if (Token::Match(tok, "--| %varid% --| )", varid))
{
if (!maxMinFlipped && MathLib::toLongNumber(min_value) < MathLib::toLongNumber(max_value))
{
// Code relies on the fact that integer will overflow:
// for (unsigned int i = 3; i < 5; --i)
// Set min value in this case to zero.
max_value = min_value;
min_value = "0";
}
}
else if (! Token::Match(tok, "++| %varid% ++| )", varid))
{
return false;
}
return true;
}
/**
* Check is the counter variable increased elsewhere inside the loop or used
* for anything else except reading
* \param tok1 first token of for-body
* \param varid counter variable id
* \return bailout needed => true
*/
static bool for_bailout(const Token * const tok1, unsigned int varid)
{
for (const Token *loopTok = tok1; loopTok && loopTok != tok1->link(); loopTok = loopTok->next())
{
if (loopTok->varId() == varid)
{
// Counter variable used inside loop
if (Token::Match(loopTok->next(), "+=|-=|++|--|=") ||
Token::Match(loopTok->previous(), "++|--"))
{
return true;
}
}
}
return false;
}
void CheckBufferOverrun::parse_for_body(const Token *tok2, const ArrayInfo &arrayInfo, const std::string &strindex, bool condition_out_of_bounds, unsigned int counter_varid, const std::string &min_counter_value, const std::string &max_counter_value)
{
const std::string pattern((arrayInfo.varid() ? std::string("%varid%") : arrayInfo.varname()) + " [ " + strindex + " ]");
// count { and } for tok2
int indentlevel2 = 0;
for (; tok2; tok2 = tok2->next())
{
if (tok2->str() == ";" && indentlevel2 == 0)
break;
if (tok2->str() == "{")
++indentlevel2;
if (tok2->str() == "}")
{
--indentlevel2;
if (indentlevel2 <= 0)
break;
}
// TODO: try to reduce false negatives. This is just a quick fix
// for TestBufferOverrun::array_index_for_question
if (tok2->str() == "?")
break;
if (Token::simpleMatch(tok2, "for (") && Token::simpleMatch(tok2->next()->link(), ") {"))
{
const Token *endpar = tok2->next()->link();
const Token *startbody = endpar->next();
const Token *endbody = startbody->link();
tok2 = endbody;
continue;
}
if (Token::Match(tok2, "if|switch"))
{
if (bailoutIfSwitch(tok2, arrayInfo.varid()))
break;
}
if (condition_out_of_bounds && Token::Match(tok2, pattern.c_str(), arrayInfo.varid()))
{
bufferOverrunError(tok2, arrayInfo.varname());
break;
}
else if (arrayInfo.varid() && counter_varid > 0 && !min_counter_value.empty() && !max_counter_value.empty())
{
// Is the loop variable used to calculate the array index?
// In this scope it is determined if such calculated
// array indexes are out of bounds.
// Only the minimum and maximum results of the calculation is
// determined
// Minimum calculated array index
int min_index = 0;
// Maximum calculated array index
int max_index = 0;
if (Token::Match(tok2, "%varid% [ %var% +|-|*|/ %num% ]", arrayInfo.varid()) &&
tok2->tokAt(2)->varId() == counter_varid)
{
// operator: +-*/
const char action = tok2->strAt(3)[0];
// second operator
const std::string &second(tok2->tokAt(4)->str());
//printf("min_index: %s %c %s\n", min_counter_value.c_str(), action, second.c_str());
//printf("max_index: %s %c %s\n", max_counter_value.c_str(), action, second.c_str());
min_index = std::atoi(MathLib::calculate(min_counter_value, second, action, _tokenizer).c_str());
max_index = std::atoi(MathLib::calculate(max_counter_value, second, action, _tokenizer).c_str());
}
else if (Token::Match(tok2, "%varid% [ %num% +|-|*|/ %var% ]", arrayInfo.varid()) &&
tok2->tokAt(4)->varId() == counter_varid)
{
// operator: +-*/
const char action = tok2->strAt(3)[0];
// first operand
const std::string &first(tok2->tokAt(2)->str());
//printf("min_index: %s %c %s\n", first.c_str(), action, min_counter_value.c_str());
//printf("max_index: %s %c %s\n", first.c_str(), action, max_counter_value.c_str());
min_index = std::atoi(MathLib::calculate(first, min_counter_value, action, _tokenizer).c_str());
max_index = std::atoi(MathLib::calculate(first, max_counter_value, action, _tokenizer).c_str());
}
//printf("min_index = %d, max_index = %d, size = %d\n", min_index, max_index, size);
if (min_index < 0 || max_index < 0)
{
std::vector<MathLib::bigint> indexes;
indexes.push_back(std::min(min_index, max_index));
arrayIndexOutOfBoundsError(tok2, arrayInfo, indexes);
}
// skip 0 length arrays
if (arrayInfo.num(0) && (min_index >= (int)arrayInfo.num(0) || max_index >= (int)arrayInfo.num(0)))
{
std::vector<MathLib::bigint> indexes;
indexes.push_back(std::max(min_index, max_index));
arrayIndexOutOfBoundsError(tok2, arrayInfo, indexes);
}
}
}
}
void CheckBufferOverrun::checkFunctionParameter(const Token &tok, unsigned int par, const ArrayInfo &arrayInfo)
{
// total_size : which parameter in function call takes the total size?
std::map<std::string, unsigned int> total_size;
total_size["fgets"] = 2; // The second argument for fgets can't exceed the total size of the array
total_size["memcmp"] = 3;
total_size["memcpy"] = 3;
total_size["memmove"] = 3;
if (par == 1)
{
// reading from array
// if it is zero terminated properly there won't be buffer overruns
total_size["strncat"] = 3;
total_size["strncpy"] = 3;
total_size["memset"] = 3;
total_size["fread"] = 1001; // parameter 2 * parameter 3
total_size["fwrite"] = 1001; // parameter 2 * parameter 3
}
if (par == 2)
{
total_size["read"] = 3;
total_size["pread"] = 3;
total_size["write"] = 3;
total_size["recv"] = 3;
total_size["recvfrom"] = 3;
total_size["send"] = 3;
total_size["sendto"] = 3;
}
std::map<std::string, unsigned int>::const_iterator it = total_size.find(tok.str());
if (it != total_size.end())
{
if (arrayInfo.element_size() == 0)
return;
// arg : the index of the "wanted" argument in the function call.
unsigned int arg = it->second;
// Parse function call. When a ',' is seen, arg is decremented.
// if arg becomes 1 then the current function parameter is the wanted parameter.
// if arg becomes 1000 then multiply current and next argument.
for (const Token *tok2 = tok.tokAt(2); tok2; tok2 = tok2->next())
{
if (tok2->str() == "(")
{
tok2 = tok2->link();
continue;
}
if (tok2->str() == ")")
break;
if (tok2->str() == ",")
{
--arg;
if (arg == 1)
{
if (Token::Match(tok2, ", %num% ,|)"))
{
const MathLib::bigint sz = MathLib::toLongNumber(tok2->strAt(1));
MathLib::bigint elements = 1;
for (unsigned int i = 0; i < arrayInfo.num().size(); ++i)
elements *= arrayInfo.num(i);
if (sz < 0 || sz > int(elements * arrayInfo.element_size()))
{
bufferOverrunError(&tok, arrayInfo.varname());
}
}
else if (Token::Match(tok2, ", %any% ,|)") && tok2->next()->str()[0] == '\'')
{
sizeArgumentAsCharError(tok2->next());
}
break;
}
if (arg == 1000) // special code. This parameter multiplied with the next must not exceed total_size
{
if (Token::Match(tok2, ", %num% , %num% ,|)"))
{
const MathLib::bigint sz = MathLib::toLongNumber(MathLib::multiply(tok2->strAt(1), tok2->strAt(3)));
MathLib::bigint elements = 1;
for (unsigned int i = 0; i < arrayInfo.num().size(); ++i)
elements *= arrayInfo.num(i);
if (sz < 0 || sz > int(elements * arrayInfo.element_size()))
{
bufferOverrunError(&tok, arrayInfo.varname());
}
}
break;
}
}
}
}
// Calling a user function?
// only 1-dimensional arrays can be checked currently
else if (arrayInfo.num().size() == 1)
{
const Token *ftok = _tokenizer->getFunctionTokenByName(tok.str().c_str());
if (Token::Match(ftok, "%var% (") && Token::Match(ftok->next()->link(), ") const| {"))
{
// Get varid for the corresponding parameter..
unsigned int parameter = 1;
unsigned int parameterVarId = 0;
for (const Token *ftok2 = ftok->tokAt(2); ftok2; ftok2 = ftok2->next())
{
if (ftok2->str() == ",")
{
if (parameter >= par)
break;
++parameter;
}
else if (ftok2->str() == ")")
break;
else if (parameter == par && Token::Match(ftok2, "%var% ,|)|["))
{
// check type..
const Token *type = ftok2->previous();
while (Token::Match(type, "*|const"))
type = type->previous();
if (type && _tokenizer->sizeOfType(type) == arrayInfo.element_size())
parameterVarId = ftok2->varId();
}
}
// No parameterVarId => bail out
if (parameterVarId == 0)
return;
// Step into the function scope..
ftok = ftok->next()->link();
if (!Token::Match(ftok, ") const| {"))
return;
ftok = Token::findmatch(ftok, "{");
ftok = ftok->next();
// Check the parameter usage in the function scope..
for (; ftok; ftok = ftok->next())
{
if (Token::Match(ftok, "if|for|while ("))
{
// bailout if there is buffer usage..
if (bailoutIfSwitch(ftok, parameterVarId))
{
break;
}
// no bailout is needed. skip the if-block
else
{
// goto end of if block..
ftok = ftok->next()->link()->next()->link();
if (Token::simpleMatch(ftok, "} else {"))
ftok = ftok->tokAt(2)->link();
if (!ftok)
break;
continue;
}
}
if (ftok->str() == "}")
break;
if (ftok->varId() == parameterVarId)
{
if (Token::Match(ftok->previous(), "-- %var%") ||
Token::Match(ftok, "%var% --"))
break;
if (Token::Match(ftok->previous(), "=|;|{|}|%op% %var% [ %num% ]"))
{
const MathLib::bigint index = MathLib::toLongNumber(ftok->strAt(2));
if (index >= 0 && arrayInfo.num(0) > 0 && index >= arrayInfo.num(0))
{
std::list<const Token *> callstack;
callstack.push_back(&tok);
callstack.push_back(ftok);
std::vector<MathLib::bigint> indexes;
indexes.push_back(index);
arrayIndexOutOfBoundsError(callstack, arrayInfo, indexes);
}
}
}
}
}
}
}
void CheckBufferOverrun::checkFunctionCall(const Token *tok, const ArrayInfo &arrayInfo)
{
// 1st parameter..
if (Token::Match(tok->tokAt(2), "%varid% ,|)", arrayInfo.varid()))
checkFunctionParameter(*tok, 1, arrayInfo);
else if (Token::Match(tok->tokAt(2), "%varid% + %num% ,|)", arrayInfo.varid()))
{
const ArrayInfo ai(arrayInfo.limit(MathLib::toLongNumber(tok->strAt(4))));
checkFunctionParameter(*tok, 1, ai);
}
// goto 2nd parameter and check it..
for (const Token *tok2 = tok->tokAt(2); tok2; tok2 = tok2->next())
{
if (tok2->str() == "(")
{
tok2 = tok2->link();
continue;
}
if (tok2->str() == ";" || tok2->str() == ")")
break;
if (tok2->str() == ",")
{
if (Token::Match(tok2, ", %varid% ,|)", arrayInfo.varid()))
checkFunctionParameter(*tok, 2, arrayInfo);
else if (Token::Match(tok2, ", %varid% + %num% ,|)", arrayInfo.varid()))
{
const ArrayInfo ai(arrayInfo.limit(MathLib::toLongNumber(tok2->strAt(3))));
checkFunctionParameter(*tok, 2, ai);
}
break;
}
}
}
void CheckBufferOverrun::checkScopeForBody(const Token *tok, const ArrayInfo &arrayInfo, bool &bailout)
{
bailout = false;
const Token *tok2 = tok->tokAt(2);
const MathLib::bigint size = arrayInfo.num(0);
// Check if there is a break in the body..
{
const Token *bodyStart = tok->next()->link()->next();
const Token *bodyEnd = bodyStart->link();
if (Token::findmatch(bodyStart, "break ;", bodyEnd))
return;
}
unsigned int counter_varid = 0;
std::string min_counter_value;
std::string max_counter_value;
tok2 = for_init(tok2, counter_varid, min_counter_value);
if (tok2 == 0 || counter_varid == 0)
return;
bool maxMinFlipped = false;
std::string strindex;
if (!for_condition(tok2, counter_varid, min_counter_value, max_counter_value, strindex, maxMinFlipped))
return;
// Get index variable and stopsize.
bool condition_out_of_bounds = bool(size > 0);
if (MathLib::toLongNumber(max_counter_value) < size)
condition_out_of_bounds = false;
if (!for3(tok2->tokAt(4), counter_varid, min_counter_value, max_counter_value, maxMinFlipped))
return;
if (Token::Match(tok2->tokAt(4), "%var% =|+=|-=") && MathLib::toLongNumber(max_counter_value) <= size)
condition_out_of_bounds = false;
// Goto the end parenthesis of the for-statement: "for (x; y; z)" ..
tok2 = tok->next()->link();
if (!tok2 || !tok2->tokAt(5))
{
bailout = true;
return;
}
// Check is the counter variable increased elsewhere inside the loop or used
// for anything else except reading
if (for_bailout(tok2->next(), counter_varid))
{
bailout = true;
return;
}
parse_for_body(tok2->next(), arrayInfo, strindex, condition_out_of_bounds, counter_varid, min_counter_value, max_counter_value);
}
void CheckBufferOverrun::checkScope(const Token *tok, const std::vector<std::string> &varname, const ArrayInfo &arrayInfo)
{
const MathLib::bigint size = arrayInfo.num(0);
const MathLib::bigint total_size = arrayInfo.element_size() * arrayInfo.num(0);
unsigned int varid = arrayInfo.varid();
std::string varnames;
for (unsigned int i = 0; i < varname.size(); ++i)
varnames += (i == 0 ? "" : " . ") + varname[i];
const unsigned char varc(static_cast<unsigned char>(varname.empty() ? 0U : (varname.size() - 1) * 2U));
if (Token::simpleMatch(tok, "return"))
{
tok = tok->next();
if (!tok)
return;
}
// Array index..
if ((varid > 0 && Token::Match(tok, "%varid% [ %num% ]", varid)) ||
(varid == 0 && Token::Match(tok, (varnames + " [ %num% ]").c_str())))
{
const MathLib::bigint index = MathLib::toLongNumber(tok->strAt(2 + varc));
if (index >= size)
{
std::vector<MathLib::bigint> indexes;
indexes.push_back(index);
arrayIndexOutOfBoundsError(tok->tokAt(varc), arrayInfo, indexes);
}
}
// If the result of pointer arithmetic means that the pointer is
// out of bounds then this flag will be set.
bool pointerIsOutOfBounds = false;
// Count { and } for tok
int indentlevel = 0;
for (; tok; tok = tok->next())
{
if (tok->str() == "{")
{
++indentlevel;
}
else if (tok->str() == "}")
{
--indentlevel;
if (indentlevel < 0)
return;
}
if (varid != 0 && Token::Match(tok, "%varid% = new|malloc|realloc", varid))
{
// Abort
break;
}
// reassign buffer
if (varid > 0 && Token::Match(tok, "[;{}] %varid% =", varid))
{
// using varid .. bailout
if (!Token::Match(tok->tokAt(3), "%varid%", varid))
break;
pointerIsOutOfBounds = false;
}
// Array index..
if ((varid > 0 && ((tok->str() == "return" || (!tok->isName() && !Token::Match(tok, "[.&]"))) && Token::Match(tok->next(), "%varid% [ %num% ]", varid))) ||
(varid == 0 && ((tok->str() == "return" || (!tok->isName() && !Token::Match(tok, "[.&]"))) && Token::Match(tok->next(), (varnames + " [ %num% ]").c_str()))))
{
std::vector<MathLib::bigint> indexes;
const Token *tok2 = tok->tokAt(2 + varc);
for (; Token::Match(tok2, "[ %num% ]"); tok2 = tok2->tokAt(3))
{
const MathLib::bigint index = MathLib::toLongNumber(tok2->strAt(1));
indexes.push_back(index);
}
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 (unsigned int i = 0; i < indexes.size(); ++i)
{
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->tokAt(-1), "%var% ."))
tok3 = tok3->tokAt(-2);
// just taking the address?
const bool addr(Token::Match(tok3, "&") ||
Token::simpleMatch(tok3->tokAt(-1), "& ("));
// taking address of 1 past end?
if (addr && totalIndex == totalElements)
continue;
// Is totalIndex in bounds?
if (totalIndex > totalElements || totalIndex < 0)
{
arrayIndexOutOfBoundsError(tok->tokAt(1 + varc), arrayInfo, indexes);
}
// Is any array index out of bounds?
else
{
// check each index for overflow
for (unsigned int i = 0; i < indexes.size(); ++i)
{
if (indexes[i] >= arrayInfo.num(i))
{
// The access is still within the memory range for the array
// so it may be intentional.
if (_settings->inconclusive)
{
arrayIndexOutOfBoundsError(tok->tokAt(1 + varc), arrayInfo, indexes);
break; // only warn about the first one
}
}
}
}
}
tok = tok2;
continue;
}
// memset, memcmp, memcpy, strncpy, fgets..
if (varid == 0 && size > 0)
{
if (Token::Match(tok, ("%var% ( " + varnames + " ,").c_str()))
checkFunctionParameter(*tok, 1, arrayInfo);
if (Token::Match(tok, ("%var% ( %var% , " + varnames + " ,").c_str()))
checkFunctionParameter(*tok, 2, arrayInfo);
}
// Loop..
if (Token::simpleMatch(tok, "for ("))
{
const ArrayInfo arrayInfo1(varid, varnames, (unsigned int)size, (unsigned int)total_size);
bool bailout = false;
checkScopeForBody(tok, arrayInfo1, bailout);
if (bailout)
break;
continue;
}
// Writing data into array..
if ((varid > 0 && Token::Match(tok, "strcpy|strcat ( %varid% , %str% )", varid)) ||
(varid == 0 && Token::Match(tok, ("strcpy|strcat ( " + varnames + " , %str% )").c_str())))
{
const std::size_t len = Token::getStrLength(tok->tokAt(varc + 4));
if (total_size > 0 && len >= (unsigned int)total_size)
{
bufferOverrunError(tok, varid > 0 ? "" : varnames.c_str());
continue;
}
}
else if ((varid > 0 && Token::Match(tok, "strcpy|strcat ( %varid% , %var% )", varid)) ||
(varid == 0 && Token::Match(tok, ("strcpy|strcat ( " + varnames + " , %var% )").c_str())))
{
const Variable *var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(tok->tokAt(4)->varId());
if (var && var->isArray() && var->dimensions().size() == 1)
{
const std::size_t len = (std::size_t)var->dimension(0);
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 = varid > 0 ? std::string("strcat ( %varid% , %str% ) ;") : ("strcat ( " + varnames + " , %str% ) ;");
if (Token::Match(tok, strcatPattern.c_str(), varid))
{
size_t charactersAppend = 0;
const Token *tok2 = tok;
while (tok2 && Token::Match(tok2, strcatPattern.c_str(), varid))
{
charactersAppend += Token::getStrLength(tok2->tokAt(4 + varc));
if (charactersAppend >= static_cast<size_t>(total_size))
{
bufferOverrunError(tok2);
break;
}
tok2 = tok2->tokAt(7 + varc);
}
}
// sprintf..
// TODO: change total_size to an unsigned value and remove the "&& total_size > 0" check.
const std::string sprintfPattern = varid > 0 ? std::string("sprintf ( %varid% , %str% [,)]") : ("sprintf ( " + varnames + " , %str% [,)]");
if (Token::Match(tok, sprintfPattern.c_str(), varid) && total_size > 0)
{
checkSprintfCall(tok, static_cast<unsigned int>(total_size));
}
// snprintf..
const std::string snprintfPattern = varid > 0 ? std::string("snprintf ( %varid% , %num% ,") : ("snprintf ( " + varnames + " , %num% ,");
if (Token::Match(tok, snprintfPattern.c_str(), varid))
{
const MathLib::bigint n = MathLib::toLongNumber(tok->strAt(4 + varc));
if (n > total_size)
outOfBoundsError(tok->tokAt(4 + varc), "snprintf size", true, n, total_size);
}
// Check function call..
if (Token::Match(tok, "%var% (") && total_size > 0)
{
// No varid => function calls are not handled
if (varid == 0)
continue;
const ArrayInfo arrayInfo1(varid, varnames, total_size / size, size);
checkFunctionCall(tok, arrayInfo1);
}
// undefined behaviour: result of pointer arithmetic is out of bounds
if (varid && Token::Match(tok, "= %varid% + %num% ;", varid))
{
const MathLib::bigint index = MathLib::toLongNumber(tok->strAt(3));
if (index > size && _settings->isEnabled("portability"))
pointerOutOfBoundsError(tok->next(), "buffer");
if (index >= size && Token::Match(tok->tokAt(-2), "[;{}] %varid% =", varid))
pointerIsOutOfBounds = true;
}
if (pointerIsOutOfBounds && Token::Match(tok, "[;{}=] * %varid% [;=]", varid))
{
outOfBoundsError(tok->tokAt(2), tok->strAt(2), false, 0, 0);
}
}
}
void CheckBufferOverrun::checkScope(const Token *tok, const ArrayInfo &arrayInfo)
{
const MathLib::bigint total_size = arrayInfo.num(0) * arrayInfo.element_size();
// Count { and } for tok
unsigned int indentlevel = 0;
for (; tok; tok = tok->next())
{
if (tok->str() == "{")
{
++indentlevel;
}
else if (tok->str() == "}")
{
if (indentlevel == 0)
return;
--indentlevel;
}
// Skip array declarations
else if (Token::Match(tok, "[;{}] %type% *| %var% [") &&
tok->strAt(1) != "return")
{
tok = tok->tokAt(3);
continue;
}
else if (Token::Match(tok, "%varid% [ %num% ]", arrayInfo.varid()))
{
std::vector<MathLib::bigint> indexes;
for (const Token *tok2 = tok->next(); Token::Match(tok2, "[ %num% ]"); tok2 = tok2->tokAt(3))
{
const MathLib::bigint index = MathLib::toLongNumber(tok2->strAt(1));
if (index < 0)
{
indexes.clear();
break;
}
indexes.push_back(index);
}
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 (unsigned int i = 0; i < indexes.size(); ++i)
{
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 *tok2 = tok->previous();
while (tok2 && Token::Match(tok2->tokAt(-1), "%var% ."))
tok2 = tok2->tokAt(-2);
// just taking the address?
const bool addr(Token::Match(tok2, "&") ||
Token::simpleMatch(tok2->tokAt(-1), "& ("));
// taking address of 1 past end?
if (addr && totalIndex == totalElements)
continue;
// Is totalIndex in bounds?
if (totalIndex > totalElements)
{
arrayIndexOutOfBoundsError(tok, arrayInfo, indexes);
}
// Is any array index out of bounds?
else
{
// check each index for overflow
for (unsigned int i = 0; i < indexes.size(); ++i)
{
if (indexes[i] >= 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
}
}
}
}
}
}
// Loop..
else if (Token::simpleMatch(tok, "for ("))
{
bool bailout = false;
checkScopeForBody(tok, arrayInfo, bailout);
if (bailout)
break;
continue;
}
// Check function call..
if (Token::Match(tok, "%var% ("))
{
checkFunctionCall(tok, arrayInfo);
}
if (Token::Match(tok, "strncpy|memcpy|memmove ( %varid% , %str% , %num% )", arrayInfo.varid()))
{
unsigned int num = (unsigned int)MathLib::toLongNumber(tok->strAt(6));
if (Token::getStrLength(tok->tokAt(4)) >= (unsigned int)total_size && (unsigned int)total_size == num)
{
if (_settings->inconclusive)
bufferNotZeroTerminatedError(tok, tok->strAt(2), tok->str());
}
}
if ((Token::Match(tok, "strncpy|strncat ( %varid% , %var% , %num% )", arrayInfo.varid())) ||
(Token::Match(tok, "strncpy|strncat ( %varid% , %var% [ %any% ] , %num% )", arrayInfo.varid())))
{
const int offset = tok->strAt(5) == "[" ? 3 : 0;
// 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(tok->strAt(6 + offset));
if (num >= total_size)
{
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()))
{
// this is currently 'inconclusive'. See TestBufferOverrun::terminateStrncpy3
if (_settings->isEnabled("style") && _settings->inconclusive)
terminateStrncpyError(tok, tok->strAt(2));
}
break;
}
}
}
}
// Dangerous usage of strncat..
if (tok->str() == "strncat")
{
const MathLib::bigint n = MathLib::toLongNumber(tok->strAt(6 + offset));
if (n >= total_size)
strncatUsageError(tok);
}
// Dangerous usage of strncpy + strncat..
if (Token::Match(tok->tokAt(8 + offset), "; strncat ( %varid% , %any% , %num% )", arrayInfo.varid()))
{
const MathLib::bigint n = MathLib::toLongNumber(tok->strAt(6 + offset)) + MathLib::toLongNumber(tok->strAt(15 + offset));
if (n > total_size)
strncatUsageError(tok->tokAt(9 + offset));
}
}
// Writing data into array..
if (Token::Match(tok, "strcpy|strcat ( %varid% , %str% )", arrayInfo.varid()))
{
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% ) ;", arrayInfo.varid()))
{
std::size_t charactersAppend = 0;
const Token *tok2 = tok;
while (tok2 && Token::Match(tok2, "strcat ( %varid% , %str% ) ;", arrayInfo.varid()))
{
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% [,)]", arrayInfo.varid()))
{
checkSprintfCall(tok, total_size);
}
// snprintf..
if (total_size > 0 && Token::Match(tok, "snprintf ( %varid% , %num% ,", arrayInfo.varid()))
{
const MathLib::bigint n = MathLib::toLongNumber(tok->strAt(4));
if (n > total_size)
outOfBoundsError(tok->tokAt(4), "snprintf size", true, n, total_size);
}
// undefined behaviour: result of pointer arithmetic is out of bounds
if (_settings->isEnabled("portability") && Token::Match(tok, "= %varid% + %num% ;", arrayInfo.varid()))
{
const MathLib::bigint index = MathLib::toLongNumber(tok->strAt(3));
if (index < 0 || index > arrayInfo.num(0))
{
pointerOutOfBoundsError(tok->next(), "array");
}
}
}
}
//---------------------------------------------------------------------------
// Checking local variables in a scope
//---------------------------------------------------------------------------
void CheckBufferOverrun::checkGlobalAndLocalVariable()
{
// check all known fixed size arrays first by just looking them up
for (size_t i = 1; i <= _tokenizer->varIdCount(); i++)
{
const Variable *var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(i);
if (var && var->isArray() && var->dimension(0) > 0)
{
ArrayInfo arrayInfo(var, _tokenizer);
const Token *tok = var->nameToken();
while (tok && tok->str() != ";")
{
if (tok->str() == "{")
{
if (Token::simpleMatch(tok->previous(), "= {"))
tok = tok->link();
else
break;
}
tok = tok->next();
}
if (!tok)
break;
if (tok->str() == "{")
tok = tok->next();
checkScope(tok, arrayInfo);
}
}
// find all dynamically allocated arrays next by parsing the token stream
// Count { and } when parsing all tokens
int indentlevel = 0;
for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next())
{
if (tok->str() == "{")
++indentlevel;
else if (tok->str() == "}")
--indentlevel;
// size : Max array index
MathLib::bigint size = 0;
// type : The type of a array element
std::string type;
// varid : The variable id for the array
unsigned int varid = 0;
// nextTok : number of tokens used in variable declaration - used to skip to next statement.
int nextTok = 0;
// if the previous token exists, it must be either a variable name or "[;{}]"
if (tok->previous() && (!tok->previous()->isName() && !Token::Match(tok->previous(), "[;{}]")))
continue;
_errorLogger->reportProgress(_tokenizer->getFiles()->front(),
"Check (BufferOverrun::checkGlobalAndLocalVariable)",
tok->progressValue());
if (indentlevel > 0 && Token::Match(tok, "[*;{}] %var% = new %type% [ %num% ]"))
{
size = MathLib::toLongNumber(tok->strAt(6));
type = tok->strAt(4);
varid = tok->tokAt(1)->varId();
nextTok = 8;
}
else if (indentlevel > 0 && Token::Match(tok, "[*;{}] %var% = new %type% ( %num% )"))
{
size = 1;
type = tok->strAt(4);
varid = tok->tokAt(1)->varId();
nextTok = 8;
}
else if (indentlevel > 0 &&
Token::Match(tok, "[;{}] %var% = %str% ;") &&
tok->next()->varId() > 0 &&
NULL != Token::findmatch(_tokenizer->tokens(), "[;{}] const| %type% * %varid% ;", tok->next()->varId()))
{
size = 1 + int(tok->tokAt(3)->strValue().size());
type = "char";
varid = tok->next()->varId();
nextTok = 4;
}
else if (indentlevel > 0 && Token::Match(tok, "[*;{}] %var% = malloc|alloca ( %num% ) ;"))
{
size = MathLib::toLongNumber(tok->strAt(5));
type = "char"; // minimum type, typesize=1
varid = tok->tokAt(1)->varId();
nextTok = 7;
if (varid > 0)
{
// get type of variable
const Variable *var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(varid);
/** @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
unsigned int sizeOfType = _tokenizer->sizeOfType(var->typeStartToken());
if (sizeOfType > 0)
size /= static_cast<int>(sizeOfType);
}
}
else
{
continue;
}
if (varid == 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(varid, tok->next()->str(), total_size / size, size);
checkScope(tok->tokAt(nextTok), v, temp);
}
}
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// Checking member variables of structs..
//---------------------------------------------------------------------------
void CheckBufferOverrun::checkStructVariable()
{
const SymbolDatabase * symbolDatabase = _tokenizer->getSymbolDatabase();
std::list<Scope>::const_iterator scope;
// find every class and struct
for (scope = symbolDatabase->scopeList.begin(); scope != symbolDatabase->scopeList.end(); ++scope)
{
// only check classes and structures
if (!scope->isClassOrStruct())
continue;
// check all variables to see if they are arrays
std::list<Variable>::const_iterator var;
for (var = scope->varlist.begin(); var != scope->varlist.end(); ++var)
{
// find all array variables
if (var->isArray())
{
// create ArrayInfo from the array variable
ArrayInfo arrayInfo(&*var, _tokenizer);
std::list<Scope>::const_iterator func_scope;
// find every function
for (func_scope = symbolDatabase->scopeList.begin(); func_scope != symbolDatabase->scopeList.end(); ++func_scope)
{
// only check functions
if (func_scope->type != Scope::eFunction)
continue;
// check for member variables
if (func_scope->functionOf == &*scope)
{
// only check non-empty function
if (func_scope->function->start->next() != func_scope->function->start->link())
{
// start checking after the {
const Token *tok = func_scope->function->start->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
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;
// Declare variable: Fred fred1;
if (Token::Match(tok3->next(), "%var% ;"))
varname[0] = tok3->strAt(1);
// 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
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 &&
var->index() == (scope->varlist.size() - 1))
{
// dynamically allocated so could be variable sized structure
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->tokAt(6)->link(), ") malloc ( %num% ) ;"))) &&
(tok3->strAt(4) == tok3->strAt(2)))
{
MathLib::bigint size;
// find size of allocation
if (tok3->strAt(3) == "(") // has cast
size = MathLib::toLongNumber(tok3->tokAt(6)->link()->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.
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)
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 = NULL;
while (tok3 && tok3 != func_scope->classEnd)
{
// End of statement.
if (tok3->str() == ";")
{
CheckTok = tok3;
break;
}
// End of function declaration..
if (Token::simpleMatch(tok3, ") ;"))
break;
// Function implementation..
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.varid(0); // do variable lookup by variable and member names rather than varid
std::string varnames; // use class and member name for messages
for (unsigned int i = 0; i < varname.size(); ++i)
varnames += (i == 0 ? "" : ".") + varname[i];
temp.varname(varnames);
checkScope(CheckTok, varname, temp);
}
}
}
}
}
}
//---------------------------------------------------------------------------
void CheckBufferOverrun::bufferOverrun()
{
checkGlobalAndLocalVariable();
checkStructVariable();
checkBufferAllocatedWithStrlen();
checkInsecureCmdLineArgs();
}
//---------------------------------------------------------------------------
MathLib::bigint CheckBufferOverrun::countSprintfLength(const std::string &input_string, const std::list<const Token*> &parameters)
{
bool percentCharFound = false;
std::size_t input_string_size = 1;
bool handleNextParameter = false;
std::string digits_string = "";
bool i_d_x_f_found = false;
std::list<const Token*>::const_iterator paramIter = parameters.begin();
std::size_t parameterLength = 0;
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;
}
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)->str()[0] != '"')
parameterLength = (*paramIter)->str().length();
handleNextParameter = true;
break;
case 's':
if (paramIter != parameters.end() && *paramIter && (*paramIter)->str()[0] == '"')
parameterLength = Token::getStrLength(*paramIter);
handleNextParameter = true;
break;
}
}
if (input_string[i] == '%')
percentCharFound = !percentCharFound;
else if (percentCharFound)
{
digits_string.append(1, input_string[i]);
}
if (!percentCharFound)
input_string_size++;
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);
if (digits_string.find('.') != std::string::npos)
{
const std::string endStr = digits_string.substr(digits_string.find('.') + 1);
unsigned int maxLen = std::max(static_cast<unsigned int>(std::abs(std::atoi(endStr.c_str()))), 1U);
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;
}
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;
else
input_string_size += tempDigits;
parameterLength = 0;
digits_string = "";
i_d_x_f_found = false;
percentCharFound = false;
handleNextParameter = false;
if (paramIter != parameters.end())
++paramIter;
}
}
return (MathLib::bigint)input_string_size;
}
void CheckBufferOverrun::checkSprintfCall(const Token *tok, const MathLib::bigint size)
{
if (size == 0)
return;
const Token *end = tok->next()->link();
// Count the number of tokens in the buffer variable's name
int varc = 0;
for (const Token *tok1 = tok->tokAt(3); tok1 != end; tok1 = tok1->next())
{
if (tok1->str() == ",")
break;
++ varc;
}
std::list<const Token*> parameters;
if (tok->tokAt(5 + varc)->str() == ",")
{
for (const Token *tok2 = tok->tokAt(5 + varc); tok2 && tok2 != end; tok2 = tok2->next())
{
if (Token::Match(tok2, ", %any% [,)]"))
{
if (Token::Match(tok2->next(), "%str%"))
parameters.push_back(tok2->next());
else if (Token::Match(tok2->next(), "%num%"))
parameters.push_back(tok2->next());
else
parameters.push_back(0);
}
else
{
// Parameter is more complex, than just a value or variable. Ignore it for now
// and skip to next token.
parameters.push_back(0);
// count parentheses for tok3
int ind = 0;
for (const Token *tok3 = tok2->next(); tok3; tok3 = tok3->next())
{
if (tok3->str() == "(")
++ind;
else if (tok3->str() == ")")
{
--ind;
if (ind < 0)
break;
}
else if (ind == 0 && tok3->str() == ",")
{
tok2 = tok3->previous();
break;
}
}
if (ind < 0)
break;
}
}
}
MathLib::bigint len = countSprintfLength(tok->tokAt(4 + varc)->strValue(), parameters);
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 char pattern[] = "%var% = new|malloc|g_malloc|g_try_malloc|realloc|g_realloc|g_try_realloc";
for (const Token *tok = Token::findmatch(_tokenizer->tokens(), pattern); tok; tok = Token::findmatch(tok->next(),pattern))
{
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;
// count { and } for tok
int indentlevel = 0;
for (; tok && tok->next(); tok = tok->next())
{
// To avoid false positives and added complexity, we will only look for
// improper usage of the buffer within the block that it was allocated
if (tok->str() == "{")
{
++indentlevel;
}
else if (tok->str() == "}")
{
--indentlevel;
if (indentlevel < 0)
return;
}
// 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->tokAt(4)->str().find("%s") != std::string::npos)
{
bufferOverrunError(tok);
}
}
}
}
//---------------------------------------------------------------------------
// 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 char pattern[] = "main ( int %var% , char *";
for (const Token *tok = Token::findmatch(_tokenizer->tokens(), pattern); tok; tok = Token::findmatch(tok->next(),pattern))
{
// 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
int indentlevel = -1;
for (; tok; tok = tok->next())
{
if (tok->str() == "{")
{
++indentlevel;
}
else if (tok->str() == "}")
{
--indentlevel;
if (indentlevel < 0)
return;
}
// 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->tokAt(4)->str().find("%s") != std::string::npos)
{
cmdLineArgsError(tok);
}
else if (Token::Match(tok, "sprintf ( %var% , %str% , * %varid%", varid) &&
tok->tokAt(4)->str().find("%s") != std::string::npos)
{
cmdLineArgsError(tok);
}
}
}
}
//---------------------------------------------------------------------------
void CheckBufferOverrun::negativeIndexError(const Token *tok, MathLib::bigint index)
{
std::ostringstream ostr;
ostr << "Array index " << index << " is out of bounds";
reportError(tok, Severity::error, "negativeIndex", ostr.str());
}
void CheckBufferOverrun::negativeIndex()
{
const char pattern[] = "[ %num% ]";
for (const Token *tok = Token::findmatch(_tokenizer->tokens(), pattern); tok; tok = Token::findmatch(tok->next(),pattern))
{
const MathLib::bigint index = MathLib::toLongNumber(tok->next()->str());
if (index < 0)
{
// Negative index. Check if it's an array.
const Token *tok2 = tok;
while (Token::simpleMatch(tok2->previous(), "]"))
tok2 = tok2->previous()->link();
if (tok2->previous() && tok2->previous()->varId())
{
const Variable *var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(tok2->previous()->varId());
if (var && var->isArray())
negativeIndexError(tok, index);
}
}
}
}
#include "executionpath.h"
/// @addtogroup Checks
/// @{
CheckBufferOverrun::ArrayInfo::ArrayInfo()
{
_element_size = 0;
_varid = 0;
}
CheckBufferOverrun::ArrayInfo::ArrayInfo(const CheckBufferOverrun::ArrayInfo &ai)
{
*this = ai;
}
CheckBufferOverrun::ArrayInfo::ArrayInfo(const Variable *var, const Tokenizer *tokenizer)
{
_varid = var->varId();
_varname = var->name();
for (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());
}
CheckBufferOverrun::ArrayInfo & CheckBufferOverrun::ArrayInfo::operator=(const CheckBufferOverrun::ArrayInfo &ai)
{
if (&ai != this)
{
_element_size = ai._element_size;
_num = ai._num;
_varid = ai._varid;
_varname = ai._varname;
}
return *this;
}
/**
* 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.
*/
CheckBufferOverrun::ArrayInfo::ArrayInfo(unsigned int id, const std::string &name, MathLib::bigint size1, MathLib::bigint n)
{
_element_size = size1;
_num.push_back(n);
_varid = id;
_varname = name;
}
CheckBufferOverrun::ArrayInfo CheckBufferOverrun::ArrayInfo::limit(MathLib::bigint value) const
{
MathLib::bigint uvalue = std::max(MathLib::bigint(0), value);
MathLib::bigint n = 1;
for (unsigned int i = 0; i < _num.size(); ++i)
n *= _num[i];
if (uvalue > n)
n = uvalue;
return ArrayInfo(_varid, _varname, _element_size, n - uvalue);
}
bool CheckBufferOverrun::ArrayInfo::declare(const Token *tok, const Tokenizer &tokenizer)
{
_num.clear();
_element_size = 0;
_varname.clear();
if (!tok)
return false;
if (!tok->isName() || tok->str() == "return")
return false;
while (tok && (tok->str() == "static" ||
tok->str() == "const" ||
tok->str() == "extern"))
tok = tok->next();
// ivar : number of type tokens
int ivar = 0;
if (Token::Match(tok, "%type% *| %var% ["))
ivar = 1;
else if (Token::Match(tok, "%type% %type% *| %var% ["))
ivar = 2;
else
return false;
if (tok->str().find(":") != std::string::npos)
return false;
// Goto variable name token, get element size..
const Token *vartok = tok->tokAt(ivar);
if (vartok->str() == "*")
{
_element_size = tokenizer.sizeOfType(vartok);
vartok = vartok->next();
}
else if (tok->str() == "struct")
{
_element_size = 100;
}
else
{
_element_size = tokenizer.sizeOfType(tok);
}
_varname = vartok->str();
_varid = vartok->varId();
if (!_varid)
return false;
const Token *atok = vartok->tokAt(2);
if (!Token::Match(atok, "%num% ] ;|=|["))
return false;
while (Token::Match(atok, "%num% ] ;|=|["))
{
_num.push_back(MathLib::toLongNumber(atok->str()));
atok = atok->next();
if (Token::simpleMatch(atok, "] ["))
atok = atok->tokAt(2);
}
if (Token::Match(atok, "] = !!{"))
return false;
return (!_num.empty() && Token::Match(atok, "] ;|="));
}
/**
* @brief %Check for buffer overruns (using ExecutionPath)
*/
class ExecutionPathBufferOverrun : public ExecutionPath
{
public:
/** Startup constructor */
ExecutionPathBufferOverrun(Check *c, const std::map<unsigned int, CheckBufferOverrun::ArrayInfo> &arrayinfo)
: ExecutionPath(c, 0), arrayInfo(arrayinfo), value(0)
{
}
private:
/** @brief Copy this check. Called from the ExecutionPath baseclass. */
ExecutionPath *copy()
{
return new ExecutionPathBufferOverrun(*this);
}
/** @brief is other execution path equal? */
bool is_equal(const ExecutionPath *e) const
{
const ExecutionPathBufferOverrun *c = static_cast<const ExecutionPathBufferOverrun *>(e);
return (value == c->value);
}
/** @brief Buffer information */
const std::map<unsigned int, CheckBufferOverrun::ArrayInfo> &arrayInfo;
/** no implementation => compiler error if used by accident */
void operator=(const ExecutionPathBufferOverrun &);
/** internal constructor for creating extra checks */
ExecutionPathBufferOverrun(Check *c, const std::map<unsigned int, CheckBufferOverrun::ArrayInfo> &arrayinfo, unsigned int varid_)
: ExecutionPath(c, varid_),
arrayInfo(arrayinfo)
{
// Pretend that variables are initialized to 0
// This checking is not about uninitialized variables
value = 0;
}
/** @brief Variable value. */
MathLib::bigint value;
/**
* @brief Assign value to a variable
* @param checks the execution paths
* @param varid the variable id
* @param value the assigned value
*/
static void assign_value(std::list<ExecutionPath *> &checks, unsigned int varid, const std::string &value)
{
if (varid == 0)
return;
std::list<ExecutionPath *>::const_iterator it;
for (it = checks.begin(); it != checks.end(); ++it)
{
ExecutionPathBufferOverrun *c = dynamic_cast<ExecutionPathBufferOverrun *>(*it);
if (c && c->varId == varid)
c->value = MathLib::toLongNumber(value);
}
}
/**
* @brief Found array usage, analyse the array usage
* @param tok token where usage occurs (only used when reporting the error)
* @param checks The execution paths
* @param varid1 variable id for the array
* @param varid2 variable id for the index
*/
static void array_index(const Token *tok, std::list<ExecutionPath *> &checks, unsigned int varid1, unsigned int varid2)
{
if (checks.empty() || varid1 == 0 || varid2 == 0)
return;
// Locate array info corresponding to varid1
CheckBufferOverrun::ArrayInfo ai;
{
ExecutionPathBufferOverrun *c = dynamic_cast<ExecutionPathBufferOverrun *>(checks.front());
std::map<unsigned int, CheckBufferOverrun::ArrayInfo>::const_iterator it;
it = c->arrayInfo.find(varid1);
if (it == c->arrayInfo.end())
return;
ai = it->second;
}
// Check if varid2 variable has a value that is out-of-bounds
std::list<ExecutionPath *>::const_iterator it;
for (it = checks.begin(); it != checks.end(); ++it)
{
ExecutionPathBufferOverrun *c = dynamic_cast<ExecutionPathBufferOverrun *>(*it);
if (c && c->varId == varid2 && c->value >= ai.num(0))
{
// variable value is out of bounds, report error
CheckBufferOverrun *checkBufferOverrun = dynamic_cast<CheckBufferOverrun *>(c->owner);
if (checkBufferOverrun)
{
std::vector<MathLib::bigint> index;
index.push_back(c->value);
checkBufferOverrun->arrayIndexOutOfBoundsError(tok, ai, index);
break;
}
}
}
}
const Token *parse(const Token &tok, std::list<ExecutionPath *> &checks) const
{
if (Token::Match(tok.previous(), "[;{}]"))
{
// Declaring variable..
if (Token::Match(&tok, "%type% %var% ;") && tok.isStandardType())
{
checks.push_back(new ExecutionPathBufferOverrun(owner, arrayInfo, tok.next()->varId()));
return tok.tokAt(2);
}
// Assign variable..
if (Token::Match(&tok, "%var% = %num% ;"))
{
assign_value(checks, tok.varId(), tok.strAt(2));
return tok.tokAt(3);
}
}
// Assign variable (unknown value = 0)..
if (Token::Match(&tok, "%var% ="))
{
assign_value(checks, tok.varId(), "0");
return &tok;
}
// Assign variable (unknown value = 0)..
if (Token::Match(tok.tokAt(-2), "(|, & %var% ,|)"))
{
assign_value(checks, tok.varId(), "0");
return &tok;
}
// Array index..
if (Token::Match(&tok, "%var% [ %var% ]"))
{
array_index(&tok, checks, tok.varId(), tok.tokAt(2)->varId());
return tok.tokAt(3);
}
return &tok;
}
};
/// @}
void CheckBufferOverrun::executionPaths()
{
// Parse all variables and extract array info..
std::map<unsigned int, ArrayInfo> arrayInfo;
for (size_t i = 1; i <= _tokenizer->varIdCount(); i++)
{
const Variable *var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(i);
if (var && var->isArray() && var->dimension(0) > 0)
arrayInfo[i] = ArrayInfo(var, _tokenizer);
}
// Perform checking - check how the arrayInfo arrays are used
ExecutionPathBufferOverrun c(this, arrayInfo);
checkExecutionPaths(_tokenizer->tokens(), &c);
}
void CheckBufferOverrun::arrayIndexThenCheck()
{
if (!_settings->isEnabled("style"))
return;
for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next())
{
if (Token::Match(tok, "%var% [ %var% ]"))
{
const std::string arrayName(tok->str());
const std::string indexName(tok->strAt(2));
// skip array index..
tok = tok->tokAt(4);
while (tok && tok->str() == "[")
tok = tok->link()->next();
// syntax error
if (!tok)
return;
// skip comparison
if (Token::Match(tok, "==|!=|<|<=|>|>= %any% &&"))
tok = tok->tokAt(2);
// check if array index is ok
if (Token::Match(tok, ("&& " + indexName + " <|<=").c_str()))
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 array index and then there is a check that it 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 when the index is out of limits.");
}
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