cppcheck/src/checkbufferoverrun.cpp

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/*
* Cppcheck - A tool for static C/C++ code analysis
* Copyright (C) 2007-2009 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 <algorithm>
#include <sstream>
#include <list>
#include <cstring>
#include <cstdlib> // <- strtoul
//---------------------------------------------------------------------------
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// Register this check class (by creating a static instance of it)
namespace
{
CheckBufferOverrunClass instance;
}
//---------------------------------------------------------------------------
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void CheckBufferOverrunClass::arrayIndexOutOfBounds(const Token *tok)
{
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_callStack.push_back(tok);
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arrayIndexOutOfBounds();
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_callStack.pop_back();
}
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void CheckBufferOverrunClass::arrayIndexOutOfBounds()
{
reportError(_callStack, "all", "arrayIndexOutOfBounds", "Array index out of bounds");
}
void CheckBufferOverrunClass::bufferOverrun(const Token *tok)
{
reportError(tok, "all", "bufferOverrun", "Buffer overrun");
}
void CheckBufferOverrunClass::strncatUsage(const Token *tok)
{
reportError(tok, "all", "strncatUsage", "Dangerous usage of strncat, possible buffer overrun");
}
void CheckBufferOverrunClass::outOfBounds(const Token *tok, const std::string &what)
{
reportError(tok, "error", "outOfBounds", what + " is out of bounds");
}
void CheckBufferOverrunClass::sizeArgumentAsChar(const Token *tok)
{
reportError(tok, "all", "sizeArgumentAsChar", "The size argument is given as a char constant");
}
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// Check array usage..
//---------------------------------------------------------------------------
void CheckBufferOverrunClass::CheckBufferOverrun_CheckScope(const Token *tok, const char *varname[], const int size, const int total_size, unsigned int varid)
{
unsigned int varc = 0;
std::string varnames;
while (varname[varc])
{
if (varc > 0)
varnames += " . ";
varnames += varname[varc];
++varc;
}
if (varc == 0)
varc = 1;
varc = 2 * (varc - 1);
// Array index..
if (varid > 0)
{
if (Token::Match(tok, "%varid% [ %num% ]", varid))
{
const char *num = tok->strAt(2);
if (std::strtol(num, NULL, 10) >= size)
{
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arrayIndexOutOfBounds(tok->next());
}
}
}
else if (Token::Match(tok, std::string(varnames + " [ %num% ]").c_str()))
{
const char *num = tok->strAt(2 + varc);
if (std::strtol(num, NULL, 10) >= size)
{
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arrayIndexOutOfBounds(tok->next());
}
}
int indentlevel = 0;
for (; tok; tok = tok->next())
{
if (tok->str() == "{")
{
++indentlevel;
}
else if (tok->str() == "}")
{
--indentlevel;
if (indentlevel < 0)
return;
}
// Array index..
if (varid > 0)
{
if (!tok->isName() && !Token::Match(tok, "[.&]") && Token::Match(tok->next(), "%varid% [ %num% ]", varid))
{
const char *num = tok->strAt(3);
if (std::strtol(num, NULL, 10) >= size)
{
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arrayIndexOutOfBounds(tok->next());
}
}
}
else if (!tok->isName() && !Token::Match(tok, "[.&]") && Token::Match(tok->next(), std::string(varnames + " [ %num% ]").c_str()))
{
const char *num = tok->next()->strAt(2 + varc);
if (std::strtol(num, NULL, 10) >= size)
{
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arrayIndexOutOfBounds(tok->next());
}
tok = tok->tokAt(4);
continue;
}
// memset, memcmp, memcpy, strncpy, fgets..
if (varid > 0)
{
if (Token::Match(tok, "memset|memcpy|memmove|memcmp|strncpy|fgets"))
{
if (Token::Match(tok->next(), "( %varid% , %any% , %any% )", varid) ||
Token::Match(tok->next(), "( %var% , %varid% , %any% )", varid))
{
const Token *tokSz = tok->tokAt(6);
if (tokSz->str()[0] == '\'')
sizeArgumentAsChar(tok);
else if (tokSz->isNumber())
{
const char *num = tok->strAt(6);
if (std::atoi(num) > total_size)
{
bufferOverrun(tok);
}
}
}
}
}
else if (Token::Match(tok, "memset|memcpy|memmove|memcmp|strncpy|fgets"))
{
if (Token::Match(tok->next(), std::string("( " + varnames + " , %num% , %num% )").c_str()) ||
Token::Match(tok->next(), std::string("( %var% , " + varnames + " , %num% )").c_str()))
{
const char *num = tok->strAt(varc + 6);
if (std::atoi(num) > total_size)
{
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bufferOverrun(tok);
}
}
continue;
}
// Loop..
if (Token::simpleMatch(tok, "for ("))
{
const Token *tok2 = tok->tokAt(2);
// for - setup..
if (Token::Match(tok2, "%var% = %any% ;"))
tok2 = tok2->tokAt(4);
else if (Token::Match(tok2, "%type% %var% = %any% ;"))
tok2 = tok2->tokAt(5);
else if (Token::Match(tok2, "%type% %type% %var% = %any% ;"))
tok2 = tok2->tokAt(6);
else
continue;
// for - condition..
if (!Token::Match(tok2, "%var% < %num% ;") && !Token::Match(tok2, "%var% <= %num% ;"))
continue;
// Get index variable and stopsize.
const char *strindex = tok2->str().c_str();
int value = ((tok2->strAt(1)[1] == '=') ? 1 : 0) + std::atoi(tok2->strAt(2));
if (value <= size)
continue;
// Goto the end of the for loop..
while (tok2 && tok2->str() != ")")
tok2 = tok2->next();
if (!tok2 || !tok2->tokAt(5))
break;
std::ostringstream pattern;
pattern << varnames << " [ " << strindex << " ]";
int indentlevel2 = 0;
while ((tok2 = tok2->next()))
{
if (tok2->str() == ";" && indentlevel2 == 0)
break;
if (tok2->str() == "{")
++indentlevel2;
if (tok2->str() == "}")
{
--indentlevel2;
if (indentlevel2 <= 0)
break;
}
if (Token::Match(tok2, pattern.str().c_str()))
{
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bufferOverrun(tok2);
break;
}
}
continue;
}
// Writing data into array..
if (Token::Match(tok, ("strcpy|strcat ( " + varnames + " , %str% )").c_str()))
{
int len = 0;
const char *str = tok->strAt(varc + 4);
while (*str)
{
if (*str == '\\')
++str;
++str;
++len;
}
if (len > 2 && len >= (int)size + 2)
{
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bufferOverrun(tok);
}
continue;
}
// Dangerous usage of strncat..
if (varid > 0 && Token::Match(tok, "strncat ( %varid% , %any% , %num% )", varid))
{
int n = atoi(tok->strAt(6));
if (n == size)
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strncatUsage(tok);
}
// Dangerous usage of strncpy + strncat..
if (varid > 0 && Token::Match(tok, "strncpy|strncat ( %varid% , %any% , %num% ) ; strncat ( %varid% , %any% , %num% )", varid))
{
int n = atoi(tok->strAt(6)) + atoi(tok->strAt(15));
if (n > size)
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strncatUsage(tok->tokAt(9));
}
// sprintf..
if (varid > 0 && Token::Match(tok, "sprintf ( %varid% , %str% ,", varid))
{
int len = 0;
for (const Token *tok2 = tok->tokAt(6); tok2 && tok2->str() != ")"; tok2 = tok2->next())
{
if (tok2->str()[0] == '\"')
{
len -= 2;
const char *str = tok->str().c_str();
while (*str)
{
if (*str == '\\')
++str;
++str;
++len;
}
}
}
if (len > (int)size)
{
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bufferOverrun(tok);
}
}
// snprintf..
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if (varid > 0 && Token::Match(tok, "snprintf ( %varid% , %num% ,", varid))
{
int n = std::atoi(tok->strAt(4));
if (n > size)
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outOfBounds(tok->tokAt(4), "snprintf size");
}
// cin..
if (varid > 0 && Token::Match(tok, "cin >> %varid% ;", varid))
{
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bufferOverrun(tok);
}
// Function call..
// It's not interesting to check what happens when the whole struct is
// sent as the parameter, that is checked separately anyway.
if (Token::Match(tok, "%var% ("))
{
// Don't make recursive checking..
if (std::find(_callStack.begin(), _callStack.end(), tok) != _callStack.end())
continue;
// Only perform this checking if showAll setting is enabled..
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if (!_settings->_showAll)
continue;
unsigned int parlevel = 0, par = 0;
for (const Token *tok2 = tok; tok2; tok2 = tok2->next())
{
if (tok2->str() == "(")
{
++parlevel;
}
else if (tok2->str() == ")")
{
--parlevel;
if (parlevel < 1)
{
par = 0;
break;
}
}
else if (parlevel == 1 && (tok2->str() == ","))
{
++par;
}
if (parlevel == 1 && Token::Match(tok2, std::string("[(,] " + varnames + " [,)]").c_str()))
{
++par;
break;
}
}
if (par == 0)
continue;
// Find function..
const Token *ftok = _tokenizer->GetFunctionTokenByName(tok->str().c_str());
if (!ftok)
continue;
// Parse head of function..
ftok = ftok->tokAt(2);
parlevel = 1;
while (ftok && parlevel == 1 && par >= 1)
{
if (ftok->str() == "(")
++parlevel;
else if (ftok->str() == ")")
--parlevel;
else if (ftok->str() == ",")
--par;
else if (par == 1 && parlevel == 1 && Token::Match(ftok, "%var% [,)]"))
{
// Parameter name..
const char *parname[2];
parname[0] = ftok->str().c_str();
parname[1] = 0;
// Goto function body..
while (ftok && (ftok->str() != "{"))
ftok = ftok->next();
ftok = ftok ? ftok->next() : 0;
// Check variable usage in the function..
_callStack.push_back(tok);
CheckBufferOverrun_CheckScope(ftok, parname, size, total_size, 0);
_callStack.pop_back();
// break out..
break;
}
ftok = ftok->next();
}
}
}
}
//---------------------------------------------------------------------------
// Checking local variables in a scope
//---------------------------------------------------------------------------
void CheckBufferOverrunClass::CheckBufferOverrun_GlobalAndLocalVariable()
{
int indentlevel = 0;
for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next())
{
if (tok->str() == "{")
++indentlevel;
else if (tok->str() == "}")
--indentlevel;
const char *varname[2] = {0};
unsigned int size = 0;
const char *type = 0;
unsigned int varid = 0;
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;
if (Token::Match(tok, "%type% *| %var% [ %num% ] [;=]"))
{
unsigned int varpos = 1;
if (tok->next()->str() == "*")
++varpos;
varname[0] = tok->strAt(varpos);
size = std::strtoul(tok->strAt(varpos + 2), NULL, 10);
type = tok->strAt(varpos - 1);
varid = tok->tokAt(varpos)->varId();
nextTok = varpos + 5;
}
else if (indentlevel > 0 && Token::Match(tok, "[*;{}] %var% = new %type% [ %num% ]"))
{
varname[0] = tok->strAt(1);
size = std::strtoul(tok->strAt(6), NULL, 10);
type = tok->strAt(4);
varid = tok->tokAt(1)->varId();
nextTok = 8;
}
else if (indentlevel > 0 && Token::Match(tok, "[*;{}] %var% = malloc ( %num% ) ;"))
{
varname[0] = tok->strAt(1);
size = std::strtoul(tok->strAt(5), NULL, 10);
type = "char";
varid = tok->tokAt(1)->varId();
nextTok = 7;
}
else
{
continue;
}
int total_size = size * ((*type == '*') ? 4 : _tokenizer->SizeOfType(type));
if (total_size == 0)
continue;
// The callstack is empty
_callStack.clear();
CheckBufferOverrun_CheckScope(tok->tokAt(nextTok), varname, size, total_size, varid);
}
}
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// Checking member variables of structs..
//---------------------------------------------------------------------------
void CheckBufferOverrunClass::CheckBufferOverrun_StructVariable()
{
const char declstruct[] = "struct|class %var% {";
for (const Token *tok = Token::findmatch(_tokenizer->tokens(), declstruct);
tok; tok = Token::findmatch(tok->next(), declstruct))
{
const std::string &structname = tok->next()->str();
// Found a struct declaration. Search for arrays..
for (const Token *tok2 = tok->tokAt(2); tok2; tok2 = tok2->next())
{
if (tok2->str() == "}")
break;
int ivar = 0;
if (Token::Match(tok2->next(), "%type% %var% [ %num% ] ;"))
ivar = 2;
else if (Token::Match(tok2->next(), "%type% %type% %var% [ %num% ] ;"))
ivar = 3;
else if (Token::Match(tok2->next(), "%type% * %var% [ %num% ] ;"))
ivar = 3;
else if (Token::Match(tok2->next(), "%type% %type% * %var% [ %num% ] ;"))
ivar = 4;
else
continue;
const char *varname[3] = {0, 0, 0};
varname[1] = tok2->strAt(ivar);
int arrsize = std::atoi(tok2->strAt(ivar + 2));
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int total_size = arrsize * _tokenizer->SizeOfType(tok2->strAt(1));
if (total_size == 0)
continue;
// Class member variable => Check functions
if (tok->str() == "class")
{
std::string func_pattern(structname + " :: %var% (");
const Token *tok3 = Token::findmatch(_tokenizer->tokens(), func_pattern.c_str());
while (tok3)
{
for (const Token *tok4 = tok3; tok4; tok4 = tok4->next())
{
if (Token::Match(tok4, "[;{}]"))
break;
if (Token::simpleMatch(tok4, ") {"))
{
const char *names[2] = {varname[1], 0};
CheckBufferOverrun_CheckScope(tok4->tokAt(2), names, arrsize, total_size, 0);
break;
}
}
tok3 = Token::findmatch(tok3->next(), func_pattern.c_str());
}
}
for (const Token *tok3 = _tokenizer->tokens(); tok3; tok3 = tok3->next())
{
if (tok3->str() != structname)
continue;
// Declare variable: Fred fred1;
if (Token::Match(tok3->next(), "%var% ;"))
varname[0] = tok3->strAt(1);
// Declare pointer: Fred *fred1
else if (Token::Match(tok3->next(), "* %var% [,);=]"))
varname[0] = tok3->strAt(2);
else
continue;
// Goto end of statement.
const Token *CheckTok = NULL;
while (tok3)
{
// 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..
CheckBufferOverrun_CheckScope(CheckTok, varname, arrsize, total_size, 0);
}
}
}
}
//---------------------------------------------------------------------------
void CheckBufferOverrunClass::bufferOverrun()
{
CheckBufferOverrun_GlobalAndLocalVariable();
CheckBufferOverrun_StructVariable();
}
//---------------------------------------------------------------------------