cppcheck/CheckBufferOverrun.cpp

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//---------------------------------------------------------------------------
#include "CheckBufferOverrun.h"
#include "tokenize.h"
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#include "CommonCheck.h"
#include <sstream>
#include <stdlib.h> // <- strtoul
//---------------------------------------------------------------------------
TOKEN *findfunction(TOKEN *tok)
{
int indentlevel = 0, parlevel = 0;
for (; tok; tok = tok->next)
{
if (tok->str[0] == '{')
indentlevel++;
else if (tok->str[0] == '}')
indentlevel--;
else if (tok->str[0] == '(')
parlevel++;
else if (tok->str[0] == ')')
parlevel--;
if (!tok->next)
break;
if (indentlevel==0 && parlevel==0 && IsName(tok->str) && tok->next->str[0]=='(')
{
for (TOKEN *tok2 = tok->next; tok2; tok2 = tok2->next)
{
if (tok2->str[0] == ')')
{
if (tok2->next->str[0] == '{')
return tok;
break;
}
}
}
}
return 0;
}
//---------------------------------------------------------------------------
// Writing dynamic data in buffer without bounds checking
//---------------------------------------------------------------------------
extern bool ShowAll;
static void _DynamicDataCheck(TOKEN *ftok, TOKEN *tok)
{
const char *var2 = tok->str;
bool decl = false;
unsigned int Var2Count = 0;
for ( TOKEN *tok2 = ftok; tok2; tok2 = tok2->next )
{
if (tok2 == tok)
break;
if (match(tok2,"char * var"))
{
decl |= (strcmp(getstr(tok2,2),var2)==0);
tok2 = gettok(tok2,3);
if ( strcmp(tok2->str, "=") == 0 )
{
Var2Count++;
break;
}
}
if (match(tok2,"char var [ ]"))
{
decl |= (strcmp(getstr(tok2,1),var2)==0);
tok2 = gettok(tok2,3);
}
// If ShowAll, only strlen(var2) counts
if ( ShowAll )
{
if (match(tok2,"strlen ( var )") &&
strcmp(getstr(tok2,2),var2)==0)
{
Var2Count++;
break;
}
}
// If not ShowAll, all usage of "var2" counts
else
{
if (strcmp(tok2->str,var2)==0)
{
Var2Count++;
break;
}
}
}
// The size of Var2 isn't checked, is it?
if (decl && Var2Count == 0)
{
std::ostringstream ostr;
ostr << FileLine(tok) << ": A string with unknown length is copied to buffer.";
ReportErr(ostr.str());
}
}
static void _DynamicData()
{
for (TOKEN *ftok = findfunction(tokens); ftok; ftok = findfunction(ftok->next))
{
int indentlevel = 0;
for (TOKEN *tok = ftok; tok; tok = tok->next)
{
if (tok->str[0] == '{')
indentlevel++;
else if (tok->str[0] == '}')
{
indentlevel--;
if (indentlevel <= 0)
break;
}
if (match(tok,"strcpy ( var , var )") ||
match(tok,"strcat ( var , var )") )
{
_DynamicDataCheck(ftok,gettok(tok,4));
}
if (match(tok,"sprintf ( var"))
{
for ( TOKEN *tok2 = gettok(tok,3); tok2; tok2 = tok2->next )
{
if (tok2->str[0] == ')')
break;
if (match(tok2,", var ,") || match(tok2,", var )"))
{
_DynamicDataCheck(ftok,tok2->next);
}
}
}
}
}
}
//---------------------------------------------------------------------------
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//---------------------------------------------------------------------------
// Buffer overrun..
//---------------------------------------------------------------------------
void CheckBufferOverrun()
{
_DynamicData();
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int indentlevel = 0;
for (TOKEN *tok = tokens; tok; tok = tok->next)
{
if (tok->str[0]=='{')
indentlevel++;
else if (tok->str[0]=='}')
indentlevel--;
else if (indentlevel > 0)
{
// Declaring array..
if (match(tok, "type var [ num ] ;"))
{
const char *varname = getstr(tok,1);
unsigned int size = strtoul(getstr(tok,3), NULL, 10);
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int total_size = size * SizeOfType(tok->str);
if (total_size == 0)
continue;
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int _indentlevel = indentlevel;
for (TOKEN *tok2 = gettok(tok,5); tok2; tok2 = tok2->next)
{
if (tok2->str[0]=='{')
{
_indentlevel++;
}
else if (tok2->str[0]=='}')
{
_indentlevel--;
if (_indentlevel < indentlevel)
break;
}
else
{
// Array index..
if (strcmp(tok2->str,varname)==0 &&
strcmp(getstr(tok2,1),"[")==0 &&
IsNumber(getstr(tok2,2)) &&
strcmp(getstr(tok2,3),"]")==0 )
{
const char *str = getstr(tok2, 2);
if (strtoul(str, NULL, 10) >= size)
{
std::ostringstream ostr;
ostr << FileLine(tok2) << ": Array index out of bounds";
ReportErr(ostr.str());
}
}
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// memset, memcmp, memcpy, strncpy, fgets..
if (strcmp(tok2->str,"memset")==0 ||
strcmp(tok2->str,"memcpy")==0 ||
strcmp(tok2->str,"memmove")==0 ||
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strcmp(tok2->str,"memcmp")==0 ||
strcmp(tok2->str,"strncpy")==0 ||
strcmp(tok2->str,"fgets")==0 )
{
if (match(tok2->next,"( var , num , num )") ||
match(tok2->next,"( var , var , num )") )
{
const char *var1 = getstr(tok2, 2);
const char *var2 = getstr(tok2, 4);
const char *num = getstr(tok2, 6);
if ( atoi(num)>total_size &&
(strcmp(var1,varname)==0 ||
strcmp(var2,varname)==0 ) )
{
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std::ostringstream ostr;
ostr << FileLine(tok2) << ": Buffer overrun";
ReportErr(ostr.str());
}
}
}
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// Loop..
const char *strindex = 0;
int value = 0;
if ( match(tok2, "for ( var = 0 ;") )
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{
if (match(tok2,"for ( var = 0 ; var < num ; var + + )"))
{
strindex = getstr(tok2,2);
value = atoi(getstr(tok2,8));
}
else if (match(tok2,"for ( var = 0 ; var <= num ; var + + )"))
{
strindex = getstr(tok2,2);
value = 1 + atoi(getstr(tok2,8));
}
else if (match(tok2,"for ( var = 0 ; var < num ; + + var )"))
{
strindex = getstr(tok2,2);
value = atoi(getstr(tok2,8));
}
else if (match(tok2,"for ( var = 0 ; var <= num ; + + var )"))
{
strindex = getstr(tok2,2);
value = 1 + atoi(getstr(tok2,8));
}
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}
if (strindex && value>(int)size)
{
TOKEN *tok3 = tok2;
while (tok3 && strcmp(tok3->str,")"))
tok3 = tok3->next;
if (!tok3)
break;
tok3 = tok3->next;
if (tok3->str[0] == '{')
tok3 = tok3->next;
while (tok3 && !strchr(";}",tok3->str[0]))
{
if (strcmp(tok3->str,varname)==0 &&
strcmp(getstr(tok3,1),"[")==0 &&
strcmp(getstr(tok3,2),strindex)==0 &&
strcmp(getstr(tok3,3),"]")==0 )
{
std::ostringstream ostr;
ostr << FileLine(tok3) << ": Buffer overrun";
ReportErr(ostr.str());
break;
}
tok3 = tok3->next;
}
}
// Writing data into array..
if (match(tok2,"strcpy ( var , "))
{
int len = 0;
if (strcmp(getstr(tok2, 2), varname) == 0)
{
const char *str = getstr(tok2, 4);
if (str[0] == '\"')
{
while (*str)
{
if (*str=='\\')
str++;
str++;
len++;
}
}
}
if (len > 2 && len >= (int)size + 2)
{
std::ostringstream ostr;
ostr << FileLine(tok2) << ": Buffer overrun";
ReportErr(ostr.str());
}
}
}
}
}
}
}
}
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// Dangerous functions
//---------------------------------------------------------------------------
void WarningDangerousFunctions()
{
for (TOKEN *tok = tokens; tok; tok = tok->next)
{
if (match(tok, "gets ("))
{
std::ostringstream ostr;
ostr << FileLine(tok) << ": Found 'gets'. You should use 'fgets' instead";
ReportErr(ostr.str());
}
else if (match(tok, "scanf (") && strcmp(getstr(tok,2),"\"%s\"") == 0)
{
std::ostringstream ostr;
ostr << FileLine(tok) << ": Found 'scanf'. You should use 'fgets' instead";
ReportErr(ostr.str());
}
}
}
//---------------------------------------------------------------------------