Thread: Stack Smashing error

Code:

int Formulate_StaticURL(char *finalstring,char *inputstring,int len)
{
	int i=0;
	char *fileextension = inputstring+len-1,fileextn[10]; 
		
	memset(fileextn,'\0',10);	
	printf("lenbfr:%d\n",len);	
	while(len > 0)
	{
		while((*fileextension!='/')&& ((len--) >0))
		{
			fileextn[i++] = *fileextension--;
			//printf("len:%d\n",len);
		}
		
		if((len <= 0)||( i==0 ))
		{
	         	printf("mylen:%d\n",len);
		        finalstring = NULL;
			break;
		}
		else
		{
			strncpy(finalstring,inputstring,len);
			finalstring += len;
			strcpy(finalstring,"something/something.");
			finalstring += strlen("something/something.");
			strcpy(finalstring,fileextn);
			break;
		}
		
	}
			printf("mylen2:%d\n",len);
	return 1;
}
//************************************************************//
// Main Program Starts here
//************************************************************//
int main()
{
	//char *StaticCfg = "192.168.5.59/mydirectoryname/php";
	char *StaticCfg = "192.168.5.59mydirectorynamehp";
	char *OutpuCfg =NULL,ch;
	OutpuCfg =(char *)malloc(URL_SZ);	
	memset(OutpuCfg,'0',URL_SZ);
	printf("My inoput :%s\n",StaticCfg);
	if(OutpuCfg != NULL)
		Formulate_StaticURL(OutpuCfg,StaticCfg,strlen(StaticCfg));
	if(OutpuCfg!=NULL)
	printf("My output:%s\n",OutpuCfg);
	//getch();
	//scanf("%c",&ch);
	//system("PAUSE");
	return 0;
}

What mistake am i doing in the above code to get a stack smashing error?

Thanks in advance

In the future, please copy-paste your code as plain text so that the forum's line numbering and syntax highlighting scripts can do their jobs.

Code:

fileextn[10];
...
while((*fileextension!='/')&& ((len--) >0))
{
    fileextn[i++] = *fileextension--;
    //printf("len:%d\n",len);
}

fileextn can hold a string of length 9 (remember 1 for the null terminator). Your while loop pays no mind to that length limitation, so in this case, where inputstring has no '/' character, and is longer than 9 characters, you copy past the end of fileextn, and smash the stack.

Note: I have no idea what this code is trying to accomplish, but I suspect your Formulate_StaticURL function has other bugs in it as well.

Ah!!! i didnt see the limit 10......Thanks for the quick reply.....I will not paste the plain txt nxt time.....

Originally Posted by anduril462

Note: I have no idea what this code is trying to accomplish, but I suspect your Formulate_StaticURL function has other bugs in it as well.

Its just replaces :

For Input :192.168.5.59/mydirectoryname/php

with
Output :192.168.5.59/mydirectoryname/something/something.php

Please let me know the other bugs as well