C bufferoverflow question. can anyone solve it?

Consider the following C program:

Code:

void func(char * str)
{
char buff[16];
strcpy(buff,str);
}
void main(int argc, char * argv[])
{
int check = 1;
func(argv);
if(check == 1)
{
printf(“check should be 1 (%d)\n”,check);
} else
{
Printf(“check should not be 1 (%d)\n”,check);
}
}

Q1. Mount buffer overflow attack on the given program and corrupt the variable “check” with the value 25.

After the buffer overflow attack the output of the program should be the following:

check should not be 1 (25)

Q2. Mount buffer overflow attack on the given program and bypass the “if” condition.

After the buffer overflow attack the output of the program should be the following:
check should not be 1 (1)

Q3. Increase the size of the buffer “buff” to as much as you want. Mount a buffer overflow attack and make the program execute a shell (“/bin/bash”).

Hint: why wouldn't this be vulnerable to a buffer overflow?

Code:

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#define CONSTANT 2

int main( int argc, char** argv )
{
	int unused = CONSTANT;
	char buffer[ CONSTANT ];
	if( argc != 2 )
	{
		printf( "Overflow This!\n" );
		printf( "Usage: %s <text>\n", *argv );
		return EXIT_FAILURE;
	}
	strncpy( buffer, argv[ 1 ], sizeof( buffer ) );
	buffer[ sizeof( buffer ) - 1 ] = 0; 
	printf( "Unused = %d, Buffer: '%s'\n", unused, buffer );	
	return EXIT_SUCCESS;
}

If you can answer that, then you can answer the original questions, I think.

Originally Posted by asdfgh

Consider the following C program:

Code:

void func(char * str)
{
char buff[16];
strcpy(buff,str);
}
void main(int argc, char * argv[])
{
int check = 1;
func(argv);
if(check == 1)
{
printf(“check should be 1 (%d)\n”,check);
} else
{
Printf(“check should not be 1 (%d)\n”,check);
}
}

Q1. Mount buffer overflow attack on the given program and corrupt the variable “check” with the value 25.

After the buffer overflow attack the output of the program should be the following:

check should not be 1 (25)

Q2. Mount buffer overflow attack on the given program and bypass the “if” condition.

After the buffer overflow attack the output of the program should be the following:
check should not be 1 (1)

Q3. Increase the size of the buffer “buff” to as much as you want. Mount a buffer overflow attack and make the program execute a shell (“/bin/bash”).

Are you sure that your code isn't like this instead: func(argv[1]); ?