Question

A buffer overflow always results in vulnerable code being executed with root level privileges. True False

Answer 1

For answering this question lets first know what buffer overflow is,

A buffer is a region of memory with a certain boundary . for eg . an array declaration of 50 integers , or character array declaration that can hold 10 characters. So a buffer have associated boundary with a minimum and maximum value.

If the code is vulnerable and is not properly written (overflow conditions are not handled properly), then attacker can actually exploit the buffer usage by writing data past the left or right boundries . Lets say a character of string is for password is initialized as follows

char password[10];

Now an attacker can try to insert following instuction

password[10] ='a';

Now if array bounds are not properly handled , then this may cause the system to crash.

lets consider another situation by following code: -

char buff[10];

int flag = 0;

gets(buff)

if(strcmp(buff,"password")) {

WRONg password

} else {

flag =1;

password correct

}

if(flag) {

GRANT root access

}

gets() function does not check arraybounds . So lets say attacker has given password as "qwertyuiopasd". As password is more then size of buff and it is not handled, compiler will ignore it.

Though Wrong Password will be there, but because of bufferoverflow it can overwrite the value of flag making it non zero and can get the rool level access.

So its not like that everytime, attacker can get the root level access. It totally depends upon how intelligent an attacker is and how vulnerable the code is. Sometimes buffer overflow leads to system crash or make system highly unstable. So Ans is FALSE.