Minix Security

To Design and implement the set- Random UID mechanism.

Lab Report .

Step 1.

The unused sticky bit in the permission field of the I-node data structure (defined in /usr/src/fs/inode.h) is used. This sticky bit is disabled in the usr/include/minix/const.h

To enable set random uid mechanism :

We have to enable the sticky bit , say, for a file

chmod +t filename

I made a file fd.c in which I was editing another text file named tested txt.

Both fd and tested.txt are owned by a normal user t2.

chmod +t fd

Following is the code for the program, with permissions 765 which can write malicious data into a text file tested.txt

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fd.c

#include

#include

#include

#include

#include

#include

main(void)

{

int fd;

setuid(getuid());

/*setgid(getgid());*/

fd=open(ÐŽ§/cs/tested.txtЎЁ, O_RDWR | O_APPEND);

if (fork())

{

close(fd);

exit(0);

}

else

{

write (fd, ÐŽ§n yes I can write