Re: Symlinks and Cryogenic Sleep

[jdc () FIAWOL ORG (John Cochran)]

der Mouse <mouse () RODENTS MONTREAL QC CA> wrote:

> > [symlink-paranoia code]
>
> > However, consider an average setuid root application, [...].  When
> > the application reaches the critical section of code between the
> > lstat and the open, you stop it by sending it a SIGSTOP.
>
> If you can send it a SIGSTOP, either you're running as root (in which
> case you don't *need* to play with symlink races), the application is
> running as you (in which case breaking it buys you nothing), or signal
> delivery is critically broken.
>
> In fact, I suspect that any process you can SIGSTOP, you can attach to
> with ptrace and do whatever you want without need for subtrefuge.

Script started on Tue Jan  4 15:40:55 2000
bash-2.02$ ls -l ./slow
-rwsr-xr-x  1 root  nogroup  3170 Jan  4 15:36 ./slow
bash-2.02$ whoami
jdc
bash-2.02$ ./slow &
[1] 68416
bash-2.02$ ps -up 68416
USER   PID %CPU %MEM   VSZ  RSS  TT  STAT STARTED      TIME COMMAND
root 68416  0.0  0.2   752  248  p1  S     3:41PM   0:00.01 ./slow
bash-2.02$ kill -STOP 68416

[1]+  Stopped                 ./slow
bash-2.02$ kill -CONT 68416
bash-2.02$ ps -up 68416
USER   PID %CPU %MEM   VSZ  RSS  TT  STAT STARTED      TIME COMMAND
root 68416  0.0  0.2   752  248  p1  S     3:41PM   0:00.01 ./slow
bash-2.02$ kill -9 68416
[1]+  Killed                  ./slow
bash-2.02$ exit
exit

Script done on Tue Jan  4 15:42:06 2000