09-08-2008
How to block or ignore signals from certain processes?
We know that a process can block certain signals by call sigprocmask(), but sometimes we may want to block signals from certain processes for safety concerning.
For example, a system may have a process management daemon, and it will response to certain signals from certain processes managed by it. A process in this system may have certain request by sending certain signals to the process manager, in this case, if the process manager just response according to the received signal value without checking the signal sender, then other hacker processes may disguise to attack the system. Therefore, it is critical to block signals from other processes that the process manager does not recognize.
Of course, we can check the pid of signal senders in the signal handler, but it may seem awkard if there are dozens of processes monitored by the process manager.
Is there any neat method to block or ignore signals from certain processes ?
Thank you in advance !
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KILL(2) System Calls Manual KILL(2)
NAME
kill - send signal to a process
SYNOPSIS
kill(pid, sig);
DESCRIPTION
Kill sends the signal sig to the process specified by the process number in r0. See signal(2) for a list of signals.
The sending and receiving processes must have the same effective user ID, otherwise this call is restricted to the super-user.
If the process number is 0, the signal is sent to all other processes in the sender's process group; see tty(4).
If the process number is -1, and the user is the super-user, the signal is broadcast universally except to processes 0 and 1, the scheduler
and initialization processes, see init(8).
Processes may send signals to themselves.
SEE ALSO
signal(2), kill(1)
DIAGNOSTICS
Zero is returned if the process is killed; -1 is returned if the process does not have the same effective user ID and the user is not
super-user, or if the process does not exist.
ASSEMBLER
(kill = 37.)
(process number in r0)
sys kill; sig
KILL(2)