a) the program has to actively run its check while being ptraced to notice. If you attach to the program (which pauses it), inject your code, run your code, and then detach, the program's own code will not notice it's being ptraced, no?
b) if you want to run the program's own code while being ptraced, can't you just stop on the ptrace syscall and lie about its result? I think `strace -e inject=ptrace:errno=0` will avoid the program in that wiki page from realizing it's being traced. (You can use seccomp-bpf for this if you don't want to take the performance overhead of stopping on every syscall.)
Depends on if all threads were put into a paused state. Also, the program that's being debugged might have spawned some additional processes that will be checking if the parent is being ptraced.
Replace "self" with the PID you want to check if it is being traced:
$ cat /proc/self/status | grep Tracer
TracerPid: 0As such, I never truly understood the semantics behind PTRACE_TRACEME, and I'm not sure what bad things will happen if you use that when the parent isn't expecting to ptrace the child.
The problem with PTRACE_TRACEME is that if you do it to yourself and recieve a signal, you're put into ptrace stop there's and there's no way out of it unless the parent knows how to get you out of it (using ptrace, of course). Sending signals will not work, even SIGKILL; somewhat humorously, on iOS, if you attempt to do the equivalent (using the similar PT_TRACE_ME) and oops yourself, the entire system will slowly grind to a halt as it tries to (at least, I think…) SIGKILL your process for a variety of reasons and fails, at some point locking up waiting for process termination.
It’s a shot in the dark, but I’d guess this is designed to work with programs that neuter themselves or commit suicide if you ptrace them, as is common for mildly sophisticated malware or (less often) CTF challenges.