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If the process is already being traced, just resume it and clear flags.

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This makes it possible to run sudo in ptrace intercept mode from within
a shell (or other process) that is already being traced by sudo.
This commit is contained in:
Todd C. Miller
2022-05-03 13:34:40 -06:00
parent cc52ab770c
commit e84fdd99fd
4 changed files with 46 additions and 20 deletions
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41
src/exec_ptrace.c
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@@ -611,27 +611,43 @@ set_exec_filter(void)
/*
* Seize control of the specified child process which must be in
* ptrace wait. Returns true on success and false on failure.
* ptrace wait. Returns true on success, false if child is already
* being traced and -1 on error.
*/
bool
int
exec_ptrace_seize(pid_t child)
{
const long ptrace_opts = PTRACE_O_TRACESECCOMP|PTRACE_O_TRACECLONE|
PTRACE_O_TRACEFORK|PTRACE_O_TRACEVFORK;
int ret = -1;
int status;
debug_decl(exec_ptrace_seize, SUDO_DEBUG_UTIL);
/* Seize control of the child process. */
if (ptrace(PTRACE_SEIZE, child, NULL, ptrace_opts) == -1) {
sudo_warn("ptrace(PTRACE_SEIZE, %d, NULL, 0x%lx)", (int)child,
ptrace_opts);
debug_return_bool(false);
/*
* If the process is already being traced, we will get EPERM.
* We don't treat that as a fatal error since we want it to be
* possible to run sudo inside a sudo shell with intercept enabled.
*/
if (errno != EPERM) {
sudo_warn("ptrace(PTRACE_SEIZE, %d, NULL, 0x%lx)", (int)child,
ptrace_opts);
goto done;
}
sudo_debug_printf(SUDO_DEBUG_WARN,
"%s: unable to trace process %d, already being traced?",
__func__, (int)child);
ret = false;
}
/* The child is suspended waiting for SIGUSR1, wake it up. */
if (kill(child, SIGUSR1) == -1) {
sudo_warn("kill(%d, SIGUSR1)", child);
debug_return_bool(false);
goto done;
}
if (!ret)
goto done;
/* Wait for the child to enter trace stop and continue it. */
for (;;) {
@@ -640,18 +656,21 @@ exec_ptrace_seize(pid_t child)
if (errno == EINTR)
continue;
sudo_warn(U_("%s: %s"), __func__, "waitpid");
debug_return_bool(false);
goto done;
}
if (!WIFSTOPPED(status)) {
sudo_warnx(U_("process %d exited unexpectedly"), (int)child);
debug_return_bool(false);
goto done;
}
if (ptrace(PTRACE_CONT, child, NULL, (long)SIGUSR1) == -1) {
sudo_warn("ptrace(PTRACE_CONT, %d, NULL, SIGUSR1)", (int)child);
debug_return_bool(false);
goto done;
}
debug_return_bool(true);
ret = true;
done:
debug_return_int(ret);
}
/*
@@ -921,7 +940,7 @@ exec_ptrace_handled(pid_t pid, int status, void *intercept)
}
/* STUB */
bool
int
exec_ptrace_seize(pid_t child)
{
return true;